The strict definition of this term is an antibody that agglutinates red blood cells from others of the same species. So, technically, we could call any alloantibody identified in human plasma an “isohemagglutinin.” However, blood bankers use the term only in reference to the naturally occurring antibodies in the ABO blood group system:
- Anti-A in a group B person
- Anti-B in a group A person
- Anti-A, anti-B, and anti-A,B in a group O person
These antibodies are of paramount importance in blood banking, as the majority of our processes are designed to ensure compatibility between donor ABO antigens and recipient isohemagglutinins.
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