Immunology of the Intestine

Abstract

The chapter introduces the anatomy of the intestine and provides an easy-to-understand description of the complex intestinal immune system whose task is to identify food components as friend or foe. The gut’s ability to differentiate needs to be acquired in early childhood by providing a broad range of nutritional and microbial stimuli to the child. If these stimuli are lacking and the child is raised under conditions of low food diversity and extreme hygiene, there is a high risk that any future encounter with novel nutrients and microbes will lead to excessive immune reactions. This can manifest in the form of allergies, chronic inflammatory intestinal diseases or even diseases outside the intestine. Defense against infections vs. tolerance for food and useful intestinal bacteria are regulated by the interaction of a large number of inflammatory and tolerogenic cells of the innate and acquired immune systems. The cells of intestinal immune regulation are in particular macrophages, dendritic cells, T and B cells, but also intestinal epithelial cells. A so-called “leaky good”, i.e., an increased permeability of the intestine, is the result and not the cause of inflammatory processes inside and outside the intestine.