Determination of immunoglobulin content of CSF based on light chain characteristics.

The immunoglobulin light chain (types kappa and lambda) content of normal cerebrospinal fluid is similar to that of normal serum. In inflammatory diseases of the central nervous system a shift in the k/l ratio in comparison to serum values, usually a relative increase of Igk, can be observed. This increase of the k/l ratio, though not specific for any disease, is most commonly found in multiple sclerosis. There is no correlation between the IgG content and the k/l ratio. The methods described here measure bound and free light chains simultaneously. The calculations show that free light chains are present in both normal and inflammatory CSF and that they appear to be of polyclonal origin. The detection of light chain abnormalities in CSF can be taken as an indicator of endogenous immunoglobulin production in the CNS and is of significance for the diagnosis of inflammatory CNS processes, especially when other signs of endogenous immunoglobulin production are absent.