Rapid Recovery of CD3+CD8+ T Cells on Day 90 Predicts Superior Survival after Unmanipulated Haploidentical Blood and Marrow Transplantation

BACKGROUND Rapid immune reconstitution after allogeneic hematopoietic stem cell transplantation (allo-HSCT) is significantly associated with lower infection, relapse and possibly secondary malignancy rates. The aim of this study was to investigate the role of peripheral lymphocyte subsets, especially CD3+CD8+ cytotoxic T cell recovery, in predicting transplant outcomes, including the overall survival (OS) and non-relapse mortality (NRM) rates after unmanipulated haploidentical blood and marrow transplantation (HBMT). METHODS Peripheral blood samples were obtained from 214 HBMT recipients with hematological malignancies. The peripheral lymphocyte subsets (CD3+ T cells, CD3+CD4+ helper T cells, CD3+CD8+ cytotoxic T cells, and CD19+ B cells) were analyzed by flow cytometry at days 30, 60, 90, 180, 270 and 360 after HBMT. RESULTS The CD3+CD8+ cytotoxic T cell recovery at day 90 (CD3+CD8+-90) was correlated with bacterial infection (P = 0.001), NRM (P = 0.001), leukemia-free survival (LFS, P = 0.005), and OS (P = 0.001) at a cutoff value of 375 cells/μL CD3+CD8+ T cells. The incidence of bacterial infection in patients with the CD3+CD8+-90 at ≥375 cells/μL was significantly lower than that of cases with the CD3+CD8+-90 at <375 cells/μL after HBMT (14.6% versus 41.6%, P<0.001). Multivariate analysis showed the rapid recovery of CD3+CD8+ T cells at day 90 after HBMT was strongly associated with a lower incidence of NRM (HR = 0.30; 95% CI: 0.15-0.60; P = 0.000) and superior LFS (HR = 0.51; 95% CI: 0.32-0.82; P = 0.005) and OS (HR = 0.38; 95% CI: 0.23-0.63; P = 0.000). CONCLUSION The results suggest that the rapid recovery of CD3+CD8+ cytotoxic T cells at day 90 following HBMT could predict superior transplant outcomes.