目的：体外研究重组可溶性MHC Ⅰ类分子相关A（soluble MHC class Ⅰ chain-related gene A，sMICA）蛋白对自然杀伤细胞（natural killer cell, NK cell)表面活化性受体NKG2D（natural killer group 2 member D）的表达、杀伤白血病细胞的活性和分泌IFN-γ的影响。方法：免疫磁珠分选健康人外周血NK细胞，分为空白对照组、重组sMICA组（200、500、800 μg/L三亚组），相互作用24 h后，流式细胞术检测NK细胞NKG2D表达水平，LDH释放法检测NK细胞对白血病细胞K562的杀伤活性，ELISA法检测培养上清中IFN-γ的水平。结果：200、500、800 μg/L sMICA作用组与对照组相比，NK细胞表面NKG2D的表达均下调\[（68.79±6.87）%,（55.75±9.31）%、45.14±5.70）% vs（92.75±6.91）%，P<0.05或P<001\]，均抑制NK细胞杀伤白血病细胞K562的活性\[（18.67±2.35）%、（15.01±2.25）%、（7.33±2.52）% vs（36.33±251）%，P<0.05或P<001\]，均抑制IFN-γ的分泌\[ (164.48±22.48）、112.71±10.89）、（70.23±9.64） vs（313.72±16.06）pg/ml，P<0.05, P<0.01\]。结论：急性白血病细胞表面脱落的sMICA可下调NK细胞NKG2D的表达和IFN-γ的分泌，抑制了NK细胞对白血病细胞的杀伤活性。

Objective: To study the effect of recombinant soluble MHC class Ⅰ chain-related gene A (sMICA) protein on the expression of NKG2D (natural killer group 2 member D), cytotoxicity and secretion of IFN-γ of NK cells. Methods:NK cells were separated from normal adults by magnetic cell sorting (MACS) and then divided into 4 groups: recombinant sMICA groups (200, 500, 800 μg/L groups) and a control group. After 24 h of the interaction, the NKG2D was detected by the flow cytometry; the cytotoxicity of NK cells on K562 leukemia cells was detected by LDH release assay; and the concentration of IFN-γ in supernatant was determined by ELISA. Results:Compared with the control group, NK cell surface expressions of NKG2D in 200, 500, 800 μg/L sMICA groups were down-regulated (\[68.79±6.87\]%, \[55.75±9.31\]%, \[45.14±5.70\]% vs \[92.75±6.91\]%, P<0.05 or P<0.01); sMICA inhibited thecytotoxicity of NK cells on K562 leukemia cells (\[18.67±2.3\]%, \[15.01±2.25\]%, \[7.33±2.52\]% vs \[36.33±2.51\]%, P<0.05 or P<0.01), and decreased the secretion of IFN-γ of NK cells (\[164.48±22.48\], \[112.71±10.89\], \[70.23±9.64\] pg/ml vs \[313.72±16.06\] pg/ml, P<0.05 or P<001). Conclusion: The sMICA sheddingfrom the acute leukemia cell urface can reduce the NKG2D expression and IFN-γ secretion of NK cells, thereby inhibit the ytotoxic activity of NK cells against leukemia cells.

甘肃省科技支撑计划资助项目（No. 0804NKCA115）