Bone marrow transplantation for aplastic anaemia from a HL-A and MLC-identical unrelated donor.

Bone-marrow transplantation (BMT) from an unrelated, HL-A-phenotype-identical, MLC-negative donor was performed in a 31 year old woman with severe longlasting aplastic anemia. In vitro assays failed to demonstrate humoral or cellular sensitization of the recipient against donor-type antigens. Following conditioning with cyclophosphamide, prompt but only transient engraftment of the transplant occurred accompanied by signs of mild graft-versus-host-disease (GVHD) of the liver. The results of a second bone marrow transplantation from the same donor cannot be evaluated due to early death of the recipient. It is concluded that bone marrow from unrelated, HL-A and MLC-identical donors may engraft without severe GVHD. Rejection of the graft in our patient may have been related to greater antigenic differences that can be expected to exist between HL-A and MLC-identical unrelated individuals than between HL-A and MLC-identical siblings. However, insufficient preparative immunosuppression with cyclophosphamide due to severe hepatic hemosiderosis appears equally likely as the cause of graft rejection. The possibly increased risk of graft rejection or severe GVHD should not preclude the use of unrelated HL-A and MLC-identical marrow donors, when histocompatible sibling donors are not available; but more potent immunosuppressive regimens than the cyclophosphamide protocol may be necessary to ensure permanent engraftment.