HLA-DP and allogeneic bone marrow transplantation.

HLA-DP typing is not routinely performed before allogeneic BMT. This highly polymorphic class II locus is implicated in immune response and DP molecules may act as transplantation antigens. HLA-DP incompatibilities contribute to MCL. In BMT performed between siblings, HLA-DP mismatches are rare and the role of such incompatibility in GVHD is probably lower than minor histocompatibility antigen disparity. In unrelated BMT, the rate of HLA-DP mismatches is high and DP incompatibility cannot be used as an exclusion criterion in the selection of unrelated donors. Even if in vitro studies show that the HLA-DP antigen may be the target for GVHD, analysis of large numbers of unrelated BMT shows that DP incompatibility is not a risk factor for acute GVHD.