Autoimmune autonomic ganglionopathy (AAG) is a disorder of the autonomic nervous system associated with autoantibodies against the α3 subunit of the ganglionic acetylcholine receptor (gnACHR). gnACHR antibodies exert their effects via receptor internalisation, but most current gnACHR diagnostic assays only detect antibody binding. Hence, we developed a new bioluminescent cell-based assay (BLIA) to measure internalising gnACHR antibodies. The BLIA was performed by incubating patient sera with live IMR-32 cells that express surface gnACHR. Remaining surface gnACHR was quantified using a novel split luciferase system with NanoBiT conjugated detecting antibodies. The percentage of receptor internalisation was calculated with comparison to cells incubated with reference sera, with > 20

The relapse risk following discontinuation of immunomodulatory treatment in myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) is unknown. Evidence suggests that 'at least' 3 months of oral corticosteroids reduces relapse risk after a single attack, and that it may be possible to stop maintenance treatment in relapsing stable disease, but the optimal duration of treatment has yet to be defined. We therefore investigated relapse outcomes following discontinuation of maintenance treatment. We conducted a cohort study of MOGAD patients seen in the Oxford Neuromyelitis Optica Highly Specialised Service between January 2010 and May 2025. Patients with MOGAD who had at least 12 months of follow-up and who commenced and then discontinued maintenance treatment were included. Associations of factors including treatment duration before discontinuation, disease course at discontinuation (after a single attack/monophasic or relapsing course) and MOG IgG1 status on live cell-based assay were investigated. The primary outcome was time-to-relapse following treatment discontinuation. Cox regression was used. We included 190 MOGAD patients with 236 discontinued treatment intervals. There were 150 (63.6%) discontinuations after a single attack and before a first relapse in patients with monophasic disease, and 86 (36.4%) discontinuations in patients with relapsing disease. Most patients used corticosteroids alone [84.7% of immunomodulatory treatment (IT) intervals], and non-steroid ITs were used in 15.2% of IT intervals, either alone or in combination with steroids. Post-discontinuation relapse occurred after 92 (39.0%) discontinuations, at a median time of 5.4 (interquartile range 1.4-20.1) months after treatment cessation. Those who relapsed were more likely to have a relapsing course at the time of discontinuation (50% versus 27.8%, P = 0.001) and a positive/low-positive pre-discontinuation MOG IgG1 result (89.8% versus 71.5%, P = 0.005). In a multivariable analysis, a relapsing course at the time of discontinuation was associated with an elevated relapse risk (hazard ratio 1.95, 95% confidence interval 1.25-3.06, P = 0.003). Overall, prolonged treatment beyond 3 months before discontinuation significantly reduced relapse risk. Optimal treatment durations were estimated to be 10-18 months for patients treated after their first attack and 20-30 months for relapsing patients, after which treatment discontinuation could be considered in patients who were relapse-free on treatment. Identifying the relapse risk when discontinuing maintenance immunomodulatory treatment in MOGAD should aid management decisions in patients presenting with their first attack and also in those on longer-term treatment for relapsing disease. Our findings, from a cohort predominantly treated with steroids, provide evidence to inform joint decision-making for stable patients who are considering treatment cessation.

Introduction: Neurodegenerative dementia syndromes are severely debilitating, progressive and increasing in incidence with an ageing population. A treatable differential diagnosis to neurodegenerative dementia is autoimmune encephalitis (AE), but AE patients are often misdiagnosed, delaying treatment. Previous work in the Netherlands has shown that 0.8% of patients with suspected neurodegenerative dementia suffer from AE. In Sweden, there is considerable variability in the prevalence of AE, possibly indicating under-diagnosis. We hypothesized that some Swedish individuals seeking care for memory impairment might suffer from an undetected AE and that these would show aberrances in available markers of neuroinflammation. Methods: We retrospectively screened frozen sera from 1041 individuals seen between 2019 and 2023 at the Karolinska University hospital memory clinics in Stockholm for autoantibodies to contactin-associated protein-like 2 (CASPR2), leucine-rich glioma-inactivated 1 (LGI1), gamma-aminobutyric acid receptor B (GABABR), the n-methyl-d-aspartate receptor (NMDA-R) and Immunoglobulin superfamily containing LAMP, OBCAM, and Neurotrimin family member 5 (IgLON5) using live cell-based assays (CBAs) and scored them by microscopy. Serum and CSF from suspected positive patient samples were re-tested and titrated by live CBA, commercial fixed CBAs and tissue based assays. Results: 8 of the 1021 individuals, or 0.8% of the cohort, tested positive in at least three different tests for antibodies to CASPR2 (n=3), GABABR (n=2), LGI1 (n=1) and NMDAR (n=2). Seven of these patients had not been previously diagnosed with AE. Apart from two CASPR2-antibody positive patients showing neuropathic pain and seizures and neuromyotonia, respectively, the patients lacked clinical signs of encephalitis aside from memory impairment and affect lability. The antibody-positive patients did not differ significantly from autoantibody-negative patients in any available clinical parameter. None showed signs of inflammation on brain magnetic resonance tomography, and 2/7 lacked any sign of neuroinflammation in the CSF with available tests, which is commonly seen in later-onset AE. Conclusion: Our work identifies undiagnosed AE patients with subtle symptomatology among Swedish memory clinic visitors, that cannot be sensitively separated from antibody-negative patients with current diagnostic tests. Our results suggest the need for the introduction of more sensitive markers of neuroinflammation to the memory clinic to identify and treat individuals with AE among sufferers of memory impairment. ### Competing Interest Statement JT has received a total of 5 speakers honoraria from Lundbeck, SVAR diagnostics and MSD 2022-2025. He has not received any research grants, restricted, or unrestricted, for this or any other work. No other coauthors have declared any conflicts of interest. ### Clinical Protocols ### Funding Statement The authors acknowledge the generous financial assistance by the Wenner-Gren foundation grants FT2021-0005 and WUP2022-003. Studies were also supported by Alzheimerfonden grant AF-981112 and Bjoerklunds fond, grant SLS-974288. NB was funded by King Gustav V:s and Queen Victorias 610 Foundation 2024-2026, and ALF-Projects Region Stockholm 2023-2025. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The overall cohort study was accepted in 2011 by the Swedish Ethical Review Authority, Stockholm branch, registration number 2011/1987-31. Using the samples and the patient data for this specific study was accepted in 2022 by the Swedish Ethical Review Authority, Lund branch (projects now allotted to other geographical regions to ensure impartiality), registration number 2022/03556-01. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes After the peer-reviewed publication of the manuscript, .nd2 microscopy image files for each sample and antigen will be available for download at Researchdata.se. This database will include information about which samples that have been considered positive in the first screen as well as which samples that were confirmed by other methods, singling out the eight positive cases as "confirmed positive". However, to avoid exposing personal data and enabling full open access to this dataset, it will be fully anonymised and no further information will be available per sample.

BACKGROUND:Little is known about the causes of serum aquaporin 4 (AQP4) antibody-positive neuromyelitis optica spectrum disorder (AQP4-positive NMOSD) or how its pathophysiology differs from other demyelinating autoimmune diseases, which limits therapeutic and preventative opportunities despite available diagnostic biomarkers. By performing a pan-ancestry genome-wide association study (GWAS), we aimed to deepen our understanding of the genetic architecture of AQP4-positive NMOSD and to explore shared heritability with other autoimmune diseases. METHODS:We performed a pan-ancestry GWAS in 2833 individuals, including 1573 AQP4-positive NMOSD cases and 1260 controls (comprising non-affected relatives, healthy non-relatives, and those with other autoimmune diseases). Samples were collected from the International NMOSD Genetics Consortium, comprising 36 hospitals and research facilities across the world. All individuals with AQP4-positive NMOSD fulfilled the 2015 international consensus diagnostic criteria for NMOSD, including positive AQP4-IgG status. We also performed a second GWAS with only the 1857 samples of European ancestry (803 cases and 1054 controls). We then compared our GWAS findings to those from other autoimmune diseases. FINDINGS:We found three independent associations with AQP4-positive NMOSD that reached genome-wide significance: two within the MHC and a third within an intron of the STAT4 gene. In the pan-ancestry study, we identified a complement C4A-associatied variant, rs1150753 (chr6:32092090:A>G, p=1·61 × 10-29, odds ratio [OR] 2·95, 95% CI 2·44-3·56), rs607929 (chr6:32619221:C>G, p=2·87 × 10-24, OR 1·93, 95% CI 1·70-2·20), and a STAT4-associated variant, rs35593987 (chr2:191051800:AC>A, p=8·49 × 10-14, OR 1·75, 95% CI 1·51-2·03). In Europeans, we identified variants that were either in linkage disequilibrium with or the same as those from the pan-ancestry study: rs1270942 (chr6:31951083:A>G, p=2·52 × 10-28, OR 3·01, 95% CI 2·47-3·66), rs607929 (p=1·12 × 10-20, OR 1·99, 95% CI 1·72-2·30), and rs3821236 (chr2:191038032:G>A, p=1·20 × 10-10, OR 1·74, 95% CI 1·47-2·06). rs1270942 is in linkage disequilibrium with rs1150753 (r2=0·96) as well as two AQP4-positive NMOSD-associated HLA alleles, HLA-DRB1*03:01 (p=2·80 × 10-26, OR 2·79, 95% CI 2·30-3·37) and HLA-B*08:01 (p=1·02 × 10-24, OR 2·68, 95% CI 2·22-3·24). A priori testing of the P1104A variant (rs34536443, chr19:10352442:G>C) within the TYK2 gene, which acts upstream in the STAT4 pathway, found it to be protective (p=0·0008, OR 0·52, 95% CI 0·35-0·76 in the pan-ancestry study). Genetic sharing was observed with several comorbid autoimmune diseases for both the complement C4A-associated and STAT4-associated variants, including Sjögren's syndrome and systemic lupus erythematosus. INTERPRETATION:AQP4-positive NMOSD is more genetically similar to systemic autoimmune diseases than to multiple sclerosis, despite sharing overlapping clinical phenotypes. Specifically, a polymorphism associated with reduced complement C4 was identified as the biggest disease genetic risk factor, which has been shown to facilitate the development of autoantibody-producing B cells. Our findings also support a pathogenic role of HLA-restricted CD4+ T cells, owing to both a genome-wide significant association of HLA-DRB1*03:01 as well as heritable risk within the TYK2-STAT4 signalling pathway. Having already been shown to be a successful target for treating psoriatic arthritis and, potentially, systemic lupus erythematosus, we propose the TYK2-STAT4 pathway as a possible therapeutic target in AQP4-positive NMOSD. FUNDING:The OAK Foundation, The Guthy Jackson Charitable Trust Foundation, and the UK Medical Research Council.

BACKGROUND:Myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) is a rare antibody-mediated inflammatory demyelinating disorder. In 2023, new international consensus diagnostic criteria were agreed. This study uses these criteria to describe epidemiological features of MOGAD in a population-based cohort of patients from south Wales, UK. METHODS:Retrospective review of case notes on all positive MOG-IgG results in South Wales between 01 January 2011 and 30 June 2024 was undertaken, 2023 diagnostic criteria applied and standardised clinical features recorded. Paediatric MOGAD was defined as age at onset < 16 years and adult MOGAD ≥ 16 years. The incidence period was between 01 January 2015 and 31 December 2023. RESULTS:Seventy-six prevalent cases were identified: 53 adults and 23 children. Minimum estimated prevalence of MOGAD in south Wales on 30 June 2024 was 76/1,974,110 population (3.85/100,000 population; 95% CI 3.03-4.82). Paediatric prevalence was 6.59/100,000 population (95% CI 4.18-9.89) and adult prevalence 3.26/100,000 population (95% CI 2.44-4.27). Sex ratio was almost equal in males and females. The most frequent presentations were optic neuritis in adults (62.3%) and ADEM in children (34.8%); 64.5% had a monophasic disease course over a median follow-up of 38 months (IQR 13-63). Mean annual incidence was 3.39 (95% CI 2.58-4.39) per million population. CONCLUSIONS:This regional study provides updated prevalence and incidence rates for MOGAD since the introduction of 2023 diagnostic criteria in a stable south Wales, UK population.

OBJECTIVE:To evaluate the diagnostic accuracy of glial fibrillary acidic protein (GFAP) measured in dried plasma spots versus conventional plasma- and serum-GFAP testing for assessment of disease severity in aquaporin-4 immunoglobulin G-positive neuromyelitis optica spectrum disorder (AQP4-IgG+ NMOSD). METHODS:A neuroimmunological prospective cohort of remission samples from 70 participants with the diagnoses AQP4-IgG+ NMOSD (n = 19), myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD; n = 9), relapsing-remitting multiple sclerosis (RRMS; n = 28) and healthy controls (HC; n = 14) from a single center were included. GFAP concentrations were measured in frozen and thawed plasma and paired dried plasma spot (DPS) samples using an ultrasensitive proximity ligation-based assay (nucleic acid-linked immuno-sandwich assay; NULISA). In NMOSD, GFAP was additionally quantified in paired serum samples using a single-molecule array (Simoa) assay as a reference. Cross-matrix correlations, diagnostic performance, and associations with neurological disability were evaluated. RESULTS:GFAP concentrations measured by NULISA correlated strongly between plasma and DPS samples across diagnostic groups and healthy controls. In NMOSD, plasma GFAP measured by NULISA showed strong concordance with serum GFAP quantified by Simoa. DPS-derived and plasma-derived GFAP demonstrated good diagnostic accuracy for AQP4-IgG+ NMOSD and was significantly associated with neurological disability as measured by the Expanded Disability Status Scale (EDSS). Group-wise comparisons across plasma and DPS showed retained elevation of GFAP in AQP4-IgG+ NMOSD compared with the other diagnostic groups and healthy controls. INTERPRETATION:GFAP quantification using the NULISA platform is feasible in plasma and DPS samples and enables reliable biomarker assessment in a potentially remote-compatible setting. DPS-derived GFAP measurements retained meaningful information on disability in NMOSD and may provide an analytical framework for future studies evaluating minimally invasive capillary or self-sampling approaches.

Objective To determine whether myelin-sensitive quantitative MRI reveals microstructural abnormalities in normal-appearing cortex (NACtx) in myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD), indicating that conventional MRI underestimates remission residual cortical injury.Methods Forty-two patients with MOGAD in remission and 42 age- and sex-matched healthy controls (HCs) underwent cognitive testing (Rao Brief Repeatable Battery), disability rating (Expanded Disability Status Scale) and 3-T MRI, including three-dimensional T1-weighted, T2-weighted and double-inversion-recovery sequences to identify cortical lesions and delineate NACtx. T1- to T2-weighted ratio z-scores (T1/T2r), magnetisation transfer ratio (MTR) and magnetisation transfer saturation (MTsat) were derived in global and lobar NACtx; MT imaging was available in 22 patients and 24 controls. Linear mixed-effects models compared MOGAD with HCs and cortical (history of at least one acute cortical attack) with non-cortical phenotypes, adjusting for age, sex, site and cortical thickness with false-discovery-rate correction.Results Sixteen of 42 MOGAD patients had a cortical phenotype; cortical lesions at remission were present in 4 of 42 (9.5%), all with a cortical phenotype. MTsat metric, but not T1/T2r or MTR, detected NACtx alterations in the MOGAD cohort compared with HCs. Cortical MOGAD phenotype showed reduced MTsat in global, frontal, temporal, limbic, hippocampal and insular NACtx regions vs. HCs, whereas non-cortical MOGAD was similar to HCs. Exploratory analyses suggested lower MTsat in temporal, limbic, hippocampal and insular NACtx regions in cortical MOGAD with cognitive impairment than in cognitively preserved MOGAD.Interpretation Myelin-sensitive MTsat reveals persistent, regionally specific abnormalities in normal-appearing cortex in cortical MOGAD and is a promising marker of residual cortical damage linked to cognitive dysfunction.

ABSTRACT Background Myasthenia gravis (MG) is categorized into several subgroups, including seronegative MG. Seronegative human patients are well documented, but seronegative dogs remain clinically uncharacterized and their prevalence unknown. Objectives This study aims to evaluate the clinical presentation, diagnosis, treatment, and outcome of canine MG subgroups. Animals One hundred sixty‐seven owner‐owned dogs diagnosed with MG from three referral centers. Methods Retrospective case series. We classified myasthenic dogs into subgroups, adhering to human guidelines. Results We classified 167 dogs into four subgroups: acetylcholine receptor (AChR) antibody‐positive generalized (49.7%, n = 83/167), focal (19.2%, n = 32/167) and thymoma‐associated MG (9%, n = 15/167) and seronegative MG (22.2%, n = 37/167). Dogs with thymoma‐associated MG were older (median 102 months; Interquartile Range (IQR) 96–120; p < 0.001) and seronegative dogs were younger (median 30 months; IQR 11.5–66; p = 0.017), compared to the generalized subgroup (median 67 months; IQR 36–96). Seronegative dogs presented less frequently with megaesophagus, compared to the generalized subgroup (63.8% vs. 85.7%; Odds Ratio 3.4; 95% confidence intervals (C.I.) 1.4–8.9; p = 0.025). Myasthenic dogs' survival time was significantly reduced when thymoma (Hazard Ratio (H.R.) 3.7; 95% C.I. 1.4–9.9; p = 0.028) or esophageal weakness (H.R. 3.8; 95% C.I. 2.0–7.0; p < 0.001) was present. Conversely, a higher likelihood of remission was achieved when esophageal weakness was absent (H.R. 3.8; 95% C.I. 1.4–10.0; p = 0.007). Conclusion and Clinical Importance Dogs with seronegative MG are more common than previously reported. Myasthenic subgroups differ in presentation and outcome, with esophageal weakness key to survival and remission. Diagnostic tests for seronegative dogs and effective treatments for esophageal weakness in myasthenic dogs are urgently needed.

Background:Early detection of autoimmune psychosis (AP) mediated by antineuronal antibodies (Abs) is critical for achieving optimal clinical outcomes. However, evidence remains limited regarding who should be tested and how Ab-positive cases should be managed. In this large-scale study, we evaluated proposed clinical criteria for targeted Ab testing in psychiatric services and described the clinical course of seropositive patients. Methods:Individuals with early psychosis (EP) or persistent psychosis (PP) were prospectively assessed with clinical criteria to determine high- or low-risk status for AP. Blood samples were collected for Ab testing using a fixed cell-based assay. Seropositive individuals were invited for detailed review, including clinical, functional, and cognitive assessments at baseline and a 12-month follow-up. Blood samples were collected from 754 individuals (EP: n = 352, PP: n = 402). Results:Abs were present in 2.3% (17/754), including 3.4% (12/352) of patients with EP and 1.2% (5/402) of patients with PP. AP was confirmed in 2 cerebrospinal fluid (CSF)-positive high-risk individuals (total: 2/754, 0.3%; EP: 1/352, 0.3%; PP: 1/402, 0.2%). Both improved with immunotherapy. Although some low-risk patients were seropositive, none were diagnosed clinically with AP. Conclusions:AP prevalence was low in this cohort. Targeted testing informed by clinical high-risk criteria successfully identified 2 immunotherapy-responsive AP cases. This approach appears feasible but requires further validation. People with psychosis and high-risk AP features should be considered for Ab testing in sera and CSF where indicated. Further research is required to embed targeted Ab testing into mental health services.

NMDAR-antibody encephalitis can arise as a post-infectious 'relapse' following HSV encephalitis. We asked whether a similar condition might occur after Japanese Encephalitis (JE). Cell-based assays for antigen-specific antibodies and IgG binding to the surface of live hippocampal neurons were performed on 13 CSFs and 65 sera, many sampled longitudinally, from 34 Vietnamese children with JE. Three month outcomes were scored according to a pediatric post-encephalitis scale; clinical features focussed on new onset symptoms during the follow-up, blinded to antibody results. Ten/34 children (29 %) had serum antibodies against known neuronal-surface antigens, 4 NMDAR, 4 CASPR2, 1 GABAAR and 1 LGI1, detected from day 23 after onset. In addition, 8/10 (80 %) of these children and 13/24 (54 %) others had antibodies that bound in a distinctive pattern to live hippocampal neurons (HN-Abs), four detected on days 9-12. A relapse was only considered possible in 5 patients, two with specific neuronal surface antibodies (NSAbs). Neither specific NSAbs (p = 1.00) nor HN-Abs (p = 1.00).were more common in patients with possible relapse than in those with unlikely relapse. There was a modest trend towards worse outcome scores in patients with known NSAbs than in the remaining patients (p = 0.089). Antibodies to neuronal surface proteins, known and unknown, are common in children after JE. Caution is urged in defining post-infectious autoimmune encephalitis on the basis of a positive neuronal antibody and new onset symptoms or deterioration following recovery from JE, or in initiating immunotherapy without confirmatory evidence of a time-dependent encephalitic illness defined by published guidelines.

The last 10 years has brought transformative developments in the effective treatment of myasthenia gravis (MG). Beginning with the randomized trial of thymectomy in myasthenia gravis that demonstrated efficacy of thymectomy in nonthymomatous MG, several new treatment approaches have completed successful clinical trials and regulatory launch. These modalities, including B cell depletion, complement inhibition, and blockade of the neonatal Fc receptor, are now in use, offering prospects of sustained remission and neuromuscular protection in what is a long-term disease. In this review, we update our clinico-immunological review of 2016 with these important advances, examine their role in treatment algorithms, and focus attention on key issues of biomarkers for prognostication and the growing cohort of older patients, both those with long-term disease, and late-onset MG (‘LOMG’). We close by expressing our four hopes for the next 5–10 years: improvements in laboratory medicine to facilitate rapid diagnosis, effective strategies for neuromuscular protection, more research into and better understanding of pathophysiology and treatment response in older individuals, and the potentially transformative role of therapies aimed at delivering a durable response such as chimeric antigen receptor (CAR) T cells. Our postscript summarizes some emerging themes in the field of serological and online biomarkers, which may develop greater stature in the next epoch.

ABSTRACT Background and Aims Reliable detection of antibodies against nodal targets is vital for the diagnosis of autoimmune nodopathies. The performance characteristics of recently developed in‐house assays are unknown. We compared testing at four centres. Methods Each submitted 29–40 serum samples to a coordinating centre from one of three groups: (1) autoimmune nodopathy patients, with positive nodal/paranodal antibodies; (2) seronegative patients with other inflammatory neuropathies, and (3) healthy individuals or those with other neurological diseases. The coordinating centre recoded all samples and returned 160 identical aliquots to each testing centre for blinded testing. Once data from all centres had been received by the coordinating centre, unblinded results were returned for analysis. Sensitivity was defined by the proportion of group 1 samples returned as positive. Accuracy was defined as 0.075(sensitivity) + 0.925(specificity). Results Centres performed various combinations of ELISA, cell‐based (CBAs) and teased‐nerve fibre assays. All labs produced highly accurate results (96%–100%) and concordance for the overall result across at least 3 or all 4 test centres was observed for 98% and 89% of the samples respectively. However, 10/30 individual assays (6/14 CBAs and 4/16 ELISAs) were less than 90% sensitive. Only 3 assays had more than 1 false positive result (2 ELISAs and 1 CBA). Combining different assay modalities to produce an overall result did not improve accuracy. Inter‐laboratory consistency in the determination of antibody subclasses was poor. Interpretation Although most samples were correctly categorised in all 4 centres, the use of a specific test modality or multiple tests did not guarantee accuracy. Early and repeated interlaboratory testing with sharing of samples is important to understand test performance and reproducibility, identify areas for improvement and maintain consistency. To aid this, we provide detailed methods for the best performing tests. Further standardisation of antibody subclass determination is required.

Detection of antibodies against aquaporin-4 (AQP4-IgG) and myelin oligodendrocyte glycoprotein (MOG-IgG) is essential for diagnosis of AQP4-IgG+ neuromyelitis optica spectrum disorder and myelin oligodendrocyte glycoprotein antibody-associated disease. Uncertainties persist regarding the clinical significance of serum antibody titres to predict relapses. We aimed to analyse the trend of serum AQP4-IgG and myelin oligodendrocyte glycoprotein antibody-IgG titres during relapses and periods of clinical stability. In this retrospective study we analysed serum AQP4-IgG and myelin oligodendrocyte glycoprotein antibody -IgG titres from live cell-based assays from the Oxford Autoimmune Neurology Diagnostic Laboratory for the UK specialist NMO Service between February 2010 and June 2024. We recruited seropositive AQP4-neuromyelitis optica spectrum disorder and myelin oligodendrocyte glycoprotein antibody-associated disease patients with serum samples available within 30 days of an attack ('attack') and at least one another sample for comparison within 1 year ('pre-attack' and 'post-attack'). Up to 3 further serum samples were selected within 2, 3 or 4 years after the attack. 117 attacks in 92 AQP4-IgG+ patients (81.5% female) and 127 attacks in 111 myelin oligodendrocyte glycoprotein antibody-IgG+ patients (62.2% female) had appropriate samples. Antibody titres significantly increased from 'pre-attack' to 'attack', decreased from 'attack' to 'post-attack', and remained stable from 2 to 4 years after attacks. Long-term immunosuppressant treatments induced a further decrease in titres during remission in both cohorts. In 40% of samples in both groups there was an increase in titre at relapse. A ≥ 2-fold increase in AQP4-IgG titres had an Odds Ratio (OR) of 6.59% and 91.5% specificity of being associated with a relapse, in myelin oligodendrocyte glycoprotein antibody-IgG+ an OR of 4.87% and 88.6% specificity. 29% (26/92) AQP4-IgG+ patients became 'seronegative' during follow: most patients (64%) had low attack titres (≤100), and the time to seroreversion related the attack titre. In contrast, 41% (46/111) myelin oligodendrocyte glycoprotein antibody-IgG+ patients became 'seronegative', mostly within the first year after the attack regardless of attack titre. In conclusion, in 60% of longitudinal serum samples from patients with AQP4-IgG or myelin oligodendrocyte glycoprotein antibody-IgG there is no increase in antibody titre. When there is an increase, it is most often at relapse. A ≥ 2-fold increase in titres should be a risk particularly in case of treatment de-escalation, non-adherence to treatment or if a pseudo-relapse is suspected.

Autoantibody-mediated diseases targeting one autoantigen provide a unique opportunity to comprehensively understand the development of disease-causing B cells and autoantibodies. Convention suggests that such autoreactivities are generated during germinal center reactions. Here, we explore earlier immune checkpoints, focusing on patients with contactin-associated protein-like 2 (CASPR2)–autoantibody encephalitis. In both disease and health, high (~0.5%) frequencies of unmutated CASPR2-reactive naïve B cells were identified. By contrast, CASPR2-reactive memory B cells were exclusive to patients, and their B cell receptors demonstrated affinity-enhancing somatic mutations with pathogenic effects in neuronal cultures and mice. The unmutated, precursor memory B cell receptors showed a distinctive balance between strong CASPR2 reactivity and very limited binding across the remaining human proteome. Our results identify permissive central tolerance, defective peripheral tolerance, and autoantigen-specific tolerance thresholds in humans as sequential steps that license CASPR2-directed pathology. By leveraging the basic immunobiology, we rationally direct tolerance-restoring approaches, with an experimental paradigm applicable across autoimmunity.

Importance A proportion of people with myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) have a relapsing disease course and persistent anti-myelin oligodendrocyte glycoprotein immunoglobulin G (MOG-IgG) seropositivity. Few studies have investigated whether treatment of the first MOGAD attack is associated with the long-term disease course and/or MOG-IgG seronegative conversion. Objective To investigate the association of time to treat the first acute MOGAD attack with relapse risk and MOG-IgG serostatus. Design, Setting, and Participants This was a retrospective, nationwide, multicenter cohort study involving 14 secondary or tertiary hospitals in South Korea between November 2009 and August 2023. People with adult-onset MOGAD, who either had a relapse or were followed up for more than 12 months after disease onset and had a detailed medical record of their first attack, were included. Individuals were excluded for adolescent-onset MOGAD or short disease duration. Exposures Patients were categorized based on the time to treat the first acute MOGAD attack: early (<5 days), intermediate (5-14 days), and late (not treated within 14 days). Main Outcomes and Measures A multivariable analysis for clinical and treatment factors associated with relapsing disease course and/or MOG-IgG seronegative conversion. Further subgroup analyses were conducted among those without long-term nonsteroidal immunosuppressant (NSIS) maintenance treatment. Results Among the 315 individuals screened, 75 were excluded. A total of 240 patients (median [IQR] age at onset, 40.4 [28.8-56.1] years; 125 female [52.1%]) with median (IQR) disease duration of 3.07 (1.95-6.15) years were included. A total of 110 of 240 patients (45.8%) relapsed after a median (IQR) of 0.45 (0.18-1.68) years, and 29 of 116 patients (25.0%) experienced a conversion to seronegative MOG-IgG. Both the time to treatment of the first MOGAD attack (late vs early: adjusted hazard ratio [aHR], 2.64; 95% CI, 1.43-4.84; P = .002; intermediate vs early: aHR, 2.02; 95% CI, 1.10-3.74; P = .02) and NSIS maintenance treatment (aHR, 0.24; 95% CI, 0.14-0.42; P < .001) were independently associated with the risk of relapse. In a subgroup without NSIS maintenance, the time to treat of the first MOGAD attack was still associated with higher risk of relapse (late vs early: aHR, 3.51; 95% CI, 1.64-7.50; P = .001; intermediate vs early: aHR, 2.68; 95% CI, 1.23-5.85; P = .01). Lastly, the time to treat of the first MOGAD attack was also associated with MOG-IgG seronegative conversion (early vs late: adjusted odds ratio, 7.04; 95% CI, 1.58-31.41; P = .01), whereas NSIS maintenance treatment was not. Conclusions and Relevance Results of this cohort study suggest that early treatment of the first acute MOGAD attack was associated with a reduction in the proportion of relapsing disease course and an increase in the likelihood of MOG-IgG seronegative conversion. These data suggest that timing of acute phase treatment for the first MOGAD attack can be associated with the long-term prognosis and autoimmune status of patients.