Clinical studies have confirmed that AHR-agonistic indole levels in the feces of patients with IBD are significantly positively correlated with serum IL-22 concentrations(p < 0.01), and that their deficiency is directly associated with increased intestinal permeability(elevated plasma lactoferrin levels) and worsening disease activity index(CDAI) (Wang et al., 2023). This evidence concerns the gene AHR and inflammatory bowel disease.