Immunoregulation at mucosal surfaces

Abstract

Mucous membranes are the largest contact site between the external environment and the internal milieu. They protect the body, allow the exchange of nutrients or respiratory gases and are the barrier that ensures the integrity of the internal environment. These barriers are also subject to aggression from infectious agents, toxins, and physical trauma. They are also sites colonized by an abundant microbiota. Mucous membranes are defensive barriers in which three layers can be defined. The epithelium ensures selective integrity and impermeability by the presence of adhesive junctions between their cells. On the outside of this layer there is a layer of mucus and other secretions that serves as a barrier to a commensal symbiont microbiota, which provides micronutrients vitamins and regulatory molecules. The microbiota lives in symbiosis with the organism but occasionally this microenvironment can be colonized by pathogenic species. To deal with these aggressions, a third layer of this defense barrier is the immunological barrier associated with the mucous membranes. Mucous membranes house the largest population of immune cells in the entire body. The immune system associated with the mucous membranes recognizes pathogens and toxins from outside the barrier but must react to pathogens and tolerate the commensal microbiota. Their different components also receive signals from the other components of the mucosal barrier. All the components of the barrier weave a network of mutual interactions that ensure homeostasis, not only of the mucous membranes but also of the whole organism. Imbalances in the response of the different components of these circuits are the basis of a large number of diseases, not only of the systems in which they are located, but also on the whole-body systems. This Research Topic addresses different aspects of their components and their mutual interrelationships.