Bone Marrow–Allograft Rejection by T Lymphocytes Recognizing a Single Amino Acid Difference in HLA-B44

BONE marrow from unrelated donors is increasingly being transplanted for the treatment of patients with leukemia, aplastic anemia, and lethal congenital disorders of hematopoiesis and immunologic function. National and international registries of HLA-typed volunteer donors have been developed to optimize HLA matching between unrelated donors and recipients.1 , 2 The fate of marrow grafts depends on many factors, including conditioning regimens, the composition of the cells in the graft, immunosuppression after transplantation, and the degree of histocompatibility between donor and recipient. Clinically serious graft-versus-host disease occurs in 20 to 50 percent of patients receiving marrow grafts from HLA-identical siblings, and some measure . . .