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 x 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. Bone Marrow Transplantation (2009) 44, 721-728; doi: 10.1038/bmt.2009.73; published online 20 April 2009