Nevco News
November 2009
Volume 2, Issue 11
New Information On Friendly Bacteria
| Out of the trillions of "friendly" bacteria -- representing
hundreds of species -- that make our intestines their home, new
evidence in mice suggests that it may be a very select few that
shape our immune responses. The findings detailed in two reports
appearing in the journals Cell and Immunity, both Cell Press
publications, offer new insight into the constant dialogue that
goes on between intestinal microbes and the immune system, and
point to a remarkably big role for a class of microbes known as
segmented filamentous bacteria (SFB). "Our study provides the surprising result that among the hundreds of bacterial species composing the gut microbiota -- only a very small number, the prototype of which is SFB -- can efficiently stimulate maturation of the immune barrier," said Valérie Gaboriau-Routhiau of INSERM in France, who led the Immunity report. "A unique feature of SFB appears to be its capacity to simultaneously stimulate a large spectrum of intestinal immune responses -- which complete and balance each other." |
Notably, those SFBs stimulate particular types of helper T
cells, known as Th17 cells, the studies show. In Littman's case, the findings by his group were something of an accidental discovery. They were studying T cells in the intestine and were getting some inconsistencies in their results. Introduction of SFB, but not other bacteria, stimulated the production of Th17 cells in mice who were otherwise deficient in them. The SFB-induced immune response protected the mice from becoming ill with an intestinal pathogen. Gaboriau-Routhiau suspects that SFBs may have some special attributes that explain their importance. "One striking feature of SFB, which makes it very different from the vast majority of the members of the microbiota, is its capacity to adhere to epithelial cells notably in the ileum, a property normally more the prerogative of pathogens." The ileum is the final section of the small intestine and is distinguished by many folds, giving it a very substantial surface area. |
The findings also suggest how such commensal bacteria might sometimes go from helping to fend off nasty bugs, to ones that may tip the balance of the immune system toward the development of autoimmune disease, such as Crohn's disease. Indeed, the Th17 cells have been noted in recent years because of their importance in autoimmune diseases. Animals with defects in those Th17 cells generally don't develop autoimmune disease or develop disease that is less severe. Given the bacterial diversity found within our guts, the new results show how much there still is to learn about this important aspect of the immune system. While probiotic products on the market today don't have the benefit of such a thorough understanding, there is little doubt that down the road we may be able to manipulate our immune system in beneficial ways with microbes. Cell Press (2009, October 19). In Shaping Our Immune Systems, Some 'Friendly' Bacteria May Play Inordinate Role ScienceDaily. |
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