Binding of encephalitogenic basic protein by serum alpha-globulins

Abstract

The binding capacity of human and rabbit serum and serum fractions for [¹²⁵I]encephalitogenic basic protein, extracted from human brain, were determined by gel-filtration radioimmunoassay. Strong binding was effected by the γ-globulin fraction or whole serum of a rabbit with experimental allergic encephalitis, and was completely inhibited by excess of unlabelled encephalitogenic basic protein but not by large amounts of lysozyme. Smaller amounts of encephalitogenic basic protein were bound by normal rabbit and human serum, and by the serum of a patient with multiple sclerosis: the α₂-macroglobulin fraction was responsible for this, and complete inhibition was effected by excess unlabelled encephalitogenic basic protein but only partial inhibition by excess lysozyme. It is concluded that binding detected in some radioimmunoassay systems may not represent a classical antigen—antibody reaction, and it is suggested that α-macroglobulins may, by binding in vivo, be of importance in experimental allergic encephalomyelitis and, by analogy, in human demyelinating disease.