MS is a chronic autoimmune disease of the central nervous system in which myelin, the protective coat that surrounds nerve cells, is damaged or destroyed by autoimmune T cells and macrophages, leading to an eventual loss of neurologic function. In a pilot study in Europe using high-dose chemotherapy, it was observed that 18 of 19 MS patients stabilized or improved clinically, and only one patient showed a new lesion on magnetic resonance imaging (MRI) of the brain at 4.5 years after treatment. Improvement was seen in quality-of-life assessments.