Intestinal worms infect over 2 billion people across the world, mostly children, in areas with poor sanitation. But despite causing serious health problems, worms can actually help the immune system of its host as an indirect way of protecting themselves.
The evidence for this is so strong that we are now testing worms for clinical benefits. However, very little is known about how worms interact with the host's immune system. A new study by shows that these effects go through the gut's bacteria that help digestion. The work is published in Immunity.
The researchers looked at the effects of helminths that infect pigs. After chronic infection with the helminths, they discovered that the animals' metabolism had been changed drastically; specifically, they produced increased levels of a class of fats in the gut called "short-chain fatty acids".
These fatty acids are produced by the microbiome, and can activate a family of receptors that in turn influence the immune system. The receptors are also known to contribute to certain functions - and malfunctions - of the colon, and are even involved in modulating allergic airway disease.
This is exactly what the researchers found when they also monitored cells in the immune system of mice that had been infected with a helminth. Like the pigs, the mice showed an increased production of short-chain fatty acids.
Further testing showed that these acted on the same receptors to influence specific immune cells. In short, the researchers uncovered a clear link between worm infection, microbiome, and the immune system.