Determination of k/l immunoglobulin light chain ratios in CSF from patients with multiple sclerosis and other neurological diseases.

Using antisera against Bence-Jones protein, the concentration of light chains type k and l can be determined in CSF. The calculation of the ratio of type k to type I light chains in CSF represents a sensitive measure for the evaluation of immunological processes involving the CNS. Our results demonstrate that an increase k/l ratio is encountered in 48% of CSF specimen from multiple sclerosis (MS) patients, but also in 50% from patients with other inflammatory diseases involving the CNS, in contrast to only 18% from other neurological diseases. In none of the MS or inflammatory cases is the altered k/l ratio the only indicator of a CNS inflammation, most commonly it is accompanied by an overproportional CSF-IgG elevation (increased QG ratio), an increased cell count or both. For these reasons determination of CSF k/l ratios is helpful in the differentiation of MS and other neurological diseases, but not for the differentiation of other inflammatory CNS diseases from MS.