A microbial symbiosis factor prevents intestinal inflammatory disease.
Humans are colonized by multitudes of commensal organisms representing members of five of the six kingdoms of life; however, our gastrointestinal tract provides residence to both beneficial and potentially pathogenic microorganisms. Imbalances in the composition of the bacterial microbiota, known as dysbiosis, are postulated to be a major factor in human disorders such as inflammatory bowel disease. We report here that the prominent human symbiont Bacteroides fragilis protects animals from experimental colitis induced by Helicobacter hepaticus, a commensal bacterium with pathogenic potential. This beneficial activity requires a single microbial molecule (polysaccharide A, PSA). In animals harbouring B. fragilis not expressing PSA, H. hepaticus colonization leads to disease and pro-inflammatory cytokine production in colonic tissues. Purified PSA administered to animals is required to suppress pro-inflammatory interleukin-17 production by intestinal immune cells and also inhibits in vitro reactions in cell cultures. Furthermore, PSA protects from inflammatory disease through a functional requirement for interleukin-10-producing CD4+ T cells. These results show that molecules of the bacterial microbiota can mediate the critical balance between health and disease. Harnessing the immunomodulatory capacity of symbiosis factors such as PSA might potentially provide therapeutics for human inflammatory disorders on the basis of entirely novel biological principles.
Division of Biology, California Institute of Technology, Pasadena, California 91125, USA. sarkis@caltech.edu
Sarkis K
SK
Mazmanian
June L
JL
Round
Dennis L
DL
Kasper
D000818:Animals; D001441:Bacteroides fragilis / Q000235:genetics / Q000276:immunology / Q000502:physiology*; D015496:CD4-Positive T-Lymphocytes / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D003092:Colitis / Q000139:chemically induced / Q000276:immunology / Q000382:microbiology* / Q000517:prevention & control*; D004195:Disease Models, Animal; D005856:Germ-Free Life; D044923:Helicobacter hepaticus / Q000472:pathogenicity*; D007249:Inflammation / Q000139:chemically induced / Q000382:microbiology / Q000473:pathology / Q000517:prevention & control; D015212:Inflammatory Bowel Diseases / Q000276:immunology / Q000382:microbiology / Q000473:pathology / Q000517:prevention & control; D016753:Interleukin-10 / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D020381:Interleukin-17 / Q000378:metabolism; D007422:Intestines / Q000187:drug effects / Q000276:immunology / Q000382:microbiology / Q000473:pathology; D051379:Mice; D011135:Polysaccharides, Bacterial / Q000235:genetics / Q000276:immunology / Q000378:metabolism / Q000494:pharmacology; D013559:Symbiosis / Q000502:physiology*; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis / Q000378:metabolism
D020381:Interleukin-17; D011135:Polysaccharides, Bacterial; D014409:Tumor Necrosis Factor-alpha; D016753:Interleukin-10