Influence of interleukin-35 on peripheral CD8+ T cell function in patients with acute-on-chronic liver failure

Objective To investigate the serum level of interleukin-35 ( IL-35) and its influence on CD8+T cell function in patients with acute-on-chronic liver failure ( ACLF) . Methods A total of 28 patients with ACLF who attended Hainan Provincial People's Hospital from November 2018 to April 2019 and 14 healthy controls were enrolled in this study. ELISA was used to measure the serum level of IL-35. Peripheral CD8+T cells were separated and stimulated with recombinant human IL-35, and real-time quantitative PCR was used to measure the mRNA expression of perforin, granzyme B, and granulysin in CD8+T cells; flow cytometry was used to measure the expression of programmed death-1 ( PD-1) and cytotoxic T-lymphocyte-associated antigen 4 ( CTLA-4) in CD8+T cells. The direct-and indirect-contact co-culture systems were used for the co-culture of HLA-A2-restricted CD8+T cells and HepG2 cells, and after recombinant human IL-35 was added, the percentage of target cell death and the secretion of cytokines were measured to evaluate the changes in the cytolytic and noncytolytic activities of CD8+T cells. The two-independent-samples t test or the paired t-test was used for comparison of normally distributed continuous data between two groups, and the Mann-Whitney U test was used for comparison of non-normally distributed continuous data between two groups; the Spearman correlation analysis was performed to investigate correlation. Results Compared with the health controls, the patients with ACLF had a significant increase in the serum level of IL-35 [72. 32 ( 54. 04-111. 30) pg/ml vs 46. 00 ( 27. 02-82. 29) pg/ml, Z = 2. 184, P = 0. 020]. CD8+T cell exhaustion was observed in ACLF patients, with the manifestations of reductions in the relative mRNA expression of perforin and granzyme B, increases in the percentages of PD-1+or CTLA-4+CD8+T cells, and reductions in the cytolytic ( induction of target cell death) and noncytolytic ( secretion of interferon-γ) functions of CD8+T cells ( all P < 0. 05) . After the stimulation with recombinant IL-35, both ACLF patients and healthy controls had significant reductions in the relative mRNA expression of perforin and granzyme B in CD8+T cells, significant increases in the percentages of PD-1+orCTLA-4+CD8+T cells, and significant reductions in the cytolytic and noncytolytic functions of CD8+T cells ( all P < 0. 05) . Conclusion Elevated IL-35 can suppress the cytolytic activity of CD8+T cells in ACLF patients, suggesting that IL-35 might induce the exhaustion of cellular immune function in ACLF patients.