[Human microbiota association with immunoglobulin A and its participation in immune response]

Human microbiota is the aggregate of microorganisms that reside in our body. Its phylogenetic composition is related to the risk for suffering from inflammatory diseases and allergic conditions. Humans interact with a large number and variety of these microorganisms via the skin and mucous membranes. An immune protection mechanism is the production of secretory IgA (SIgA), which recognizes resident pathogenic microorganisms and prevents their interaction with host epithelial cells by means of immune exclusion. Formerly, it was thought that SIgA only function in mucous membranes was to recognize and exclude pathogens, but thanks to the use of massive sequencing techniques for human microbiota phylogenetic characterization, now we know that it can be associated with pathogenic and non-pathogenic microorganisms, an association that is important for functions the microbiota carries out in epithelia, such as regulating the capability of certain microbial species to settle on the skin and mucous membranes, and stimulation and regulation of the immune response and of the risk for the development of inflammatory problems, allergic conditions, autoimmune diseases, and even cancer. Established microbiota determines the type of bacterial species (and probably viral and protozoan species) that reside on the skin and mucous membranes, promoting microbial diversity.