The aromatic hydrocarbon receptor (AhR) ligand, the metabolite produced by intestinal Trp-decomposing microorganisms, showed a decreasing trend in the intestines of patients with IBD (Lamas et al., 2016), and recent studies have confirmed that, as a key immunomodulator, AhR ligands potentially induce a variety of cellular and epigenetic mechanisms to attenuate inflammation (Cannon et al., 2021). The gene discussed is AHR; the disease is inflammatory bowel disease.