Vaccinations

are made allow for a much quicker and stronger response to the infection should the infectious organism enter the host again.

VACCINATIONS

Vaccinations are important to the prevention of infection. It artificially stimulates the adaptive immune system in a way that resembles a primary immune response. The difference is that no actual infection really occurs with a vaccination.

Immunity can be active or passive. Natural active immunity happens after a person gets the infection itself. This confers lifelong immunity to the pathogen and is how many people get immunity to a particular pathogen. Natural passive immunity is when a fetus gets temporary immunity through the transfer of IgG antibodies. This lasts up to six months, although IgA antibodies will come to the infant through breast milk.

Artificial passive immunity comes from getting antibodies to an infection by a donor. This is when immunoglobulins are given to a person who has been exposed to a particular antigen and when the person will be greatly harmed by getting the infection. It can be used to protect against toxin-related illnesses. Artificial active immunity is what immunizations or vaccinations involve. The adaptive immune system is activated by receiving epitopes that confer immunity but do not cause infection.

Herd immunity refers to the fact that, if most of the people in a community have resistance to an infection, this means that fewer people have the ability to pass on the infection to others and fewer actual infections happen, even if not everyone is immune. This has been a problem with certain infections that some parents object to giving their child. If too few are immune, the risk of infection in the community increases for every nonimmune person.

There are different types of vaccines that can protect against disease. Live attenuated vaccines have living organisms injected into the person but the infected organisms are weakened and do not usually have the ability to cause real disease. The risk is that the attenuated organism can mutate to become a pathogenic organism, which can lead to disease, particularly in immunocompromised host.

Inactivated vaccines have whole pathogens in them that are either killed or inactivated somehow. The inactivation must be mild enough not to destroy the architecture of the epitopes. These are more easily stored and transported but do not produce any active infection so the immune response is not as strong. Multiple booster shots usually need to be given.

Other vaccine types are subunit vaccines that have only antigens and not whole organisms. Toxoid vaccines only contain inactivated bacterial toxins, known as toxoids. Toxoid vaccines are used in infections that have toxins associated with them. Conjugate vaccines have a protein that is attached to a polysaccharide capsule to fight infections that involve encapsulated organisms.

Key Takeaways

• The adaptive immune system involves specificity to an organism and memory for the infection. • The main cells of the adaptive immune system are T cells and B cells. • Adaptive immune cells undergo selection in order to have a cell that does not selfreact to self-cells. • Cytotoxic T cells react similarly to NK cells that specifically kill infected or damaged cells with perforins and granzymes. • Immunizations provide immunity to an infection, usually without causing an actual infection.