Eating leafy greens may be even more important than previously thought, with the discovery that an immune cell population essential for intestinal health could be controlled by the presence of leafy greens in the diet.

Research undertaken by Australian scientists and published in March 2013 in the Nature Immunology journal found that leafy greens help the body produce digestive immune cells that play an important role in protecting the body from infection. The research team included Dr Gabrielle Belz, Lucie Rankin, Dr Joanna Groom and other researchers from the Walter and Eliza Hall Institute’s Molecular Immunology division.

The immune cells, named innate lymphoid cells (ILCs), are found in the lining of the digestive system and protect the body from ‘bad’ bacteria in the intestine. They are also believed to play an important role in controlling food allergies, inflammatory diseases and obesity, and may even prevent the development of bowel cancers.

The researchers found that the gene ‘T-bet’ is essential for producing a population of these critical immune cells and that the gene responds to signals in food. Proteins in green leafy vegetables are known to interact with a cell surface receptor that switches on T-bet, and might play a role in producing these critical immune cells.

“In this study, we discovered that T-bet is the key gene that instructs precursor cells to develop into ILCs, which it does in response to signals in the food we eat and bacteria in the gut,” said Dr Belz, one of the study’s authors. “ILCs are essential for immune surveillance of the digestive system and this is the first time that we have identified a gene responsible for the production of ILCs,” she said.

“Proteins in these leafy greens could be part of the same signaling pathway that is used by T-bet to produce ILCS,” Dr Belz said. “We are very interested in looking at how the products of these vegetables are able to talk to T-bet to make ILCs, which will give us more insight into how the food we eat influences our immune system and gut bacteria,” she added.

ILCS are essential for maintaining the delicate balance between tolerance, immunity and inflammation. The immune cells help to maintain a ‘healthy’ environment in the intestine by promoting good bacteria and healing small wounds and abrasion that are common in the tissues of the gut. They may also have a role in resolving cancerous lesions.

The study’s authors said that it until recently it had been difficult to isolate or produce ILCS.

“The discovery of these immune cells has thrown open a completely new way of looking at gut biology,” Dr Belz said. “We are just starting to understand how important these immune cells are in regulating allergy and inflammation, and the implications for bowel cancer and other gastrointestinal disorders such as Crohn’s disease,” she said.

“Understanding the biology of ILCs and the genes that are essential for generating them will help us to develop methods of targeting these cells,” Dr Belz said. “This might include boosting ILCs in situations where they may not be active enough, such as infections or some cancers, or depleting them in situations where they are overactive, such as chronic inflammatory disease,” she said.

The research was supported by the National Health and Medical Research Council of Australia, the Sylvia and Charles Viertel Foundation, the Howard Hughes Medical Institute and the Victorian Government.

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