Inflammation

INFLAMMATION "Inflammation is one of the most important and most useful of our host defense mechanisms, and without an adequate inflammatory response none of us or our patients would be living. It is also one of the most common means whereby our own tissues are injured."

(Slauson and Cooper, 2002) Definition: It is the immediate local vascular and exudative reaction of living tissue against an injurious agent (irritants). It is the reaction of vascularized living tissues to local injury.

The suffix “itis” is usually added to the inflamed organs as tonsil = tonsillitis.

Roles of inflammation:

1-Protection: i-Contain and isolate the injury. ii-Destroy invading organisms and inactive toxins(dilutes, remove or localize).

2-Achieve healing and repair: i-Under ideal conditions the source of the tissue injury is eliminated, the inflammatory response resolves and normal tissue architecture and physiological functions are restored ii- The nature of the acute inflammatory reaction is intense and the affected area is walled-off by the collection of inflammatory cells. This process results in destruction of tissue by products of polymorphonuclear leukocytes and formation of an abscess. iii-Failure to eliminate the pathological insult results in persistence of the inflammatory reaction and spread out in the body. iv-Chronic inflammation often leads to scar formation.

Causes of inflammation: They include A-Endogenous causes: i-immunological reactions (Ag-Ab reaction). ii-some neurological and genetical disorders.

B-Exogenous Causes: I-Non-living irritants: include 1-Physical irritants: as mechanical trauma, cold, heat or radiation.

2-Chemical irritants: as strong or concentrated acids or alkalis.

3-Neutrional irritants: as in vitamin or oxygen deficiencies.

II-Living irritants: include 1-Bacteria 2-Viruses 3-Fungi 4-Parasites They produce their effect either through direct irritation or toxin production.

Remember: The body defense mechanism either: i-Local Body defense (local reaction): inflammation. ii-Systemic body reaction: It is help the local one and include -Humoral defense -Cellular systemic defense (leukocytosis).

-Fever Humoral defense: It is based upon the production of antibodies in the body fluid. It includes agglutinin, lysin, opsonin, precipitin,…

NB: Antigen is a substance (protein in nature or polysaccharides) capable of inducing antibody formation and combined specifically with it.

Haptens (incomplete antigens): It is combined specifically with antibodies; but fails to stimulate their formation.

The response to injury and infection The mechanism for triggering the response the body to injury is extremely sensitive. Three major events occur during this response: 1-An increased blood supply to the tissue ''in danger'': It is performed by vasodilation.

The inflamed tissue looks like containing greater number of blood vessels.

2-Increased capillary permeability: It is caused by retraction of the endothelial cells.

This permits larger molecules than usual to escape from the capillaries, and thus allows the soluble mediators of immunity to reach the site of inflammation.

3-Leukocytes migrate out of the capillaries into the surrounding tissues: In the earliest stages of inflammation, neutrophils are particularly prevalent, but later monocytes and lymphocytes also migrate towards the site of infection.

Cardinal Signs of Acute Inflammation and Its Pathogenesis: 1-Redness (Rubor) 4-Swelling (Tumor or Edema)

2-Hotness (Calor) 3-Pain (Dolar) 5-Loss of Function (Functiolaesa)

1-Redness (Rubor): The inflamed area usually appear red due to a great increase of blood in the inflamed part due to dilation of capillaries and arterioles w opening of all collapsed capillaries.

NB: Dilation of capillaries caused by chemical mediator and dilation of arterioles caused by nerve reflex.

Axon reflex mean that the stimuli pass from sensory nerve–ending up to the bifurcation of the axon then travels in direction apposite to the normal toward the periphery and although these stimuli are traveling along sensory nerve it has the capacity to dilate the arterioles.

Triple response of Lewis: Lewis 1927 proved that the dilation of capillaries caused by chemical mediators and the dilation of arterioles caused by axon reflex.

It occurs when a blunt instrument (a corner of a ruler) is down firmly across the skin of arm and illustrated the vascular change in the acute inflammation. i-A red line appears rapidly in the site of contact. ii-This red line is surrounded by a bright red-halo (flare) of about 3 cm in diameter. iii-The red line becomes pale due to its swelling (wheal). iv-The swelling increases and finally there is a pale wheal surrounded by a wide red flare.

In this experiment, 3 cardinal signs of inflammation (redness, hotness and swelling) are evident.

Chemical Proof: A comparison of the skin of a normal arm with another arm injected with adrenalin (antihistaminic) before experiment by 10 minutes showed only the flare. This is indicating that the red line and wheal are due to dilation of blood capillaries which is caused by histamine (chemical mediators).

Axon-Reflex Proof: If the nerve supply (sensory nerve ending) is cut 6-10 days before the experiment (allow degenerating the nerve fiber), only red line and wheal are developed and the flare is not appeared. This is indicating that the flare is due to dilation of arterioles which is caused by nerve reflex.

Conclusion: -Capillaries dilation is mediated by chemical mediators.

-Dilation of arterioles is mediated by axon reflex.

-Lymphatics are dilated in attempt to drain the exudate.

Wheal: it is the swelling which replaced the red line and it is due to dilation of blood capillaries by the action of chemical mediators.

Flare: It is the inflamed area around the wheal (appeared after a period) due to dilation of the arterioles, which is mediated by axon reflex (bright halo).

2-Hotness (Calor): The inflamed area feels warmer than the adjacent normal area due to: i-Blood from internal organs (warmer) rushes to the inflamed area. ii-High metabolic rate of the inflamed area “as on fire or catching fire".

3-Pain (Dolor): The inflamed area is painful because: i-Pressure on nerve ending by exudate (edema). ii-Liberated chemical mediators from damaging cells e.g. bradykinin the nerve endings. iii-Changes in the pH of the exudate (acidic). iv-Changes in the isotonicity of the fluids (hypertonic).

4-Swelling (Edema or Tumor): The inflamed area is swollen due to: i-Accumulation of exudate in the inflamed area (Exudation). ii-Increase the blood inside the blood vessels (Active local hyperemia).

5-Loss of Function (Functiolaesa): It is due to

sensitizing

i-Pain ii-Edema cause mechanical disability iii- Destruction of tissue iv-Interference with the activity of specific cells as of glandular organs.

Definitions: Edema: Excess fluid in interstitial tissue or body cavity. It may be exudate or transudate.

Exudate: It is an inflammatory extravascular fluid that has a high protein concentration and cellular debris; specific gravity above 1.020.

Exudation: It is extravasation of fluid, proteins, and blood from vessels into the interstitial space or body cavity.

Pus: It is a purulent inflammatory exudate rich in neutrophils and cell debris.

Pus cell: It is dead neutrophils and produce proteolytic enzyme.

Transudate: It is an extravascular fluid with low protein content and specific gravity below 1.012; essentially an ultrafiltrate of blood plasma resulting from increased hydrostatic pressure or decreased osmotic pressure.

The inflammatory process: It is composed of 4 major components: 1-Plasma Proteins: They leaks to the perivascular space at the site of inflammation (swelling) and include: i- Albumin and immunoglobulins ii-Zymogens (inactive proteases) which activated and causing the initiation of complement, fibrinolytic, coagulation and kinine system which are responsible for the inflammatory response. iii-Other protein systems are involved.

2-Fixed Tissue Cells: They include: i-Mast cells. ii-Fibroblasts iii-Endothelium They are very important for initiation and maintaining the inflammatory process through secretion of chemical mediators. They are either the targets of the primary irritant or the most affected by the damage caused to the adjacent cells.

3-Leukocytes and Platelets: They arrive to the site of inflammation by blood. The leukocytes are important to phagocytize and degrade the organisms and debris; meanwhile the platelets do its function within the vascular space through secretion of chemical mediators 4-Mediators of The Inflammatory Reaction: They consist of proteins, acidic lipids and vasoactive amines, secreted by the above mentioned and play an important role in inflammation.

Normal vascular anatomy and fluid exchange A-Normal vascular anatomy The lining endothelium of microcirculation varies in different organs. It can be classified into four types: 1-Continous endothelium: It is found in arteries, arterioles, venules, veins and capillaries in most organs. These types of endothelium are connected to each other through pleomorphic intercellular junction.

2-Fenestrated type:

It is present in capillaries of endocrine and exocrine glands, intestinal mucosa and renal glomeruli. These vessels are fenestrated or opening where the endothelium is entirely missing as in glomerular capillaries or is reduced to a cell membrane.

3-Sinusoidal endothelium: It is found in liver and spleen and is characterized by presence of holes in endothelial cells that permit passing of even large molecule from the vascular lumen.

4-Specialized endothelium: It is presents in postcapillary venules of lymphatic organs. This type is large and columnar.

B-Normal fluid exchange: It occurs via capillaries and under normal circumstances; there is a constant exchange of nutrients (glucose) and cellular by products (Co2) between the blood and interstitium by: 1-Diffusion: The most important means by which the plasma components cross continuous endothelium is by diffusion. The solutes diffuse across the vascular wall from the side of high concentration to the side of low concentration. Lipid soluble materials and water diffuse by direct crossing the lipid bilayer of endothelial well.

2-Pore system: Large non-lipid soluble molecules can’t pass by diffusion and they use the capillary intercellular slits 6-7 nm in diameter or use a system of endothelial pores (pore system).

3-Bulk flow (Bulk transfer): Although more solutes and fluid pass by diffusion there is also important processing with the fluids and solutes pass across the vascular wall due to the difference in hydrostatic pressure inside and outside the wall of vessels.

NB: Starling's law: Under normal conditions, the amount of fluid filtered out the arterial capillaries roughly equals the fluid returned to the various capillaries.

There are 4 forces responsible for this equilibrium: 1-Capillary Hydrostatic Pressure: 2-Hydrostatic Pressure of The Interstitial Space: 3-Plasma Colloid Oncotic Pressure: 4-Interstitial Fluid Colloid Oncotic Pressure: Plasma hydrostatic pressure Tissue hydrostatic pressure Plasma colloidal osmotic pressure Tissue colloidal osmotic pressure Net filtration or absorption*

Arteriolar 30 mm Hg 8 mm Hg 25 mm Hg 10 mm Hg (30-8) - (25-10) = 7 mm Hg

Venular 17 mm Hg 8 mm Hg 25 mm Hg 10 mm Hg (17-8) – (25-10) = -6 mm Hg*

NB: If the fluid leakage is exceed the fluid returned by venules and lymphatic, edema develops.

Cells participating in inflammation Acute Inflammatory Cells 1-Neutrophils 2-Eosinophils Granulocytes 3-Basophils/ mast cell 4-Lymphocytes (Agranulocytes)

Chronic Inflammatory Cells 1-Macrophages and epithelioid cells 2-Giant Cells 3-Plasma cells

I-NEUTROPHILS (polymorphs, Polys, PMN's, Neuts): Characteristics -High motility due to rapid amoeboid movement -Respond to a wide variety of chemotaxic compounds -Phagocytic and bactericidal activities -Neutrophils are the major cellular defense system against bacteria -Are a major part of the innate immune system-first line of defense.

-Crucial to the entire inflammatory process -Neutrophils have surface receptors for complement fragment C3b and Fc portion of immunoglobulin -End cell-don’t divide 2 distinct pools of neutrophils in the blood: 1-Marginating Pool: Neutrophils within blood vessels but lying out of the flow -or"marginated" against the walls.

2-Circulating Pool: Neutrophils in circulation - Circulating and marginating pools are approximately equal in size - Neutrophils in the marginating pool can be mobilized very quickly - Once neutrophils go out of the vasculature they do not return (Live 1-2 days in tissue) 2 major sources of reserve neutrophils are 1-marginating pool 2-bone marrow

Morphology of neutrophils: - 10-12 Âľm in diameter with a multilobed nucleus.

- Contain abundant cytoplasmic granules.

Several (up to 5) classes and subclasses have been identified: 1-Azurophil Granules (primary granules) large, oval and electron dense 2-Specific Granules (secondary granules) smaller, less dense and more numerous 3-Tertiary granules (gelatinase granules) NB: Differentiating neutrophils from eosinophils in rabbits, guinea pigs, rats, reptiles, fish and birds is difficult because the neutrophils have prominent eosinophilic granules and are difficult to differentiate from eosinophils. They tend to be grouped together.

NEUTROPHIL GRANULE CONSTITUENTS Constituents Azurophilic Granules A-Antimicrobial

B-Neutral proteinases C-Acid Hydrolases

1-Myeloperoxidase 2-Lysosomes 3- BPIP 4-Defensins 1-Cathepsin G 2- Elastase 3-Proteinase 3 1-Cathepsins (B and D) 2-β-D-Glucuronidase 3-α-Mannosidase 4-Phospholipase A2

Granules Specific Granules

Small or tertiary (only in human: gelatinase granules)

1-Lysosomes 2-Lactoferrin

1-Collagenase 2-Complement activator

1-Phospholipase A2 Cytoplasmic 1-CR3, CR4 membrane 2-FMLP-receptors receptors 3-Laminin receptors Others Chondroitin-4-sulphate 1-Cytochrom b 2-Monocyte-chemotactic factor 3-Histaminase 4-Vit B12 binding protein BPIP: Bactericidal permeability increasing protein FMLP: N-Formylmethionyl-leucyl-phenylalanine.

1-Gelatinase 2-Plasminogen activator 1-Cathepsins (B and D) 2-β-D-Glucuronidase 3-α-Mannosidase

1-Cytochrom b

Function of Neutrophils in the inflammation:

1-Phagocytosis Ingest, neutralize, and kill/destroy ingested material Killing mechanisms: a. Production of oxygen free radicals b. Hydrogen peroxide c. Lysosomal enzymes

2-Mediate tissue injury: i-Lysosomal enzymes are released into the extracellular space during phagocytosis causing cell injury and matrix degradation ii-Activated leukocytes release reactive oxygen species and products of arachidonic acid metabolism which can injure tissue and endothelial cells iii-These events underlie many human diseases (e.g. Rheumatoid arthritis)

3-Regulate inflammatory response : Via releasing chemical mediators: i-Leukotrienes ii-Platelet activating factor Remark: The neutrophils have surface receptors for: i-Fc receptor and Ab and C3b of complement. ii-Platelet activating factor, receptor. iii-Leukotrine B4, receptor. iv-Leukocyte cell adhesion molecule.

II-EOSINOPHILS: Characteristics 1-Numerous at inflammatory sites which result from Parasites Allergic or Immunologic Disease Some fungi 2-May be present in any exudate (1-5% WBC).

3-Phagocytic but less so than neutrophil 4-Present in tissues in contact with environment Intestine Skin Mucous membranes Lungs 5-Sensitive to corticosteroid therapy Release from bone marrow Cytokines important for production (IL-3, IL-5 and GM-CSF) 6-Ratio of eosinophils Blood: bone marrow: tissue 1: 200: 500 Morphology: -Granules vary in size (dependent upon species), bilobed nucleus in all animals except in rodent (C-shape).

-Granules stain with acid dye eosin - hence their name -Slightly larger than neutrophils (12- 14 Âľm in diameter) -Lysosomal granules contain a wide variety of catalytic enzymes similar to those in neutrophils, except they do not contain lysozyme -Antiparasitic proteins present in granules include i-Major basic protein ii-Eosinophil cationic protein Function i-Work to kill or damage helminths and other pathogens ii-Cause and assist in hypersensitivity reactions (Type I hypersensitivities). iii-Regulator of inflammation - particularly to mast cell products iv-Killing helminths by antibody-dependent cell-mediated cytotoxicity DISTINCTIVE CHARACTERISTICS OF EOSINOPHILS CONSTITUENT OR PRODUCT Major basic protein

Eosinophilic cationic protein

Arylsulfatase Histaminase Phospholipase D

FUNCTION Parasite killing Induces histamine release from mast cells Neutralize heparin from mast cells Parasite killing Shortens coagulation time Alters fibrinolysis Inactivates leukotrienes (LTC4, LTD4, LTE4) Inactivates histamine Inactivates platelet-activating factor

III-BASOPHILS AND MAST CELLS Characteristics: i-Basophils are rare circulating granulocytes ii-Mast cells are found in perivascular sites iii-Both derived from bone marrow iv-Contain abundant cytoplasmic metachromatic granules 1-Metachromatic granules stain pink to blue with toluidine blue.

2-Result of high content of sulphated mucopolysaccharides (heparin). v-Granules also contain histamine, proteases, + potent inflammatory mediators vi-Receptors that bind the Fc portion of IgE antibody vii-Major source of histamine - acute inflammation viii-Produce cytokines (TNF-", IL-1,-3,-4,-6-,-8. IFN) ix-Major cellular mediator of Immediate Hypersensitivity Reactions (Type I) x-Don’t die after release of granules. xi-In birds stimulate the gonadotrophic hormone.

Morphology: Mast cells - round nuclei with abundant cytoplasm filled with granules Found in connective tissue in perivascular spaces Contact with environment - (lung, gut, mm, skin) 2 subtypes 1-Mucosal mast cells: seen in gastrointestinal and respiratory tract 2-Connective tissue mast cells: found in the skin Basophils: -from blood and multilobed or S shape nuclei Are recruited to sites in hypersensitivities

Functions: 1-Intimately involved in acute inflammation Release of histamine smooth muscle contraction and increase vascular permeability.

2-Involved in recruitment of Eosinophils (secrete ECF-A).

Cause other cells to secrete eotaxins 3-Generate Cytokines

IV-MACROPHAGES/ MONOCYTES Characteristics: Macrophages: i-Derived from circulating blood monocyte of bone marrow origin ii-Some originate from immature resident mononuclear phagocytes iii-“Histiocytes” another name for tissue macrophages Monocytes: -Do not have a large reserve pool in the bone marrow -Remain longer in circulation, (24-72 hours) -Are functional cells but require activation to become macrophages secrete various chemical mediators.

-Monocytes migrate into tissues and then are called macrophages.

-Motile - but sluggish -Life span: 30-60 days but can proliferate

Morphology: -Larger (15-20 Âľm) than neutrophils.

-Prominent, usually central nuclei, which may be folded or bean-shaped.

-Contain many lysosomes and have cytoplasmic extensions.

Function: 1-Phagocytosis: i-Antimicrobial and phagocytic (Oxygen radicals) cell. ii-Recruit other leukocytes (secrete several chemokines and cytokines) iii-Stimulate or modulate other cell activity (vascular effects) 2-Secretory function: Macrophages are capable of the production of large number of proinflammatory, procoagulatory and immune regulatory products.

3-Help in repair: i-Clean up or phagocytize necrotic debris in the wound. ii-Simulate the growth of new local vessels (secret growth factors) iii-Induce fibroblasts to migrate, divide and produce collagen. iv-Induce systemic effects.

4-Regulation of granulocyte and monocyte pools: During the inflammatory response or tissue injury, there is increased production of granulocyte and monocytes in the bone morrow. The increased production is controlled by hormonal-like factors secreted by macrophages at the site of tissue injury and via blood reach to the bone marrow stimulating the stem cell to divided and differentiates to mature effectors cells.

NB: These substances known as some of these factors are: i-M-CSF: (macrophage colony stimulating factor). ii-G-CSF: (granulocyte colony stimulating factor). iii-GM-CSF: (macrophage colony stimulating factor).

5- Modulation of tumor cell growth: via production of TNF. 6-Source of multinucleated giant and epithelioid cells Types of giant cells: 1-Inflammatory giant cells.

2-Tumor giant cells.

3-Specific giant cells.

1-Inflammatory Giant cells: These types of cells are produced by fusion of several macrophages together to phagocytize largest particles and they include: A-Langhan’s giant cells: They have many nuclei form wreath at the periphery i.e. arranged around the periphery of the cytoplasm in the form of horse-shoe shape. They usually observed in TB, Actinomycosis and Actinobacillosis.

B-Foreign body giant cells: They have numerous nuclei (50-100) of the same size and shape and distributed haphazardly in the cytoplasm (in the center, at one or both poles). They observed in the presence of foreign material in the tissues as in the cases of silicosis or presence of splinters or thorns or cat gut.

C-Touton giant cells: The cells are two-toned (the nuclei arranged peripherally around central eosinophilic cytoplasm with a rim of foamy cytoplasm peripheral to the nuclei).

NB: The Nuclei arranged as Langhan’s giant cells and they show in areas containing lipids.

2-Tumor Giant cells: The nuclei are relatively few about 8 and of variable size and shape (produced by nuclear division without cytoplasm division). They observed in malignant neoplasms of CT. 3-Specific giant cells: They are pathognomonic for some specific diseases as. i-Aschoff cells of rheumatic fever in the heart. ii-Warthin-Finkeldy giant cells in measles. iii-Spermatid giant cells in testicular degeneration.

NB: Dendritic cells: i-Langerhans cells of epidermis. ii-Follicular cells of nodal and splenic follicles. iii-Interdigitating dendritic cells (in the T-lymphocyte areas of lymph node and spleen).

The relatedness of dendritic cells to other mononuclear phagocytes is based on their ability to function as potent antigen–presenting cells but they are relatively poor at phagocytosis

V-LYMPHOCYTES AND PLASMA CELLS: Characteristics: i-Principally involved in immune reactions -Immediate antibody response.

-Delayed cellular hypersensitivity responses. ii-Less motile than neutrophils and monocytes and non-phagocytic.

Plasma cells produce and release antibody (originate from B cells).

-Produced by lymphoid organs -Migrate to lymphoid tissue (spleen, lymph node) -Recirculate Morphology: Heterogeneous in size (8-10 µm) and morphology There are 2 types (T cells and B cells) T-Lymphocytes: T-cells differentiate in the thymus into 4 subsist 2 regulators T- helper 2 effectors

T- suppressor T- cytotoxic T- delayed hypersensitivity

i-CD4 helper T cells: divided into Th1: regulate the cellular immunity through interleukins and γINF. Th2: stimulate the B cells to differentiate to plasma cells ii-CD8: It either T-cytotoxic: cytotoxic for tumor and infected cells with living organisms.

T-suppressor: suppress the activated T and B cells. iii-Td for delayed hypersensitivity

Mature post thymic T-Cells live for several months they not resident in any one lymphoid organs, but they transverse from one lymphoid organ to another constitute the recirculating lymphocyte pool, however they can found in paracortex of LN and non-follicular region of splenic white pulp. They contained round nucleus and narrow rim of light blue cytoplasm which contain few azurophilic granules.

Functions of T cells: i-T- cell don't respond to free Ag but the Ag must be presented by APCs in context with MHC molecules and these MHC molecules must be recognized as self molecule

by T-cells before the T-cell recognize the Ag. This dual recognition of Ag Only in context with MHC is known as MHC restriction. ii-T-cells are responsible for cellular immunity or cell-mediated immunity as immune response without Ab involvement.

B-lymphocytes: i-Represent 10% of the lymphocytes in the peripheral circulation. ii-Mature B- cells circulate in the blood and lymph vessels W a half – life of 2 days , but Ag primed cells have a longer life span. iii-They can found in: Cortical follicles of L.N. Follicles of Peyer's patches Follicles of splenic white pulp.

Functions of B lymphocytes: i-The mature B-cells has immunoglobulin surface receptors (IgM/IgD), they act as receptors for Ag (MHC-II and complement). ii-Some cells differentiated to plasma cells to produce Ab. iii-Other cells differentiated to memory cells that can survive for months without further antigenic stimulation and on re-exposure to the same Ag. Some of these cells are rapidly producing Ab. iv-Plasma cells and other become memory cells.

Activation of B cells: it is either by 1-T-cell independent mechanism: -It involve antigens that have repeating epitopes as polysaccharides with cross link adjacent surface immunoglobulin on the B-cell, this crass linking signals the B-cell to proliferate and differentiate.

2-T-cell dependent mechanism: -Depend on the help T-cells and involve protein fragment antigens.

-The B-cell recognizes the Ag by its surface Ab internalizes it a process it (mechanism similar done by APCs and presents if on the surface bound to MHC-II Molecules.

-The Ag is then presented to T-cell which becomes activated and produces particular growth factors for the B-cell to divide to make memory cells or causing it to terminally differentiate to plasma cells.

Natural killer cells (NK): 1-It represent heterogeneous group of cells composed of cells from different lineages and they are defined only by their functional attributes not by their histogenesis.

2-They can kill cells targets with out regard to Ag recognition or MHCI expression therefore they are capable of MHC unrestricted cytotoxicity.

3-Large granular lymphocytes (LGLs) represent a subset of NK cells but not all NK cells are LGLs.

4-These cells: i-Don’t express TCR ii-Don't rearrange the genes associated with TCR. iii-May or may not express CD8.

Functions of NK: i-Recognize changes on virus – infected cells and destroy them by an extra cellular killing produce molecule that damage infected cells membrane destruction. ii-Recognize changes in the cell membranes of cancer cells recognize them. iii-Recent observation suggests that NK cells kill cells express low levels at MHCI molecules. iv-TL12 and TNF stimulate NK cells to release interferon, VI-PLATELETS AS INFLAMMATORY CELLS NOTE: In addition to their role in hemostasis and coagulation, platelets are very important in inflammation. Primary hemostasis is a part of the inflammatory response.

Products from activated and/or aggregated platelets: -Fibrinogen -Fibronectin -Coagulation factors VIII and V -Serotonin -Histamine -ADP, ATP -Ca++ cations -Thromboxane A2 -Complement-cleaving proteases -Platelet Activating Factor -Growth factors -P-selectins Contributions to the inflammatory response -Release constituents that increase vascular permeability -Release constituents that may provide local amplification -Release cationic inflammatory mediators -Release enzymes that can directly activate C5 -Chemotactic activity for leukocytes PLATELETS AS INFLAMMATORY CELLS i-Lysosomal-like granules constituents ii-Release action is a secretory degranulation iii-Respond to vascular injury iv-Accumulate in vessels adjacent to inflamed areas v- Interact with immune-complexes as well as microorganisms vi-Initiate intravascular inflammation vii-Enzymes can further damage endothelium viii-Adhesion to subendothelium (collagen)

MAJOR COMPONENTS OF THE INFLAMMATORY RESPONSE: I-Vascular Changes: i- Change in the caliber (diameter) of blood vessels. ii-Changes in the blood flow. iii-Changes in the vascular wall.

II-Cellular Events: i-Margination (from the axial to periphery) as a result of slowing or stasis of blood. ii-Adhesion, pavementation and transmigration to the wall of blood vessels. iii-Emigration and chemotaxis (accumulation of leukocytes at sites of injury)

iv-Phagocytosis and degranulation (activation of inflammatory cells and removal of stimulus).

I-Vascular Changes: i-Changes in the caliber of blood vessels: 1-Transient vasoconstriction: Narrowing of the arterioles immediately after injury results from smooth muscle contraction of the arterioles, which mediated by damaging stimulus. It disappears within 3 to 5 seconds.

2-Long-standing vasodilation: i-The next response is widespread dilation of arterioles and venules due to relaxation of smooth muscles caused by chemical mediators (mostly prostaglandin). ii-The collapsed capillaries are opened and the tissue become hyperemic (Rubor) and warm (Calor). iii-Halo or flare develops and radiate peripherally from the injured site. The cause of this flare results from (axon reflex) which cause dilation of arterioles. It extend throughout the stage of acute inflammation. ii-Changes in the blood flow (blood stream): 1-Acceleration of the blood flow: i-Initially the blood flow very rapidly due to sudden and rapid dilation of blood vessels in the inflamed area. It lasts for minutes or hours depending on the severity and nature of the irritant.

2-Slowing of the blood flow: i-Hemoconcentration (increase blood viscosity) is due to escape of exudate into the inflamed area through the wall of blood vessels. ii-Protruded-swollen endothelium inside the lumen of blood vessels together with increase the capillary bed that resist the blood flow (mechanical resistance). iii-Margination and pavementation of the leukocytes to the inflamed endothelium. iv-The impaired action of plasmatic zone which exchanged position with axial cellular zone. The latter is controlled by “Centripetal force�.

3-Stasis of the blood stream: It is due to thrombosis of the blood vessels (obstruction) at inflamed area. iii-Changes in the vascular wall: A-Vascular endothelium become swollen, rounded and projected into the lumen of bv.

B-Changes in vascular permeability: Increased vascular permeability is one of the clearest changes that occur during inflammation leading to swelling or edema. Five mechanisms of increased vascular permeability are described: 1-Formation of endothelial gaps in venules: (Immediate Transient Response) i-Endothelial cell contraction: Rapid Widening of intercellular junctions (gaps).

Mediators: histamine, bradykinin, leukotrienes.

Binding of mediator to receptor contraction.

Short lived 15 - 30 minutes Reversible Affects only venules (Capillaries and arteries not affected)

ii-Endothelial retraction: Delayed and prolonged Cytoskeletal and junctional reorganization Reversible Structural reorganizing of cytoskeleton - disruption of endothelial junctions Starts 4-6 hours lasts and lasts 24+ hours Mediators: tumor necrosis factor (TNF), interleukin-1 (IL-1), Interferon-gamma (ÎłINF) 2-Direct endothelial injury: (Immediate Sustained Response) Arterioles, venules and capillaries affected Lasts for several hours to days until vascular structures are repaired or thrombosed Causes: Damage directly to endothelium Severe burns or lytic bacterial infections Milder damage-delayed prolonged leakage (2 to 12 hours) Some toxins, thermal injury 3-Leukocyte dependent endothelial injury Cause: leukocytes aggregate and adhere to endothelium Become activated release toxic oxygen species and proteolytic enzymes, which then cause endothelial injury or detachment resulting in increased permeability.

Sites: venules (at neutrophils can adhered).

Time: late response 4-Increased transcytosis i-Transport of fluid through endothelial cells by channels of interconnected, uncoated vesicles and vacuoles (vesiculovacuolar organelles). ii-Certain factors (vascular endothelial growth factor) can increase the number and size of these channels. May be important method used with histamine and other chemical mediators.

5-Leakage from regenerating capillaries Cause: Proliferating endothelial cells are leaky.

Time: Seen in repair process.

Mediators: VEGF (vascular endothelial growth factor).

There are three pattern of vascular leakage i-Immediate transient response occurs due to mild injury and lasts for 30 minutes under the effect of chemical mediators. This response occurs mainly in postcapillary venules due to increase the hydrostatic pressure. ii-Immediate sustained response occurs immediately after severe injuries and lasts for several hours to several days. It involves all vessels leading to increase vascular permeability and the formation of inflammatory exudate. iii-Delayed prolonged response occurs due to mild to moderate injury starting after injury peaking 2 to 6 hours and gradually subsides by 8 hours as in case of sunbathing. The Leakage occurs from venules and capillaries from damaged endothelium.

Chemical mediators of vascular permeability Types of Mediator Vasoactive Amines Plasma kinins Complement Fragments Leukotrienes Prostaglandins

Characteristics Histamine and serotonin - Stored in mast cells, basophils and platelets as granules (Bradykinin principle vasoactive amine) - Generated from plasma precursors by enzymatic cleavage C5a and C3a - Work indirectly by causing WBC’s to release mediators LTC4, LTD4, LTE4 (independent of neutrophils) LTB4 – works dependently via neutrophils PGE2 and PGI2 – vasodilation & potentiates vascular leakage TXA2 – causes vascular leakage

Cytokines Interleukin 1 (IL-1) Derived from WBC’s Tumor necrosis factor (TNF) Induce “Second Phase” Platelet Activating Factor (PAF) Works on endothelium and WBC’s

II-Cellular Events: The movement of leukocytes (primarily neutrophils and monocytes) from peripheral blood to the area of inflammation is one of the most important manifestations of acute inflammation.

The sequence of events in the extravasations of leukocytes from the vascular lumen to the extravascular space can be divided into 4 steps: i-Margination and Rolling: the leukocytes pushed out from the central axial to periphery and come in contact with endothelial lining as a result of slowing or stasis of blood. Rolling of the leukocytes along the vasculature is mediated through transient interactions between selectin proteins and their carbohydrate ligands.

NB: In normal blood vessels the cellular elements of blood are present in a central (axial zone) leaving a cellular cell free area of plasma in contact with vessel wall (peripheral zone). ii-Adhesion, Pavementation andTransmigration: Adhesion and transmigration occur by interaction between complementary adhesion molecules on leukocytes and endothelium.

The mechanisms of adhesion involves both: 1-Endothelial dependent mechanism.

2-Leukocyte dependent mechanism.

1-Endothelial dependent mechanism: -The endothelial cells of postcapillary venules in the site of inflammation become enlarged, plumped and synthesized new receptors (normally absent) under the effect of IL-1 and INF. -These receptor proteins interact with complementary proteins on leukocytes leading to adhesion.

There are 3 classes of adhesion molecules : a-Immunoglobulin superfamily. b-Integrin family c-Selectin family These three classes include many different molecules that are important in cell-to-cell interactions in the immune response, but there are 4 major endothelial adhesion proteins involved in leukocyte-endothelial interactions which are 2 fast acting selectins (E and P) and 2 late acting immunoglobulin (ICAM and VCAM).

I-Endothelial-dependent mechanism: 1-E-selectin: i-It peak 2-4 hrs after exposure to cytokines (IL-1 and TNF–α) and disappear within 12-24 hrs without repeated stimulation. ii-It mediates the adhesion of neutrophils.

2-P-Selectin: i-It found in the cytoplasmic Weibel–Palade bodies of resting endothelial cells and during endothelial activation it redistributed to the endothelial cell membrane within minutes to mediate adherence.

NB: Due to E–selectin and P-selectin, the first cells seen in the inflammatory exudate is neutrophils.

Weibel-Palade bodies: They are rod-shaped intracytoplasmic bundles of microtubules derived from Golgi complex and they are specific for vascular endothelium.

3-ICAM (intercellular adhesion molecule): 4-VCAM (Vascular cell adhesion molecular): i-They appear on the endothelial cell membrane in response to cytokines (as IL-1 and TNF-α) but appear later and persist for longer period of time. ii-ICAM-1 mediates endothelial adhesion with most leukocytes (neutrophils, monocytes and lymphocytes) . iii-VCAM-1 is more important in lymphocytes and monocytes adhesion to endothelium.

II-Leukocyte-dependent mechanism: i-One of which is termed (lymphocyte function-related Antigen-1; LFA-1), which is the leukocyte receptor for endothelial ICAM adhesion protein. So patient with leukocyte adhesion deficiency (LAD) have a mutation in the B2 chain of the LFA-1 molecule, thus fail to localize leukocytes to damage tissue with impaired healing and life-threading inflection.

B1 : VLA Integrins: They include: B2 : LFA B3 : Similar in action to VLA ß1 Integrins: are composed of a group of six adhesion proteins called very late antigen (VIA) protein (so named because the first two proteins isolated from this group). They were induced on lymphocytes, weeks after primary antigenic stimulate VLA-4: is constitutively expressed on resting lymphocyte and monocytes and this protein is the ligand for VCAM-1.

Leukocyte adhesion and Transmigration Endothelial Molecule P-Selectin E-Selectin ICAM-1

Leukocyte Receptor Sialyl-Lewis X PSGL-1 Sialyl-Lewis X

GlyCam-1

CD11/CD16 (integrins) (LFA-1, Mac-1) α4β1 (VLA4) (integrins) α4β7 (LPAM-1) L-Selectin

CD31 (PECAM)

CD31

VCAM-1

Major Role (neutrophils,

Rolling monocytes, lymphocytes.

Rolling, adhesion to activated endothelium (neutrophils, monocytes, T cell).

Adhesion, arrest, transmigration (all leukocytes) Adhesion (eosinophils, monocytes, lymphocytes) Lymphocyte homing to high endothelial venules

iii-Emigration and Chemotaxis into interstitial tissue: A-Emigration: It is the migration of the leukocytes from capillaries and postcapillary venules to the inflamed area. The process starts after adhesion and include: 1-The leukocytes migrate along pores between the endothelial cells to reach the site of injury 2-They forced or insert pseudopodia through the intercellular junction and bulge through and the rest of the cell follows.

3-Then the leukocytes break the basement membrane under the effect of active enzymatic digestion.

4-They crawl over other elements, such as fibrin or tissue cells, toward their destination.

5-RBCs often passive follow the emigrating leukocytes by diapedesis.

NB: This is a passive process (not need energy).

-adherence to endothelium -amoeboid movement -RBCs have not any effect on the inflammatory process.

B-Chemotaxis: It is the force (attractant agent) that attracts leukocytes into the inflamed or damaged.

This process occurs under the effect of attraction factors called chemotactic factors.

There are several endogenous and exogenous chemotactic agents: i-Soluble bacterial products (leukotaxine). ii-Complement component especially C3a and C5a. iii-Arachidonic acid metabolites (lipoxygenase pathway as Leukotrine B4). iv-Cytokines as IL-8 (released from activated neutrophils, macrophages, lymphocytes, mast cells and basophils).

Leukocytes only travel along surfaces (a mostly fibrin) and can't swim in the fluid.

iv-Phagocytosis and degranulation: It is activation of inflammatory cells and removal of stimulus.

The phagocytosis occurs in three steps: 1-Recognition and attachment: The leukocytes are attached to most microorganisms. This process is facilitated by serum protein called opsonin.

2-Engulfment: The foreign particle is engulfed by phagocytic cells forming phagocytic vacuole.

The phagocytic vacuole fuses with lysosome to become a phagolysosome in which the ingested particle is exposed to the lysosomal enzymes. Some of the enzymes kill microorganisms, and others digest the remnants.

3-Microbial killing and degranulation: By phagosome enzymes (hydrogen peroxidase, myeloperoxidase, toxic oxygen based radicals as superoxide) through oxygen dependent or independent mechanism. During phagocytosis, phagocytes show respiratory burst (oxygen consumption) to produce reactive oxygen metabolites (O2 superoxide and H2O2)

to kill phagocytized microorganisms, damage tissue and modulate some cell function.

Exudation and exudates components: I-Fluid (humoral) Exudate.

II-Cellular Exudate.

I-Fluid Exudate: i-The exudates dilute toxic substances formed within the body or introduced from outside. ii-The dilution decrease or abolish the damaging effect of the irritant. iii-Exudates carry all plasma proteins including fibrinogen and Igs. (antibodies). iv-The exudates carry leukocytes. v-The exudates bring all the components of the plasma enzyme system to initiate, control and resolve the inflammatory process.

The enzyme system in the exudate are:

1-Clotting (coagulation) cascade: NB: Cascade means step-by-step sequence.

The clotting cascade may be initiated by activation of either: i-Intrinsic pathway: It is initiated by activation of Hageman factors (factor XII) by contact of the XII with negatively charged surfaces as vascular wall denuded from endothelium. ii-Extrinsic pathway: It is initiated by activation of factor (VII) stable factor by thromboplastin (tissue factor).

NB: Thromboplastin is hydrophobic protein manufactured by normal and activated macrophages, endothelium, fibroblasts and other fixed cells.

Both pathways converge at the activation of factor X which ultimately results in production of thrombin and conversion of fibrinogen to fibrin. i-Fibrinogen is important for clot formation and the prevention of further loss of blood. ii-Fibrin is very important in the inflammatory process due to : 1-Provid essential matrix for the chemotactic migration of leukocytes into the inflamed area because leukocytes can not swim in a pool of liquid plasma i.e. fibrin gel provides a substrate for leukocyte migration (surface).

2-Provides a scaffold for granulation tissue formation and new capillaries in repair.

3-Act as physical barrier to confined the irritants and its spread to the adjacent tissue.

4-Important for phagocytosis.

II-The kinin system: -The Hageman factor (XII) is activated by prekallikrein and high molecular weight kininogen (HMWK) in the intrinsic coagulation cascade and the prekallikrein is activated to kallikrein which digests kininogen plasma protein zymogen to generate the vasoactive peptide bradykinin.

-The prekallikrein and HMW kininogen circulate as a biomolecular complex.

NB: Kallikrein can initiate the conversion of C5 to C4a.

Function of the Bradykinin: i-Increase the vascular permeability by inducing endothelial contraction and widening of endothelial-gap junctions. ii-Causes vasodilation, thus amplifying the increased vascular permeability.

iii-Activates phospholipase A2 which liberates arachidonic acid and AA-metabolites that have powerful vasopermeability effects. iv-Induces local pain.

III-Fibrinolytic system: The fibrinolytic system removes the fibrin of clot by 3 ways: 1-Direct degradation of the fibrin by leukocytic fibrinolytic enzymes released from living and dead leukocytes in the area of inflammation.

2-Direct phagocytosis of fibrin by phagocytic cells especially macrophages.

3-Dissolution of the fibrin by activation of plasmin that is the most important plasma degrades fibrin into fibrin-split products, which are soluble and removed via lymphatics.

4-These fibrin-split products are chemotactic for neutrophils.

NB: Plasmin is derived from plasma zymogen plasminogen this conversion can by initiated by: -Activated Hageman factor -WHMWK -Prekallikrein -Plasminogen activator as: -Urokinase–like plasminogen activator (UPA): It is found in plasma.

-Tissue plasminogen activator (TPA): It made by endothelium and macrophages.

-Plasmin can directly initiate the conversion of HMWK to bradykinin which has powerful vasoactive and proinflammatory functions.

Plasmin activates C3 to form C3a and Cab. If the fibrinolytic system not controlled, uncontrollable hemorrhage occur.

IV-The complement cascade: Definition: The complement is a complex system containing more than 30 various glycoproteins in low concentration in normal serum in the form of components, factors, regulators or receptors. It presents in an inactive form but is activated to form an enzyme cascade and is not increased in the serum after immunization.

There are 3 pathways of complement activation: i-Classical Pathway: is activated by immune complex. ii-Lectin Pathway: is activated by carbohydrate. iii-Alternative Pathway: is activated by other substances, mainly of bacterial origin.

Classical Pathway Immune complexes C1q C1r C1s C4 C2

Lectin Pathway

Alternative Pathway

Carbohydrate Collections MBP

Activating Surfaces

MASP C4 C2

C3b

C1r C1s C4 C2

P D B

C3 C3b

C5b678(9)n

(MAC)

MBP: mannan-binding protein; MASP: MBP-associated serine protease; B: factor B; D: factor D; P: properdin; MAC: membrane attack complex: lysis bacteria, parasites and foreign cells)

Biological effects of complement activation: 1-Cytolysis: It means destruction of target cells by lysis of the cell membrane: i-Cytoxicity in case of nucleated cells. ii-Hemolysis in case of RBCs iii-Bacteriolysis in case of bacteria.

The cytolysis is due to the formation of MAC (56789). MAC is hydrophobic in nature.

2-Anaphylaxis: -C3, C4 and C5 peptides termed anaphylatoxins. They responsible for degranulation of mast cell and release of histamine which increase vascular permeability and cause smooth muscle contraction.

3-Chemotaxis: -C5a acts as chemotactic for neutrophils -C3b acts as an opsonin promoting phagocytosis of C3b-coated material by way of C3b receptors on macrophages, neutrophils and eosinophils.

NB: The complement system is not entirely autonomous because other enzymes the fibrinolytic and kinin systems can activate complement components by themselves.

Kallikrein can initiate the conversion of C5 to C5a plasmin can activate C3 to C3a and C3b.

Mediators of Inflammation Mediators: They are substances that direct the vascular and cellular event in inflammation.

They can originate from the damaged fixed cells at the site of inflammation or from the migrating cells under the effect four plasma enzyme systems collectively or individually.

They can be divided into 6 classes: 1-Vasoactive Amines.

2-Granular constituents other than vasoactive amines .

3-Arachidonic acid metabolites (lipid mediators).

4-Platelet Activating Factor (PAF).

5-Oxidizing reagents.

6-Cytokines.

1-Vasoactive Amines: The vasoactive amines are mediators that are preformed and stored in the granules of mast cells, basophils, eosinophils and platelets. They include: i-Histamine: It is the prototypic vasoactive amine fund in the granules of mast cells, basophils, eosinophils and platelets. ii-Serotonin: It is found in the mast cells and platelets. It is more important in rodents.

Functions: -Histamine causes vasodilation, increase the vascular permeability and smooth muscle contraction. The principal mechanism of its release is by formation of immune complex on the mast cells (Type I hypersensitivity).

-Serotonin has the same effect of histamine.

2-Granular constituents other than vasoactive amines: i-Mast cells: Mast cells contain preformed compounds contribute to the immediate response associated with degranulation including: Proteases as tryptase and chymase that digest the basement membranes of B.Vs. increasing the vascular permeability.

Proteoglyceans as heparin and chondroitin sulfate which serve to stabilize and protect proteases from antiproteases.

Chemotactic factors as (ECF-A) eosinophil chemotactic factor of anaphylaxis which attract eosinophils, and neutrophil chemotactic factor for attraction of neutrophils. ii-Granulocytes and macrophages: Granulocytes and macrophages contain lysosomal granules that fuse with the phagocytic vacuoles to form phago-lysosomes releasing proteases and enzymes to kill bacteria, fungi and protozoa.

If these contents released extracellular they create tissue damage and contribute to the initiation and evolution of the inflammatory response.

NB: Small quantities of the lysosomal constituents are released during phagocytosis and large quantities after dying and lysis of cells.

3-Arachidonic acid metabolites (lipid mediators) The major constituents of cell membranes are phospholipids. Cellular phospholipases, especially phospholipase A2 and C are activated during inflammation and degrade phospholipids to arachidonic acid. The arachidonic acid has a short half-life and can be metabolized by two major routes: i-Cyclo-oxygenase Pathway: It produces prostaglandins, prostacyclin, and thromboxanes. ii-Lipoxygenase pathway: It produces leukotrienes and lipoxins.

Phospholipids in cell membrane

Phospholipase A2 and C Arachidonic acid

Cyclo-oxygenase TXB2

TXA2

PGG2

Lipoxygenase 15-lipoxygenase

PGI2

Thromboxanes Prostacyclin PGH2

5-lipoxygenase 5-HPETE, 5-HETE

15-HPETE

Leukotrienes (LT-ABCDEF) Slow reacting substances of anaphylaxis

PGD2

PGE2

PGF2

Prostaglandins

LXA4

LXB4 (Lipoxins)

HPETE: hydroperoxy-eicosatetraenoic acid.

HETE: hydroxy-eicosatetraenoic acid.

Functions of arachidonic acid metabolites: A-Leukotrienes: They have potent effects on many different cells, including endothelium and leukocytes: LTC4, LTD4 and LTE4 are known as slow-reacting substances of anaphylaxis (SRS- A) that has characteristic effects of immediate hypersensitivity reactions and are much more potent than histamine: i-Induced smooth muscle contraction and bronchospasm. ii-Increased vascular permeability by endothelial contraction. iii-Vasoconstriction, platelets aggregation and neutrophils adherence to endothelium. iv-LTB4 stimulates chemotaxis, phagocytosis, degranulation and leukocyte adhesion.

B-Lipoxins: They stimulate granulocytes and cause chemotaxis as LTB4 but have no effect on the vascular permeability and the leukocyte adhesion to endothelium.

C-Prostaglandins: They induce: i-Vasodilatation ii-Inhibit platelet aggregation and suppress neutrophil adherence to endothelium.

NB: Thromboxane is produced by monocytes and macrophages as well as activated platelets. It causes platelet to aggregate, vasoconstriction, and constriction of airways.

4-Platelet Activating Factor (PAF): It is a lipid mediator, which produced by stimulated neutrophils, monocytes, macrophages, lymphocytes, basophils, mast cells, endothelial cells and platelets.

It has proinflammatory effects including: i-Vasodilation ii-increase vascular permeability iii-Chemotaxis iv-Stimulation of granulocytes v-Platelets aggregation vi-Induction of local inflammatory cells to produce other mediators.

5-Oxidizing reagents: During phagocytosis, neutrophils and macrophages are stimulated to produce a number of oxygen metabolites (reactive oxygen) which is released into the surrounding tissues creating tissue damage and progression of the inflammatory response.

6-Cytokines: Definition: They are polypeptides that provide the necessary means for cell to

communicate with one another. They link between many different cells produced by stimulated cells to the extracellular environment to influence the same cells acutocrine or neighboring cells paracrine or exert systemic effect.

Types of Cytokines: i-Interleukins (IL). ii-Interferons (IFN). iii-Chemokines. iv-Growth Factors (GF). v-Colony stimulating Factor (CSF).

NB: -Cytokines may be called immunocytokines or interleukins.

-They comprise interleukins, initially through to be produced by leukocytes (lymphokines) through to be produced by lymphocytes (monkines) through to be produced by monocytes, interferon, colony stimulating factors and others chemokines.

-Cytokines share certain characteristics: -Usually synthesized by a cell in response to a stimulus and once produced are secreted, they aren’t stored performed within cells.

-The same cytokine is produced by various cell types and the individual cytokine act on many different types pleiotropic and may affect various cells in different ways.

-Many similar functions are shared by different cytokines i.e. their actions are abundant.

-Cytokines often influence the synthesis of and affect the actions of other cytokines.

-Cytokine actions mediated by binding to specific receptors on target cells. They tend to be very potent -ILI, TNF and interferon involved in innate immunity and others involved in acquired immunity i.e. act to control the activation growth and differentiation of immune cells.

Functions of cytokines: i-They play a crucial roles in immunity, inflammation and hematopoiesis. ii-They affect on the nature of inflammatory response by activation of number of cells either fixed as endothelium or migratory cells (leukocytes). iii-The most important cytokines involved in the inflammation are IL-1 and TNF-α which produced by activated macrophages and IFN-γ and TNF-α which produced by activated lymphocytes. They activate fixed cells (endothelium) to secrete adhesion molecules and other inflammatory cells.

NB: Activation means quantitative changes in the level of expression of specific gene products (proteins) to perform new functions.

Cytokines activate the endothelial cells: Endothelial cells respond to cytokine activation signals by: i-Hyertrophy (becoming more plump) and the generation of E- selection, ICAM-1 and VCAM -1 adhesion molecules to mediate leukocytes adhesion to the endothelial surface which followed by emigration. ii-Increase its expression of MHC class I and II to facilitate the recognition of antigens between immune cells. iii-Becomes more thrombogenic i.e. clotting become more easily induced through: a-Increase production of thromboplastin (tissue factor) which activates the extrinsic coagulation cascade. b-Decrease production inactivates thrombin on the endothelial surface. iv-Produce their own cytokines especially IL-1 (which is essential in activation and clonal expansion of antigen primed lymphocytes) in response to specific cytokines as TNF–α and IFN- ß.

Cytokines activate leukocytes to: 1-Produce more LFA-1 molecules in their cell membrane to attach more efficiently the ICAM-1 expressing endothelium.

2-Reach their full functional potential e.g.: i-IL-1 activate lymphocytes proliferate and differentiate to effectors cells in response to Ag.

ii-IFN-γ help macrophages and IFN- α help neutrophils to phagocytize and kill foreign organisms much more efficiently. iii-Cytokine-primed macrophages and neutrophils increase their biosynthesis and / or release of lysosomal enzymes granule contents (neutrophil) cytokines and reactive O2 intermediates.

3-Cytokines increase the intracellular calcium in leukocytes which activate cellular phospholipase A2 to liberate AA. from the cell.

Cytokine influence the fixed structural cells to: -Increase healing and repair e.g. cytokines induce fibroblasts to divide and produce more collagen and proteolytic enzymes.

Cytokines have endocrine effect which induce systemic signs of inflammation: This effect is defined collectively as the acute-phase response which has 5 components: 1-Fever: It is elevation of the body temperature above the normal limit that caused by exogenous pyrogens of bacterial or fungal origin. The bacterial pyrogens cause disintegration of tissue and leukocytes which release endogenous pyrogens (IL1, IL6, cachectin and TNF-α) stimulate thermoregulatory center in the hypothalamus to decrease cutaneous blood flow and heat dissipation Fever.

Function of Fever: i-It has bacteriostatic and bactericidal effects. ii-In viruses: stimulate the cells to produce the interferon. iii-It enhances the phagocytosis. iv-It stimulates the cells to produce antibodies.

2-Hepatocyte acute–phase protein production: The liver is stimulated to produce a number of proteins including: Group A-Positive Acute-Phase Reactants (APRs) i-Major APRs ii-Complement Proteins iii-Coagulation Proteins iv-Proteinase inhibitors v-Metal-binding Proteins vi-Other Proteins

B-Negative APRs

Individual Proteins -Serum amyloid A, CRP, Serum amyloid P component.

-C2, C3, C4, C5, C9, B, C1-inhibitor and C4 binding protein -Fibrinogen, von Willebrand factor.

-Antitrypsin, Antichymotrypsin, Antiplasmin, heparin cofactor II, Plasminogen activator inhibitor I. -Haptoglobin, hemopexin, Ceruloplasmin, Manganese superoxide dismutase.

-Acid glycoprotein, heme oxygenase, Lipoprotein, leukocyte protein I, Lipopolysaccharide-binding protein, Mannosebinding protein.

-Albumin, Pre-albumin, Transferrin, ..

3-Leukocytosis: Definition: It is an increase of the leukocytes. It is usually associated with pyogenic bacteria, toxemia and severe hemorrhages.

4-Increases in plasma copper and decreases in plasma iron and zinc:

These changes can be considered unique protective host mechanisms because it has been shown that the host and the invading microorganisms are in competition for iron and zinc.

While, the copper is required for upper immune functioning and increase in copper is secondary to increase in plasma concentration of copper binding protein (ceruloplasmin).

5-Catabolic processes: If the acute-phase response is long lasting chronic inflammation, it leads to catabolism in the form of muscle wasting, weight loss and weakness.

TNF-Îą (cachectin) suppress synthesis of lipoprotein lipase which is required for the utilization of serum triglycerides so they can't utilize leading to empyema and weight loss. IL1, has similar but minor effect.

CLASSIFICATION OF INFLAMMATION Purpose: Using specific criteria, it is possible to provide a brief description evaluation, also known as morphologic diagnosis, for each type of inflammatory response.

Duration Peracute Acute Subacute Chronic Chronic active

Extent Mild Moderate Severe

Distribution Focal Multifocal Locally extensive Diffuse

Exudate Serous Catarrhal Fibrinous Suppurative hemorrhagic Lymphocytic Allergic

Anatomic modifiers Interstitial Parenchymatous i-Glomerulonephritis ii-Bronchopneumonia

Organs Nephritis Hepatitis Splenitis ect

DURATION: How long has the process been underway?

Determination of duration can also be very subjective and the morphologic changes associated with an inflammatory process may not correlate with the onset of clinical signs. For example, due to the high functional reserve of the liver and kidney it is common to find severe chronic lesions in these organs in animals that die suddenly. i-PERACUTE INFLAMMATION: Definition: very acute.

Usually caused by a potent stimulus.

Usually the animal has no time to respond morphologically to a disease process.

Less common than acute disease processes General Features: (eg: bee sting) Time: 0-4 hours Vascular involvement: hyperemia, slight edema, hemorrhage Inflammatory cells: not usually numerous, few leukocytes Clinical signs: shock, sudden death ii-ACUTE INFLAMMATION: Definition: having a short and relatively severe course.

Time: It begins within 4-6 hours can last for 3-5 days Vascular involvement: -Local active hyperemia, -Edema (due to endothelial damage) -Occasional fibrin thrombi within vessels.

Inflammatory cells: Leukocyte infiltration is variable.

In general, neutrophils, eosinophils and lymphocytes are present.

Clinical signs: Most associated to the vascular changes: warm, red, swollen, painful, loss of function.

Lymphatics: Lymphatic vessels have a role in moving away the exudate. The transportation of the exudate (i.e., inflammatory cells and necrotic debris) can lead to acute regional lymphadenitis and lymphangitis. iii-SUBACUTE INFLAMMATION: Definition: Transition period separating acute and chronic inflammation. Evidence of hyperemia and edema is regressing but evidence of repair such as fibroplasia and angiogenesis is lacking.

Time: varies from a few days to a few weeks.

Vascular involvement: There is a decline in the magnitude of vascular changes, compared to acute inflammation (less hemorrhage, hyperemia and edema).

Inflammatory cells: characterized by a “mixed inflammatory infiltrates�.

Lymphatics: lymphatic drainage endothelial damage repaired iv-CHRONIC INFLAMMATION: Definition: Inflammation which persists over a period of time.

Features: -Chronic inflammation is often the result of a persistent inflammatory stimulus in which the host has failed to completely eliminate the causative agent.

-Inflammatory response usually is accompanied by an immune response.

-Chronic inflammation is characterized by evidence of host tissue response in terms of repair -Formation of scar and regeneration of damaged tissue Histology: mononuclear inflammatory cells, fibroblasts and collagen with proliferating vasculature.

Cause: May follow an acute inflammatory phase. May develop as an insidious, lowgrade, subclinical process without history of a prior acute episode.

Time: Variable Vascular involvement: Proliferations of capillaries and small blood vessel (angiogenesis/ neovascularization) resulting in edema, hemorrhage and congestion.

Host involvement: Parenchymal regeneration or repair by fibrosis (scarring).

Inflammatory cells: Macrophages, epithelioid and giant cells besides plasma cells and fibroblasts Lymphatics: involvement variable +/- proliferation and activation.

Clinical Signs: Primary dependent upon duration of the illness and inflammatory lesions.

NB: Many changes represented in chronic inflammation are also seen in areas of repair.

EXTENT/SEVERITY: The severity of the process must be evaluated. However, it is important to recognize that determining the degree of severity is often very subjective.

Extent of injury Mild Moderate Severe

Tissue damage Absent - minimal Some present Substantial

Inflammatory cells Few Evident Abundant

Vascular Involvement Slight Moderate edema and Hgs. Massive edema and Hgs.

NB: In addition to mild, moderate, severe; other modifiers can also be used, as minimal, extensive, etc.

DISTRIBUTION: What is the location of the lesion within an organ? i-FOCAL: Definition: Single abnormality or inflamed area within a tissue.

Size: Varies from 1 mm to several centimeters in diameter ii-MULTIFOCAL: Definition: Arising from many foci (several foci separated from one another).

Size: Variable.

NB: Each focus of inflammation is separated from other inflamed foci by an intervening zone of relatively normal tissue.

iii-LOCALLY EXTENSIVE ( Focally extensive): Definition: Involvement of considerable area within an organ.

Possible origin: 1-Severe local reactions that spread into adjacent tissue 2-Coalescence of foci in a multifocal reaction Example: -Pulmonary lesion of pneumonic Mannheimiosis in cattle.

-The cranioventral aspects of the lungs are involved while the dorsal portions usually are spared. iv-DIFFUSE: -Involve all the tissue or organ in which the inflammation is present.

-Variations in severity may exist.

Example: Interstitial pneumonia. Diffuse lesions are often viral or toxic in etiology.

Acute Inflammation The acute inflammation is characterized by: I-Macroscopically: swollen (thickened) and congested affected tissue.

II-Microscopically: dilated blood vessels, leukocytic infiltration and plasma leakage.

Classification of the inflammation according to the predominant constituents of the exudate: 1-Serous inflammation Mild Inflammation 2-Catarrhal inflammation 3-Fibrinous inflammation 4-Suppurative inflammation 5-Hemorrhagic inflammation 6-Lymphocytic inflammation

Severe Inflammation

Moderate Inflammation 7-Allergic inflammation

Serous Inflammation Definition: It is a mild inflammation of serous and mucous membranes, where the predominant constituent of exudate is albumin (serous fluid).

Occurrence: It occurs within organs or on surfaces as in case of: i-Serous pneumonia, lymphadenitis,. ii-Serous rhinitis, gastritis.. iii-Serous pleuritis, peritonitis, Causes: Mild irritants such as sun-rays, blisters on skin, burns,

Macroscopic Pictures: i-The affected area is swollen and congested (red) Cardinal Signs. ii-Cut sections oozed watery fluid (lymph). iii-the serous membranes lose their shiny appearance because the inflammatory cells and few fibrin threads may adhere to it.

Microscopic Pictures: i-Dilated blood vessels (Active hyperemia). ii-Leukocytic infiltrations. iii-Fine granular or homogenous eosinophilic material within the tissue spaces (albumin).

Significance: i-It indicates that the cause is mild and the prognosis is favorable if the cause removed. ii-If the cause is not removed change into another type. iii-The exudate either absorbed or become organized by fibrous tissue.

Catarrhal Inflammation Mucous Inflammation Cellular Inflammation Definition: It is a relatively mild inflammation of mucous membranes where the predominant constituent of exudate is mucus (mucin in water).

Occurrence: It occurs on the mucous membrane of tubular respiratory, reproductive and digestive tracts, where the goblet cells are numerous as catarrhal rhinitis, laryngitis, tracheitis, enteritis, gastritis, endometritis, cystitis, ‌.

Causes: Mild irritants such as i-Chemicals as formaldehyde and cresol in high concentration. ii-Inhaled dusts, cold air or foreign proteins. iii-Infection as in some viral and bacterial diseases. iv-Ingestion of spoiled or moldy or irritating food.

Macroscopic Pictures: i-The affected m.m. are swollen and congested (red) Cardinal Signs. ii-Clear transparent or gray, yellow opaque material is sticky on hyperemic m.m.

Microscopic Pictures: i-Dilated blood vessels (Active hyperemia). ii-Leukocytic infiltrations. iii-Hyperplasia and desquamation of the lining epithelium in the lumen. iv-Numerous columnar epithelium changed into goblet cells (metaplasia). v-Homogenous basophilic material (mucus) in the lumen. vi-The mucus is stained red by mucicarmine stain.

NB: Sloughing: It is a loss or separation of mass of tissue as testis or ear concha.

Desquamation: It is a loss or separation of sheet of the lining epithelium from its m.m.

Significance: i-It indicates that the cause is mild and the prognosis is good if the cause removed. ii-If the cause persists for a long period, it change into another type.

Fibrinous Inflammation Definition: It is a severe inflammation where the predominant constituent of the exudate is fibrin.

Occurrence: It occurs on the serosal and mucosal surfaces and is predominant on the intestinal mucosa, peritoneum, pleura, synovial membrane, and meninges and in the lungs.

Causes: It is so severe cause to be escape of fibrinogen (largest molecule of plasma protein) through the wall of blood vessels. i-Viral diseases as in feline enteritis. ii-Bacterial diseases as in salmonellosis and necrobacillosis. iii-Inhalation of hot gases during barn fires.

Macroscopic Pictures: i-The affected m.m. appear opaque dull and covered with whitish fuzzy material. ii-The early lesion on a serosal surface gives a roughened ground-glass appearance. It is easily overlooked. iii-When it present in large quantities, it takes “a bread and butter� appearance. iv-The affected membrane is congested (when remove the fibrin membrane).

The fibrin membrane (pseudomembrane) is 2 types: i-Croupous membrane: It is one type of pseudomembrane can be removed from the affected surface without causing to the surface (there is no necrosis). ii-Diphtheritic membrane: It is one type of pseudomembrane when be removed leave the affected surface eroded and damaged (there is coagulative necrosis).

Microscopic Pictures: i-Dilated blood vessels (Active hyperemia). ii-Leukocytic infiltrations. iii-Pink fibrin network adhered to the affected surface, entrapped the leukocytes. iv-Coagulative necrosis is only seen with diphtheritic type.

Significance: i-The fibrinous inflammation indicates severe cause. ii-The fibrin act as physical barrier to confined the irritants and prevent its spreading by occlusion of blood vessels and lymphatics. iii-The fibrin helps the phagocytosis and healing. iv-The fibrinous exudate is either absorbed, sloughed or organized by fibrous tissue. a-permanent adhesions in serous membrane as in case of.

Pericardium heart block.

Pleura suffocation.

Peritoneum adhesions between different organs leading to impair intestinal motility and the circulation of the area b-The organized portion of the lung becomes permanently converted into fibrous tissue (lung carnification=fleshy).

Suppurative Inflammation Purulent Inflammation Definition: It is a severe inflammation where the predominant constituent of exudate is “neutrophils”. It occurs in all body tissue.

Causes: i-Pyogenic bacteria as staph, strept, coryne (pyo=pus * genic-produce). ii-Some chemicals as turpentine oil (if injected in tissue).

Macroscopic Pictures: i-The affected area show swelling and redness Cardinal Signs. ii-Cut section oozed pus with different colors and consistency.

A-Color: according to species of bacteria. o Staph and strept white to yellow pus. o Corynebacterium greenish pus. o Presence of RBCs red pus. o Saprophytic (produce H2S) turn the pus into black (hoof injury).

B-Consistency: according to animal species and neutrophil-lymphocyte ratio.

Animal species Dog Cat Horse Bovine Chickens

Neutrophil-lymphocyte ratio 3.5 : 1 2:1 1.5 : 1 0.5 : 1 No neutrophils (heterophils)

Consistency of pus Thin and watery Liquid Slightly viscid Viscid Dry and caseous

NB: presence of large number of neutrophils means rich in the proteolytic enzyme that liquefy the tissue into pus (watery); while the decreased numbers (poor in the proteolytic enzyme) the liquefaction is not efficient to become watery where the consistency is viscid.

In birds: The pus is dry and caseous due to presence of “antitryptic enzyme”. The neutrophil is called heterophil so there is suppurative inflammation and no liquefactive necrosis.

Microscopic Pictures: i-Dilated blood vessels (Active hyperemia). ii-Considerable numbers of neutrophils infiltrations (living or dead). iii-Homogenous basophilic material (pus) is seen. iv-Line of defense (pyogenic membrane) separate the inflamed tissue from the adjacent.

It consist of dilated capillaries, fibrin threads and leukocytes infiltrations. v-Few numbers of lymphocytes, macrophages and plasma cells may be seen.

NB: The pus consists of i-Living neutrophils. ii-Dead neutrophils. i-Liquefied necrotic tissue. iii-The causative agents (bacteria).

Significance and Results: i-The suppurative inflammation indicates presence of pyogenic bacteria. ii-Pus is healthy signs. iii-Pyemia and death or localized as abscess surrounded by fibrous tissue capsule. iv-Abscess may become sterile where the body defenses may kill all the causative agents and the pus slowly absorbed or organized.

Types of Suppurative inflammation:

Abscess: It is a local suppurative inflammation. It has different names according to its sites.

Pustule: It is a small abscess in the malpighian layer of the epidermis.

Furuncle or Boil: It is a small abscess in the hair follicle or sebaceous gland.

Carbuncle: It is a subcutaneous abscess with several opening to the surface of the skin (sinus).

Pyorrhea: It is a deep suppurative inflammation of the gum.

Empyema: It is an accumulation of pus in the body cavity.

Phlegmon or Cellulitis: It is acute diffuse suppurative inflammation in subcutaneous loose connective tissue. It is caused by Streptococcus hemolyticum which produces: a-Streptokinase (fibrinolysin): dissolve and prevent fibrin formation. b-Hyaluronidase: break tissue cement substance helping spread of bacteria and its toxins.

Ulcer: It is discontinuation of the epithelial lining, where the base lies in the lamina propria (lining epithelium) or the dermis (covering epithelium).

Erosion: It is loss of the superficial layer of the epithelium with intact basement membrane.

Sinus: It is the formation of tract lined by FCT connects between cavity and surface.

Fistula: It is a tract between 2 cavities.

Cold Abscess: It is a chronic abscess in the internal organs as liver and lungs.

NB: Pathogenesis of Abscess Formation: i-The pyogenic microorganisms produce toxin which induce coagulative necrosis. ii-The damaged tissue produce chemical mediators (leukotaxine) chemotaxis to neutrophils. iii-Many neutrophils died during the process (pus cells) proteolytic enzymes which liquefy the damaged tissue and fibrin threads (liquefactive necrosis). iv-The resulting fluid is mixed with the other products of the inflammatory process forming the pus. v-The adjacent tissue (peripheral zone of the inflamed tissue) called pyogenic membrane which consists of dilated capillaries, fibrin and leukocytes neutrophils lymphocyte and macrophages.

Hemorrhagic Inflammation Definition: It is a severe inflammation, where the predominant constituent of exudate is erythrocytes.

Causes: the injurious agents are usually severe as i-Bacterial or viral diseases as in blackleg, anthrax, pasteurellosis, cattle plague. ii-Chemicals as phenol, arsenic, chloroform and phosphorus.

Macroscopic Pictures: i-Swelling and redness (cardinal signs). ii-The exudate is red due to presence of RBCs. iii-In the stomach, the blood becomes black where the Hb is changed into acid hematin (derived from oxidized Hb).

Microscopic Pictures: i-Dilated blood vessels (Active hyperemia). ii-Leukocytic infiltrations. iii-The RBCs are the main constituent of exudate.

Significance: i-The hemorrhagic inflammation indicates severe cause and bad prognosis. ii-The animal is died due to anemia and extensive tissue damage. iii-Recovery is usually delayed.

Lymphocytic Inflammation Definition: it is a special type of inflammation where the predominant constituent of exudate is lymphocytes and characterized by absence of cardinal signs of inflammation.

Causes: Cellular exudate (lymphocytes). i-Viral infections. ii-Toxins. iii-Protozoal infection.

Macroscopic Pictures: i-Absence of cardinal signs of inflammation. ii-Grayish-white spots of irregular shape on the surface of the affected organs. iii-This type of inflammation mostly seen in parenchymatous organs and brain.

Microscopic Pictures: i-The dilated blood vessels are absent (not clear). ii-The exudate is highly cellular (lymphocytes and may few macrophages). iii-In the brain: the lymphocytes usually accumulate in the Virchow-Robin spaces forming “perivascular lymphocytic cuffing).

Significance: i-The indicates viral disease, toxemia or protozoa. ii- If the cause is removed the healing occur rapidly.

NB: Grayish-white nodules in the liver of birds are due to one of the following: 1-Leukosis 2-Asperigellosis 3-Histomoniasis 4-TB.

Allergic or Eosinophilic Inflammation Definition: it is a special type of inflammation where the predominant constituent of exudate is eosinophils and usually associated with any types of inflammation (fibrinous, catarrhal,).

Causes: Cellular exudate (lymphocytes). i-Metazoan parasitism. ii-Hypersensitivity (allergy). iii-Sodium chloride toxicosis.

Macroscopic Pictures: It is associated with any type of inflammation. i-Cardinal signs of inflammation. ii-The exudate may be serous, fibrinous, hemorrhagic, suppurative.

Microscopic Pictures: i-Dilated blood vessels. ii-The cellular exudate is mainly eosinophils besides other inflammatory cells.

Significance: i-It depends on the cause allergy is severe while parasites are milder. ii-If the cause is removed recovery occur. iii-Shock and death may occur due to excess histamine.

NB: Alterative inflammation: The term alterative refers to the retrogressive alterations e.g. cloudy swelling, fatty change and necrosis induced in cells with injurious agents which under other circumstances cause inflammation.

Chronic Inflammation Proliferative or Productive Inflammation Definition: It is an inflammation of prolonged duration in which the body responds by producing excessive amount of:

i-Connective tissue. ii-Reticuloendothelial tissue. iii-Epithelium tissue.

Causes: i-Follow the acute inflammation when the tissue destruction is extensive or the bacteria survive and persist in small number at the site of inflammation (fail to eliminate).

Recurrent attacks of acute inflammation leading to develop the chronic one. ii-Some immune diseases (Type-IV hypersensitivity). ii-Some specific diseases (can’t be removed by the host defense) as TB, some retroviruses, dust (silica and carbon).

Macroscopic Pictures: i-If the inflammation is not severe and the proliferative component is not profound it may not be noticed grossly. ii-If the fibrous tissue has yet to develop, the only gross change is paleness of the affected tissue (white to tan) than normal. iii-If there is large amount of fibrosis the inflammatory area appear indurated , tan and feels gritty upon cutting with scalpel (white in color).

Microscopic Pictures: the chronic inflammation is characterized by: i-Hyperplasia (proliferation): o Epithelium o Fibrous connective tissue o Lymphoid tissue (increase number of lymphocytes at the area).

NB: The proliferative changes are as a result of necrosis, proliferation of small blood vessels and fibroblasts is stimulated resulting in formation of “granulation tissue”. There are 4 components of this process:  Formation of new blood vessels (angiogenesis).  Migration and proliferation of fibroblasts.  Deposition of extracellular matrix.  Maturation and organization of the fibrous tissue (remodeling).

ii-Metaplasia: o The fibrous tissue changed into cartilage bone. o The epithelium changed into another type of epithelium. iii-Chronic inflammatory cells infiltrations: o Macrophages or Epithelioid cells (secretory macrophages). o Plasma cells. o Giant cells (its presence indicates rapid turn over of macrophages).

Types of Chronic Inflammation: I-Non-Specific: when the irritant substance produces a non-specific chronic inflammatory reaction with formation of granulation tissue and healing by fibrosis.

A-Chronic non-specific inflammation B- Chronic non-specific interstitial inflammation II-Specific: when the injurious agent causes a characteristic histological tissue response, e.g. tuberculosis, leprosy.

A-Chronic Granulomatous Inflammation.

Definition: It is a specific chronic inflammation characterized by formation of granulomas.

Granuloma: It is a chronic inflammatory reaction consisting of macrophages or macrophages and giant cells.

-The macrophages kill the intracellular microorganisms.

-They produce cytokines and certain degradative enzymes.

-They enhance the phagocytosis -They can recognize and kill tumor cells.

NB: The word “granuloma� is composed of granule meaning circumscribed granule-like lesion, and -oma, which is a suffix commonly, used for true tumors.

Types of granulomas: according to the nature of stimulus.

I-High Turnover Granulomas (hypersensitivity granulomas).

II-Low Turnover Granulomas (foreign body granulomas).

I-High Turnover Granulomas: i-They are characteristic response to TB, fungi, helminthes and their ova, and many organisms that replicate intracellular e.g. brucella. ii-They consist of focal collection of macrophages, epithelioid cells and Langhan’s giant cells besides T-lymphocytes. iii-The granulomas often become partially or completely surrounded by immature fibrous connective tissue which is infiltrated with lymphocytes.

II-Low Turnover Granulomas: i-They are formed in response to agent which fails to stimulate immune response such as silk suture, splinters or oil. ii-They consist of collection of macrophages associated with neutrophils surrounding the foreign objects and that may form foreign body giant cells (no lymphocytes and epithelioid cells).

NB: Other classification of granulomas: 1-Infectious granuloma.

2-Non-infectious granulomas.

How do endothelial cells become permeable?

Endothelial cell contraction Junctional retraction Direct endothelial injury (immediate sustained response) Leukocyte-dependent endothelial injury Increased transcytosis of fluid