Cerebrospinal fluid antibodies to myelin basic protein in acute idiopathic optic neuritis.

Free and bound levels of anti-myelin basic protein (anti-MBP) antibodies were measured by radioimmunoassay in the cerebrospinal fluid of 20 patients with acute idiopathic optic neuritis, 133 patients with multiple sclerosis (MS) divided into three clinical subgroups, and 76 normal control subjects. Patients with idiopathic optic neuritis had elevated levels of anti-MBP predominantly in free form, resulting in an elevated (above unity) free/bound anti-MBP ratio similar to that of MS patients with acute relapses. These data suggest that acute idiopathic optic neuritis, like active MS, is associated with anti-MBP.