It could be deemed appropriate to view terrestrial vertebrates as a combination of many species and their genetic build as a composite of genes embedded in their own genome and in the genomes of affiliated microbial partners: the microbiome. The body’s large surfaces, harbouring many resident commensals, are, however, also exposed to potentially harmful micro-organisms. These surfaces include the skin and the gastro-intestinal tract.
Several barriers are in place to prevent microbes invading our bodies, the first of which is the epithelial cell layer. Although sufficient to prevent invasion by most microbes, this is not always adequate. A second line of defence is formed by cells of the immune system, providing protection against those microbes that overcome the epithelial barrier or which invade the body after trauma.
Our laboratory studies the role that cells of the immune system play at the initiation, modulation and resolution of immune responses at epithelial barrier sites. These studies provide insights into the mechanisms that control the maintenance of a resident population of micro-organisms, promoting healthy living, and the prevention of undesirable immune responses that may result in chronic infections, allergies, autoimmunity and an increased risk of cancer.
Interestingly, many commensal micro-organisms are highly beneficial to us and are instrumental in mediating physiologically important chemical transformations, whilst the cells of the epithelial barrier themselves are important for nutrient processing and uptake. Hence, an immune reaction at these sites needs to be tightly controlled and tailored to the potential threat-level of the micro-organisms detected (commensals vs. harmful opportunistic pathogens), with minimal damage to self, and with swift resolution and wound repair.