Intestinal Bacteria and Dendritic Cells

Abstract

It has been reported that there are more than 1,000 types of intestinal bacteria and more than 40 trillion intestinal bacteria in the human intestine. The human intestinal microbiota weighs 1.5 to 2 kg and is also called the intestinal flora. About half to one third of feces is of bacterial origin and humans shed 2 to 3 trillion bacteria per day. In recent years, next-generation sequencers have made it possible to accelerate gene analysis of the gut microbiota, and metagenomic analysis. As a result, it has become clear that the composition of the intestinal flora of subjects with digestive diseases as well as various diseases such as metabolic diseases, neurological diseases, allergic diseases, and arteriosclerosis is different from that of healthy subjects. Our studies have revealed links between gastrointestinal disorders such as ulcerative colitis, colorectal adenoma, colorectal cancer, liver cirrhosis, and irritable bowel syndrome and the gut microbiota. Metabolites of gut microbiota have also been suggested to be a related mechanism of gut microbiota, but further detailed investigation is awaited. Furthermore, it has been reported that the intestinal flora may be associated with the onset and treatment outcomes of patients with cancer via intestinal epithelial cells and the intestinal immune system. In this paper, we introduce recent findings regarding immune regulation in the intestine, mainly regarding the involvement of antigen-presenting dendritic cells.