Key points. 1  Intestinal epithelial cells (IECs) provide a physical and biochemical barrier that segregates host tissue and commensal bacteria to maintain intestinal homeostasis. 2  Secretory IECs support this function through the secretion of mucins and antimicrobial peptides.ey points. 1  Intestinal epithelial cells (IECs) provide a physical and biochemical barrier that segregates host tissue and commensal bacteria to maintain intestinal homeostasis. 2  Secretory IECs support this function through the secretion of mucins and antimicrobial peptides.