Helena Enocsson

The soluble urokinase plasminogen activator receptor (suPAR) has been shown to adequately predict the risk of organ damage development in patients with systemic lupus erythematosus (SLE). However, the cellular source and mechanism of increased circulating levels remain unknown. The cell-bound uPAR is expressed on various cell types and can be shed from the plasma membrane surface by proteases, resulting in the soluble form, suPAR. Herein, leukocyte uPAR expression and plasma suPAR levels were explored in unstimulated and cytokine-treated (tumor necrosis factor; TNF or interferon-α; IFN-α) blood from patients with SLE ( n = 37) and healthy blood donors (HBD; n = 27). Unstimulated or cytokine-treated whole blood was thereafter used for analysis of cellular uPAR expression by flow cytometry, and plasma suPAR levels by enzyme-linked immunosorbent assay (ELISA). Monocytes and neutrophils had the most prominent uPAR expression and showed increased expression after TNF addition to the blood ( p < 0.001). Addition of IFN-α resulted in increased uPAR expression only in patients ( p < 0.05). No differences in uPAR expression were found depending on organ damage or other clinical variables. Nevertheless, suPAR levels were higher in patients with organ damage ( p < 0.01). Unstimulated suPAR levels were correlated with monocyte uPAR expression in patient samples (rho = 0.4). As circulating suPAR levels can predict organ damage development in SLE, it is important to unravel its potential disease mediating effects as well as cellular sources. Results of this study suggest IFN-α as a regulator of uPAR expression in SLE and monocyte uPAR as an important source of plasma suPAR.

Objective: Systemic inflammatory autoimmune diseases (SIADs) such as systemic lupus erythematosus (SLE), primary Sjögren disease (pSS), and idiopathic inflammatory myopathies (myositis) are complex conditions characterized by shared circulating autoantibodies and clinical manifestations, including skin rashes, among others. This study was aimed at elucidating the genetics underlying these common features.Methods: We performed targeted DNA sequencing of coding and regulatory regions from approximately 1,900 immune‐related genes in a large cohort of 2,292 well‐characterized Scandinavian patients with SIADs with SLE, pSS, and myositis as well as 1,252 controls. A gene‐based functionally weighted genetic score for aggregate testing of all genetic variants, including rare variants, was complemented by in silico functional analyses and in vitro reporter experiments.Results: Case–control association analysis detected known and potentially novel genetic loci in agreement with previous genetic and transcriptomics findings linked to the SIAD autoimmune background. Intriguingly, case–case comparisons between patient subgroups with and without specific autoantibodies revealed that the subgroups defined by antinuclear antibodies and anti–double‐stranded DNA antibodies have unique genetic profiles reflecting their heterogeneity. When focusing on clinical features, we overall showed that dual‐specificity phosphatase 1 (DUSP1) protective genetic variants lead to increased gene expression and potentially to anti‐inflammatory effects on the SIAD‐associated skin phenotype. This is consistent with recent genetic findings on eczema and with the previously reported down‐regulation of the MAPK signaling‐related gene DUSP1 in other skin disorders.Conclusion: Together, this suggests common molecular mechanisms potentially underlying overlapping clinical manifestations shared among different disorders and informs clinical heterogeneity, which could be translated to improve disease diagnostic and treatment, also in more generalized disease frameworks.

Editorial: Autoantibodies for Diagnostics, Prognostics, andBreach of tolerance to self-antigens and serological autoimmunity, reportedly occurs long before onset of clinical autoimmune disease (1). Still, circulating disease-specific autoantibodies remain a hallmark of B-cell driven autoimmune disease although they may also be detected in healthy individuals and transiently in patients with infections. Over the years associations between specific autoantibodies and clinical disease have improved our understanding of mechanisms in autoimmunity as well as clinical diagnostics (2,3).Lack of immune tolerance and increased production of antibodies directed against self-antigens may induce or precipitate autoimmune disease as clearly demonstrated for the TSH receptor antibodies in Graves' disease. Beyond that, autoantibodies may represent an epiphenomenon in autoimmune disease without distinct pathophysiologic relevance; this is exemplified by smooth muscle antibodies (SMA) in autoimmune hepatitis (AIH). However, most autoimmune diseases, e.g., systemic lupus erythematosus (SLE), idiopathic inflammatory myopathies (IIM) and Sjögren's disease (SjD) are characterized by mixtures of autoantibodies with varying degrees of pathogenic potential. They can help physicians to make a correct diagnosis or to predict the severity of the disease or the response to treatments. In addition, "new" autoantibodies with clinical relevance are constantly discovered and new areas of application for "old" autoantibodies are emerging (4).The Research Topic "Autoantibodies for Diagnostics, Prognostics, and Surveillance in Autoimmune Disease" collected original works, review articles and case reports offering new insights on clinical applications of new and established autoantibodies in autoimmune diseases. The clinical use of autoantibodies has the potential to facilitate early diagnosis, informed selection of patients for targeted and personalized therapies which in turn can be expected to improve long-term outcomes for patients with autoimmune diseases. Furthermore, the discovery of (new) autoantibodies and their autoantigens may give clues to disease mechanisms and reveal new areas of research. We hereby summarize the final content of the Research Topic which covers a variety of autoimmune diseases and autoantibodies.In a single center study by Marklund et al. the presence of myositis-specific autoantibodies (MSA) and myositis associated autoantibodies (MAA) were examined in relation to lung involvement in patients with myositis. Patients presenting with MAA, particularly anti-SSA/Ro52 antibodies were found to be at higher risk of developing interstitial lung disease (ILD). Interestingly, it was also noticed that patients presenting only with antibodies against Mi-2α, Mi-2β, NXP2, HMGCR, and TIF1γ, or no MSA/MAA, were all spared from ILD.Zhang et al. contributed a case report describing a patient with anti-MDA5 positive amyopathic dermatomyositis, also positive for anti-SSA/Ro52. This patient, who suffered from rapidly progressive ILD was successfully treated with methylprednisolone pulses combined with cyclosporine A and hydroxychloroquine.In a review, Antiochos and Casciola-Rosen thoughtfully described the autoantigens associated with the interferon (IFN) system. They included the type I IFN induced autoantigen SSA/Ro52, as well as MDA-5, a cytoplasmic dsRNA sensor that promote type I IFN production. The authors also describe autoantibodies against IFN types I, II and III themselves, and linked them to autoimmune diseases and immunodeficiencies.A cross-sectional study by Sciascia et al. investigated autoantibodies recognizing high density lipoprotein (HDL) in antiphospholipid syndrome (APS). Patients with APS showed higher levels of anti-HDL when compared to healthy controls; the highest levels were found among patients with arterial, as compared to venous thrombosis, even when adjusting for total IgG. The results suggest that whether anti-HDL autoantibodies could serve a biomarker for thrombotic events in APS deserve further studies.Andraos and colleagues assessed a large collection of sera from healthy blood donors (n=825) for ANA using both HEp-2 cells and ALBIA. A considerable proportion of the sera contained autoantibodies, though without any clear association to self-reported symptoms. Importantly, the combination of ANA fine-specificities, relevant symptoms and high IFN-α levels identified a small proportion of blood donors with autoimmune disease (two cases with SjD). In a case-control study by Liu et al., the presence, titer and pattern of antinuclear antibodies (ANA) among patients with newly diagnosed rheumatoid arthritis (RA) were investigated. ANA positivity, especially at high titers and homogenous staining pattern on Hep-2 cells, was associated with a higher probability of RA when compared with healthy individuals and non-RA subjects with arthritis.Another study, by Martinsson et al., examined the relation between a periodontitis pathogen (Aggregatibacter actinomycetemcomitans; A.a.) and the development of RA in at-risk RA patients from two cohorts. Leukotoxin A (LtxA) is expressed by A.a. and has the indirect ability of citrullination, thereby providing a possible route for an increased load of citrullinated antigens. These may induce anti-citrullinated protein antibodies (ACPA), a hallmark of RA. An association between anti-LtxA antibodies with disease progression to RA was found in one of the two cohorts, but not in the other. The authors suggest that there might be population-dependent differences in the oral microbiome and the risk to develop RA, which should be further explored in future studies.A review article by Wang et al. covered the area of Chinese herbal medicine and the beneficial effects of various herbs and herbal compounds in the treatment of RA. A structured overview of these compounds, their biological targets and potential mechanism of action were...

The detection of antinuclear antibodies is central to the diagnosis and prognosis of systemic lupus erythematosus (SLE), primary Sjögren’s syndrome (pSS) and mixed connective tissue disease (MCTD). Anti-U1-RNP and anti-RNP70 antibodies were assayed in the sera of patients with SLE (n = 114), pSS (n = 54) and MCTD (n = 12). In the SLE group, 34/114 (30%) were anti-U1-RNP positive, and 21/114 (18%) were both anti-RNP70 positive and anti-U1-RNP positive. In the MCTD group, 10/12 (83%) were anti-U1-RNP positive, and 9/12 (75%) were anti-RNP70 positive. Only one individual with pSS was antibody positive (for both anti-U1-RNP and anti-RNP70). All anti-RNP70-positive samples were also anti-U1-RNP positive. Anti-U1-RNP-positive subjects with SLE were younger (p < 0.0001); showed lower concentrations of complement protein 3 (p = 0.03); had lower eosinophil (p = 0.0005), lymphocyte (p = 0.006) and monocyte (p = 0.03) counts; and had accrued less organ damage (p = 0.006) than the anti-U1-RNP-negative SLE patients. However, we observed no significant clinical or laboratory parameter differences between the anti-U1-RNP-positive individuals with/without anti-RNP70 in the SLE group. In conclusion, anti-RNP70 antibodies are not exclusive to MCTD but are rarely detected in pSS and healthy individuals. In SLE, anti-U1-RNP antibodies are associated with a clinical phenotype that resembles MCTD, with hematologic involvement and less damage accrual. Based on our results, the clinical value of subtyping anti-RNP70 in anti-U1-RNP-positive sera appears to be of limited value.

Patients with systemic lupus erythematosus (SLE) are at an increased risk of cardiovascular disease. We aimed to evaluate whether antibodies to oxidized low-density lipoprotein (anti-oxLDL) were associated with subclinical atherosclerosis in patients with different SLE phenotypes (lupus nephritis, antiphospholipid syndrome, and skin and joint involvement). Anti-oxLDL was measured by enzyme-linked immunosorbent assay in 60 patients with SLE, 60 healthy controls (HCs) and 30 subjects with anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV). Intima-media thickness (IMT) assessment of vessel walls and plaque occurrence were recorded using high-frequency ultrasound. In the SLE cohort, anti-oxLDL was again assessed in 57 of the 60 individuals approximately 3 years later. The levels of anti-oxLDL in the SLE group (median 5829 U/mL) were not significantly different from those in the HCs group (median 4568 U/mL), while patients with AAV showed significantly higher levels (median 7817 U/mL). The levels did not differ between the SLE subgroups. A significant correlation was found with IMT in the common femoral artery in the SLE cohort, but no association with plaque occurrence was observed. The levels of anti-oxLDL antibodies in the SLE group were significantly higher at inclusion compared to 3 years later (median 5707 versus 1503 U/mL, p < 0.0001). Overall, we found no convincing support for strong associations between vascular affection and anti-oxLDL antibodies in SLE.

C-reactive protein (CRP) is well-known as a sensitive albeit unspecific biomarker of inflammation. In most rheumatic conditions, the level of this evolutionarily highly conserved pattern recognition molecule conveys reliable information regarding the degree of ongoing inflammation, driven mainly by interleukin-6. However, the underlying causes of increased CRP levels are numerous, including both infections and malignancies. In addition, low to moderate increases in CRP predict subsequent cardiovascular events, often occurring years later, in patients with angina and in healthy individuals. However, autoimmune diseases characterized by the Type I interferon gene signature (e.g., systemic lupus erythematosus, primary Sjögren’s syndrome and inflammatory myopathies) represent exceptions to the general rule that the concentrations of CRP correlate with the extent and severity of inflammation. In fact, adequate levels of CRP can be beneficial in autoimmune conditions, in that they contribute to efficient clearance of cell remnants and immune complexes through complement activation/modulation, opsonization and phagocytosis. Furthermore, emerging data indicate that CRP constitutes an autoantigen in systemic lupus erythematosus. At the same time, the increased risks of cardiovascular and cerebrovascular diseases in patients diagnosed with systemic lupus erythematosus and rheumatoid arthritis are well-established, with significant impacts on quality of life, accrual of organ damage, and premature mortality. This review describes CRP-mediated biological effects and the regulation of CRP release in relation to aspects of cardiovascular disease and mechanisms of autoimmunity, with particular focus on systemic lupus erythematosus.

Objectives: Type I interferons (IFNs) are central and reflective of disease activity in systemic lupus erythematosus (SLE). However, IFN-α levels are notoriously difficult to measure and the type I IFN gene signature (IGS) is not yet available in clinical routine. This study evaluates galectin-9 and an array of chemokines/cytokines in their potential as surrogate markers of type I IFN and/or SLE disease activity.Methods: Healthy controls and well-characterized Swedish SLE patients from two cross-sectional cohorts (n=181; n=59) were included, and a subgroup (n=21) was longitudinally followed. Chemokine/cytokine responses in immune complex triggered IFN-α activity was studied in healthy donor peripheral blood mononuclear cells (PBMC). Levels of chemokines/cytokines and galectin-9 were measured by immunoassays. Gene expression was quantified by qPCR.Results: The IGS was significantly (p<0.01) correlated with galectin-9 (rho=0.54) and CXCL10 (rho=0.37) levels whereas serum IFN-α correlated with galectin-9 (rho=0.36), CXCL10 (rho=0.39), CCL19 (rho=0.26) and CCL2 (rho=0.19). The strongest correlation was observed between galectin-9 and TNF (rho=0.56). IFN-α and disease activity (SLEDAI-2K) were correlated (rho=0.20) at cross-sectional analysis, but no significant associations were found between SLEDAI-2K and galectin-9 or chemokines. Several inflammatory mediators increased at disease exacerbation although CCL19, CXCL11, CXCL10, IL-10 and IL-1 receptor antagonist were most pronounced. Immune complex-stimulation of PBMC increased the production of CCL2, CXCL8 and TNF.Conclusion: Galectin-9 and CXCL10 were associated with type I IFN in SLE but correlated stronger with TNF. None of the investigated biomarkers showed a convincing association with disease activity, although CXCL10 and CCL19 performed best in this regard.

Objectives: Patients with systemic lupus erythematosus (SLE) often display modest elevations of C-reactive protein (CRP) despite raised disease activity and increased interleukin (IL-) 6. We asked to what extent IL-6 levels, the CRP polymorphism rs1205, and the type I interferon (IFN) gene signature affects the basal CRP levels in patients with SLE during a quiescent phase of the disease.Methods: CRP and IL-6 were analyzed in plasma from 57 patients meeting established classification criteria for SLE. The CRP polymorphism rs1205 was assessed and gene expression analyzed including four type I IFN-regulated genes (IGS).Results: CRP was increased in patients with detectable IL-6 levels (p=0.001) and decreased among IGS-positive subjects (p=0.033). A multiple linear regression model revealed IL-6 to have a positive association with CRP levels, whereas both IGS-positivity and CRP genotype (rs1205) AA/GA were negatively associated with CRP-levels.Conclusion: Our data offer an explanation to the modest CRP levels seen in viral infections and IFN-α driven autoimmunity and corroborate prior observations showing an IFN-α dependent downregulation of CRP. The latter observation, together with the fact that the CRP-lowering polymorphism rs1205 is overrepresented in human SLE, could explain low basal CRP and inadequate CRP-responses among patients with active SLE.