Binding of 125 I myelin basic protein by serum and cerebrospinal fluid.

A sensitive gel filtration redioimmunoassay was used to test for antibodies to the basic protein of myelin, the antigen of experimental autoimmune encephalomyelitis, in serum and cerebrospinal fluid (CSF) of patients with multiple sclerosis (MS) and other diseases. Sera and CSF from patients with MS gave results similar to those for controls including subjects with various neurological diseases. Binding of I-basic protein by seven-fold concentrated CSF was shown to be due to α-globulin. Free basic protein, as a possible auto-immunogen, was sought in the serum and seven-fold concentrated CSF of patients with MS and controls by competitive inhibition in the radioimmunoassay, but none was demonstrable. If an immunological mechanism is to be invoked in the initiation of destruction of the basic protein of myelin in MS, then either pathogenic `antibody' must be absorbed to the target antigen in the central nervous system or the initiating events must be mediated entirely by sensitized lymphocytes.