Describe the events that occur after a B cell is exposed to its specific antigen.

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B cells mature and proliferate within the lymphatic system. They will typically differentiate into either a memory B cell or a plasma B cell. Plasma B cells are responsible for secreting antibodies when activated. Plasma B cells which migrate to tissues are usually very short-lived. Longer-lived B plasma cells usually migrate to bone marrow. While there, they secrete specific antibodies into the bloodstream or lymphatic circulation system. These antibodies enter the site of infection to promote the immune response that combats whatever antigen is present in the area.

When a B cell is exposed to most antigens something known as humoral immunity occurs. When an antigen is detected, B cells, along with the aid of T helper cells, begin producing specialized antibodies to combat the specific antigen. This only occurs when antigens are circulating freely in the body, not inside of infected cells. The antigens produced by the B cells are designed to bind with the antigen when they are encountered. This renders the antigen inert; it is then destroyed by phagocyte cells or lysin enzymes.

This response is different from the cellular immunity which occurs within the body's cells themselves. While T cells play a role in both types of immune responses, B cells are not involved with cellular immunity.

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