Association of natural killer cells in allografts with transplant outcomes in patients receiving G-CSF-mobilized PBSC grafts and G-CSF-primed BM grafts from HLA-haploidentical donors

The aim of this study was to investigate the effects of natural killer (NK) cells on transplant outcomes in patients receiving G-CSF-mobilized PBSC grafts and G-CSF-primed BM grafts from HLA-haploidentical donors. Forty-one haploidentical allogeneic hematopoietic SCT patients were analyzed according to the NK cell concentration in relation to acute GVHD (aGVHD), chronic GVHD (cGVHD), TRM and leukemia-free survival. The patients receiving a higher dose of CD56 bright NK cells (>1.9 × 10 6 /kg) showed a higher incidence of grades II–IV aGVHD (hazard risk (HR), 2.872; P =0.022) and cGVHD (HR, 2.884; P =0.039). A higher CD56 dim /CD56 bri NK cell ratio (>8.0) was correlated with a decreased risk of III–IV aGVHD (HR, 0.290; P =0.065) and TRM (HR, 0.072; P =0.012), thereby increasing the rate of leukemia-free survival (HR, 0.174; P =0.007) after haploidentical transplantation without in vitro T-cell depletion. Our results suggest that a high allograft CD56 dim /CD56 bright NK cell ratio (>8.0) plays an important role in improving transplant outcomes. A higher dose of CD56 bright NK cells might be a predictor for a higher incidence of GVHD.