Developmental signifi cance of early gut-associated lymphoid tissue (GALT)- microbiota interactions in health and disease: Creating balance between tolerance and infl ammation in children

The establishment of gut microbiota in humans does not occur randomly but develops after birth through highly organized interactions between microorganisms, the immune processes orchestrated by the Gut-Associated Lymphoid Tissue (GALT), and a selective absorption to the blood regulated by the Gastrointestinal-Blood Barrier (GIB). In term infants, the initial colonization of gut microorganisms depends on the maturation of the GALT and critical closure of GIB and these interactions lead to the establishment of symbiotic conditions defi ned as a balance between immunity and infections. In preterm infants, development of the GALT is less complete at birth, and the GIB closure is delayed, both of which impact gut microbiota colonization resulting in dysbiosis. Early developmental dysbiosis may underlie non-infectious diseases such as allergies, autoimmune diseases, or infl ammatory bowel diseases and contribute to the pathology of neurodevelopmental disorders. This review focuses on the developmental signifi cance of GALT - microbiota interaction while comparing preterm and term infants. It concludes with the premiss that the developmental dysbiosis may have both short- and long-term impact on human health.