T cell

A type of white blood cell that is of crucial importance to the immune system. Immature T cells (termed T- stem cells) migrate to the thymus gland in the neck, where they mature and differentiate into various types of mature T cells and become active in the immune system in response to a hormone called thymosin and other factors. T-cells that are potentially activated against the body’s own tissues are normally killed or changed (“down-regulated”) during this maturation process. There are several different types of mature T cells. Not all of their functions are known. T cells can produce substances called cytokines, such as the interleukins, which in turn further stimulate the immune response. T-cell activation is measured as a way to assess the health of patients with the HIV virus (AIDS). T-cell activity is examined less frequently in other disorders, but as we learn more about how the immune system works, it is becoming part of the routine process for assessing many immune conditions and some types of cancer. T cell are also known as T lymphocytes. The "T" stands for "thymus" — the organ in which these cells mature. As opposed to B cells which mature in the bone marrow.

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T cell n any of several lymphocytes (as a helper T cell) that differentiate in the thymus, possess highly specific cell-surface antigen receptors, and include some that control the initiation or suppression of cell-mediated and humoral immunity (as by the regulation of T and B cell maturation and proliferation) and others that lyse antigen-bearing cells called also T lymphocyte see CYTOTOXIC T CELL, HELPER T CELL, SUPPRESSOR T CELL, T4 CELL