Identification of IgG subclasses' oligoclonal bands in multiple sclerosis CSF

The elusive nature of the oligoclonal bands in multiple sclerosis

Intrathecal immunoglobulin G (IgG) and oligoclonal bands (OCBs) detected in both the brain and cerebrospinal fluid (CSF) are seminal features of multiple sclerosis (MS). The presence of OCBs correlates with elevated disease burden and severity and supports the diagnosis of MS. Despite numerous investigations into the potential viral and autoantigen targets, the precise antigenic specificity of OCBs has remained elusive. We have little knowledge of the nature regarding these oligoclonal IgG bands. Here, we present compelling evidence highlighting the key findings that both OCBs and intrathecal IgG antibodies are under genetic control and that OCBs originate from clonal B-cells in both the periphery and CNS. We propose that MS OCBs are IgG immune complexes composed of IgG1 and IgG3 antibodies and that the pathological role of OCB stems from the IgG effector functions of these complexes, leading to demyelination and axonal injuries. We present additional evidence regarding the nature of MS OCBs: (1) disease-modifying therapies have been shown to affect CSF OCB; (2) OCBs have also been detected in several neuroinfectious diseases; (3) Epstein-Barr virus (EBV) has been particularly linked with MS pathogenesis, and its association with OCB is an important area of study. Although OCBs are closely associated with MS, more meticulously planned research is necessary to clarify the precise role of OCB in MS, both in terms of disease pathogenesis and diagnosis.

Peripheral B-cell dysregulation is associated with relapse after long-term quiescence in patients with multiple sclerosis

B cells play a major role in multiple sclerosis (MS), with many successful therapeutics capable of removing them from circulation. One such therapy, alemtuzumab, is thought to reset the immune system without the need for ongoing therapy in a proportion of patients. The exact cells contributing to disease pathogenesis and quiescence remain to be identified. We utilized mass cytometry to analyze B cells from the blood of patients with relapse-remitting MS (RRMS) before and after alemtuzumab treatment, and during relapse. A complementary RRMS cohort was analyzed by single-cell RNA sequencing. The R package "Spectre" was used to analyze these data, incorporating FlowSOM clustering, sparse partial least squares-discriminant analysis and permutational multivariate analysis of variance. Immunoglobulin (Ig)A+ and IgG1 + B-cell numbers were altered, including higher IgG1 + B cells during relapse. B-cell linker protein (BLNK), CD40 and CD210 expression by B cells was lower in patients with RRMS compared with non-MS controls, with similar results at the transcriptomic level. Finally, alemtuzumab restored BLNK, CD40 and CD210 expression by IgA+ and IgG1 + B cells, which was altered again during relapse. These data suggest that impairment of IgA+ and IgG1 + B cells may contribute to MS pathogenesis, which can be restored by alemtuzumab.

An appraisal of antigen identification and IgG effector functions driving host immune responses in multiple sclerosis

Increased immunoglobulin G (IgG) antibodies and oligoclonal bands (OCB) are the most characteristic features of multiple sclerosis (MS), a neuroinflammatory demyelinating disease with neurodegeneration at chronic stages. OCB are shown to be associated with disease activity and brain atrophy. Despite intensive research over the last several decades, the antigen specificities of the IgG in MS have remained elusive. We present evidence which supports that intrathecal IgG is not driven by antigen-stimulation, therefore provide reasoning for failed MS antigen identification. Further, the presence of co-deposition of IgG and activated complement products in MS lesions suggest that the IgG effector functions may play a critical role in disease pathogenesis.

Ectopic Lymphoid Follicles in Multiple Sclerosis: Centers for Disease Control?

While the contribution of autoreactive CD4⁺ T cells to the pathogenesis of Multiple Sclerosis (MS) is widely accepted, the advent of B cell-depleting monoclonal antibody (mAb) therapies has shed new light on the complex cellular mechanisms underlying MS pathogenesis. Evidence supports the involvement of B cells in both antibody-dependent and -independent capacities. T cell-dependent B cell responses originate and take shape in germinal centers (GCs), specialized microenvironments that regulate B cell activation and subsequent differentiation into antibody-secreting cells (ASCs) or memory B cells, a process for which CD4⁺ T cells, namely follicular T helper (T_FH) cells, are indispensable. ASCs carry out their effector function primarily via secreted Ig but also through the secretion of both pro- and anti-inflammatory cytokines. Memory B cells, in addition to being capable of rapidly differentiating into ASCs, can function as potent antigen-presenting cells (APCs) to cognate memory CD4⁺ T cells. Aberrant B cell responses are prevented, at least in part, by follicular regulatory T (T_FR) cells, which are key suppressors of GC-derived autoreactive B cell responses through the expression of inhibitory receptors and cytokines, such as CTLA4 and IL-10, respectively. Therefore, GCs represent a critical site of peripheral B cell tolerance, and their dysregulation has been implicated in the pathogenesis of several autoimmune diseases. In MS patients, the presence of GC-like leptomeningeal ectopic lymphoid follicles (eLFs) has prompted their investigation as potential sources of pathogenic B and T cell responses. This hypothesis is supported by elevated levels of CXCL13 and circulating T_FH cells in the cerebrospinal fluid (CSF) of MS patients, both of which are required to initiate and maintain GC reactions. Additionally, eLFs in post-mortem MS patient samples are notably devoid of T_FR cells. The ability of GCs to generate and perpetuate, but also regulate autoreactive B and T cell responses driving MS pathology makes them an attractive target for therapeutic intervention. In this review, we will summarize the evidence from both humans and animal models supporting B cells as drivers of MS, the role of GC-like eLFs in the pathogenesis of MS, and mechanisms controlling GC-derived autoreactive B cell responses in MS.

A pathogenic and clonally expanded B cell transcriptome in active multiple sclerosis

B cells serve as a key weapon against infectious diseases. They also contribute to multiple autoimmune diseases, including multiple sclerosis (MS) where depletion of B cells is a highly effective therapy. We describe a comprehensive profile of central nervous system (CNS)-specific transcriptional B cell phenotypes in MS at single-cell resolution with paired immune repertoires. We reveal a polyclonal immunoglobulin M (IgM) and IgG1 cerebrospinal fluid B cell expansion polarized toward an inflammatory, memory and plasmablast/plasma cell phenotype, with differential up-regulation of specific proinflammatory pathways. We did not find evidence that CNS B cells harbor a neurotropic virus. These data support the targeting of activated resident B cells in the CNS as a potentially effective strategy for control of treatment-resistant chronic disease.

Central nervous system B cells have several potential roles in multiple sclerosis (MS): secretors of proinflammatory cytokines and chemokines, presenters of autoantigens to T cells, producers of pathogenic antibodies, and reservoirs for viruses that trigger demyelination. To interrogate these roles, single-cell RNA sequencing (scRNA-Seq) was performed on paired cerebrospinal fluid (CSF) and blood from subjects with relapsing-remitting MS (RRMS; n = 12), other neurologic diseases (ONDs; n = 1), and healthy controls (HCs; n = 3). Single-cell immunoglobulin sequencing (scIg-Seq) was performed on a subset of these subjects and additional RRMS (n = 4), clinically isolated syndrome (n = 2), and OND (n = 2) subjects. Further, paired CSF and blood B cell subsets (RRMS; n = 7) were isolated using fluorescence activated cell sorting for bulk RNA sequencing (RNA-Seq). Independent analyses across technologies demonstrated that nuclear factor kappa B (NF-κB) and cholesterol biosynthesis pathways were activated, and specific cytokine and chemokine receptors were up-regulated in CSF memory B cells. Further, SMAD/TGF-β1 signaling was down-regulated in CSF plasmablasts/plasma cells. Clonally expanded, somatically hypermutated IgM+ and IgG1+ CSF B cells were associated with inflammation, blood–brain barrier breakdown, and intrathecal Ig synthesis. While we identified memory B cells and plasmablast/plasma cells with highly similar Ig heavy-chain sequences across MS subjects, similarities were also identified with ONDs and HCs. No viral transcripts, including from Epstein–Barr virus, were detected. Our findings support the hypothesis that in MS, CSF B cells are driven to an inflammatory and clonally expanded memory and plasmablast/plasma cell phenotype.

IgG3 + B cells are associated with the development of multiple sclerosis

OBJECTIVES

Disease-modifying therapies (DMTs) targeting B cells are amongst the most effective for preventing multiple sclerosis (MS) progression. IgG3 antibodies and their uncharacterised B-cell clones are predicted to play a pathogenic role in MS. Identifying subsets of IgG3 + B cells involved in MS progression could improve diagnosis, could inform timely disease intervention and may lead to new DMTs that target B cells more specifically.

METHODS

We designed a 31-parameter B-cell-focused mass cytometry panel to interrogate the role of peripheral blood IgG3 + B cells in MS progression of two different patient cohorts: one to investigate the B-cell subsets involved in conversion from clinically isolated syndrome (CIS) to MS; and another to compare MS patients with inactive or active stages of disease. Each independent cohort included a group of non-MS controls.

RESULTS

Nine distinct CD20+IgD-IgG3 + B-cell subsets were identified. Significant changes in the proportion of CD21+CD24+CD27-CD38- and CD27+CD38hiCD71hi memory B-cell subsets correlated with changes in serum IgG3 levels and time to conversion from CIS to MS. The same CD38- double-negative B-cell subset was significantly elevated in MS patients with active forms of the disease. A third CD21+CD24+CD27+CD38- subset was elevated in patients with active MS, whilst narrowband UVB significantly reduced the proportion of this switched-memory B-cell subset.

CONCLUSION

We have identified previously uncharacterised subsets of IgG3 + B cells and shown them to correlate with autoimmune attacks on the central nervous system (CNS). These results highlight the potential for therapies that specifically target IgG3 + B cells to impact MS progression.

Oligoclonal IgG antibodies in multiple sclerosis target patient-specific peptides

IgG oligoclonal bands (OCBs) are present in the cerebrospinal fluid (CSF) of more than 95% of patients with multiple sclerosis (MS), and are considered to be the immunological hallmark of disease. However, the target specificities of the IgG in MS OCBs have remained undiscovered. Nevertheless, evidence that OCBs are associated with increased levels of disease activity and disability support their probable pathological role in MS. We investigated the antigen specificity of individual MS CSF IgG from 20 OCB-positive patients and identified 40 unique peptides by panning phage-displayed random peptide libraries. Utilizing our unique techniques of phage-mediated real-time Immuno-PCR and phage-probed isoelectric focusing immunoblots, we demonstrated that these peptides were targeted by intrathecal oligoclonal IgG antibodies of IgG1 and IgG3 subclasses. In addition, we showed that these peptides represent epitopes sharing sequence homologies with proteins of viral origin, and proteins involved in cell stress, apoptosis, and inflammatory processes. Although homologous peptides were found within individual patients, no shared peptide sequences were found among any of the 42 MS and 13 inflammatory CSF control specimens. The distinct sets of oligoclonal IgG-reactive peptides identified by individual MS CSF suggest that the elevated intrathecal antibodies may target patient-specific antigens.

Intrathecal oligoclonal bands synthesis in multiple sclerosis: is it always a prognostic factor?

BACKGROUND

Oligoclonal IgM (OCMB) and IgG (OCGB) bands were found to be associated with poor multiple sclerosis (MS) prognosis.

OBJECTIVE

We aimed to evaluate the prognostic value of OCMB/OCGB in a cohort of Sardinian MS patients.

MATERIALS AND METHODS

We recruited patients from the University of Cagliari. They underwent lumbar puncture for diagnostic purposes. Demographic and the following clinical data were recorded: clinical course; time to reach EDSS 3 and 6; EDSS at last follow-up; and MS treatments. The influence of gender, clinical course, age at onset, treatments, and OCGB/OCMB on reaching EDSS 3 was analysed using Cox regression. Kaplan-Meier curves were used to study the time to reach EDSS 3 considering OCMB/OCGB and therapies.

RESULTS

The enrolled number of subjects was 503. The variables influencing the achievement of EDSS 3.0 were: male gender (p = 0.005); progressive course (p = 0.001); age at onset (p < 0.001); and disease-modifying drugs (p < 0.001). The OCGB/OCMB status was not significant. Kaplan-Meier analysis showed no difference in time to reach EDSS 3 for patients with and without OCGB or OCMB in both treated and non-treated groups.

CONCLUSION

Our study did not confirm the poor prognostic value of OCMB/OCGB. These results may be influenced by the peculiar genetic background associated with the risk of MS in Sardinians.

The complex relationship between oligoclonal bands, lymphocytes in the cerebrospinal fluid, and immunoglobulin G antibodies in multiple sclerosis: Indication of serum contribution

Introduction

Intrathecal immunoglobulin G (IgG) and oligoclonal bands (OCBs) are the most consistent and characteristic features of Multiple Sclerosis (MS). OCBs in MS are considered products of clonally expanded B cells in the cerebrospinal fluid (CSF), representing the sum of contributions from B cells in the brain. However, large amounts of IgG can be eluted from MS plaques in which lymphocytes are absent, and there is no correlation between levels of plaque-associated IgG and the presence of lymphocytes. It is calculated that it would take 3.2 billion lymphocytes to generate such large amounts of intrathecal IgG (30 mg in 500 ml CSF) in MS patients. Therefore, circulating lymphocytes in CSF could only account for <0.1% of the extra IgG in MS.

Methods

We analyzed clinical laboratory parameters from sera and CSF of 115 patients including 91 patients with MS and 24 patients with other inflammatory central nervous system (CNS) disorders (IC). We investigated the relationship between oligoclonal bands, IgG antibodies, CSF cells, IgG Index, albumin, and total protein.

Results

MS patients have significantly elevated serum concentrations of IgG antibodies, albumin, and total protein, lower levels of lymphocytes, albumin, and total protein in the cerebrospinal fluid, but no difference in CSF IgG concentration compared to those with other inflammatory neurological disorders. Furthermore, in MS there was no linear relationship between the numbers of OCBs, CSF lymphocytes, CSF IgG, and IgG Index, and between serum IgG and serum albumin, but significant correlation between IgG in CSF and serum, and between CSF IgG and CSF albumin.

Conclusion

There are unique differences between MS and patients with other inflammatory neurological disorders. Our data suggest that in MS patient (a) B cells and their products in the CSF may not be the sole source of intrathecal IgG; (b) oligoclonal bands may not be the products of single B cell clones in the CSF; and (c) there is a strong connection between serum components in the peripheral circulation and the central nervous system.

Features of intrathecal immunoglobulins in patients with multiple sclerosis

We have analyzed immunoglobulin (Ig) isotypes and IgG subclasses in cerebrospinal fluid (CSF) and serum of patients with multiple sclerosis (MS) and other neurological diseases to determine whether different Ig isotype patterns correlate with clinical or paraclinical findings and CSF B cell populations. Intrathecal IgG1 synthesis was elevated in MS patients. An increased intrathecal IgM production was found in patients with a higher cerebral MRI lesion burden, whereas other clinical and paraclinical parameters were not associated with a specific Ig isotype or subclass profile. Finally, intrathecal IgG production (IgG1 and IgG3) correlated with the presence of mature B cells and plasma blasts.

Difficulties in the differentiation of chronic inflammatory diseases of the central nervous system--value of cerebrospinal fluid analysis and immunological abnormalities in the diagnosis

OBJECTIVES

A number of neurological syndromes may be evoked by involvement of the nervous system due to systemic diseases such as lupus erythematodes, sarcoidosis, Behçet's disease and Sjögren's syndrome (SS) and may be confounded with another chronic inflammatory disease which is restricted to the central nervous system, e.g. multiple sclerosis (MS). Because of different treatment strategies, it is important to distinguish between these different autoimmune diseases.

RESULTS

Neither clinical signs nor additional analyses such as serological findings or cerebrospinal fluid (CSF) analysis are able to differentiate between the diseases with certainty. Nevertheless, taking all findings together, diagnosis may be possible.

CONCLUSION

Here we compare typical clinical and CSF findings in MS, neurosarcoidosis, neurolupus, neuro-Behçet and nervous system involving SS with special emphasis on those findings allowing differentiation of the respective diseases by reviewing the literature.

[Differential diagnosis of chronic inflammatory diseases of the central nervous system. Cerebrospinal fluid diagnosis and immunological parameters]

A number of neurological syndromes may be evoked by involvement of the nervous system due to systemic diseases such as lupus erythematosus, sarcoidosis, Behcet's disease, and Sjogren's syndrome. Because of different treatment strategies, it is important to distinguish between these different diseases. Neither clinical signs nor additional analyses such as serological findings or cerebrospinal fluid analysis are able to differentiate between the diseases with certainty. Nevertheless, diagnosis may finally be made taking all findings together. Here we compare typical clinical and cerebrospinal fluid findings in neurosarcoidosis, neurolupus, neuro-Behcet, and nervous system involving Sjogren's syndrome, with special emphasis on those findings allowing differentiation of the respective diseases.

New immunopathologic insights into multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory and demyelinating disease of the central nervous system. Although the immune system seems to play an important role in the pathogenesis of disease, target antigens are still uncertain and pathways leading to tissue destruction have not been fully elucidated. Recent studies have significantly contributed to a better understanding of the disease process and broadened our view on possible scenarios of disease initiation and progression. We review the role of the immune system for the manifestation and evolution of MS and discuss different pathogenetic concepts. We conclude with an outlook on future strategies to identify the cause of MS.

Immunoglobulin isotypes reveal a predominant role of type 1 immunity in multiple sclerosis

IgG, its subclasses and IgE concentrations were measured in cerebrospinal fluid (CSF) and serum of multiple sclerosis (MS) patients and matched controls as surrogate markers for type 1 and type 2 immunity. IgE indices were significantly reduced in MS patients compared to controls. In contrast, IgG1 was elevated in CSF of MS patients and elevated indices indicated intrathecal synthesis. Because isotype switching to IgE and IgG4 is driven by type 2 immunity and occurrence of IgG1 has previously been found in type 1 immunity-dominated diseases, the results underscore a role of type 1 immunity in MS.

IgG allotypes and subclasses in Norwegian patients with multiple sclerosis

Multiple sclerosis (MS) is a multifactorial disease in which genetic and environmental factors apparently have a major influence on the susceptibility and course of the disease. In the present study we have investigated the genetic basis and subclass levels of IgG in MS. Hundred and thirty-six Norwegian patients with MS and 92 controls were genotyped for IgG allotypes of the GM and KM systems. IgG and IgG subclasses were quantified in sera from 115 MS patients and 20 controls. Neither GM nor KM allo-, haplo- or genotypes were significantly correlated with susceptibility, severity or course of the disease. The G1M (3) (3), G2M (23) (23) and G3M (5) (5) allotypes were significantly correlated with high serum levels of IgG3, whereas high IgG2 levels were correlated with G1M (3) (3) and G2M (23) (23) in both patients and controls. Serum levels of IgG subclasses were not significantly correlated with course or severity of the disease. The results indicate no major role for IgG allotypes or IgG subclass levels in the pathogenesis of MS.

The effect of large-dose prednisone therapy on IgG subclasses in multiple sclerosis

The effect of large-dose prednisone therapy (3960 mg over 56 days) on IgG subclasses in the cerebrospinal fluid and sera, as well as on their intrathecal synthesis, was studied in 15 patients with clinically definite multiple sclerosis. The concentration of IgG subclasses was measured using ELISA with monoclonal antibodies against human IgG subclasses, secondary biotinylated antibody and avidin-biotin-peroxidase complex. There was a decrease of IgG1, IgG3 and IgG4 in the CSF of MS patients after the treatment, but the differences did not reach statistical significance. The IgG index was decreased about 34% (p < 0.01) after the therapy. This was mainly due to diminished synthesis of IgG1 and IgG3. The significance of IgG subclasses in the pathogenesis of MS is discussed.

Diagnostic usefulness of cerebrospinal fluid in multiple sclerosis

Multiple sclerosis (MS) is one of the most common demyelinating diseases of the central nervous system affecting adults between the ages of 20 and 40 years. Clinically, it is characterized by episodes of exacerbations and remissions. Although the cause of MS is unknown, it is generally believed that one or more infectious agents triggers an autoimmune response that causes myelin destruction. There is no known cure for this disease; however, early diagnosis is helpful in the management of patients with MS. The diagnosis of MS is commonly made on the basis of established clinical criteria. No specific laboratory diagnostic test exists, but detection of abnormalities in cerebrospinal fluid (CSF) is a useful aid to support the clinical diagnosis of MS. This review describes the most common CSF abnormalities. These include (a) elevation of immunoglobulin G (IgG), IgG index and IgG synthesis rate; and (b) detection of oligoclonal IgG bands in the CSF by electrophoresis and isoelectric-focusing procedures.

Detection of myelin basic protein-like material in cerebrospinal fluid of multiple sclerosis patients by immunoblot assay

Myelin basic protein (MBP)-like material in 15 cerebrospinal fluid (CSF) samples from patients with multiple sclerosis (MS) was analyzed by isoelectric focusing (IEF) followed by immunoblot assay using rabbit antiserum against human MBP- peptide 69-89, which contains the dominant epitope for MBP-like material. Samples from seven of 10 MS patients with disease in the exacerbation stage showed one band and in three other samples, a number of faint bands also appeared in the alkaline pH region in addition to the one band. CSF from five MS patients whose disease was in remission showed no detectable bands. Our results are consistent with those obtained by quantitative assay, reported in the literature.