Aryl Hydrocarbon Receptor Signals in Epithelial Cells Govern the Recruitment and Location of Helios⁺ Tregs in the Gut

The authors administered indigo naturalis (IN), a nontoxic phytochemical aryl hydrocarbon receptor agonist used for treating patients with ulcerative colitis in Asia, and showed that IN increased Helios+ regulatory T cells (Tregs) and MHC class II+ epithelial cells in the colon.