Fig. 1

Structure of intestinal epithelium. The intestinal epithelial layer (IEL) ① is the first lining of gastrointestinal tract. It is formed by a single layer of specialized intestinal epithelial cells (enterocytes, goblet cells, paneth cells, microfold cells, stem cells and enteroendocrine cells) that physically separates the gut lumen ② from the circulatory system. The IEL is lined by a mucous layer ③, where the gut microbiota ④ is embedded. The IEL orchestrates gut homeostasis by establishing communication between the gut microbiota and the underlying immune cells in lamina propria ⑤. The intestinal epithelial cells secrete several antimicrobial peptides ⑥ for host-defense. For references, see text. Figure created using BioRender.com