Image caption The shiny layer of mucus in the small intestine calms the immune system

Bottled mucus may one day play a role in some gut diseases, according to US researchers.

A study of the slimy lining of the bowels, published in the journal Science, showed mucus had a role in calming the immune system.

The team at Mount Sinai Hospital, in New York, believe it may be useful in diseases in which inflammation runs rampant in the intestines.

The human body naturally produces around a litre of mucus every day.

Researchers at the hospital and Mount Sinai School of Medicine were investigating why the lining of the bowel does not react to the trillions of bacteria which call the human intestines home. Elsewhere in the body, the immune system would launch a brutal attack against such invaders.

The team investigated the interaction between the mucus produced by the intestines and the immune system.

They showed that a mucus was not only acting as barrier between bacteria and immune system, but a component of the mucus was also calming the immune response. Sugars, or glycans, stuck to the a mucus protein called MUC2 were having the effect.

Lead researcher Dr Andrea Cerutti told the BBC: "We were able to show its ability to dampen the immune reaction in a specific type of immune cell, a dendritic cell, which orchestrates the immune response.

"But these are just initial studies; we know very, very little about mucus."

Mucus treatments?

One area the team think mucus could help in is some bowel problems.

Crohn's disease, inflammatory bowel disease and ulcerative colitis are all poorly understood diseases, but do have inflammation, a part of the immune response, as a common feature.

Dr Cerutti said mucus was often disrupted in these patients and suggested that it may be possible to use mucus as a treatment.

One vision is to artificially synthesise mucus, although this is not currently possible, or a drug which can stimulate the same effect in the lining of the gut.

Whether such approaches to boost the mucus layer of the guts would help patients with bowel disorders is still unknown.

Mucus is not unique to the digestive system. It lines the lungs and streams out of the nose during a cold.

There is speculation that it could be producing similar immune-calming effects in the respiratory system and may be playing a role in allergies and asthma.

Dr Cerutti said even cancer may be affected by mucus: "Several aggressive tumours, such as colon, ovarian, and breast cancers produce mucus, including MUC2.

"Mucus produced by malignant cells may prevent protective immune responses against the malignant cells."

Prof Jon Rhodes, from the department of gastroenterology at the University of Liverpool, said: "There's a massive amount of work in this intriguing paper and it's fascinating to read.

"To extrapolate this to just swallowing mucus would be hopelessly naive, but what might actually be interesting to speculate is that when the nature of the glycans are better understood it could lead to a very exciting and new type of therapeutic"