Effect Of KLRG1 Receptor On NK Cells In Chronic Hepatitis B Virus Infection

ObjectiveHepatitis B virus(HBV)infection is a worldwide epidemic with the highest prevalence of infections in Africa and Asia.According to the latest epidemiological survey that 2 billion people in the world have been infected with HBV,of which 240 million are chronic HBV infections.About 650,000 people die of HBV-infected liver failure,cirrhosis and hepatocellular carcinoma every year(Hepatocellular Carcinoma,HCC).Chronic infection with hepatitis B virus is the result of viral replication and impaired host immune interactions.Due to the impaired innate immune and adaptive immune system of chronic hepatitis B virus infection,the virus cannot be effectively eliminated,leading to persistent chronic infection.Innate immunity plays a role in the early stage of HBV infection and induces subsequent specific immune responses.Natural killer cells(NK cells)are important virus-responsive cells for innate immune as clearance of intracellular pathogens and abnormal cells.They play a role mainly through the secretion of cytokines and killer functions.Killer cell lectin-like receptor subfamily G member 1(KLRG1)was first found on rat mucosal mast cell line RBL-2H3 and was considered as an inhibitor of inflammatory mediator release.KLRG1 are mainly expressed in NK cells and T cells in humans.It has been reported that KLRG1 expression on peripheral blood NK cells in patients with hepatitis C reduces the number of NK cell and impaired its function.Its mechanism is mainly to inhibit the proliferation of NK cells,promote the apoptosis of NK cells and reduce NK cell inflammatory cytokines.The purpose of this study was to investigate the effect of KLRG1 expression on NK cell function in chronic hepatitis B virus infection.Methods1.Peripheral Blood Mononuclear Cell(PBMC)from Peripheral Blood of 120 Chronic Hepatitis B Virus Infected and 19 Healthy individuals.Flow Cytometry was used to detect the proportion of NK cells in lymphocytes and KLRG1+NK cells proportion;2.PBMCs from HBV-infected and healthy controls were stimulated with propylene glycol methyl ether acetate(PMA)and ionomycin in vitro,and the frequency of NK cells expressing IFN-?in PBMC of peripheral blood was measured.3.The correlation between KLRG1 expression and IFN-?secretion on NK cells in peripheral blood PBMCs was analyzed..Results1.Detection of NK cells frequency in peripheral blood:The proportion of NK cells in peripheral blood lymphocytes from chronic hepatitis B virus infected patients(120 cases)and healthy control group(19cases)was measured by flow cytometry and the results showed that the frequency of NK cells in the group of HBV infection(16.92±7.9%)was not significantly different from that in healthy controls(10.57±6.5%)(P=0.3297).;2.Analysis of the frequency of KLRG1~+NK cells in peripheral blood:The proportion of KLRG1~+NK cells in peripheral blood PBMC of chronic hepatitis B virus infected(120 cases)and healthy control group(19 cases)was detected by flow cytometry.The proportion of KLRG1~+NK cells in the HBV infection group was significantly higher than that in the healthy control group(31.60±17.9%)(49.43±21.2%)(P<0.001).3.Analysis of the frequency of NK cells secreting IFN-?in peripheral blood PBMCs:The frequency of NK cells secreting IFN-?in peripheral blood PBMCs of patients with chronic hepatitis B virus infection(28 cases)and healthy control group(12 cases)was detected.The frequency of NK cells secreting IFN-?in peripheral blood PBMC of HBV-infected group was significantly lower than that of healthy control group(t=4.801,P<0.0001).Further analysis found that the frequency of KLRG1~+NK cells secreting IFN-?in the control group was significantly lower than that of KLRG1~-NK cells(t=8.586,P<0.0001);the frequency of KLRG1~+NK cells secreting IFN-?in the HBV-infected group were also significantly less than that of KLRG1~-NK cells(t=4.801,P<0.0001).Compared with the control group,the frequency of KLRG1~+NK cells and KLRG1~-NK cells secreting IFN-?in the HBV infection group were significantly decreased(t=2.753,P=0.009;t=6.391,P<0.0001).4.Correlation analysis between KLRG1 expression and IFN-?secretion in NK cells in peripheral blood PBMC of HBV infected patients:In order to further clarify the relationship between KLRG1 expression and IFN-?secretion on NK cells,we used GraphPad Prism 6.03 software The correlation between the two groups of variables was analyzed.The results showed that there was a significant negative correlation between the expression of KLRG1 on NK cells and the secretion of IFN-?in peripheral blood PBMC of infected persons(correlation coefficient-0.5470,P=0.0026).ConclusionHepatitis B virus infection can increase the expression of KLRG1 in NK cells and further reduce the secretion of IFN-?in NK cells,which may be an important factor in the chronic infection of HBV.