CELLULAR IMMUNITY - A form of cellular defense which identifies certain foreign substances (antigens) as harmful to the body. For this reason, the body can acquire "resistance" to a particular foreign agent. These foreign agents are then attacked by sensitized T lymphocytes (cellular immunity). White blood cells, plasma cells, B lymphocytes, and other specialized immune system cells act in concert with T lymphocytes to produce antibodies (humoral immunity) that attach to the antigen directing T cells to attack. Antibodies also stimulate the release of special chemical mediators in the blood (e.g. complement, interferon) that further enhance antigen destruction.