Immune Imprinting by Gut Microbiota Early in Life, a Window of Opportunity

During and immediately after birth, mammals are exposed to bacteria of maternal and environmental origins, some of which colonize the intestinal lumen to form the early-phase intestinal microbiota. The immature intestinal microbiota during infancy is unstable and susceptible to various environmental factors. Many epidemiological studies have shown that delivery by cesarean section and antibiotic exposure affect the gut microbiota early in life, possibly predisposing the host animals to immune allergic diseases in adulthood. However, the mechanism linking the early microbiota and disease susceptibility remains unclear. A growing body of evidence indicates that intestinal microbiota-dependent immune imprinting occurs only during a specific period in infancy, and that lack of immune imprinting during this “window of opportunity" may lead to immune allergic diseases after weaning. Therefore, expectations are high that research into a methodology for the normalization of the intestinal microbiota during infancy will lead to the prevention of the onset of future immune allergic diseases.