Celiac disease may be partly triggered by bacterial infection

For people with celiac disease, going gluten-free isn’t just a trendy diet fad – it’s a necessary way of life. This autoimmune disorder is thought to result largely from genetic predisposition, but environmental factors also play a part. Now, researchers have found evidence that exposure to certain bacteria may be one of these external factors.

Gluten is a protein found in grains like wheat, rye and barley, and as such it winds up in foods like bread, pastries and pasta. For the majority of the population it presents no problem, but in people with celiac disease, gluten triggers an autoimmune response. This causes inflammation in the gut and gastrointestinal discomfort, and the easiest solution is to avoid foods containing the protein.

Generally, there are two main genes associated with celiac disease, but only a few people with one or both of those genes goes on to develop the disease. It seems that other environmental factors are needed to tip predisposed people over the edge. Past studies have suggested reovirus infection in the intestine, at a specific stage of development, could trigger the immune system’s overreaction to gluten.

And now a new study has found evidence of another related environmental factor. The researchers found that a particular type of bacteria could be priming the immune system in a similar way. Protein fragments from these bacteria are very similar to fragments from gluten. That means once the immune system finishes fighting off these bugs, it’s still all riled up when gluten proteins start showing up.

To test the idea, the researchers isolated receptors from immune T cells taken from celiac patients. When they were exposed to the bacterial protein fragments, these T cells recognized them, lending weight to the hypothesis.

“In coeliac disease you get aberrant reactivity to gluten and we have provided a proof-of-principle that there’s a link between gluten proteins and proteins that are found in some bacteria,” says Hugh Reid, co-lead author of the study. “That is, it's possible that the immune system reacts to the bacterial proteins in a normal immune response and in so doing develops a reaction to gluten proteins because, to the immune system, they look indistinguishable – like a mimic.”

While there’s still plenty of work to do to confirm the concept, the researchers say that it could eventually lead to new ways to diagnose or treat celiac disease.

The research was published in the journal Nature Structural and Molecular Biology.

Source: Monash University