NEW YORK (Reuters Health) - Patients with multiple sclerosis (MS) may benefit from treatment with a substance that influences the immune response, called interferon beta-1a (INF-beta). According to researchers, treating MS patients with INF-beta when symptoms of MS are just emerging may prevent later relapse.

MS causes the immune system to attack the body's own nerve cells because it sees them as ``foreign,'' causing changes in vision, muscle weakness and other symptoms. The disease may progress steadily, or sudden attacks may be followed by a temporary remission of symptoms. At some point, however, patients may convert to what is called ``clinically definite'' MS, in which symptoms become irreversible.

A team of European researchers led by Dr. Giancario Comi with the University of Milan, Italy, wanted to test whether INF-beta could prevent relapse in patients if it was given to them shortly after their first MS attack.

The investigators injected a total of 241 patients with either INF-beta or an inactive placebo once a week for 2 years. During that time, the researchers examined the patients every 6 months and performed MRI brain scans every 12 months.

Fewer patients receiving INF-beta showed signs of clinically definite MS than did patients receiving placebo. Only 34% of the INF-beta group showed signs, compared with 45% of the placebo group. The patients receiving INF-beta who did convert tended to do so after a much longer period of time than did the patients receiving placebo.

According to Comi, INF-beta acts in multiple ways on the function of the immune system, which is why it may help patients with MS.

``Treatment given early in the course of MS might therefore affect the subsequent course of the disease, by decreasing the amount of inflammation,'' the researchers write in the May 19th issue of The Lancet.

``The results are in line with what we expected, because the rationale of the study was that even low doses of INF-beta can be active in the early phases of the disease,'' Comi told Reuters Health.

Comi suggested that MS patients should discuss with their doctor the possibility of starting treatment right away after the first attack if the disease continues to be active. But he also pointed out that ``we need new trials evaluating whether patients in the early phases of the disease can benefit more from higher doses of IFN-beta,'' he said.