This is because the eye has a special ability to kill off invading bacteria and viruses without resorting to the kind of inflammation seen in other parts of the body.

We believe that it has a great potential to work in other autoimmune diseases by changing the immune response responsible for multiple sclerosis or for the onset of type I diabetes

Dr Andrew Taylor, Schepens Eye Research Institute

It is the inflammation which, as part of an inappropriate immune response, sparks the damage which causes the symptoms of multiple sclerosis.

Scientists believe that it may be possible to harness the eye's ability and head off a number of life-threatening diseases, including type I diabetes.

The research team, from the Schepens Eye Research Institute in Boston, US, extracted the chemical, called factor alpha-MSH, from the eye.

Eye disease

The eye needs this chemical to protect itself from inflammation, as even the slightest flare-up can damage its sensitive light gathering tissues.

The team found that alpha-MSH could actually subtlely alter immune system cells responsible for inflammation so that they did not cause this effect.

To test the potential for the chemical, the researchers tried it against cells taken from mice with a disease called uveitis, in which the immune system wrongly attacks the retina of the eye.

When immune cells from mice without uveitis were mixed with the chemical in the laboratory, the same subtle change was seen.

Then, when these cells were injected into mice with uveitis, the severity of the disease was significantly reduced - and the onset of the disease was prevented.

Dr Andrew Taylor, who led the study, said: "This technique was extremely effective in the mouse model, and we believe that it has a great potential to work in other autoimmune diseases by changing the immune response responsible for multiple sclerosis or for the onset of type I diabetes."

The research is published in the Journal of Leukocyte Biology.