Autoantibodies Targeting Intracellular and Extracellular Proteins in Autoimmunity

Multiple sclerosis: an immune attack on astrocyte-mediated ion and water homeostasis

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the CNS. The chain of events that results in demyelinating lesions is not understood, although most theories assume a primary immune attack on myelin. However, the glial cell adhesion molecule GlialCAM, which forms part of a protein complex in astrocytic endfeet that is crucial for brain ion and water homeostasis, was recently identified as a target for autoimmunity in patients with MS. This complex also includes the astrocytic transmembrane protein MLC1, the water channel aquaporin 4 (AQP4) and the potassium channel KIR4.1. Autoimmunity against AQP4 underlies another demyelinating disorder, neuromyelitis optica, and autoimmunity against KIR4.1 has been implicated in a subtype of MS. Genetic defects in any of these proteins cause leukodystrophies with disruption of brain ion and water homeostasis, which is regulated by astrocytes and secondarily affects myelin. In this Perspective, we argue that an immune attack on the ion and water homeostasis machinery in astrocytic endfeet, rather than directly on myelin, is the primary event in MS and that myelin damage is a consequence of astrocyte dysfunction. This hypothesis is supported by pathological studies on tissue from people with MS and has important implications for disease models and therapy targets.

Identification of B cell antigens in solid cancer: initial insights and functional implications

Cancer antigen discovery has mostly focused on T cell antigens, while antigens driving B cell responses have been largely overlooked despite representing another important branch of adaptive immune responses in cancer. Traditional B cell antigens in cancer have been studied using serological approaches analyzing polyclonal antibodies in serum. With recent technological advances in single-cell sequencing, a few studies have begun to investigate single B cell antigen specificity in the tumor microenvironment using immunoglobulin single-cell sequencing, recombinant monoclonal antibody production, cancer binding screening, and antigen identification. In this review, we highlight the initial insights into B cell directed cancer antigens and categorize them into cancer-associated viral antigens and non-viral antigens, with the latter featuring autoantigens. We will further discuss the functions of B cells in cancer in the context of their antigen specificity, and categorize their functions into antibody effector function, T cell activation, and B cell secretion. Lastly, we will provide perspectives on the challenges and opportunities in the identification of new B cell cancer antigens and highlight their translational potential.

Understanding chronic inflammation: couplings between cytokines, ROS, NO, Cai 2+, HIF-1α, Nrf2 and autophagy

Chronic inflammation is an important component of many diseases, including autoimmune diseases, intracellular infections, dysbiosis and degenerative diseases. An important element of this state is the mainly positive feedback between inflammatory cytokines, reactive oxygen species (ROS), nitric oxide (NO), increased intracellular calcium, hypoxia-inducible factor 1-alpha (HIF-1α) stabilisation and mitochondrial oxidative stress, which, under normal conditions, enhance the response against pathogens. Autophagy and the nuclear factor erythroid 2-related factor 2 (Nrf2)-mediated antioxidant response are mainly negatively coupled with the above-mentioned elements to maintain the defence response at a level appropriate to the severity of the infection. The current review is the first attempt to build a multidimensional model of cellular self-regulation of chronic inflammation. It describes the feedbacks involved in the inflammatory response and explains the possible pathways by which inflammation becomes chronic. The multiplicity of positive feedbacks suggests that symptomatic treatment of chronic inflammation should focus on inhibiting multiple positive feedbacks to effectively suppress all dysregulated elements including inflammation, oxidative stress, calcium stress, mito-stress and other metabolic disturbances.

Strong Association of Autoantibodies Targeting Deamidated Extracellular Epitopes of Insulinoma Antigen-2 With Clinical Onset of Type 1 Diabetes

ARTICLE HIGHLIGHTS

CD4+ T cells from patients with type 1 diabetes (T1D) have a significant response to post-translationally modified (PTM) deamidated IA-2 peptides; autoantibodies to these PTM neoepitopes remain to be identified in T1D. We aimed to identify autoantibodies specifically targeting reported T-cell reactive, deamidated epitopes of IA-2 and explore their relationship with T1D development. Autoantibodies to deamidated IA-2 were specific to deamidated epitopes and were predominantly present during the late stages of T1D development, challenging the hypothesis that the loss of immune tolerance occurs via post-translational modification of islet antigens. Newly identified autoantibodies to deamidated IA-2 are new biomarkers of islet autoimmunity and have the potential to aid in T1D diagnosis.

Disruption of RNA-binding proteins in neurological disorders

RNA-binding proteins (RBPs) are multifunctional proteins essential for the regulation of RNA processing and metabolism, contributing to the maintenance of cell homeostasis by modulating the expression of target genes. Many RBPs have been associated with neuron-specific processes vital for neuronal development and survival. RBP dysfunction may result in aberrations in RNA processing, which subsequently initiate a cascade of effects. Notably, RBPs are involved in the onset and progression of neurological disorders via diverse mechanisms. Disruption of RBPs not only affects RNA processing, but also promotes the abnormal aggregation of proteins into toxic inclusion bodies, and contributes to immune responses that drive the progression of neurological diseases. In this review, we summarize recent discoveries relating to the roles of RBPs in neurological diseases, discuss their contributions to such conditions, and highlight the unique functions of these RBPs within the nervous system.

Autoantibodies in patients with fibromyalgia syndrome

ABSTRACT

The objective of this study was to assess the frequency of IgG autoantibodies in patients with fibromyalgia syndrome (FMS), to characterize their binding to dorsal root ganglion (DRG) neurons and glial cells, and to assess whether specific DRG binding patterns correlate with clinical symptoms. Sera of a cohort of 184 patients with FMS and 55 control sera were used to test binding of patient IgG on rat DRG sections. ELISA, Western blot, and preadsorption tests were used to search for potential target antigens. We found binding to DRGs in 68 of 184 FMS sera and in none of the control sera. We could identify 9 binding clusters including binding to neurons and to cells labelled with the satellite glial cell marker fatty acid binding protein 7 (FABP7). Current pain intensity correlated positively with IgG binding to FABP7 immunoreactive structures, and burning pain was associated with binding to transient receptor potential vanilloid 1 immunoreactive neurons. Specific antibody detection revealed 13 of 68 sera positive for anti-citrullinated peptide antibodies, 9 of 68 positive for SOX1 antibodies, 7 of 68 positive for antibodies against the serotonin receptor 5HT1AR, and 3 of 68 positive for fibroblast growth factor 3 antibodies. Our findings support the notion of an immune activation in a subgroup of patients with FMS.

Serum and tear autoantibodies from NOD and NOR mice as potential diagnostic indicators of local and systemic inflammation in Sjögren's disease

Background

Sjögren's Disease (SjD) is an autoimmune disease characterized by lymphocytic infiltration of salivary and lacrimal glands (LG). The LG produces the protein-rich aqueous component of tears, and SjD-associated autoimmune dacryoadenitis (AD) may thus alter tear autoantibody composition.

Methods

The presence of tertiary lymphoid structures (TLS) in LG from two murine models of SjD-associated AD, male non-obese diabetic (NOD) and male non-obese insulitis resistant (NOR) mice, were evaluated using immunofluorescence. IgG and IgA reactivity in serum and tears from these models were probed in three studies against a panel of 80-120 autoantigens using autoantibody microarrays relative to serum and tears from healthy male BALB/c mice. Sources of Ig in tears were investigated using scRNA-Seq of the LG (GSE132420). Data were analyzed by R package Limma and Seurat.

Results

Analysis of immunofluorescence in LG sections from both SjD models showed TLS. Only one autoantibody was significantly elevated in tears and serum in both SjD models across all studies. Three autoantibodies were significantly elevated in serum but not in tears in both SjD models across all studies. Conversely, six IgG and thirteen IgA autoantibodies (6 sharing the same autoantigen) were significantly elevated in tears but not serum in both SjD models. Igha and Ighg2b expressing cells were identified in the plasma cell cluster of NOD.H2b LG.

Conclusion

NOD and NOR mice with SjD-associated AD have distinct autoantibody profiles in tears and serum. Tear IgA isotype autoantibodies showed a greater diversity than tear IgG autoantibodies. TLS observed in LG are a likely source of the tear autoantibodies.

T cell and autoantibody profiling for primary immune regulatory disorders

Background

Limited clinical tools exist for characterizing primary immune regulatory disorders (PIRD), which are often diagnoses of exclusion. Increased CD4+CXCR5+PD1+ circulating T follicular helper (cTfh) cell percentages have been identified as a marker of active disease in some, but not all, autoimmune disorders.

Objective

To develop a diagnostic approach that combines measurements of cellular and serologic autoimmunity.

Methods

We recruited 71 controls and 101 pediatric patients with PIRD with autoimmunity. Flow cytometry was used to measure CD4+CXCR5+ T cells expressing the chemokine receptors CXCR3 and/or CCR6. IgG and IgA autoantibodies were quantified in 56 patients and 20 controls using a microarray featuring 1616 full-length, conformationally intact protein antigens. The 97.5th percentile in the controls serves as the upper limit of normal for percentages of cTfh cells, CD4+CXCR5+ T cells expressing CXCR3 and/or CCR6, and autoantibody intensity and number.

Results

We found that 27.7% of patients had increased percentages of CD4+CXCR5+PD1+ cTfh cells and 42.5% had increased percentages of CD4+CXCR5+ cells expressing CXCR3 and/or CCR6. Patients had significantly more diverse IgG and IgA autoantibodies than controls and 37.5% had increased numbers of high-titer autoantibodies. Integrating measurements of cTfh cells, CD4+CXCR5+ T cells with CXCR3 and/or CCR6, and numbers of high-titer autoantibodies had 71.4% sensitivity (95% CI: 0.5852 - 0.8158) and 85% specificity (95% CI: 0.6396 - 0.9476) for patients with PIRD compared to controls.

Conclusion

By integrating CD4+ T cell phenotyping and total burden of autoantibodies, this approach provides additional tools for the diagnosis of PIRD lacking clinical diagnostic criteria.

Identification of anti-c, E alloantibodies with autoantibodies mimicking anti-c, E alloantibodies

Objectives

Autoantibodies mimicking alloantibodies (referred to as mimicking antibodies) are a type of specific antibody that reacts with all red blood cells, but exhibits a stronger reaction with red blood cells expressing the target antigens. This study aimed to explore immunohematologic methods for identifying mimicking antibodies, autoantibodies and alloantibodies, and to formulate safe transfusion strategies based on the results.

Methods

ABO, Rh blood types and direct antiglobulin test were determined using the tube saline method. Antibody detection and identification were performed using tube saline and anti-human globulin microcolumn gel method with two sets of panel red blood cells. The specificity of antibodies was confirmed through absorption elution test, antibody dilution and titer integral method.

Results

The study identified the presence of both anti-c and anti-E alloantibodies as well as anti-c and anti-E mimicking antibodies in patient samples. Based on these findings, suitable A-type CCDee donors can be selected for the patient, while avoiding both mimicking antibodies and alloantibodies.

Conclusion

When mimicking antibodies, autoantibodies and alloantibodies are present in patients, either separately or simultaneously, antibody identification can be challenging. Accurate determination of the type and specificity of antibodies is essential for developing safe transfusion strategies in clinical practice.

Turncoat antibodies unmasked in a model of autoimmune demyelination: from biology to therapy

Autoantibodies contribute to many autoimmune diseases, yet there is no approved therapy to neutralize them selectively. A popular mouse model, experimental autoimmune encephalomyelitis (EAE), could serve to develop such a therapy, provided we can better understand the nature and importance of the autoantibodies involved. Here we report the discovery of autoantibody-secreting extrafollicular plasmablasts in EAE induced with specific myelin oligodendrocyte glycoprotein (MOG) antigens. Single-cell RNA sequencing reveals that these cells produce non-affinity-matured IgG antibodies. These include pathogenic antibodies competing for shared binding space on MOG's extracellular domain. Interestingly, the synthetic anti-MOG antibody 8-18C5 can prevent the binding of pathogenic antibodies from either EAE mice or people with MOG antibody disease (MOGAD). Moreover, an 8-18C5 variant carrying the NNAS mutation, which inactivates its effector functions, can reduce EAE severity and promote functional recovery. In brief, this study provides not only a comprehensive characterization of the humoral response in EAE models, but also a proof of concept for a novel therapy to antagonize pathogenic anti-MOG antibodies.

Dysregulated plasma autoantibodies are associated with B cell dysfunction in young Arab children with autism spectrum disorder in Qatar

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by impaired social interaction and communication, as well as the occurrence of stereotyped and repetitive behaviors. Previous studies have provided solid evidence of dysregulated immune system in ASD; however, limited studies have investigated autoantibody profiles in individuals with ASD. This study aims to screen plasma autoantibodies in a well-defined cohort of young children with ASD (n = 100) and their matched controls (n = 60) utilizing a high-throughput KoRectly Expressed (KREX) i-Ome protein-array technology. We identified differential protein expression of 16 autoantibodies in ASD, which were correlated with differential gene expression of these markers in independent ASD cohorts. Meanwhile, we identified a distinct list of 33 autoantibodies associated with ASD severity; several of which were correlated with maternal age and birth weight in ASD. In addition, we found dysregulated numbers of circulating B cells and activated HLADR+ B cells in ASD, which were correlated with altered levels of several autoantibodies. Further in-depth analysis of B cell subpopulations revealed an increased frequency of activated naïve B cells in ASD, as well as an association of resting naïve B cells and transitional B cells with ASD severity. Pathway enrichment analysis revealed disrupted MAPK signaling in ASD, suggesting a potential relevance of this pathway to altered autoantibodies and B cell dysfunction in ASD. Finally, we found that a combination of eight autoantibodies associated with ASD severity showed an area under the curve (ROC-AUC) of 0.937 (95% CI = 0.890, 0.983; p < 0.001), which demonstrated the diagnostic accuracy of the eight-marker signature in the severity classification of ASD cases. Overall, this study determined dysregulated autoantibody profiles and B cell dysfunction in children with ASD and identified an eight-autoantibody panel for ASD severity classification.

Mechanisms underlying sex differences in autoimmunity

Autoimmune diseases are a leading cause of disability worldwide. Most autoimmune diseases occur more often in women than men, with rheumatic autoimmune diseases being among those most highly expressed in women. Several key factors, identified mainly in animal models and cell culture experiments, are important in increasing autoimmune disease in females. These include sex hormones, immune genes including those found on the X chromosome, sex-specific epigenetic effects on genes by estrogen and the environment, and regulation of genes and messenger RNA by microRNAs found in extracellular vesicles. Evidence is also emerging that viruses as well as drugs or toxins that damage mitochondria may contribute to increased levels of autoantibodies against nuclear and mitochondrial antigens, which are common in many autoimmune diseases. The purpose of this Review is to summarize our current understanding of mechanisms that may determine sex differences in autoimmune disease.

Autoantibodies in COVID-19 and Other Viral Diseases: Molecular, Cellular, and Clinical Perspectives

Autoantibodies are immune system-produced antibodies that wrongly target the body's cells and tissues for attack. The COVID-19 pandemic has made it possible to link autoantibodies to both the severity of pathogenic infection and the emergence of several autoimmune diseases after recovery from the infection. An overview of autoimmune disorders and the function of autoantibodies in COVID-19 and other infectious diseases are discussed in this review article. We also investigated the different categories of autoantibodies found in COVID-19 and other infectious diseases including the potential pathways by which they contribute to the severity of the illness. Additionally, it also highlights the probable connection between vaccine-induced autoantibodies and their adverse outcomes. The review also discusses the therapeutic perspectives of autoantibodies. This paper advances our knowledge about the intricate interaction between autoantibodies and COVID-19 by thoroughly assessing the most recent findings.

Clinical Significance of Uncommon, Non-Clinical, and Novel Autoantibodies

Autoantibodies are a common mark of autoimmune reaction and their identification in the patients' serum, cerebrospinal fluid, or tissues is generally believed to represent diagnostic or prognostic biomarkers of autoimmune diseases or autoinflammatory conditions. Traditionally, autoantibody testing is an important part of the clinical examination of suspected patients, and in the absence of reliable T cell tests, characterization of autoantibody responses might be suitable in finding causes of specific autoimmune responses, their strength, and sometimes commencement of autoimmune disease. Autoantibodies are also useful for prognostic stratification in clinically diverse groups of patients if checked repeatedly. Antibody discoveries are continuing, with important consequences for verifying autoimmune mechanisms, diagnostic feasibility, and clinical management. Adding newly identified autoantibody-autoantigen pairs to common clinical laboratory panels should help upgrade and harmonize the identification of systemic autoimmune rheumatic disorders and other autoimmune conditions. Herein, we aim to summarize our current knowledge of uncommon and novel autoantibodies in the context of discussing their validation, diagnostic practicability, and clinical relevance. The regular updates within the field are important and well justified.

Autoimmune diseases: targets, biology, and drug discovery

Autoimmune diseases (AIDs) arise from a breakdown in immunological self-tolerance, wherein the adaptive immune system mistakenly attacks healthy cells, tissues and organs. AIDs impose excessive treatment costs and currently rely on non-specific and universal immunosuppression, which only offer symptomatic relief without addressing the underlying causes. AIDs are driven by autoantigens, targeting the autoantigens holds great promise in transforming the treatment of these diseases. To achieve this goal, a comprehensive understanding of the pathogenic mechanisms underlying different AIDs and the identification of specific autoantigens are critical. In this review, we categorize AIDs based on their underlying causes and compile information on autoantigens implicated in each disease, providing a roadmap for the development of novel immunotherapy regimens. We will focus on type 1 diabetes (T1D), which is an autoimmune disease characterized by irreversible destruction of insulin-producing β cells in the Langerhans islets of the pancreas. We will discuss insulin as possible autoantigen of T1D and its role in T1D pathogenesis. Finally, we will review current treatments of TID and propose a potentially effective immunotherapy targeting autoantigens.

The good or the bad: an overview of autoantibodies in traumatic spinal cord injury

Infections remain the most common cause of death after traumatic spinal cord injury, likely due to a developing immune deficiency syndrome. This, together with a somewhat contradictory development of autoimmunity in many patients, are two major components of the maladaptive systemic immune response. Although the local non-resolving inflammation in the lesioned spinal cord may lead to an antibody formation against autoantigens of the injured spinal cord tissue, there are also natural (pre-existing) autoantibodies independent of the injury. The way in which these autoantibodies with different origins affect the neuronal and functional outcome of spinal cord-injured patients is still controversial.

[Autoimmunity in rheumatology: A review]

Autoimmunity and autoinflammation, co-potentiating pathological processes, are considered within the "immune-inflammatory" continuum (continuity with a variety of elements), reflecting the close relationship between the innate and acquired immune responses. Autoimmunity is the leading pathogenetic mechanism for a specific type of human chronic inflammatory disorders - autoimmune diseases, affecting more than 10% of people in the general population. Advances in molecular biology, pharmacogenetics, and bioinformatics provided the background for individualizing therapy for systemic autoimmune rheumatic diseases within personalized medicine. Studying the immunopathogenesis mechanisms, improving diagnostics, interpreting the molecular taxonomy, and developing approaches to the prevention and personalized therapy of systemic autoimmune rheumatic diseases are the priority issues of modern medicine.

Pathophysiological Effects of Autoantibodies in Autoimmune Encephalitides

The heterogeneity of autoantibody targets in autoimmune encephalitides presents a challenge for understanding cellular and humoral pathophysiology, and the development of new treatment strategies. Thus, current treatment aims at autoantibody removal and immunosuppression, and is primarily based on data generated from other autoimmune neurological diseases and expert consensus. There are many subtypes of autoimmune encephalitides, which now entails both diseases with autoantibodies targeting extracellular antigens and classical paraneoplastic syndromes with autoantibodies targeting intracellular antigens. Here, we review the current knowledge of molecular and cellular effects of autoantibodies associated with autoimmune encephalitis, and evaluate the evidence behind the proposed pathophysiological mechanisms of autoantibodies in autoimmune encephalitis.

Recent Advances in Folates and Autoantibodies against Folate Receptors in Early Pregnancy and Miscarriage

Though firstly identified in cerebral folate deficiency, autoantibodies against folate receptors (FRAbs) have been implicated in pregnancy complications such as miscarriage; however, the underlying mechanism needs to be further elaborated. FRAbs can be produced via sensitization mediated by folate-binding protein as well as gene mutation, aberrant modulation, or degradation of folate receptors (FRs). FRAbs may interfere with folate internalization and metabolism through blocking or binding with FRs. Interestingly, different types of FRs are expressed on trophoblast cells, decidual epithelium or stroma, and macrophages at the maternal-fetal interface, implying FRAbs may be involved in the critical events necessary for a successful pregnancy. Thus, we propose that FRAbs may disturb pregnancy establishment and maintenance by modulating trophoblastic biofunctions, placental development, decidualization, and decidua homeostasis as well as the functions of FOLR2+ macrophages. In light of these findings, FRAbs may be a critical factor in pathological pregnancy, and deserve careful consideration in therapies involving folic acid supplementation for pregnancy complications.

The role of inflammation in autoimmune disease: a therapeutic target

Autoimmune diseases (AIDs) are immune disorders whose incidence and prevalence are increasing year by year. AIDs are produced by the immune system's misidentification of self-antigens, seemingly caused by excessive immune function, but in fact they are the result of reduced accuracy due to the decline in immune system function, which cannot clearly identify foreign invaders and self-antigens, thus issuing false attacks, and eventually leading to disease. The occurrence of AIDs is often accompanied by the emergence of inflammation, and inflammatory mediators (inflammatory factors, inflammasomes) play an important role in the pathogenesis of AIDs, which mediate the immune process by affecting innate cells (such as macrophages) and adaptive cells (such as T and B cells), and ultimately promote the occurrence of autoimmune responses, so targeting inflammatory mediators/pathways is one of emerging the treatment strategies of AIDs. This review will briefly describe the role of inflammation in the pathogenesis of different AIDs, and give a rough introduction to inhibitors targeting inflammatory factors, hoping to have reference significance for subsequent treatment options for AIDs.

Hydrophobicity and molecular mass-based separation method for autoantibody discovery from mammalian total cellular proteins

Serum autoantibody profiles are unique to individuals and reflect the level and history of autoimmunity and tumor immunity. The identification of autoantibody biomarkers is critical for the development of immune monitoring systems for immune-related disorders. Here, we present a practical method for large-scale autoantibody discovery using total cellular proteins from cultured mammalian cells. We found that nucleic acid-free and fully denatured water-soluble total cellular proteins from mammalian cells were superior, allowing precise separation by reversed-phase HPLC after preparing a large set of homogeneous total cellular proteins. After separating the proteins based on hydrophobicity, the fractionated samples were subjected to molecular mass analysis using conventional SDS-PAGE. The resulting two-dimensional gel electrophoresis was successfully employed for immune blotting and LC-MS/MS analysis. All procedures, including TRIzol-based total cellular protein extraction, solubilization of denatured proteins, reversed-phase HPLC separation, and SDS-PAGE, were highly reproducible and easily scalable. We propose this novel two-dimensional gel electrophoresis system as an alternative proteomics-based methodology suitable for large-scale autoantibody discovery.

Mining Autoimmune-Disorder-Linked Molecular-Mimicry Candidates in Clostridioides difficile and Prospects of Mimic-Based Vaccine Design: An In Silico Approach

Molecular mimicry, a phenomenon in which microbial or environmental antigens resemble host antigens, has been proposed as a potential trigger for autoimmune responses. In this study, we employed a bioinformatics approach to investigate the role of molecular mimicry in Clostridioides difficile-caused infections and the induction of autoimmune disorders due to this phenomenon. Comparing proteomes of host and pathogen, we identified 23 proteins that exhibited significant sequence homology and were linked to autoimmune disorders. The disorders included rheumatoid arthritis, psoriasis, Alzheimer's disease, etc., while infections included viral and bacterial infections like HIV, HCV, and tuberculosis. The structure of the homologous proteins was superposed, and RMSD was calculated to find the maximum deviation, while accounting for rigid and flexible regions. Two sequence mimics (antigenic, non-allergenic, and immunogenic) of ≥10 amino acids from these proteins were used to design a vaccine construct to explore the possibility of eliciting an immune response. Docking analysis of the top vaccine construct C2 showed favorable interactions with HLA and TLR-4 receptor, indicating potential efficacy. The B-cell and T-helper cell activity was also simulated, showing promising results for effective immunization against C. difficile infections. This study highlights the potential of C. difficile to trigger autoimmunity through molecular mimicry and vaccine design based on sequence mimics that trigger a defensive response.

Antibody Cross-Reactivity in Auto-Immune Diseases

Autoimmunity is defined by the presence of antibodies and/or T cells directed against self-components. Although of unknown etiology, autoimmunity commonly is associated with environmental factors such as infections, which have been reported to increase the risk of developing autoimmune diseases. Occasionally, similarities between infectious non-self and self-tissue antigens may contribute to immunological cross-reactivity in autoimmune diseases. These reactions may be interpreted as molecular mimicry, which describes cross-reactivity between foreign pathogens and self-antigens that have been reported to cause tissue damage and to contribute to the development of autoimmunity. By focusing on the nature of antibodies, cross-reactivity in general, and antibody-antigen interactions, this review aims to characterize the nature of potential cross-reactive immune reactions between infectious non-self and self-tissue antigens which may be associated with autoimmunity but may not actually be the cause of disease onset.

Autoantibodies identify primary Sjögren's syndrome in patients lacking serum IgG specific for Ro/SS-A and La/SS-B

OBJECTIVE

Identify autoantibodies in anti-Ro/SS-A negative primary Sjögren's syndrome (SS).

METHODS

This is a proof-of-concept, case-control study of SS, healthy (HC) and other disease (OD) controls. A discovery dataset of plasma samples (n=30 SS, n=15 HC) was tested on human proteome arrays containing 19 500 proteins. A validation dataset of plasma and stimulated parotid saliva from additional SS cases (n=46 anti-Ro+, n=50 anti-Ro-), HC (n=42) and OD (n=54) was tested on custom arrays containing 74 proteins. For each protein, the mean+3 SD of the HC value defined the positivity threshold. Differences from HC were determined by Fisher's exact test and random forest machine learning using 2/3 of the validation dataset for training and 1/3 for testing. Applicability of the results was explored in an independent rheumatology practice cohort (n=38 Ro+, n=36 Ro-, n=10 HC). Relationships among antigens were explored using Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) interactome analysis.

RESULTS

Ro+ SS parotid saliva contained autoantibodies binding to Ro60, Ro52, La/SS-B and muscarinic receptor 5. SS plasma contained 12 novel autoantibody specificities, 11 of which were detected in both the discovery and validation datasets. Binding to ≥1 of the novel antigens identified 54% of Ro- SS and 37% of Ro+ SS cases, with 100% specificity in both groups. Machine learning identified 30 novel specificities showing receiver operating characteristic area under the curve of 0.79 (95% CI 0.64 to 0.93) for identifying Ro- SS. Sera from Ro- cases of an independent cohort bound 17 of the non-canonical antigens. Antigenic targets in both Ro+ and Ro- SS were part of leukaemia cell, ubiquitin conjugation and antiviral defence pathways.

CONCLUSION

We identified antigenic targets of the autoantibody response in SS that may be useful for identifying up to half of Ro seronegative SS cases.

Potential Role of Antibodies against Aquaporin-1 in Patients with Central Nervous System Demyelination

Aquaporins (AQPs; AQP0-AQP12) are water channels expressed in many and diverse cell types, participating in various functions of cells, tissues, and systems, including the central nervous system (CNS). AQP dysfunction and autoimmunity to AQPs are implicated in several diseases. The best-known example of autoimmunity against AQPs concerns the antibodies to AQP4 which are involved in the pathogenesis of neuromyelitis optica spectrum disorder (NMOSD), an autoimmune astrocytopathy, causing also CNS demyelination. The present review focuses on the discovery and the potential role of antibodies against AQP1 in the CNS, and their potential involvement in the pathophysiology of NMOSD. We describe (a) the several techniques developed for the detection of the AQP1-antibodies, with emphasis on methods that specifically identify antibodies targeting the extracellular domain of AQP1, i.e., those of potential pathogenic role, and (b) the available evidence supporting the pathogenic relevance of AQP1-antibodies in the NMOSD phenotype.

Anti-topoisomerase 1 Antibody Level Changes after B Cell Depletion Therapy in Systemic Sclerosis

The aim of our study was to assess the relationship between the changes of antinuclear autoantibodies (ANAs) and autoantibodies to topoisomerase 1 (anti-Topo 1) in systemic sclerosis (SSs) patients on rituximab (RTX) therapy. The prospective study included 88 patients (73 women) with a mean age of 47 (17-71) years. The mean disease duration was 5.9 ± 4.8 years. The mean follow-up period was more than 2 years (27 (12-42) months). We documented a statistically significant change in skin score, the disease activity index, improvement of pulmonary function and reduction of mean dose of prednisolone after RTX treatment. There was a significant decrease in the number of patients with high levels of ANA and overall decrease of the ANA and anti-Topo 1 levels. A moderate positive statistically significant correlation was found between ANA and anti-Topo 1 (r = 0.403). In the group of patients positive for anti-Topo 1 there were a more pronounced depletion of B lymphocytes, significantly higher increase in forced vital capacity and diffusion capacity, decrease in the disease activity index, compared with patients negative for anti-Topo 1. We observed the decline in the level of ANA and anti-Topo 1 in SSc patients after RTX therapy, and it was correlated by an improvement of the main outcome parameters of the disease. Therefore, anti-Topo 1 positivity could be considered as a predictor of a better response to RTX treatment, especially in SSc patients with hyperproduction of anti-Topo 1.

Clinical and prognostic associations of autoantibodies recognizing adrenergic/muscarinic receptors in patients with heart failure

AIMS

The importance of autoantibodies (AABs) against adrenergic/muscarinic receptors in heart failure (HF) is not well-understood. We investigated the prevalence and clinical/prognostic associations of four AABs recognizing the M2-muscarinic receptor or the β1-, β2-, or β3-adrenergic receptor in a large and well-characterized cohort of patients with HF.

METHODS AND RESULTS

Serum samples from 2256 patients with HF from the BIOSTAT-CHF cohort and 299 healthy controls were analysed using newly established chemiluminescence immunoassays. The primary outcome was a composite of all-cause mortality and HF rehospitalization at 2-year follow-up, and each outcome was also separately investigated. Collectively, 382 (16.9%) patients and 37 (12.4%) controls were seropositive for ≥1 AAB (P = 0.045). Seropositivity occurred more frequently only for anti-M2 AABs (P = 0.025). Amongst patients with HF, seropositivity was associated with the presence of comorbidities (renal disease, chronic obstructive pulmonary disease, stroke, and atrial fibrillation) and with medication use. Only anti-β1 AAB seropositivity was associated with the primary outcome [hazard ratio (95% confidence interval): 1.37 (1.04-1.81), P = 0.024] and HF rehospitalization [1.57 (1.13-2.19), P = 0.010] in univariable analyses but remained associated only with HF rehospitalization after multivariable adjustment for the BIOSTAT-CHF risk model [1.47 (1.05-2.07), P = 0.030]. Principal component analyses showed considerable overlap in B-lymphocyte activity between seropositive and seronegative patients, based on 31 circulating biomarkers related to B-lymphocyte function.

CONCLUSIONS

AAB seropositivity was not strongly associated with adverse outcomes in HF and was mostly related to the presence of comorbidities and medication use. Only anti-β1 AABs were independently associated with HF rehospitalization. The exact clinical value of AABs remains to be elucidated.

Advanced methods and novel biomarkers in autoimmune diseases ‑ a review of the recent years progress in systemic lupus erythematosus

There are several autoimmune and rheumatic diseases affecting different organs of the human body. Multiple sclerosis (MS) mainly affects brain, rheumatoid arthritis (RA) mainly affects joints, Type 1 diabetes (T1D) mainly affects pancreas, Sjogren's syndrome (SS) mainly affects salivary glands, while systemic lupus erythematosus (SLE) affects almost every organ of the body. Autoimmune diseases are characterized by production of autoantibodies, activation of immune cells, increased expression of pro-inflammatory cytokines, and activation of type I interferons. Despite improvements in treatments and diagnostic tools, the time it takes for the patients to be diagnosed is too long, and the main treatment for these diseases is still non-specific anti-inflammatory drugs. Thus, there is an urgent need for better biomarkers, as well as tailored, personalized treatment. This review focus on SLE and the organs affected in this disease. We have used the results from various rheumatic and autoimmune diseases and the organs involved with an aim to identify advanced methods and possible biomarkers to be utilized in the diagnosis of SLE, disease monitoring, and response to treatment.

Biological mechanisms underpinning the development of long COVID

As COVID-19 evolves from a pandemic to an endemic disease, the already staggering number of people that have been or will be infected with SARS-CoV-2 is only destined to increase, and the majority of humanity will be infected. It is well understood that COVID-19, like many other viral infections, leaves a significant fraction of the infected with prolonged consequences. Continued high number of SARS-CoV-2 infections, viral evolution with escape from post-infection and vaccinal immunity, and reinfections heighten the potential impact of Long COVID. Hence, the impact of COVID-19 on human health will be seen for years to come until more effective vaccines and pharmaceutical treatments become available. To that effect, it is imperative that the mechanisms underlying the clinical manifestations of Long COVID be elucidated. In this article, we provide an in-depth analysis of the evidence on several potential mechanisms of Long COVID and discuss their relevance to its pathogenesis.

Uncommon types of autoantibodies - Detection and clinical associations

Immunofluorescence is a basic method for detection of autoantibodies in serum. It is used as screening for people with symptoms suggesting autoimmune process and disease. Antinuclear antibodies (ANA) assay detecting antibodies against nuclear proteins used commonly for diagnosis of systemic autoimmune disease, although antibodies against cytoplasmic components and mitotic structures are usable in clinic. The majority of ANA nuclear patterns have been comprehensively studied with increasing data. However, the cytoplasmic and mitotic patterns are underestimated and still require further assessment. In this review the clinical associations and significance of uncommon types of autoantibodies are presented and discussed.

Maternal brain reactive antibodies profile in autism spectrum disorder: an update

Autism spectrum disorder (ASD) is a heterogeneous neurodevelopmental disorder with multifactorial etiologies involving both genetic and environmental factors. In the past two decades it has become clear that in utero exposure to toxins, inflammation, microbiome, and antibodies (Abs), may play a role in the etiology of ASD. Maternal brain-reactive Abs, present in 10-20% of mothers of a child with ASD, pose a potential risk to the developing brain because they can gain access to the brain during gestation, altering brain development during a critical period. Different maternal anti-brain Abs have been associated with ASD and have been suggested to bind extracellular or intracellular neuronal antigens. Clinical data from various cohorts support the increase in prevalence of such maternal brain-reactive Abs in mothers of a child with ASD compared to mothers of a typically developing child. Animal models of both non-human primates and rodents have provided compelling evidence supporting a pathogenic role of these Abs. In this review we summarize the data from clinical and animal models addressing the role of pathogenic maternal Abs in ASD. We propose that maternal brain-reactive Abs are an overlooked and promising field of research, representing a modifiable risk factor that may account for up to 20% of cases of ASD. More studies are needed to better characterize the Abs that contribute to the risk of having a child with ASD, to understand whether we can we predict such cases of ASD, and to better pinpoint the antigenic specificity of these Abs and their mechanisms of pathogenicity.

Thymus antibody-secreting cells: once forgotten but not lost

Antibody-secreting cells are essential contributors to the humoral response. This is due to multiple factors which include: 1) the ability to secrete thousands of antibodies per second, 2) the ability to regulate the immune response and 3) the potential to be long-lived. Not surprisingly, these cells can be found in numerous sites within the body which include organs that directly interface with potential pathogens (e.g., gut) and others that provide long-term survival niches (e.g., bone marrow). Even though antibody-secreting cells were first identified in the thymus of both humans and rodents in the 1960s, if not earlier, only recently has this population begun to be extensively investigated. In this article, we provide an update regarding the current breath of knowledge pertaining to thymus antibody-secreting cells and discuss the potential roles of these cells and their impact on health.

Repositioning synthetic glucocorticoids in psychiatric disease associated with neural autoantibodies: a narrative review

Synthetic glucocorticoids (sGCs) are a well-investigated and standard drug therapy for disorders associated with CNS inflammation. Less is known about treating psychiatric disorders associated with neural autoantibodies. Our aim is to elucidate the repositioning of sGCs in psychiatric diseases that co-exist with neural autoantibodies. We used PubMed to identify articles for this narrative review. To our knowledge, no randomized, placebo-controlled trials have yet been conducted on applying sGC to treat neural autoantibody-associated psychiatric disorders. We describe initial results of cohort studies and single cases or case series often associated with autoantibodies against membrane-surface antigens demonstrating a largely beneficial response to sGCs either as monotherapy or polytherapy together with other immunosuppressive agents. However, sGCs may be less efficient in patients with psychiatric diseases associated with autoantibodies directed against intracellular antigens. These results reveal potential benefits of the novel usage of sGCs for the indication of neural autoantibody-associated psychiatric disease. Further large-scale randomized, placebo-controlled trials are needed to discover whether sGCs are safe, well tolerated, and beneficial in subgroups of neural autoantibody-associated psychiatric diseases.

The relationship between chronic immune response and neurodegenerative damage in long COVID-19

In the past two years, the world has faced the pandemic caused by the severe acute respiratory syndrome 2 coronavirus (SARS-CoV-2), which by August of 2022 has infected around 619 million people and caused the death of 6.55 million individuals globally. Although SARS-CoV-2 mainly affects the respiratory tract level, there are several reports, indicating that other organs such as the heart, kidney, pancreas, and brain can also be damaged. A characteristic observed in blood serum samples of patients suffering COVID-19 disease in moderate and severe stages, is a significant increase in proinflammatory cytokines such as interferon-α (IFN-α), interleukin-1β (IL-1β), interleukin-2 (IL-2), interleukin-6 (IL-6) and interleukin-18 (IL-18), as well as the presence of autoantibodies against interferon-α (IFN-α), interferon-λ (IFN-λ), C-C motif chemokine ligand 26 (CCL26), CXC motif chemokine ligand 12 (CXCL12), family with sequence similarity 19 (chemokine (C-C motif)-like) member A4 (FAM19A4), and C-C motif chemokine ligand 1 (CCL1). Interestingly, it has been described that the chronic cytokinemia is related to alterations of blood-brain barrier (BBB) permeability and induction of neurotoxicity. Furthermore, the generation of autoantibodies affects processes such as neurogenesis, neuronal repair, chemotaxis and the optimal microglia function. These observations support the notion that COVID-19 patients who survived the disease present neurological sequelae and neuropsychiatric disorders. The goal of this review is to explore the relationship between inflammatory and humoral immune markers and the major neurological damage manifested in post-COVID-19 patients.

Consensus on the Key Characteristics of Immunotoxic Agents as a Basis for Hazard Identification

BACKGROUND

Key characteristics (KCs), properties of agents or exposures that confer potential hazard, have been developed for carcinogens and other toxicant classes. KCs have been used in the systematic assessment of hazards and to identify assay and data gaps that limit screening and risk assessment. Many of the mechanisms through which pharmaceuticals and occupational or environmental agents modulate immune function are well recognized. Thus KCs could be identified for immunoactive substances and applied to improve hazard assessment of immunodulatory agents.

OBJECTIVES

The goal was to generate a consensus-based synthesis of scientific evidence describing the KCs of agents known to cause immunotoxicity and potential applications, such as assays to measure the KCs.

METHODS

A committee of 18 experts with diverse specialties identified 10 KCs of immunotoxic agents, namely, 1) covalently binds to proteins to form novel antigens, 2) affects antigen processing and presentation, 3) alters immune cell signaling, 4) alters immune cell proliferation, 5) modifies cellular differentiation, 6) alters immune cell-cell communication, 7) alters effector function of specific cell types, 8) alters immune cell trafficking, 9) alters cell death processes, and 10) breaks down immune tolerance. The group considered how these KCs could influence immune processes and contribute to hypersensitivity, inappropriate enhancement, immunosuppression, or autoimmunity.

DISCUSSION

KCs can be used to improve efforts to identify agents that cause immunotoxicity via one or more mechanisms, to develop better testing and biomarker approaches to evaluate immunotoxicity, and to enable a more comprehensive and mechanistic understanding of adverse effects of exposures on the immune system. https://doi.org/10.1289/EHP10800.

Seronegative autoimmune diseases: A challenging diagnosis

Autoimmune diseases (AID) are increasingly prevalent conditions which comprise more than 100 distinct clinical entities that are responsible for a great disease burden worldwide. The early recognition of these diseases is key for preventing their complications and for tailoring proper management. In most cases, autoantibodies, regardless of their potential pathogenetic role, can be detected in the serum of patients with AID, helping clinicians in making a definitive diagnosis and allowing screening strategies for early -and sometimes pre-clinical- diagnosis. Despite their undoubted crucial role, in a minority of cases, patients with AID may not show any autoantibody, a condition that is referred to as seronegative AID. Suboptimal accuracy of the available laboratory tests, antibody absorption, immunosuppressive therapy, immunodeficiencies, antigen exhaustion, and immunosenescence are the main possible determinants of seronegative AID. Indeed, in seronegative AID, the diagnosis is more challenging and must rely on clinical features and on other available tests, often including histopathological evaluation and radiological diagnostic tests. In this review, we critically dissect, in a narrative fashion, the possible causes of seronegativity, as well as the diagnostic and management implications, in several AID including autoimmune gastritis, celiac disease, autoimmune liver disease, rheumatoid arthritis, autoimmune encephalitis, myasthenia gravis, Sjögren's syndrome, antiphospholipid syndrome, and autoimmune thyroid diseases.

Autoantibodies in central nervous system and neuromuscular autoimmune disorders: A narrative review

The discovery of novel autoantibodies in neurological disorders contributes to a better understanding of its pathogenesis, improves the accuracy of diagnosis, and leads to new treatment strategies. Advances in techniques for the screening and detection of autoantibodies have enabled the discovery of new antibodies in the central nervous system (CNS) and neuromuscular diseases. Cell-based assays using live or fixed cells overexpressing target antigens are widely used for autoantibody-based diagnosis in clinical practice. Common pathogenic autoantibodies are unknown in most patients with multiple sclerosis (MS) and chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). Novel pathogenic autoantibodies to aquaporin-4 and myelin oligodendrocyte glycoprotein (MOG) have been identified in neuromyelitis optica spectrum disorder and MOG antibody-associated disease, respectively. These diseases have clinical similarities to MS, but with the discovery of pathogenic autoantibodies, they are now recognized as distinct disease entities. Antibodies to paranodal membrane proteins such as neurofascin-155, contactin‑1, contactin‑associated protein‑1 in CIDP and muscle-specific kinase and low-density lipoprotein receptor–related protein 4 in myasthenia gravis were added to the profiles of autoantibodies in neurological disorders. Despite the relatively low frequency of seropositivity, autoantibody detection is currently essential for the clinical diagnosis of CNS and neuromuscular autoimmune disorders, and differential approaches to seropositive patients will contribute to more personalized medicine. We reviewed recent discoveries of autoantibodies and their clinical implications in CNS and neuromuscular disorders.

Discovery of Novel Circulating Immune Complexes in Lupus Nephritis Using Immunoproteomics

Objective

The goal is to discover novel circulating immune complexes (ICx) in the serum of lupus nephritis (LN) as potential biomarkers.

Methods

Protein A/G magnetic beads or C1q-coated plates were used to capture ICx in the serum of LN, followed by the identification of immunoglobulin-binding proteins using liquid chromatography and tandem mass spectrometry (LC-MS/MS). Bioinformatic approaches and single-cell RNA sequencing (scRNA Seq) databases were used to select potential candidate ICx markers in LN. The selected ICx markers were further validated using ELISA.

Results

A total of 300 immunoglobulin-binding proteins were discovered in the screening, among which 77 proteins were detectable only in LN samples. Bioinformatics-assisted selection allowed us to further identify 10 potential immunoglobulin-binding proteins, which form ICx as potential biomarkers in LN. In a validation cohort of 62 LN patients and 21 healthy controls (HC), we found that prolyl 3-hydroxylase 1 (P3H1), phosphatase and actin regulator 4 (PHACTR4), and regulator of G-protein signaling 12 (RGS12) ICx exhibited discriminative capability in distinguishing LN from HC, with an area under the curve (AUC) values of 0.82, 0.99, and 0.90, respectively. Furthermore, a biomarker panel comprising CD14, CD34, cystatin A, myocyte enhancer factor 2C (MEF2C), RGS12, and ubiquitin C (UBC) ICx could distinguish active LN from inactive LN with an AUC value of 0.85, which is comparable to or better than pathological parameters such as renal activity index (AI) and renal chronicity index (CI).

Conclusion

Immunoproteomics-based discovery studies have enabled us to identify circulating immune complexes as potential biomarkers of LN.

Autoantibodies directed against glutamate decarboxylase interfere with glucose-stimulated insulin secretion in dispersed rat islets

Islet autoantibodies, including autoantibodies directed against the 65kDa isoform of glutamate decarboxylase (GAD65Ab), are present in the majority of patients with newly diagnosed type 1 diabetes (T1D). Whereas these autoantibodies are historically viewed as an epiphenomenon of the autoimmune response with no significant pathogenic function, we consider in this study the possibility that they impact the major islet function, namely glucose-stimulated insulin secretion. Two human monoclonal GAD65Ab (GAD65 mAb) (b78 and b96.11) were investigated for uptake by live rat beta cells, subcellular localization and their effect on glucose-stimulated insulin secretion. The GAD65 mAbs were internalized by live pancreatic beta cells, where they localized to subcellular structures in an epitope-specific manner. Importantly, GAD65 mAb b78 inhibited, while GAD65 mAb b96.11 enhanced, glucose-stimulated insulin secretion (GSIS). These opposite effects on GSIS rule out non-specific effects of the antibodies and suggest that internalization of the antibody leads to epitope-specific interaction with intracellular machinery regulating insulin granule release. The most likely explanation for the alteration of GSIS by GAD65 Abs is via changes in GABA release due to inhibition or change in GAD65 enzyme activity. This is the first report indicating an active role of GAD65Ab in the pathogenesis of T1D.

Anti-aging vaccines targeting senescent cells

The development of senomorphic drugs to attenuate the senescent phenotype and senolytics to clear pro-inflammatory senescent cells to treat aging-associated disorders is being hotly pursued. The effort is complicated by the fact that senescent cells play a constructive role in some cellular processes such as tissue repair and wound healing. However, concerns about efficacy, which senescent cells to target, and unwanted side effects have created potential roadblocks. Chimeric Antigen Receptor (CAR) T cells directed against urokinase-type plasminogen activator receptor (uPAR), which is expressed on at least a subset of senescent cells (SC) in atherosclerotic plaques and fibrotic livers, removed SC and improved glucose metabolism. A conventional vaccine targeting CD153-expressing senescent T-cells, also improved glucose metabolism in obese mice. Recent work to selectively target senescent cells associated with several pathologies has resulted in the creation of a peptide vaccine that primarily targets endothelial cells expressing high levels of GPNMB, recently identified as a biomarker of senescence. The vaccine reduces atherosclerotic plaque burden and metabolic dysfunction such as glucose intolerance in mouse models of obesity and atherosclerosis. For translation to humans the activity of the vaccine will need to be tightly controlled, as the target, GPNMB has multiple roles in normal physiology including acting to inhibit and possibly resolve inflammation. A promising alternative approach would be to use passive immunization with a monoclonal antibody directed against GPNMB.

Detecting Autoantibodies by Multiparametric Assays: Impact on Prevention, Diagnosis, Monitoring, and Personalized Therapy in Autoimmune Diseases

BACKGROUND

The introduction of multiparametric autoantibody tests has been proposed to improve the accuracy of the immunological diagnosis of autoimmune diseases (AID) and to accelerate time for completing the diagnostic process. Multiplex tests are capable of detecting many autoantibodies in a single run whereas a traditional immunoassay uses a single antigen to detect only a single specificity of autoantibodies. The reasons why multiplex tests could replace conventional immunoassays lie in the evidence that they allow for more efficient handling of large numbers of samples by the laboratory, while ensuring greater diagnostic sensitivity in AID screening.

CONTENT

This review aims to highlight the important role that multiparametric tests could assume when designed for defined profiles they are used not only for diagnostic purposes but also to predict the onset of AID to identify clinical phenotypes and to define prognosis. Furthermore, differences in the antibody profile could identify which subjects will be responsive or not to a specific pharmacological treatment.

SUMMARY

The use of autoantibody profiles, when specifically requested and performed with clinically validated technologies, can represent a significant step toward personalized medicine in autoimmunology.

Amino acid sequence homology between thyroid autoantigens and central nervous system proteins: Implications for the steroid-responsive encephalopathy associated with autoimmune thyroiditis

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Alpha-enolase, aldehyde reductase-I and dimethylargininase-I are SREAT autoantigens.

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Molecular mimicry between thyroid and CNS autoantigens is hypothesized in SREAT.

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Homology with TSH-R, Tg and TPO exists for 6, 27 and 47 of 46,809 CNS-proteins.

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The above homologies are often in epitope-containing parts of thyroid autoantigens.

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Most of the above proteins are expressed in CNS regions which are altered in SREAT.

A few patients with Hashimoto’s thyroiditis or Graves’ disease develop a multiform syndrome of the central nervous system (CNS) termed Hashimoto’s encephalopathy or steroid-responsive encephalopathy associated with autoimmune thyroid disease (HE/SREAT). They have high levels of thyroid autoantibodies (TgAb, TPOAb and/or TSH-R-Ab) in blood and cerebrospinal fluid. Autoantibodies against alpha-enolase, aldehyde reductase-I (AKRIA) and/or dimethylargininase-I (DDAHI), proteins expressed in the CNS among other tissues, were detected in the blood and, when searched, in the cerebrospinal fluid of HE/SREAT patients. Recently, we reported that alpha-enolase, AKRIA and DDAHI share local sequence homology with each of the three autoantigens (TgAb, TPOAb, TSH-R-Ab), often in epitope-containing segments of the thyroid autoantigens. We hypothesized that there might be additional CNS-expressed proteins homologous to thyroid autoantigens, possibly overlapping known epitopes of the thyroid autoantigens. We used bioinformatic methods to address this hypothesis.

Six, 27 and 47 of 46,809 CNS-expressed proteins share homology with TSH-R, Tg and TPO, respectively. The homologous regions often contain epitopes, and some match regions of thyroid autoantigens which have homology with alpha-enolase, AKRIA and/or DDAHI. Several of the aforementioned proteins are present in CNS areas that show abnormalities at neuroimaging in HE/SREAT patients. Furthermore, autoantibodies against some of the said six, 27 and 47 proteins were reported to be associated with a number of autoimmune diseases.

Not only we validated our hypothesis, but we think that such a variety of potential CNS targets for thyroid Ab against epitopes contained in regions that have local homology with CNS proteins may explain the polymorphic phenotypes of HE/SREAT. Only when elevated amounts of these Ab are synthesized and trespass the blood-brain barrier, HE/SREAT appears. This might explain why HE/SREAT is so relatively rare.

Centrality of Myeloid-Lineage Phagocytes in Particle-Triggered Inflammation and Autoimmunity

Exposure to exogenous particles found as airborne contaminants or endogenous particles that form by crystallization of certain nutrients can activate inflammatory pathways and potentially accelerate autoimmunity onset and progression in genetically predisposed individuals. The first line of innate immunological defense against particles are myeloid-lineage phagocytes, namely macrophages and neutrophils, which recognize/internalize the particles, release inflammatory mediators, undergo programmed/unprogrammed death, and recruit/activate other leukocytes to clear the particles and resolve inflammation. However, immunogenic cell death and release of damage-associated molecules, collectively referred to as "danger signals," coupled with failure to efficiently clear dead/dying cells, can elicit unresolved inflammation, accumulation of self-antigens, and adaptive leukocyte recruitment/activation. Collectively, these events can promote loss of immunological self-tolerance and onset/progression of autoimmunity. This review discusses critical molecular mechanisms by which exogenous particles (i.e., silica, asbestos, carbon nanotubes, titanium dioxide, aluminum-containing salts) and endogenous particles (i.e., monosodium urate, cholesterol crystals, calcium-containing salts) may promote unresolved inflammation and autoimmunity by inducing toxic responses in myeloid-lineage phagocytes with emphases on inflammasome activation and necrotic and programmed cell death pathways. A prototypical example is occupational exposure to respirable crystalline silica, which is etiologically linked to systemic lupus erythematosus (SLE) and other human autoimmune diseases. Importantly, airway instillation of SLE-prone mice with crystalline silica elicits severe pulmonary pathology involving accumulation of particle-laden alveolar macrophages, dying and dead cells, nuclear and cytoplasmic debris, and neutrophilic inflammation that drive cytokine, chemokine, and interferon-regulated gene expression. Silica-induced immunogenic cell death and danger signal release triggers accumulation of T and B cells, along with IgG-secreting plasma cells, indicative of ectopic lymphoid tissue neogenesis, and broad-spectrum autoantibody production in the lung. These events drive early autoimmunity onset and accelerate end-stage autoimmune glomerulonephritis. Intriguingly, dietary supplementation with ω-3 fatty acids have been demonstrated to be an intervention against silica-triggered murine autoimmunity. Taken together, further insight into how particles drive immunogenic cell death and danger signaling in myeloid-lineage phagocytes and how these responses are influenced by the genome will be essential for identification of novel interventions for preventing and treating inflammatory and autoimmune diseases associated with these agents.

Roles of IL-1 and IL-10 family cytokines in the progression of systemic lupus erythematosus: Friends or foes?

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease of unknown etiology that can affect nearly every organ system in the body. Besides genetic and environmental factors, unbalanced pro-inflammatory and anti-inflammatory cytokines contribute to immune dysregulation, trigger an inflammatory response, and induce tissue and organ damage. Inflammatory responses in SLE can be promoted and/or maintained by the availability of cytokines that are overproduced systemically and/or in local tissues. Several key cytokines have been considered potential targets for the reduction of chronic inflammation in SLE. Recent studies indicated that dysregulated production of several cytokines, including those of the IL-1 family and IL-10 family, orchestrate immune activation and self-tolerance, play critical roles in the pathogenesis of SLE. Among IL-1 family cytokines, IL-1, IL-18, IL-33, IL-36, IL-37, and IL-38 had been the most thoroughly investigated in SLE. Additionally, IL-10 family cytokines, IL-10, IL-20, IL-22, IL-26, IL-28, and IL-29 are dysregulated in SLE. Therefore, a better understanding of the initiation and progression of SLE may provide suitable novel targets for therapeutic intervention. In this review, we discuss the involvement of inflammation in the pathogenesis of SLE, with a focus on IL-1 family and IL-10 family cytokines, and highlight pathophysiological approaches and therapeutic potential for treating SLE.

In-Depth Evaluation of a Case of Presumed Myocarditis After the Second Dose of COVID-19 mRNA Vaccine

Supplemental Digital Content is available in the text.

A Longitudinal, Observational Analysis of Neuronal Injury Biomarkers in a Case Report of a Patient With Paraneoplastic Anti-CRMP5 Antibody-Associated Transverse Myelitis

Biomarkers are needed to guide therapeutic decision making in autoimmune and paraneoplastic neurologic disorders. Here, we describe a case of paraneoplastic collapsing response-mediator protein-5 (CRMP5)-associated transverse myelitis (TM) where plasma neurofilament light (NfL) chain and glial fibrillary protein (GFAP) levels were observed over a 14-month clinical course, correlating with radiographical and clinical outcome measures in response to treatment. Blood and CSF samples obtained at diagnosis as well as 7 and 14 months into treatment. At the time of initial diagnosis, both plasma NfL (782.62 pg/ml) and GFAP (283.26 pg/ml) were significantly elevated. Initial treatment was with IV steroids and plasma exchange (PLEX) followed by neuroendocrine tumor removal, chemotherapy, and radiation. After initial improvement with chemotherapy, the patient experienced clinical worsening and transient elevation of plasma NfL (103.27 pg/ml and GFAP (211.58 pg/ml) levels. Whole body positron emission tomography PET scan did not demonstrate recurrence of malignancy. Repeat PLEX and rituximab induction resulted in improvements in patient function, neurologic exam, and plasma biomarker levels. To our knowledge, this is the first described longitudinal, prospective analysis of neuronal injury biomarkers and association of clinical treatment outcomes in CRMP5 myelitis. Our findings suggest that clinical improvement correlates with NfL and GFAP concentrations.