Serum and cerebrospinal fluid C2 in multiple sclerosis.

C2 hemolytic activity was quantitated in the serum and cerebrospinal fluid of 46 MS patients studied twice at a 1-year interval. whereas serum C2 levels were found within the normal range, CSF C2 values were decreased (55 and 59% of normal) in patients with severe active disease. In contrast CSF C2 levels were normal in patients with stable or recently improved condition. CSF C2 fluctuations in individuals were found to closely parallel changes in the clinical course.