Discrimination of elevated immunoglobulin concentrations in CSF due to inflammatory reaction of the central nervous system and blood-brain-barrier dysfunction.

Inflammatory reactions of the central nervous system (CNS) are diagnosed by the determination of elevated immunoglobulin concentrations in cerebrospinal fluid (CSF) due to local production of immunoglobulins. However, unspecific disturbances of the blood-brain-barrier (BBB) can also cause an increase of CSF immunoglobulin concentration as a result of filtration from blood serum. The methods described here attempt a more precise characterization of immunoglobulins in CSF and to define that portion of CSF immunoglobulin derived from the CNS. Albumin and the immunoglobulin fractions IgG, IgA and IgM are determined in serum and CSF. The ratio of albumin in serum and CSF is taken as an indicator of BBB function. By the determination of quotients an overproportional immunoglobulin elevation in CSF as expression of an inflammatory reaction of the CNS can be detected. Methodological problems and the definition of normal ranges are discussed.