Figure 2. Th17 Cells Respond to IL-12 to Rapidly Upregulate IFN-γ and Extinguish IL-17.

OT-II CD4⁺ T cells were cultured with irradiated Il12b^−/− splenic feeder cells under Th17-polarizing condition for 7 days (1° culture, top panel), and a fraction of recovered T cells were restimulated and analyzed for intracellular IL-17A and IFN-γ as in Figure 1. The remaining T cells were cultured again with irradiated Il12b^−/− splenic feeder cells in the presence of indicated cytokine(s), anti-IFNγ, anti-IL-4, and OVAp as in Figure 1 for 7 days (2° culture, middle panel), and a fraction was reanalyzed for intracellular cytokine expression. The remaining recovered cells from secondary cultures were recultured under identical cytokine conditions for a third and fourth round (3° and 4° cultures, bottom panel), then analyzed for intracellular IL-17A and IFN-γ after PMA-ionomycin activation as before. Numbers in quadrants indicate percentage of total CD4⁺ cells in each. Data are representative of at least three experiments.