AHR and immune system disorder: In this review, we propose a classification system for intestinal inflammation based on the "microbiota metabolite immune disease" axis, which decomposes the general concept of "intestinal inflammation" into five operable molecular subtypes: trimethylamine N-oxide-driven, lipopolysaccharide imbalance, short-chain fatty acid imbalance, aryl hydrocarbon receptor ligand-regulated, and bile acid metabolic disorder types.