MedlinePlus Medical Encyclopedia: Antigen

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Antigen

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Illustrations	Definition

Illustrations

Antigens

Definition Return to top

An antigen is any substance that causes your immune system to produce antibodies against it. An antigen may be a foreign substance from the environment such as chemicals, bacteria, viruses, or pollen. An antigen may also be formed within the body, as with bacterial toxins or tissue cells.

Update Date: 7/19/2007

Updated by: Donald Accetta, MD, MPH, President, Allergy & Asthma Care, PC, Taunton, MA. Review provided by VeriMed Healthcare Network.

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