sciencedaily | Infection with worms counters inflammatory bowel diseases (IBD) by triggering immune responses that change the mix of bacteria, or microbiome, in the gut. This is according to a study published online April 14 in the journal Science.
The study results support the hygiene hypothesis which, in the case of IBD, argues that the absence of exposure to worms in too-clean modern living spaces has left some with oversensitive, gut-based immune systems vulnerable to inflammatory diseases. Gut worms have helped to train and balance immune systems throughout human evolution, but are now missing in developed nations, which, in turn, have the highest rates of Crohn's disease and ulcerative colitis.
In the newly published study, a team led by researchers from NYU Langone Medical Center found that mice infected with intestinal worms experienced as much as a thousand-fold decrease in Bacteroides -- a group of bacterial species linked by past studies to higher risk for IBD. At the same time, the number of Clostridia, a bacterial species known to counter inflammation, increased tenfold. The investigators argue that the immune response to the worms triggers the growth in Clostridia, which then either outcompete Bacteroides for nutrients or release toxins harmful to Bacteroides.
"Our findings are among the first to link parasites and bacteria to the origin of IBD, supporting the hygiene hypothesis," says study co-senior investigator and parasitologist P'ng Loke, PhD, an associate professor at NYU Langone. Loke says this model may also be applicable to other autoimmune diseases, including multiple sclerosis, rheumatoid arthritis, and type 1 diabetes, in which processes meant to attack foreign invaders instead become oversensitive and react to the body's own cells.
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