Intestinal immune health.

The fetal intestinal immune system is structurally intact from a very early gestational age. At birth, the neonate is challenged with an extraordinary and variable bacterial challenge. This mucosal and bacterial interface is the site of critical symbiotic and potentially pathogenic interactions. Neonatal inflammatory reactions are often exaggerated, creating a situation in a newly colonized gut whereby homeostasis must be actively achieved. Fortunately, the neonate is armed with a multitude of protective mechanisms by which to ensure a productive microbiota in the setting of an intact mucosal surface. The intestinal epithelium orchestrates complex interactions and signaling through a variety of intrinsic and extrinsic stimuli. Chief among these is the immunomodulatory capacity of breast milk which is increasingly implicated in the achievement of intestinal and immunologic health via a multitude of mechanisms. Additionally, developmental expression of enzymes, pattern recognition, downstream signaling and dendritic cell interaction all contribute to intestinal homeostasis. Current research is uncovering the molecular mechanisms behind many of these mechanisms. These strategies lend insight into the establishment of tolerance so critical to neonatal health. In a clinic context of increasing food allergy and inflammatory bowel disease, elucidating this machinery is increasingly pertinent. Future research should explore these molecular interactions more closely for their potential therapeutic applications.