CSF antibody to myelin basic protein. Measurement in patients with multiple sclerosis and subacute sclerosing panencephalitis.

A solid phase radioimmunoassay was used to detect antibodies to myelin basic protein (MBP) in the CSF of patients with multiple sclerosis (MS) and subacute sclerosing panencephalitis (SSPE). F(ab')2 fragments prepared from SSPE IgG retained their activity, which showed that the assay measures a true antigen-antibody reaction rather than nonspecific adherence to IgG to MBP. Samples of CSF from 48 patients with MS and 30 patients with SSPE were tested and, in both conditions, antibody activity was significantly greater than in controls, when tested at identical IgG concentrations. In MS, levels of antibody were highest in patients with acute exacerbations and lower in patients in remission, which supported the hypothesis that autoimmunity to a myelin antigen may play a role in the pathogenesis of the disease. The reaction with MBP was consistently more pronounced in SSPE than in MS. In view of the association of SSPE with measles virus and the presence of high titers of measles antibody in the CSF, antibodies to measles and to MBP may be directed against similar antigenic determinants.