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ADAPTIVE IMMUNE SYSTEM

ADAPTIVE IMMUNE SYSTEM. LYMPHOCYTES. Specificity and Memory. Lymphocytes are responsible for the specificity and memory in adaptive immune responses.

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ADAPTIVE IMMUNE SYSTEM

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  1. ADAPTIVE IMMUNE SYSTEM

  2. LYMPHOCYTES

  3. Specificity and Memory • Lymphocytes are responsible for the specificity and memory in adaptive immune responses. • They are produced in the primary lymphoid organs and function in the secondary lymphoid organs / tissues where they recognize and respond to foreign antigens. • There are three types of lymphocytes – NK cells, T cells and B cells,although only T and B cells have true antigen specifiicity and memory. • T cells and B cells mature in the thymus and bone marrow, respectively. In the resting state both T and b lymphocytes have a similar morphology with a small amount of cytoplasm.

  4. They have specific but different antigen receptors and a variety of other surface molecules necessary for interaction with other cells. • These include molecules required for their activation and for movement into and out of the tissues of the body. • This ability to migrate into the tissues and return via the lymphatic vessels to the blood stream is a unique feature of lymphocytes. • There are two classes of T lymphocytes, T helper cells and T cytotoxic cells. All T lymphocytes have antigen receptors (TcR) which provide their specificity and CD3 which is essential for their activation. • These molecules also serve as “Markers” to identity T cells. • B lymphocytes make and use antibodies are their specific antigen receptor. They have molecules similar to CD3, i.e. CD79 which are important in their activation. • B lymphocytes can mature into plasma cells which produce and secrete large amounts of antibody.

  5. Characteristics of Human B and T cells

  6. B Lymphocytes and Plasma Cells • B cells are produced in the bone marrow and like T cells migrate to the secondary lymphoid organs and tissues where they responed to foreign antigens. There are two kinds of B cells. • B1 cells: These cells arise early in ontogeny, express mainly lgM antibodies encoded by germ-line antibody genes, mature independently of the bone-marrow, generally recognize multimmeric sugar / lipid antigens of microbes and are T cell independent. • B2 cells: These cells are the B cells primarily responsible for the development of humoral mediated immunity. They are produced in the bone marrow, and with the help of T cells produce lgG, lgA and lgE antibodies.

  7. B cells are mainly found in loose aggregates in lymphoid tissues or in well-defined proliferating foci. • Antibodies are the antigen receptor on these cells and are associated with several other molecules which form the B cells receptor complex. • When activated by antigen and, in most cases, with T cell help, B cells proliferate and mature into memory cells or plasma cells. • Memory cells only produce antibody for expression on their cell surface and remain able to respond to antigen if it is reintroduced. • In contrast, plasma cells do not have cell surface antibody receptors. • Rather these cells, which are derived from activated B cells, function as factories producing and secreting large amounts of antibody of the same specificity as the antigen receptor on the stimulated parent B cells.

  8. THANK YOU

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