Hla-DPB1 mismatch in HLA-A-B-DRB1 identical sibling donor stem cell transplantation and acute graft-versus-host disease.

BACKGROUND: The role of human leukocyte antigen (HLA)-DPB1 as a transplantation antigen is controversial. A higher incidence of acute graft-versus-host disease (aGVHD) has been described after unrelated donor bone marrow transplant when both HLA-DPB1 alleles were mismatched. METHODS: We investigated the impact of a single HLA-DPB1 mismatch after HLA-A-B-DRB1 identical sibling donor transplantation on aGVHD. We analyzed 627 adult patient-donor pairs and identified 30 pairs without HLA-DPB1 identity (4.78%). In 17 cases, the patient had an allele that was not shared by the donor. RESULTS: The cumulative incidence of grades II-IV aGVHD was higher in the HLA-DPB1 mismatched group (66.7% vs. 35.7%, p=0.012). The HLA-DPB1 mismatch was identified by multivariate analysis as an independent risk factor for aGVHD (p=0.020, RR=2.68, 95% CI: 1.73-3.62). CONCLUSIONS: HLA-DPB1 can mediate alloreactive responses. A single HLA-DPB1 mismatch increases the risk of aGVHD after sibling donor stem cell transplantation.