Multiple sclerosis: search for a serologic inhibitor

Complement-fixing (CF) antibrain antibodies are frequently found in serum and CSF in multiple sclerosis (MS). A negative result in the test for these antibodies might depend not only on a lack of antibodies, but also on serologic inhibiting factors. To test this possibility, serum and concentrated CSF samples without demonstrable CF antibrain antibodies were allowed to interact with two standardized positive complement fixation reactions; one for antibrain antibodies and the other a Wasserman reaction. No evidence of inhibiting activity was found in 11 CSF and 15 serum samples from 20 MS patients. On the other hand, inhibiting activity was seen in serum from four of 12 patients with neoplasms and from three of 11 patients with rheumatoid arthritis.