Low incidence of acute graft-versus-host disease by the administration of methotrexate and cyclosporine in Japanese leukemia patients after bone marrow transplantation from human leukocyte antigen compatible siblings; possible role of genetic homogeneity. The Nagoya Bone Marrow Transplantation Group

Japanese patients with leukemia who received bone marrow from human leukocyte antigen (HLA)-compatible siblings had a low incidence of acute graft-versus-host disease (GVHD). Twenty-five (21%) of 120 patients developed moderate (grade II) to severe (grades III to IV) acute GVHD. Severe GVHD was only seen in patients older than 20 years of age. It is also notable that only 2 (5%) of 39 patients who received the combination of methotrexate and cyclosporine (MTX/CSP) for the prevention of GVHD developed grade II acute GVHD, and none developed grades III to IV acute GVHD. Thirteen (30%) of 44 patients receiving MTX alone and 10 (27%) of 37 patients receiving CSP alone developed grades II to IV acute GVHD. Multivariate life-table analysis indicated that the prophylaxis by MTX/CSP was the risk factor for the low incidence of grades II to IV acute GVHD. Compared with the reported incidence of acute GVHD in the patients of the United States, lower incidence of acute GVHD in Japanese BMT patients might be attributable to a lesser degree of genetic diversity in histocompatibility antigens among Japanese.