Radioimmunological Determination of Myelin Basic Protein (MBP) and MBP-Antibodies

Optimal conditions for radioiodinating of MBP by the chloramine T method are described. Adsorption on CM cellulose was found to be the best way to separate 125T-MBP from inorganic iodine. Iodination and purification can be performed in less than 30 min. The iodinated MBP was used for radioimmunological determination of antibodies against MBP and of MBP itself. The immunoreactivity of iodinated MBP was independent of the extent of iodination, by which an upper level of 8 radio iodine atoms/molecule could be reached. Therefore, it is possible to develop a radioimmunoassay of high sensitivity. The optimal conditions for formation of the antibody-MBP complex were investigated. The complex was isolated using gel filtration on Sephadex or dextran-coated charcoal. Both gave the same results, but the charcoal procedure is far more rapid. Antibody titration curves and MBP standard curves were performed. Bovine and human MBP, which differ from each other in molecular weight and amino acid sequence, were shown to give a complete cross-reaction with antibodies against human MBP. In a preliminary study in sera cerebrospinal fluids of patients with multiple sclerosis humural antibodies to human MBP could not be detected, whereas in serum of a patient with a second cerebrovascular accident MBP antibodies were found.