CLINICAL IMMUNOLOGY MED STUDENT MCQ & SAQ Table Of Contents: What’s included: A comprehensive set of university-level multiple-choice (MCQ) and shortanswer (SAQ) exam questions covering everything to do with the Immune System. All answer keys are provided directly after each quiz so that you can revise and reassess as you go, helping you learn better and improve retention. Quizzes in this booklet: • • • • • • • • • • • • • • • • • • •
OVERVIEW OF THE IMMUNE SYSTEM - INNATE IMMUNITY ADAPTIVE IMMUNITY - HUMORAL AND CELL-MEDIATED IMMUNITY ANTIGENS AND ANTIBODIES ANTIGEN RECEPTORS, PAMPS, AND TLRS MAJOR HISTOCOMPATIBILITY COMPLEXES CELLS OF THE IMMUNE SYSTEM - LYMPHOID CELLS, ORIGINS, AND DEVELOPMENT TOLERANCE IN THE IMMUNE SYSTEM FUNCTIONAL ANATOMY OF SECONDARY LYMPHOID ORGANS REJECTION IMMUNITY INFLAMMATION HYPERSENSITIVITY AND ALLERGY IMMUNODEFICIENCY IMMUNITY AGAINST INFECTIOUS ORGANISMS AND EVASION OF THE IMMUNE RESPONSE VIRUSES AND IMMUNITY BACTERIA AND IMMUNITY PARASITES AND IMMUNITY IMMUNE EVASION MECHANISMS AUTOIMMUNITY COMMON AUTOIMMUNE CONDITIONS
MCQ Quiz: Overview of the Immune System - Innate Immunity 1. Which of the following is NOT considered a physical barrier of the innate immune system? A. Skin B. Mucous membranes C. Macrophages D. Saliva 2. What is the primary function of macrophages in the innate immune system? A. Producing antibodies B. Phagocytosis of pathogens C. Producing histamine D. Activating T cells 3. Which of the following cells is primarily responsible for killing virus-infected cells? A. B cells B. Neutrophils C. Natural killer (NK) cells D. Eosinophils 4. Antigen-presenting cells (APCs) include which of the following? A. Neutrophils B. Dendritic cells C. B cells D. Both B and C 5. Which of the following is an essential feature of inflammation? A. Vasodilation B. Vasoconstriction C. Decreased vascular permeability D. Inhibition of leukocyte migration 6. The complement system is a group of proteins that primarily function to: A. Produce antibodies B. Engulf and digest pathogens C. Enhance the ability of antibodies and phagocytic cells to clear pathogens D. Stimulate the production of cytokines 7. Which of the following is a granulocyte involved in fighting parasitic infections? A. Eosinophils B. Basophils C. Neutrophils D. Lymphocytes 8. Fever is induced by the release of which substance? A. Histamine B. Interleukin-1 C. Prostaglandins D. Cytotoxic T cells
9. What is the primary function of mast cells in the immune system? A. Phagocytosis B. Release of histamine C. Killing virus-infected cells D. Presenting antigens 10. Which of the following cells is a phagocyte? A. Eosinophil B. B cell C. Macrophage D. Natural killer cell 11. What is the primary role of neutrophils in the innate immune system? A. Producing antibodies B. Phagocytosis and release of antimicrobial substances C. Inducing fever D. Killing virus-infected cells 12. Which of the following is NOT a function of the complement system? A. Opsonization B. Membrane attack complex (MAC) formation C. Antibody production D. Recruitment of inflammatory cells
Answer Key: 1. C 2. B 3. C 4. D 5. A 6. C 7. A 8. B 9. B 10. C 11. B 12. C
SAQ Quiz: Overview of the Immune System - Innate Immunity 1. Briefly explain the process of phagocytosis in the innate immune system.
2. Describe the role of natural killer (NK) cells in the immune response.
3. How do dendritic cells function in the immune system, and why are they considered antigen-presenting cells (APCs)?
4. Explain the steps involved in the process of inflammation.
5. How does the complement system contribute to the immune response against pathogens?
6. Briefly describe the role of mast cells in allergic reactions.
7. What is opsonization and how does it contribute to the immune response?
Model Answers: 1. Phagocytosis is a process by which cells, such as macrophages and neutrophils, engulf and destroy pathogens. The process begins with pathogen recognition, followed by attachment to the phagocyte's cell membrane. The membrane then surrounds the pathogen, forming a phagosome. The phagosome fuses with a lysosome, creating a phagolysosome, where the pathogen is digested by enzymes and destroyed. 2. Natural killer (NK) cells are lymphocytes that play a crucial role in the immune response against virus-infected cells and tumor cells. They recognize and bind to abnormal cells, then release cytotoxic granules containing perforin and granzymes, which cause the target cell to undergo apoptosis (cell death). 3. Dendritic cells function as antigen-presenting cells (APCs) in the immune system. They capture and process antigens, then migrate to lymphoid tissues where they present the processed antigen fragments on their cell surface using MHC II molecules. This presentation activates T cells, initiating the adaptive immune response. 4. Inflammation is a process that involves several steps: (1) tissue injury or infection triggers the release of chemical mediators, such as histamine and prostaglandins; (2) vasodilation occurs, increasing blood flow to the affected area; (3) increased vascular permeability allows plasma proteins and leukocytes to enter the site of injury or infection; (4) chemotaxis attracts immune cells, such as neutrophils and macrophages, to the site; (5) phagocytes engulf and destroy pathogens and cellular debris. 5. The complement system contributes to the immune response by enhancing the ability of antibodies and phagocytic cells to clear pathogens. This occurs through processes such as opsonization, which enhances phagocytosis; the formation of the membrane attack complex (MAC), which leads to cell lysis; and the recruitment of inflammatory cells, which helps to eliminate pathogens. 6. Mast cells play a key role in allergic reactions by releasing histamine and other inflammatory mediators upon activation. This occurs when allergens bind to IgE antibodies on the surface of mast cells, leading to degranulation and the release of histamine, which causes vasodilation, increased vascular permeability, and smooth muscle contraction, resulting in the symptoms of an allergic reaction. 7. Opsonization is the process by which pathogens are coated with molecules, such as antibodies or complement proteins, that enhance their recognition and uptake by phagocytes. This process increases the efficiency of phagocytosis, allowing for more effective clearance of pathogens from the body.
MCQ Quiz: Adaptive Immunity - Humoral and Cell-Mediated Immunity 1. Which of the following cells are responsible for humoral immunity? A. B cells B. T cells C. Macrophages D. Neutrophils 2. What is the primary function of cytotoxic T cells (CD8+ T cells) in cell-mediated immunity? A. Producing antibodies B. Killing virus-infected cells C. Helping B cells produce antibodies D. Suppressing the immune response 3. Which of the following cells play a crucial role in both humoral and cell-mediated immunity? A. B cells B. Neutrophils C. Helper T cells (CD4+ T cells) D. Natural killer cells 4. What is the primary function of antibodies in the immune response? A. Phagocytosis B. Killing virus-infected cells C. Binding to antigens to neutralize or target pathogens for destruction D. Suppressing the immune response 5. Which of the following types of T cells is responsible for suppressing the immune response? A. Helper T cells (CD4+ T cells) B. Cytotoxic T cells (CD8+ T cells) C. Regulatory T cells D. Natural killer T cells 6. The three phases of adaptive immune responses are: A. Activation, effector, and memory B. Recognition, proliferation, and differentiation C. Priming, effector, and resolution D. Induction, elimination, and memory 7. What is the primary function of memory cells in the immune response? A. Producing antibodies B. Killing virus-infected cells C. Providing a rapid and enhanced response to subsequent exposures to the same antigen D. Suppressing the immune response
8. Which of the following cells presents antigens to helper T cells (CD4+ T cells)? A. Neutrophils B. B cells C. Macrophages D. All of the above 9. During the activation phase of the adaptive immune response, which of the following events occurs? A. Naïve T and B cells are stimulated to proliferate and differentiate B. Effector cells eliminate the pathogen C. Memory cells are formed D. The immune response is suppressed 10. The primary function of the effector phase in the adaptive immune response is to: A. Activate naïve T and B cells B. Eliminate the pathogen C. Form memory cells D. Suppress the immune response 11. In which phase of the adaptive immune response are memory cells formed? A. Activation B. Effector C. Memory D. Resolution 12. The process by which B cells produce antibodies with increased affinity for the antigen during an immune response is called: A. Clonal expansion B. Somatic hypermutation C. Class switching D. Affinity maturation
Answer Key: 1. A 2. B 3. C 4. C 5. C 6. A 7. C 8. D 9. A 10. B 11. C 12. D
SAQ Quiz: Adaptive Immunity - Humoral and Cell-Mediated Immunity 1. Explain the primary difference between humoral immunity and cell-mediated immunity.
2. Describe the role of helper T cells (CD4+ T cells) in the adaptive immune response.
3. How do cytotoxic T cells (CD8+ T cells) recognize and kill infected cells?
4. Explain the process of clonal expansion in the adaptive immune response.
5. Describe the role of regulatory T cells in the immune system.
6. What is the importance of class switching in B cell activation and antibody production?
7. How do memory cells contribute to a more rapid and effective immune response upon subsequent exposure to the same antigen?
Model Answers: 1. The primary difference between humoral immunity and cell-mediated immunity lies in their mechanisms of action. Humoral immunity is mediated by B cells that produce antibodies, which neutralize or target pathogens for destruction. Cell-mediated immunity, on the other hand, involves T cells, specifically cytotoxic T cells (CD8+ T cells), which directly kill infected cells or activate other immune cells. 2. Helper T cells (CD4+ T cells) play a crucial role in the adaptive immune response by activating other immune cells. They help B cells produce antibodies and differentiate into memory B cells, and they also stimulate cytotoxic T cells (CD8+ T cells) to become more efficient at killing infected cells. 3. Cytotoxic T cells (CD8+ T cells) recognize infected cells through the interaction of their T cell receptor (TCR) with the major histocompatibility complex class I (MHC I) molecule, which presents antigens on the surface of infected cells. Once the cytotoxic T cell binds to the infected cell, it releases cytotoxic granules containing perforin and granzymes, leading to apoptosis (cell death) of the infected cell. 4. Clonal expansion is the process by which activated T and B cells rapidly proliferate and differentiate into effector and memory cells upon encountering a specific antigen. This allows the immune system to generate a large number of immune cells specific to the pathogen, ensuring a more effective response. 5. Regulatory T cells play a role in maintaining immune tolerance and preventing autoimmune reactions by suppressing the immune response. They do this by inhibiting the activation and function of other immune cells, such as helper T cells and cytotoxic T cells, and by promoting the production of anti-inflammatory cytokines. 6. Class switching is the process by which B cells change the class of the antibody they produce while retaining antigen specificity. This allows the immune system to produce antibodies with different functions and effector mechanisms, ensuring a more effective and targeted response against the pathogen. 7. Memory cells contribute to a more rapid and effective immune response upon subsequent exposure to the same antigen by providing a faster and more robust response. When memory cells encounter the antigen again, they rapidly proliferate and differentiate into effector cells, producing a larger number of antibodies and effector T cells. This results in quicker pathogen elimination and a reduced likelihood of illness.
MCQ Quiz: Antigens and Antibodies 1. Which of the following best describes an antigen? A. A molecule that binds to a B cell receptor or T cell receptor B. A protein that recognizes and binds to a specific antigen C. A molecule that triggers an immune response D. Both A and C 2. What is an epitope? A. The portion of an antigen that is recognized and bound by an antibody B. The region of an antibody that binds to an antigen C. A protein that is produced by B cells in response to an antigen D. A protein that is produced by T cells in response to an antigen 3. Thymus-dependent antigens (TD antigens) are characterized by their ability to: A. Activate B cells without the help of T cells B. Activate B cells only with the help of T cells C. Trigger an immune response independently of B cells D. Bind directly to T cell receptors 4. Thymus-independent antigens (TI antigens) are characterized by their ability to: A. Activate B cells without the help of T cells B. Activate B cells only with the help of T cells C. Trigger an immune response independently of B cells D. Bind directly to T cell receptors 5. Which of the following is NOT a function of antibodies? A. Neutralization B. Opsonization C. Activation of complement D. Phagocytosis 6. Which region of an antibody molecule is responsible for binding to an antigen? A. Constant region B. Variable region C. Hinge region D. Fab region 7. What is the process by which B cells change the class of the antibody they produce? A. Somatic hypermutation B. Clonal expansion C. Isotype switching D. Affinity maturation 8. Which of the following is NOT one of the five main classes of immunoglobulins? A. IgA B. IgD C. IgE D. IgY
9. Which immunoglobulin class is the most abundant in the blood? A. IgA B. IgD C. IgG D. IgM 10. Which immunoglobulin class is primarily found in mucosal secretions? A. IgA B. IgD C. IgG D. IgM 11. What is the primary function of IgE antibodies? A. Neutralizing bacterial toxins B. Mediating allergic reactions C. Crossing the placenta to provide passive immunity to the fetus D. Participating in agglutination 12. Which immunoglobulin class is the first to be produced in response to an infection? A. IgA B. IgD C. IgG D. IgM
Answer Key: 1. D 2. A 3. B 4. A 5. D 6. B 7. C 8. D 9. C 10. A 11. B 12. D
SAQ Quiz: Antigens and Antibodies 1. Explain the difference between thymus-dependent (TD) and thymus-independent (TI) antigens.
2. Describe the general structure of an antibody.
3. Explain the concept of antigenic determinants and their importance in the immune response.
4. What are the primary functions of antibodies in the immune system?
5. How does somatic hypermutation contribute to the specificity of the adaptive immune response?
6. Briefly describe the roles of the five main immunoglobulin classes (IgA, IgD, IgE, IgG, and IgM) in the immune response.
7. Explain the importance of antibody-dependent cellular cytotoxicity (ADCC) in the immune response.
Model Answers: 1. Thymus-dependent (TD) antigens are antigens that require the help of T cells to activate B cells, leading to the production of antibodies. In contrast, thymusindependent (TI) antigens can activate B cells without the assistance of T cells, often through the direct cross-linking of B cell receptors, leading to an immune response. 2. The general structure of an antibody consists of four polypeptide chains: two identical heavy chains and two identical light chains. These chains are connected by disulfide bonds, forming a Y-shaped molecule. Each chain has a variable region (V) at the amino-terminal end, which is responsible for antigen recognition and binding, and a constant region (C) at the carboxy-terminal end, which determines the antibody's class and effector functions. 3. Antigenic determinants, also known as epitopes, are specific regions on an antigen that are recognized and bound by antibodies. These determinants play an important role in the immune response as they determine the specificity of the antibodyantigen interaction and are crucial for the activation of B cells and the production of specific antibodies. 4. The primary functions of antibodies in the immune system include neutralization (binding to and inactivating pathogens or toxins), opsonization (coating pathogens to enhance phagocytosis), activation of the complement system (triggering a cascade of events that lead to pathogen elimination), and agglutination (clumping together of pathogens to facilitate their clearance). 5. Somatic hypermutation is a process by which the variable regions of B cell receptor genes undergo rapid and random mutations during an immune response. This process generates a diverse pool of B cells with different antigen-binding specificities, allowing the immune system to select B cells that produce antibodies with higher affinity for the antigen, ultimately improving the effectiveness of the immune response. 6. The five main immunoglobulin classes have distinct roles in the immune response: IgA is primarily found in mucosal secretions and provides local defense against pathogens; IgD is involved in the activation and maturation of B cells; IgE is involved in allergic reactions and defense against parasites; IgG is the most abundant immunoglobulin in the blood and provides systemic immunity, crossing the placenta to provide passive immunity to the fetus; and IgM is the first immunoglobulin to be produced in response to an infection and is involved in early immune responses. 7. Antibody-dependent cellular cytotoxicity (ADCC) is a mechanism by which immune cells, such as natural killer (NK) cells, recognize and eliminate target cells coated with antibodies. The Fc receptor on the effector cell binds to the constant region (Fc) of the antibody, which is attached to the target cell. The effector cell then releases cytotoxic molecules, such as perforin and granzymes, which induce apoptosis in the target cell, contributing to the elimination of infected or abnormal cells.
MCQ Quiz: Antigen Receptors, PAMPs, and TLRs 1. Which of the following statements best describes the function of antigen receptors on B and T lymphocytes? A. Binding to specific antigens to initiate an immune response B. Producing antibodies C. Killing infected cells D. Suppressing the immune response 2. How is the diversity of antigen receptors on B and T cells generated? A. Through gene rearrangement during lymphocyte development B. By somatic hypermutation during an immune response C. Through the interaction with MHC molecules D. By isotype switching 3. B cell receptors (BCRs) are composed of which of the following components? A. Immunoglobulin (Ig) molecules and CD3 signaling complex B. T cell receptor (TCR) molecules and CD3 signaling complex C. Immunoglobulin (Ig) molecules and Igα/Igβ signaling complex D. T cell receptor (TCR) molecules and Igα/Igβ signaling complex 4. What is the primary function of T cell receptors (TCRs)? A. Binding to free antigens in the extracellular environment B. Binding to antigens presented on MHC molecules C. Producing antibodies D. Killing infected cells 5. Which of the following statements about PAMPs (pathogen-associated molecular patterns) is true? A. PAMPs are molecules produced by the host immune system B. PAMPs are molecules produced by pathogens that are recognized by the host immune system C. PAMPs are molecules that bind to T cell receptors D. PAMPs are molecules that bind to B cell receptors 6. Toll-like receptors (TLRs) are a class of proteins that play a role in: A. Antibody production B. Killing infected cells C. Recognizing PAMPs and initiating an innate immune response D. Binding to MHC molecules 7. Which of the following cells express Toll-like receptors (TLRs)? A. B cells only B. T cells only C. Dendritic cells, macrophages, and other innate immune cells D. All of the above
8. What is the primary function of the CD3 signaling complex in T cell receptors? A. Binding to antigens B. Transmitting signals to the interior of the cell upon antigen recognition C. Producing antibodies D. Killing infected cells 9. Which of the following statements about MHC molecules is true? A. MHC molecules are expressed only on antigen-presenting cells B. MHC molecules are responsible for presenting antigens to T cell receptors C. MHC molecules bind directly to B cell receptors D. MHC molecules are only expressed on B cells 10. Which type of MHC molecule presents antigens to CD4+ T cells? A. MHC class I B. MHC class II C. MHC class III D. MHC class IV 11. Which type of MHC molecule presents antigens to CD8+ T cells? A. MHC class I B. MHC class II C. MHC class III D. MHC class IV 12. In which cellular location do T cell receptors primarily encounter antigens? A. Extracellular environment B. Cell surface C. Endosomes D. Cytosol
Answer Key: 1. A 2. A 3. C 4. B 5. B 6. C 7. C 8. B 9. B 10. B 11. A 12. B
SAQ Quiz: Antigen Receptors, PAMPs, and TLRs 1. Explain the process by which diversity in B cell receptors (BCRs) is generated.
2. Describe the structure and function of T cell receptors (TCRs).
3. Explain the role of pathogen-associated molecular patterns (PAMPs) in the immune response.
4. Describe the structure and function of Toll-like receptors (TLRs) and their role in the immune response.
5. Compare and contrast the recognition of antigens by B cell receptors (BCRs) and T cell receptors (TCRs).
6. Explain the importance of MHC molecules in the presentation of antigens to T cells.
7. Describe the role of the CD3 signalling complex in T cell activation.
Model Answers: 1. Diversity in B cell receptors (BCRs) is generated during lymphocyte development through a process known as V(D)J recombination. This process involves the random rearrangement of gene segments encoding the variable regions of the immunoglobulin heavy and light chains, which form the antigen-binding site of the BCR. The junctions between the gene segments are further diversified by the addition or deletion of nucleotides, creating a diverse repertoire of BCRs with unique antigen-binding specificities. 2. T cell receptors (TCRs) are membrane-bound glycoproteins expressed on the surface of T cells. They are composed of two polypeptide chains, the α and β chains, which are connected by a disulfide bond. Each chain has a variable region that is responsible for antigen recognition and a constant region that anchors the TCR to the cell membrane. The primary function of TCRs is to recognize and bind to peptide antigens presented on MHC molecules, leading to T cell activation and the initiation of an adaptive immune response. 3. Pathogen-associated molecular patterns (PAMPs) are conserved molecular structures found on the surface of pathogens. They are recognized by pattern recognition receptors (PRRs) on host immune cells, such as dendritic cells and macrophages. The recognition of PAMPs by PRRs triggers an innate immune response, including the production of cytokines and chemokines, phagocytosis of pathogens, and the activation of the adaptive immune response. 4. Toll-like receptors (TLRs) are a family of transmembrane proteins that serve as pattern recognition receptors (PRRs) in the innate immune system. They recognize a wide range of PAMPs, such as bacterial lipopolysaccharides and viral nucleic acids. Upon binding to PAMPs, TLRs initiate signaling pathways that lead to the activation of immune cells and the production of pro-inflammatory cytokines, which help to eliminate the pathogen and initiate an adaptive immune response. 5. B cell receptors (BCRs) and T cell receptors (TCRs) both recognize antigens, but they do so in different ways. BCRs, which are membrane-bound immunoglobulin molecules, bind to free antigens in the extracellular environment. In contrast, TCRs recognize peptide antigens that are presented on the surface of antigen-presenting cells (APCs) in complex with MHC molecules. This difference in antigen recognition underlies the distinct functions of B and T cells in the adaptive immune response. 6. MHC molecules play a crucial role in the presentation of antigens to T cells, facilitating the initiation of an adaptive immune response. MHC molecules bind to peptide fragments derived from pathogens and display them on the cell surface for recognition by T cell receptors (TCRs). MHC class I molecules present endogenously derived antigens, such as those from intracellular pathogens, to CD8+ cytotoxic T cells. MHC class II molecules present exogenously derived antigens, such as those from extracellular pathogens, to CD4+ helper T cells. The interaction between TCRs and MHC-peptide complexes leads to T cell activation, allowing them to carry out their effector functions against the specific pathogen.
7. The CD3 signaling complex is a group of transmembrane proteins associated with the T cell receptor (TCR). It consists of CD3γ, CD3δ, CD3ε, and the ζ-chain (CD247) subunits. These subunits contain immunoreceptor tyrosine-based activation motifs (ITAMs) in their cytoplasmic tails. When the TCR recognizes and binds to an antigenMHC complex on an antigen-presenting cell, it triggers the phosphorylation of ITAMs within the CD3 signaling complex. This phosphorylation event recruits and activates downstream signaling molecules, such as ZAP-70 and LAT, which initiate a cascade of intracellular signaling events that ultimately lead to T cell activation, proliferation, and differentiation into effector T cells. The CD3 signaling complex is therefore essential for translating the recognition of antigen-MHC complexes by the TCR into the cellular activation necessary for an adaptive immune response.
MCQ Quiz: Major Histocompatibility Complexes 1. What is the primary function of major histocompatibility complex (MHC) molecules? A. Binding to antibodies B. Producing cytokines C. Presenting antigens to T cells D. Phagocytosis 2. Which of the following cells express MHC class I molecules? A. Nucleated cells B. Antigen-presenting cells C. B cells D. T cells 3. Which of the following cells express MHC class II molecules? A. Nucleated cells B. Antigen-presenting cells C. B cells D. T cells 4. MHC class I molecules present antigens to which type of T cells? A. CD4+ T cells B. CD8+ T cells C. Both CD4+ and CD8+ T cells D. Neither CD4+ nor CD8+ T cells 5. MHC class II molecules present antigens to which type of T cells? A. CD4+ T cells B. CD8+ T cells C. Both CD4+ and CD8+ T cells D. Neither CD4+ nor CD8+ T cells 6. MHC class I molecules primarily present antigens derived from which source? A. Extracellular pathogens B. Intracellular pathogens C. Both extracellular and intracellular pathogens D. Neither extracellular nor intracellular pathogens 7. MHC class II molecules primarily present antigens derived from which source? A. Extracellular pathogens B. Intracellular pathogens C. Both extracellular and intracellular pathogens D. Neither extracellular nor intracellular pathogens 8. What is MHC restriction? A. The process by which T cells recognize only self-MHC molecules B. The limitation of MHC molecules to present only certain types of antigens C. The restriction of MHC expression to specific cell types D. The process by which T cells recognize only foreign MHC molecules
9. How is diversity in MHC molecules primarily generated? A. Through gene rearrangement during lymphocyte development B. By somatic hypermutation during an immune response C. Through the high number of MHC genes and allelic polymorphism D. By isotype switching 10. Which of the following statements about superantigens is true? A. Superantigens bind to MHC molecules and T cell receptors in a highly specific manner B. Superantigens bind to MHC molecules and T cell receptors in a non-specific manner C. Superantigens trigger a weak immune response D. Superantigens are always derived from the host
Answer Key: 1. C 2. A 3. B 4. B 5. A 6. B 7. A 8. A 9. C 10. B
SAQ Quiz: Major Histocompatibility Complexes 1. Explain the role of MHC molecules in the adaptive immune response.
2. Describe the structure of MHC class I and class II molecules, highlighting the differences between them.
3. Explain how MHC molecules contribute to the recognition of self versus non-self in the immune system.
4. Discuss the heritability of MHC genes and their role in transplantation.
5. Describe the process by which antigens are processed and presented on MHC class I molecules.
6. Describe the process by which antigens are processed and presented on MHC class II molecules.
7. Explain the concept of MHC restriction and its importance in T cell activation.
Model Answers: 1. MHC molecules play a critical role in the adaptive immune response by presenting peptide antigens to T cells. MHC class I molecules present endogenously derived antigens, such as those from intracellular pathogens, to CD8+ cytotoxic T cells. MHC class II molecules present exogenously derived antigens, such as those from extracellular pathogens, to CD4+ helper T cells. This antigen presentation triggers T cell activation and the initiation of an adaptive immune response specific to the pathogen. 2. MHC class I molecules consist of a polymorphic heavy (α) chain, non-covalently associated with a non-polymorphic β2-microglobulin light chain. The heavy chain has three domains: α1, α2, and α3. The α1 and α2 domains form the peptide-binding groove. MHC class II molecules consist of two polymorphic chains, α and β, each with two domains. The α1 and β1 domains form the peptide-binding groove. The primary structural difference between MHC class I and class II molecules is the number and arrangement of their chains and domains. 3. MHC molecules contribute to the recognition of self versus non-self by presenting self-peptides alongside foreign peptides. T cells undergo a process called thymic selection during their development, which eliminates T cells that strongly recognize self-peptides presented on self-MHC molecules. This process ensures that T cells respond primarily to foreign antigens while maintaining tolerance to self-antigens. 4. MHC genes are highly polymorphic and are inherited from both parents as a set of linked genes, called a haplotype. This high degree of polymorphism results in a unique set of MHC molecules for each individual, which contributes to the individual's immune system recognizing and responding to a wide range of pathogens. The unique nature of MHC molecules is an important factor in transplantation, as matching the donor's and recipient's MHC molecules can reduce the risk of graft rejection. 5. In MHC class I antigen presentation, intracellular proteins are degraded by the proteasome into peptide fragments. These peptides are transported into the endoplasmic reticulum (ER) by the transporter associated with antigen processing (TAP). In the ER, the peptides are loaded onto MHC class I molecules, which then traffic to the cell surface for presentation to CD8+ cytotoxic T cells. 6. In MHC class II antigen presentation, extracellular proteins are internalized by antigen-presenting cells through endocytosis or phagocytosis. Within endosomes or phagosomes, the proteins are degraded into peptide fragments by acid-dependent proteases. MHC class II molecules, synthesized in the ER, are transported to the endosomes/phagosomes through the action of the invariant chain (Ii). The Ii is degraded, and the peptides are loaded onto the MHC class II molecules. The peptide-MHC class II complexes then traffic to the cell surface for presentation to CD4+ helper T cells.
7. MHC restriction is the concept that T cells can only recognize antigens when they are presented by self-MHC molecules. During T cell development, T cells undergo positive and negative selection in the thymus, which ensures that the surviving T cells can recognize self-MHC molecules presenting foreign antigens but do not react strongly to self-antigens. This process is essential for T cell activation and the initiation of an adaptive immune response specific to the pathogen while maintaining tolerance to self-antigens.
MCQ Quiz: Cells of the Immune System - Lymphoid Cells, Origins, and Development 1. Which of the following is a primary lymphoid organ? a. Spleen b. Lymph node c. Bone marrow d. Tonsils 2. Secondary lymphoid organs are responsible for: a. The production of lymphocytes b. The development and maturation of lymphocytes c. The initiation of adaptive immune responses d. The filtration of blood 3. B cell development begins in the: a. Thymus b. Lymph nodes c. Bone marrow d. Spleen 4. What is the final stage of B cell development? a. Pre-B cell b. Immature B cell c. Plasma cell d. Memory B cell 5. T cell development occurs primarily in the: a. Thymus b. Bone marrow c. Lymph nodes d. Spleen 6. Which process is responsible for generating diversity in T cell receptor (TCR) genes during T cell development? a. Gene duplication b. V(D)J recombination c. Alternative splicing d. Somatic hypermutation 7. Positive selection in T cell development ensures that: a. T cells recognize self-MHC molecules b. T cells do not recognize self-MHC molecules c. T cells recognize foreign antigens d. T cells do not recognize foreign antigens 8. Negative selection in T cell development eliminates T cells that: a. Cannot recognize self-MHC molecules b. React strongly to self-antigens c. React weakly to self-antigens d. Cannot recognize foreign antigens
9. Mature T cells migrate from the thymus to the: a. Bone marrow b. Lymph nodes c. Spleen d. Tonsils 10. Which cell type differentiates into cytotoxic T cells? a. CD4+ T cells b. CD8+ T cells c. B cells d. Natural killer cells 11. Helper T cells are primarily responsible for: a. Directly killing infected cells b. Producing antibodies c. Assisting other immune cells in their functions d. Suppressing immune responses 12. What is the primary function of a plasma cell? a. Phagocytosis b. Antibody production c. Antigen presentation d. Cytotoxicity
Answer Key: 1. C 2. C 3. C 4. C 5. A 6. B 7. A 8. B 9. B 10. B 11. C 12. B
SAQ Quiz: Cells of the Immune System - Lymphoid Cells, Origins, and Development 1. Describe the role of primary lymphoid organs in the development of lymphocytes.
2. Explain the process of B cell maturation and differentiation.
3. Outline the stages of T cell development in the thymus.
4. Explain the importance of positive selection in T cell development.
5. Explain the importance of negative selection in T cell development.
6. Describe the function of CD4+ helper T cells.
7. Describe the function of CD8+ cytotoxic T cells.
Model Answers: 1. Primary lymphoid organs, such as the bone marrow and thymus, are responsible for the production, development, and maturation of lymphocytes. B cells develop in the bone marrow, while T cells develop in the thymus. These organs provide a specialized environment for lymphocyte progenitors to undergo processes such as gene rearrangement, receptor expression, and selection, which are essential for generating a diverse and self-tolerant pool of mature lymphocytes. 2. B cell maturation begins in the bone marrow, where hematopoietic stem cells give rise to B cell progenitors. These progenitors undergo V(D)J recombination to generate a diverse repertoire of B cell receptors (BCRs). As B cells develop, they pass through various stages, including pro-B cells, pre-B cells, and immature B cells. Once B cells express a functional BCR on their surface, they leave the bone marrow and migrate to peripheral lymphoid organs, such as lymph nodes and the spleen. Upon encountering a specific antigen, B cells can differentiate into plasma cells, which produce and secrete antibodies, or memory B cells, which provide long-lasting immunity. 3. T cell development occurs in the thymus and involves several stages, including the double-negative, double-positive, and single-positive stages. During the doublenegative stage, T cell progenitors undergo V(D)J recombination to generate T cell receptors (TCRs) and begin expressing CD4 and CD8 coreceptors. In the doublepositive stage, T cells undergo positive and negative selection based on their ability to recognize self-MHC molecules and self-antigens, respectively. T cells that survive selection become single-positive cells, expressing either CD4 or CD8, and differentiate into CD4+ helper T cells or CD8+ cytotoxic T cells, respectively. Mature T cells then leave the thymus and migrate to peripheral lymphoid organs. 4. Positive selection in T cell development ensures that T cells recognize self-MHC molecules, a process necessary for T cell activation and the initiation of an adaptive immune response. During positive selection, T cells that can weakly recognize selfMHC molecules in the thymus receive survival signals, while T cells that fail to recognize self-MHC molecules undergo apoptosis. 5. Negative selection in T cell development is crucial for maintaining self-tolerance, as it eliminates T cells that react strongly to self-antigens. This process prevents the development of autoimmune diseases, as T cells that recognize self-antigens could potentially attack the host's own tissues. During negative selection, T cells that bind too strongly to self-MHC molecules presenting self-antigens receive apoptotic signals and are eliminated. 6. CD4+ helper T cells play a central role in orchestrating adaptive immune responses. They recognize antigens presented by MHC class II molecules on antigen-presenting cells (APCs) and, upon activation, secrete cytokines that assist other immune cells in their functions. CD4+ helper T cells help B cells produce antibodies, promote the activation and differentiation of CD8+ cytotoxic T cells, and stimulate the activity of macrophages and other immune cells, such as dendritic cells and neutrophils. CD4+ helper T cells are essential for mounting an effective immune response against a wide range of pathogens.
7. CD8+ cytotoxic T cells play a crucial role in the immune system's defense against intracellular pathogens, such as viruses and some bacteria. They recognize antigens presented by MHC class I molecules on the surface of infected or transformed cells. Upon activation, CD8+ cytotoxic T cells release perforin and granzymes, which induce apoptosis in the target cells, leading to the destruction of the infected or transformed cells and the elimination of the pathogen. CD8+ cytotoxic T cells are a vital component of the immune system's ability to clear infections and protect against cancer.
MCQ Quiz: Tolerance in the Immune System 1. What is the primary purpose of immune tolerance? A. To enhance the response to foreign antigens B. To prevent autoimmune diseases C. To increase the diversity of T cell receptors D. To stimulate the production of memory cells 2. Which process is responsible for central tolerance in T cells? A. Positive selection B. Negative selection C. Clonal expansion D. Isotype switching 3. Where does central tolerance occur for B cells? A. Thymus B. Spleen C. Bone marrow D. Lymph nodes 4. Which of the following is NOT a mechanism of peripheral tolerance? A. Anergy B. Suppression by regulatory T cells C. Clonal deletion D. Positive selection 5. Which cells play a critical role in maintaining peripheral tolerance? A. CD4+ helper T cells B. CD8+ cytotoxic T cells C. Regulatory T cells D. B cells 6. What is the main purpose of oral tolerance? A. To suppress immune responses to food antigens B. To enhance the immune response to pathogens C. To stimulate the production of mucosal antibodies D. To facilitate the absorption of nutrients 7. Which mechanism is primarily involved in oral tolerance? A. Activation-induced cell death B. Anergy C. Suppression by regulatory T cells D. Clonal deletion 8. Which type of cell is responsible for central tolerance in B cells? A. T cells B. Macrophages C. Dendritic cells D. B cells
9. In central tolerance, what happens to T cells that strongly bind self-antigens presented by MHC molecules? A. They undergo clonal expansion B. They become memory T cells C. They undergo apoptosis D. They differentiate into effector cells 10. What is the primary purpose of peripheral tolerance? A. To enhance the immune response to pathogens B. To prevent the activation of autoreactive cells that escaped central tolerance C. To increase the diversity of B cell receptors D. To stimulate the production of memory cells 11. Which of the following cells plays a role in the induction of oral tolerance? A. Neutrophils B. Mast cells C. Dendritic cells D. Natural killer cells 12. What type of tolerance primarily occurs in the thymus? A. Central tolerance B. Peripheral tolerance C. Oral tolerance D. Acquired tolerance
Answer Key: 1. B 2. B 3. C 4. D 5. C 6. A 7. C 8. D 9. C 10. B 11. C 12. A
SAQ Quiz: Tolerance in the Immune System 1. Explain the concept of central tolerance and its importance in preventing autoimmune diseases.
2. Describe the process of negative selection in T cell development and its role in central tolerance.
3. Explain the role of peripheral tolerance in the immune system and its mechanisms.
4. Discuss the importance of regulatory T cells in maintaining peripheral tolerance.
5. Describe the process of oral tolerance and its significance in immune regulation.
6. Explain how anergy contributes to peripheral tolerance.
7. What is the difference between central and peripheral tolerance?
Model Answers: 1. Central tolerance is the process by which immature lymphocytes that recognize selfantigens are eliminated or rendered non-functional during their development in primary lymphoid organs. This process is essential for preventing autoimmune diseases, as it ensures that the immune system does not attack the body's own tissues. 2. Negative selection is a critical step in T cell development, occurring in the thymus. During this process, developing T cells that strongly bind self-antigens presented by MHC molecules on thymic epithelial cells undergo apoptosis. This eliminates potentially autoreactive T cells, contributing to the establishment of central tolerance. 3. Peripheral tolerance is a set of mechanisms that prevent the activation of autoreactive cells that have escaped central tolerance, thus maintaining selftolerance in the periphery. Key mechanisms include anergy (functional unresponsiveness), clonal deletion (apoptosis), and suppression by regulatory T cells. 4. Regulatory T cells (Tregs) play a crucial role in maintaining peripheral tolerance by suppressing the activation and function of autoreactive T cells. Tregs produce immunosuppressive cytokines, such as IL-10 and TGF-beta, and inhibit the function of effector T cells and antigen-presenting cells, preventing autoimmune responses. 5. Oral tolerance is the process by which the immune system becomes unresponsive to ingested antigens, such as food proteins. This immune regulation helps prevent unnecessary immune responses against harmless antigens. Oral tolerance is mainly mediated by the induction of regulatory T cells, which suppress immune responses to the ingested antigens. 6. Anergy is a state of functional unresponsiveness in which T cells fail to become activated upon antigen recognition. This mechanism contributes to peripheral tolerance by preventing the activation of autoreactive T cells that have escaped central tolerance, thus avoiding autoimmune responses. 7. Central tolerance occurs during lymphocyte development in primary lymphoid organs (thymus for T cells, bone marrow for B cells) and involves the elimination or inactivation of immature lymphocytes that recognize self-antigens. In contrast, peripheral tolerance takes place in the periphery and involves mechanisms that prevent the activation of autoreactive cells that have escaped central tolerance. Both central and peripheral tolerance are essential for maintaining self-tolerance and preventing autoimmune diseases.
MCQ Quiz: Functional Anatomy of Secondary Lymphoid Organs 1. Which of the following is the primary function of lymph nodes? A. Production of lymphocytes B. Filtration of blood C. Filtration of lymph D. Secretion of hormones 2. What is the primary function of the spleen? A. Production of red blood cells B. Filtration of lymph C. Filtration of blood D. Storage of platelets 3. Which of the following is NOT a component of mucosa-associated lymphoid tissue (MALT)? A. Peyer's patches B. Tonsils C. Lymph nodes D. Bronchus-associated lymphoid tissue 4. Which region of the lymph node contains mostly B cells? A. Cortex B. Paracortex C. Medulla D. Capsule 5. Which of the following is a function of the spleen's red pulp? A. Filtration of blood B. Production of antibodies C. Activation of T cells D. Storage of red blood cells 6. Where are antigens primarily presented to T cells in the lymph node? A. Cortex B. Paracortex C. Medulla D. Capsule 7. Which type of cell is responsible for transporting antigens from the site of infection to the lymph node? A. Neutrophils B. Dendritic cells C. Macrophages D. B cells
8. Which structure in the spleen is responsible for mounting immune responses to blood-borne antigens? A. Red pulp B. White pulp C. Marginal zone D. Capsule 9. Which secondary lymphoid organ is responsible for mounting immune responses to pathogens in the respiratory and gastrointestinal tracts? A. Lymph nodes B. Spleen C. MALT D. Thymus 10. What is the primary purpose of germinal centers in the lymph nodes? A. Production of T cells B. Filtration of lymph C. B cell activation and maturation D. Storage of antigens 11. Which of the following immune cells is predominantly found in the marginal zone of the spleen? A. B cells B. T cells C. Macrophages D. Both A & C 12. What is the primary function of the spleen's white pulp? A. Filtration of blood B. Production of antibodies C. Activation of T cells D. Storage of red blood cells
Answer Key: 1. C 2. C 3. C 4. A 5. A 6. B 7. B 8. B 9. C 10. C 11. D 12. C
SAQ Quiz: Functional Anatomy of Secondary Lymphoid Organs 1. Describe the structure of a lymph node and its role in immune surveillance.
2. Explain the functions of the spleen's white pulp and red pulp.
3. Describe the features and functions of mucosa-associated lymphoid tissue (MALT).
4. Explain the role of germinal centers in lymph node function.
5. Describe the role of the marginal zone in the spleen's immune function.
6. Explain how antigens are transported from the site of infection to the lymph nodes.
7. Discuss the importance of secondary lymphoid organs in the adaptive immune response.
Model Answers: 1. Lymph nodes are bean-shaped structures distributed along the lymphatic vessels. They consist of an outer capsule, an inner cortex with B cell-rich follicles, and a paracortex containing T cells and dendritic cells. The medulla contains lymphatic sinuses and cords of lymphocytes. Lymph nodes filter lymph, trapping antigens and presenting them to lymphocytes, thus facilitating immune surveillance and activation of adaptive immune responses. 2. The spleen consists of two distinct regions: white pulp and red pulp. The white pulp is the site of immune responses to blood-borne antigens and contains lymphocytes and antigen-presenting cells. The red pulp is responsible for filtering blood, removing aged or damaged red blood cells, and recycling iron from hemoglobin. 3. Mucosa-associated lymphoid tissue (MALT) is a collection of immune tissues found in the mucosal linings of the gastrointestinal, respiratory, and urogenital tracts. MALT includes structures such as Peyer's patches, tonsils, and bronchus-associated lymphoid tissue. Its primary function is to protect the body from pathogens that enter through mucosal surfaces by initiating immune responses. 4. Germinal centers are specialized structures within lymph node follicles where B cell activation, proliferation, and differentiation occur. B cells undergo affinity maturation and class-switch recombination in germinal centers, leading to the production of high-affinity antibodies and memory B cells. 5. The marginal zone in the spleen is a region between the red pulp and the white pulp. It contains macrophages, B cells, and specialized dendritic cells that capture and present blood-borne antigens to lymphocytes in the white pulp, initiating immune responses. 6. Antigens are transported from the site of infection to the lymph nodes by dendritic cells. Dendritic cells capture and process antigens at the site of infection, then migrate to the nearest lymph node. In the lymph node, dendritic cells present the processed antigens to T cells, initiating an adaptive immune response. 7. Secondary lymphoid organs, such as lymph nodes, spleen, and MALT, play a crucial role in the adaptive immune response. They provide an environment where antigens can be captured and presented to lymphocytes, leading to the activation, proliferation, and differentiation of T and B cells. This facilitates the generation of effector cells and the production of specific antibodies, ultimately resulting in the elimination of pathogens and the development of immunological memory.
MCQ Quiz: Rejection Immunity 1. Which of the following is a unique feature of placental immunology? A. Maternal immune cells directly attack the fetus B. Maternal and fetal blood mix freely C. Maternal immune system is suppressed during pregnancy D. The placenta forms a barrier that separates maternal and fetal blood 2. Which of the following is NOT a function of the blood-testis barrier? A. Protection of developing sperm from immune attack B. Regulation of the passage of molecules into the testes C. Prevention of pathogens from entering the testes D. Activation of an immune response to sperm antigens 3. Which type of transplant is least likely to cause an immune response? A. Autograft B. Allograft C. Xenograft D. Isograft 4. Which immune cell type is primarily responsible for transplant rejection? A. B cells B. T cells C. Neutrophils D. Macrophages 5. Which type of transplant rejection occurs within minutes to hours after transplantation? A. Hyperacute rejection B. Acute rejection C. Chronic rejection D. Delayed rejection 6. Which type of transplant rejection is primarily mediated by antibodies? A. Hyperacute rejection B. Acute rejection C. Chronic rejection D. Delayed rejection 7. Which of the following is NOT a strategy for preventing transplant rejection? A. Immunosuppressive therapy B. HLA matching C. Induction of tolerance D. Removing all MHC molecules from the donor tissue 8. In the context of transplantation, what does "alloimmune response" refer to? A. The immune response against self-antigens B. The immune response against donor-specific antigens C. The immune response against pathogens D. The immune response against antigens of the same species
9. What is the main function of the placenta in terms of immunology? A. Activate maternal immune responses against the fetus B. Allow maternal and fetal blood to mix freely C. Protect the fetus from maternal immune attack D. Expose the fetus to maternal pathogens 10. Which of the following is an immunologically privileged site? A. Liver B. Lungs C. Testes D. Kidney 11. In graft-versus-host disease, which cells attack the recipient's tissues? A. Recipient T cells B. Donor T cells C. Recipient B cells D. Donor B cells 12. Which term describes a transplant from an identical twin? A. Autograft B. Allograft C. Xenograft D. Isograft
Answer Key: 1. D 2. D 3. A 4. B 5. A 6. A 7. D 8. B 9. C 10. C 11. B 12. D
SAQ Quiz: Rejection Immunity 1. Explain the role of the placenta in preventing maternal immune responses against the fetus.
2. Describe the concept of immunologically privileged sites and provide an example.
3. Explain the difference between autografts, allografts, and xenografts.
4. What factors contribute to transplant rejection?
5. Describe the three types of transplant rejection: hyperacute, acute, and chronic.
6. What is graft-versus-host disease (GVHD) and how does it occur?
7. Explain the strategies used to minimize transplant rejection.
Model Answers: 1. The placenta plays a crucial role in protecting the fetus from maternal immune attack. It forms a physical barrier that separates maternal and fetal blood, preventing the direct interaction between maternal immune cells and fetal tissues. Additionally, the placenta produces immunosuppressive molecules and expresses non-polymorphic MHC molecules, which help to suppress maternal immune responses and maintain immune tolerance. 2. Immunologically privileged sites are areas of the body where immune responses are suppressed or limited to protect delicate tissues. These sites have unique properties, such as the presence of blood-tissue barriers, the expression of immunosuppressive molecules, and a reduced number of antigen-presenting cells. An example of an immunologically privileged site is the testes. 3. Autografts are transplants of tissue from one part of a person's body to another part of the same individual, which typically do not elicit an immune response. Allografts are transplants between two genetically non-identical individuals of the same species and can trigger immune responses. Xenografts are transplants between individuals of different species and have the highest risk of immune rejection. 4. Transplant rejection is mainly driven by the recognition of foreign antigens, particularly MHC molecules, on the donor tissue by the recipient's immune system. T cells are the primary mediators of transplant rejection, as they can recognize donor MHC molecules as foreign and mount an immune response. The degree of HLA mismatch, presence of pre-existing antibodies, and overall immune status of the recipient contribute to the risk of rejection. 5. Hyperacute rejection occurs within minutes to hours after transplantation and is mediated by pre-existing antibodies against donor antigens. Acute rejection occurs within days to weeks after transplantation and is primarily mediated by T cells. Chronic rejection occurs months to years after transplantation and is characterized by progressive fibrosis and vascular damage, which is thought to be due to a combination of T cell-mediated and antibody-mediated responses. 6. Graft-versus-host disease (GVHD) is a complication of allogeneic bone marrow or stem cell transplantation, in which donor T cells recognize recipient tissues as foreign and mount an immune response against them. This immune attack can cause damage to the recipient's organs, particularly the skin, liver, and gastrointestinal tract. 7. Strategies used to minimize transplant rejection include HLA matching between the donor and recipient, immunosuppressive therapy to dampen the recipient's immune response, and induction of tolerance by modulating the recipient's immune system to accept the graft without compromising overall immunity.
MCQ Quiz: Inflammation 1. Which of the following is NOT one of the classical signs of inflammation? A. Rubor (redness) B. Calor (heat) C. Pallor (paleness) D. Tumor (swelling) 2. What is the primary purpose of inflammation? A. To cause pain and discomfort B. To isolate and destroy pathogens or damaged tissue C. To generate heat to fight off infection D. To suppress immune responses 3. Which of the following is a characteristic of acute inflammation? A. Long-lasting and persistent B. Neutrophil infiltration C. Fibrosis and tissue remodeling D. Lymphocyte infiltration 4. Which of the following is a characteristic of chronic inflammation? A. Rapid onset and short duration B. Neutrophil infiltration C. Fibrosis and tissue remodeling D. Vasodilation and increased vascular permeability 5. What is the main cause of redness and heat during inflammation? A. Vasodilation B. Vasoconstriction C. Fibrinogen deposition D. Platelet aggregation 6. Which of the following molecules is a key mediator of vasoactivity during inflammation? A. Histamine B. Interferon-gamma C. Interleukin-10 D. Tumor necrosis factor-alpha 7. What is the term for the process of leukocytes moving from the bloodstream into the surrounding tissues during inflammation? A. Diapedesis B. Chemotaxis C. Phagocytosis D. Opsonization 8. Which molecule acts as a chemical attractant for leukocytes during inflammation? A. Cytokines B. Chemokines C. Complement proteins D. Immunoglobulins
9. What type of leukocyte is typically the first to arrive at the site of inflammation? A. Neutrophils B. Macrophages C. Lymphocytes D. Eosinophils 10. Which of the following is a function of macrophages during inflammation? A. Phagocytosis of pathogens and debris B. Release of pro-inflammatory cytokines C. Promotion of tissue repair and healing D. All of the above 11. Which enzyme is responsible for the synthesis of prostaglandins during inflammation? A. Cyclooxygenase (COX) B. Lipoxygenase C. Phospholipase A2 D. Nitric oxide synthase 12. Which of the following is an anti-inflammatory cytokine? A. Interleukin-1 B. Tumor necrosis factor-alpha C. Interleukin-6 D. Interleukin-10
Answer Key: 1. C 2. B 3. B 4. C 5. A 6. A 7. A 8. B 9. A 10. D 11. A 12. D
SAQ Quiz: Inflammation 1. 2. 3. 4. 5. 6. 7.
Explain the differences between acute and chronic inflammation. Describe the role of histamine in the inflammatory process. Explain the process of leukocyte migration during inflammation. How do prostaglandins contribute to the inflammatory response? Describe the role of neutrophils in inflammation. What is the function of anti-inflammatory cytokines during inflammation? Explain how the complement system contributes to inflammation.
Model Answers: 1. Acute inflammation is a rapid and short-lived response to injury or infection, characterized by increased blood flow, vasodilation, increased vascular permeability, and infiltration of neutrophils. Chronic inflammation, on the other hand, is a longlasting and persistent response often due to unresolved infections, persistent irritants, or autoimmune reactions. It is characterized by infiltration of lymphocytes and macrophages, fibrosis, and tissue remodeling. 2. Histamine is a key mediator of inflammation, released by mast cells, basophils, and platelets. It promotes vasodilation, increased vascular permeability, and the recruitment of leukocytes to the site of inflammation. Histamine also contributes to redness and heat observed during inflammation. 3. Leukocyte migration during inflammation involves several steps: margination (leukocytes move to the periphery of blood vessels), rolling adhesion (leukocytes interact with endothelial cells through selectins), firm adhesion (integrins on leukocytes bind to ICAM-1 on endothelial cells), and diapedesis (leukocytes pass through gaps in the endothelial layer and move into surrounding tissue). Once in the tissue, leukocytes follow chemotactic signals towards the source of inflammation. 4. Prostaglandins are lipid mediators synthesized from arachidonic acid by the enzyme cyclooxygenase (COX). They contribute to the inflammatory response by promoting vasodilation, increasing vascular permeability, sensitizing nociceptors (leading to pain), and enhancing leukocyte recruitment to the site of inflammation. 5. Neutrophils are the first leukocytes to arrive at the site of inflammation. They play a crucial role in the innate immune response by phagocytosing pathogens, releasing antimicrobial proteins and reactive oxygen species, and forming neutrophil extracellular traps (NETs) to trap and kill pathogens. 6. Anti-inflammatory cytokines, such as interleukin-10, help to resolve inflammation by suppressing the production of pro-inflammatory cytokines, inhibiting leukocyte recruitment, and promoting tissue repair and healing. 7. The complement system contributes to inflammation by promoting vasodilation, increasing vascular permeability, and recruiting leukocytes to the site of inflammation. Complement proteins also enhance phagocytosis through opsonization, form the membrane attack complex (MAC) to directly kill pathogens, and contribute to the clearance of immune complexes and apoptotic cells.
MCQ Quiz: Hypersensitivity and Allergy 1. Which of the following describes a Type I hypersensitivity reaction? a. Immune complex-mediated b. Delayed-type hypersensitivity c. Antibody-dependent cell-mediated cytotoxicity d. IgE-mediated 2. What is the primary immune reactant involved in a Type II hypersensitivity reaction? a. IgE b. IgG or IgM c. IgA d. T cells 3. In a Type III hypersensitivity reaction, the immune complexes deposit in tissues, leading to which of the following processes? a. Complement activation b. Anaphylaxis c. Granuloma formation d. Immediate hypersensitivity 4. Which of the following cells play a major role in Type IV hypersensitivity reactions? a. B cells b. Mast cells c. T cells d. Neutrophils 5. What is the most common treatment for anaphylaxis caused by a Type I hypersensitivity reaction? a. Corticosteroids b. Epinephrine c. Antihistamines d. Immunosuppressive drugs 6. Rheumatoid arthritis is an example of which type of hypersensitivity reaction? a. Type I b. Type II c. Type III d. Type IV 7. Which type of hypersensitivity reaction is involved in the development of systemic lupus erythematosus (SLE)? a. Type I b. Type II c. Type III d. Type IV
8. Which of the following is a common clinical manifestation of a Type II hypersensitivity reaction? a. Urticaria b. Hemolytic anemia c. Serum sickness d. Contact dermatitis 9. Tuberculin skin test is an example of which type of hypersensitivity reaction? a. Type I b. Type II c. Type III d. Type IV 10. Asthma is a result of which type of hypersensitivity reaction? a. Type I b. Type II c. Type III d. Type IV 11. Desensitization therapy is used for the management of which type of hypersensitivity reaction? a. Type I b. Type II c. Type III d. Type IV 12. Which type of hypersensitivity reaction can be triggered by penicillin? a. Type I b. Type II c. Type III d. Type I & II
Answer Key: 1. d 2. b 3. a 4. c 5. b 6. c 7. c 8. b 9. d 10. a 11. a 12. d
SAQ Quiz: Hypersensitivity and Allergy 1. Explain the mechanisms involved in a Type I hypersensitivity reaction.
2. Describe the process of antibody-dependent cell-mediated cytotoxicity in Type II hypersensitivity reactions.
3. Explain the role of immune complex deposition in Type III hypersensitivity reactions.
4. Describe the role of T cells in Type IV hypersensitivity reactions.
5. How can allergen immunotherapy be used to treat allergies?
6. What is the role of antihistamines in the management of hypersensitivity reactions?
7. Explain the difference between allergic and non-allergic hypersensitivity reactions.
Model Answers: 1. Type I hypersensitivity reactions are IgE-mediated. Upon initial exposure to an allergen, B cells produce allergen-specific IgE antibodies that bind to the surface of mast cells and basophils. During subsequent exposure, the allergen cross-links these IgE molecules, leading to the activation and degranulation of mast cells and basophils, releasing histamine and other mediators that cause symptoms such as wheezing, itching, and hives. 2. In Type II hypersensitivity reactions, IgG or IgM antibodies bind to antigens on the surface of target cells, leading to antibody-dependent cell-mediated cytotoxicity (ADCC). Natural killer (NK) cells, macrophages, and neutrophils recognize the Fc portion of the bound antibodies, resulting in the activation of these effector cells and the subsequent destruction of the target cells. 3. Type III hypersensitivity reactions involve the formation and deposition of immune complexes (antigen-antibody complexes) in tissues, which leads to complement activation, recruitment of inflammatory cells, and tissue damage. This can result in various clinical manifestations, including vasculitis, glomerulonephritis, and arthritis. 4. Type IV hypersensitivity reactions are T cell-mediated and involve the activation of CD4+ helper T cells and/or CD8+ cytotoxic T cells in response to an antigen. Activated helper T cells release cytokines, which recruit and activate macrophages and other inflammatory cells, leading to tissue damage. In some cases, activated cytotoxic T cells can directly kill target cells. 5. Allergen immunotherapy involves the administration of gradually increasing doses of an allergen to a patient with a Type I hypersensitivity reaction. This process aims to induce immune tolerance to the allergen, reducing the production of allergenspecific IgE and increasing the production of allergen-specific IgG, ultimately resulting in decreased symptoms upon allergen exposure. 6. Antihistamines are used to manage symptoms of hypersensitivity reactions, particularly Type I reactions, by blocking the action of histamine, a key mediator of inflammation released by mast cells and basophils. This can help alleviate symptoms such as itching, hives, and sneezing. 7. Allergic hypersensitivity reactions are immune responses to normally harmless substances (allergens) and typically involve Type I, II, or III hypersensitivity reactions. Non-allergic hypersensitivity reactions do not involve allergens, and are generally caused by other immune mechanisms, such as Type IV hypersensitivity reactions, which are T cell-mediated responses to specific antigens.
MCQ Quiz: Immunodeficiency 1. Which of the following is a primary immunodeficiency disorder? A. DiGeorge Syndrome B. HIV/AIDS C. Malnutrition D. Immunosuppressive therapy 2. Which of the following is considered a secondary immunodeficiency? A. Severe combined immunodeficiency (SCID) B. Chronic granulomatous disease C. Diabetes mellitus D. Bruton's agammaglobulinemia 3. Which immune cell type is most affected in patients with X-linked agammaglobulinemia? A. B cells B. T cells C. Natural killer cells D. Macrophages 4. What is a common clinical feature of primary immunodeficiencies? A. Hypertension B. Obesity C. Recurrent infections D. Migraines 5. Which laboratory investigation is often used to assess the immune system function in suspected immunodeficiency cases? A. Liver function tests B. Creatinine clearance C. Serum immunoglobulin levels D. Blood glucose levels 6. Which of the following is a common treatment approach for primary immunodeficiencies? A. Antibiotic prophylaxis B. Insulin therapy C. Diuretics D. Beta-blockers 7. What is the primary cause of secondary immunodeficiencies? A. Genetic mutations B. Underlying diseases or conditions C. Autoimmune diseases D. Nutritional deficiencies
8. Which of the following is NOT a cause of secondary immunodeficiencies? A. Cancer B. DiGeorge Syndrome C. Immunosuppressive medications D. Chronic renal failure 9. Which of the following is a primary immunodeficiency disorder affecting T cells? A. X-linked agammaglobulinemia B. DiGeorge Syndrome C. Common variable immunodeficiency D. Chronic granulomatous disease 10. In which type of immunodeficiency are patients more susceptible to fungal infections? A. B cell deficiencies B. T cell deficiencies C. Complement deficiencies D. Phagocyte deficiencies 11. Which of the following is a treatment option for severe combined immunodeficiency (SCID)? A. Insulin therapy B. Hematopoietic stem cell transplantation C. Corticosteroids D. Diuretics
Answer Key: 1. A 2. C 3. A 4. C 5. C 6. A 7. B 8. B 9. B 10. B 11. B
SAQ Quiz: Immunodeficiency 1. Briefly explain the difference between primary and secondary immunodeficiencies.
2. Describe the clinical features that might indicate an underlying immunodeficiency disorder.
3. Explain the role of immunoglobulin replacement therapy in the treatment of immunodeficiency.
4. What is the significance of recurrent infections in a patient with an immunodeficiency disorder?
5. Describe the pathophysiology of X-linked agammaglobulinemia.
6. How do T cell deficiencies affect an individual's susceptibility to certain infections?
7. Discuss the use of hematopoietic stem cell transplantation in the treatment of severe combined immunodeficiency (SCID).
Model Answers: 1. Primary immunodeficiencies are genetic disorders that result in impaired immune function from birth, whereas secondary immunodeficiencies are acquired later in life and are often the result of an underlying disease, condition, or external factors such as medications or radiation therapy. 2. Clinical features that might indicate an underlying immunodeficiency disorder include recurrent or persistent infections, poor response to treatment, unusual infections with rare or opportunistic pathogens, failure to thrive or poor growth, and a family history of immunodeficiency. 3. Immunoglobulin replacement therapy involves administering intravenous or subcutaneous immunoglobulins to patients with immunodeficiency, particularly those with antibody deficiencies. This therapy provides passive immunity by supplementing the patient's immune system with functional antibodies, thus reducing the risk of infections and improving the patient's quality of life. 4. Recurrent infections in a patient with an immunodeficiency disorder signify that the immune system is not functioning properly, leaving the individual more susceptible to infections that would otherwise be controlled in healthy individuals. This increased susceptibility can lead to serious complications, long-term organ damage, and even death. 5. X-linked agammaglobulinemia is a primary immunodeficiency disorder caused by mutations in the BTK gene. This genetic defect impairs B cell development and maturation, leading to a severe reduction or absence of circulating B cells and, consequently, low or absent levels of immunoglobulins. Affected individuals are more susceptible to recurrent bacterial infections, particularly those involving the respiratory and gastrointestinal tracts. 6. T cell deficiencies affect an individual's susceptibility to certain infections by impairing cell-mediated immunity, which is essential for defense against intracellular pathogens such as viruses, certain bacteria, and fungi. As a result, individuals with T cell deficiencies are more prone to severe or recurrent infections caused by these types of pathogens. 7. Hematopoietic stem cell transplantation is a treatment option for severe combined immunodeficiency (SCID), which involves the replacement of the patient's defective immune system with healthy hematopoietic stem cells from a compatible donor. This procedure can potentially cure the underlying immunodeficiency and restore normal immune function, allowing the individual to lead a normal life without the constant risk of life-threatening infections.
MCQ Quiz: Immunity Against Infectious Organisms and Evasion of the Immune Response 1. Which of the following is a common mechanism by which pathogens cause tissue damage? A. Production of exotoxins B. Activation of the immune system C. Hijacking of host cell machinery D. All of the above 2. What is the first step in the process of infection? A. Colonization B. Invasion C. Evasion D. Transmission 3. Which of the following is an example of an extracellular pathogen? A. Bacteria within a phagosome B. Viruses replicating within a host cell C. Bacteria in the extracellular fluid D. Intracellular protozoan parasites 4. Which immune cell is primarily responsible for eliminating extracellular bacteria? A. Neutrophils B. CD8+ cytotoxic T cells C. Natural killer cells D. B cells 5. Which immune mechanism is used to eliminate intracellular pathogens? A. Phagocytosis B. Cell-mediated immunity C. Complement activation D. Humoral immunity 6. How do intracellular pathogens evade the immune system? A. Avoiding phagocytosis B. Antigenic variation C. Inhibiting antigen presentation D. All of the above 7. Which of the following immune cells is most effective against intracellular viral infections? A. Neutrophils B. CD8+ cytotoxic T cells C. Natural killer cells D. B cells 8. How do some pathogens evade the host's immune system by antigenic variation? A. By changing the composition of their cell walls B. By modifying their surface proteins C. By secreting immunosuppressive molecules D. By hiding inside host cells
9. What is a common strategy used by extracellular pathogens to avoid immune recognition? A. Forming biofilms B. Inhibiting apoptosis C. Molecular mimicry D. Inducing host cell autophagy 10. What is the primary function of antibodies in the defense against extracellular pathogens? A. Inducing apoptosis B. Neutralization C. Phagocytosis D. Cytotoxicity 11. Which immune cell type is involved in the defense against extracellular parasites? A. Neutrophils B. Eosinophils C. Natural killer cells D. Dendritic cells 12. How do some intracellular bacteria evade host immune responses? A. By escaping from phagosomes into the cytosol B. By inhibiting MHC class II expression C. By preventing phagosome-lysosome fusion D. All of the above
Answer Key: 1. D 2. A 3. C 4. A 5. B 6. D 7. B 8. B 9. C (and/or A) 10. B 11. B 12. D
SAQ Quiz: Immunity Against Infectious Organisms and Evasion of the Immune Response 1. Explain how pathogens can cause tissue damage during infection.
2. Describe the difference between extracellular and intracellular pathogens and provide examples of each.
3. Explain how the immune system targets extracellular pathogens.
4. Describe how the immune system targets intracellular pathogens.
5. Explain the concept of antigenic variation and how it helps pathogens evade the immune system.
6. Discuss how molecular mimicry is used by pathogens to evade the immune response.
7. Explain how biofilms help extracellular pathogens avoid immune recognition.
Model Answers: 1. Pathogens can cause tissue damage during infection through several mechanisms, including the production of exotoxins, activation of the host's immune system, and hijacking of host cell machinery for their own replication. Exotoxins can directly damage host cells, while the immune response can cause inflammation and collateral damage to healthy tissues. Intracellular pathogens may also disrupt normal cellular functions and induce cell death. 2. Extracellular pathogens are found outside host cells, usually in the extracellular fluid or adhering to cell surfaces. Examples include Streptococcus pneumoniae and Staphylococcus aureus. Intracellular pathogens, on the other hand, invade and replicate within host cells. Examples include Mycobacterium tuberculosis and Listeria monocytogenes. 3. The immune system targets extracellular pathogens primarily through humoral immunity. Antibodies produced by B cells bind to pathogens and neutralize them, facilitate their phagocytosis by macrophages and neutrophils (opsonization), or activate the complement system, which can directly kill pathogens or promote their clearance. Neutrophils are also essential for eliminating extracellular bacteria through phagocytosis and the release of antimicrobial substances. 4. The immune system targets intracellular pathogens through cell-mediated immunity. CD8+ cytotoxic T cells recognize and kill infected cells, while CD4+ helper T cells produce cytokines that activate macrophages, enhancing their ability to kill intracellular pathogens. Natural killer (NK) cells also play a role in targeting virally infected cells and tumor cells. 5. Antigenic variation is a mechanism used by some pathogens to evade the host's immune system. It involves the alteration of surface proteins, making it difficult for the host's immune system to recognize and target the pathogen. By constantly changing their surface antigens, pathogens can avoid detection by the host's existing immune memory and prolong the infection. 6. Molecular mimicry is a strategy used by some pathogens to evade the immune response. It involves the expression of molecules that closely resemble host molecules, making it difficult for the immune system to distinguish between self and non-self. This can lead to reduced immune recognition and elimination of the pathogen. 7. Biofilms are complex, multicellular communities of microorganisms embedded in a self-produced extracellular matrix. They help extracellular pathogens avoid immune recognition by providing a physical barrier that protects the pathogens from the host's immune cells and antibodies. Additionally, biofilms can alter the local microenvironment, making it less favorable for immune cell function and promoting pathogen survival.
MCQ Quiz: Viruses and Immunity 1. Which of the following is NOT a property of viruses? A. They are cellular organisms. B. They rely on host cells for replication. C. They have either DNA or RNA as their genetic material. D. They can infect a variety of hosts. 2. What is the purpose of the viral capsid? A. To provide energy for viral replication B. To protect the viral genome C. To facilitate viral attachment to host cells D. To assist in viral assembly 3. What type of viral antigen is typically found on the surface of enveloped viruses? A. Glycoproteins B. Lipids C. Capsid proteins D. Nucleic acids 4. Which innate immune response is specifically aimed at targeting viral infections? A. Complement system activation B. Fever C. Interferon production D. Inflammation 5. Which immune cells are primarily responsible for killing virus-infected cells? A. Macrophages B. Neutrophils C. CD8+ cytotoxic T cells D. B cells 6. Which type of immunity is responsible for the production of virus-specific antibodies? A. Innate immunity B. Humoral immunity C. Cell-mediated immunity D. Passive immunity 7. Which of the following is a mechanism by which viruses evade the host immune response? A. Antigenic variation B. MHC downregulation C. Inhibition of interferon production D. All of the above 8. What is the primary role of natural killer (NK) cells in antiviral immunity? A. Production of virus-specific antibodies B. Phagocytosis of viral particles C. Killing of virus-infected cells D. Activation of the complement system
9. How do neutralizing antibodies protect against viral infections? A. By directly killing virus-infected cells B. By blocking viral attachment or entry into host cells C. By promoting phagocytosis of viral particles D. By stimulating the production of interferons 10. What is the main function of CD4+ helper T cells during a viral infection? A. Killing virus-infected cells B. Producing virus-specific antibodies C. Producing cytokines to orchestrate the immune response D. Directly neutralizing viral particles 11. Which of the following cells act as antigen-presenting cells during viral infections? A. B cells B. Dendritic cells C. Macrophages D. All of the above 12. How do some viruses interfere with MHC class I presentation to evade the immune response? A. By downregulating MHC class I molecules on the cell surface B. By blocking the processing of viral antigens C. By preventing the loading of viral peptides onto MHC class I molecules D. All of the above
Answer Key: 1. A 2. B 3. A 4. C 5. C 6. B 7. D 8. C 9. B 10. C 11. D 12. D
SAQ Quiz: Viruses and Immunity 1. Describe the basic structure of a virus.
2. Explain how interferons contribute to the innate immune response against viral infections.
3. Describe the role of CD8+ cytotoxic T cells in the adaptive immune response to viruses.
4. Explain how neutralizing antibodies protect the host from viral infections.
5. Describe the process of antigen presentation during a viral infection and the involvement of MHC molecules.
6. Discuss the role of CD4+ helper T cells in the immune response to viral infections.
7. Explain how antigenic variation allows some viruses to evade the host immune response.
Model Answers: 1. Viruses consist of a nucleic acid genome, either DNA or RNA, surrounded by a protein coat called a capsid. Some viruses also possess a lipid envelope derived from the host cell membrane, which contains viral glycoproteins that play a role in viral attachment and entry into host cells. 2. Interferons are a group of cytokines produced by virus-infected cells and other immune cells in response to viral infections. They inhibit viral replication, activate natural killer (NK) cells and macrophages, and enhance the adaptive immune response by promoting antigen presentation and the activation of T cells. 3. CD8+ cytotoxic T cells play a crucial role in the adaptive immune response to viruses by recognizing and killing virus-infected cells. They do this by binding to viral peptides presented on MHC class I molecules on the surface of infected cells, which triggers the release of cytotoxic molecules, such as perforin and granzymes, leading to the targeted destruction of the infected cell. 4. Neutralizing antibodies are a type of virus-specific antibody that can protect the host from viral infections by blocking viral attachment or entry into host cells. This prevents the virus from infecting new cells and spreading within the host, effectively neutralizing the virus. 5. During a viral infection, antigen-presenting cells (APCs), such as dendritic cells, macrophages, and B cells, process viral antigens and present them on their surface in complex with MHC molecules. MHC class I molecules present endogenously derived viral peptides to CD8+ cytotoxic T cells, while MHC class II molecules present exogenously derived viral peptides to CD4+ helper T cells. This process of antigen presentation is critical for the activation of T cells and the initiation of an adaptive immune response against the virus. 6. CD4+ helper T cells play a central role in the immune response to viral infections by producing cytokines that orchestrate various aspects of the immune response. They stimulate the activation and proliferation of CD8+ cytotoxic T cells, promote the differentiation of B cells into antibody-producing plasma cells, and enhance the function of macrophages and other immune cells involved in antiviral immunity. 7. Antigenic variation is a strategy used by some viruses to evade the host immune response. It involves changes in the viral surface antigens, which can occur through genetic mutations or the recombination of viral genes. These changes alter the antigenic properties of the virus, making it difficult for the host immune system to recognize and target the virus effectively. This allows the virus to evade the immune response and persist in the host.
MCQ Quiz: Bacteria and Immunity 1. Which of the following is a common feature of bacterial cell walls? A. Cholesterol B. Peptidoglycan C. Glycoproteins D. Lipopolysaccharide 2. What is the role of Toll-like receptors (TLRs) in the innate immune response to bacterial infections? A. Phagocytosis of bacteria B. Recognition of bacterial PAMPs C. Production of antibodies D. Activation of B cells 3. Which type of immune cell primarily phagocytoses bacteria during the early stages of infection? A. Neutrophils B. CD8+ cytotoxic T cells C. CD4+ helper T cells D. B cells 4. What is the primary role of CD4+ helper T cells in the adaptive immune response to bacterial infections? A. Phagocytosis of bacteria B. Production of antibodies C. Cytotoxicity towards infected cells D. Production of cytokines to orchestrate the immune response 5. Which type of antibody is most effective at opsonizing bacteria? A. IgA B. IgD C. IgE D. IgG 6. Which of the following is an example of an extracellular bacterium? A. Listeria monocytogenes B. Mycobacterium tuberculosis C. Streptococcus pneumoniae D. Salmonella enterica 7. Which immune cells are responsible for the formation of granulomas in response to intracellular bacterial infections? A. Neutrophils B. Macrophages C. CD8+ cytotoxic T cells D. B cells
8. What is the primary function of antibodies in the immune response to extracellular bacteria? A. Killing infected cells B. Neutralizing bacterial toxins C. Promoting phagocytosis D. Inducing inflammation 9. Which MHC class molecule presents exogenously derived bacterial peptides to CD4+ helper T cells? A. MHC class I B. MHC class II C. MHC class III D. MHC class IV 10. What is the primary function of complement proteins in the immune response to bacterial infections? A. Opsonization of bacteria B. Production of cytokines C. Induction of apoptosis in infected cells D. Activation of B cells 11. Which of the following mechanisms is used by some bacteria to evade the host immune response? A. Production of superantigens B. Antigenic variation C. Inhibition of phagosome-lysosome fusion D. All of the above 12. In the context of bacterial infections, what is the primary role of natural killer (NK) cells? A. Phagocytosis of bacteria B. Production of antibodies C. Killing of infected cells D. Activation of macrophages
Answer Key: 1. B 2. B 3. A 4. D 5. D 6. C 7. B 8. C 9. B 10. A 11. D 12. C
SAQ Quiz: Bacteria and Immunity 1. Describe the differences between gram-positive and gram-negative bacteria and their implications for the immune response.
2. Explain the role of neutrophils in the innate immune response to bacterial infections.
3. Discuss how the adaptive immune response is activated during a bacterial infection.
4. Explain the process of opsonization and its importance in the immune response to bacterial infections.
5. Describe how some bacteria can evade the host immune response by hiding within host cells.
6. Explain how natural killer (NK) cells contribute to the immune response against bacterial infections.
7. Discuss the role of the complement system in the immune response to bacterial infections.
Model Answers: 1. Gram-positive bacteria have a thick peptidoglycan layer in their cell walls and lack an outer membrane, while gram-negative bacteria have a thin peptidoglycan layer and an outer membrane containing lipopolysaccharide (LPS). The immune response differs because gram-positive bacteria are primarily recognized by Toll-like receptor 2 (TLR2), while gram-negative bacteria are recognized by TLR4 due to the presence of LPS. Moreover, gram-negative bacteria are often more resistant to antibiotics due to their outer membrane. 2. Neutrophils are the most abundant type of white blood cell and play a critical role in the innate immune response to bacterial infections. They are rapidly recruited to the site of infection, where they phagocytose bacteria, release antimicrobial granules, and produce reactive oxygen species to kill the bacteria. Neutrophils can also form neutrophil extracellular traps (NETs) to immobilize and kill bacteria. 3. The adaptive immune response to bacterial infections is initiated when antigenpresenting cells (APCs), such as dendritic cells and macrophages, phagocytose bacteria and present bacterial peptides on MHC class II molecules to CD4+ helper T cells. The activation of CD4+ T cells leads to the production of cytokines that orchestrate the immune response, including the activation of B cells to produce antibodies and the activation of CD8+ cytotoxic T cells to kill infected cells. 4. Opsonization is the process by which pathogens are coated with molecules, such as antibodies or complement proteins, that facilitate their recognition and phagocytosis by immune cells. This process is important in the immune response to bacterial infections because it enhances the efficiency of bacterial clearance by phagocytes, such as neutrophils and macrophages. 5. Some bacteria can evade the host immune response by hiding within host cells, such as macrophages. By residing within these cells, bacteria can avoid recognition by antibodies and other components of the immune system. Intracellular bacteria can also manipulate host cell processes to promote their own survival and replication, such as inhibiting phagosome-lysosome fusion to prevent bacterial degradation. 6. Natural killer (NK) cells contribute to the immune response against bacterial infections primarily by producing cytokines, such as interferon-gamma (IFN-γ), which activate macrophages to enhance their bactericidal activity. Additionally, NK cells can directly kill infected cells through the release of cytotoxic granules, although this is a less prominent role in the context of bacterial infections compared to viral infections. 7. The complement system plays a crucial role in the immune response to bacterial infections through a variety of mechanisms, including opsonization, direct bacterial lysis, and the recruitment of immune cells to the site of infection. Activation of the complement system can result in the formation of the membrane attack complex (MAC), which directly lyses bacteria by forming pores in their membranes. Complement proteins also promote the recruitment and activation of immune cells, such as neutrophils and macrophages, by serving as chemoattractants and opsonins, thus enhancing the overall immune response against bacterial infections.
MCQ Quiz: Parasites and Immunity 1. Which type of immune response is most effective against extracellular parasites? a. Humoral immunity b. Cell-mediated immunity c. Innate immunity d. Passive immunity 2. Which cells are primarily involved in defense against intracellular parasites? a. Neutrophils b. Eosinophils c. CD4+ T cells d. CD8+ T cells 3. Which immunoglobulin class is most commonly associated with immunity against parasitic infections? a. IgA b. IgD c. IgE d. IgG 4. What is the primary function of eosinophils in response to parasitic infections? a. Phagocytosis b. Production of cytokines c. Release of cytotoxic granules d. Activation of the complement system 5. Which of the following cytokines is crucial for the activation of macrophages against intracellular parasites? a. IL-4 b. IL-10 c. IFN-γ d. TNF-α 6. Which type of T helper cell is predominantly involved in the immune response against parasites? a. Th1 b. Th2 c. Th17 d. Tfh 7. How do some parasites evade the host immune response? a. Antigenic variation b. Inhibition of phagosome-lysosome fusion c. Immunosuppression d. All of the above
8. What is the main role of mast cells during a parasitic infection? a. Phagocytosis of parasites b. Release of histamine and other inflammatory mediators c. Production of antibodies d. Direct killing of parasites through cytotoxic granules 9. In which way does the complement system contribute to the immune response against parasites? a. Opsonization b. Recruitment of immune cells c. Direct lysis of parasites d. All of the above 10. Which type of immune response is most effective against helminth infections? a. Humoral immunity b. Cell-mediated immunity c. Innate immunity d. Passive immunity 11. How do some protozoan parasites evade the immune system? a. Forming a cyst stage b. Antigenic variation c. Inhibiting host cell apoptosis d. All of the above 12. What is the primary role of IgE antibodies during a parasitic infection? a. Neutralization of parasites b. Activation of the complement system c. Opsonization d. Mediating immune cell activation and release of inflammatory mediators
Answer Key: 1. a 2. d 3. c 4. c 5. c 6. b 7. d 8. b 9. d 10. a 11. d 12. d
SAQ Quiz: Parasites and Immunity 1. Describe the main differences between the immune response against extracellular and intracellular parasites.
2. Explain the role of eosinophils in the defense against helminth infections.
3. How do Th2 cells contribute to the immune response against parasitic infections?
4. Describe the mechanisms by which parasites evade the host's immune response.
5. Explain the role of mast cells in the immune response against parasites.
6. Discuss the importance of the complement system in immunity against parasites.
7. How do IgE antibodies contribute to the defense against parasitic infections?
Model Answers: 1. The immune response against extracellular parasites, such as helminths, predominantly involves humoral immunity, which includes the production of antibodies (IgE) that bind to and neutralize the parasites. Eosinophils and mast cells also play important roles in the defense against extracellular parasites. In contrast, the immune response against intracellular parasites, such as protozoa, relies mainly on cell-mediated immunity. This involves the activation of CD8+ cytotoxic T cells and the stimulation of macrophages by cytokines such as IFN-γ, which helps eliminate the intracellular parasites. 2. Eosinophils play a crucial role in the defense against helminth infections by releasing cytotoxic granules containing proteins such as major basic protein, eosinophil cationic protein, and eosinophil peroxidase. These proteins are toxic to helminths and can cause damage to their outer layers, leading to their death. Additionally, eosinophils can release cytokines that promote inflammation and recruit other immune cells to the site of infection. 3. Th2 cells contribute to the immune response against parasitic infections by producing cytokines, such as IL-4, IL-5, and IL-13, which promote humoral immunity and the activation of eosinophils, mast cells, and basophils. These cytokines also stimulate the production of IgE antibodies, which play a critical role in the defense against parasites. 4. Parasites can evade the host's immune response through various mechanisms, such as antigenic variation, inhibition of phagosome-lysosome fusion, immunosuppression, forming a cyst stage, and inhibiting host cell apoptosis. These strategies allow parasites to persist in the host and continue their life cycle. 5. Mast cells play a role in the immune response against parasites by releasing histamine and other inflammatory mediators upon activation by IgE antibodies or other stimuli. This leads to increased vascular permeability, recruitment of immune cells, and promotion of inflammation, which helps to eliminate the parasites. 6. The complement system is important in immunity against parasites by contributing to opsonization, recruitment of immune cells, and direct lysis of parasites. These mechanisms enhance the overall immune response against parasites and promote their elimination from the host. 7. IgE antibodies contribute to the defense against parasitic infections by binding to parasites and mediating immune cell activation, such as eosinophils, mast cells, and basophils. This leads to the release of inflammatory mediators and cytotoxic granules that help eliminate the parasites. Additionally, IgE antibodies can bind to FcεRI receptors on mast cells and basophils, sensitizing these cells for future encounters with the same parasite.
MCQ Quiz: Immune Evasion Mechanisms 1. What is antigenic variation? A. The process by which a pathogen changes its surface proteins to avoid recognition by the host's immune system B. The ability of a pathogen to survive inside host cells and avoid immune detection C. The suppression of the host's immune response by a pathogen D. The ability of a pathogen to hide in immune-privileged sites 2. Which of the following is an example of latency? A. The HIV virus integrating into the host genome B. The herpes simplex virus remaining dormant in sensory ganglia C. The Plasmodium parasite changing its surface antigens D. The Mycobacterium tuberculosis bacteria surviving within macrophages 3. How can a pathogen resist immune effector mechanisms? A. By producing proteins that block complement activation B. By undergoing antigenic variation C. By hiding in immune-privileged sites D. All of the above 4. Which of the following is an example of immunosuppression? A. The Epstein-Barr virus inhibiting the expression of MHC class I molecules B. The influenza virus undergoing antigenic drift C. The hepatitis B virus integrating into the host genome D. The varicella-zoster virus establishing latency in dorsal root ganglia 5. What are immune-privileged sites? A. Locations in the body where the immune response is limited or restricted B. Sites where pathogens can replicate without being detected by the immune system C. Sites where the immune system is more active than in other parts of the body D. Locations where pathogens can establish latency 6. How can a pathogen exploit the host's immune system to aid in its life cycle? A. By inducing an inflammatory response that promotes its dissemination B. By undergoing antigenic variation to avoid immune detection C. By establishing latency within host cells D. By producing proteins that block complement activation 7. Which of the following pathogens undergoes antigenic variation to evade the host's immune system? A. Mycobacterium tuberculosis B. Human immunodeficiency virus (HIV) C. Trypanosoma brucei D. Herpes simplex virus
8. What is the main purpose of immune evasion mechanisms? A. To promote the survival and replication of pathogens within the host B. To enhance the host's immune response against the pathogen C. To help the pathogen spread to new hosts D. To prevent the host from developing immunity to the pathogen 9. Which of the following is NOT an immune evasion mechanism? A. Antigenic variation B. Latency C. Resistance to immune effector mechanisms D. Induction of a strong immune response 10. How does the human immunodeficiency virus (HIV) evade the immune system? A. By downregulating the expression of MHC class I molecules B. By undergoing antigenic variation C. By integrating into the host genome D. Both A and C 11. How is the immune system exploited in the life cycle of Plasmodium parasites? A. It helps in the dissemination of the parasites throughout the body and infect new blood cells B. It promotes the replication of the parasites within host cells C. It aids in the transmission of the parasites to new hosts D. It limits the severity of the infection by killing the parasites 12. Which of the following pathogens can establish latency in immune-privileged sites? A. Mycobacterium tuberculosis B. Trypanosoma brucei C. Human papillomavirus (HPV) D. Herpes simplex virus
Answer Key: 1. A 2. B 3. D 4. A 5. A 6. A 7. C 8. A 9. D 10. D 11. A 12. D
SAQ Quiz: Immune Evasion Mechanisms 1. Explain the concept of antigenic variation and provide an example of a pathogen that employs this immune evasion mechanism.
2. Describe the process of latency and give an example of a pathogen that uses latency as an immune evasion strategy.
3. How do some pathogens resist immune effector mechanisms?
4. Describe an example of immunosuppression by a pathogen.
5. What are immune-privileged sites, and why are they important for some pathogens?
6. Explain how a pathogen can exploit the host's immune system to aid in its life cycle.
7. Provide an example of a pathogen that shelters in immune-privileged sites to evade the immune response.
Model Answers: 1. Antigenic variation is the process by which a pathogen alters its surface proteins to evade recognition by the host's immune system. This allows the pathogen to escape detection and neutralization by the host's antibodies. An example of a pathogen that employs antigenic variation is Trypanosoma brucei, the causative agent of African sleeping sickness. 2. Latency is the ability of a pathogen to remain dormant within host cells or tissues, evading the host's immune system until reactivation under certain conditions. An example of a pathogen that uses latency as an immune evasion strategy is the herpes simplex virus (HSV), which can establish latency in sensory ganglia and reactivate later, causing recurrent infections. 3. Some pathogens resist immune effector mechanisms by producing proteins that interfere with the host's immune response. For example, some bacteria produce proteases that cleave components of the complement system, preventing its activation and the subsequent destruction of the pathogen. 4. An example of immunosuppression by a pathogen is the Epstein-Barr virus, which can inhibit the expression of MHC class I molecules on the surface of infected cells, preventing recognition and elimination by cytotoxic T cells. 5. Immune-privileged sites are locations in the body where the immune response is limited or restricted, allowing certain pathogens to evade immune detection. These sites include the central nervous system, eyes, and testes. Some pathogens, such as the herpes simplex virus, can establish latency in immune-privileged sites to evade the immune response. 6. A pathogen can exploit the host's immune system to aid in its life cycle by inducing an inflammatory response that promotes its dissemination. For example, the Plasmodium parasite, which causes malaria, induces an inflammatory response that helps the parasite disseminate throughout the body and infect new red blood cells. 7. The varicella-zoster virus (VZV), which causes chickenpox and shingles, is an example of a pathogen that shelters in immune-privileged sites to evade the immune response. VZV establishes latency in the dorsal root ganglia, an immune-privileged site, and can reactivate later to cause shingles.
MCQ Quiz: Autoimmunity 1. Which of the following is NOT a pathogenic mechanism of autoimmune diseases? a. Molecular mimicry b. Exposure of hidden epitopes c. Epitope spreading d. Phagocytosis 2. Exposure of hidden epitopes can lead to autoimmunity by: a. Allowing immune cells to recognize self-antigens as foreign b. Inducing inflammation in response to harmless antigens c. Promoting antibody production against self-tissues d. Both a and c 3. What is the process of epitope spreading? a. The recognition of multiple epitopes on a single antigen b. The recognition of multiple epitopes on different antigens within a self-tissue c. The spreading of an immune response to previously ignored epitopes within a tissue d. The recognition of self-epitopes by multiple immune cells 4. Molecular mimicry is a mechanism of autoimmunity in which: a. Self-antigens are modified to resemble foreign antigens b. Foreign antigens resemble self-antigens, leading to cross-reactivity c. Self-antigens are recognized as foreign due to mutations d. Autoantibodies are produced against multiple epitopes on a single selfantigen 5. Which of the following autoimmune diseases is characterized by the destruction of pancreatic beta cells? a. Rheumatoid arthritis b. Systemic lupus erythematosus c. Multiple sclerosis d. Type 1 diabetes mellitus 6. A genetic predisposition to autoimmunity is often associated with: a. Altered antigen processing b. Altered cytokine production c. Altered MHC expression d. All of the above 7. Which of the following factors can contribute to the development of autoimmunity? a. Infections b. Hormones c. Environmental factors d. All of the above
8. The term "forbidden clone" refers to: a. A lymphocyte that has escaped the central tolerance process b. A lymphocyte that has developed resistance to regulatory T cells c. A lymphocyte that has undergone uncontrolled clonal expansion d. A lymphocyte that has lost its ability to recognize foreign antigens 9. The breakdown of immune tolerance can lead to autoimmunity by: a. Inducing an immune response against self-antigens b. Promoting the production of autoantibodies c. Allowing the activation of autoreactive T cells d. All of the above 10. Regulatory T cells play a critical role in preventing autoimmunity by: a. Suppressing the activation of autoreactive T cells b. Promoting the production of anti-inflammatory cytokines c. Inducing apoptosis of autoreactive immune cells d. All of the above 11. Which of the following is NOT a mechanism by which infections can trigger autoimmunity? a. Molecular mimicry b. Polyclonal activation of B cells c. Breakdown of immune tolerance d. Activation of the complement system 12. The autoimmune disease multiple sclerosis primarily affects which part of the body? a. Joints b. Kidneys c. Central nervous system d. Skin
Answer Key: 1. D 2. D 3. C 4. B 5. D 6. D 7. D 8. A 9. D 10. D 11. D 12. C
SAQ Quiz: Autoimmunity 1. Explain the concept of molecular mimicry and how it can contribute to autoimmunity.
2. Describe the role of regulatory T cells in preventing autoimmunity.
3. What is the difference between central tolerance and peripheral tolerance?
4. Explain the role of genetic factors in autoimmunity, including examples of specific genes associated with an increased risk of autoimmune diseases.
5. How can environmental factors contribute to the development of autoimmunity?
6. What is the "forbidden clone" hypothesis in the context of autoimmunity?
7. Describe the mechanism of epitope spreading and how it can lead to autoimmunity.
Model Answers: 1. Molecular mimicry is a phenomenon in which foreign antigens resemble selfantigens, leading to cross-reactivity between the immune response against the foreign antigen and the self-tissue. This can result in autoimmune damage as the immune system mistakenly targets self-tissues. 2. Regulatory T cells play a crucial role in preventing autoimmunity by suppressing the activation of autoreactive T cells, promoting the production of anti-inflammatory cytokines, and inducing apoptosis of autoreactive immune cells. This helps maintain immune tolerance to self-antigens. 3. Central tolerance is the process by which autoreactive lymphocytes are eliminated or rendered non-functional in primary lymphoid organs (e.g., bone marrow for B cells and thymus for T cells) during their development. Peripheral tolerance is the process by which autoreactive lymphocytes that have escaped central tolerance are controlled or eliminated in secondary lymphoid organs and other peripheral tissues. 4. Genetic factors play a significant role in autoimmunity, as certain gene variants are associated with an increased risk of developing autoimmune diseases. One example is the association of specific human leukocyte antigen (HLA) genes, such as HLADRB1, with an increased risk of developing rheumatoid arthritis or multiple sclerosis. 5. Environmental factors can contribute to the development of autoimmunity through various mechanisms, such as molecular mimicry, exposure to certain chemicals or drugs, and alterations in the gut microbiota. These factors can trigger the breakdown of immune tolerance and lead to autoimmune reactions. 6. The "forbidden clone" hypothesis suggests that autoimmunity results from the presence of autoreactive lymphocytes that have escaped the central tolerance process. These "forbidden clones" can potentially recognize self-antigens and initiate an autoimmune response if not properly controlled by peripheral tolerance mechanisms. 7. Epitope spreading is a process in which an immune response to a specific epitope within a self-tissue spreads to previously ignored epitopes within the same tissue. This can lead to autoimmunity as the immune system begins to target a broader range of self-antigens, causing more extensive tissue damage.
MCQ Quiz: Common Autoimmune Conditions 1. Which autoimmune disorder is characterized by the destruction of insulin-producing beta cells in the pancreas? a. Myasthenia gravis b. Type 1 diabetes mellitus c. Hashimoto's thyroiditis d. Systemic lupus erythematosus 2. In myasthenia gravis, autoantibodies primarily target which receptor? a. Insulin receptor b. Acetylcholine receptor c. Thyroid-stimulating hormone receptor d. Nuclear antigen 3. Hashimoto's thyroiditis is characterized by the production of autoantibodies against which thyroid components? a. Thyroid-stimulating hormone receptor and thyroglobulin b. Thyroid peroxidase and thyroglobulin c. Thyroid peroxidase and thyroid-stimulating hormone receptor d. Thyroglobulin and thyroid hormone 4. Graves' disease is caused by autoantibodies that stimulate which receptor? a. Insulin receptor b. Acetylcholine receptor c. Thyroid-stimulating hormone receptor d. Nuclear antigen 5. Rheumatic fever is an autoimmune reaction that can occur following an infection with which type of bacteria? a. Staphylococcus aureus b. Streptococcus pneumoniae c. Streptococcus pyogenes d. Escherichia coli 6. Rheumatoid arthritis is characterized by inflammation and destruction of which type of joint? a. Fibrous joint b. Cartilaginous joint c. Synovial joint d. Suture joint 7. Antinuclear antibodies (ANAs) are most commonly associated with which autoimmune disorder? a. Type 1 diabetes mellitus b. Myasthenia gravis c. Hashimoto's thyroiditis d. Systemic lupus erythematosus
8. Which autoimmune condition is characterized by inflammation and damage to the joints, skin, kidneys, blood cells, brain, and heart? a. Systemic lupus erythematosus b. Hashimoto's thyroiditis c. Rheumatoid arthritis d. Graves' disease 9. In which autoimmune disease do immune cells mistakenly attack the myelin sheath surrounding nerve cells? a. Multiple sclerosis b. Rheumatoid arthritis c. Graves' disease d. Type 1 diabetes mellitus 10. Which of the following conditions is characterized by dry eyes and dry mouth due to an autoimmune attack on exocrine glands? a. Sjogren's syndrome b. Systemic lupus erythematosus c. Hashimoto's thyroiditis d. Rheumatoid arthritis 11. Which autoimmune disorder is characterized by the formation of granulomas in various organs, most commonly the lungs and lymph nodes? a. Sarcoidosis b. Rheumatoid arthritis c. Systemic lupus erythematosus d. Graves' disease 12. Which autoimmune condition is characterized by a butterfly-shaped rash on the face? a. Rheumatoid arthritis b. Systemic lupus erythematosus c. Hashimoto's thyroiditis d. Myasthenia gravis
Answer Key: 1. b. 2. b. 3. b. 4. c. 5. c. 6. c. 7. d. 8. a. 9. a. 10. a. 11. a. 12. b.
SAQ Quiz: Common Autoimmune Conditions 1. Describe the pathogenesis of Type 1 diabetes mellitus.
2. Explain the underlying autoimmune mechanism in Myasthenia Gravis.
3. Differentiate between Hashimoto's thyroiditis and Graves' disease in terms of their pathophysiology and clinical presentation.
4. Describe the link between Rheumatic fever and Streptococcal infections.
5. Explain the role of autoantibodies in Rheumatoid Arthritis.
6. Identify common clinical manifestations of Systemic Lupus Erythematosus (SLE).
7. Describe the diagnostic criteria for SLE.
Model Answers: 1. Type 1 diabetes mellitus (T1DM) is an autoimmune disease characterized by the destruction of insulin-producing beta cells in the pancreas. The immune system mistakenly targets these cells, leading to a lack of insulin production and an inability to regulate blood glucose levels effectively. 2. Myasthenia Gravis is an autoimmune neuromuscular disorder in which autoantibodies target the acetylcholine receptors at the neuromuscular junction, leading to impaired nerve-to-muscle signal transmission and muscle weakness. 3. Hashimoto's thyroiditis is an autoimmune disorder characterized by the destruction of thyroid tissue, leading to hypothyroidism. Graves' disease is also an autoimmune thyroid disorder, but it results in the stimulation of thyroid hormone production, leading to hyperthyroidism. 4. Rheumatic fever is an autoimmune reaction that can occur following a Streptococcal infection. Molecular mimicry between Streptococcal antigens and host tissues, such as heart valves, can lead to the immune system mistakenly attacking the host tissue, resulting in inflammation and potential damage to the heart valves. 5. In Rheumatoid Arthritis, autoantibodies such as rheumatoid factor (RF) and anticitrullinated protein antibodies (ACPAs) contribute to the formation of immune complexes, which deposit in the synovium and cause inflammation, leading to joint destruction. 6. Common clinical manifestations of SLE include malar rash, photosensitivity, oral ulcers, arthritis, kidney involvement (nephritis), neurological symptoms (seizures, psychosis), and hematological abnormalities (anemia, thrombocytopenia, leukopenia). 7. The diagnostic criteria for SLE include a combination of clinical and laboratory findings, such as the presence of antinuclear antibodies (ANA), anti-double-stranded DNA (anti-dsDNA) antibodies, and anti-Smith (anti-Sm) antibodies. Diagnosis is typically based on meeting at least four of the American College of Rheumatology (ACR) criteria for SLE.