Abstract: Objective：To explore the functional different natural killer (NK) cell subsets through the expression of killer immunoglobulin receptor (KIR) and CD57 on NK cells. Methods: From May 2012 to June 2012, the peripheral blood samples of 10 related healthy donors for hematopoietic stem cells transplantation were collected to analyze KIR, CD57 expression and the intracellular cytokines of interferon-γ(IFN-γ), and the CD107a secreted by NK cells through 6-colour flow cytometer to compare the cytokine secretion and cytotoxic function among different NK subset. Results: The expression of CD57 on NK cells were significantly higher than those of KIR on NK cells［(60.71%±5.71%) vs. (24.47%±3.95%), P<0.001］. All the NK cells were separated into KIR+CD57－, KIR+CD57+, KIR－CD57+, KIR－CD57－ cells based on the expressions of KIR and CD57. The proportions of KIR－CD57+ NK cells (43.03%±5.70%) and KIR－CD57－NK cells (32.45%±5.50%) among NK cells were comparable （P=0.189）, and were higher than those of KIR+CD57+ NK cells (17.67%±3.39%) and KIR+CD57－ NK cells (6.69%±0.95%). Further functional experiments demonstrated that the cytotoxic function and IFN-γ cytokine secretion of CD57+ NK cells and KIR+ NK cells were comparable, which were significantly lower than those of CD56^bri NK cells (P=0.046 and 0.035, respectively), but were equal to those of CD56^dim NK cells. The cytotoxic function and the IFN-γ secretion of KIR－CD57－ NK cells (46.22%± 9.24% and 23.41%±5.82%) were significantly higher than those of the other NK subsets including KIR+CD57－ NK cells，KIR- CD57+ NK cells and KIR+CD57+ NK cells, which were similar to those of CD56^bri NK cells. The cytotoxic function and IFN-γ secretion of KIR+CD57- NK cells were lower than those of KIR－CD57－ NK cells, but were higher than those of CD57+ NK cells, whether KIR positive or negative. The cytotoxic function and IFNγ secretion were similar between KIR+CD57+ and KIR－CD57+ cells. Conclusion: The expressions of KIR and CD57 are correlated with the function of NK cells. Therefore, CD57+ cells might be the end stage of NK cells, KIR－CD57－ NK cells might be the early stage of NK cells, however, KIR+CD57－ showed to be the intermediate stage of the NK cells.

Key words: Killer cells, natural, Receptors, KIR, Antigens, CD57, Lymphocyte subsets