an·ti·gen  (ān'tĭ-jən)  n. A substance that when introduced into the body stimulates the production of an antibody. Antigens include toxins, bacteria, foreign blood cells, and the cells of transplanted organs. an'ti·gen'ic (-jěn'ĭk) adj., an'ti·gen'i·cal·ly adv., an'ti·ge·nic'i·ty (-jə-nĭs'ĭ-tē) n. |