Studies on the inactivation of encephalitogenic myelin basic protein by serum

Abstract

Previous reports that myelin basic protein loses its encephalitogenic activity when incubated in normal serum at 37.degree. C are confirmed. The mechanisms for this were studied. 125I-labeled human myelin basic protein was rapidly degraded by normal guinea pig serum to low MW products as shown by polyacrylamide gel electrophoresis. An intermediate product of MW about 6000 daltons was seen. Plasma had a much lower degradative activity than serum; the half-life of myelin basic protein was 3.8 h in plasma compared with 12 min in serum. Serum degraded myelin basic protein was no longer capable of suppressing experimental allergic encephalomyelitis in the guinea pig nor of eliciting delayed-type hypersensitivity in guinea pigs sensitized to myelin basic protein.