Incidence and clinical relevance of donor-derived recipient-specific anti-HLA antibodies in haploidentical hematopoietic stem cell transplantation: a retrospective study

Donor-derived recipient-specific anti-HLA antibodies (RSAs) are rarely investigated in allogeneic hematopoietic stem cell transplantation (allo-HSCT). In this retrospective study, 185 haploidentical donor-recipient pairs were consecutively analyzed. Anti-HLA antibodies were detected in eight donors (4.3%) and 31 recipients (16.8%), with only one donor (0.5%) harboring RSAs. Donors were predominantly young, male, and transfusion-naïve, which likely contributed to the low antibody prevalence. No association was observed between donor antibody positivity and graft rejection or severe acute graft-versus-host disease (GVHD). However, recipients of antibody-positive grafts showed higher rates of Epstein-Barr virus (EBV) reactivation and transfusion refractoriness. Our findings suggest that donor-derived HLA antibodies, particularly RSAs, are infrequent and clinically limited under current haploidentical donor selection and immunosuppressive strategies, but may subtly influence post-transplant immune recovery.