Which factors influence the development of GVHD in HLA-matched or mismatched transplants?

The sheer diversity of HLA alleles makes the probability of finding matched unrelated donors for patients requiring hematopoietic cell transplantation (HCT) a complex situation. New evidence suggests that mismatching at certain HLA loci may provide a greater benefit in terms of graft-versus-leukemia effect than other mismatches when HLA-matched donors are not available. This review summarizes the current understanding of HLA matching requirements for unrelated donor HCT.