Relation between Genetic markers and oligoclonal IgG in CSF in optic neuritis

Thirty patients with acute, unilateral optic neuritis (ON), where re-examination after a mean observation period of 5 years did not reveal any aetiology, were investigated with regard to laboratory abnormalities frequently observed in multiple sclerosis. Eleven patients had oligoclonal IgG in CSF. In 5 of these a measles virus antibody response within the CNS was demonstrable. The remaining 19 patients did not display oligoclonal CSF IgG, nor an antibody response. The major histocompatibility antigens HL-A3 and HL-A7 occurred at similar frequencies in ON and in controls, irrespective of the presence of oligoclonal CSF IgG. The HL-A7 associated MLC determinant LD-7a occurred in ON at a frequency between that observed in controls and in MS. However, an association of the same magnitude as observed in MS was found between ON with oligoclonal CSF IgG and the presence of LD-7a. This association was absent in those ON patients who lacked oligoclonal CSF IgG. The present data indicate that the finding of oligoclonal CSF IgG may increase the risk of developing MS.