Enhanced T cell responses to IL-6 in type 1 diabetes are associated with early clinical disease and increased IL-6 receptor expression

Abstract

IL-6 is a key pathogenic cytokine in multiple autoimmune diseases including rheumatoid arthritis and multiple sclerosis, suggesting that dysregulation of the IL-6 pathway may be a common feature of autoimmunity. The role of IL-6 in type 1 diabetes (T1D) is not well understood. Here we show that STAT3 and STAT1 responses to IL-6 are significantly enhanced in CD4 and CD8 T cells from individuals with T1D compared to healthy controls. The effect is IL-6 specific as it is not seen with IL- 10 or IL-27 stimulation, two cytokines that signal via STAT3. An important determinant of enhanced IL-6 responsiveness in T1D is IL-6 receptor surface expression, which correlated with phospho-STAT3 levels. Further, reduced expression of the IL-6R sheddase ADAM17 in T cells from patients indicated a mechanistic link to enhanced IL-6 responses in T1D. Interestingly, IL- 6- induced STAT3 phosphorylation was inversely correlated with time from diagnosis, suggesting that dysregulation of IL-6 signaling may be a marker of early disease. Finally, whole-transcriptome analysis of IL-6 stimulated CD4+ T cells from patients revealed novel IL-6 targets involved in T cell migration and inflammation, including lymph node homing markers CCR7 and L-selectin. In summary, our study demonstrates enhanced T cell responses to IL-6 in T1D due in part to an increase in IL-6R surface expression. Dysregulated IL-6 responsiveness may contribute to diabetes through multiple mechanisms including altered T cell trafficking and indicates that individuals with T1D may benefit from IL-6 targeted therapeutic intervention such as being currently tested (NCT02293837).