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A group of specialised immune cells in the gut may play a key role in controlling the progression of Crohn’s disease.

Crohn’s disease is one of two main forms of inflammatory bowel disease (IBD) that together affect roughly 1 per cent of adults in the UK and the US. However, very little is known about what actually causes them, says at the Francis Crick Institute in London.

Immune cells in the gut are thought to play a role, particularly a set of cells called gamma delta T-cells, he says.

Hayday and his colleagues wanted to better understand what these cells look like in the guts of people with IBD compared with those with healthy guts. To do this, they took gut lining samples from 150 people who were undergoing a colonoscopy, some of whom had IBD.

They found that people with IBD generally had lower numbers of a specialised subset of these immune cells, called V-gamma-4 (Vg4) cells, than those with a healthy gut. These cells are largely found in the gut lining, says Hayday.

But it wasn’t simply the case that those who had fewer Vg4 cells were more likely to have IBD. Instead, specifically for people with Crohn’s disease, the team found that people with fewer of these immune cells in the gut were likely to have more severe disease.

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Among people who were in remission from Crohn’s disease, people with Vg4 cells that looked like those in people with healthy guts were less likely to relapse in the next five years.

“These cells are not going to stop you getting the disease, but they’re going to give you a better response to it,” says Hayday. “It’s sort of like a vacuum cleaner: if you’ve got a good vacuum cleaner, you can keep on top of things.”

He says it is unclear why these cells seem to be depleted in people with IBD, but they could potentially act as a biomarker to help doctors diagnose what type of IBD a person has more specifically.

“In the clinic, when I have a patient who comes to me, we don’t really have clear biomarkers that tell us which drug might treat them best,” says at King’s College London, a member of the study team. These cells could help doctors determine if patients have a type of IBD that is likely to relapse or not, he says.