Radioimmunoassay of the myelin basic protein in biological fluids, conditions improving sensitivity and specificity

The radioimmunoassay (RIA) for myelin basic protein (MBP) in biological fluids was reassessed in order to improve its sensitivity and eliminate some interferences. By using the preincubation technique and the charcoal-dextran-horse serum mixture for the separation step, the detection limit could be lowered to 200 pg/ml for cerebrospinal fluids (CSF), amniotic fluids (AF) and nervous tissue extracts and 600 pg/ml for sera. The RIA could be used directly on CSF, AF and nervous tissue extracts. Sera, however, had to be heated in citrate buffer at 100 degrees C in order to discard interfering material. The present method is 10 to 20 times more sensitive than others previously published. Moreover, it can be applied to amniotic fluid. The biological fluids had to be promptly frozen to avoid degradation of MBP.