MARROW TRANSPLANTATION FROM UNRELATED VOLUNTEER DONORS

Marrow transplants from human leukocyte antigen (HLA)-compatible unrel ated volunteer donors have become feasible for more than 30% of patien ts without a family match and have allowed long-term, disease-free sur vival in 15-65% of patients with a variety of hematological disorders. However, unrelated donor transplants have a higher incidence of graft failure and graft versus host disease (GVHD) than do HLA-matched sibl ing transplants. This increase may be due to disparities between donor and recipient for undetected HLA determinants or for non-HLA histocom patibility genes. Because of the large number of HLA loci and their hi gh degree of polymorphism fully compatible donors will not be found fo r most patients, Fortunately, a limited degree of HLA mismatch does no t necessarily impair long-term survival in patients with hematologic m alignancy. Current studies ai-e defining the risk associated with mism atching for each histocompatibility locus and are developing methods f or marrow transplantation that can decrease morbidity and improve surv ival despite genetic disparity between donor and recipient.