IRF4 and colitis: To specifically assess whether Th17 cell differentiation inducing and/or Th17 cell promoting cytokines are differentially regulated, we compared colonic gene expression profiles of IL-12 (Th1) and IL-1ß/IL-6/IL-23 (Th17) between colitis-protected Rag1−/−Irf4−/− and colitic IRF4-competent mice (Figure 3B).