An improved radioimmunoassay for myelin basic protein-like immunoreactive material in cerebrospinal fluid

A modified radioimmunoassay protocol is described which can measure elevated levels of myelin basic protein-like immunoreactive material in the cerebrospinal fluid of some patients with multiple sclerosis or head injury and in rats developing an acute demyelinating form of experimental allergic encephalomyelitis. The assay uses synthetic peptides that differ in their sequences from natural myelin basic protein for both standard and radioligand, but in apparent contrast to previously published assays serial dilutions of samples produce the expected dose estimates when interpolated from the standard curve. A second radioimmunoassay was produced with high sensitivity and specificity for myelin basic protein peptides with a carboxyl terminus at phenylalanine 89. This assay was used in attempts to detect the myelin basic protein-like immunoreactivity recently reported to occur in human urine. This radioimmunoassay failed to detect specific immunoreactivity in urine samples from control and multiple sclerosis donors. The specificities of both assays were studied using a wide range of synthetic peptides and the importance of this information to the design of future assays is addressed. Our work reinforces that of others in suggesting the complex situation involved in the design of assays for MBP fragments in body fluids. We are willing to distribute the reagents for use in our CSF assay to researchers who request them.