Hemagglutinin, (Anti-A and Anti-B) are which type of antibodies?

Ans. B. IgM. (Ref. H-17th/pg. 708-709; Wintrobe's clinical hematology 13th/ pg. 979)Isohemagglutinins, substances that agglutinate the red blood cells of others of the same species, are also found in humans. Thus, there are four main blood groups, which differ with respect to two antigens, A and B, in the red blood cells and two isohemagglutinins, anti-A and anti-B, in the serum. Thus, in humans, type O has neither antigen but both agglutinins, type A has A antigen and anti-B.# Anti-A and anti-B antibodies are usually IgM and do not pass through the placenta.