INTERLEUKIN-35 DOWNREGULATES THE IMMUNE RESPONSE OF EFFECTOR CD4 + T CELLS VIA RESTRICTING HIGH MOBILITY GROUP BOX-1 PROTEIN-DEPENDENT AUTOPHAGY IN SEPSIS.

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Background: Immunosuppression is critically involved in the development of sepsis and is closely associated with poor outcomes. The novel role of the anti-inflammatory cytokine IL-35 in sepsis was examined. Methods: Sepsis was induced by in C57BL/6 mice cecal ligation and puncture (CLP). The impacts of IL-35 on effector CD4 + T cells were investigated by examining cell proliferation and the Th1/Th2 ratio in the presence of recombinant IL-35 (rIL-35) or anti-IL-35 (EBI3). The regulatory effect of IL-35 on autophagy was evaluated by measuring autophagy markers and autophagic flux in CLP mice in vivo and in activated effector CD4 + T cells in vitro . Results: IL-35 levels were significantly increased in the serum and spleens of septic mice. rIL-35 administration after CLP further decreased proliferation and the Th1/Th2 ratio in effector CD4 + T cells and significantly shortened the survival time. Sepsis-induced autophagy activation was protective in effector CD4 + T cells and was blocked by rIL-35. The inhibitory effect of IL-35 on autophagy was observed in activated effector CD4 + T cells in vitro , and this effect was mediated by restricting high mobility group box-1 protein (HMGB1) translocation. Conclusion: IL-35 is an immunosuppressive cytokine that impairs CD4 + T-cell proliferation and differentiation in sepsis, and the effect might be mediated by reducing HMGB1-dependent autophagy.