Impact of Lymphocyte Subsets of Grafts on the Outcome of Haploidentical Peripheral Blood Stem Cell Transplantation

The contribution of lymphocyte subset composition of the graft on the outcomes following haploidentical peripheral blood stem cell transplantation (haploPBSCT) is not fully elucidated. We retrospectively analyzed 314 patients with hematological malignancies who underwent haploPBSCT from 2016 to 2020 in our center. We obtained a cutoff value of CD3+ T cell dose (2.96 × 10(8)/kg) that separated the risk of II–IV acute graft-versus-host disease (aGvHD) and divided patients into the low CD3+ T cell dose group (CD3+ low) and the high CD3+ T cell dose (CD3+ high) group. Significantly higher incidences of I-IV aGvHD, II–IV aGvHD, and III–IV aGvHD were identified in the CD3+ high group (50.8%, 19.8%, and 8.1% in the high group, 23.1%, 6.0%, and 0.9% in the low group, P < 0.0001, P = 0.002, and P = 0.02, respectively). We found that CD4+ T cell and its naïve and memory subpopulations of grafts had a significant impact on aGvHD (P = 0.005, P = 0.018, and P = 0.044). Besides, we found an inferior reconstitution of natural killer (NK) cells in the CD3+ high group than in the low group within the first-year posttransplant (239 cells/μL vs 338 cells/μL, P = 0.0003). No differences in engraftment, chronic GvHD (cGvHD), relapse rate, transplant-related mortality (TRM), and overall survival (OS) were identified between the two groups. In conclusion, our study found that a high CD3+ T cell dose led to a high risk of aGvHD and inferior reconstitution of NK cells in the haploPBSCT setting. In the future, carefully manipulating the composition of lymphocyte subsets of grafts might reduce the risk of aGvHD and improve the transplant outcome.