Definition and complications in ABO-mismatched HSCT
Major ABO-mismatched HSCT
Major ABO-mismatched HSCT can cause hemolysis of donor’s erythrocytes by recipient’s IHAs10. In bone marrow derived grafts, hemolysis is more common than PBSC due to the high amount of erythrocytes in bone marrow11.
In major ABO-mismatched HSCT, hemolysis can be prevented by removing erythrocytes from graft. Insignificant hemolysis can also occur during erythrocyte engraftment due to destruction of erythrocytes containing donor’s antigens by means of recipient’s IHAs12. Finally, these reactions cause pure red cell aplasia (PRCA) in the majority of patients who had major ABO-mismatched HSCT 13. Antibody titers can be diminished in major ABO-mismatched HSCT by plasma or whole blood exchange before engraftment8.
Minor ABO-mismatched HSCT (passenger lymphocytes syndrome)
About 7-14 days after the infusion of graft, hemolysis occurs due to donor’s IHAs against recipient’s erythrocytes14.
1. This immediate hemolysis can be more severe than major ABO-mismatched HSCT that usually decreases after 5-10 days. In this situation, direct antiglobulin test (DAT) is usually positive against recipient’s erythrocytes antigens.
2. Passenger lymphocyte syndrome: A second hemolytic reaction occurs due to immunization of donor’s B lymphocytes, which is called passenger lymphocytes (PL) and production of IHAs against recipient’s erythrocytes, which is called “delayed hemolysis”. An important factor in development of PL syndrome is PBSC-derived grafts due to high lymphocyte content15.
In minor ABO-mismatched HSCT, IHAs can be removed from the graft by various techniques. There is a significant association between minor ABO-mismatched HSCT and increased risk of acute graft-versus-host disease (aGVHD) in patients.
Reference: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6375375/
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