Oligoclonal bands

Oligoclonal bands (OCBs) are bands of immunoglobulins that are seen when a patient's blood serum, or cerebrospinal fluid (CSF) is analyzed.

Two methods of analysis are possible: (a) protein electrophoresis, a method of analyzing the composition of fluids, also known as "agarose gel electrophoresis/Coomassie Blue staining", and (b) the combination of isoelectric focusing/silver staining. The latter is more sensitive.

For the analysis of cerebrospinal fluid, a patient has a lumbar puncture performed, which collects some of his or her cerebrospinal fluid. The blood serum can be gained from a clotted blood sample. Normally it is assumed that all the proteins that appear in the CSF but are not present in the serum are produced intrathecally (inside the CNS). Therefore, it is normal to subtract bands in serum from bands in CSF when investigating CNS diseases.

OCBs are specially important for multiple sclerosis. In MS, normally only OCBs made of immunoglobulin G antibodies are considered, though sometimes other proteins can be taken into account, like lipid-specific immunoglobulin M. The presence of these IgM OCBs is associated with a more severe course.

New techniques like "capillary isoelectric focusing immunoassay" are able to detect them in a population higher than 95%.

Even more than 12 OCBs can appear in MS. Each one of them represent proteins (or protein fragments) secreted by plasma cells, although why exactly these bands are present, and which proteins these bands represent, has not yet been fully elucidated. The target antigens for these antibodies is not easy to find because it requires to isolate a single kind of protein in each band, though new techniques are able to do so.

In 40% of MS patients with OCBs, HHV-6 and EBV specific antibodies have been found.

HHV-6 specific OCBs have also been found in other demyelinating diseases. A lytic protein of HHV-6A virus was identified as the target of HHV-6 specific oligoclonal bands.

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