Identification of the kappa and lambda light chains within the CSF immunoglobulin region in multiple sclerosis and subacute sclerosing panencephalitis by immunofixation after isoelectric focusing

The Increasing Role of Kappa Free Light Chains in the Diagnosis of Multiple Sclerosis

Free light chains (FLC) are a promising biomarker to detect intrathecal inflammation in patients with inflammatory central nervous system (CNS) diseases, including multiple sclerosis (MS). The diagnostic use of this biomarker, in particular the kappa isoform of FLC ("KFLC"), has been investigated for more than 40 years. Based on an extensive literature review, we found that an agreement on the correct method for evaluating KFLC concentrations has not yet been reached. KFLC indices with varying cut-off values and blood-CSF-barrier (QAlbumin) related non-linear formulas for KFLC interpretation have been investigated in several studies. All approaches revealed high diagnostic sensitivity and specificity compared with the oligoclonal bands, which are considered the gold standard for the detection of intrathecally synthesized immunoglobulins. Measurement of KFLC is fully automated, rater-independent, and has been shown to be stable against most pre-analytic influencing factors. In conclusion, the determination of KFLC represents a promising diagnostic approach to show intrathecal inflammation in neuroinflammatory diseases. Multicenter studies are needed to show the diagnostic sensitivity and specificity of KFLC in MS by using the latest McDonald criteria and appropriate, as well as standardized, cut-off values for KFLC concentrations, preferably considering non-linear formulas such as Reiber's diagram.

Urine free light chains in SLE: clonal markers of B-cell activity and potential link to in vivo secreted Ig

As a marker of in vivo B-cell activity, urine levels of free light chain (FLC) were measured twice weekly by radioimmunoassay (RIA) and correlated with disease activity over periods of 5-10 months in seven patients with systemic lupus erythematosus (SLE). In addition, RIA-measured urine albumin was used to track glomerular injury, and alpha1-microglobulin (alpha1-M) levels, 28- to 32-kDa protein, provided control measurements on excretion of low-molecular-weight proteins. As controls, urine FLC levels were obtained from healthy normals and in subjects with acute pharyngitis, sickle-cell anemia, and acute sepsis or pneumonia. The control results showed that with acute sepsis/pneumonia had marked increases in urine FLC, while pharyngitis and sickle-cell controls had normal FLC levels. In SLE, active patients receiving intravenous cyclophosphamide and high-dose steroids exhibited highly increased urine FLC that fluctuated widely during therapy and fell to normal range levels with disease remission. During active SLE, urine albumin often was increased, while alpha1-M levels remained in normal range. In contrast to the increased FLC of active disease, inactive patients on low-dose maintenance therapy had predominantly normal FLC levels throughout the collection period. These results support our hypothesis that longitudinal levels of urine FLC can be used to track disease-related B-cell activity in SLE. Furthermore, we suggest that the urine FLC of active SLE would share LC idiotype with the clonal associated in vivo secreted Ig, and thus permit the identification of these antibodies that are targeted to the culprit immunogen(s) responsible for the pathogenesis of SLE.

Is progressive multifocal leukoencephalopathy associated with intrathecal IgG synthesis?

Examination of the cerebrospinal fluid by isoelectric focusing was done in 2 cases of progressive multifocal leukoencephalopathy (PML). The diagnosis was confirmed at autopsy in one case. IgG oligoclonal bands were found in both, suggesting that there was intrathecal immunoglobulin synthesis. Production may be due to a specific intrathecal response to papova virus or to IgG oligoclonal formation by lymphoma cells confined to the central nervous system or to a specific immune response to tumor cell antigens.

Increase of predominantly k-type light chains in the CSF of a case of subacute sclerosing panencephalitis treated with interferon

The results of a study of the CSF protein pattern in a case of SSPE treated with interferon are reported. An increase in the IgG, IgG index and CNS IgG synthesis values was found during and after the period of treatment. The electrophoretic and IEF patterns show a predominant increase in the L-chain bands, principally k-type, which are anti-measles antibodies. It is suggested that interferon could stimulate some cell clones to synthesize a particular type of L-chains.