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T-lymphocyte

(Science: haematology, immunology) A class of lymphocytes, derived from the thymus gland. They originate from lymphoid stem cells that migrate from the bone marrow to the thymus and differentiate under the influence of the thymic hormones. Various subpopulations have been described.

They help to control cell-mediated immunity and the control of b-cell development, to facilitate antibody production. T lymphocytes assist in the recognition and rejection of foreign tissues and provide immune surveillance for cancer.

They express t-cell antigen receptors (cD3) and lack fc or C3b receptors. Major t-cell subsets are cD4 (mainly helper cells) and cD8 (mostly cytotoxic or suppressor T-cells). Uncontrolled proliferation of this type of cell gives rise to t-cell leukaemia/lymphoma.