Limiting the Progression of Inflammatory Bowel Disease

IBD is the collective term for Crohn’s disease and ulcerative colitis, two currently incurable conditions which involve excessive inflammation in the gut, causing debilitating symptoms like pain and diarrhea.

Researchers have characterized a specialized type of immune cell, which plays a key role in protecting and repairing the cells in the healthy human gut. These protective immune cells are depleted in inflammatory bowel disease (IBD), leaving patients vulnerable to disease progression and severe complications. 

As part of their study the researchers investigated tissue from over 150 patients at Guy’s and St Thomas’ NHS Foundation Trust, dissecting a major population of T cells called gamma delta (γδ) T cells in the colons of people with healthy guts and people with IBD. In healthy guts, there was a unique specialized subset of gamma delta cells, termed V-gamma-4 (Vg4) cells, that intriguingly were significantly altered and often conspicuously depleted in inflamed IBD samples.

Prior to this work, the team at the Crick and King’s had identified molecules in the healthy gut epithelium (the cells lining the gut walls) which directly interact with Vg4 T cells. So, in this new study they tested whether losing this normal interaction between Vg4 T cells and the epithelium was underpinning disease.

To do this, the team looked at relatively rare individuals carrying a gene that severely limits this interaction, and found that whereas carrying this gene didn’t increase the chance of developing IBD, for those who already developed Crohn’s Disease, it significantly increased the risk of disease progression and the development of severe complications.

The researchers also observed that, in people whose inflammation had improved, those with restored Vg4 T cell function were less likely to relapse than those who did not. This suggests that assessing the status of Vg4 T cells could be a useful biomarker for disease progression.

Adrian Hayday, leader of the study, said: “The links between uncontrolled IBD and particularly severe forms of colon cancer aren’t well understood. So, it’s fascinating that the key immune cell subset that we have identified as missing in IBD, may also be the same as the gut γδ T cells described by another group in Milan as having profound potential to attack colon cancer cells. We think that defects in these cells could conceivably link the two diseases.

The next steps for the research are to investigate potential drug targets for the interactions between γδ T cell and the epithelial cells and to refine approaches for routinely monitoring gut γδ T cells as a much-needed marker for IBD progression versus recovery. The broader implications of this immune cell biology on different body surfaces should also be a focus.

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Sources:

Robin J. Dart, Iva Zlatareva, Pierre Vantourout, Efstathios Theodoridis, Ariella Amar, Shichina Kannambath, Philip East, Timothy Recaldin, John C. Mansfield, Christopher A. Lamb, Miles Parkes, Peter M. Irving, Natalie J. Prescott, Adrian C. Hayday. Conserved γδ T cell selection by BTNL proteins limits progression of human inflammatory bowel disease. Science, 2023; 381 (6663) DOI: 10.1126/science.adh0301

The Francis Crick Institute. “Specialized gut immune cells pinpointed that can limit progression of inflammatory bowel disease.” ScienceDaily. ScienceDaily, 14 September 2023. <www.sciencedaily.com/releases/2023/09/230914175041.htm>.

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