Occurrence of oligoclonal IgM bands in the cerebrospinal fluid of neurological patients: an immunoaffinity-mediated capillary blot study.

We developed a highly sensitive and specific immunoaffinity-mediated capillary blot technique for the detection of oligoclonal IgM bands in CSF and sera from patients with various neurological disorders. Pre-treatment of the samples by dithiothreitol was necessary to obtain a migration of the IgM molecule into the gel of isoelectric focusing. IgM was then transferred by immunoaffinity onto a polyvinylidene difluoride sheet previously coated with anti-IgM antiserum. The limit of detection was found to be 6 ng in 15-microliters samples. The presence of CSF-restricted IgM bands was considered the result of an intrathecal synthesis and was observed in 13 out of 46 (28%) patients with MS, more frequently in acute relapses (9 out of 21, 43%), including 6 cases out of 13 presenting the first bout of the disease. Similar IgM bands were also detected in 15 out of 46 (38%) patients with CNS infections, especially in cases of neurosyphilis and neuroborreliosis. The presence of CSF oligoclonal IgM bands was linked to an increase of the IgM index in the MS group, but not in the group of infectious diseases as a whole. The occurrence of CSF-restricted oligoclonal IgM bands seems to be the most specific indicator of an intrathecal synthesis of this isotype.