T cell
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T cells, a type of lymphocyte (white blood cell), have an important role in the body's immune system. When a T cell encounters an invading virus it begins to divide, forming four different types of T cell, each with a different function. Killer T cells destroy cells that have become infected with the virus by lysis. Helper T cells activate more killer T cells and also stimulate B cells to begin antibody production (unlike B cells, T cells do not produce antibodies to destroy invading pathogens). Suppressor T cells protect healthy cells from viral attack and memory T cells persist in the bloodstream to guard against re-infection.
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.
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