DETECTION OF GENETICALLY DETERMINED HISTOCOMPATIBILITY ANTIGEN DIFFERENCES BETWEEN HL‐A IDENTICAL AND MLC NONREACTIVE SIBLINGS

SUMMARY Five patients with aplastic anemia were shown to be sensitized in vivo to the transplantation antigens of HL-A identical and MLC nonreactive sibling bone marrow transplantation donors. The sensitization in four cases were detected by antibody-in dependent cell-mediated lysis (AICML) techniques, and in one case by antibody-dependent cell-mediated lysis (ADCML). In two cases the inherited nature of the sensitizing antigen was demonstrated, and in one case the inheritance of the antigen was shown by a family study to be independent of the HL-A and MLC loci. Maximal AICML was demonstrated in two cases at the time of bone marrow graft rejection. Successful transplants after immunosuppression with rabbit anti-thymocyte serum, procarbazine, and cyclophosphamide were performed in two patients, in whom sensitization was detected before transplantation.