Segmented filamentous bacteria
Segmented filamentous bacteria are members of the gut flora that potently induce immune responses. Although not taxonomically classified, they have been given a candidate name "Candidatus Arthromitus".[1] Referring to these bacteria by their morphology has been somewhat problematic as this terminology does not allow one to distinguish between bacteria that colonize various eukaryotic species or even if segmented filamentous bacteria are actually several groups of bacteria. These bacteria grow primarily in the terminal ileum in close proximity to the intestinal epithelium where they are thought to help induce T helper 17 cell responses.[2] Described over 100 years ago by Joseph Leidy, to date there have been no techniques described to facilitate their growth outside of the mammalian intestinal tract, and recognition of their importance in immunity has seen a slow but steady rise over the past decade.[3] Intriguingly, Segmented Filamentous Bacteria were found to expand in AID-deficient mice, which lack the ability to mount an appropriate humoral immune response because of impaired somatic hypermutation; parabiotic experiments revealed the importance of IgA in eliminating Segmented Filamentous Bacteria.[4] This goes hand and hand with an earlier study demonstrating the ability of monocolonization with Segmented Filametnous Bacteria to dramatically increase mucosal IgA levels[5]. Segmented Filamentous Bacteria are species specific, and may be important to immune development.
References
- ^ Taxonomy of Candidatus Arthromitus.
- ^ Ivanov, I.; Atarashi, K.; Manel, N.; Brodie, E.; Shima, T.; Karaoz, U.; Wei, D.; Goldfarb, K. et al. (2009). "Induction of intestinal Th17 cells by segmented filamentous bacteria". Cell 139 (3): 485–498. doi:10.1016/j.cell.2009.09.033. PMC 2796826. PMID 19836068. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2796826. edit
- ^ Leidy, J. 1849. On the existence of entophyta in healthy animals, as a natural condition. Proc. National Academy of Science. USA 4:225–233
- ^ Suzuki, K.; Meek, B.; Doi, Y.; Muramatsu, M.; Chiba, T.; Honjo, T.; Fagarasan, S. (2004). "Aberrant expansion of segmented filamentous bacteria in IgA-deficient gut". Proceedings of the National Academy of Sciences of the United States of America 101 (7): 1981–1986. Bibcode 2004PNAS..101.1981S. doi:10.1073/pnas.0307317101. PMC 357038. PMID 14766966. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=357038. edit
- ^ Klaasen, HL; Van Der Heijden, PJ; Stok, W; Poelma, FG; Koopman, JP; Van Den Brink, ME; Bakker, MH; Eling, WM et al. (1993). "Apathogenic, intestinal, segmented, filamentous bacteria stimulate the mucosal immune system of mice". Infection and immunity 61 (1): 303–6. PMC 302719. PMID 8418051. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=302719. edit
Further reading
Two review articles
- Ivanov II, Littman DR (May 2010). "Segmented filamentous bacteria take the stage". Mucosal Immunol 3 (3): 209–12. doi:10.1038/mi.2010.3. PMID 20147894.
- Klaasen HL, Koopman JP, Poelma FG, Beynen AC (June 1992). "Intestinal, segmented, filamentous bacteria". FEMS Microbiol. Rev. 8 (3-4): 165–80. PMID 1515159.