Interferon can help moderate the devastating attacks of one form of multiple sclerosis, reports a new study.

Fifteen patients with relapsing-remitting multiple sclerosis "experienced fewer and milder attacks" while they were receiving injections of alpha interferon -- a natural substance found in the body -- concludes a double-blind study reported in the journal Neurology. These same patients experienced more attacks when they were injected with a placebo during another phase of the study.

An estimated 250,000 Americans, many of them young adults, are afflicted with MS -- a chronic and gradually debilitating disease of the central nervous system. There are no known cures or treatments. As a result, MS patients often try treatments with no proven medical benefit.

How interferon helps is still unknown. One theory is that this substance -- produced in minute quantities in the body -- suppresses the abnormal immune responses believed to occur in MS patients. Another possibility is that interferon may cut the incidence of common viral infections that sometimes preceed a relapse.

The research, conducted at the University of California (San Francisco), Scripps Clinic and Research Foundation and Stanford University, is considered "preliminary but promising." Yet interferon probably won't help all MS patients: In the study, nine patients with chronic, progressive MS showed no improvement from the injections.