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

Abstract

The binding of partially purified multiple sclerosis (MS) specific brain antigens (MSG2) and of the corresponding antigens of non-MS brains (KG2) to the IgG in cerebrospinal fluid (CSF) of patients with MS and other neurological diseases were assayed employing sandwich enzyme linked immunosorbent assay (ELISA) technique. The brain antigens were bound to the wells in micro-ELISA plates, followed by the binding of CSF-IgG to the antigens, and finally peroxidase labelled rabbit antihuman IgG was bound to the CSF-IgG. The activity of peroxidase expressed as optical density (OD) of the enzyme released chromophore was considered as a measure of antigen-antibody binding. Initial studies revealed an antigen dose dependent increase in the binding of brain antigens with the IgG in undiluted CSF until an optimal (maximal) binding was achieved. Assay of antigen-antibody binding revealed that the concentration of MSG2 required for the optimal binding with the IgG in the undiluted MS CSF was significantly lower than that of KG2. The index for IgG binding capacity of an antigen (IgBC) was expressed as a ratio of the OD of the colour formed 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 various antigens in the MSG2 may be present in the CSF of MS patients.