Fig 1: IL-6 trans-signaling drives ECM expression in fibroblasts. (A–C) CD4+ T cells from peripheral blood were activated with CD3/CD28 Dynabeads for 3 d, n = 3 per group; data are representative of 2 independent experiments. (A) Representative FACS plot of HLA-DR and IL6Ra staining. (B) Quantification of HLA-DR and IL6Ra expression by CD4+ T cells. (C) sIL6Ra levels in CD4 T cell supernatant, n.d. not detected. (D) Relative expression of IL-6 signaling genes in fibroblasts, n = 3 to 5 per group. (E) IL6 expression by HFF and SSc fibroblasts incubated with IFNa2, n = 7 (HFF) and 4 (SSc1-3) per group; data were combined from 2 independent experiments. (F and G) IL6 and TNC expression when SSc1 and HFF fibroblasts were incubated with IL6 and/or sIL6Ra for 4 h, n = 4 per group; data are representative from 2 independent experiments. (H) IL6 and ECM gene expression by HFF and SSc fibroblasts in response to hyper-IL6 for 4 h, n = 4 per group. (I) Model of IL-6 trans-signaling in scleroderma skin grafts. tmIL6Ra is cleaved by ADAM17 (39), thereby generating the soluble receptor. IL6 expression is induced by type I interferon, which can then bind sIL6Ra and gp130 on fibroblasts to drive ECM expression along with IL6 positive feedback loop. Data are mean ± SD (*P < 0.05, **P < 0.01, ***P < 0.001, and ****P < 0.0001) analyzed with one-way ANOVA with Tukey multiple-comparisons test (D, F, and G) and unpaired two-tailed Student t test (B, E, and H).