Myelin encephalitogenic protein fragments in cerebrospinal fluid of persons with multiple sclerosis.

With a double-antibody radioimmunoassay performed on unconcentrated cerebrospinal fluid, eight of 14 patients in an acute phase of multiple sclerosis had levels of 3.4 to 15.4 ng per milliliter of the P1 fragment (residues 43-88) of myelin encephalitogenic protein. Encephalitogenic protein-P1 was found only in the acute phase and was present in six of seven persons in the first week of an exacerbation and absent in 29 multiple sclerosis patients who were stable or had a gradually progressive course. Six of 117 controls had detectable cerebrospinal fluid encephalitogenic protein-P1. Only in two of these, one with a recent cerebral infarction and one with diabetic nephropathy who was in coma, were the levels in the range encountered in patients in the acute phase of multiple sclerosis. Although not entirely specific for multiple sclerosis, the presence of material in the cerebrospinal fluid of multiple sclerosis patients cross-reacting with encephalitogenic protein-P1 appears to be a characteristic of acute exacerbations.