Target Of Autoantibodies Research Articles

A master autoantigen-ome links alternative splicing, female predilection, and COVID-19 to autoimmune diseases

Chronic and debilitating autoimmune sequelae pose a grave concern for the post-COVID-19 pandemic era. Based on our discovery that the glycosaminoglycan dermatan sulfate (DS) displays peculiar affinity to apoptotic cells and autoantigens (autoAgs) and that DS-autoAg complexes cooperatively stimulate autoreactive B1 cell responses, we compiled a database of 751 candidate autoAgs from six human cell types. At least 657 of these have been found to be affected by SARS-CoV-2 infection based on currently available multi-omic COVID data, and at least 400 are confirmed targets of autoantibodies in a wide array of autoimmune diseases and cancer. The autoantigen-ome is significantly associated with various processes in viral infections, such as translation, protein processing, and vesicle transport. Interestingly, the coding genes of autoAgs predominantly contain multiple exons with many possible alternative splicing variants, short transcripts, and short UTR lengths. These observations and the finding that numerous autoAgs involved in RNA-splicing showed altered expression in viral infections suggest that viruses exploit alternative splicing to reprogram host cell machinery to ensure viral replication and survival. While each cell type gives rise to a unique pool of autoAgs, 39 common autoAgs associated with cell stress and apoptosis were identified from all six cell types, with several being known markers of systemic autoimmune diseases. In particular, the common autoAg UBA1 that catalyzes the first step in ubiquitination is encoded by an X-chromosome escape gene. Given its essential function in apoptotic cell clearance and that X-inactivation escape tends to increase with aging, UBA1 dysfunction can therefore predispose aging women to autoimmune disorders. In summary, we propose a model of how viral infections lead to extensive molecular alterations and host cell death, autoimmune responses facilitated by autoAg-DS complexes, and ultimately autoimmune diseases. Overall, this master autoantigen-ome provides a molecular guide for investigating the myriad of autoimmune sequalae to COVID-19 and clues to the rare adverse effects of the currently available mRNA and viral vector-based COVID vaccines.

Discovery of Autoantibodies Targeting Nephrin in Minimal Change Disease Supports a Novel Autoimmune Etiology.

Failure of the glomerular filtration barrier, primarily by loss of slit diaphragm architecture, underlies nephrotic syndrome in minimal change disease. The etiology remains unknown. The efficacy of B cell-targeted therapies in some patients, together with the known proteinuric effect of anti-nephrin antibodies in rodent models, prompted us to hypothesize that nephrin autoantibodies may be present in patients with minimal change disease. We evaluated sera from patients with minimal change disease, enrolled in the Nephrotic Syndrome Study Network (NEPTUNE) cohort and from our own institutions, for circulating nephrin autoantibodies by indirect ELISA and by immunoprecipitation of full-length nephrin from human glomerular extract or a recombinant purified extracellular domain of human nephrin. We also evaluated renal biopsies from our institutions for podocyte-associated punctate IgG colocalizing with nephrin by immunofluorescence. In two independent patient cohorts, we identified circulating nephrin autoantibodies during active disease that were significantly reduced or absent during treatment response in a subset of patients with minimal change disease. We correlated the presence of these autoantibodies with podocyte-associated punctate IgG in renal biopsies from our institutions. We also identified a patient with steroid-dependent childhood minimal change disease that progressed to end stage kidney disease; she developed a massive post-transplant recurrence of proteinuria that was associated with high pretransplant circulating nephrin autoantibodies. Our discovery of nephrin autoantibodies in a subset of adults and children with minimal change disease aligns with published animal studies and provides further support for an autoimmune etiology. We propose a new molecular classification of nephrin autoantibody minimal change disease to serve as a framework for instigation of precision therapeutics for these patients.

Endogenous Levels of Gamma Amino-Butyric Acid Are Correlated to Glutamic-Acid Decarboxylase Antibody Levels in Type 1 Diabetes.

Gamma-aminobutyric acid (GABA) is an important inhibitory neurotransmitter in the central nervous system (CNS) and outside of the CNS, found in the highest concentrations in immune cells and pancreatic beta-cells. GABA is gaining increasing interest in diabetes research due to its immune-modulatory and beta-cell stimulatory effects and is a highly interesting drug candidate for the treatment of type 1 diabetes (T1D). GABA is synthesized from glutamate by glutamic acid decarboxylase (GAD), one of the targets for autoantibodies linked to T1D. Using mass spectrometry, we have quantified the endogenous circulating levels of GABA in patients with new-onset and long-standing T1D and found that the levels are unaltered when compared to healthy controls, i.e., T1D patients do not have a deficit of systemic GABA levels. In T1D, GABA levels were negatively correlated with IL-1 beta, IL-12, and IL-15 15 and positively correlated to levels of IL-36 beta and IL-37. Interestingly, GABA levels were also correlated to the levels of GAD-autoantibodies. The unaltered levels of GABA in T1D patients suggest that the GABA secretion from beta-cells only has a minor impact on the circulating systemic levels. However, the local levels of GABA could be altered within pancreatic islets in the presence of GAD-autoantibodies.

Antiphospholipid antibodies in patients with myocardial infarction with and without obstructive coronary arteries.

Recent studies demonstrate that prothrombotic antiphospholipid antibodies (aPL) are overrepresented in patients with myocardial infarction (MI) due to coronary artery disease (MICAD). However, it is not known whether aPL differ between the two subsets of MI: MICAD and MI with nonobstructive coronary arteries (MINOCA). To determine whether aPL are associated with MINOCA or MICAD, or with hypercoagulability as assessed by activated protein C-protein C inhibitor (APC-PCI) complex. Well-characterized patients with MINOCA (n = 98), age- and gender-matched patients with MICAD (n = 99), and healthy controls (n = 100) were included in a cross-sectional case-control study. Autoantibodies (IgA/G/M) targeting cardiolipin and β2 glycoprotein-I and specific nuclear antigens were analyzed by multiplexed bead technology. The concentration of APC-PCI was determined as a measure of hypercoagulability by an immunofluorometric sandwich assay. Both prevalence and titers of aPL of the IgG isotype (anti-cardiolipin and/or anti-β2 glycoprotein-I) were higher in patients with MINOCA and MICAD than in controls. aPL IgG positivity was twice as frequent among patients with MICAD than MINOCA (11% vs. 6%, nonsignificant). We observed no group differences regarding aPL IgA/M or antibodies targeting specific nuclear antigens. Levels of APC-PCI were elevated in aPL IgG-positive compared to aPL IgG-negative MICAD patients. aPL IgG, but not IgA/M, are enriched particularly in patients with MICAD but also in patients with MINOCA, as compared to controls. Interestingly, signs of hypercoagulability-measured by increased levels of the APC-PCI complex-were present in aPL IgG-positive MICAD patients, indicating an association with functional disturbances of the coagulation system.

The major histocompatibility complex: new insights from old molecules into the pathogenesis of autoimmunity.

The major histocompatibility complex (MHC) is a central molecule in the immune system. The MHC is also a highly polymorphic gene that is the most strongly involved in susceptibility to many autoimmune diseases. Therefore, the elucidation of the mechanism by which specific MHC alleles are involved in autoimmune disease susceptibility is important to our understanding of the pathogenesis of autoimmune diseases. Specific autoantibody production is observed in many autoimmune diseases, but the mechanism underlying their production remains unclear. We have found that MHC class II molecules exhibit a chaperone-like function to transport misfolded proteins in the endoplasmic reticulum to the outside of cells. Furthermore, misfolded proteins transported to the cell surface by MHC class II molecules of autoimmune disease risk alleles are major autoantibody targets. In this article, I propose a novel mechanism underlying autoimmune diseases mediated by misfolded proteins complexed with MHC class II molecules.

TRIM21/Ro52 - Roles in Innate Immunity and Autoimmune Disease.

TRIM21 (Ro52/SSA1) is an E3 ubiquitin ligase with key roles in immune host defence, signal transduction, and possibly cell cycle regulation. It is also an autoantibody target in Sjögren’s syndrome, systemic lupus erythematosus, and other rheumatic autoimmune diseases. Here, we summarise the structure and function of this enzyme, its roles in innate immunity, adaptive immunity and cellular homeostasis, the pathogenesis of autoimmunity against TRIM21, and the potential impacts of autoantibodies to this intracellular protein.

Laminin-521 is a Novel Target of Autoantibodies Associated with Lung Hemorrhage in Anti-GBM Disease.

Antiglomerular basement membrane (anti-GBM) disease is characterized by GN and often pulmonary hemorrhage, mediated by autoantibodies that typically recognize cryptic epitopes within α345(IV) collagen-a major component of the glomerular and alveolar basement membranes. Laminin-521 is another major GBM component and a proven target of pathogenic antibodies mediating GN in animal models. Whether laminin-521 is a target of autoimmunity in human anti-GBM disease is not yet known. A retrospective study of circulating autoantibodies from 101 patients with anti-GBM/Goodpasture's disease and 85 controls used a solid-phase immunoassay to measure IgG binding to human recombinant laminin-521 with native-like structure and activity. Circulating IgG autoantibodies binding to laminin-521 were found in about one third of patients with anti-GBM antibody GN, but were not detected in healthy controls or in patients with other glomerular diseases. Autoreactivity toward laminin-521 was significantly more common in patients with anti-GBM GN and lung hemorrhage, compared with those with kidney-limited disease (51.5% versus 23.5%, P=0.005). Antilaminin-521 autoantibodies were predominantly of IgG1 and IgG4 subclasses and significantly associated with lung hemorrhage (P=0.005), hemoptysis (P=0.008), and smoking (P=0.01), although not with proteinuria or serum creatinine at diagnosis. Besides α345(IV) collagen, laminin-521 is another major autoantigen targeted in anti-GBM disease. Autoantibodies to laminin-521 may have the potential to promote lung injury in anti-GBM disease by increasing the total amount of IgG bound to the alveolar basement membranes.

Antibody-Mediated Autoimmune Diseases of the CNS: Challenges and Approaches to Diagnosis and Management.

Antibody-mediated disorders of the central nervous system (CNS) are increasingly recognized as neurologic disorders that can be severe and even life-threatening but with the potential for reversibility with appropriate treatment. The expanding spectrum of newly identified autoantibodies targeting glial or neuronal (neural) antigens and associated clinical syndromes (ranging from autoimmune encephalitis to CNS demyelination) has increased diagnostic precision, and allowed critical reinterpretation of non-specific neurological syndromes historically associated with systemic disorders (e.g., Hashimoto encephalopathy). The intracellular vs. cell-surface or synaptic location of the different neural autoantibody targets often helps to predict the clinical characteristics, potential cancer association, and treatment response of the associated syndromes. In particular, autoantibodies targeting intracellular antigens (traditionally termed onconeural autoantibodies) are often associated with cancers, rarely respond well to immunosuppression and have a poor outcome, although exceptions exist. Detection of neural autoantibodies with accurate laboratory assays in patients with compatible clinical-MRI phenotypes allows a definite diagnosis of antibody-mediated CNS disorders, with important therapeutic and prognostic implications. Antibody-mediated CNS disorders are rare, and reliable autoantibody identification is highly dependent on the technique used for detection and pre-test probability. As a consequence, indiscriminate neural autoantibody testing among patients with more common neurologic disorders (e.g., epilepsy, dementia) will necessarily increase the risk of false positivity, so that recognition of high-risk clinical-MRI phenotypes is crucial. A number of emerging clinical settings have recently been recognized to favor development of CNS autoimmunity. These include antibody-mediated CNS disorders following herpes simplex virus encephalitis or occurring in a post-transplant setting, and neurological autoimmunity triggered by TNFα inhibitors or immune checkpoint inhibitors for cancer treatment. Awareness of the range of clinical and radiological manifestations associated with different neural autoantibodies, and the specific settings where autoimmune CNS disorders may occur is crucial to allow rapid diagnosis and early initiation of treatment.

Evolving Mechanisms in the Pathophysiology of Pemphigus Vulgaris: A Review Emphasizing the Role of Desmoglein 3 in Regulating p53 and the Yes-Associated Protein

The immunobullous condition Pemphigus Vulgaris (PV) is caused by autoantibodies targeting the adhesion proteins of desmosomes, leading to blistering in the skin and mucosal membrane. There is still no cure to the disease apart from the use of corticosteroids and immunosuppressive agents. Despite numerous investigations, the pathological mechanisms of PV are still incompletely understood, though the etiology is thought to be multifactorial. Thus, further understanding of the molecular basis underlying this disease process is vital to develop targeted therapies. Ample studies have highlighted the role of Desmoglein-3 (DSG3) in the initiation of disease as DSG3 serves as a primary target of PV autoantibodies. DSG3 is a pivotal player in mediating outside-in signaling involved in cell junction remodeling, cell proliferation, differentiation, migration or apoptosis, thus validating its biological function in tissue integrity and homeostasis beyond desmosome adhesion. Recent studies have uncovered new activities of DSG3 in regulating p53 and the yes-associated protein (YAP), with the evidence of dysregulation of these pathways demonstrated in PV. The purpose of this review is to summarize the earlier and recent advances highlighting our recent findings related to PV pathogenesis that may pave the way for future research to develop novel specific therapies in curing this disease.

Small Angle X-Ray Scattering Reveals the Conformation of β2glycoprotein I and the Conformational Binding Epitopes of Autoantibodies

Despite the fact that autoantibodies to a variety of antigens have been described in patients with the antiphospholipid syndrome (APS), it is now generally accepted that β2glycoprotein I (β2GPI) is a primary target of pathogenic autoantibodies in APS patients. Unraveling the immunodominant epitope of β2GPI at the molecular/conformational level may help to understand the disease and develop specific therapies. β2GPI is an abundant plasma protein that, upon interaction with negative phospholipids, has been shown to undergo a conformational change resulting in the exposure of a pathogenic epitope on domain I. Although the conformation of β2GPI has been previously reported by small angle X-ray scattering (SAXS), we are the first to show the interaction with autoimmune anti-β2GPI antibodies. We previously showed that antibodies towards the cryptic domain I epitope are highly associated with both thrombosis and pregnancy morbidity. Previous studies indicated that amino acids R39-R43 and the interlinking region between domains I and II are part of this cryptic epitope. However, these studies used point-mutated variants of β2GPI, and the results could be influenced by structural changes compared to native β2GPI.In this study, we visualized the conformation of β2GPI in solution by SAXS and its interaction with two anti-domain I antibodies, obtained via B cell isolation from two APS patients. Antibody P2-6 previously showed affinity for domain I regardless of the conformation of β2GPI, whereas antibody P1-117 only recognized domain I of β2GPI upon binding to anionic phospholipids. Via point-mutated variants of β2GPI we previously demonstrated that P1-117 is reactive against the cryptic domain I epitope including epitope G40-R43. In a first set of SAXS experiments, we visualized plasma purified β2GPI in its native conformation. We found that, due to the flexibility of domain I-III of β2GPI, β2GPI is able to adapt into several different conformations ranging from a sort of circular shape into a S shape, confirming results of previous studies. Upon increasing the pH, the conformation of β2GPI changed into a more erect fish-hook conformation resembling the crystal structure of β2GPI. The three-dimensional structures of both antibodies were determined by SAXS and allowed to react with β2GPI in the open conformation (Figure 1). Antibody P2-6 interacted mainly with the amino terminal end of domain I of β2GPI which is available in both the native and open conformations of β2GPI. In contrast, antibody P1-117 interacted with a broader part of the protein, identifying a discontinuous and conformational epitope covering domain I, the interlinking region and a small part of domain II. Importantly, (part of) the epitope is not available in the native closed conformation of β2GPI due to its interaction with domain V (circular conformation) or due to a carbohydrate chain positioned on the interface of domain I-II (S shaped conformation). These data confirm the importance of the conformation of β2GPI coated on the solid phase of diagnostic anti-β2GPI assays to avoid false negative classification of APS patients.In conclusion, our findings contribute to elucidating the conformation of β2GPI in solution and clearly indicate that pathogenic autoantibodies bind a discontinuous conformational epitope. Identification of this conformational epitope will allow optimization of peptide-based therapies and also epitope-specific diagnostic assays that will enable the stratification of patients according to their risk on thrombosis/pregnancy morbidity. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

The GAR/RGG motif defines a family of nuclear alarmins

The nucleus is the target of autoantibodies in many diseases, which suggests intrinsic nuclear adjuvants that confer its high autoimmunogenicity. Nucleolin (NCL) is one abundant nucleolar autoantigen in systemic lupus erythematosus (SLE) patients and, in lupus-prone mice, it elicits autoantibodies early. With purified NCL, we observed that it was a potent alarmin that activated monocytes, macrophages and dendritic cells and it was a ligand for TLR2 and TLR4. NCL released by necrotic cells also exhibited alarmin activity. The NCL alarmin activity resides in its glycine/arginine-rich (GAR/RGG) motif and can be displayed by synthetic GAR/RGG peptides. Two more GAR/RGG-containing nucleolar proteins, fibrillarin (FBRL) and GAR1, were also confirmed to be novel alarmins. Therefore, the GAR/RGG alarmin motif predicts a family of nucleolar alarmins. The apparent prevalence of nucleolar alarmins suggests their positive contribution to tissue homeostasis by inducing self-limiting tissue inflammation with autoimmunity only occurring when surveillance is broken down.

Diverse Functional Autoantibodies that Underlie Immune Perturbations in COVID-19

Abstract Infection with SARS-CoV-2 results in a broad spectrum of immunological and clinical outcomes for patients with COVID-19. While dysregulated innate immunity has been extensively explored in severe disease, autoantibody responses and their impact on disease trajectories remain uncharted. Here, we enrolled a cohort of 194 SARS-CoV-2 infected patients and uninfected individuals, and employed a high-throughput autoantibody discovery platform, Rapid Extracellular Antigen Profiling (REAP), to assess the prevalence of autoantibodies against 2,770 extracellular and secreted proteins in COVID-19 disease. We found that COVID-19 patients harbor dramatically expanded autoantibody repertoires compared to uninfected controls. We further established that immunomodulatory proteins including cytokines, chemokines, complements, and cell surface receptors, are frequent targets of autoantibodies. Longitudinal analysis revealed the existence of both pre-existing autoantibodies, as well as a broad subset of autoantibodies induced upon SARS-CoV-2 infection. We uncovered distinct mechanisms by which immune-targeting autoantibodies perturb immunological functions, including interference of immunoreceptor signaling, depletion of circulating leukocytes, and modulation of antiviral antibody responses. Concordantly, murine surrogates of these autoantibodies hinder immune activation and exacerbate disease severity in a mouse model of SARS-CoV-2 infection. In summary, through the lens of an unbiased proteome-scale survey for autoantibody targets, these findings implicate humoral immunopathology as an integral aspect of COVID-19 pathogenesis with diverse impacts on immune functionality and clinical outcomes.

An autoantigen profile of human A549 lung cells reveals viral and host etiologic molecular attributes of autoimmunity in COVID-19

We aim to establish a comprehensive COVID-19 autoantigen atlas in order to understand autoimmune diseases caused by SARS-CoV-2 infection. Based on the unique affinity between dermatan sulfate and autoantigens, we identified 348 proteins from human lung A549 cells, of which 198 are known targets of autoantibodies. Comparison with current COVID data identified 291 proteins that are altered at protein or transcript level in SARS-CoV-2 infection, with 191 being known autoantigens. These known and putative autoantigens are significantly associated with viral replication and trafficking processes, including gene expression, ribonucleoprotein biogenesis, mRNA metabolism, translation, vesicle and vesicle-mediated transport, and apoptosis. They are also associated with cytoskeleton, platelet degranulation, IL-12 signaling, and smooth muscle contraction. Host proteins that interact with and that are perturbed by viral proteins are a major source of autoantigens. Orf3 induces the largest number of protein alterations, Orf9 affects the mitochondrial ribosome, and they and E, M, N, and Nsp proteins affect protein localization to membrane, immune responses, and apoptosis. Phosphorylation and ubiquitination alterations by viral infection define major molecular changes in autoantigen origination. This study provides a large list of autoantigens as well as new targets for future investigation, e.g., UBA1, UCHL1, USP7, CDK11A, PRKDC, PLD3, PSAT1, RAB1A, SLC2A1, platelet activating factor acetylhydrolase, and mitochondrial ribosomal proteins. This study illustrates how viral infection can modify host cellular proteins extensively, yield diverse autoantigens, and trigger a myriad of autoimmune sequelae. Our work provides a rich resource for studies into “long COVID” and related autoimmune sequelae.

Autoantibodies Against the Purkinje Cell Protein RGS8 in Paraneoplastic Cerebellar Syndrome

ObjectiveTo describe the identification of regulator of G-protein signaling 8 (RGS8) as an autoantibody target in patients with cerebellar syndrome associated with lymphoma.MethodsSera of 4 patients with a very similar unclassified reactivity against cerebellar Purkinje cells were used in antigen identification experiments. Immunoprecipitations with cerebellar lysates followed by mass spectrometry identified the autoantigen, which was verified by recombinant immunofluorescence assay, immunoblot, and ELISA with the recombinant protein.ResultsThe sera and CSF of 4 patients stained the Purkinje cells and molecular layer of the cerebellum. RGS8 was identified as the target antigen in all 4 sera. In a neutralization experiment, recombinant human RGS8 was able to neutralize the autoantibodies' tissue reaction. Patient sera and CSF showed a specific reactivity against recombinant RGS8 in ELISA and immunoblot, whereas no such reactivity was detectable in the controls. Clinical data were available for 2 of the 4 patients, remarkably both presented with cerebellar syndrome accompanied by B-cell lymphoma of the stomach (patient 1, 53 years) or Hodgkin lymphoma (patient 2, 74 years).ConclusionOur results indicate that autoantibodies against the intracellular Purkinje cell protein RGS8 represent new markers for paraneoplastic cerebellar syndrome associated with lymphoma.Classification of EvidenceThis study provided Class IV evidence that autoantibodies against the intracellular Purkinje cell protein RGS8 are associated with paraneoplastic cerebellar syndrome in lymphoma.

Neutrophil Extracellular Traps: A Potential Therapeutic Target in MPO-ANCA Associated Vasculitis?

Our understanding of immune recognition and response to infection and non-infectious forms of cell damage and death is rapidly increasing. The major focus is on host immunity and microbiological invasion. However, it is also clear that these same pathways are important in the initiation and maintenance of autoimmunity and the damage caused to targeted organs. Understanding the involvement of cell death in autoimmune disease is likely to help define critical pathways in the immunopathogenesis of autoimmune disease and new therapeutic targets. An important immune responder cell population in host defense and autoimmunity is the neutrophil. One autoimmune disease where neutrophils play important roles is MPO-ANCA Microscopic Vasculitis. This a severe disease that results from inflammation to small blood vessels in the kidney, the glomeruli (high blood flow and pressure filters). One of the best studied ways in which neutrophils participate in this disease is by cell death through NETosis resulting in the discharge of proinflammatory enzymes and nuclear fragments. In host defense against infection this process helps neutralize pathogens however in auto immunity NETosis results in injury and death to the surrounding healthy tissues. The major autoimmune target in this disease is myeloperoxidase (MPO) which is found uniquely in the cytoplasm of neutrophils. Although the kidney is the major organ targeted in this disease MPO is not expressed in the kidney. Autoantibodies target surface MPO on activated circulating neutrophils resulting in their lodgment in glomerular capillaries where they NETose releasing extracellularly MPO and nuclear fragments initiating injury and planting the key autoantigen MPO. It is the cell death of neutrophils that changes the kidney from innocent bystander to major autoimmune target. Defining the immunopathogenesis of this autoimmune disease and recognizing critical injurious pathways will allow therapeutic intervention to block these pathways and attenuate autoimmune injury. The insights (regarding mechanisms of injury and potential therapeutic targets) are likely to be highly relevant to many other autoimmune diseases.

Autoantibodies Targeting Intracellular and Extracellular Proteins in Autoimmunity.

Detecting autoantibodies provides foundational information for the diagnosis of most autoimmune diseases. An important pathophysiological distinction is whether autoantibodies are directed against extracellular or intracellular proteins. Autoantibodies targeting extracellular domains of proteins, such as membrane receptors, channels or secreted molecules are often directly pathogenic, whereby autoantibody binding to the autoantigen disrupts the normal function of a critical protein or pathway, and/or triggers antibody-dependent cell surface complement killing. By comparison, autoantibodies directed against intracellular proteins are recognized as useful diagnostic biomarkers of abnormal autoimmune activity, but the link between antigenicity and pathogenicity is less straightforward. Because intracellular autoantigens are generally inaccessible to autoantibody binding, for the most part, they do not directly contribute to pathogenesis. In a few diseases, autoantibodies to intracellular targets cause damage indirectly by immune complex formation, immune activation, and other processes. In this review, the general features of and differences between autoimmune diseases segregated on the basis of intracellular or extracellular autoantigens are explored using over twenty examples. Expression profiles of autoantigens in relation to the tissues targeted by autoimmune disease and the temporal appearance of autoantibodies before clinical diagnosis often correlate with whether the respective autoantibodies mostly recognize either intracellular or extracellular autoantigens. In addition, current therapeutic strategies are discussed from this vantage point. One drug, rituximab, depletes CD20+ B-cells and is highly effective for autoimmune disorders associated with autoantibodies against extracellular autoantigens. In contrast, diseases associated with autoantibodies directed predominately against intracellular autoantigens show much more complex immune cell involvement, such as T-cell mediated tissue damage, and require different strategies for optimal therapeutic benefit. Understanding the clinical ramifications of autoimmunity derived by autoantibodies against either intracellular or extracellular autoantigens, or a spectrum of both, has practical implications for guiding drug development, generating monitoring tools, stratification of patient interventions, and designing trials based on predictive autoantibody profiles for autoimmune diseases.

Case of Linagliptin-Induced Bullous Pemphigoid

Bullous pemphigoid is an autoimmune subepidermal blistering condition in which autoantibodies target components of the hemidesmosomal proteins. It typically presents as pruritic bullous lesions in a generalized distribution. Certain drugs such as diuretics, NSAIDs, antibiotics, and ACE inhibitors have been implicated in the development of bullous pemphigoid. Recently, a class of medications for type II diabetes, dipeptidyl peptidase-4 (DPP-4) inhibitors (commonly called gliptins) have been implicated in drug-induced bullous pemphigoid. We report a case of a 73-year-old female with type II diabetes mellitus who presented with biopsy-proven bullous pemphigoid after being treated with linagliptin. After discontinuing linagliptin and receiving first-line treatment, the patient achieved remission by her five-week follow-up. It is imperative that dermatologists and primary care physicians remain aware of this association when diagnosing and treating bullous pemphigoid, particularly in diabetic patients.

Characterization of Beta-2-Glycoprotein I Domain V interaction with Plasma Membrane

Beta-2-Glycoprotein I (β2GPI), also known as apolipoprotein H, is a 48kDa protein which circulates in blood at a high concentration [0.2 mg/ml]. β2GPI is the main target of autoantibodies in antiphospholipid syndrome (APS) which results in thrombosis and/or recurrent miscarriage. Therefore, investigating membrane binding mechanism of β2GPI is important to elucidate how this protein become immunogenic upon binding to plasma membrane and to help target specific drug development for APS. It is known that β2GPI binds to anionic phospholipids in the plasma membrane via its positively charged domain V (DV) but the mechanism of binding is still elusive. in this study, we performed multiple 500-ns molecular dynamics simulations of β2GPI-DV in the presence of membranes containing PC and PS in varying compositions employing the HMMM (highly mobile membrane mimetic) model. We observed stable membrane binding in eight out of ten replicas. Our results show that in seven out of eight replicas, β2GPI-DV interacts with the membrane via its flexible loop (311-317) which insert into the membrane below the PO4 level. interestingly, in one replica we observe insertion of the loop carrying three lysine residues, a mode which closely corresponds to an alternative binding mode reported previously. The orientation of membrane-bound states was characterized by measuring the tilt angle between the protein and the membrane. After insertion of the flexible loop, β2GPI-DV held an average tilt angle of 92 with respect to the membrane normal. This study establishes the significance of the flexible loop for membrane binding of β2GPI which could lead to a more rational approach in drug design for treatment of APS.

Detection of Complement Factor B Autoantibodies by ELISA.

Antibodies to autoantigens are implicated in a large number of diseases. Such autoantibodies may cause pathological activation of complement, an ancient humoral recognition and effector system of innate immunity; in addition, complement components or regulators may be target of autoantibodies and cause abnormal complement activation or function. Autoantibodies to complement proteins are in particular involved in kidney diseases. Those binding to complement convertase enzymes can cause enhanced stability of convertases and their increased resistance to regulation, thus promoting complement turnover. Here, we describe an ELISA method to detect factor B autoantibodies that bind to and stabilize the alternative complement pathway C3 convertase enzyme, C3bBb.

Acute severe autoimmune hepatitis with anti-rods and rings autoantibodies; literature first evidence.

Autoimmune hepatitis (AIH) was defined as a progressive, chronic inflammatory autoimmune liver disease (ALD). The diagnosis of AIH requires the presence of characteristic clinical and laboratory features, and the exclusion of other clinical conditions that cause chronic hepatitis and cirrhosis. AIH can have an acute onset that mimics an acute viral or toxic hepatitis or an acute severe (fulminant, ASF) presentation that satisfies criteria for acute liver. Guidelines from the European Association for the Study of Liver Diseases define ALF with absence of pre-existing liver disease, acute onset of ≤ 26 weeks, coagulopathy (international normalised ratio (INR) ≥ 1.5), and presence of hepatic encephalopathy (HE). In recent years, autoantibodies (Aab) targeting subcellular structures described as the rods and rings (R&R) pattern in HEp-2 ANA have been presented as a unique and particular case of Aab generation. These R&R structures are composed of inosine monophosphate dehydrogenase type 2 (IMPDH2), and their formation can be induced in vitro by several small-molecule inhibitors. Aab targeting these relatively unknown structures has been observed in Hepatitis C virus (HCV) patients who have undergone treatment with pegylated interferona/ ribavirin (IFN/RBV) therapy. We presented and characterized a case patient with R&R and SMA Aab in AIH (ASF, fatal, without liver transplantation). To the best of our knowledge, this is the first evidence described in the Literature. Our early experience showed the R&R circulating Aab in one patient with Primary Biliary Cholangitis. This work now demonstrates that R&R Aab can also be present in AIH case.