T-cell selection and intestinal homeostasis.
Although intestinal bacteria live deep within the body, they are topographically on the exterior surface and thus outside the host. According to the classic notion that the immune system targets non-self rather than self, these intestinal bacteria should be considered foreign and therefore attacked and eliminated. While this appears to be true for some commensal bacterial species, recent data suggest that the immune system actively becomes tolerant to many bacterial organisms. The induction or activation of regulatory T (Treg) cells that inhibit, rather than promote, inflammatory responses to commensal bacteria appears to be a central component of mucosal tolerance. Loss of this mechanism can lead to inappropriate immune reactivity toward commensal organisms, perhaps contributing to mucosal inflammation characteristic of disorders such as inflammatory bowel disease.
Department of Medicine, Division of Rheumatology, Washington University School of Medicine, St. Louis, MO, USA.
Teresa L
TL
Ai
Benjamin D
BD
Solomon
Chyi-Song
CS
Hsieh
D000818:Animals; D001419:Bacteria / Q000276:immunology; D002454:Cell Differentiation / Q000276:immunology; D060833:Cellular Microenvironment / Q000276:immunology; D060966:Clonal Selection, Antigen-Mediated / Q000276:immunology*; D003713:Dendritic Cells / Q000276:immunology; D018984:Epitopes, T-Lymphocyte / Q000276:immunology; D006706:Homeostasis / Q000276:immunology*; D054884:Host-Pathogen Interactions / Q000276:immunology; D006801:Humans; D007107:Immune System / Q000276:immunology; D015212:Inflammatory Bowel Diseases / Q000276:immunology / Q000378:metabolism / Q000382:microbiology; D007413:Intestinal Mucosa / Q000276:immunology / Q000378:metabolism / Q000382:microbiology; D007422:Intestines / Q000276:immunology* / Q000382:microbiology; D050378:T-Lymphocytes, Regulatory / Q000166:cytology / Q000276:immunology* / Q000378:metabolism / Q000382:microbiology; D014157:Transcription Factors / Q000378:metabolism
D018984:Epitopes, T-Lymphocyte; D014157:Transcription Factors
T cell; T-cell receptors; inflammatory bowel disease; mucosa