Interaction between gut microbiota and host immune cells

The intestine, skin, and respiratory tract harbor pools of commensal microbes, known as microbiota. Over the last few years, the field of mucosal immunology has revealed that the microbiota play important roles in the host immune system. Here, we have summarized recent studies regarding the interaction between microbiota and the mucosal immune systems in health and diseases. The application of 16S rRNA PCR and new sequencing technology have enabled us to understand the composition of intestinal microbiota. Here, we specifically assess their contribution to obesity and cancer (chronic inflammatory conditions) as well as to inflammatory autoimmune diseases (e.g., inflammatory bowel disease and type 1 diabetes) and allergic syndromes. Optimization of the microbiota composition has been attempted via the intake of probiotic bacteria in various fermented foods and via fecal microbiota transplantation (FMT) from healthy donors to patients with Clostridium difficile-induced colitis. The presence of certain microbiota species affects the development and function of various types of immune cells, such as regulatory T (Treg) cells and interleukin-17-producing helper T (Th17) cells. Furthermore, innate lymphoid cells (ILCs) have also been shown to be regulated by microbiota. These findings indicate that manipulation of the microbiota could improve health and chronic diseases via immune regulation.