AHR ligands, including TCDD (Singh et al., 2011; Liu et al., 2020), FICZ (Qiu and Zhou, 2013; Hanieh, 2014; Wang et al., 2018), and Norisoboldine (NOR) (Lv et al., 2018a; Lv et al., 2018b), could ameliorate colitis symptoms by suppressing Th17 differentiation, leading to the increased IL-22 production, as well as decreased expression of IFN-γ and IL-17. The gene discussed is AHR; the disease is colitis.