Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) characterized by infiltration of T lymphocytes and macrophages into white matter leading to demyelination [1-2]. This pathology is frequently associated with disability of neurological function, in particular sensory deficits, visual problems and paralysis. The acute MS plaques are markered by the presence of activated T cells expressing the IL-2 receptor as well as activated, class II MHC positive macrophages [3-4]. In addition, cytokines such as TNF and oligoclonal immunoglobulin have been found in the brain and cerebrospinal fluid (CSF) of patients with MS [5-7]. This active inflammatory process is confined to the CNS, not affecting either the peripheral nervous system or other organs. Although it is generally accepted that this CNS inflammatory process causes demyelination and the resulting neurologic disability in MS, the mechanism(s) by which the inflammation is initiated and maintained is unknown.