Fig. 1.

Intestinal epithelial cells (IECs) are the first barrier against outer environment. The gastrointestinal tract, formed of an IEC monolayer, interacts with the commensal microbiome and protects the organism from pathogenic microbes by secreting antimicrobial peptides and mucins. Further, IECs coordinate with stromal cells, including immune cells and mesenchymal cells, via antigen presentation and cytokine-mediated signaling, to maintain gastrointestinal homeostasis.