In less than a decade since the Seattle team achieved a successful bone marrow transplantation,1 this procedure has become an acceptable treatment for leukemia and a preferred treatment for severe aplastic anemia.2 However, the success of this therapy is lessened by complicating infections and graft-vs-host reactions, with attendant graft rejection and mortality. Even though the donor is a family member with identical human leukocyte antigen, the risk of graft rejection hangs over the patient like the sword of Damocles.
To reduce the risk of graft rejection, a conditioning immunosuppressive regimen is scrupulously followed. This usually entails using total-body irradiation, methotrexate for prevention of graft-vs-host reaction, and corticosteroids and antithymocyte globulin when this reaction develops. Despite such regimens the incidence of graft-vs-host disease remains high. Thomas and associates3 reported the occurrence of this complication in 12 of 19 marrow transplant patients with acute myelogenous leukemia, five of whom