effector cell, type of cell in the body that carries out a specific activity in response to stimulation. The term effector cell generally is applied to certain cells in the immune system; however, it is sometimes also used to refer to cells in the nervous system that are found at the ends of autonomic nerve terminals, where they effect a specific function upon activation.
In the immune system, effector cells are the relatively short-lived activated cells that defend the body in an immune response. Effector B cells are called plasma cells and secrete antibodies, and activated T cells include cytotoxic T cells and helper T cells, which carry out cell-mediated responses. The production of effector cells in response to first-time exposure to an antigen is called the primary immune response.