Anitbodies - Antigens

Antibodies - A class of proteins (known as immunoglobulins) formed in the body in response to the presence of antigens (foreign proteins and other compounds), which bind to the antigen, inactivating it.

Antigens - Foreign substances in the body that are capable of causing disease. The presence of antigens in the body triggers an immune response, usually the production of antibodies. Antigens may be soluble substances, such as toxins and foreign proteins, or particulate, such as bacteria and tissue cells; however only the portion of the protein of polysaccharide molecule known as the antigenic determinant combines with antibody or a specific receptor on a lymphocyte.