A class of chemicals, called the immunoglobulins, made by the cells of the immune system to specifically tag or identify foreign material within the body of the host. Antibodies combine with specific markers—antigens—found on viruses, bacteria, or other toxins, and agglutinate them. The immune system is capable of manufacturing millions of different antibodies against a wide variety of potential invaders. Individuals of Type O, Type A, or Type B blood carry anti-bodies to other blood types. Type AB, the universal recipient, manufactures no antibodies to other types.