antigen

an·ti·gen

noun \ˈan-ti-jən, -ˌjen\

Definition of ANTIGEN

: any substance (as an immunogen or a hapten) foreign to the body that evokes an immune response either alone or after forming a complex with a larger molecule (as a protein) and that is capable of binding with a product (as an antibody or T cell) of the immune response

— an·ti·gen·ic \ˌan-ti-ˈje-nik\ adjective

— an·ti·gen·i·cal·ly \-ni-k(ə-)lē\ adverb

— an·ti·ge·nic·i·ty \-jə-ˈni-sə-tē\ noun

Origin of ANTIGEN

German, from French antigène, from anticorps antibody + -gène -gen

First Known Use: 1908

an·ti·gen

noun \ˈant-i-jən\   (Medical Dictionary)

Medical Definition of ANTIGEN

: any substance (as an immunogen or a hapten) foreign to the body that evokes an immune response either alone or after forming a complex with a larger molecule (as a protein) and that is capable of binding with a product (as an antibody or T cell) of the immune response

—an·ti·gen·ic \ˌant-i-ˈjen-ik\ (audio pronunciation) adjective

—an·ti·gen·i·cal·ly \-i-k(ə-)lē\ (audio pronunciation) adverb

Illustration of ANTIGEN

antigen

noun    (Concise Encyclopedia)

Foreign substance in the body that induces an immune response. The antigen stimulates lymphocytes to produce antibodies or to attack the antigen directly (see antibody;immunity). Virtually any large foreign molecule can act as an antigen, including those of bacteria, viruses, parasites, foods, venoms, blood components, and cells and tissues of various species, including other humans. Sites on the antigen's surface fit and bind to receptor molecules on the lymphocytes' surface, stimulating the latter to multiply and initiate an immune response that neutralizes or destroys the antigen.