Lymphocyte Cell in the immune system responsible for specific immunity. Lymphocytes are present in the blood (they constitute 25 % of white blood cells in adults) and in lymphoid organs (bone marrow, thymus, lymphatic ganglions, spleen, tonsils, etc).
There are two categories of lymphocytes that differ according to their function. The T lymphocytes, which depend on the thymus, are responsible for cellular immunity. After activation, they can kill other living cells and produce factors that play a central role in the body’s immune response. The B lymphocytes depend on the bone marrow and, by producing antibodies, ensure humoral immunity.
Under the microscope, lymphocytes appear as ovoid, nucleated cells, whose large nucleus (approximately 7 µm) takes up almost the entire body of the cell.
