A type of white blood cell that is of key importance to the immune system
and is at the core of adaptive immunity, the system that tailors the body`s immune response to specific pathogens. The T cells are like soldiers who search out and destroy the targeted invaders.
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 maturational 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 further stimulate the immune response. T-cell activation is measured as a way to assess the health of patients with HIV/AIDS and less frequently in other disorders.
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.
