Clinically Isolated Syndrome According to McDonald 2010: Intrathecal IgG Synthesis Still Predictive for Conversion to Multiple Sclerosis

CSF lymphocytic pleocytosis does not predict a less favourable long-term prognosis in MS

OBJECTIVE

The role of CSF lymphocytic pleocytosis in predicting the clinical outcome of multiple sclerosis is unclear. We explored the impact of CSF pleocytosis at diagnosis on long-term disease progression in a large UK cohort.

METHODS

We extracted demographic, clinical and CSF data of people with MS attending the MS clinics between 1996 and 2014 at two MS centres from the English Midlands. We compared EDSS at onset, follow up EDSS and progression indices Multiple Sclerosis Severity Score (MSSS), annualized change in EDSS and transition to secondary progression in the presence/absence of pleocytosis. Two-tailed student t-test, Mann-Whitney U test, Chi-Square or Fisher's exact tests were used for detecting the differences.

RESULTS

A total of 247 patients with MS (178 females; mean age 42.4; 217 with relapsing onset) were followed up for an average of 13.56 years (median 12 years). Almost 18% had lymphocytic CSF ≥ 5 per microliter. CSF pleocytosis was not associated with higher EDSS at the time of LP or at follow up, and other progression indices like MSSS, annualized change in EDSS or transition to secondary progression.

DISCUSSION

CSF pleocytosis at MS diagnosis does not predict higher long-term disability and has no long-term prognostic value in routine clinical circumstances. Differences between MS populations and potential differences in disease activity at the time of CSF analysis may account for differences between studies.

Decreased Intrathecal Concentrations of Free Light Chains Kappa in Multiple Sclerosis Patients Taking Very High Effective Disease-Modifying Treatment

Free light chains kappa (FLCκ) in cerebrospinal fluid (CSF) are a part of the intrathecal immune response. This observational study was conducted to investigate the effects of different disease-modifying therapies (DMT) on the humoral intrathecal immune response in the CSF of patients with multiple sclerosis (MS). FLCκ were analyzed in CSF and serum samples from MS patients taking DMT (n = 60) and those in a control cohort of treatment-naïve MS patients (n = 90). DMT was classified as moderately effective (including INFß-1a, INFß-1b, glatiramer acetate, dimethyl fumarate, teriflunomide, triamcinolone); highly effective (including fingolimod, daclizumab) and very highly effective (alemtuzumab, natalizumab, rituximab/ocrelizumab, mitoxantrone). FLCκ were measured using a nephelometric FLCκ kit. Intrathecal FLCκ and IgG concentrations were assessed in relation to the hyperbolic reference range in quotient diagrams. Intrathecal FLCκ concentrations and IgG concentrations were significantly lower in samples from the cohort of MS patients taking very highly effective DMT than in samples from the cohort of MS patients taking highly effective DMT and in the treatment-naïve cohort (FLCκ: p = 0.004, p < 0.0001 respectively/IgG: p = 0.013; p = 0.021). The reduction in FLCκ could contribute to an anti-inflammatory effect in the CNS through this mechanism. There was no difference in the appearance of CSF-specific oligoclonal bands (p = 0.830). Longitudinal analyses are required to confirm these results.

The Influence of Renal Function Impairment on Kappa Free Light Chains in Cerebrospinal Fluid

Background

The determination of kappa free light chains (KFLC) in cerebrospinal fluid (CSF) is an upcoming biomarker for the detection of an intrathecal immunoglobulin synthesis. Since renal function impairment leads to altered serum KFLC and albumin concentrations, interpretation of KFLC in CSF may be influenced by these parameters.

Methods

In this two-center study, the influence of renal function (according to the CKD-EPI creatinine equation) on KFLC and albumin concentrations was investigated in patients with "physiological" (n = 139), "non-inflammatory" (n = 146), and "inflammatory" (n = 172) CSF profiles in respect to the KFLC index and the evaluation in quotient diagrams in reference to the hyperbolic reference range (KFLC IF).

Results

All sample groups displayed declining KFLC indices and KFLC IF values with decreasing renal function (P-values between <.0001 and .0209). In "inflammatory" CSF profile samples, 15% of the patients presented a KFLC index <5.9 while 10% showed an intrathecal KFLC fraction below Q_Kappa(lim), suggesting possible false negative KFLC results.

Conclusions

The influence of renal function should be considered while interpreting KFLC results in patients with neuroinflammatory diseases. The interpretation of KFLC in quotient diagrams is less susceptible to renal function impairment than the KFLC index and should be preferentially used.

Signs of neuroinflammation outweigh neurodegeneration as predictors for early conversion to MS

Background

The pathophysiological mechanisms underlying multiple sclerosis include both inflammatory and degenerative processes. We aimed to study and compare markers of neuroinflammation and neurodegeneration in patients with first presentation of demyelinating disorder and to prospectively identify which of the studied markers serve as predictors for early conversion to multiple sclerosis. Thus, 42 patients with first clinical manifestations suggestive of demyelinating disease were included in a prospective study. Subjects underwent thorough history taking and clinical evaluation. Laboratory studies involved analysis of cerebrospinal fluid (CSF) and serum chitinase 3-like 1 levels. Brain imaging included MRI and ultrasonographic assessment.

Results

T1 black holes, elevated oligoclonal bands (OCB), high baseline T2 lesion load, and enhanced MRI lesions were significantly higher in patients with 1st attack multiple sclerosis. Significantly higher CSF-OCB and serum chitinase 3-like 1 protein was detected in patients with multiple sclerosis (MS) compared to clinically isolated syndrome, and higher levels in MS convertors than non-convertors. Cognitive dysfunction evaluated by MoCA test and brain atrophy assessed using transcranial sonography did not show significant difference among the studied groups. Logistic regression analysis showed that heavy T2 lesion load served as the only predictor of conversion to MS.

Conclusion

Early conversion to MS after first attack of demyelination is related to detection of signs of neuroinflammation rather than neurodegeneration.

The contribution of multifocal visual evoked potentials in patients with optic neuritis and multiple sclerosis: a review

Purpose

To review the evidence on the usefulness of the multifocal visual evoked potential (mfVEP) test in patients with optic neuritis (ON) and/or multiple sclerosis (MS).

Methods

We critically review key published evidence on the use of mfVEP in ON/MS patients and its association with other functional and structural tests.

Results

Multifocal VEP tests are useful in detecting abnormality in patients with ON/MS and monitor the progression of lesions (remyelination, atrophy). In addition, mfVEP has good correlation with conventional visual evoked potential (VEP), standard automated perimetry, optical coherence tomography and magnetic resonance imaging. In patients with ON, mfVEP might be useful in predicting the risk of conversion to MS.

Prognostication and contemporary management of clinically isolated syndrome

Clinically isolated syndrome (CIS) patients present with a single attack of inflammatory demyelination of the central nervous system. Recent advances in multiple sclerosis (MS) diagnostic criteria have expanded the number of CIS patients eligible for a diagnosis of MS at the onset of the disease, shrinking the prevalence of CIS. MS treatment options are rapidly expanding, which is driving the need to recognise MS at its earliest stages. In CIS patients, finding typical MS white matter lesions on the patient's MRI scan remains the most influential prognostic investigation for predicting subsequent diagnosis with MS. Additional imaging, cerebrospinal fluid and serum testing, information from the clinical history and genetic testing also contribute. For those subsequently diagnosed with MS, there is a wide spectrum of long-term clinical outcomes. Detailed assessment at the point of presentation with CIS provides fewer clues to calculate a personalised risk of long-term severe disability.Clinicians should select suitable CIS cases for steroid treatment to speed neurological recovery. Unfortunately, there are still no neuroprotection or remyelination strategies available. The use of MS disease modifying therapy for CIS varies among clinicians and national guidelines, suggesting a lack of robust evidence to guide practice. Clinicians should focus on confirming MS speedily and accurately with appropriate investigations. Diagnosis with CIS provides an opportune moment to promote a healthy lifestyle, in particular smoking cessation. Patients also need to understand the link between CIS and MS. This review provides clinicians an update on the contemporary evidence guiding prognostication and management of CIS.

IgG Index Revisited: Diagnostic Utility and Prognostic Value in Multiple Sclerosis

Objective: Early and accurate diagnosis of multiple sclerosis (MS) remains a clinical challenge. The main objective is to evaluate the diagnostic and prognostic value of the routinely performed immunoglobulin G (IgG) index for MS patients in the Asian population.

Methods: A retrospective study was conducted among a cohort of clinically isolated syndrome (CIS) patients in China with known oligoclonal band (OCB) status and IgG index at baseline. We first evaluated the predictive value of IgG index for OCB status. Secondly, the diagnostic utility and prognostic value of IgG index alone were tested. Lastly, we incorporated IgG index into the 2017 McDonald criteria by replacing OCB with either “IgG index or OCB” (modified criteria 1), “IgG index and OCB” (modified criteria 2), or “IgG index” (modified criteria 3). The diagnostic utility of different criteria was calculated and compared.

Results: In a CIS cohort in China (n = 105), IgG index > 0.7 forecasted OCB positivity (X² = 22.90, P < 0.001). An elevated IgG index was highly prognostic of more clinical relapses [1-year adjusted odds ratio [OR] = 1.32, P = 0.015; 2-years adjusted OR = 1.69, P = 0.013] and Expanded Disability Status Scale worsening (1-year adjusted OR = 1.76, P = 0.040; 2-years adjusted OR = 1.85, P = 0.032). Under the 2017 McDonald criteria (Positive Likelihood Ratio = 1.54, Negative Likelihood Ratio = 0.56), an IgG index > 0.7 in CIS patients increased the likelihood of developing MS within 2 years, either when OCB status was unknown (Positive Likelihood Ratio = 2.11) or with OCB positivity (Positive Likelihood Ratio = 2.11) at baseline; An IgG index ≤ 0.7, along with a negative OCB, helped rule out the MS diagnosis (Negative Likelihood Ratio = 0.53).

Conclusions: IgG index > 0.7 predicts OCB positivity at the initial attack of MS and is prognostic of early disease activity. IgG index serves as an easily-obtainable and accurate OCB surrogate for MS diagnosis in the Asian population.

Conversion of clinically isolated syndrome to multiple sclerosis: a prospective study

BACKGROUND

Multiple sclerosis (MS) begins with an acute clinical attack (clinically isolated syndrome) in approximately 85% of patients. The conversion rate from clinically isolated syndrome to multiple sclerosis has been documented at 30% to 82% in previous studies. When an individual presents for evaluation after a single episode of inflammation of the CNS, several decisions regarding follow-up in subsequent years need to be made, including that of whether or not to start a therapy. There is, therefore, an emerging need to identify the predictive factors that anticipate conversion from CIS to MS.

METHODS

This paper presents a single-center prospective longitudinal study aimed at identification of the most powerful independent predictors for conversion from CIS to MS, utilizing the 2010 McDonald MS criteria and focusing on selected demographic, clinical, radiographical (magnetic resonance imaging - MRI), cerebrospinal fluid (predominantly oligoclonal bands - OCB) and electrophysiological parameters (multimodal sensory and motor-evoked potentials - EP). Two independent outcomes meeting MS criteria are evaluated: development of second clinical relapse (clinically definite multiple sclerosis) and progression in magnetic resonance imaging (based on new MRI T2 brain and/or spinal cord lesions). CIS patients were followed clinically and MRI was repeated at one and two years within the course of a follow-up period of at least 24 months (median 27, range 24-36 months).

RESULTS

Of the 64 CIS patients enrolled who completed at least a 2-year follow-up period (42 women and 22 men, median age 36.5, range 22-66 years), 45 (70.3%) (29 women and 16 men, median age 38; range 22-66 years) fulfilled the 2010 McDonald criteria for MS by dissemination in space (DIS) and time (DIT) over the follow-up period. Twenty-nine CIS patients converted to MS through a clinically symptomatic attack, and 16 CIS patients developed new T2 lesions on MRI, while 19 patients without progression remained stable as CIS. Confirmed among potential predictors for the conversion of CIS patients to MS were increased (>10) baseline MRI T2-hyperintense lesions (odds ratio (OR) 3.107, p = 0.046), OCB positivity (OR 5.958, p = 0.003) and subclinical EP abnormality (OR 14.400, p = 0.003). Multivariate statistical models (logistic regression and Cox proportional hazards regression models) confirmed these parameters as independent predictors of high sensitivity (84%) and acceptable specificity (63%).

CONCLUSION

In addition to accepted predictors for the conversion of CIS to MS (i.e. baseline MRI T2 lesion load and OCB positivity), already implemented in current diagnostic criteria for MS, this study demonstrates, in addition, the high predictive value of subclinical multimodal evoked potential abnormalities.

The Impact of Immunomodulatory Treatment on Kappa Free Light Chains as Biomarker in Neuroinflammation

Background: Kappa free light chains (KFLC) are a promising new biomarker to detect neuroinflammation. Still, the impact of pre-analytical effects on KFLC concentrations was not investigated. Methods: KFLC concentrations were measured in serum and cerebrospinal fluid (CSF) of patients with a newly diagnosed multiple sclerosis (MS) or clinically isolated syndrome (CIS) before (n = 42) or after therapy with high-dose methylprednisolone (n = 65). In prospective experiments, KFLC concentrations were analyzed in the same patients in serum before and after treatment with high-dose methylprednisolone (n = 16), plasma exchange (n = 12), immunoadsorption (n = 10), or intravenous immunoglobulins (n = 10). In addition, the influence of storage time, sample method, and contamination of CSF with blood were investigated. Results: Patients diagnosed with MS/CIS and treated with methylprednisolone showed significantly lower KFLC concentrations in serum as untreated patients. Repeated longitudinal investigations revealed that serum KFLC concentrations continuously decreased after each application of methylprednisolone. In contrast, other immune therapies and further pre-analytical conditions did not influence KFLC concentrations. Conclusion: Our results show prominent effects of steroids on KFLC concentrations. In contrast, various other pre-analytical conditions did not influence KFLC concentrations, indicating the stability of this biomarker.

Reiber's Diagram for Kappa Free Light Chains: The New Standard for Assessing Intrathecal Synthesis?

Oligoclonal bands are the gold standard for determination of an intrathecal immunoglobulin G synthesis and were recently included in the McDonald criteria of 2017 to diagnose relapsing multiple sclerosis (MS) as a substitute for dissemination in time. Intrathecally produced kappa free light chains (KFLC) are a novel promising biomarker with similar characteristics and the advantage for automated determination. However, different approaches exist to determine the intrathecal KFLC fraction. The most common method is to calculate the CSF/serum KFLC quotient with reference to the albumin CSF/serum quotient (QKappa/QAlb) the so-called KFLC index. Recently, Reiber developed a theoretically and empirically founded hyperbolic function similar to his traditional hyperbolic function for the immunoglobulins A, G, M. Our study included a total of 168 patients with either MS according to the McDonald criteria of 2017, clinically isolated syndrome (CIS) with conversion to MS during follow-up, or stable CIS. Positive oligoclonal bands were compared with the KFLC index, Reiber's KFLC diagram, Presslauer's KFLC exponential curve, and Senel's linear curve for KFLC. Reiber's diagram detected an intrathecal production of KFLC in 98/100 patients with MS, only one patient fewer than oligoclonal bands positivity (99/100). By using the KFLC index ≥ 5.9, Presslauer's KFLC exponential function, and Senel's linear curve two more patients would not have been identified (96/100). For the group of patients who converted from CIS to MS similar results were obtained for both the oligoclonal bands and the Reiber graph (21/24, 88%). The KFLC index ≥ 5.9, Presslauer's method, and Senel's linear function each identified two patients fewer (19/24, 79%). In patients with stable CIS, 11/44 patients (25%) displayed oligoclonal bands in contrast to 9/44 patients (20%) with elevated KFLC by using Reiber's diagram and Presslauer's method, 8/44 patients (18%) with elevated KFLC as detected by Senel's linear function, and 7/44 patients (16%) with KFLC index ≥ 5.9. In conclusion, Reiber's KFLC diagram shows a great diagnostic performance to detect an intrathecal KFLC production in patients with MS.

Investigation of Oligoclonal IgG Bands in Tear Fluid of Multiple Sclerosis Patients

Background: Oligoclonal IgG bands (OCB) in the cerebrospinal fluid (CSF) represent a typical marker for inflammation in multiple sclerosis (MS) patients and have a predictive and diagnostic value in patients with a first suspected demyelinating event. The detection in tears remains controversial but some reports suggested a replacement of CSF analysis by OCB detection in tears. We aimed to investigate the value of OCB detection in tears systematically in patients with MS.

Methods: Tears of 59 patients with suspected or diagnosed MS were collected with Schirmer filter paper strips. Tear IgG was purified by affinity chromatography with protein G. After isoelectric focusing in polyacrylamide gels OCB detection was performed with direct silver staining. Paired triplets of CSF, serum, and tears were analyzed. For comparison purposes we additionally used other tear collection methods (flush procedure and plastic capillary tubes) or detection techniques (Immunoblotting). Clinical and paraclinical parameters are provided.

Results: IgG collection in tears was most reliable by using Schirmer strips. Thirteen patients had to be excluded due to insufficient sample material. Tear specific proteins that interfered with OCB detection were successfully eliminated by IgG purification. The concordance of OCB in tears and CSF of all investigated MS patients was 39% with a high rate of only marginal pattern in tears. Five patients demonstrated restricted bands in tears, neither detectable in CSF nor serum. Occurrence of OCB in tears was significantly associated with pathological visual evoked potentials (P = 0.0094) and a history of optic neuritis (P = 0.0258).

Conclusion: Due to the limited concordance, high rate of samples with insufficient material, and the unknown origin of tear IgG we cannot recommend that tear OCB detection may replace CSF OCB detection in MS patients. The detection of unique OCB in tears might offer new insights in ophthalmological diseases.

Conversion of clinically isolated syndrome to multiple sclerosis: a prospective multi-center study in Eastern India

BACKGROUND

In White populations more than 60% of clinically isolated syndrome (CIS) convert to multiple sclerosis (MS) on a long-term follow-up; several predictors for conversion have been identified.

OBJECTIVE

This study aimed to determine the conversion rate and the predictors of conversion from CIS to MS (McDonald 2010) among Indians. The other objective was to evaluate the diagnostic accuracy of the new McDonald 2017 criteria in prediction of a second clinical attack.

METHODS

Clinical and demographic data of CIS cohorts were collected. Baseline investigations included cerebrospinal magnetic resonance imaging (MRI) with contrast and cerebrospinal fluid (CSF) testing for oligoclonal band (OCB). Follow-up clinical and MRI examinations were performed annually for at least 24 months.

RESULTS

Of the 82 subjects (age range 15-58 years), 36 (43.9%) converted to MS; 31/82 (37.8%) converted in 24 months. The predictors for conversion were earlier age of onset, CSF-OCB, cerebral MRI T2 lesion count, and periventricular and juxtacortical location of lesions. Twenty-two (26.83%) CIS fulfilled the McDonald MS 2017 criteria at baseline.

CONCLUSION

In this first prospective study of CIS in India, the risk factors for conversion are similar but the conversion rate to MS is lower than that in the western nations.

Impact of the McDonald Criteria 2017 on Early Diagnosis of Relapsing-Remitting Multiple Sclerosis

Multiple sclerosis is a chronic immune mediated demyelinating disease leading to neurological disabilities that need to be diagnosed and treated early. Guidelines on multiple sclerosis diagnosis and monitoring experienced comprehensive changes over the last decades. The first McDonald criteria published in 2001 emphasized the importance of MR imaging but also recognized the role of cerebrospinal fluid diagnostics. The demonstration of an intrathecal immunoglobulin G synthesis is a well-established additional component and has a long tradition in the diagnosis of relapsing-remitting multiple sclerosis. However, the role of cerebrospinal fluid for diagnostic purposes was rather diminished in each revision of the McDonald criteria. In the latest revision of the McDonald criteria of 2017, the detection of an intrathecal immunoglobulin G synthesis as oligoclonal bands experienced a revival. Patients with the first clinical event suggesting multiple sclerosis who fulfill the criteria for dissemination in space can be diagnosed with relapsing-remitting multiple sclerosis when oligoclonal bands in cerebrospinal fluid are detected. The diagnostic sensitivity of these novel criteria with a focus on dissemination in time and oligoclonal bands as a substitute for dissemination in time was published in different cohorts in the last year and is of special interest in this review. Recently published data show that by applying the 2017 McDonald criteria, multiple sclerosis can be diagnosed more frequently at the time of first clinical event as compared to the 2010 McDonald criteria. The main effect was due to the implementation of oligoclonal bands as a substitute for dissemination in time. However, careful differential diagnosis is essential in patients with atypical clinical manifestations to avoid misdiagnoses.

Cost-effectiveness of interferon therapy for multiple sclerosis in Peru: impact of treatment adherence

Objective

To analyse the cost-effectiveness (C-E) of interferon therapy for MS and the impact of adherence associated with a patient support programme (PSP).

Methods

Markov model was structured based on systematic review of the evidence and the opinion of local experts. The model has three health states: (1) Baseline treatment (BT), (2) Interferon-β (IFN) with patient support programme (PSP) and (3) IFN without PSP. Annual cycles were considered, with a time horizon of 30 years. The analysis perspective was based on the Ministry of Health (MoH).

Key findings

Interferon-β + PSP dominates the treatment of IFN without PSP. The incremental C-E rate (ICER) for IFN + PSP was estimated at S/. 26 408 per Quality Adjusted Life Year (QALY) in relation to BT. IFN without PSP was dominated by the IFN + PSP treatment. The cost per QALY of IFN + PSP was below the payment threshold in almost 100% of the model simulations. The acceptability curves show that the treatment with PSP + IFN is probabilistically more cost effective from a payment threshold of 1.25 annual Gross Domestic Product per capita (GDP-pc). The Tornado analysis for the ICER between IFN + PSP and BT shows that the most sensitive variables of the model are the relative risk (RR) for treatment adherence and the cost of IFN + PSP treatment.

Conclusion

The addition of a PSP had a significant effect on adherence and C-E of the intervention. The ICER for IFN + PSP was below 1.5 annual GDP-pc of payment threshold with an incremental cost near to 3 GDP-pc. IFN without PSP was dominated by the IFN + PSP.

The Persisting Significance of Oligoclonal Bands in the Dawning Era of Kappa Free Light Chains for the Diagnosis of Multiple Sclerosis

The latest revision of the McDonald criteria of 2017 considers the evidence of an intrathecal immunoglobulin (IgG) synthesis as a diagnostic criterion for dissemination in time in multiple sclerosis. While the detection of oligoclonal bands is considered as the gold standard, determination of kappa free light chains might be a promising tool as a less technically demanding and cost saving method. However, data on the direct comparison between kappa free light chains and oligoclonal bands are limited and no study to date has used the highly sensitive method of polyacrylamide gels with consecutive silver staining for the demonstration of oligoclonal bands. Furthermore, the impact of the revised McDonald criteria of 2017 on the role of kappa free light chains as a biomarker has not been investigated. Nephelometry was used to determine kappa free light chains in cerebrospinal fluid (CSF) and serum from 149 patients with their first demyelinating event between 2010 and 2015. Clinical data, kappa free light chains, and oligoclonal band status were compared at the time of initial diagnosis and after follow-up to identify converters from clinically isolated syndrome to multiple sclerosis. An elevated kappa free light chain index (>5.9) was found in 79/83 patients (95%) with multiple sclerosis diagnosed at baseline, slightly less frequent than oligoclonal bands (98.8%). 18/25 (72%) patients who converted from clinically isolated syndrome to multiple sclerosis showed an elevated kappa free light chain index compared to 20/25 (80%) patients with positive oligoclonal bands. In patients with stable clinically isolated syndrome 7/41 (17%) displayed an elevated kappa free light chain index against 11/41 (27%) oligoclonal band positive patients. Only two patients with stable clinically isolated syndrome showed an elevated kappa free light chain index but were oligoclonal bands negative. In conclusion, determination of the kappa free light chain index is a promising diagnostic approach to assess intrathecal immunoglobulin synthesis in multiple sclerosis. Nevertheless, oligoclonal bands are highly prevalent in multiple sclerosis and can detect an intrathecal synthesis of IgG even when the kappa free light chain index is below the threshold. We consider sequential use of both methods as reasonable.

Higher Serum Immunoglobulin G3 Levels May Predict the Development of Multiple Sclerosis in Individuals With Clinically Isolated Syndrome

Clinically isolated syndrome (CIS) is a first episode of neurological symptoms that may precede a diagnosis of multiple sclerosis (MS). Therefore, studying individuals with CIS may lead to breakthroughs in understanding the development and pathogenesis of MS. In this study, serum levels of immunoglobulin (Ig)G, IgA, IgM, and IgG1–4 were measured in 20 people with CIS and compared with those in 10 healthy controls (HC) and 8 people with MS. Serum Ig levels in individuals with CIS were compared with (a) the time to their conversion from CIS to MS, (b) serum levels of antibodies to Epstein–Barr virus, (c) frequencies of T regulatory (Treg), T follicular regulatory (Tfr), and B cell subsets, and (d) Treg/Tfr expression of Helios. Serum IgG, IgM, and IgG2 levels were significantly lower in people with CIS than HC, and IgG, IgM, and IgG1 levels were significantly lower in people with CIS than MS. After adjusting for age, sex, and serum 25(OH) vitamin D₃ [25(OH)D] levels, CIS was associated with lower serum levels of IgG and IgG2 compared with HC (p = 0.001 and p < 0.001, respectively). People with MS had lower IgG2 levels (p < 0.001) and IgG2 proportions (%IgG; p = 0.007) compared with HC. After adjusting for age, sex, and 25(OH)D, these outcomes remained, in addition to lower serum IgA levels (p = 0.01) and increased IgG3 levels (p = 0.053) in people with MS compared with HC. Furthermore, serum from people with MS had increased proportions of IgG1 and IgG3 (p = 0.03 and p = 0.02, respectively), decreased proportions of IgG2 (p = 0.007), and greater ratios of “upstream” to “downstream” IgG subclasses (p = 0.001) compared with HC. Serum IgG3 proportions (%IgG) from people with CIS correlated with the frequency of plasmablasts in peripheral blood (p = 0.02). Expression of Helios by Treg and Tfr cell subsets from individuals with CIS correlated with levels of serum IgG2 and IgG4. IgG3 levels and proportions of IgG3 (%IgG) in serum at CIS diagnosis were inversely correlated with the time until conversion to MS (p = 0.018 and p < 0.001, respectively), suggesting they may be useful prognostic markers of individuals with CIS who rapidly convert to MS.