The role of iTr35 cells in the inflammatory response and fibrosis progression of systemic sclerosis.

To evaluate the role of induced immunosuppressive T regulatory (iTr) 35 cells in systemic sclerosis (SSc)-related inflammation and fibrosis.68 SSc patients were enrolled in this study. Subsets of iTr35 and Tr1 were measured by flow cytometry. Interleukin (IL)-35 and IL-10 levels were measured using enzyme-linked immunosorbent assay (ELISA). Expressions of iTr35, Tr1, fibrosis-related genes, and proteins associated with signalling pathways were determined using immunofluorescence, western blot, and immunohistochemistry assays.In peripheral blood, the proportions of the iTr35 cells were higher and Tr1 cells were lower than the control group. Similarly, IL-35 expression was increased, while IL-10 levels were decreased. In fibroblasts from skin tissue, the expression levels of EBI3, IL-12Ap35, Foxp3, and IL-10 were decreased, but collagen I, TGF-β, α-SMA, and fibronectin levels were increased. Phosphorylated STAT3/6 were increased, but iTr35 and Tr1 cell levels were significantly decreased. When CD4+ cells were incubated with both rhIL-35 and rhIL-10, the cell numbers of iTr35 and Tr1 were greater than the same type of cells treated with rhIL-35 or rhIL-10 alone. However, the viability of conventional CD4+ T cells was decreased by gradually increasing iTr35 cells. Moreover, iTr35 cells affected α-SMA expression through the STAT3/6 signalling pathway.Both iTr35 and Tr1 cells are involved in SSc-related inflammation and fibrosis. IL-35 can induce iTr35 cells, showing a synergistic effect with IL-10. We also found that iTr35 cells can inhibit T cell proliferation and differentiation via the STAT3/6 signalling pathway, thereby causing fibrosis.