title: Regulation of intestinal homeostasis by innate and adaptive immunity.
abstract: The intestine is a unique tissue where an elaborate balance is maintained between tolerance and immune responses against a variety of environmental factors such as food and the microflora. In a healthy individual, the microflora stimulates innate and adaptive immune systems to maintain gut homeostasis. However, the interaction of environmental factors with particular genetic backgrounds can lead to dramatic changes in the composition of the microflora (i.e. dysbiosis). Many of the specific commensal-bacterial products and the signaling pathways they trigger have been characterized. The role of T(h)1, T(h)2 and T(h)17 cells in inflammatory bowel disease has been widely investigated, as has the contribution of epithelial cells and subsets of dendritic cells and macrophages. To date, multiple regulatory cells in adaptive immunity, such as regulatory T cells and regulatory B cells, have been shown to maintain gut homeostasis by preventing inappropriate innate and adaptive immune responses to commensal bacteria. Additionally, regulatory myeloid  cells have recently been identified that prevent intestinal inflammation by inhibiting T-cell proliferation. An increasing body of evidence has shown that multiple regulatory mechanisms contribute to the maintenance of gut homeostasis.
authors.affiliation: Laboratory of Immune Regulation, Department of Microbiology and Immunology, Graduate School of Medicine, Osaka University, Suita, Osaka 565-0871, Japan.
authors.forename: Hisako
authors.initials: H
authors.lastname: Kayama
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Takeda
mesh_terms: D056704:Adaptive Immunity / Q000276:immunology*; D000818:Animals; D001419:Bacteria / Q000276:immunology; D006706:Homeostasis / Q000276:immunology*; D006801:Humans; D007108:Immune Tolerance / Q000276:immunology; D007113:Immunity, Innate / Q000276:immunology*; D007413:Intestinal Mucosa / Q000276:immunology / Q000382:microbiology; D007422:Intestines / Q000276:immunology* / Q000382:microbiology; D018448:Models, Immunological