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Oligoclonal bands (OCBs) are bands of immunoglobulins that are seen when a patient's blood serum, or cerebrospinal fluid (CSF) is analyzed.
Contents
- Oligoclonal bands in multiple sclerosis
- Diagnostic value in MS
- Bands in other diseases
- Diseases associated
- References
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.
Oligoclonal bands in multiple sclerosis
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.
Though early theories assumed that the OCBs were somehow pathogenic autoantigens, recent research has shown that the IgG present in the OCBs are antibodies against debris, and therefore, OCBs seem to be just a secondary effect of MS. Nevertheless, OCBs remain useful as a biomarker.
Diagnostic value in MS
Oligoclonal bands are an important indicator in the diagnosis of multiple sclerosis. More than 95% of all patients with multiple sclerosis have permanently observable oligoclonal bands.
Nevertheless, the main importance of oligoclonal bands is to demonstrate the production of intrathecal immunoglobins (IgGs). Currently alternative methods for detection of this intrathecal synthesis have been published. Specially interesting are the free light chains (FLC), specially the kappa-FLCs (kFLCs). Several authors have reported that the nephelometric and ELISA FLCs determination is comparable with OCBs as markers of IgG synthesis, and kFLCs behave even better than oligoclonal bands.
Bands in other diseases
The presence of one band (a monoclonal band) may be considered serious, such as lymphoproliferative disease, or may simply be normal—it must be interpreted in the context of each specific patient. More bands may reflect the presence of a disease. The bands tend to disappear from the cerebrospinal fluid as a person recovers from the neurological disease.
Diseases associated
Oligoclonal bands are found in: