Abstract
Background: Little is known about the role of the CD56+ natural killer (NK) cell dose on the outcome of allogeneic peripheral blood stem cell transplantation (PBSCT). Recently, a higher dose of NK cells has been associated with a lower incidence of severe GVHD in a PBSCT setting. Therefore, the current study attempted to evaluate the effect of the NK cell dose on transplant outcomes, including non-relapse mortality (NRM) and infectious events, in an allogeneic PBSCT setting.
Methods and Materials: Sixty-one cytokine mobilized PBSC recipients from HLA-matched sibling donors were analyzed according to the infused dose of CD34+ cells and NK cells in relation to overall survival (OS), NRM, GVHD, and infectious events.
Results: The group of patients that received a higher dose of NK cells (≥ 5x107/Kg) showed a lower incidence of NRM (p=0.0186) and infectious events (p=0.0107). When confining the analysis to the group that received a CD34+ cell dose of ≥ 6x106/Kg, those patients that received a higher dose of NK cells exhibited a lower incidence of extensive chronic GVHD (p=0.0704). In a multivariate analysis using Cox’s regression model, a higher dose of NK cells was significantly associated with better transplant outcomes (for NRM, NK cell dose p=0.042, for CD34+ cell dose p=0.018; for infectious events, NK cell dose p=0.013, CD34+ cell dose 0.016; for bacterial infection, NK cell dose p=0.049). The group that received a higher NK cell dose also showed a faster immune recovery (p=0.046 for NK cell recovery, p=0.034 for helper T-cell recovery) in serial measurements of peripheral lymphocyte subsets at D+90, +180, and +365.
Conclusions: The present data suggests that a high dose of NK cells may play an important role in improving transplant outcomes, in terms of reducing NRM and infectious events together with CD34+ cells. The protective role of NK cells against infections may also be associated with a faster immune recovery after allogeneic PBSCT.
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