Estimation of levels of IgG to multiple sclerosis specific brain antigens in the cerebrospinal fluid of MS patients

The binding of partially purified multiple sclerosis (MS) specific brain antigens (MSG2) and of the corresponding antigens of non-MS brains (KG2) to cerebrospinal fluid IgG of patients with MS and other neurological diseases was assayed employing sandwich enzyme linked immunosorbent assay (ELISA). Assay of the antigen-antibody binding revealed that the concentration of MSG2 required for the optimum binding to IgG in the undiluted MS CSFs was lower than that of KG2 in all cases. The index for IgG binding capacity of an antigen (IgBC) was expressed as a ratio of the optical density of the enzymic products in ELISA at the optimal antigen-antibody binding to the lowest concentration of the antigen required for the optimal binding. The IgBC of MSG2 was found to be linearly correlated with the IgG concentration in the CSF of MS patients. These results indicate that IgG with specificity to MSG2 may be present in the CSF of MS patients.