AHR and colitis: The susceptibility to colitis of germ-free mice colonized with fecal microbiota from colitis mice was rescued by the supplementation of Lactobacillus strains (L. murinus CNCM I-5020, L. reuteri CNCM I-5022, and L. taiwanensis CNCM I-5019), which have the capacity to activate AhR by metabolizing tryptophan and producing AhR ligands [357].