Supplementary Figure 6: DC-derived IL-6 is required for robust activation of STAT3 in T cells.

(a, b) Subcutaneous immunization with a peptide antigen in CFA induces similar amounts of serum IL-6 in control mice (Il6^flox/flox) and Il6^ΔDC mice. Control animals (Il6^flox/flox), Il6^-/- mice, and Il6^ΔDC mice were either injected with LPS (a) to induce systemic IL-6 or immunized subcutaneously with MOG(35-55) in CFA (b). Serum samples were collected 5 h after LPS injection or 1 day after subcutaneous immunization for the assessment of IL-6 by ELISA (n=3, SD, *P<0.04, One-way-ANOVA plus Tukey's multiple comparisons test). (c, d) RNA Seq analysis was performed in 2D2 T cells re-isolated from draining lymph nodes of control hosts (Il6^flox/flox) or Il6^ΔDC hosts after immunization with cognate MOG peptide. (c) Ingenuity pathway analysis was performed to evaluate the strength of STAT3 pathway activation in control primed (left panel) or Il6^ΔDC primed (right panel) 2D2 effector T cells. (d) Notably, in contrast to T cells primed in a control milieu, Il6^ΔDC primed T cells exhibited a weakened “STAT3” signature when their RNA profile was directly tested for the enrichment of STAT3 dependent genes by GSEA (see also Supplementary Tables).