Protection against hemolysis in ABO mismatched renal transplantation

The kidneys from a blood group O cadaver donor were transplanted into two patients whose blood groups were B and A2B. The former developed a positive direct antiglobulin test (DAT) and hemolysis due to anti-B; the latter also developed a positive DAT, but due to anti-A. However, this second patient, unlike the first, did not have any hemolysis. Both patients were on the same immunosuppression regimen with cyclosporine. The possible protective roles of patients' ABO subgroup and blood group substances in plasma are discussed.