Article: Study reveals a microbe's molecular role in Crohn's disease

Study reveals a microbe's molecular role in Crohn's disease

Changes in the gut microbiome have long been linked with Crohn's disease and other forms of inflammatory bowel disease (IBD), but the biology behind those links has remained murky. Researchers at the Broad Institute, Massachusetts General Hospital (MGH), and Harvard Medical School (HMS) have now found that one bacterium, Ruminococcus gnavus, which is associated with Crohn's disease, releases a certain type of polysaccharide (or a chain of sugar molecules) that triggers an immune response.

...during some flares of Crohn's disease, the abundance of R. gnavus can jump from less than one percent of the gut microbiota to greater than 50 percent." That experiment was a correlation experiment. A is correlated with B. Now the challenge was to get to causation," said Xavier

After growing colonies of R. gnavus in the laboratory, they characterized all of the molecules produced by the bacteria, to see if there was anything pro-inflammatory. One polysaccharide comprised mainly of rhamnose, a sugar not familiar to the human immune system, antagonized the immune system by activating the cytokine TNF-α.

https://medicalxpress.com/news/2019-06-reveals-microbe-molecular-role-crohn.html

Certainly interesting stuff. Triggering TNF-A is calling for an immune attack as a direct-result of this bacterium. I'm on remicade a TNF-A blocker. They're looking to find high abundances of this bacterium prior to a flare occurring, which would be the next link!

Interesting. It seems reasonable that the pro-inflammatory by-product can produce increased inflammation. Finding an increase in the gut microbe before an increase in inflammation is the evidence needed, but should not be too hard to get. Follow some CD patients, taking samples to profile gut microbes every week, and then when some have flares, look to see if the profile changed before the flare.

If temporal precedence can be established, it will be key to find out what causes the bloom of the microbe. It could be a response to the immune suppressing some other gut microbe, or to changes in mucus on the mucosal lining.