"In addition to their function as a physical barrier, intestinal epithelial cells (IECs) sense the microbiota through pattern recognition receptors. Stimulation of these receptors promotes epithelial cell repair and the upregulation of tight-junction proteins, and triggers the production of various cytokines that signal to cells in the lamina propria. Critically, the epithelium does not stand alone, but rather as a triad with immune cells and the mesenchyme ".