The need for a new strategy for the treatment of multiple sclerosis

Gadolinium-DTPA-enhanced magnetic resonance imaging in experimental optic neuritis

Magnetic resonance imaging (MRI) with gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA) was used to investigate disruption of the blood-optic nerve barrier associated with acute autoimmune demyelination. Leakage of Gd-DTPA was seen in the optic nerves and optic chiasm of adult guinea pigs sensitized for acute experimental allergic encephalomyelitis, but not in normal unsensitized animals. This finding occurred as early as 5 to 8 days after antigenic sensitization with the myelin emulsion and before the onset of paralysis or ataxia. Pathologic examination at this early stage of experimental allergic encephalomyelitis showed an absence of demyelination in the optic nerves and optic chiasm, although scant perivascular foci of inflammatory cells were seen. Leakage of Gd-DTPA in the optic nerve before demyelination of this white matter tract illustrates that increased permeability of the blood-optic nerve barrier is an early, if not the initial, event in autoimmune demyelination, and the optic nerve is a common site of central nervous system involvement during the initial phase of acute experimental allergic encephalomyelitis. Findings in this animal model appear comparable with the results of MRI with Gd-DTPA in patients with optic neuritis, and they suggest that disruption of the blood-optic nerve barrier is a common denominator for both disorders of primary demyelination.

Nervous and immune system disorders in multiple sclerosis

Multiple sclerosis is probably an acquired infectious disease with an autoimmune response relating to damage to the white matter of the central nervous system. There is evidence of continued intrathecal synthesis of oligoclonal antibody and there are perivascular inflammatory cell infiltrates close to areas of demyelination in the central nervous system. Following adoptive transfer, cells sensitized to the myelin basic protein can cause demyelinating disease in rodent recipients. Unlike the peripherally-mediated immune changes in the experimental model it is argued that autoaggressive cells are generated within the CNS in multiple sclerosis. The possible mechanism of cellular demyelination is discussed and the implication for therapy is reviewed.