Cerebrospinal fluid isoelectric focusing

The most characteristic abnormality in patients with multiple sclerosis is certainly the intrathecal synthesis of IgG. It can be demonstrated—with different sensitivity— by various methods, which can be divided into qualitative and quantitative methods. The gold standard for the demonstration of intrathecal synthesis of IgG is the detection of oligoclonal bands, which are not present in CSF, in the appropriately diluted serum (i.e., to the same concentration of IgG) by isoelectric focusing. This is a qualitative method and the description of its different modifications and interpretations goes beyond the scope of this chapter. This method is by far the most sensitive, and its sensitivity is reported between 90 and 100%. Here it is suitable to repeat that the detection of plasmocytic forms in cerebrospinal fluid may also be regarded as qualitative proof of intrathecal synthesis of immunoglobulins— although in this case the proof is obviously not specific for IgG from the theoretical point of view. 

Ol. Olsson, T., Kostulas, V., and Link, H., Improved detection of oligoclonal IgG in cerebrospinal fluid by isoelectric focusing in agarose, double-antibody peroxidase labeling, and avidin-biotin amplification. Clin. Chem. 30/7, 1246-1249 (1984). 

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Staugaitis, S. M., Shapshak, R, Tourtellotte, W. W., etal. Isoelectric focusing of unconcentrated cerebrospinal fluid Applications to ultrasensitive analysis of oligoclonal immunoglobulin G. Electrophoresis 6, 287-291 (1985). 

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Storstein A, Monstad SE, Honnorat J, Vedeler CA. Paraneoplastic antibodies detected by isoelectric focusing of cerebrospinal fluid and serum. J Neuroimmunol 2004 155(1-2) 150-154. 

SI 1. Souverijn, J. H., Peet, R., Smit, W. G., Serree, H. M., andBruyn, G. W., TheHAF enigma Origin and clinical consequences of the appearance of high alkaline fractions on isoelectric focusing patterns of cerebrospinal fluid. J. Neurol. Sci. 97(1), 117-128 (1990). 

Fortini AS, Sanders EL, Weinshenker BG, Katzmann JA (2003) Cerebrospinal fluid oligoclonal bands in the diagnosis of multiple sclerosis. Isoelectric focusing with IgG immunoblotting compared with high-resolution agarose gel electrophoresis and cerebrospinal fluid IgG index. Am J Clin Pathol 120 672-675. 

Hiroaka, A. et al.. Charge microheterogeneity of the fi-trace proteins (lipocalin-type prostaglandin D synthase) in the cerebrospinal fluid of patients with neurological disorders analyzed by capillary isoelectric focusing. Electrophoresis, 22, 3433, 2001. 

Isoelectric focusing for specific applications such as cerebrospinal fluid oligoclonal bands is of more specialist interest. Immunoelectrophoresis (i.e., electrophoresis followed by the application of specific antibodies) for typing monoclonal gammopathies (myelomas) is the procedure of choice. Capilliary electrophoresis offers the opportunity to determine genotypes for homo or heterozygotes of, e.g., enzyme defects, following polymerase chain reaction. 

See also Blood and Plasma. Capillary Electrophoresis Overview. Cerebrospinal Fluid. Clinical Analysis Sample Handling. Electrophoresis Principles Isoelectric Focusing Polyacrylamide Gels Clinical Applications. Immunoassays Overview. Immunoassays,... 

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