Definition of antigen
: any substance (such 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 (such as a protein) and that is capable of binding with a product (such as an antibody or T cell) of the immune response
antigenicplay \ˌan-ti-ˈje-nik\ adjective
antigenicallyplay \-ni-k(ə-)lē\ adverb
antigenicityplay \-jə-ˈni-sə-tē\ noun
Did You Know?
An antibody is a protein produced by your immune system to fight outside invaders. Since the enemy substance actually triggers the production of antibodies, such substances are called antigens—anti- being short for antibody, and -gen meaning "producer". (In a similar way, an allergen produces an allergy, and a pathogen produces a pathology or disease.) Antigens are often rodlike structures that stick out from the surface of an invading organism—usually a bacterium or a virus—and allow it to attach itself to cells in the invaded body. But unfortunately for them, in doing so they let the immune system know they're present, and the body is flooded with an army of Pac-Man-like antibodies.
Origin and Etymology of antigen
German, from French antigène, from anticorps antibody + -gène -gen
First Known Use: 1908See Words from the same year
ANTIGEN Defined for English Language Learners
Definition of antigen for English Language Learners
medical : a harmful substance that causes the body to produce antibodies
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
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