Up-regulation Of LAG-3 On Activated CD8+t Cell In Chronic HCV Infection Contributing To Virus Persistence

Background: HCV is one of serious public-health problem that can lead to severe liver disease.The rate at which HCV infected individual progress to CHC is approximately 80-85%.In recent years,many studies have found that Chronic Hepatitis C is mainly due to T cell exhaustion,one of characteristics is inhibitory receptors expression upregulation.LAG-3 is a new inhibitory receptors that can suppress proliferation?secrete and cytotoxicity of T lymphocyte cell,but the mechanism is unclear.Objective: This study tries to reveal whether inflammatory microenvironment can upregulate LAG-3 expression,and the importance and initial mechanism of LAG-3 on immune regulation in CHC patients.Methods: 1.Collected blood sample from intravenous drug users;According to the results of the patients' anti-HCV antibody and HCV RNA divided them into two groups:Chronic infection group and Healthy control.2.Plasma IL-12p70,IL-10 and TGF-?level were measured by ELISA;3.The expression of LAG-3?T-bet and HLA-DR and intracellular IL-10 and IFN-?level were detected by flow cytometry.4.In vitro,PBMCs(1*106/well)from health control were treated with different stimulation condition,detection of LAG-3 expression on CD8+T cell were identified by flow cytometry.Results: 1.The expression of LAG-3 in CHC patients was dramatically elevated on CD8+T cell(p=0.012)compared to health control,and was significantly positively correlated with the viral load(p=0.036,r=0.484);2.Compared with health control,the level of intracellular IFN-?in CD8+T cell was significantly higher in CHC patients(p=0.04),the level of intracellular IL-10 had no significant difference(p=0.33);3.In CHC patients,the level of intracellular IFN-?in CD8+LAG-3+T cell was significantly lower than in CD8+LAG-3-T cell(p=0.02),in Healthy control,there is no significantly difference;4.Compared with healthy control,plasma IL-10(p=0.001)and IL-12(p=0.019)level were significantly increased and plasma TGF-?(p=0.01)level were significantly decreased in CHC patients;r IL-12 could up-regulate LAG-3 on CD8+T cell relying on TCR activation(p=0.002),r TGF-?could down-regulate LAG-3 on CD8+T cell relying on TCR activation(p=0.002).5.In CHC patients,the level of HLA-DR in CD8+LAG-3+T cell was significantly higher than in CD8+LAG-3-T cell(p<0.001),the level of T-bet in CD8+LAG-3+T cell was significantly lower than in CD8+LAG-3-T cell(p=0.037);the level of T-bet in activated CD8+LAG-3+T cell was significantly lower than in activated CD8+LAG-3-T cell(p=0.005);6.In CHC patients,LAG-3 expression was significantly negatively correlated with T-bet expression on activated CD8+T cell(p=0.005,r=-0.943).Conclusions: 1.Plasma IL-10 and IL-12 level were significantly increased and plasma TGF-?level were significantly decreased in CHC patients.2.LAG-3 expression on CD8+T cell was up-regulation 3.The expression of LAG-3 in CHC patients was significantly positively correlated with the viral load 4.This study suggests that activated immune cell can secrete a variety of cytokines following infection with HCV,the inflammatory microenvironment can increase LAG-3 expression on CD8+T cells,leading to influence T-bet expression and secreting intracellular IFN-?.This may be one of the reason of T cell exhaustion.5.These findings provide the importance and initial mechanism of LAG-3 on immune regulation in CHC patients,and a new sight to know about HCV chronic infection and therapy.