Monoclonal immunoglobulin bands in the cerebrospinal fluid

Isoelectric focusing and immunofixation allow the detection of abnormal immunoglobulin bands in the cerebrospinal fluid (CSF). In normal subjects, the immunoglobulins in the CSF are derived from serum. In inflammatory disorders of the nervous system, there may be intrathecal immunoglobulin synthesis usually seen as oligoclonal bands confined to the CSF. Monoclonal immunoglobulin bands in the CSF are not common. We surveyed 1490 CSF samples, and found that a total of nine had a monoclonal immunoglobulin band and that in three this was not present in the serum. Of these three, one patient had chronic inflammatory demyelinating polyneuropathy and the antibody may have been secreted by lymphocytes which had infiltrated the nervous system. The other patients had either lymphoma or lymphomatoid granulomatosis within or adjacent to the nervous system and the monoclonal immunoglobulin was probably secreted by B lymphocytes within those lesions.