Clinical Significance and Properties of IFN-γ+IL-17+ Th17 Cells in Liver Injury Associated with Chronic Hepatitis B Virus Infection

Introduction: Our previous study demonstrated that intrahepatic Th17 cells exacerbated the progression of chronic hepatitis B virus (HBV) infection. Meanwhile, we found a small group of IFN-γ and IL-17 double-positive Th17 cells (IFN-γ⁺IL-17⁺ Th17 cells) in liver tissues. This study aimed to investigate the clinical significance and properties of IFN-γ⁺IL-17⁺ Th17 cells in liver injury associated with chronic HBV infection. Methods: The frequencies of CD4⁺ Th cells, Tregs, and CD4⁺ T cells expressing specific chemokine receptors in the blood and liver tissues were detected using flow cytometry. The chemotaxis of C C chemokine receptor 5 (CCR5) and C-X-C chemokine receptor 3 (CXCR3) toward IFN-γ⁺IL-17⁺ Th17 cells and Tregs was evaluated by transwell chemotactic assay. Analyses of different variables were performed using GraphPad Prism v 5.01 and IBM SPSS Statistics 23.0. HBV-specific IFN-γ⁺IL-17⁺ Th17 cells were investigated using a cell stimulation assay with HBV antigens in vitro. Results: The frequencies of IFN-γ⁺IL-17⁺ Th17, Th17 cells, and Tregs in the blood were increased from normal controls to chronic hepatitis B (CHB) and acute-on-chronic liver failure (ACLF). The same trend could also be observed in CHB liver tissues compared to those in CHB blood specimens. Furthermore, the frequencies of IFN-γ⁺IL-17⁺ Th17 cells were positively associated with Th17 cells, Th17 cell-related cytokines (IL-17 and IL-6), HBV DNA load, and the levels of HBsAg, HBeAg, and ALT. The ratios of IFN-γ⁺IL-17⁺ Th17 cells to Tregs extremely decreased in ACLF blood specimens compared with those in CHB blood specimens. Additionally, CCR5 and CXCR3 were conducive to the recruitment of IFN-γ⁺IL-17⁺ Th17 cells and Tregs to liver tissue. Conclusions: IFN-γ⁺IL-17⁺ Th17 cells have Th17 cell-like properties in the progression of chronic HBV infection. CCR5 and CXCR3 facilitated the recruitment of IFN-γ⁺IL-17⁺ Th17 cells and Tregs to the liver. Importantly, the ratio of IFN-γ⁺IL-17⁺ Th17 cells to Tregs might be an effective assessment indicator of the severity of liver injury.