Background:The dose of certain cell types in allografts affects engraftment kinetics and clinical outcomes after allogeneic stem cell transplantation (SCT).Hence,the present study investigated the association of cell compositions in allografts with outcomes after unmanipulated haploidentical SCT (haplo-SCT) for patients with acquired severe aplastic anemia (SAA).Methods:A total of 131 patients with SAA who underwent haplo-SCT were retrospectively enrolled.Cell subsets in allografts were determined using flow cytometry.To analyze the association of cellular compositions and outcomes,Mann-Whitney U nonparametric tests were conducted for patient age,sex,weight,human leukocyte antigen mismatched loci,ABO-matched status,patient ABO blood type,donor-recipient sex match,donor-recipient relationship,and each graft component.Multivariate analysis was performed using logistic regression to determine independent influence factors involving dichotomous variables selected from the univariate analysis.Results:A total of 126 patients (97.7％) achieved neutrophil engraftment,and 121 patients (95.7％) achieved platelet engraftment.At 100 days after transplantation,the cumulative incidence of Ⅱ-Ⅳ acute graft-versus-host disease (GVHD) was 32.6％.After a median follow-up of 842 (range:124-4110) days for surviving patients,the cumulative incidence of total chronic GVHD at 3 years after transplantation was 33.7％.The probability of overall survival at 3 years was 83.0％.Multivariate analysis showed that higher total doses of CD14+ (P =0.0l 8) and CD34+ cells (P ＜ 0.00l) were associated with a successful platelet engraftment.A successful platelet was associated with superior survival (P ＜ 0.001).No correlation of other cell components with outcomes was observed.Conclusions:These results provide evidence and explain that higher doses ofCD34+ and CD14+ cells in haploidentical allografts positively affect platelet engraftment,contributing to superior survival for patients with SAA.