| Antibody | A modified protein molecule present in the blood serum or plasma (and other body fluids), whose activity is associated chiefly with gamma globulin. Produced by the immune system in response to exposure to a foreign substance, it is the body's protective mechanism against infection and disease. An antibody is characterized by a structure complementary to the foreign substance, the antigen that provokes its formation, and is thus capable of binding specifically to the foreign substance to neutralize it. |
