Effect of HLA class I or class II incompatibility in pediatric marrow transplantation from unrelated and related donors

The degree of histoincompatibility that can be tolerated, and the relative importance of matching at individual HLA class I and class II locus in bone marrow transplantation (BMT) has not been established. We hypothesized tha t matching for HLA-DR map nor be more important than matching for HLA-A or HLA-B in selection of a donor for successful BMT. We retrospectively analyz ed the outcomes of 248 consecutive pediatric patients who received allogene ic BMT from related donors (RD, n = 119) or unrelated donors (URD, n = 129) . HLA-A and HLA-B were serologically marched, and HLA-DRB1 were identical b y DNA typing in 69% of donor-recipient pairs. Most patients (89%) had hemat ologic malignancies; the rest had aplastic anemia or a congenital disorder. One HLA-A antigen mismatch was associated with a decrease in survival (p = 0.003) and a delay in granulocyte engraftment (P = 0.02) in recipients of RD marrow; as well as a decrease in survival (p = 0.02) and the development of severe acute graft-versus-host disease (GVHD) (p = 0.03) in recipients of URD marrow. One HLA-B antigen mismatch was associated with a decrease in the survival (P = 0.05) and the development of severe GVHD (p = 0.0007) in recipients of RD marrow. One HLA-DRB1 allele mismatch was associated only with a decrease in the survival (p = 0.0003) of recipients of RD marrow. Re sults of this study suggest that disparity in HLA-A and HLA-B antigens may nor be better tolerated than disparity in HLA-DR allele in allogeneic BMT. Further studies are warranted to confirm our results. (C) American Society for Histocompatibility and Immunogenetics, 2001. Published by Elsevier Scie nce Inc.