HLA-DPB1 and hematologic disorder: Permissiveness to DPB1 mismatches is now a well-established phenomenon in HSCT, both clinically (14, 15) and in vitro (9, 12, 41), with permissive mismatches (i.e., those involving two alleles of the same T cell epitope, TCE, group, and that share structural similarities) conferring significantly lower risks of relapse without significant increases in non-relapse mortality when compared to DPB1 allele matches after HSCT for hematologic malignancies (14, 42, 43).