ABH antigens and bone marrow transplantation.

We studied the role of ABH antigens in determining graft outcome in 104 patients who received HLA-identical bone marrow transplants for aplastic anaemia and acute leukaemia. ABH compatibility had no significant effect on incidence of graft rejection or graft-versus-host disease. Fifteen recipients ahd pre-transplant antibodies against donor ABH antigens. In 14, large volume plasma exchange and transfusion of donor-type erythrocytes was successful in reducing the antibody titre to low or undetectable levels. In one patient, plasma exchange was unsuccessful and red cells were removed from the marrow inoculum by unit gravity sedimentation. This approach prevented transfusion reaction, and permitted engraftment of all haematopoietic cell lines despite persistently elevated antibody titres. Parallel in vitro studies revealed that antibodies to ABH antigens failed to inhibit the growth of progenitor cells committed to both granulocyte-macrophage (CFU-C) and erythroid (BFU-E) development. These findings indicate that ABH-antigens are not clinically important transplantation antigens and suggest that ABH antigens are not operationally present on hematopoietic stem cells.