title: The love-hate relationship between bacterial polysaccharides and the host immune system.
abstract: This article explores the fascinating relationship between the mammalian immune system and the bacteria that are present in the mammalian gut. Every human is an ecosystem that hosts 10(13)-10(14) bacteria. We review the evidence that immunomodulatory molecules produced by commensal bacteria in the gut have a beneficial influence on the development of certain immune responses, through eliciting the clonal expansion of CD4(+) T-cell populations. This process seems to contribute to the overall health of the host by offering protection against various diseases and might provide supporting evidence at a molecular level for the 'hygiene hypothesis' of allergic immune disorders.
authors.affiliation: Division of Biology, California Institute of Technology, Mail code 156-29, 1200 East California Boulevard, Pasadena, California 91125, USA.
authors.forename: Sarkis K
authors.initials: SK
authors.lastname: Mazmanian
authors.forename: Dennis L
authors.initials: DL
authors.lastname: Kasper
mesh_terms: D000818:Animals; D000941:Antigens / Q000276:immunology; D006262:Health; D006801:Humans; D007107:Immune System / Q000276:immunology*; D008213:Lymphocyte Activation / Q000276:immunology; D011135:Polysaccharides, Bacterial / Q000737:chemistry / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology
chemical_list: D000941:Antigens; D011135:Polysaccharides, Bacterial