<haematology, immunology> A class of lymphocytes, so called because they are derived from the thymus and have been through thymic processing. Involved primarily in controlling cell-mediated immune reactions and in the control of B-cell development. The T-cells coordinate the immune system by secreting lymphokine hormones.

There are 3 fundamentally different types of t cells : helper, killer, and suppressor. Each has many subdivisions. T-cells are also called t lymphocytes.

They bear 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.

(21 Jun 1999)