Acute optic neuritis: myelin basic protein and proteolipid protein antibodies, affinity, and the HLA system.

Anti-myelin basic protein, anti-proteolipid protein, and anti-myelin basic protein peptide (amino acid residues 1-20, 63-88, and 89-101) antibody-secreting cells were studied in 20 patients with idiopathic optic neuritis, 20 with optic neuritis as part of multiple sclerosis, and 20 neurological control subjects. Antibody-secreting cells were enumerated with an immunospot assay; the relative binding affinity of the antibodies was estimated by elution with thiocyanate. Patients with optic neuritis had more anti-myelin basic protein and anti-proteolipid protein antibodies than did control subjects (both p < 0.05); there was no difference between idiopathic optic neuritis and optic neuritis as a symptom of multiple sclerosis. Presence of the multiple sclerosis-associated DRB1*1501 gene was not associated with preferential synthesis of high-affinity antibodies reactive with a single myelin basic protein peptide or with preferential synthesis of either anti-myelin basic protein or anti-proteolipid protein antibodies. The results demonstrate a potential for intrathecal synthesis of both anti-myelin basic protein and anti-proteolipid protein antibodies of high apparent affinity in patients with optic neuritis.