Figure 3: Summary of changes taking place in the intestine during the fetal period, neonatal period, and adult period. Please refer to the text for details. IECs: intestinal epithelial cells: CRAMP: cathelin-related antimicrobial peptide; CRS: cryptdin-related sequence; IgA: immunoglobulin A; TLR: toll-like receptor; IRAK1: interleukin-1 receptor-associated kinase 1; miR-146a: microRNA 146a.