What term describes antibodies produced after exposure to foreign antigens via transfusion or pregnancy?

• A. Autoantibodies
• B. Alloantibodies
• C. Isoantibodies
• D. Heteroantibodies

Answer: (B)

Alloantibodies are antibodies formed in response to non-self antigens from another individual of the same species. When exposure occurs through a transfusion, the recipient may form alloantibodies against donor red cell antigens. In pregnancy, fetal red cell antigens inherited from the father can also stimulate maternal alloantibody production. These antibodies are directed at antigens that the individual does not have, which is why they can cause reactions in transfusion or hemolytic disease in the newborn if the corresponding antigen is present. This differs from autoantibodies, which target the person’s own antigens. Isoantibodies is a term sometimes seen, but alloantibodies is the standard clinical term for antibodies formed after exposure to foreign antigens via transfusion or pregnancy.