The role of autoantibodies in the pathogenesis of multiple sclerosis (MS) and other demyelinating diseases is controversial, in part because widely used western blotting and ELISA methods either do not permit the detection of conformation-sensitive antibodies or do not distinguish them from conformation-independent antibodies. We developed a sensitive assay based on self-assembling radiolabeled tetramers that allows discrimination of antibodies against folded or denatured myelin oligodendrocyte glycoprotein (MOG) by selective unfolding of the antigen domain. The tetramer radioimmunoassay (RIA) was more sensitive for MOG autoantibody detection than other methodologies, including monomer-based RIA, ELISA or fluorescent-activated cell sorting (FACS). Autoantibodies from individuals with acute disseminated encephalomyelitis (ADEM) selectively bound the folded MOG tetramer, whereas sera from mice with experimental autoimmune encephalomyelitis induced with MOG peptide immunoprecipitated only the unfolded tetramer. MOG-specific autoantibodies were identified in a subset of ADEM but only rarely in adult-onset MS cases, indicating that MOG is a more prominent target antigen in ADEM than MS.The role of autoantibodies in the pathogenesis of human demyelinating diseases of the central nervous system (CNS) is an important, unresolved issue. In animal models, autoantibodies that recognize epitopes on the surface of myelin or myelin-producing oligodendrocytes can enhance demyelination 1,2 . A monoclonal antibody (8-18C5) against myelin oligodendrocyte glycoprotein (MOG) induces severe demyelination in mice and rats with mild experimental autoimmune encephalomyelitis (EAE) but does not induce disease in healthy animals because the antibody cannot gain access to the CNS parenchyma 1,2 . MOG is a minor component of myelin but is localized on the outer surface of the multilamellar myelin structure and is thus accessible to antibodies, whereas more abundant antigens such as myelin basic protein are inaccessible in intact myelin 1 . In the marmoset primate model of EAE, immunization with MOG induces a chronic demyelinating disease with pathological features reminiscent of MS (ref. 3). In mouse models, however, severe demyelination is observed in the absence of antibodies and B cells 4 , indicating that autoantibodies are not required for demyelination in all species.These elegant studies in animal models have shown the demyelinating potential of autoantibodies to myelin surface proteins, but their role in the pathogenesis of human inflammatory demyelinating diseases such as MS and acute disseminated encephalomyelitis (ADEM) is far less certain. MOG has been extensively studied as a potential target antigen for autoantibodies in MS (refs. 5-8) Unlike MS, ADEM typically has a rapidly progressive clinical presentation that includes encephalopathy 11 . The disease course is usually self limiting, although in a minority of cases relapses may occur. The pathogenic relationship between MS and ADEM is unclear, and it remains to be d...

Multiple sclerosis (MS) typically manifests in early to mid adulthood, but there is increasing recognition of pediatric-onset MS, aided by improvements in imaging techniques. The immunological mechanisms of disease are largely unexplored in pediatric-onset MS, in part because studies have historically focused on adult-onset disease. We investigated autoantibodies to myelin surface Ags in a large cohort of pediatric MS cases by flow cytometric labeling of transfectants that expressed different myelin proteins. Although Abs to native myelin oligodendrocyte glycoprotein (MOG) were uncommon among adult-onset patients, a subset of pediatric patients had serum Abs that brightly labeled the MOG transfectant. Abs to two other myelin surface Ags were largely absent. Affinity purification of MOG Abs as well as competition of binding with soluble MOG documented their binding specificity. Such affinity purified Abs labeled myelin and glial cells in human CNS white matter as well as myelinated axons in gray matter. The prevalence of such autoantibodies was highest among patients with a very early onset of MS: 38.7% of patients less than 10 years of age at disease onset had MOG Abs, compared with 14.7% of patients in the 10- to 18-year age group. B cell autoimmunity to this myelin surface Ag is therefore most common in patients with a very early onset of MS.