Evidence for humoral autoimmunity in neuromyelitis optica.

Neuromyelitis optica (NMO) is an idiopathic central nervous system (CNS) demyelinating syndrome that may be distinguished from typical multiple sclerosis (MS). Although the cause of the disorder is not known, several lines of evidence suggest that the fundamental immunological process is driven by humoral mechanisms. These observations include the frequent coexistence of systemic autoimmune disease or positive serum autoantibodies with NMO, immunopathologic studies that demonstrate prominent complement activation and immunoglobulin deposition and the discovery of the serum autoantibody NMO-IgG, a potential NMO biomarker that targets aquaporin-4. Furthermore, clinical experience suggests that plasmapheresis and immunosuppressive therapies are beneficial for treatment and prevention of acute attacks but that standard MS immunomodulatory drugs may not alter the course of NMO. This evidence is reviewed in the context of its implications for future laboratory and clinical research in NMO.