T cells are a group of white blood cells known as lymphocytes, and are a central component to our body’s defense system and are 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.

T-cells can be distinguished from other lymphocyte types, such as B cells and natural killer cells by the presence of a special receptor on the cell’s surface called T cell receptors (TCR). 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.