<p><strong>Noun</strong></p><ul><li>Any substance, as a protein, carbohydrate, etc., that, on entering the body, can stimulate an immune response and combine with a specific antibody or T cell receptor having a matching molecular structure.</li><li>Any commercial substance, usually synthetic, that stimulates the production of antibodies when injected or absorbed into animal tissues.</li><li>Antigens of a particular type collectively.</li></ul><p><strong>End of Response</strong></p>