Impact of Donor-Recipient Major ABO Mismatch on Allogeneic Transplantation Outcome According to Stem Cell Source

Major ABO incompatibility between donor and recipient is not considered a barrier to successful allogeneic hematopoietic stem cell transplantation (HSCT), even if it can be associated with several immunohematologic complications. Nevertheless, conflicting data still exist as to its influence on graft-versus-host disease (GVHD) incidence, relapse rate, and survival. To further investigate the relevance of ABO major mismatch on transplantation outcome, we retrospectively analyzed results from 414 patients with major or major/minor ABO-mismatched bone marrow (BM), peripheral blood (PB), and cord blood (CB) allogeneic HSCT. Transplantation outcome was assessed by comparison with results from a 395-patient ABO-compatible population with similar characteristics. Median time to red cell transfusion independence was significantly longer in ABO-incompatible BM recipients (median time, 63 days vs 41 days; P =.001), with faster disappearance of antidonor IgM hemagglutinins in unrelated recipients (median time, 36 days vs 44 days; P = .03) and in patients with grade ≥II acute GVHD (aGVHD) (median time, 35 days vs 59 days ; P = .001). In PB stem cell (PBSC) and CB transplantation, erythroid reconstitution was not significantly delayed, regardless of donor type or presence of aGVHD. A slight correlation between ABO incompatibility and GVHD incidence was found in PBSC recipients when considering grade ≥II aGVHD incidence (63% in ABO-matched HSCT vs 83% in ABO-mismatched HSCT; P = .055), but this was not confirmed in multivariate analysis. In patients with acute leukemia, multivariate analysis revealed an association between major ABO mismatch and decreased relapse rate with borderline statistical significance (hazard ratio, 0.65; P = .04). Major ABO incompatibility mainly, if not exclusively, affects red blood cell engraftment after BM transplantation. Somewhat surprisingly, the graft-versus-plasma cell effect seems to be confined to this stem cell source.