No effect of HLA‐C mismatch after allogeneic hematopoietic stem cell transplantation with unrelated donors and T‐cell depletion in patients with hematological malignancies

HLA‐C mismatch in unrelated donor's hematopoietic stem cell transplantation (HSCT) has been associated with poor patient outcome. However, the impact of HLA‐C mismatch in the context of HSCT combined with in vivo T‐cell depletion remains unclear. We therefore performed a single‐center, retrospective analysis of the clinical outcome on patients with hematological malignancies treated with allo‐HSCT, who underwent T‐cell depletion. The majority of the patients (n=276) received a HLA‐A, HLA‐B, HLA‐DRB1‐matched graft that were either also HLA‐C matched (n=260), or patients with the permissive HLA‐C*03:03/03:04 mismatch (n=16), while the remaining patients (n=95) received a HLA‐C‐mismatched graft (excluding HLA‐C*03:03/03:04 mismatches). We did not observe any significant differences between the HLA‐C‐matched patients (including the permissive HLA‐C*03:03/03:04 mismatch) and the HLA‐C‐mismatched patients regarding cumulative proportion surviving, graft failure, relapse‐free survival, relapse, or acute graft‐versus‐host disease. Our data suggest that in the context of high dose T lymphocyte‐depleting agents, HLA‐C matching is not essential for patients with hematological malignancies.