T cell

Immune cell (see immunity and lymphocyte) that plays several roles in the body's defences. T cells are so called because they mature in the thymus (as opposed to the B cells, which mature in the bone marrow).

There are three main types of T cells: T helper cells (Th cells), which allow other immune cells to go into action; T suppressor cells (Ts cells), which stop specific immune reactions from occurring; and T cytotoxic cells (Tc cells), which kill cells that are cancerous or infected with viruses. Like B cells, to which they are related, T cells have surface receptors that make them specific for particular antigens.