A super-charged immune system could reduce the symptoms of a debilitating bowel disease, researchers say.

Crohn's disease is a chronic, lifelong condition, which causes inflammation of the small intestine or colon.

US researchers have found that boosting the immune system improves symptoms of the disease in 80% of patients with moderate to severe Crohn's.

Around one in 1,000 have the condition in the UK. It usually begins between the ages of 20 and 30 and causes diarrhoea, abdominal pain, infections. Some patients can need surgery.

It has been thought that Crohn's results from an overactive immune system, so treatments have tried to suppress, rather than boost it.

Conventional thinking would have predicted that these drugs could worsen the disease

Prof Brian Dieckgraefe

But some patients do not benefit from this treatment.

The researchers, from the Washington University School of Medicine in St Louis, Missouri, discovered patients with some genetic disorders, characterised by impaired immune systems, had similar gastrointestinal problems to people with Crohn's.

They looked at patients with glycogen storage disease 1B, where people have problems metabolising glucose and chronic granulomatous disease.

About a third had symptoms of Crohn's disease.

Patients with the genetic disorders are often treated with drugs that stimulate the body's immune response.

One drug is an artificial version of a protein which the body produces to boost the immune response by increasing the number and function of white blood cells.

It is called granulocyte-macrophage colony stimulating factor (GM-CSF), also known as sagramostim or Leukine.

It has been found to treat the symptoms of the immune disorders, but it also reduced the symptoms of Crohn's disease.

'Oil on a fire'

Unlike other treatments for Crohn's, which target acquired immunity that develops over time, it targets the body's built-in immune system - the first line of defence against infection.

Researchers gave the drug to 15 patients with Crohn's disease.

They were given daily injections of GM-CSF every day for eight weeks.

Eighty per cent who were given the treatment significantly improved.

Half were considered to be in clinical remission following treatment.

Patients were followed after the end of the study and it was found symptoms returned once the treatment stopped.

Professor Joshua Korzenik, who led the research, said: "At first blush, the idea of priming the immune system in patients with Crohn's disease sounds sort of like throwing oil on a fire.

Natural

"You might compare it to proposing a high cholesterol diet to treat heart disease."

But he added: "This approach may someday help large numbers of patients who don't respond to traditional Crohn's disease therapy."

He said larger studies were now needed to confirm their findings.

Fellow researcher Professor Brian Dieckgraefe added: "Conventional thinking would have predicted that these drugs could worsen the disease.

"But we thought that these immune deficiencies provided a good model for how our Crohn's patients would respond.

"Furthermore, we knew that GM-CSF was a natural protein that already was present in the body."

The research is published in The Lancet.