Identification of DPB1 Permissive Unrelated Donors Is Highly Likely

•A DPB1 permissive–matched donor is possible in ~80% of patients with 10/10 matches•Minimal donor DPB1 typing is required to identify a young DPB1 permissive match•A productive search provides better match rates (>90%) regardless of T cell epitope group.

HLA-DPB1 permissive matching based on T cell epitope (TCE) groups should be considered when selecting among equally matched HLA-A, -B, -C, -DRB1 unrelated hematopoietic stem cell donors to improve patient survival. Previous studies have defined 3 TCE groups based on functional assays of alloreactivity. Combinations of donor and recipient DPB1 alleles with low immunogenic potential identify permissive donors, who provide no increased risk of mortality compared with DPB1–matched donors. To determine the likelihood of identifying a DPB1 permissive–matched (includes both allele-matched and DPB1-permissive mismatched) unrelated donor for patients with high-resolution matches at 10/10 HLA-A, -B,- C, -DRB1, and -DQB1 in the Be The Match Registry, preliminary search requests from United States' transplant centers for 595 DPB1-typed patients were evaluated for existence of a DPB1 permissive–matched donor, identified either among already typed donors or by prospective DPB1 typing. The baseline DPB1 permissive match rate was 69% and improved to 80% after additional donor DPB1 typing (median, 4 donors per patient). When seeking a 10/10-matched, young (18- to 32-year-old) donor in the registry, the probability of finding a DPB1 permissive–matched donor started lower at 59% and improved to 70% after additional DPB1 testing. Our results show that most patients with a 10/10 match can find a DPB1 permissive–matched donor.