Anti-HLA antibodies in double umbilical cord blood transplantation

Recent registry data suggest that host-versus-graft alloreactions mediated by anti-donor HLA antibodies in recipients of adult allogeneic hematopoietic stem cells or single-unit umbilical cord blood (UCB) contribute to the risk of graft failure. The present study evaluated the impact of anti-HLA antibodies on engraftment and unit predominance in 126 double-UCB (dUCB) recipients. Eighteen dUCB recipients were identified with at least 1 of 2 UCB units recognized by anti-HLA antibodies directed against donor-directed HLA-specific antibodies (DSAs). Overall, 9 of 12 patients who had DSAs against 1 of the 2 UCB units composing the graft and 5 of 6 patients who had DSAs against both units engrafted. The cumulative incidence of engraftment was similar in patients with and without DSAs (83% vs 78%). Thus, our data do not support a negative effect of anti-HLA antibodies on engraftment, at least in the setting of cyclosporine and mycophenolate mofetil and the conditioning regimens used at the University of Minnesota, and argue against routine screening for use in graft selection before dUCB transplantation. Further studies are needed to fully understand the value of anti-HLA antibody testing in dUCB graft selection and its impact on transplantation outcomes.