antibody (AN-tee-BAH-dee) is a protein made by plasma cells (a type of white blood cell) in response to an antigen (a substance that causes the body to make a specific immune response) . Each antibody can bind to only one specific antigen. The purpose of this binding is to help destroy the antigen. Some antibodies destroy antigens directly. Others make it easier for white blood cells to destroy the antigen. An antibody is a type of immunoglobulin.