Mother Donors Improve Outcomes after HLA Haploidentical Transplantation: A Study by the Cellular Therapy and Immunobiology Working Party of the European Society for Blood and Marrow Transplantation

Transplacental trafficking of maternal and fetal cells during pregnancy establishes long-term reciprocal microchimerism in both mother and child. Consequently, the maternal immune system may become sensitized to paternal histocompatibility antigens. It has been hypothesized that mother's “exposure” to paternal HLA haplotype antigens during pregnancy may affect the outcome of hematopoietic stem cell transplantation (HSCT) when the mother serves as a donor for the child. In T cell-depleted HLA haploidentical HSCT, maternal donors have been associated with improved transplantation outcomes. The present retrospective multicenter study, conducted on behalf of the Cellular Therapy and Immunobiology Working Party of the European Society of Blood and Marrow Transplantation, involved 409 patients (102 pediatric and 307 adult) with acute leukemia who underwent HLA-haploidentical HSCT. The goal of the study was to evaluate the role of maternal donors in a large cohort of haploidentical transplantation recipients. Transplantation from maternal donors was associated with a lower relapse incidence in T cell-depleted HSCTs (hazard ratio [HR], 2.13; 95% confidence interval [CI], 1.16 to 3.92; P = .018) as well as in a limited series of unmanipulated in vivo T cell-depleted HSCTs (HR, 4.15; 95% CI, 0.94 to 18.35; P = .06), along with better graft-versus-host disease/relapse-free survival (GRFS) in T cell-depleted HSCT (HR, 1.67; 95% CI, 1.02 to 2.73; P = .04). These results indicate that the mother is the preferred donor to provide better GRFS in T cell-depleted HLA-haploidentical HSCT for acute leukemia.