As such, AHR ligands, including TCDD (Singh et al., 2011) and 3, 3′-diindolylmethane (DIM) (Huang et al., 2013), could restore the Th17/Treg ratio to alleviate experimental colitis by inhibiting Th17 proliferation and inducing Treg differentiation. The gene discussed is AHR; the disease is colitis.