noun, plural: antigens
Any of the various substances that when recognized as non-self by the adaptive immune system triggers an immune response, stimulating the production of an antibody that specifically reacts with it.
Antigens may be exogenous antigens, endogenous antigens or autoantigens depending on their origin.
Word origin: Contraction of antibody-generator.
Related forms: antigenic (adjective), antigenically (adverb)
See also: allergen, immunogen.