If your children stump you with 'cite your data' claims on why they need to eat leafy green vegetables, even though we got to the top of the food chain so we wouldn't have to do that, here is good news; a new study found that that an immune cell population essential for intestinal health could be controlled by leafy greens in your diet.

The immune cells, named innate lymphoid cells (ILCs), are found in the lining of the digestive system and produce a hormone called interleukin-22 (IL-22), which can protect the body from invading bacteria and play an important role in controlling food allergies, inflammatory diseases and obesity, and may even prevent the development of bowel cancers.

The researchers discovered the gene T-bet is essential for producing a population of these critical immune cells and that the gene responds to signals in the food we eat. T-bet was found to be essential for generating a subset of ILCs which is a newly discovered cell type that protects the body against infections entering through the digestive system.

"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 to bacteria in the gut," said Dr. Gabrielle Belz from the Walter and Eliza Hall Institute's Molecular Immunology division have . "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."

The proteins in green leafy (cruciferous) 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. "Proteins in these leafy greens could be part of the same signalling pathway that is used by T-bet to produce ILCs," 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."

ILCs are essential for maintaining the delicate balance between tolerance, immunity and inflammation. Co-author Lucie Rankin said the discovery had given the research team further insight into external factors responsible for ILC activation. "Until recently, it has been difficult to isolate or produce ILCs. So we are very excited about the prospect for future research on these cells which are still poorly understood."

Belz said. "Our research shows that, without the gene T-bet, the body is more susceptible to bacterial infections that enter through the digestive system. This suggests that boosting ILCs in the gut may aid in the treatment of these bacterial infections," she said. "The discovery of these immune cells has thrown open a completely new way of looking at gut biology. 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.

"Understanding the biology of ILCs and the genes that are essential for generating them will help us to develop methods of targeting these cells. 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."

Published in Nature Immunology.