Gut and Breast Milk Microbiota and Their Role in the Development of the Immune Function

The gastrointestinal immune system consists of both innate and adaptive immunity. The microbiota plays an important role in gastrointestinal immune function. In newborns, the maternal gut microbiota may either come across into the amniotic fluid or secrete factors that enter the amniotic fluid and affect the development of oral tol- erance in utero. Adequate colonization must occur in the immediate postpartum period for the appropriate mucosal immune response since it is apparent that later attempts at colonization do not have the same impact. Human milk, being also a direct source of microbes, represents one of the main factors that play a critical role in influencing infant’s microbiota composition.