Rheumatic diseases: The microbiota-immunity axis in development and treatment

Rheumatic diseases (RDs) are immune-mediated disorders characterized by complex pathogenic mechanisms usually acting on a genetic background with a large impact on individual and societies and considerable economic costs in all countries. In the last few years, the human microbiota and its interplay with immune system have been extensively studied as a potential and key player in the RD onset and development. As known, the gut microbiota (GM) is crucial for the development of the immune system, contributing to the establishment of the gut-associated lymphoid tissue and modulating both the innate and the adaptive immune responses outside the intestine. Alterations of the microbiota composition, named dysbiosis, can affect the host immune responses at epithelial surfaces, thus determining systemic inflammation in susceptible individuals. In this chapter, we will comment on the intricate relationship between microbiota and immune system, and we will provide the most important evidences for the microbiota-immunity axis’ role in the development of autoimmune RDs, looking also at the potential implication in clinical management and treatment.