antigen an·ti·gen (ān'tĭ-jən)
Any of various substances, including toxins, bacteria, and the cells of transplanted organs, that when introduced into the body stimulate the production of antibodies. Also called allergen, immunogen.
antigenicity an·ti·ge·nic·i·ty (ān'tĭ-jə-nĭs'ĭ-tē)
The capacity to induce an immune response.
The degree to which a substance induces an immune response. Also called immunogenicity.