Non-CD34⁺ Cells, Especially CD8⁺ Cytotoxic T Cells and CD56⁺ Natural Killer Cells, Rather Than CD34 Cells, Predict Early Engraftment and Better Transplantation Outcomes in Patients with Hematologic Malignancies after Allogeneic Peripheral Stem Cell Transplantation

The effect of the transplant dose of each cell subset on engraftment kinetics and transplantation outcomes was evaluated in HLA-identical allogeneic peripheral blood stem cell transplantation (PBSCT). Sixty-nine patients were included in this retrospective study. Engraftment kinetics, transplantation outcomes, and immune reconstitution up to 1 year after transplantation were analyzed according to the transplant dose of CD34⁺ and non-CD34⁺ cells, including natural killer (NK) cells and CD8⁺ cytotoxic T (Tc) cells. An accelerated neutrophil engraftment was strongly associated with a higher transplant dose of NK cells (12 versus 16 days, P < .001) and Tc cells (13 versus 16 days, P < .001) but not CD34⁺ cells (P = .442). Survival analyses revealed a favorable prognosis for patients who received a higher dose of non-CD34⁺ cell subsets, rather than CD34⁺ cells, in terms of overall survival (OS; P = .024 for NK cells and .050 for Tc cells) and nonrelapse mortality (NRM; P = .005 for NK cells, .060 for Tc cells). In addition, a higher transplant dose of NK and Tc cells was correlated with a faster lymphoid reconstitution. In multivariate analyses, rapid neutrophil engraftment was correlated with a higher transplant dose of NK cells (P = .001) and Tc cells (P = .004). Moreover, an increased OS was associated with the NK cell dose (P = .007) and chronic graft-versus-host disease (P = .009), whereas a decreased NRM was associated with the NK dose (P = .024). In conclusion, in a PBSCT setting, a higher transplant dose of NK and Tc cells accelerated neutrophil engraftment, improved the immune reconstitution, and decreased NRM, thereby increasing OS after allogeneic PBSCT.