The cellular immunology of multiple sclerosis

Multiple sclerosis (MS) is a neurological disease that affects the central nervous system (brain and spinal cord) resulting in debilitating motor and sensory dysfunction. Its mean age of onset is 30 years and, with the exception of trauma, MS remains the most frequent cause of neurological disabilities for young adults. The disease is highly variable in its onset and progression. It may not be easily diagnosed, at least in its earliest stages. Significant disability is a hallmark of MS. Indeed, up to 50% of patients require walking aids and 10% are wheelchair-bound at 15 years after an initial diagnosis. Clinical features include deficits in sensory (parasthesias and numbness), motor (difficulties with fine movements and gait), balance, bladder, and sexual functions. Although the etiology for MS is not yet known, it is thought to be related to microbial, genetic, and/or environmental factors. Pathologically, MS is characterized by inflammation. An influx of mononuclear cells occurs through a disrupted blood-brain barrier into an immune-privileged central nervous system. The secretion of a variety of inflammatory cytokines and chemokines from glial cells leads to loss of myelin, disruption of oligodendrocyte integrity, and axonal loss. These events, in large measure, affect progressive neural atrophy. How brain inflammatory activities affect transendothelial migration of leukocytes into the brain and alter the process of myelination are the focal points for MS research activities.