Fig. 1.
Cytokine-driven Th17 differentiation requires strong TCR engagement. Naïve TCR transgenic CD4+ T cells specific for the LCMV glycoprotein gp61–80 from Smarta-2 mice were cultured with spleen-derived DCs in the presence of the indicated antigen doses in the absence of exogenous cytokines (A and D Top) or in the presence of TGF-β (5 ng/ml) and rIL-6 (20 ng/ml) (B and D Bottom). After 5 d, cytokine production by expanded T cells was assessed by intracellular cytokine staining after PMA/ionomycin restimulation. Shown are the percentages of IFN-γ-, IL-4-, or IL-17-producing CD4+ T cells (A and B) and the expression levels (mean fluorescence intensity, M.F.I.) of TCR and CD40L assessed by flow cytometry after 5 and 20 h of culture, respectively (C). SD ≤2 for all points depicted. (D) Dot plot of IL-17+ and IFN-γ+ CD4 T cells cultured at the indicated antigen concentrations in the absence or presence of TGF-β and IL-6.