What are the Types of Lymphocytes?

T LYMPHOCYTES:

Lymphocytes that differentiate and mature in thymus before their release into circulation are known as thymus cells or T cells in short.

Based upon the surface markers, different subsets are noticed in T cells. T cells play a major role in cell -mediated immunity. Even though different subsets formed in thymus are immunologically competent, they are functionally inert as long as they are in thymus.

Because in thymus they fail to get contact with the pathogens. They become functional only when they reach T dependent areas of the secondary or peripheral lymphoid organs and exposed to pathogens (Refer T cells & immunity in chapter 4 for further details).

B LYMPHOCYTES:

Lymphocytes that develop in bursa of fabricus (birds) or bursa equivalent regions in bone marrow are known as B lymphocytes.

The letter B is used to indicate bursa of fabricus or bone marrow. In immune system they are responsible for humoral / antibody mediated immunity. Antigenic challenge initiates immuno competent B cells to produce plasma cells that in turn secrete antibodies that are very specific for the antigen.