Overexpression of ascitic interleukin-35 induces CD8+ T cell exhaustion in liver cirrhotic patients with spontaneous bacterial peritonitis

Interleukin (IL) -35 induces immunotolerance by suppression of CD8+ T cells during chronic infections and cancers. In the present study, we amined to investigate the role of IL-35-mediated regulation of CD8+ T cells in patients with liver cirrhosis. Seventy-one patients with liver cirrhosis (46 patients with untainted ascites and 25 patients with spontaneous bacterial peritonitis [SBP]) and 22 controls were enrolled. Plasma and ascitic IL-35 levels were measured using ELISA. Peripheral and ascitic CD4+ and CD8+ T cells were purified to investigate their functional phenotypes. IL-35-stimulated CD8+ T cells were cultured with HepG2 cells in direct and indirect contact systems. Lactate dehydrogenase expression and cytokine secretion were measured to determine the cytotoxicity of CD8+ T cells. Plasma IL-35 was elevated in patients with liver cirrhosis, and ascitic IL-35 levels were higher in the SBP group than in the untainted ascites group. No significant differences in transcription factor expression or cytokine production in peripheral and ascitic CD4+ T cells were observed among groups. In the SBP group, ascitic CD8+ T cells expressed decreased cytotoxic molecules, along with the reduced secretion of interferon-γ and tumor necrosis factor-α when compared with the untainted ascites group. IL-35 stimulation suppressed ascitic CD8+ T cell cytotoxicity and cytokine production in both direct and indirect contact culture systems. This process was accompanied by decreased cytotoxic molecule expression and increased immune-checkpoint molecules in ascitic CD8+ T cells. The present findings revealed that overexpression of ascitic IL-35 dampened the cytotoxicity of CD8+ T cells in liver cirrhotic patients with SBP.