DURING the 1980s the number of allogeneic bone marrow transplantations performed worldwide increased exponentially. In 1990 more than 4000 allogeneic transplantations were estimated to have been completed. This dramatic increase has been stimulated by the demonstration that bone marrow transplantation is an important therapeutic option for many patients with leukemia or lymphoma. In addition, the establishment of international marrow-donor registries has made HLA phenotypically matched marrow from unrelated donors available to patients who lack a suitable related donor. These developments have focused attention on the immunologic aspects of allogeneic transplantation and its chief complication, graft-versus-host disease (GVHD).

Definition and Cause . . .