a type of white blood cell that seeks out and destroys cells that have already been invaded by a virus or some other substance

White blood cells that are part of the immune system and destroy microorganisms and cancer cells.

a group of T cells that is activated by helper T cells and have the ability to destroy cells infected by foreign invaders (such as viruses). Also known as cytotoxic T cells.

see CD8+ T cells.

T cells that carry T-cell receptors and kill cells displaying the recognized antigens.

Because viruses lurk inside host (e.g. human) cells where antibodies cannot reach them, the only way they can be eliminated is by killing the infected host cell. To do this, the immune system uses a kind of white blood cell, called killer T cells. Also known as cytotoxic T cells (or cytotoxic T lymphocytes). See Natural Killer (NK) Cells; T Cells.