Interleukin-35 Suppresses CD8.sup.+ T Cell Activity in Patients with Viral Hepatitis-Induced Acute-on-Chronic Liver Failure

Background Interleukin (IL)-35 is a newly indentified cytokine and induces immunotolerance via suppression of CD8.sup.+ T cell activity in chronic viral hepatitis. Aims To investigate the modulatory function of IL-35 to CD8.sup.+ T cells in viral hepatitis-induced acute-on-chronic liver failure (ACLF). Methods Fifty-five ACLF patients and 21 healthy controls were enrolled. Serum IL-35 concentration was measured by ELISA. Absolute accounts for T cells, immune checkpoint molecules, and cytotoxic molecules in CD8.sup.+ T cells were measured by flow cytometry and real-time PCR, respectively. Direct and indirect contact co-culture systems between CD8.sup.+ T cells and HepG2 cells were set up. The regulatory function of IL-35 to CD8.sup.+ T cells was assessed by measuring lactate dehydrogenase expression and cytokine production. Results Serum IL-35 concentration was elevated in ACLF patients and positively correlated with total bilirubin, but negatively correlated with prothrombin time activity. Peripheral CD8.sup.+ T cells showed exhausted phenotype in ACLF patients, which manifested as up-regulation of programmed death-1 (PD-1), cytotoxic T-lymphocyte-associated protein-4 (CTLA-4), and lymphocyte activation gene-3 (LAG-3) but down-regulation of perforin, granzyme B, and FasL. Recombinant IL-35 stimulation dampened cytotoxicity and interferon-[gamma] production in both direct and indirect contact co-culture systems. This process was accompanied by elevation of PD-1, CTLA-4, and LAG3, as well as reduction of perforin, granzyme B, and FasL in CD8.sup.+ T cells. Conclusion Elevated IL-35 suppressed both cytolytic and non-cytolytic activity of CD8.sup.+ T cells in ACLF patients.