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This article waslast modified on 10 July 2017.
White blood cell (leucocyte) containing no granules that normally makes up about 25% of the total white blood cell count but increases in the presence of infection. Lymphocytes occur in two forms: B cells, the chief agents of the humoral immune system, which recognize specific antigens and produce antibodies against them; and T cells, the agents of the cell-mediated immune system, which secrete immunologically active compounds and assist B cells in their function.