Autoantigens as Partners in Initiation and Propagation of Autoimmune Rheumatic Diseases.

Systemic autoimmune diseases are characterized by specific targeting of a limited group of ubiquitously expressed autoantigens by the immune system. This review examines the mechanisms underlying their selection as immune targets. Initiation of autoimmune responses likely reflects the presentation of antigens with a distinct structure not previously encountered by the immune system, in a proimmune context (injury, malignancy, or infection). Causes of modified structure include somatic mutation and posttranslational modifications (including citrullination and proteolysis). Many autoantigens are components of multimolecular complexes, and some of the other components may provide adjuvant activity. Propagation of autoimmune responses appears to reflect a bidirectional interaction between the immune response and the target tissues in a mutually reinforcing cycle: Immune effector pathways generate additional autoantigen, which feeds further immune response. We propose that this resonance may be a critical principle underlying disease propagation, with specific autoantigens functioning as the hubs around which amplification occurs.

Cumulative disease damage and anti-PM/Scl antibodies are associated with a heavy burden of calcinosis in systemic sclerosis.

OBJECTIVES: Ectopic calcification (calcinosis) is a common complication of SSc, but a subset of SSc patients has a heavy burden of calcinosis. We examined whether there are unique risk factors for a heavy burden of calcinosis, as compared with a light burden or no calcinosis. METHODS: We reviewed the medical records of all patients in the Johns Hopkins Scleroderma Center Research Registry with calcinosis to quantify calcinosis burden using pre-specified definitions. We performed latent class analysis to identify SSc phenotypic classes. We used multinomial logistic regression to determine whether latent phenotypic classes and autoantibodies were independent risk factors for calcinosis burden. RESULTS: Of all patients, 29.4% (997/3388) had calcinosis, and 13.5% (130/963) of those with calcinosis had a heavy burden. The latent phenotypic class with predominantly diffuse skin disease and higher disease severity (characterized by pulmonary hypertension, interstitial lung disease, cardiomyopathy, severe RP, gastrointestinal involvement, renal crisis, myopathy and/or tendon friction rubs) was associated with an increased risk of both a heavy burden [odds ratio (OR) 6.92, 95% CI 3.66, 13.08; P < 0.001] and a light burden (OR 2.88, 95% CI 2.11, 3.95; P < 0.001) of calcinosis compared with the phenotypic class with predominantly limited skin disease. Autoantibodies to PM/Scl were strongly associated with a heavy burden of calcinosis (OR 17.31, 95% CI 7.72, 38.81; P < 0.001) and to a lesser degree a light burden of calcinosis (OR 3.59, 95% CI 1.84, 7.00; P < 0.001). CONCLUSIONS: Calcinosis burden is associated with cumulative SSc-related tissue damage. Independent of disease severity, autoantibodies to PM/Scl are also associated with a heavy burden of calcinosis.

Granzyme B Induces IRF-3 Phosphorylation through a Perforin-Independent Proteolysis-Dependent Signaling Cascade without Inducing Cell Death.

Granzyme B (GrB) is an immune protease implicated in the pathogenesis of several human diseases. In the current model of GrB activity, perforin determines whether the downstream actions of GrB occur intracellularly or extracellularly, producing apoptotic cytotoxicity or nonapoptotic effects, respectively. In the current study, we demonstrate the existence of a broad range of GrB-dependent signaling activities that 1) do not require perforin, 2) occur intracellularly, and 3) for which cell death is not the dominant outcome. In the absence of perforin, we show that GrB enzymatic activity still induces substoichiometric activation of caspases, which through nonlethal DNA damage response signals then leads to activity-associated phosphorylation of IFN regulatory factor-3. These findings illustrate an unexpected potential interface between GrB and innate immunity separate from the traditional role of GrB in perforin-dependent GrB-mediated apoptosis that could have mechanistic implications for human disease.

Learning and Predicting from Dynamic Models for COVID-19 Patient Monitoring.

COVID-19 has challenged health systems to learn how to learn. This paper describes the context, methods and challenges for learning to improve COVID-19 care at one academic health center. Challenges to learning include: (1) choosing a right clinical target; (2) designing methods for accurate predictions by borrowing strength from prior patients' experiences; (3) communicating the methodology to clinicians so they understand and trust it; (4) communicating the predictions to the patient at the moment of clinical decision; and (5) continuously evaluating and revising the methods so they adapt to changing patients and clinical demands. To illustrate these challenges, this paper contrasts two statistical modeling approaches - prospective longitudinal models in common use and retrospective analogues complementary in the COVID-19 context - for predicting future biomarker trajectories and major clinical events. The methods are applied to and validated on a cohort of 1,678 patients who were hospitalized with COVID-19 during the early months of the pandemic. We emphasize graphical tools to promote physician learning and inform clinical decision making.

Autoantibodies targeting LINE-1-encoded ORF1p are associated with systemic lupus erythematosus diagnosis but not disease activity.

OBJECTIVES: Long Interspersed Element 1 (LINE-1) is an endogenous retroelement that constitutes a significant portion of the human genome and has been implicated in the pathogenesis of systemic lupus erythematosus (SLE). The LINE-1 RNA chaperone protein ORF1p was recently identified as an SLE autoantigen. Here we analyse ORF1p for qualities underlying SLE autoantigen status, compared anti-ORF1p antibodies to markers of SLE disease activity, and performed screening for antibodies against LINE-1 reverse transcriptase ORF2p. METHODS: ORF1p was examined in epithelial cell lines treated with cytotoxic lymphocyte granules and UV irradiation. Anti-ORF1p and anti-ORF2p antibodies were assayed by ELISA and analysed in two SLE cohorts. RESULTS: We found that ORF1p localises to cytoplasmic RNA-containing blebs in apoptotic cells, and is a substrate of the cytotoxic protease granzyme B (GrB). Anti-ORF1p antibodies were present in 4.2% of healthy controls, compared to 15.8% (p=0.0157) and 15.5% (p=0.036) of subjects in the two SLE cohorts. Anti-ORF1p antibodies were not associated with SLE disease activity nor peripheral blood markers of interferon (IFN) activation. Anti-ORF1p titres demonstrated stability over serial time points. Anti-ORF1p antibodies were not associated with anti-DNA, anti-RNP, or other SLE autoantibodies. There was no difference in anti-ORF2p ELISA results in controls versus SLE patients. CONCLUSIONS: LINE-1 ORF1p is a component of apoptotic blebs and a substrate for GrB. Anti-ORF1p antibodies are enriched in SLE subjects but are not associated with dynamic markers of disease activity. These data support a potential role for LINE-1 dysregulation in SLE pathogenesis.

IMMUNOEDITING IN AUTOIMMUNE RHEUMATIC DISEASES.

The striking association of specific autoantibodies with distinct disease phenotypes and trajectories in human autoimmune rheumatic diseases provides a powerful opportunity to interrogate disease mechanism. In scleroderma, a subgroup of patients with autoantibodies to POLR3 have coincident onset of cancer and scleroderma. The majority of these patients have genetic changes (somatic mutations and loss of heterozygosity) in the POLR3A gene in their matched cancers, coupled with immune responses directed against the mutated and wild type autoantigen. In some individuals with scleroderma or dermatomyositis where specific immune responses mark a high risk of emergent cancer, cancer does not emerge. Such patients have a broader immune response that targets additional autoantigens, suggesting that the breadth and magnitude of the immune response regulates cancer, and that the rheumatic diseases provide a unique window into natural immunoediting of cancer in humans. This has implications for prediction and therapy in both autoimmunity and cancer.

Patient Trajectories Among Persons Hospitalized for COVID-19 : A Cohort Study.

BACKGROUND: Risk factors for progression of coronavirus disease 2019 (COVID-19) to severe disease or death are underexplored in U.S. cohorts. OBJECTIVE: To determine the factors on hospital admission that are predictive of severe disease or death from COVID-19. DESIGN: Retrospective cohort analysis. SETTING: Five hospitals in the Maryland and Washington, DC, area. PATIENTS: 832 consecutive COVID-19 admissions from 4 March to 24 April 2020, with follow-up through 27 June 2020. MEASUREMENTS: Patient trajectories and outcomes, categorized by using the World Health Organization COVID-19 disease severity scale. Primary outcomes were death and a composite of severe disease or death. RESULTS: Median patient age was 64 years (range, 1 to 108 years); 47% were women, 40% were Black, 16% were Latinx, and 21% were nursing home residents. Among all patients, 131 (16%) died and 694 (83%) were discharged (523 [63%] had mild to moderate disease and 171 [20%] had severe disease). Of deaths, 66 (50%) were nursing home residents. Of 787 patients admitted with mild to moderate disease, 302 (38%) progressed to severe disease or death: 181 (60%) by day 2 and 238 (79%) by day 4. Patients had markedly different probabilities of disease progression on the basis of age, nursing home residence, comorbid conditions, obesity, respiratory symptoms, respiratory rate, fever, absolute lymphocyte count, hypoalbuminemia, troponin level, and C-reactive protein level and the interactions among these factors. Using only factors present on admission, a model to predict in-hospital disease progression had an area under the curve of 0.85, 0.79, and 0.79 at days 2, 4, and 7, respectively. LIMITATION: The study was done in a single health care system. CONCLUSION: A combination of demographic and clinical variables is strongly associated with severe COVID-19 disease or death and their early onset. The COVID-19 Inpatient Risk Calculator (CIRC), using factors present on admission, can inform clinical and resource allocation decisions. PRIMARY FUNDING SOURCE: Hopkins inHealth and COVID-19 Administrative Supplement for the HHS Region 3 Treatment Center from the Office of the Assistant Secretary for Preparedness and Response.

Autoantibodies targeting telomere-associated proteins in systemic sclerosis.

OBJECTIVES: Systemic sclerosis (SSc) is an autoimmune fibrotic disease affecting multiple tissues including the lung. A subset of patients with SSc with lung disease exhibit short telomeres in circulating lymphocytes, but the mechanisms underlying this observation are unclear. METHODS: Sera from the Johns Hopkins and University of California, San Francisco (UCSF) Scleroderma Centers were screened for autoantibodies targeting telomerase and the shelterin proteins using immunoprecipitation and ELISA. We determined the relationship between autoantibodies targeting the shelterin protein TERF1 and telomere length in peripheral leucocytes measured by qPCR and flow cytometry and fluorescent in situ hybridisation (Flow-FISH). We also explored clinical associations of these autoantibodies. RESULTS: In a subset of patients with SSc, we identified autoantibodies targeting telomerase and the shelterin proteins that were rarely present in rheumatoid arthritis, myositis and healthy controls. TERF1 autoantibodies were present in 40/442 (9.0%) patients with SSc and were associated with severe lung disease (OR 2.4, p=0.04, Fisher's exact test) and short lymphocyte telomere length. 6/6 (100%) patients with TERF1 autoantibodies in the Hopkins cohort and 14/18 (78%) patients in the UCSF cohort had a shorter telomere length in lymphocytes or leukocytes, respectively, relative to the expected age-adjusted telomere length. TERF1 autoantibodies were present in 11/152 (7.2%) patients with idiopathic pulmonary fibrosis (IPF), a fibrotic lung disease believed to be mediated by telomere dysfunction. CONCLUSIONS: Autoantibodies targeting telomere-associated proteins in a subset of patients with SSc are associated with short lymphocyte telomere length and lung disease. The specificity of these autoantibodies for SSc and IPF suggests that telomere dysfunction may have a distinct role in the pathogenesis of SSc and pulmonary fibrosis.

A Bayesian approach to restricted latent class models for scientifically structured clustering of multivariate binary outcomes.

This paper presents a model-based method for clustering multivariate binary observations that incorporates constraints consistent with the scientific context. The approach is motivated by the precision medicine problem of identifying autoimmune disease patient subsets or classes who may require different treatments. We start with a family of restricted latent class models or RLCMs. However, in the motivating example and many others like it, the unknown number of classes and the definition of classes using binary states are among the targets of inference. We use a Bayesian approach to RLCMs in order to use informative prior assumptions on the number and definitions of latent classes to be consistent with scientific knowledge so that the posterior distribution tends to concentrate on smaller numbers of clusters and sparser binary patterns. The paper derives a posterior sampling algorithm based on Markov chain Monte Carlo with split-merge updates to efficiently explore the space of clustering allocations. Through simulations under the assumed model and realistic deviations from it, we demonstrate greater interpretability of results and superior finite-sample clustering performance for our method compared to common alternatives. The methods are illustrated with an analysis of protein data to detect clusters representing autoantibody classes among scleroderma patients.

Estimating autoantibody signatures to detect autoimmune disease patient subsets.

Autoimmune diseases are characterized by highly specific immune responses against molecules in self-tissues. Different autoimmune diseases are characterized by distinct immune responses, making autoantibodies useful for diagnosis and prediction. In many diseases, the targets of autoantibodies are incompletely defined. Although the technologies for autoantibody discovery have advanced dramatically over the past decade, each of these techniques generates hundreds of possibilities, which are onerous and expensive to validate. We set out to establish a method to greatly simplify autoantibody discovery, using a pre-filtering step to define subgroups with similar specificities based on migration of radiolabeled, immunoprecipitated proteins on sodium dodecyl sulfate (SDS) gels and autoradiography [Gel Electrophoresis and band detection on Autoradiograms (GEA)]. Human recognition of patterns is not optimal when the patterns are complex or scattered across many samples. Multiple sources of errors-including irrelevant intensity differences and warping of gels-have challenged automation of pattern discovery from autoradiograms.In this article, we address these limitations using a Bayesian hierarchical model with shrinkage priors for pattern alignment and spatial dewarping. The Bayesian model combines information from multiple gel sets and corrects spatial warping for coherent estimation of autoantibody signatures defined by presence or absence of a grid of landmark proteins. We show the pre-processing creates more clearly separated clusters and improves the accuracy of autoantibody subset detection via hierarchical clustering. Finally, we demonstrate the utility of the proposed methods with GEA data from scleroderma patients.

Systematic autoantigen analysis identifies a distinct subtype of scleroderma with coincident cancer.

Scleroderma is a chronic autoimmune rheumatic disease associated with widespread tissue fibrosis and vasculopathy. Approximately two-thirds of all patients with scleroderma present with three dominant autoantibody subsets. Here, we used a pair of complementary high-throughput methods for antibody epitope discovery to examine patients with scleroderma with or without known autoantibody specificities. We identified a specificity for the minor spliceosome complex containing RNA Binding Region (RNP1, RNA recognition motif) Containing 3 (RNPC3) that is found in patients with scleroderma without known specificities and is absent in unrelated autoimmune diseases. We found strong evidence for both intra- and intermolecular epitope spreading in patients with RNA polymerase III (POLR3) and the minor spliceosome specificities. Our results demonstrate the utility of these technologies in rapidly identifying antibodies that can serve as biomarkers of disease subsets in the evolving precision medicine era.

Autoantibodies and scleroderma phenotype define subgroups at high-risk and low-risk for cancer.

OBJECTIVES: Recent studies demonstrate autoantibodies are powerful tools to interrogate molecular events linking cancer and the development of autoimmunity in scleroderma. Investigating cancer risk in these biologically relevant subsets may provide an opportunity to develop personalised cancer screening guidelines. In this study, we examined cancer risk in distinct serologic and phenotypic scleroderma subsets and compared estimates with the general population. METHODS: Patients in the Johns Hopkins Scleroderma Center observational cohort were studied. Overall and site-specific cancer incidence was calculated in distinct autoantibody and scleroderma phenotypic subsets, and compared with the Surveillance, Epidemiology and End Results registry, a representative sample of the US population. RESULTS: 2383 patients with scleroderma contributing 37 686 person-years were studied. 205 patients (8.6%) had a diagnosis of cancer. Within 3 years of scleroderma onset, cancer risk was increased in patients with RNA polymerase III autoantibodies (antipol; standardised incidence ratio (SIR) 2.84, 95% CI 1.89 to 4.10) and those lacking centromere, topoisomerase-1 and pol antibodies (SIR 1.83, 95% CI 1.10 to 2.86). Among antipol-positive patients, cancer-specific risk may vary by scleroderma subtype; those with diffuse scleroderma had an increased breast cancer risk, whereas those with limited scleroderma had high lung cancer risk. In contrast, patients with anticentromere antibodies had a lower risk of cancer during follow-up (SIR 0.59, 95% CI 0.44 to 0.76). CONCLUSIONS: Autoantibody specificity and disease subtype are biologically meaningful filters that may inform cancer risk stratification in patients with scleroderma. Future research testing the value of targeted cancer screening strategies in patients with scleroderma is needed.

Affinity maturation shapes the function of agonistic antibodies to peptidylarginine deiminase type 4 in rheumatoid arthritis.

OBJECTIVES: The citrullinating enzyme peptidylarginine deiminase type 4 (PAD4) is the target of a polyclonal group of autoantibodies in patients with rheumatoid arthritis (RA). A subgroup of such antibodies, initially identified by cross-reactivity with peptidylarginine deiminase type 3 (PAD3), is strongly associated with progression of radiographic joint damage and interstitial lung disease and has the unique ability to activate PAD4. The features of these antibodies in terms of their T cell-dependent origin, genetic characteristics and effect of individual antibody specificities on PAD4 function remain to be defined. METHODS: We used PAD4 tagged with the monomeric fluorescent protein mWasabi to isolate PAD4-specific memory B cells from anti-PAD4 positive patients with RA and applied single cell cloning technologies to obtain monoclonal antibodies. RESULTS: Among 44 single B cells, we cloned five antibodies with PAD4-activating properties. Sequence analysis, germline reversion experiments and antigen specificity assays suggested that autoantibodies to PAD4 are not polyreactive and arise from PAD4-reactive precursors. Somatic mutations increase the agonistic activity of these antibodies at low calcium concentrations by facilitating their interaction with structural epitopes that modulate calcium-binding site 5 in PAD4. CONCLUSIONS: PAD4-activating antibodies directly amplify a key process in disease pathogenesis, making them unique among other autoantibodies in RA. Understanding the molecular basis for their functionality may inform the design of future PAD4 inhibitors.

Proteolysis by Granzyme B Enhances Presentation of Autoantigenic Peptidylarginine Deiminase 4 Epitopes in Rheumatoid Arthritis.

Proteolysis of autoantigens can alter normal MHC class II antigen processing and has been implicated in the induction of autoimmune diseases. Many autoantigens are substrates for the protease granzyme B (GrB), but the mechanistic significance of this association is unknown. Peptidylarginine deiminase 4 (PAD4) is a frequent target of autoantibodies in patients with rheumatoid arthritis (RA) and a substrate for GrB. RA is strongly associated with specific MHC class II alleles, and elevated levels of GrB and PAD4 are found in the joints of RA patients, suggesting that GrB may alter the presentation of PAD4 by RA-associated class II alleles. In this study, complementary proteomic and immunologic approaches were utilized to define the effects of GrB cleavage on the structure, processing, and immunogenicity of PAD4. Hydrogen-deuterium exchange and a cell-free MHC class II antigen processing system revealed that proteolysis of PAD4 by GrB induced discrete structural changes in PAD4 that promoted enhanced presentation of several immunogenic peptides capable of stimulating PAD4-specific CD4+ T cells from patients with RA. This work demonstrates the existence of PAD4-specific T cells in patients with RA and supports a mechanistic role for GrB in enhancing the presentation of autoantigenic CD4+ T cell epitopes.

Evaluation of cancer-associated myositis and scleroderma autoantibodies in breast cancer patients without rheumatic disease.

OBJECTIVES: Systemic sclerosis (scleroderma) and dermatomyositis are two prototypic autoimmune diseases that are strongly associated with malignancy. While specific autoantibodies in these diseases are markers of an increased risk of cancer at scleroderma and dermatomyositis onset, it is not known whether these autoantibodies are biomarkers of cancer risk in patients without rheumatic disease. METHODS: In a matched case-control study of women without rheumatic disease, identified from a familial breast cancer cohort, 50 breast cancer cases and 50 controls were assayed for 3 autoantibodies that are known markers of cancer-associated scleroderma and dermatomyositis: anti-RNA polymerase III, anti-NXP2, and anti-TIF1γ. RESULTS: No subject had moderate or strong autoantibody positivity. Eleven women were borderline positive for at least one autoantibody. The prevalence of borderline autoantibody positivity did not differ between cases and controls. CONCLUSIONS: Our results suggest that scleroderma and dermatomyositis autoantibodies are cancer biomarkers only in patients with clinical manifestations of specific rheumatic diseases and are unlikely to improve risk stratification for cancer in the general population. However, prospective studies are needed to examine whether scleroderma and dermatomyositis autoantibodies are markers of malignancy in other cancer types.

PUF60: a prominent new target of the autoimmune response in dermatomyositis and Sjögren's syndrome.

OBJECTIVES: Autoantibodies are used clinically to phenotype and subset patients with autoimmune rheumatic diseases. We detected a novel 60 kDa autoantibody specificity by immunoblotting using a dermatomyositis (DM) patient's serum. Our objective was to identify the targeted autoantigen and to evaluate disease specificity and clinical significance of this new autoantibody. METHODS: A new 60 kDa specificity was detected by immunoblotting HeLa cell lysates. The targeted autoantigen was identified as poly(U)-binding-splicing factor 60 kDa (PUF60) using (i) a human protein array and (ii) two-dimensional gel electrophoresis and liquid chromatography tandem mass spectrometry peptide sequencing. Anti-PUF60 antibodies were assayed by ELISA using sera from patients with primary Sjögren's syndrome (SS; n=84), systemic lupus erythematosus (SLE; n=71), DM (n=267), polymyositis (n=45), inclusion body myositis (n=45) and healthy controls (n=38). RESULTS: PUF60 was identified as a new autoantigen. Anti-PUF60 antibodies were present in 25/84 (30%) patients with SS, 6/71 (8.5%) patients with SLE and 2/38 (5.0%) control subjects (SS vs controls, p=0.002; SLE vs controls, p=0.711). Anti-PUF60 antibodies were present in 48/267 (18.0%) patients with DM versus 4/45 (8.9%) and 5/45 (11.1%) patients with inclusion body myositis and polymyositis, respectively. The antibody was significantly associated with anti-Ro52 antibodies, rheumatoid factor and hyperglobulinemia in the patients with primary SS. In patients with DM, the antibody was associated with anti-transcription intermediary factor 1 gamma seropositivity and Caucasian race. CONCLUSIONS: PUF60 represents a novel autoantigen in patients with SS and DM. PUF60 antibodies are associated with distinct clinical features and different immune responses in different diseases.

A methodology for exploring biomarker--phenotype associations: application to flow cytometry data and systemic sclerosis clinical manifestations.

BACKGROUND: This work seeks to develop a methodology for identifying reliable biomarkers of disease activity, progression and outcome through the identification of significant associations between high-throughput flow cytometry (FC) data and interstitial lung disease (ILD) - a systemic sclerosis (SSc, or scleroderma) clinical phenotype which is the leading cause of morbidity and mortality in SSc. A specific aim of the work involves developing a clinically useful screening tool that could yield accurate assessments of disease state such as the risk or presence of SSc-ILD, the activity of lung involvement and the likelihood to respond to therapeutic intervention. Ultimately this instrument could facilitate a refined stratification of SSc patients into clinically relevant subsets at the time of diagnosis and subsequently during the course of the disease and thus help in preventing bad outcomes from disease progression or unnecessary treatment side effects. The methods utilized in the work involve: (1) clinical and peripheral blood flow cytometry data (Immune Response In Scleroderma, IRIS) from consented patients followed at the Johns Hopkins Scleroderma Center. (2) machine learning (Conditional Random Forests - CRF) coupled with Gene Set Enrichment Analysis (GSEA) to identify subsets of FC variables that are highly effective in classifying ILD patients; and (3) stochastic simulation to design, train and validate ILD risk screening tools. RESULTS: Our hybrid analysis approach (CRF-GSEA) proved successful in predicting SSc patient ILD status with a high degree of success (>82% correct classification in validation; 79 patients in the training data set, 40 patients in the validation data set). CONCLUSIONS: IRIS flow cytometry data provides useful information in assessing the ILD status of SSc patients. Our new approach combining Conditional Random Forests and Gene Set Enrichment Analysis was successful in identifying a subset of flow cytometry variables to create a screening tool that proved effective in correctly identifying ILD patients in the training and validation data sets. From a somewhat broader perspective, the identification of subsets of flow cytometry variables that exhibit coordinated movement (i.e., multi-variable up or down regulation) may lead to insights into possible effector pathways and thereby improve the state of knowledge of systemic sclerosis pathogenesis.

Precise probes of type II interferon activity define the origin of interferon signatures in target tissues in rheumatic diseases.

Elucidating the molecular pathways active in pathologic tissues has important implications for defining disease subsets, selecting therapy, and monitoring disease activity. The development of therapeutics directed at IFN-α or IFN-γ makes the discovery of probes that report precisely on the activity of different IFN pathways a high priority. We show that, although type I and II IFNs induce the expression of a largely overlapping group of molecules, precise probes of IFN-γ activity can be defined. Used in combination, these probes show prominent IFN-γ effects in Sjögren syndrome (SS) tissues. In contrast, dermatomyositis muscle shows a dominant type I IFN pattern. Interestingly, heterogeneity of IFN signatures exists in patients with SS, with some patients demonstrating a predominant type I pattern. The biochemical patterns largely distinguish the target tissues in patients with SS from those with dermatomyositis and provide a relative weighting of the effects of distinct IFN pathways in specific biopsies. In SS, type I and II IFN effects are localized to the same epithelial cells, surrounded by inflammatory cells expressing IFN-γ-induced proteins, suggesting reinforcing interactions. Precise probes of the different IFN pathways active in tissues of complex rheumatic diseases will be critical to classify disease, elucidate pathogenesis, and select therapy.

Most patients with cancer-associated dermatomyositis have antibodies to nuclear matrix protein NXP-2 or transcription intermediary factor 1γ.

OBJECTIVE: Since dermatomyositis (DM) is associated with an increased risk of malignancy, accurate identification of patients likely to harbor cancers is important. Using immunoprecipitations from radiolabeled cell lysates, several groups recently showed that anti-transcription intermediary factor 1γ (anti-TIF-1γ) antibodies are associated with malignancy in DM. We undertook this study to develop sensitive, specific assays to detect antibodies against TIF-1γ and nuclear matrix protein NXP-2 and to evaluate their association with malignancy in DM. METHODS: To detect anti-TIF-1γ antibodies, immunoprecipitations were performed using lysates made from HeLa cells overexpressing TIF-1γ, with detection by immunoblotting. Anti-NXP-2 antibodies were assayed by immunoprecipitation using (35) S-methionine-labeled NXP-2 generated by in vitro transcription/translation. We analyzed patient sera from DM cohorts seen at the Stanford University Dermatology Clinic (n = 111) and the Johns Hopkins Myositis Center (n = 102). RESULTS: A total of 17% and 38% of patients had antibodies against NXP-2 and TIF-1γ, respectively. Reactivity against either NXP-2 or TIF-1γ identified 83% of patients with cancer-associated DM. In addition to older age and male sex, cancer was associated with antibodies to NXP-2 or TIF-1γ on multivariate analysis (odds ratio 3.78 [95% confidence interval 1.33-10.8]). Stratification by sex revealed that anti-NXP-2 was specifically associated with cancer in males (odds ratio 5.78 [95% confidence interval 1.35-24.7]). CONCLUSION: These studies demonstrate that anti-NXP-2 and anti-TIF-1γ antibodies are frequent DM specificities (found in 55% of patients) and are present in most patients with cancer-associated DM.

Anti-Gephyrin Antibodies: A Novel Specificity in Patients With Systemic Sclerosis and Lower Bowel Dysfunction.

OBJECTIVE: Autoantibodies are clinically useful in phenotyping patients with systemic sclerosis (SSc). Gastrointestinal (GI) function is regulated by the enteric nervous system (ENS) and commonly impaired in SSc, suggesting that the SSc autoimmune response may target ENS antigens. We sought to identify novel anti-ENS autoantibodies with an aim to clinically phenotype SSc GI dysfunction. METHODS: Serum from a patient with SSc with GI dysfunction but without defined SSc-associated autoantibodies was used for autoantibody discovery. Immunoprecipitations performed with murine myenteric plexus lysates were on-bead digested, and autoantigens were identified by mass spectrometry. Prevalence was determined, and clinical features associated with novel autoantibodies were evaluated in a SSc cohort using regression analyses. The expression of gephyrin in human GI tract tissue was examined by immunohistochemistry. RESULTS: We identified gephyrin as a novel SSc autoantigen. Anti-gephyrin antibodies were present in 9% of patients with SSc (16/188) and absent in healthy controls (0/46). Anti-gephyrin antibody-positive patients had higher constipation scores (1.00 vs 0.50, P = 0.02) and were more likely to have severe constipation and severe distention/bloating (46% vs 15%, P = 0.005; 54% vs 25%, P = 0.023, respectively). Anti-gephyrin antibody levels were significantly higher among patients with severe constipation (0.04 vs 0.00; P = 0.001) and severe distention and bloating (0.03 vs 0.004; P = 0.010). Severe constipation was associated with anti-gephyrin antibodies even in the adjusted model. Importantly, gephyrin was expressed in the ENS, which regulates gut motility. CONCLUSION: Gephyrin is a novel ENS autoantigen that is expressed in human myenteric ganglia. Anti-gephyrin autoantibodies are associated with the presence and severity of constipation in patients with SSc.