A protein that is made by certain lymphocytes (white blood cells) to neutralize an antigen (foreign protein) in the body. Bacteria, viruses, and other microorganisms contain many antigens; antibodies that are formed against these antigens help the body to neutralize or destroy the invading microorganisms. Antibodies may be formed in response to vaccines, thereby giving immunity. Antibodies are also known as immunoglobulins. Inappropriate or excessive formation of antibodies may lead to illness, as in an allergy. Antibodies against antigens in organ transplants may result in rejection of the transplanted organ. In some disorders, antibodies are formed against the body’s own tissues, resulting in an autoimmune disorder.


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