Preliminary study on the changes of NKG2D expression and its role in children with infectious mononucleosis
Objective To investigate the mechanism of disturbed immunological function induced by Epstein-Barr virus(EBV) infection through evaluating NKG2D expressions in NK cells and CD8+ T lymphocytes from children with infectious mononucleosis.Methods Twenty-nine children with infectious mononucleosis (IM) and twenty-five age-matched healthy children were enrolled in the study.NKG2D/NKG2A expressions in NK cells and CD8+T lymphocytes,and NKG2D ligand MHC Ⅰ chain-related molecules A(MICA) and UL-16binding proteins (ULBP-1) expressions on CD14+ mononuclear cells (MC) were analyzed by flow cytometry.The concentrations of cytokines such as IL-7,IL-12,IL-15,IFN-γ,TGF-β and soluble MICA(sMICA) in plasma were determined by enzyme-linked immunosorbent assay (ELISA).Results (1) Compared with the control group,NKG2D expression was significantly decreased in both NK cells and CD8+T lymphocytes from children with IM (P＜0.05),especially in the three cases of suspected EVB-HLH children.(2)There was no difference in the expression of MICA and ULBP-1 in CD14+ MC between the children with IM and the normal control(P＞0.05).(3)The concentrations of IL-15 and TGF-β in plasma were lower than those of the control group (P＜0.05),while the levels of IL-7,IL-12,IFN-γ and sMICA were up-regulated(P＜0.05) in children with IM.(4)NKG2A expression in NKcells in children with IM was significantly increased as compared with healthy controls(P＜0.05),however,there was no differences in the expression of NKG2A in CD8+ T lymphocytes between the two groups (P＞0.05).Conclusion Remarkable down-regulated expressions of NKG2D in NK cells and CD8+T lymphocytes might be one of the factors causing disturbed immunological function in children with EBV infection,which might have a close relationship with abnormal cytokine milieu of IL-15 and IL-12or high concentration of sMICA. 
 
Key words: 
Epstein-Barr virus; Infectious mononucleosis; NKG2D