Serum oligoclonal IgG is a common and persistent finding in multiple sclerosis, and has a systemic source

Synthesis of oligoclonal IgG within the central nervous system is a wellestablished feature of multiple sclerosis. The occurrence of oligoclonalIgG in the serum of patients with multiple sclerosis has received littleattention. We detected such a serum response in 20/45 consecutive patients(44%, 95% CI 30-59%) but in only 3/41 age- and sex- matched healthycontrols (p < 0.01). We present qualitative and quantitative evidencethat this oligoclonal IgG has a systemic origin. The plasma cell clonesresponsible for the serum response are often also represented in theintrathecal compartment. In a further study of the clinical significance ofserum oligoclonal bands, in 80 patients, their presence was associated withelevated levels of intrathecal synthesis, increasing age, later diseaseonset and the presence of serum autoantibodies. These findings add to theevidence that there is a systemic immune disturbance in multiple sclerosis.