Antigen

Article By:

Polley, Margaret J. Department of Medicine, Cornell Medical Center, New York, New York.

Cohen, Zoë Department of Blood Transfusion Medicine Research, Saint Michael's Hospital, Toronto, Ontario, Canada.

Last reviewed:February 2020

DOI:https://doi.org/10.1036/1097-8542.040600

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• Antigen, published June 2014:Download PDF Get Adobe Acrobat Reader

Any substance that causes the immune system to produce specific antibodies or T cells against it. An antigen may be a foreign substance from the environment (such as chemicals, bacterial or viral proteins, or pollen; Fig. 1) or formed within the host's own body. Reactions of antigens with antibodies or T cells [thymic lymphocytes (white blood cells), which are capable of suppressing immune reactions and attacking other cells] serve as a defense against microorganisms and other foreign bodies, but can be detrimental if the immune response is mounted against the "self," as in autoimmune disorders. Antigen-antibody complexes are used in laboratory tests for detecting the presence of either antigen or antibody to determine a subject's previous exposure to pathogens. See also: Antibody; Antigen-antibody reaction; Autoimmunity; Immunologic cytotoxicity; Immunology; Immunopathology; Pathogen

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