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Recombinant soluble MICA protein negatively regulates the cytotoxic activity of NK cells on leukemia cells
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Abstract:
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<001). 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.
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Project supported by the Science and Technology supporting Program of Gansu Province (No. 0804NKCA115)
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