CSF antibodies to myelin basic protein and to myelin-associated glycoprotein in multiple sclerosis. Evidence of the intrathecal production of antibodies.

Cerebrospinal fluid (CSF) from 40 multiple sclerosis (MS) patients was tested by solid-phase radioimmunoassay (RIA) for ability to bind 2 common structural components of myelin and oligodendroglia, i.e., to bind myelin basic protein (MBP) and myelin-associated glycoprotein (MAG). To prevent the effect of differences in CSF IgG concentration on binding activity, the CSF samples were tested at equal IgG concentration 1 mg/ml. The mean binding activity to MBP and MAG was significantly higher than in control neurotics, respectively P less than or equal to 0.05 and P less than or equal to 0.001. In 33% of MS cases, CSF antibody against both antigens was found. Indirect data were obtained that autoantibodies whose antigens are associated with myelin-oligodendrocyte unit are produced locally within the central nervous system (CNS). Anti-MAG and anti-MBP CSF antibody activity was significantly higher, P less than or equal to 0.01 for both antibody specificity, in MS cases characterized by high IgG Index, greater than or equal to 0.70 = means + SD in the neurotic group, versus MS cases characterized by normal IgG Index (less than or equal to 0.70). Correlation coefficient between antibody activity and IgG Index values was 0.785 for anti-MBP antibody, and 0.400 for anti-MAG antibody. The importance of intrathecally produced antibody to MBP and MAG lies in the fact that it indicates an active humoral autoimmune process against a myelin-oligodendrocyte unit in which more than one autoantigen is involved.