CSF oligoclonal bands

In normal individuals all the immunoglobulins present in the CSF are derived by filtration from the plasma across the blood-brain barrier. In certain inflammatory conditions however, activated B lymphocytes can migrate from the peripheral circulation into the perivascular space where they differentiate into plasma cells. These cells secrete their immunoglobulins directly into the brain extracellular space from where they diffuse into the CSF. Such immunoglobulins are known as locally synthesized, intracranial or de novo produced immunoglobulins. Locally synthesized immunoglobulins can be identified because they produce a characteristic pattern of bands on electrophoresis which is unique to the CSF. This pattern is known as an oligoclonal pattern and it is widely accepted that each group of bands represents the product of a separate clone of activated B-cells or plasma cells.

Oligoclonal bands (of intrathecal origin) occur in three groups of Central nervous system (CNS) disease:-

A) demyelinating disorders, typically multiple sclerosis, when the pattern is predominantly one of bands in the CSF but absent from the serum (approx 5 % of patients will also show bands in the serum).

B) in chronic CNS infections where bands are present in both CSF and serum, but generally more bands are present in the CSF than in the serum.

c) in a miscellaneous group of diseases that are possibly autoimmune in origin, where the patterns in the CSF and serum are usually but not always the same. If there is neurological involvement, additional bands may be found in the CSF.