These ligands activate AhR signaling to reduce aberrant Th2 responses and may offer an effective strategy for alleviating atopic dermatitis (AD).96,97 Beyond serving as AhR activators, tryptophan metabolites also directly influence T cell metabolism; for instance, microbial-derived tryptamine promotes mTOR activation and glycolysis in CD4+ T cells, leading to an enhanced inflammatory phenotype.98 Here, AHR is linked to Alzheimer disease.