 Multiple sclerosis MS is the major disabling neurologic disease of young adults,and represents the most common immune-mediated inflammatory and demyelinating disorder of the central nervous system CNS. Active inflammatory lesions contain components that include T cells, macrophages, and activated microglia. Within these lesions myelin is removed, axons are damaged and oligodendrocytes may be lost. In lesions undergoing inflammatory demyelination axonal injury also occurs. The disability MS produces is underscored by the nearly fifty percent of patients who will require ambulatory aids within 15 years after disease onset. 