The most serious hemolytic transfusion reactions are usually due to incompatibility in which blood group system?

The most serious hemolytic transfusion reactions are primarily associated with incompatibility in the ABO blood group system. This is due to the presence of naturally occurring antibodies in the plasma of individuals who lack specific ABO antigens on their red blood cells. For instance, a person with blood type A has anti-B antibodies, and if they receive type B or AB blood, their immune system recognizes those transfused cells as foreign. This leads to a strong and potentially life-threatening immune response that includes hemolysis, where the body's immune cells attack and destroy the transfused red blood cells.

The ABO system's ability to cause rapid and severe reactions is significantly heightened compared to other blood group systems, such as Rh, MN, or Duffy. While Rh incompatibility can lead to serious reactions as well, particularly in the context of hemolytic disease of the newborn, it typically does not cause immediate hemolytic transfusion reactions because the antibodies in the Rh system develop more slowly and usually do not pre-exist in individuals who are Rh-negative.

The MN and Duffy blood group systems are associated with less severe transfusion reactions. Antibodies against these groups exist, but they do not usually lead to acute hemolytic reactions because they tend to