Any of the nearly colorless cells found in the blood, lymph, and lymphoid tissues, constituting approximately 25 percent of white blood cells and including B cells, which function in humoral immunity, and T cells, which function in cellular immunity.
Any of the nearly colorless cells formed in lymphoid tissue, as in the lymph nodes, spleen, thymus, and tonsils, constituting between 22 and 28 percent of all white blood cells in the blood of a normal adult human. They function in the development of immunity and include two specific types, B cells and T cells.
Any of various white blood cells, including B cells and T cells, that function in the body's immune system by recognizing and deactivating specific foreign substances called antigens. B cells act by stimulating the production of antibodies. T cells contain receptors on their cell surfaces that are capable of recognizing and binding to specific antigens. Lymphocytes are found in the lymph nodes and spleen and circulate continuously in the blood and lymph.