T cell

Immunol.

any of several closely related lymphocytes, developed in the thymus, that circulate in the blood and lymph and orchestrate the immune system's response to infected or malignant cells, either by lymphokine secretions or by direct contact: helper T cells recognize foreign antigen on the surfaces of other cells, then they stimulate B cells to produce antibody and signal killer T cells to destroy the antigen-displaying cells; subsequently suppressor T cells return the immune system to normal by inactivating the B cells and killer T cells. Also called T lymphocyte.

[1965-70; T(hymus-derived)]

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With the B cell, one of the two main types of white blood cell, essential parts of the immune system.

T cells originate in the bone marrow, mature in the thymus, and travel in the blood to other lymphoid tissues, such as the spleen, tonsils, and lymph nodes. Through receptor molecules on their surfaces, T cells directly attack invaders (antigens) by binding to them and helping remove them from the body. Because the body contains millions of T and B cells, many of which carry unique receptors, it can respond to virtually any antigen. See also antibody, immunology.

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