AHR and bacterial infectious disease: For instance, SCFAs facilitate the expansion of Th17 cells and ILC3s in the intestine via free fatty acid receptor 2,[13] and Lactobacillus‐derived indole serves as an AHR ligand to enhance IL‐22 transcription in ILC3s.[14] BA metabolism, which involves the intestinal microbiome, also contributes to the functions of peripheral regulatory T cells,[39] ILCs,[40] and intestinal stem cells.[41] In the present study, Lactobacillus contributed to HCA production and enhanced γδT cell and ILC3 development in early life by inhibiting FXR, which effectively prevented intestinal bacterial infections.