T-cell (Thymus-cell or T-lymphocyte) Type of lymphocyte (white blood cell) that is the key to the defence mechanism of the immune system. There are three main kinds of T-cells: Th (helper T-cells), Ts (suppressor T-cells), and Tc (cytotoxic T-cells). Helper T-cells recognize foreign antigens and help other immune cells to act; suppressor T-cells prevent specific immune reactions; and cytotoxic T-cells, or effector T-cells, kill cancerous cells or cells infected with a virus. T-cells are produced in the bone marrow and then move to the thymus gland. See also acquired immune deficiency syndrome (AIDS)

T-cell n. a type of lymphocyte that matures in the thymus and is primarily responsible for cell-mediated immunity. cytotoxic T-c. a T-cell that destroys cancerous cells, virus-infected cells, and allografts. helper T-c. a T-cell that stimulates the production of cytotoxic T-cells. suppressor T-c. a T-cell that prevents an immune response by other T-cells or B-cells to an antigen.

Tc • symb. the chemical element technetium.