MedlinePlus Medical Encyclopedia: Antibody

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Antibody

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Illustrations	Definition

Illustrations

Antibodies

Definition Return to top

An antibody is a type of protein. The body's immune system produces antibodies when it detects harmful substances, called antigens. Examples of antigens include microorganisms (such as as bacteria, fungi, parasites, and viruses) and chemicals.

Antibodies are also be produced when the immune system mistakenly considers healthy tissue a harmful substance. See: Autoimmune disorders

Each type of antibody is unique and defends the body against one specific type of antigen.

Update Date: 10/18/2008

Updated by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; and George F. Longstreth, MD, Department of Gastroenterology, Kaiser Permanente Medical Care Program, San Diego, California. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

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