Oligoclonal bands are a about two to five bands of immunoglobulins. Each band is in a protein secreted by plasma cells. They are found in spinal fluid and blood serum in some persons. They are discovered by testing the fluids on a gel which reveals the bands.

The presence of Oligoclonal bands in spinal fluid often indicates a disease of the Central Nervous System if the bands are not also found in blood serum, however the presence of one band, called monoclonal, is not serious and may be normal. The bands usually disappear from the spinal fluid as a person recovers from the neurological disease.

Approximately 90% of all patients with Multiple Sclerosis have these bands. For those who possibly have the disease, these bands are an important indicator. The bands are permanent in these patients.