'Overdose' may halt MS relapses

MS is a disabling and hard-to-treat condition

The disabling attacks that characterise multiple sclerosis might be stopped by a huge dose of the chemical that triggers them.

The unlikely-sounding technique was compared by one scientist to "pouring gasoline on a fire" to put it out.

MS relapses happen when the body's own immune system, which normally is activated to fight against foreign intruders such as bacteria and viruses, launches an attack against the tissues of the body.

Current treatments have only limited effect

In the case of MS, these are the myelin sheaths which surround the nerve fibres - if they are damaged, the fibres cannot conduct nerve messages as efficiently.

Every time the immune system launches an attack, the patient suffers a relapse, which generally leaves him or her more disabled than before.

Scientists are still not entirely sure how or why the immune system comes to regard the myelin cells as an intruder, but believe that somehow the "killer" T-cells which carry out the attacks become sensitised to a particular protein on the surface of the myelin cell.

This defence system functions if the T-cells are exposed to small amounts of this protein.

However, what Dr Michael Lenardo, from the National Institute of Allergy and Infectious Diseases, discovered was that larger amounts of this protein actually had the reverse effect.

Instead of launching a massive response, the T-cells simply shut down.

This is a natural safeguard devised by the body to stop too many T-cells being around at the same time.

Smothering the fire

Dr Lenardo said: "The immune system doesn't let your T-cells grow uncontrolled and kill you. In this case, adding more antigen smothers the fire."

To test this principle, the research team stimulated MS in nine marmoset monkeys by sensitising their T-cells to myelin proteins.

Three monkeys then got huge additional doses of myelin protein, three got moderate doses, and three received no additional treatment.

The untreated monkeys went on to have symptoms similar to those of humans with MS.

None of the huge-dose group got symptoms, and while two out of three in the moderate did get symptoms, they took longer to develop.

Brain scans

Brain scans showed that while untreated monkeys had experienced massive myelin damage, the huge-dose group had only suffered slight damage, suggesting that the disease had at the very least been significantly slowed.

Although the reports authors, writing in the Journal of Immunology, say that much more work needs to be done, they suggest that the technique could in the future ease the suffering of patients with other "auto-immune" diseases.

Examples of these include type I, or juvenile diabetes, which is caused when insulin-producing pancreatic cells are attacked and destroyed, and myasthenia gravis, in which muscle cells are destroyed.

Current treatments for MS are generally aimed at suppressing the body's immune system with drugs - and are only of limited help against the advance of the disease.