Fig. 2. TGFβ1 signaling maintains Ahr expression in T_H17 cells, while it opposes IL-23-driven conversion into pathogenic T_H17 cells.

a Naive CD4⁺ T cells were cultured 3 days under nonpathogenic T_H17-polarizing conditions (TGFβ1+IL-6) in the absence or presence of FICZ and then stained intracellularly for IL-17A and IL-22 (first culture). A fraction of recovered cells cultured without FICZ was re-stimulated for additional 3 days with TGFβ1, IL-6 plus IL-23, or only IL-23, with or without FICZ stimulation (second culture). b Frequencies of IL-17A⁺ and IL-22⁺ cells after the second culture shown in a. c qPCR analysis of Ahr, Cyp1a1, Ahrr, Il17a, and Tbx21 of naive CD4⁺ T cells cultured under nonpathogenic T_H17-polarizing conditions (TGFβ1+IL-6) for 3 days (first culture, white bars) and re-stimulated with TGFβ1, IL-6, and IL-23 combinations for 24 h (second culture). NS not significant; *P < 0.05, **P < 0.01, and ***P < 0.001 (two-way ANOVA)