The role of the gut in type 2 immunity

Abstract

Allergic and autoimmune disorders have been on the raise in the last decades in westernized countries while infectious diseases could be dramatically reduced due to efficient vaccination campaigns, improvement of personal hygiene and use of medication. Alteration of immunological tolerance may be implicated in both autoimmune and allergic inflammation yet underlying mechanisms remain poorly understood. Microbes colonizing all barrier sites are now known to have strong impact on our general immune status. The intestinal tract harbors the densest community of microbes and in combination with a huge surface area, the microenvironment in the gut implies strong tolerogenic properties. While a healthy symbiosis between intestinal microbes and the immune system is beneficial for the host, dysbiosis of microbial communities can heavily impact on immune responses and immunological tolerance. A systemic effect on the general susceptibility to allergic and autoimmune disorders is difficult to study and remains controversial. As an alternative explanation, allergic sensibilisation via the skin or lung is thought to be an important pathway but lacks the capability to explain the increase of allergic disorders on an epidemiological level. In this chapter, I will highlight a possible impact of a beneficial host-microbiota relationship in both the intestinal tract and other mucosal surfaces.