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Explain the phenomenon of adaptive immunity with special reference to its properties, activation, clonal selection, and its role in Vaccination.

Last updated date: 20th Jun 2024
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Hint: Adaptive immunity is one of the two types of immunity. Adaptive or acquired immunity comes after our birth and develops with time, whereas we are born with the innate immunity in our body.

Complete answer:
The ability of the body that defends itself against disease and the infection-causing organisms is called immunity. It is of two types mainly Innate immunity and Acquired or adaptive immunity.
Adaptive immunity is the type of immunity that our body gains over time. It is not present in the body by birth. The adaptive immune system is composed of highly specialized cells and processes the elimination of pathogens or prevents their growth inside us. It is specified and mediated by antibodies or lymphocytes.
The main function of this type of immunity is to relive our body from infectious disease and prevent its attack in the future as well.
Activation of adaptive immunity:
This type of immunity takes longer than innate immunity. Also without the information from the innate immune system, it could not be mobilized. The adaptive immune system is of two types
a)Cell-mediated immune response- It is carried out by T cells. These cells eliminate the infected cells by releasing toxins, thus promoting programmed cell death or apoptosis. These cells also activate other immune cells.
b)Humoral immune response: This response consists of antibodies produced by B-lymphocytes. These antibodies are present in blood cells and transported all over the body. The humoral immune response occurs when a B-cell binds with an antigen. The antigen is internalized and presented on the helper T cell. The activation of the B cell through this produces plasma cells. The B cells also retain the information about pathogens to use in the near future.
Clonal selection and vaccination:
Clonal selection is a hypothesis which states that there is already a vast array of lymphocytes present in the body before infection. The body selects only one type of lymphocytes to match with an antigen and produce the corresponding antibody to destroy it. This hypothesis was introduced by doctor Frank MacFarlane Burnet in 1957. This concept is used in Vaccine Immunology, by using a specific type of vaccine for different diseases.

Note: Clonal selection and adaptive immunity are related and this selection is very important for adapting immune response. After the presentation of the antigen, the selected lymphocytes undergo clonal expansion as they have the needed antigen receptor. The clonal selection concept also explains why memory cells can initiate secondary immune response more quickly than primary ones. This is due to the binding affinity from clonal expansion.