| Microbiota residing in the intestine is shown to influence the host physiology. Accordingly, intestinal microbiota is involved in the pathogenesis of a variety of disorders, particularly inflammatory bowel diseases (IBD). Dysregulated interaction of intestinal microbiota and intestinal immunity causes development of IBD. Therefore, in a healthy condition, activity of intestinal immunity is finely regulated to prevent inflammatory responses to the intestinal microbiota. As one of such mechanisms, intestinal epithelial cells possess a barrier function that separates intestinal microbiota and intestinal immunity. Thus, microbiota is present in the intestinal lumen without directly associating with the host cells. But, microbiota is well known to have a beneficial effect on the host cells. In this regard, bacterial metabolites mediate the host cell functions. We will discuss how intestinal homeostasis is maintained. Microbiota is implicated in the pathogenesis of several immune disorders, such as rheumatoid arthritis (RA). We previously showed that some RA patients harbor dysbiotic microbiota, in which Prevotella copri is dominated. We will also discuss how Prevotella mediates the development of arthritis. |
