Figure 4.

Multiple Th17 cell subsets but not bona fide Th1 cells are critically dependent on the expression of functional IRF4 in Rag1 ^−/− mice with established T cell driven colitis. Rag1 ^−/− and Rag1 ^{− / −} Irf4 ^−/− mice were injected i.p. with 1 × 10⁶ naïve (CD4⁺CD25⁻) T cells. When colitis was established in Rag1 ^−/− mice five to six weeks after T cell transfer, both Rag1 ^−/− and Rag1 ^{− / −} Irf4 ^−/− mice were sacrificed, and the cytokine profile of transferred CD4⁺ T cells (CD3⁺CD4⁺) in the MLN (A) and in the cLP (B) was analyzed by intracellular flow cytometry after ex vivo restimulation. Frequencies of IFN-γ ⁺IL-17a⁻, IFN-γ ⁺IL-17a⁺, IFN-γ ⁻IL-17a⁺ (upper panel) and GM-CSF⁺IL-17a^- GM-CSF⁺IL-17a⁺ GM-CSF⁻IL-17a⁺ (lower panel) expressing cell populations within the CD4⁺ T cell pool were analyzed. One representative flow cytometry plot is shown for every experimental group. Data are combined from two individual experiments (Rag1 ^−/− n = 7; Rag1 ^{− / −} Irf4 ^−/− n = 8). Data were analyzed by Student’s t test and are shown as mean ± SEM. ns, not significant. *p < 0.05.