Oligoclonal free kappa and lambda bands in the cerebrospinal fluid of patients with multiple sclerosis and other neurological diseases. An immunoaffinity-mediated capillary blot study

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.

Determination of chitinase 3-like 1 in cerebrospinal fluid in multiple sclerosis and other neurological diseases

Objectives

Chitinase 3-like 1 (CHI3L1) is an extracellular monomeric single-chain glycoprotein expressed by many types of cells. Its elevated levels were found in cerebrospinal fluid in central nervous system (CNS) inflammatory diseases patients. The aim of the study was 1) to validate the reference interval of cerebrospinal fluid (CSF) CHI3L1 in a control group; 2) to measure the CHI3L1 concentration in different diagnosis groups .including multiple sclerosis (MS); and 3) to correlate those values with other biomarkers of axonal damage or neuroinflammation in different grous.

Methods

The study included 132 CSF samples sent to the Department of Clinical Biochemistry, Institute of Laboratory Diagnostics, University Hospital Ostrava. Concentrations of CHI3L1, CXCL13 chemokine, neurofilament light chains, and phosphorylated neurofilament heavy chains were determined by enzyme-linked immunosorbent assays. IgG oligoclonal bands were detected by isoelectric focusing in agarose gels followed by immunofixation. IgM and FLC oligoclonal bands were analyzed by IEF followed by affinity immunoblotting. The group consisted of 42 patients with multiple sclerosis, 14 with clinically isolated syndrome, 11 with other central nervous system inflammatory diseases, 46 with non-inflammatory diseases of the central nervous system, 4 with inflammatory diseases of the peripheral nervous system, and 15 controls.

Results

The estimated reference values of CHI3L1 were 28.6–182.5 μg.L^-1. Statistically significant differences of CSF CHI3L1 concentrations were found among diagnosis groups (p < 0.0001), after age adjustment (p = 0.002). There was a statistically significant relationship between CHI3L1 and NFL in the MS group (r_s = 0.460; P = 0.002), and between CHI3L1 and pNFH in the MS group (r_s = 0.691; P < 0.001). No statistically significant difference was found in the categorical comparison of CHI3L1 in the MS group and other diagnostic groups as well as when using the Mann-Whitney U test for CHI3L1 with additional parameters with and without oligoclonal bands present.

Conclusions

CSF CHI3L1 values differ depending on diagnosis and correlate significantly with concentrations of the axonal damage markers CSF neurofilament light chains, and CSF phosphorylated neurofilament heavy chains, but not with CSF concentrations of the inflammatory marker CXCL13. Thus, CSF CHI3L1 could be another promising prognostic, albeit probably etiologically nonspecific, biomarker of MS.

Free Kappa light chains in neuroinflammatory disorders: Complement rather than substitute?

OBJECTIVES

The detection of cerebrospinal fluid (CSF)-specific IgG oligoclonal bands (OCB) by isoelectric focusing (IEF) is widely used to help diagnose inflammatory neurological disorders (IND), including multiple sclerosis. However, the quantification of free light chains (FLC) is increasingly evaluated as a surrogate method to determine the presence of an intrathecal inflammatory process. The objective of this study was to evaluate the diagnostic performance of kappa (κ) FLC measurement in comparison with OCB detection by IEF.

MATERIAL AND METHODS

We measured serum and CSF κFLCs by turbidimetry using the SPA_plus automated analyser and calculated the κ index in 142 samples from OCB-positive and negative MS, as well as from patients with inflammatory and non-inflammatory neurological disorders (IND and NIND).

RESULTS

The κFLC index was significantly increased in OCB-positive MS and IND patients versus OCB-negative patients. Its performance was relatively comparable to that of IEF for MS diagnosis. When using a κFLC index cutoff value of 6.29, sensitivity increased from 61.2% to 75.7% in comparison with IEF for diagnosing IND (P = .0051), with a slightly lower non-statistically significant specificity (82.1% vs 100%). When considering both OCB status positivity or a κFLC index superior to 6.29 to diagnose IND status, sensitivity raised to 80.6% (P < .05) with an equal specificity.

CONCLUSION

Our results demonstrate that the κFLC index does not discriminate MS from other IND patients, but is a reliable technique to detect intrathecal inflammation. However, κFLC quantification should probably be considered as a complementary method, rather than a substitute, to OCB detection.

Chemiluminescent detection of oligoclonal immunoglobulins after isoelectric focusing and affinity-mediated immunoblotting

BACKGROUND AND AIMS

Detection of oligoclonal IgG (o-IgG) in the cerebrospinal fluid (CSF) not found in serum is the principal laboratory test to support a diagnosis of multiple sclerosis. The aim of this study was to compare chemiluminescent and chromogenic detection of oligoclonal immunoglobulins in the cerebrospinal fluid and serum after their separation by means of isoelectric focusing followed by immunoblotting.

METHODS

A set of experiments was designed to detect oligoclonal immunoglobulins by means of alkaline phosphatase BCIP/NBT substrate and chemiluminescent peroxidase substrate.

RESULTS

Based on visual evaluation of signals, chemiluminescent detection requires about a 4 times lower amount of applied protein than very sensitive BCIP/NBT chromogenic detection. Very good correlation between methods has been shown for oligoclonal IgG. Antigen-specific oligoclonal IgG could be demonstrated by both methods although the pattern was clearer using chemiluminescence. In one patient, oligoclonal IgD bands barely visible by BCIP/NBT were convincingly demonstrated by chemiluminescence.

CONCLUSION

Chemiluminescent detection is a feasible option for oligoclonal immunoglobulin detection and could be used in cases when the sensitivity needs to be improved. Further studies and method optimisation are warranted.

Assessment of Intrathecal Free Light Chain Synthesis: Comparison of Different Quantitative Methods with the Detection of Oligoclonal Free Light Chains by Isoelectric Focusing and Affinity-Mediated Immunoblotting

Objectives

We aimed to compare various methods for free light chain (fLC) quantitation in cerebrospinal fluid (CSF) and serum and to determine whether quantitative CSF measurements could reliably predict intrathecal fLC synthesis. In addition, we wished to determine the relationship between free kappa and free lambda light chain concentrations in CSF and serum in various disease groups.

Methods

We analysed 166 paired CSF and serum samples by at least one of the following methods: turbidimetry (Freelite™, SPA_PLUS), nephelometry (N Latex FLC™, BN ProSpec), and two different (commercially available and in-house developed) sandwich ELISAs. The results were compared with oligoclonal fLC detected by affinity-mediated immunoblotting after isoelectric focusing.

Results

Although the correlations between quantitative methods were good, both proportional and systematic differences were discerned. However, no major differences were observed in the prediction of positive oligoclonal fLC test. Surprisingly, CSF free kappa/free lambda light chain ratios were lower than those in serum in about 75% of samples with negative oligoclonal fLC test. In about a half of patients with multiple sclerosis and clinically isolated syndrome, profoundly increased free kappa/free lambda light chain ratios were found in the CSF.

Conclusions

Our results show that using appropriate method-specific cut-offs, different methods of CSF fLC quantitation can be used for the prediction of intrathecal fLC synthesis. The reason for unexpectedly low free kappa/free lambda light chain ratios in normal CSFs remains to be elucidated. Whereas CSF free kappa light chain concentration is increased in most patients with multiple sclerosis and clinically isolated syndrome, CSF free lambda light chain values show large interindividual variability in these patients and should be investigated further for possible immunopathological and prognostic significance.

Intrathecal IgG synthesis: a resistant and valuable target for future multiple sclerosis treatments

Intrathecal IgG synthesis is a key biological feature of multiple sclerosis (MS). When acquired early, it persists over time. A growing body of evidence suggests that intrathecal Ig-secreting cells may be pathogenic either by a direct action of toxic IgG or by locally secreting bystander toxic products. Intrathecal IgG synthesis depends on the presence of CNS lymphoid organs, which are strongly linked at anatomical level to cortical subpial lesions and at clinical level to the impairment slope in progressive MS. As a consequence, targeting CNS lymphoid lesions could be a valuable new target in MS, especially during the progressive phase. As intrathecal IgGs are end-products of these lymphoid lesions, intrathecal IgG synthesis may be considered as a specific marker of the persistence of these inflammatory lesions. Here we review the effect upon intrathecal IgG synthesis of all drugs ever used in MS. Except for steroids, all these therapeutic strategies, including rituximab, failed to decrease intrathecal IgG synthesis, with the exception of a questionable incomplete action of natalizumab. Thus, IgG synthesis is a robust marker of persistent intrathecal inflammation and its complete normalization should be one of the goals in future therapeutic strategies.

Oligoclonal free light chains in cerebrospinal fluid as markers of intrathecal inflammation. Comparison with oligoclonal IgG

AIMS

To compare the sensitivity and specificity of CSF-restricted oligoclonal IgG and free light chains as markers of multiple sclerosis and other inflammatory neurological diseases.

METHODS

196 paired CSF and serum samples were examined for oligoclonal IgG and oligoclonal free light chains. The sensitivity and specificity of the tests were calculated and optimal cut-offs for the number of CSF-restricted oligoclonal bands were then determined by analysis of receiver operating characteristic curves.

RESULTS

Optimal cut-off values were ≥5 IgG bands for multiple sclerosis, ≥4 IgG bands for inflammatory neurological disease, ≥6 free κ, and ≥2 free λ bands for both purposes. Using these cut-off values, sensitivities and specificities for multiple sclerosis were 83.8% and 91.3% for IgG, 83.8% and 81.0% for free κ, and 67.6% and 75.4% for free λ. For inflammatory neurological disease, sensitivities and specificities were 60.8% and 95.7% for IgG, 69.6% and 92.6% for free κ, and 64.8% and 86.2% for free λ.

CONCLUSIONS

Although exact cut-off values may vary according to method, reporting borderline results as positive, may compromise the specificity of the test and should be avoided.. The detection of intrathecal free light chain synthesis may be of value especially when the oligoclonal IgG test is negative or borderline, even though its specificity is slightly lower.

Cerebrospinal fluid analysis

The cerebrospinal fluid (CSF) is a bodily fluid, which is both easily accessible and the most proximate to the pathological alterations of multiple sclerosis (MS). Consequently, the analysis of this fluid provides an important window into the pathological underpinnings of this disease. For example, for years, it has been known that the CSF of MS patients contains oligoclonal gamma immunoglobulins (IgG), which are synthesized within the central nervous system and presumably relate to the immune dysfunction, which is characteristically found in MS. This insight has lead to the introduction of highly-effective anti-B-cell therapies into the field of MS therapeutics. Moreover, the presence of an oligoclonal IgG response in the CSF, although not specific for MS, is a very sensitive finding and, as a result, its presence can be quite helpful for establishing an MS diagnosis in the right clinical context. In addition, this finding has predictive value. Thus, patients without a definite diagnosis who have CSF IgG bands are significantly more likely to develop definite MS compared to those patients without such a banding pattern. Other biological molecules can also be found in the CSF including neurofiliment, myelin basic protein (MBP), glial fibrillary acidic protein (GFAP), tau, neuronal cell adhesion molecule (NCAM), and the growth associated protein (GAP-43). However, the value of measuring these (and other) CSF constituents for both diagnostic and prognostic purposes and for following response to therapy is still to be determined.

Detection of oligoclonal IgG kappa and IgG lambda bands in cerebrospinal fluid and serum with Hevylite™ antibodies. comparison with the free light chain oligoclonal pattern

Background

Oligoclonal IgG bands in cerebrospinal fluid that are absent in serum indicate intrathecal IgG synthesis and are a sensitive marker of CNS inflammatory diseases, in particular multiple sclerosis. It may be of interest to determine whether these bands are predominantly IgGκ or IgGλ.

Methods

We have used Hevylite™ antibodies and developed a technique for detection of oligoclonal IgGκ and IgGλ bands by means of isoelectric focusing followed by immunoblotting. The same technique was used for oligoclonal free κ and free λ detection. Among several techniques tested, affinity immunoblotting appears to be the most sensitive; it can detect less than 1 ng of IgGκ or IgGλ paraprotein. We compared oligoclonal IgG profiles with those of oligoclonal IgGκ and IgGλ. There was good agreement concerning the presence or absence of intrathecal synthesis. We observed the ratios between oligoclonal IgGκ and IgGλ bands, and they did not always match the ratios between free κ and free λ bands. We were also able to detect antigen-specific CSF-restricted oligoclonal IgGκ and IgGλ bands in neuroborreliosis. It remains to be determined subsequently by a clinically-oriented prospective study, whether predominant IgGκ/IgGλ or free κ/free λ can be observed more frequently in particular diseases with oligoclonal IgG synthesis.

Discussion

Very sensitive detection of oligoclonal IgGκ and IgGλ bands in cerebrospinal fluid with Hevylite antibodies is feasible; detection of antigen-specific IgGκ or IgGλ is possible as well. In particular situations, e.g. when difficulties arise in distinguishing between oligoclonal and monoclonal pattern, the test may be of considerable clinical value.

Differential cerebro spinal fluid proteome investigation of Leber hereditary optic neuropathy (LHON) and multiple sclerosis

Leber's hereditary optic neuropathy (LHON) is a genetic disease leading to the loss of central vision and optic nerve atrophy. The existence of occasional cases of LHON patients developing a Multiple Sclerosis (MS)-like illness and the hypothesis that mtDNA variants may be involved in MS suggest the possibility of some common molecular mechanisms linking the two diseases. We have pursued a comparative proteomics approach on cerebrospinal fluid (CSF) samples from LHON and MS patients, as well as healthy donors by employing 2-DE gel separations coupled to MALDI-TOF-MS and nLC-MS/MS investigations. 7 protein spots showed significant differential distribution among the three groups. Both CSF of LHON or MS patients are characterized by lower level of transthyretin dimer adduct while a specific up regulation of Apo A-IV was detected in LHON CSF.

The role of antibody affinity for specific antigens in the differential diagnosis of inflammatory nervous system disorders

Affinity maturation has previously been shown with assays for total IgG for specific antigens using the technique of competition by chaotropic ions. We have extended this technique to individual clones and followed the maturation of clones during the course of herpes encephalitis. This has important implications for our understanding of the pathogenesis of multiple sclerosis.

Comparaison de l’immunofixation après électrophorèse sur gel d’agarose avec la focalisation isoélectrique dans la détection des bandes oligoclonales d’IgG du liquide céphalo-rachidien de patients atteints de sclérose en plaques

INTRODUCTION

Intrathecal immunoglobulins (Ig) synthesis, reflected by oligoclonal bands (OCBs) in cerebrospinal fluid (CSF) is observed in up to 90 percent of patients with clinically definite Multiple Sclerosis (MS). The gold standard laboratory test to establish the presence of OCBs in CSF of MS patients is isoelectric focusing (IEF). However, a quicker and less expensive method has been developed: immunofixation (IF).

METHODS

The aim of this study was to compare these two methods carried out 74 CSF/serum pairs of MS, 103 CSF/serum pairs of subject controls and to determine their sensitivity and specificity.

RESULTS

The agreement between results from IEF and IF was excellent (Kappa = 0.84). IEF sensitivity (78 percent) was not significantly different from that of IF (74 percent) (p = 0.3). Similarly, the specificity of IEF (93 percent) was not significantly different from that of IF (95 percent) (p = 0.2).

CONCLUSION

IF is a semi automated method which is easier to perform than IEF and which appears to be as efficient as IEF.

Quantification of Immunoglobulin Free Light Chains in CerebroSpinal Fluid by Nephelometry

Oligoclonal free light chains (FLC) banding has been described in multiple sclerosis (MS) and should be correlated with disease activity. However, discrepancies between studies have been reported because of differences in methods. A new quantitative, rapid, and automated method using nephelometry is now available. Our objective was to investigate the interest of this method for the diagnosis and prognosis of MS. For this purpose, FLC index was determined in paired samples of CSF and serum from consecutive and unselected patients from the same department of neurology. We enrolled 89 patients (33 MS, 15 "possible MS", and 41 controls) and correlated with IgG index, IgG oligoclonal banding, and clinical MS progression criteria. The main results were (1) FLC kappa index was more sensitive but less specific than IgG index for the diagnosis of MS, (2) two MS patients were negative for oligoclonal banding but exhibited a positive kappa index, (3) no relation between FLC kappa indices, MS clinical criteria, and disease progression was found. In conclusion, FLC kappa index should be considered as a useful complementary test for MS diagnosis. Its pronostic interest remains to be determined on a larger cohort of possible MS patients.

Kappa Free Light Chains in Cerebrospinal Fluid as Markers of Intrathecal Immunoglobulin Synthesis

Background: Intrathecal immunoglobulin synthesis is observed in several inflammatory disorders of the central nervous system, but its detection by current laboratory tests is either tedious or relatively insensitive. We assessed the diagnostic accuracy of an assay for κ free light chains (κFLC) in cerebrospinal fluid (CSF) and serum, and compared it with traditional tests for intrathecal immunoglobulin synthesis.

Methods: κFLCs were measured by nephelometry in CSF/serum pairs from 112 patients. Samples were excluded if blood contamination of CSF as a result of traumatic lumbar puncture (n = 12) or monoclonal bands in both CSF and serum (n = 5) were present. The remaining sample pairs were grouped according to the presence (n = 71) or absence (n = 24) of oligoclonal bands. Data were analyzed as κFLC concentrations in CSF, as κFLC CSF/serum ratios, and by use of the quotient diagram described previously for immunoglobulins.

Results: Both κFLC concentrations in CSF and the κFLC CSF/serum ratio identified patients with oligoclonal bands with high specificity and sensitivity. The areas under the ROC curves were 0.991 (95% confidence interval, 0.944–0.998) and 0.978 (0.924–0.996), respectively. Exclusion of patients with impaired blood–CSF barrier function further improved diagnostic accuracy. To account for patients with impaired blood–CSF barrier function, data were also analyzed in a quotient diagram. Only two patients without detectable oligoclonal bands would have been misclassified by this approach.

Conclusions: Our data indicate that the nephelometric assay for κFLCs in CSF reliably detects intrathecal immunoglobulin synthesis. This automated and quantitative method could simplify the diagnostic procedure for CSF analysis in the routine laboratory.

Detection of Oligoclonal Immunoglobulins in Cerebrospinal Fluid by an Immunofixation-Peroxidase Method

Background: The detection of intrathecal synthesis of immunoglobulins is used in the diagnosis of multiple sclerosis (MS). We tested the semiautomated immunofixation-peroxidase (IFPOD) technique, which uses high-resolution agarose gel electrophoresis (HRAGE) directly followed by immunofixation with a peroxidase-labeled anti-IgG antiserum to detect oligoclonal immunoglobulins in cerebrospinal fluid (CSF).

Methods: We analyzed 230 consecutive matched serum/CSF pairs that arrived in the laboratory over a 6-month period with both IFPOD and our routine techniques, immunofixation electrophoresis (IFE) and HRAGE. For IFPOD, CSF samples were not concentrated before testing.

Results: Among the 230 samples were 12 clinically definite MS, 33 clinically probable, and 20 clinically possible MS samples. IFPOD and HRAGE + IFE each detected oligoclonal IgG in CSF in 10, 16, and 7 cases of these respective groups. For clinically definite MS, sensitivity and specificity (95% confidence intervals) were, respectively, 83% (51–97%) and 79% (73–84%).

Conclusions: The IFPOD technique performs comparably to other analytical methods, without the requirement for sample concentration, and may represent an attractive alternative in testing for intrathecal immunoglobulin synthesis.

The intrathecal humoral immune response: laboratory analysis and clinical relevance

In normal conditions, albumin and immunoglobulin (Ig)G in the cerebrospinal fluid (CSF) originate from the blood, and there is no antibody production within the central nervous system. Up to 20% of CSF proteins are intrathecally synthesized, but the major fraction is blood-derived. The CSF/serum albumin quotient (QAlb) is the best marker of the blood-CSF barrier function. The corresponding immunoglobulin quotients (QIGG, QIGA, QIGM) are not linearly related to QAlb and their correlations are defined by an hyperbolic equation. This equation is used to discriminate between a blood-derived and a locally produced fraction of immunoglobulins in case of an intrathecal humoral immune response. The detection of CSF-specific oligoclonal IgG is more sensitive than the quantitative comparison between QIGG and QAlb. A further step is the determination of antibody indices and the detection of specific oligoclonal antibodies by antigen-driven immunoblots. CSF analysis remains a cornerstone for the diagnosis of various neurological disorders, including multiple sclerosis and infectious diseases of the central nervous system.

Intrathecal synthesis of free immunoglobulin light chains in multiple sclerosis

OBJECTIVE

The detection of oligoclonal immunoglobulin free light chains (FLC) in the diagnosis of multiple sclerosis (MS) was compared to IgG isoelectric focusing.

MATERIAL AND METHODS

Cerebrospinal fluid and serum samples from 69 patients with possible first attacks of MS, 50 patients with clinically definite MS (CDMS), and 118 patients with other neurological diseases (OND) were analyzed. IgG and FLC oligoclonal bands were detected by isoelectric focusing and immunoperoxidase staining.

RESULTS

Intrathecal synthesis of IgG, kappa FLC, and lambda FLC oligoclonal bands, respectively, was seen in 92%, 92%, and 86% of MS patients; in 61%, 62%, and 64% of patients with possible first attacks of MS; and in 3%, 3%, and 8% of the patients with OND. In control patients without IgG synthesis intrathecal lambda FLC synthesis was more common than kappa FLC synthesis (P=0.03).

CONCLUSION

Kappa FLC detection proved as useful as IgG analysis for the laboratory diagnosis of MS whereas the presence of intrathecal lambda FLC synthesis was less specific.

Can CSF predict the course of optic neuritis?

To discuss the implications of CSF abnormalities for the course of acute monosymptomatic optic neuritis (AMON), various CSF markers were analysed in patients being randomly selected from a population-based cohort. Paired serum and CSF were obtained within a few weeks from onset of AMON. CSF-restricted oligoclonal IgG bands, free kappa and free lambda chain bands were observed in 17, 15, and nine of 27 examined patients, respectively. Sixteen patients showed a polyspecific intrathecal synthesis of oligoclonal IgG antibodies against one or more viruses. At 1 year follow-up five patients had developed clinically definite multiple sclerosis (CDMS); all had CSF oligoclonal IgG bands and virus-specific oligoclonal IgG antibodies at onset. Due to the relative small number studied at the short-term follow-up, no firm conclusion of the prognostic value of these analyses could be reached. CSF Myelin Basic Protein-like material was increased in only two of 29 patients with AMON, but may have potential value in reflecting disease activity, as the highest values were obtained among patients with CSF sampled soon after the worst visual acuity was reached, and among patients with severe visual impairment. In most previous studies of patients with AMON qualitative and quantitative analyses of CSF IgG had a predictive value for development of CDMS, but the results are conflicting.

Intrathecal synthesis of virus-specific oligoclonal IgG, and of free kappa and free lambda oligoclonal bands in acute monosymptomatic optic neuritis. Comparison with brain MRI

Twenty-seven patients with acute monosymptomatic optic neuritis were randomly selected from a population-based cohort of patients extensively screened for known etiologies of ON. Paired serum and CSF obtained median 20 days from onset were examined for oligoclonal IgG, free kappa and free lambda chains, and virus-specific oligoclonal IgG antibodies by an affinity-mediated capillary blot technique. CSF-restricted oligoclonal IgG bands, free kappa and free lambda chain bands were observed in 17, 15 and nine patients, respectively. In addition, 16 patients showed a polyspecific intrathecal synthesis of oligoclonal IgG antibodies against one or more viruses (12 measles, nine varicella zoster, six rubella, six mumps) compared to all the 18 examined patients with definite multiple sclerosis (P = 0.0014). The presence of virus-specific oligoclonal IgG was significantly related to the results of oligoclonal IgG (P = 0.0034), free kappa chain bands (P = 0.0020), and brain MRI abnormalities (P = 0.0402). At 1 year follow-up five patients had developed clinically definite multiple sclerosis; all had virus-specific oligoclonal IgG antibodies, oligoclonal IgG and abnormal MRI at onset.

Detection of CSF-specific oligoclonal antibodies to recombinant JC virus VP1 in patients with progressive multifocal leukoencephalopathy

The intrathecal synthesis of antibodies against recombinant VP1, the major structural protein of JC virus (JCV), was studied in 18 patients with progressive multifocal leukoencephalopathy (PML) and in 31 patients with various neurological disorders. Two methods were used, the calculation of an antibody specific index (ASI) on one hand and an antigen-driven immunoblotting for the detection of oligoclonal antibodies on the other. Most PML patients displayed an elevated (> 1.5) ASI (78%) and anti-VP1 oligoclonal antibodies restricted to the cerebrospinal fluid (55%). Only two other patients (one case each of multiple sclerosis and of neuroborreliosis) also showed an intrathecal synthesis of anti-VP1 oligoclonal antibodies, likely as a result of a 'polyspecific' reaction within the central nervous system.

Cerebrospinal fluid free kappa light chains versus IgG findings in neurological disorders: qualitative and quantitative measurements

In this study free kappa light chains in cerebrospinal fluid (CSF) were determined both by an affinity mediated capillary blotting technique after isoelectric focusing (IEF) in agarose gel and by a quantitative enzyme linked immunosorbent assay (ELISA). The free kappa results were compared with the IgG findings in 4 neurological patient groups with a distinct CSF IgG pattern: (1) CSF without oligoclonal IgG bands, (2) CSF with serum derived IgG bands, (3) CSF restricted IgG bands and (4) CSF restricted and serum derived IgG bands. Oligoclonal free kappa bands are nearly absent in CSF of groups 1 + 2, and present in 88% of group 3 and 84% of group 4 patients. We could also establish free kappa indices from specimens in the 4 groups in analogy to IgG indices. Group 1 had a median free kappa index of 1.1, group 2: 1.0 and groups 3 + 4: 10.0. The correspondence between immunoblot and index findings for free kappa is better than for IgG. Free kappa index is more sensitive but somewhat less specific than IgG index for establishing intrathecal immune production.

The intrathecal synthesis of virus-specific oligoclonal IgG in multiple sclerosis

A highly sensitive antigen-mediated capillary blot technique was developed for the detection of virus-specific oligoclonal IgG in paired CSF and serum samples from patients with various neurological diseases. In multiple sclerosis, intrathecal synthesis of oligoclonal antibodies was present against measles (70%), rubella (60%), varicella zoster (40%) and mumps (30%); in most cases (75%), such synthesis involved two or more viruses. In contrast, antibodies against a non-neurotropic virus (cytomegalovirus) were rarely produced in CSF from MS patients (5%). However, this 'polyspecific' reaction was not restricted to MS samples but was also observed in neurolupus and in the late phase of infectious diseases of the central nervous system. These anti-viral antibodies could be produced without de novo replication of the corresponding viral genome and are likely mere bystanders of an ongoing immune response.

Cerebrospinal fluid in the diagnosis of multiple sclerosis: a consensus report

The Committee of the European Concerted Action for Multiple Sclerosis (Charcot Foundation) organised five workshops to discuss CSF analytical standards in the diagnosis of multiple sclerosis. This consensus report from 12 European countries summarises the results of those workshops. It is hoped that neurologists will confer with their colleagues in clinical chemistry to arrange the best possible local practice. The most sensitive method for the detection of oligoclonal immunoglobulin bands is isoelectric focusing. The same amounts of IgG in parallel CSF and serum samples are used and oligoclonal bands are revealed with IgG specific antibody staining. All laboratories performing isoelectric focusing should check their technique at least annually using "blind" standards for the five different CSF and serum patterns. Quantitative measurements of IgG production in the CNS are less sensitive than isoelectric focusing. The preferred method for detection of blood-CSF barrier dysfunction is the albumin quotient. The CSF albumin or total protein concentrations are less satisfactory. These results must be interpreted with reference to the age of the patient and the local method of determination. Cells should be counted. The normal value is no more than 4 cells/microliters. Among evolving optional tests, measurement of the combined local synthesis of antibodies against measles, rubella, and/or varicella zoster could represent a significant advance if it offers higher specificity (not sensitivity) for identifying chronic rather than acute inflammation. Other tests that may have useful correlations with clinical indices include those for oligoclonal free light chains, IgM, IgA, or myelin basic protein concentrations.

Occurrence of oligoclonal IgM bands in the cerebrospinal fluid of neurological patients: an immunoaffinity-mediated capillary blot study

We developed a highly sensitive and specific immunoaffinity-mediated capillary blot technique for the detection of oligoclonal IgM bands in CSF and sera from patients with various neurological disorders. Pre-treatment of the samples by dithiothreitol was necessary to obtain a migration of the IgM molecule into the gel of isoelectric focusing. IgM was then transferred by immunoaffinity onto a polyvinylidene difluoride sheet previously coated with anti-IgM antiserum. The limit of detection was found to be 6 ng in 15-microliters samples. The presence of CSF-restricted IgM bands was considered the result of an intrathecal synthesis and was observed in 13 out of 46 (28%) patients with MS, more frequently in acute relapses (9 out of 21, 43%), including 6 cases out of 13 presenting the first bout of the disease. Similar IgM bands were also detected in 15 out of 46 (38%) patients with CNS infections, especially in cases of neurosyphilis and neuroborreliosis. The presence of CSF oligoclonal IgM bands was linked to an increase of the IgM index in the MS group, but not in the group of infectious diseases as a whole. The occurrence of CSF-restricted oligoclonal IgM bands seems to be the most specific indicator of an intrathecal synthesis of this isotype.

Polyclonal and oligoclonal IgA synthesis in the cerebrospinal fluid of neurological patients: an immunoaffinity-mediated capillary blot study

An intrathecal synthesis of IgA has been reported in various neurological disorders. However, the frequency of its occurrence and the electrophoretic characteristics of the locally produced IgA remained a matter of controversy. We developed a sensitive immunoaffinity-mediated capillary blot technique for the detection of polyclonal and oligoclonal IgA in the CSF of 115 patients with various neurological disorders. Paired CSF and serum samples containing 50 ng IgA after appropriate dilutions were submitted to isoelectric focusing in agarose gels; IgA was then blotted onto a polyvinylidene difluoride sheet coated by an anti-IgA antiserum or by infectious antigens. The immunoblots were revealed by an alkaline phosphatase-conjugated anti-IgA antiserum. Only five samples displayed CSF-restricted oligoclonal IgA bands, including two out of 33 from MS patients. In herpetic encephalitis (n = 5) and varicella-zoster meningitis (n = 2), a strong intrathecal production of virus-specific IgA antibodies was detectable. In such cases, faint oligoclonal IgA antibodies were superimposed on a polyclonal background. A weak local production of anti-Borrelia burgdorferi IgA antibodies was present in two out of four cases of neuroborreliosis.

Clinical applications of immunoglobulin free light chain estimations

The relevance of free light chain assays to diagnosis, staging, treatment and prognosis assessment in B-cell disorders (including myeloma, chronic lymphocytic leukaemia, and lymphoma), multiple sclerosis and diabetes is discussed and their actual and potential use is examined.