LYMPHOCYTES
Unlike granulocytes and monocytes which move unidirectionally from bone marrow to blood to tissue, blood lymphocytes recirculate. The pattern is blood to lymph node to lymph and back to blood. Transit time in the blood during each circuit is estimated to be 8 to 12 hours. Recirculating lymphocytes are long-lived cells which survive for months to years.
Function
Lymphocytes are the cells of the specific immune system. B lymphocytes differentiate into plasma cells which produce antibodies (humoral immunity).
T lymphocytes are responsible for cellular immunity through the formation and release of molecules known collectively as cytokines.
Peripheral blood lymphocytes serve as the memory cells of the immune system. As they recirculate, lymphocytes monitor for the presence of antigens to which they have been previously sensitized. When lymphocytes activated by such contact enter lymphnodes, they can initiate both the cellular and humoral immune response through selective clonal expansion.
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