AHR and bacterial infectious disease: 2020). The rapid regeneration of IECs is driven by the proliferation of intestinal stem cells in the crypt (Barker et al. 2007), but mice with AHR-specific deficiency in IECs cannot maintain the integrity of the epithelial barrier against bacterial infection due to impaired intestinal stem cells differentiation and proliferation (Metidji et al. 2019). Mucin secreted by the goblet cells is the necessary source of mucus. The deficiency of the AHR gene leads to the loss of goblet cells and reduced expression of mucin 2 in mice (Yin et al. 2019).