Lupus nephritis: role of antinucleosome autoantibodies

The additional role of anti-nucleosome antibodies in the prediction of renal damage in systemic lupus erythematosus based on CSTAR (XXV)

OBJECTIVES

The predominant determinant of an unfavorable prognosis among Systemic Lupus Erythematosus (SLE) patients resides in the irreversible organ damage. This prospective cohort study aimed to identify the additional value of anti-nucleosome antibodies on organ damage accumulation in SLE patients.

METHODS

Based on the Chinese SLE Treatment and Research group (CSTAR) registry, demographic characteristics, autoantibodies profiles, and clinical manifestations were collected at baseline. Follow-up data were collected by reviewing clinical records.

RESULTS

Of 2481 SLE patients with full follow-up data, 663 (26.7%) were anti-nucleosome antibodies positive and 1668 (68.0%) were anti-dsDNA antibodies positive. 764 (30.8%) patients developed new organ damage during a mean follow-up of 4.31 ± 2.60 years. At baseline, patients with positive anti-nucleosome antibodies have a higher rate of lupus nephritis (50.7% vs 36.2%, p < .001). According to the multivariable Cox regression analysis, both anti-nucleosome (HR = 1.30, 95% CI, 1.09-1.54, p < .001) and anti-dsDNA antibodies (HR=1.68, 95% CI, 1.38-2.05, p < .001) were associated with organ damage accumulation. Anti-nucleosome (HR = 2.51, 95% CI, 1.81-3.46, p < .001) and anti-dsDNA antibodies (HR = 1.69, 95% CI, 1.39-2.06, p < .001) were independent predictors for renal damage. Furthermore, the combination of the two antibodies can provide more accurate information about renal damage in overall SLE patients (HR = 3.19, 95% CI, 2.49-4.10, p < .001) and patients with lupus nephritis at baseline (HR = 2.86, 95% CI, 2.29-3.57, p < .001).

CONCLUSION

Besides anti-dsDNA antibodies, anti-nucleosome antibodies can also provide information about organ damage accrual during follow-up. The ability of co-positivity of anti-nucleosome and anti-dsDNA antibodies in predicting renal damage may lead to additional benefits in the follow-up of these patients.

Precise Targeting of Autoantigen-Specific B Cells in Lupus Nephritis with Chimeric Autoantibody Receptor T Cells

Despite conventional therapy, lupus nephritis (LN) remains a significant contributor to short- and long-term morbidity and mortality. B cell abnormalities and the production of autoantibodies against nuclear complexes like anti-dsDNA are recognised as key players in the pathogenesis of LN. To address the challenges of chronic immunosuppression associated with current therapies, we have engineered T cells to express chimeric autoantibody receptors (DNA-CAART) for the precise targeting of B cells expressing anti-dsDNA autoantibodies. T cells from LN patients were transduced using six different CAAR vectors based on their antigen specificity, including alpha-actinin, histone-1, heparan sulphate, or C1q. The cytotoxicity, cytokine production, and cell-cell contact of DNA-CAART were thoroughly investigated in co-culture experiments with B cells isolated from patients, both with and without anti-dsDNA positivity. The therapeutic effects were further evaluated using an in vitro immune kidney LN organoid. Among the six proposed DNA-CAART, DNA4 and DNA6 demonstrated superior selectively cytotoxic activity against anti-dsDNA+ B cells. Notably, DNA4-CAART exhibited improvements in organoid morphology, apoptosis, and the inflammatory process in the presence of IFNα-stimulated anti-dsDNA+ B cells. Based on these findings, DNA4-CAART emerge as promising candidates for modulating autoimmunity and represent a novel approach for the treatment of LN.

Synbiotic regulates gut microbiota in patients with lupus nephritis: an analysis using metagenomic and metabolome sequencing

Objective

To investigate the changes in gut microbes and their metabolites after administering synbiotics to patients with new-onset lupus nephritis (LN) treated using a conventional method and provide a theoretical basis for finding new targets for the diagnosis and treatment of LN.

Methods

In this study, a total of 12 participants were divided into the lupus and synbiotic groups. Stool samples and clinical data were collected before and after treatment for metagenomic, nontargeted metabolomic, and statistical analyses.

Results

The relative abundances of the pathogenic bacteria Prevotella, Bacteroides, and Enterobacteriaceae_unclassified decreased after synbiotic treatment, whereas the abundances of Actinobacteria and Firmicutes increased. Further, the Firmicutes to Bacteroidetes ratio increased; however, the difference was not statistically significant (p > 0.05). α diversity analysis showed no significant differences in the intestinal microbial richness and diversity index of patients with LN between the groups before and after treatment (p > 0.05). β analysis showed the differences in the community structure between the samples of the two groups before and after treatment. Linear discriminant analysis effect size and receiver operating characteristic curve analyses revealed that Negativicutes (AUC = 0.9722) and Enterobacteriaceae_unclassified (AUC = 0.9722) were the best predictors of the lupus and synbiotic groups, respectively, before and after treatment. Joint analyses revealed that amino acid biosynthesis, aminoacyl-tRNA biosynthesis, purine metabolism, and other metabolic pathways may be involved in the changes in the metabolic function of patients with LN after the addition of synbiotics. Spearman's correlation analysis revealed the interaction between clinical features and flora, and flora exhibited a complex biological network regulatory relationship.

Conclusion

Synbiotics regulate the metabolic functions of intestinal microorganisms in patients with LN and play a role in various biological functions. Synbiotic supplements may be safe and promising candidates for patients with LN.

The greatest contribution to medical science is the transformation from studying symptoms to studying their causes-the unrelenting legacy of Robert Koch and Louis Pasteur-and a causality perspective to approach a definition of SLE

The basic initiative related to this study is derived from the fact that systemic lupus erythematosus (SLE) is a unique and fertile system science subject. We are, however, still far from understanding its nature. It may be fair to indicate that we are spending more time and resources on studying the complexity of classified SLE than studying the validity of classification criteria. This study represents a theoretical analysis of current instinctual SLE classification criteria based on "the causality principle." The discussion has its basis on the radical scientific traditions introduced by Robert Koch and Louis Pasteur. They announced significant changes in our thinking of disease etiology through the implementation of the modern version of "the causality principle." They influenced all aspects of today's medical concepts and research: the transformation of medical science from studies of symptoms to study their causes, relevant for monosymptomatic diseases as for syndromes. Their studies focused on bacteria as causes of infectious diseases and on how the immune system adapts to control and prevent contagious spreading. This is the most significant paradigm shift in the modern history of medicine and resulted in radical changes in our view of the immune system. They described acquired post-infection immunity and active immunization by antigen-specific vaccines. The paradigm "transformation" has a great theoretical impact also on current studies of autoimmune diseases like SLE: symptoms and their cause(s). In this study, the evolution of SLE classification and diagnostic criteria is discussed from "the causality principle" perspective, and if contemporary SLE classification criteria are as useful as believed today for SLE research. This skepticism is based on the fact that classification criteria are not selected based on cogent causal strategies. The SLE classification criteria do not harmonize with Koch's and Pasteur's causality principle paradigms and not with Witebsky's Koch-derived postulates for autoimmune and infectious diseases. It is not established whether the classification criteria can separate SLE as a "one disease entity" from "SLE-like non-SLE disorders"-the latter in terms of SLE imitations. This is discussed here in terms of weight, rank, and impact of the classification criteria: Do they all originate from "one basic causal etiology"? Probably not.

Autoantibodies in lupus nephritis useful in distinguishing proliferative nephritis from membranous nephritis

OBJECTIVES

This study was conducted to determine autoantibodies associated with lupus nephritis (LN), especially those useful in diagnosing proliferative and membranous nephritis.

METHODS

A total of 106 patients with LN and 63 patients with systemic lupus erythematosus but no nephritis were enrolled; then, 55 patients were selected from the LN group and were divided into two groups: proliferative nephritis patients (n = 36) and membranous nephritis patients (n = 19). The autoantibody profiles of patients' sera were evaluated using the EUROLINE ANA Profile 3 (IgG) kit.

RESULTS

A higher positivity rate of anti-double-stranded DNA antibody and anti-histone antibody was seen in LN patients compared to nonrenal systemic lupus erythematosus patients. In comparing between proliferative and membranous nephritis, the positivity of anti-nucleosome antibody was higher in proliferative nephritis, although it was not statistically significant. However, anti-nucleosome antibody-positive patients with LN had a higher prevalence of haematuria and pyuria, which are strong indications of proliferative nephritis. Also, a significantly higher positivity rate of anti-RNP70 antibody was seen in membranous nephritis compared to proliferative nephritis.

CONCLUSIONS

Our results showed that anti-nucleosome and anti-RNP70 antibodies may be predictive nonhistological factors for discriminating between proliferative and membranous LN.

Microparticles in Autoimmunity: Cause or Consequence of Disease?

Microparticles (MPs) are small (100 nm - 1 um) extracellular vesicles derived from the plasma membrane of dying or activated cells. MPs are important mediators of intercellular communication, transporting proteins, nucleic acids and lipids from the parent cell to other cells. MPs resemble the state of their parent cells and are easily accessible when released into the blood or urine. MPs also play a role in the pathogenesis of different diseases and are considered as potential biomarkers. MP isolation and characterization is technically challenging and results in different studies are contradictory. Therefore, uniform guidelines to isolate and characterize MPs should be developed. Our understanding of MP biology and how MPs play a role in different pathological mechanisms has greatly advanced in recent years. MPs, especially if derived from apoptotic cells, possess strong immunogenic properties due to the presence of modified proteins and nucleic acids. MPs are often found in patients with autoimmune diseases where MPs for example play a role in the break of immunological tolerance and/or induction of inflammatory conditions. In this review, we describe the main techniques to isolate and characterize MPs, define the characteristics of MPs generated during cell death, illustrate different mechanism of intercellular communication via MPs and summarize the role of MPs in pathological mechanisms with a particular focus on autoimmune diseases.

The Anti-DNA Antibodies: Their Specificities for Unique DNA Structures and Their Unresolved Clinical Impact-A System Criticism and a Hypothesis

Systemic lupus erythematosus (SLE) is diagnosed and classified by criteria, or by experience, intuition and traditions, and not by scientifically well-defined etiology(ies) or pathogenicity(ies). One central criterion and diagnostic factor is founded on theoretical and analytical approaches based on our imperfect definition of the term “The anti-dsDNA antibody”. “The anti-dsDNA antibody” holds an archaic position in SLE as a unique classification criterium and pathogenic factor. In a wider sense, antibodies to unique transcriptionally active or silent DNA structures and chromatin components may have individual and profound nephritogenic impact although not considered yet – not in theoretical nor in descriptive or experimental contexts. This hypothesis is contemplated here. In this analysis, our state-of-the-art conception of these antibodies is probed and found too deficient with respect to their origin, structural DNA specificities and clinical/pathogenic impact. Discoveries of DNA structures and functions started with Miescher’s Nuclein (1871), via Chargaff, Franklin, Watson and Crick, and continues today. The discoveries have left us with a DNA helix that presents distinct structures expressing unique operations of DNA. All structures are proven immunogenic! Unique autoimmune antibodies are described against e.g. ssDNA, elongated B DNA, bent B DNA, Z DNA, cruciform DNA, or individual components of chromatin. In light of the massive scientific interest in anti-DNA antibodies over decades, it is an unexpected observation that the spectrum of DNA structures has been known for decades without being implemented in clinical immunology. This leads consequently to a critical analysis of historical and contemporary evidence-based data and of ignored and one-dimensional contexts and hypotheses: i.e. “one antibody - one disease”. In this study radical viewpoints on the impact of DNA and chromatin immunity/autoimmunity are considered and discussed in context of the pathogenesis of lupus nephritis.

An updated review of anti-Ro52 (TRIM21) antibodies impact in connective tissue diseases clinical management

Anti-Ro52 (or anti-TRIM21) antibodies are part of the family of anti-Ro/SSA antibodies, historically markers of Sjögren syndrome and systemic lupus erythematosus. Anti-Ro52 antibodies represent one the most frequently encountered autoantibodies in patients with connective tissue disease (primary Sjögren syndrome, systemic lupus erythematosus, systemic sclerosis and idiopathic inflammatory myopathies). Because of their lack of specificity and detection in patients with non-autoimmune disorders, the usefulness of anti-Ro52 testing in connective tissue diseases is still matter of debate among clinicians and immunologists. Autoantibodies are mainly diagnostic markers for autoimmune diseases but some of them can also be directly involved in the generation of tissue damage. Over the past decade several authors reported associations of anti-Ro52 antibodies with some clinical features - especially interstitial lung disease - and survival in patients with connective tissue diseases. There is also a growing evidence of the role of anti-Ro52 antibodies in the pathogenesis of connective tissue diseases. In this review, we comprehensively discuss the clinical associations of anti-Ro52 antibodies in the different connective tissue diseases and the recent advances on their potential role in the inflammatory response.

Comparative analysis of three methods in anti-dsDNA antibodies detection: implications for Systemic Lupus Erythematosus diagnosis

The evaluation of anti-dsDNA antibodies represents one of the essential diagnostic and prognostic marker features in patients affected by Systemic Lupus Erythematosus (SLE). In this study, we have compared immunoblotting (IB) with Crithidia luciliae indirect immunofluorescence test (CLIFT) and chemiluminescent immunoassay (CLIA) in 91 patients referred to our hospital for anti-dsDNA antibodies detection. The concordance and correlation measured by Cohen's kappa and Spearman's coefficient respectively was significant between CLIFT and CLIA (0.70; 0,7404, P < .0001) and among CLIA and IB (0.79; 0,5377, P < 0,0001) and lower between CLIFT and IB (0.55; 0,4373, P  <0,0001). Among the 46 IB-positive samples, 14 were positive for either CLIA or CLIFT. It is noteworthy that 11 out of these 14 samples had the final diagnosis of SLE. Thirteen out of fourteen samples were also positive for anti-nucleosome antibodies as measured concomitantly in immunoblotting. While our observations are based on a limited number of samples and will have to be confirmed in a bigger cohort, they underline the contribution of immunoblotting as an additional assay in defining the anti-dsDNA antibody profile in association with other well-established methods such as CLIA and CLIFT.

Update and clinical management of anti-DNA auto-antibodies

Anti-deoxyribonucleic acid (DNA) antibodies in the clinical laboratory are intimately linked to the diagnosis and monitoring of systemic lupus erythematosus (SLE); however, the characteristics of the analytical methods and the properties of the antibodies themselves are heterogeneous. To review the definition and properties of anti-double-stranded anti-DNA (anti-dsDNA) antibodies, the adequacy of analytical methods, and the clinical requirements for this biomarker. Through PubMed we searched the existing literature with the terms anti-dsDNA, editorial, review, guideline, meta-analysis and SLE. The last search, anti-dsDNA and SLE restricted to the last two years. Information was expanded through related articles and those published in official state bodies related to anti-dsDNA and SLE. Clinical laboratory methods for anti-dsDNA analysis and their characteristics are analyze. The clinical utility of anti-dsDNA in its diagnostic, clinical association and follow-up aspects of SLE is reviewed. There is wide variability in analytical methods and deficits in standardization persist. They are part of the current SLE classification criteria and are used as markers in the follow-up of the disease. Their diagnostic usefulness improves when they are determined in antinuclear antibody (ANA)-positive patients. In follow-up, quantification is of interest, preferably with the same analytical method (given the deficits in standardization).

Acute Kidney Injury Induced Lupus Exacerbation Through the Enhanced Neutrophil Extracellular Traps (and Apoptosis) in Fcgr2b Deficient Lupus Mice With Renal Ischemia Reperfusion Injury

Renal ischemia is the most common cause of acute kidney injury (AKI) that might be exacerbate lupus activity through neutrophil extracellular traps (NETs) and apoptosis. Here, the renal ischemia reperfusion injury (I/R) was performed in Fc gamma receptor 2b deficient (Fcgr2b-/-) lupus mice and the in vitro experiments. At 24 h post-renal I/R injury, NETs in peripheral blood neutrophils and in kidneys were detected using myeloperoxidase (MPO), neutrophil elastase (NE) and citrullinated histone H3 (CitH3), as well as kidney apoptosis (activating caspase-3), which were prominent in Fcgr2b-/- mice more compared to wild-type (WT). After 120 h renal-I/R injury, renal NETs (using MPO and NE) were non-detectable, whereas glomerular immunoglobulin (Ig) deposition and serum anti-dsDNA were increased in Fcgr2b-/- mice. These results imply that renal NETs at 24 h post-renal I/R exacerbated the lupus nephritis at 120 h post-renal I/R injury in Fcgr2b-/- lupus mice. Furthermore, a Syk inhibitor attenuated NETs, that activated by phorbol myristate acetate (PMA; a NETs activator) or lipopolysaccharide (LPS; a potent inflammatory stimulator), more prominently in Fcgr2b-/- neutrophils than the WT cells as determined by dsDNA, PAD4 and MPO. In addition, the inhibitors against Syk and PAD4 attenuated lupus characteristics (serum creatinine, proteinuria, and anti-dsDNA) in Fcgr2b-/- mice at 120 h post-renal I/R injury. In conclusion, renal I/R in Fcgr2b-/- mice induced lupus exacerbation at 120 h post-I/R injury partly because Syk-enhanced renal NETs led to apoptosis-induced anti-dsDNA, which was attenuated by a Syk inhibitor.

Harnessing Tolerogenic Histone Peptide Epitopes From Nucleosomes for Selective Down-Regulation of Pathogenic Autoimmune Response in Lupus (Past, Present, and Future)

Autoantigen-directed tolerance can be induced by certain nucleosomal histone peptide epitope/s in nanomolar dosage leading to sustained remission of disease in mice with spontaneous SLE. By contrast, lupus is accelerated by administration of intact (whole) histones, or whole nucleosomes in microparticles from apoptotic cells, or by post-translationally acetylated histone-peptides. Low-dose therapy with the histone-peptide epitopes simultaneously induces TGFβ and inhibits IL-6 production by DC in vivo, especially pDC, which then induce CD4+CD25+ Treg and CD8+ Treg cells that suppress pathogenic autoimmune response. Both types of induced Treg cells are FoxP3+ and act by producing TGFβ at close cell-to-cell range. No anaphylactic adverse reactions, or generalized immunosuppression have been detected in mice injected with the peptides, because the epitopes are derived from evolutionarily conserved histones in the chromatin; and the peptides are expressed in the thymus during ontogeny, and their native sequences have not been altered. The peptide-induced Treg cells can block severe lupus on adoptive transfer reducing inflammatory cell reaction and infiltration in the kidney. In Humans, similar potent Treg cells are generated by the histone peptide epitopes in vitro in lupus patients’ PBMC, inhibiting anti-dsDNA autoantibody and interferon production. Furthermore, the same types of Treg cells are generated in lupus patients who are in very long-term remission (2-8 years) after undergoing autologous hematopoietic stem cell transplantation. These Treg cells are not found in lupus patients treated conventionally into clinical remission (SLEDAI of 0); and consequently they still harbor pathogenic autoimmune cells, causing subclinical damage. Although antigen-specific therapy with pinpoint accuracy is suitable for straight-forward organ-specific autoimmune diseases, Systemic Lupus is much more complex. The histone peptide epitopes have unique tolerogenic properties for inhibiting Innate immune cells (DC), T cells and B cell populations that are both antigen-specifically and cross-reactively involved in the pathogenic autoimmune response in lupus. The histone peptide tolerance is a natural and non-toxic therapy suitable for treating early lupus, and also maintaining lupus patients after toxic drug therapy. The experimental steps, challenges and possible solutions for successful therapy with these peptide epitopes are discussed in this highly focused review on Systemic Lupus.

Autoantibodies spectrum in lupus nephritis in a cohort of Egyptian patients: relation to disease activity and prognostic value

Background

Specific autoantibodies are considered as an important marker in autoimmune rheumatic diseases and are of great value for the diagnosis and prognosis of systemic lupus erythematosus (SLE) patients. A total of eighteen autoantibodies were analyzed for their positivity in SLE patients and we evaluated the clinical relevance of the five most frequent autoantibodies: anti-dsDNA, anti-nucleosome, anti-histone, anti-Ro60, and anti-Ro52 on disease activity and renal affection in SLE Egyptian patients.

Results

Immunological profile and correlation of the five autoantibodies with disease activity and histopathological pattern of renal involvement were analyzed for 190 SLE patients. Lupus nephritis (LN) patients showed much worse constitutional and mucocutaneous manifestations than patients without nephritis. Autoantibody profile showed a significant increased frequency of anti-dsDNA, anti-nucleosome, anti-histone, anti-Ro-60, and anti-Ro52 antibodies in LN patients. The impact of the co-positivity of the autoantibodies on the renal function was obvious. Moreover, the disease activity increased by the increased frequency of autoantibodies positivity in LN patients. ROC curve analysis showed that anti-nucleosome had the highest sensitivity; 93% followed by anti-dsDNA 83.3% then anti-histone 73.8%, but anti-Ro60 and anti-Ro52 showed a humble sensitivity. Furthermore, the highest frequency of positivity for the five autoantibodies was found in class-III and class-IV LN patients.

Conclusion

Detection of anti-dsDNA, anti-nucleosome, anti-histone, and anti-Ro60 in SLE patients may be important for predicting disease progression and kidney affection. Moreover, anti-nucleosome and anti-dsDNA show high sensitivity and specificity for lupus nephritis, thus patients with four to five positive autoantibody panels should be kept under close monitoring as they may warrant considering aggressive therapy to control their disease and prevent renal damage.

Immune Sensing of Cell Death through Recognition of Histone Sequences by C-Type Lectin-Receptor-2d Causes Inflammation and Tissue Injury

The immune system monitors the health of cells and is stimulated by necrosis. Here we examined the receptors and ligands driving this response. In a targeted screen of C-type lectin receptors, a Clec2d reporter responded to lysates from necrotic cells. Biochemical purification identified histones, both free and bound to nucleosomes or neutrophil extracellular traps, as Clec2d ligands. Clec2d recognized poly-basic sequences in histone tails and this recognition was sensitive to post-translational modifications of these sequences. As compared with WT mice, Clec2d^-/- mice exhibited reduced proinflammatory responses to injected histones, and less tissue damage and improved survival in a hepatotoxic injury model. In macrophages, Clec2d localized to the plasma membrane and endosomes. Histone binding to Clec2d did not stimulate kinase activation or cytokine production. Rather, histone-bound DNA stimulated endosomal Tlr9-dependent responses in a Clec2d-dependent manner. Thus, Clec2d binds to histones released upon necrotic cell death, with functional consequences to inflammation and tissue damage.

Measuring plasma C4D to monitor immune complexes in lupus nephritis

Objective

Because currently available assays that measure circulating immune complexes (ICx) are suboptimal, a novel assay was recently developed measuring C4d, a stable product of activation of the classical complement pathway. The present study aimed to establish the value of measuring plasma C4d levels in a longitudinal cohort of patients with severe refractory SLE who were treated with a combination therapy of rituximab with belimumab (RTX+BLM).

Methods

Fifteen patients with SLE who were treated with RTX+BLM in a phase 2A, open label study were included to sequentially measure plasma C4d levels and correlated to well-established markers of ICx-formation, that is, autoantibodies against double-stranded (ds) DNA, autoantibodies against C1q and proteinuria. The performance of plasma C4d measurements, C4 measurements and the ratio of C4d over C4 (C4d:C4) was evaluated.

Results

After establishing that on RTX+BLM treatment kinetics of C4d levels was distinct from traditional C3 and C4 levels, we found strong correlation of C4d:C4 with anti-dsDNA (R=0.76, p<0.001) and anti-C1q (R=0.65, p<0.001) autoantibody levels, which outperformed both stand-alone C4 and C4d levels. Additionally, changes in C4d:C4 over time correlated strongly with changes in proteinuria (R=0.59, p<0.001) as well as anti-dsDNA (R=0.46, p=0.003) and anti-C1q (R=0.47, p=0.002).

Conclusion

In patients with severe SLE, plasma C4d levels in relation to C4 levels is useful for longitudinal monitoring after RTX+BLM treatment to reflect amelioration of classical complement activation by ICx as well as proteinuria.

The dsDNA, Anti-dsDNA Antibody, and Lupus Nephritis: What We Agree on, What Must Be Done, and What the Best Strategy Forward Could Be

This study aims to understand what lupus nephritis is, its origin, clinical context, and its pathogenesis. Truly, we encounter many conceptual and immanent tribulations in our attempts to search for the pathogenesis of this disease—and how to explain its assumed link to SLE. Central in the present landscape stay a short history of the early studies that substantiated the structures of isolated or chromatin-assembled mammalian dsDNA, and its assumed, highly controversial role in induction of anti-dsDNA antibodies. Arguments discussed here may provoke the view that anti-dsDNA antibodies are not what we think they are, as they may be antibodies operational in quite different biological contexts, although they bind dsDNA by chance. This may not mean that these antibodies are not pathogenic but they do not inform how they are so. This theoretical study centers the content around the origin and impact of extra-cellular DNA, and if dsDNA has an effect on the adaptive immune system. The pathogenic potential of chromatin-anti-dsDNA antibody interactions is limited to incite lupus nephritis and dermatitis which may be linked in a common pathogenic process. These are major criteria in SLE classification systems but are not shared with other defined manifestations in SLE, which may mean that they are their own disease entities, and not integrated in SLE. Today, the models thought to explain lupus nephritis are divergent and inconsistent. We miss a comprehensive perspective to try the different models against each other. To do this, we need to take all elements of the syndrome SLE into account. This can only be achieved by concentrating on the interactions between autoimmunity, immunopathology, deviant cell death and necrotic chromatin in context of elements of system science. System science provides a framework where data generated by experts can be compared, and tested against each other. This approach open for consensus on central elements making up “lupus nephritis” to separate what we agree on and how to understand the basis for conflicting models. This has not been done yet in a systematic context.

Prophylactic and Therapeutic Effects of Interleukin-2 (IL-2)/Anti-IL-2 Complexes in Systemic Lupus Erythematosus-Like Chronic Graft-Versus-Host Disease

Murine chronic graft-versus-host-disease (cGvHD) induced by injection of parental lymphocytes into F1 hybrids results in a disease similar to systemic lupus erythematosus. Here, we have used DBA/2 T cell injection into (C57BL/6 × DBA/2)F1 (BDF1) mice as a model system to test the prophylactic and therapeutic effects of interleukin-2 (IL-2)/anti-IL-2 immune complexes on the course of cGvHD. Our findings demonstrate that pretreatment with Treg inducing JES6/IL-2 complexes render BDF1 mice largely resistant to induction of cGvHD, whereas pretreatment with CD8⁺ T cell/NK cell inducing S4B6/IL-2 complexes results in a more severe cGvHD. In contrast, treatment with JES6/IL-2 complexes 4 weeks after induction had no beneficial effect on disease symptoms. However, similar treatment with S4B6/IL-2 complexes led to a significant amelioration of the disease. This therapeutic effect seems to be mediated by donor CD8⁺ T cells. The fact that a much stronger cGvHD is induced in BDF1 mice depleted of donor CD8⁺ T cells strongly supports this conclusion. The contrasting effects of the two different IL-2 complexes are likely due to different mechanisms.

Impaired TLR9 responses in B cells from patients with systemic lupus erythematosus

B cells play a central role in systemic lupus erythematosus (SLE) pathophysiology but dysregulated pathways leading to a break in B cell tolerance remain unclear. Since Toll-like receptor 9 (TLR9) favors the elimination of autoreactive B cells in the periphery, we assessed TLR9 function in SLE by analyzing the responses of B cells and plasmacytoid dendritic cells (pDCs) isolated from healthy donors and patients after stimulation with CpG, a TLR9 agonist. We found that SLE B cells from patients without hydroxychloroquine treatment displayed defective in vitro TLR9 responses, as illustrated by the impaired upregulation of B cell activation molecules and the diminished production of various cytokines including antiinflammatory IL-10. In agreement with CD19 controlling TLR9 responses in B cells, decreased expression of the CD19/CD21 complex on SLE B cells was detected as early as the transitional B cell stage. In contrast, TLR7 function was preserved in SLE B cells, whereas pDCs from SLE patients properly responded to TLR9 stimulation, thereby revealing that impaired TLR9 function in SLE was restricted to B cells. We conclude that abnormal CD19 expression and TLR9 tolerogenic function in SLE B cells may contribute to the break of B cell tolerance in these patients.

IL-1β Promotes a New Function of DNase I as a Transcription Factor for the Fas Receptor Gene

Recently we described that endonuclease inactive DNase I translocated into the nucleus in response to increased endogenous IL-1β expression. Here, we demonstrate impact and function of translocated DNase I in tubular cells. Effect of cytokines on expression level and nuclear localisation of DNase I and corresponding levels of Fas receptor (FasR) and IL-1β were determined by confocal microscopy, qPCR and western blot analyses, in presence or absence of siRNA against IL-1β and DNase I mRNA. Nuclear DNase I bound to the FAS promotor region as determined by chromatin immuno-precipitation analysis. Data demonstrate that; (i) translocation of DNase I depended on endogenous de novo-expressed IL-1β, (ii) nuclear DNase I bound FAS DNA, (iii) FasR expression increased after translocation of DNase I, (iv) interaction of exogenous Fas ligand (FasL) with upregulated FasR induced apoptosis in human tubular cells stimulated with TNFα. Thus, translocated DNase I most probably binds the promoter region of the FAS gene and function as a transcription factor for FasR. In conclusion, DNase I not only executes chromatin degradation during apoptosis and necrosis, but also primes the cells for apoptosis by enhancing FasR expression.

Phenotyping of autoreactive B cells with labeled nucleosomes in 56R transgenic mice

The phenotypic characterization of self-reactive B cells producing autoantibodies is one of the challenges to get further insight in the physiopathology of autoimmune diseases. We took advantage of our previously developed flow cytometry method, using labeled nucleosomes, prominent autoantigens in systemic lupus erythematosus, to analyze the phenotype of self-reactive B cells in the anti-DNA B6.56R mouse model. We showed that splenic anti-nucleosome B cells express mostly kappa light chains and harbor a marginal zone phenotype. Moreover, these autoreactive B cells fail to acquire a germinal center phenotype and are less abundant in the transitional T3 compartment. In conclusion, the direct detection of autoreactive B cells helped determine their phenotypic characteristics and provided a more direct insight into the B cell tolerance process in B6.56R mice. This method constitutes an interesting new tool to study the mechanisms of B cell tolerance breakdown in B6.56R mice crossed with autoimmune prone models.

Acetylated Histones in Apoptotic Microparticles Drive the Formation of Neutrophil Extracellular Traps in Active Lupus Nephritis

Objective

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by the presence of autoantibodies against nuclear components. Lupus nephritis (LN) is the major cause of morbidity and mortality in patients with SLE. Central to the pathogenesis of SLE is the accumulation of cellular waste, especially apoptotic microparticles (MPs), which stimulates diverse immune reactions including the formation of neutrophil extracellular traps (NETs). In this study, we investigated the content of MPs from SLE patients with and without (active) LN, their capacity to stimulate NET release, and assessed the molecular mechanisms underlying MP-induced NETosis.

Methods

MPs from SLE patients with biopsy-proven active LN, remissive LN, without LN, and healthy controls were characterized by flow cytometry. Isolated neutrophils were exposed to MPs derived from either patient plasma or apoptotic human umbilical vein endothelial cells, and NET release was quantified by immunofluorescence imaging, spectrofluorometry or an in-house developed NET ELISA.

Results

MPs from SLE patients with active LN contain higher levels of acetylated chromatin compared to MPs from those with remissive LN, without LN, or healthy controls. MPs enriched in hyperacetylated chromatin are more potent in inducing NETosis when compared to MPs containing moderate acetylated chromatin. The release of NETs in response to MPs occurs rapidly in a concentration-dependent manner and proceeds independent from the formation of reactive oxygen species (ROS).

Conclusion

Our data suggest that MPs containing acetylated chromatin drive ROS-independent NET release in SLE patients with active LN, which may lead to the glomerular deposition of NETs and subsequent NET-driven LN.

The impact of biological treatments on the anti-dsDNA and anti-nucleosome tests

Background Anti-double stranded DNA antibodies are a very heterogeneous group of antibodies, quite specific for systemic lupus erythematosus. Newer technologies, such as addressable laser bead immunoassays (ALBIA), show great potential as a diagnostic application. The production of anti-double stranded DNA antibodies is often encountered in inflammatory arthritis; however, literature reports that the actual onset of drug induced lupus in patients treated with biological drugs is a rare event. False positive results for anti-double stranded DNA and anti-nucleosome antibodies detected in patients with inflammatory arthritis treated with different biologics prompted the investigation of full autoantibody profiles to evaluate each biomarker's diagnostic performance in systemic lupus erythematosus. The aim of the study was to compare the diagnostic performance of anti-double stranded DNA antibody and anti-nucleosome antibody methods and to evaluate the value of simultaneously measuring anti-double stranded DNA and anti-nucleosome antibodies, along with other anti-nuclear antibody analytes, as biomarkers for systemic lupus erythematosus, using a more appropriate control cohort including inflammatory arthritis patients with a non-clinical drug induced lupus. Methods Anti-double stranded DNA and anti-nucleosome antibody levels were evaluated in 247 patient samples: 70 systemic lupus erythematosus, 177 disease controls (including 97 inflammatory arthritis during treatment with different biologics) using the Bio-Rad BioPlex® 2200. Results Anti-nucleosome antibodies demonstrated greater clinical sensitivity and specificity than anti-double stranded DNA antibodies. At the manufacturers' cut-off range, considering the two markers as a single or combined test, the "anti-double stranded DNA test or anti-nucleosome antibodies" was the most sensitive combination (0.400) with the best negative likelihood ratio (0.62) and negative predictive value (0.803). Conclusion Anti-nucleosome antibodies are a more sensitive and specific biomarker of systemic lupus erythematosus than anti-double stranded DNA antibodies. Anti-nucleosome antibodies and anti-double stranded DNA antibodies are independent and complementary markers of systemic lupus erythematosus diagnosis and, therefore, are strongly suggested as combined tests (positive predictive value = 0.938). Moreover, the combined use of the two tests may help to overcome the decreased specificity percentage of the anti-double stranded DNA test, when considering an inflammatory arthritis cohort under biological therapies. The ALBIA method for anti-nuclear specificity detection allows a full autoantibody assessment, resulting in a much higher clinical specificity for systemic lupus erythematosus in the presence of ≥3 positive markers and significantly more positive likelihood ratio when ≥2 positive markers are present.

Identification of autoreactive B cells with labeled nucleosomes

The pathogenesis of autoimmune diseases has not been completely elucidated yet, and only a few specific treatments have been developed so far. In autoimmune diseases mediated by pathogenic autoantibodies, such as systemic lupus erythematosus, the specific detection and analysis of autoreactive B cells is crucial for a better understanding of the physiopathology. Biological characterization of these cells may help to define new therapeutic targets. Very few techniques allowing the precise detection of autoreactive B cells have been described so far. Herein we propose a new flow cytometry technique for specific detection of anti-nucleosome B cells, which secrete autoantibodies in systemic lupus erythematosus, using labeled nucleosomes. We produced different fluorochrome-labeled nucleosomes, characterized them, and finally tested them in flow cytometry. Nucleosomes labeled via the cysteines present in H3 histone specifically bind to autoreactive B cells in the anti-DNA transgenic B6.56R mice model. The present work validates the use of fluorochrome-labeled nucleosomes via cysteines to identify anti-nucleosome B cells and offers new opportunities for the description of autoreactive B cell phenotype.

Autoantibodies against Modified Histone Peptides in SLE Patients Are Associated with Disease Activity and Lupus Nephritis

Persistent exposure of the immune system to death cell debris leads to autoantibodies against chromatin in patients with systemic lupus erythematosus (SLE). Deposition of anti-chromatin/chromatin complexes can instigate inflammation in multiple organs including the kidney. Previously we identified specific cell death-associated histone modifications as targets of autoantibodies in SLE. In this study we addressed, in a large cohort of SLE patients and controls, the question whether plasma reactivities with specific histone peptides associated with serology and clinical features. Plasma from SLE patients with and without lupus nephritis, disease controls, and healthy controls, were tested in ELISA with histone H4 peptide acetylated at lysines 8, 12 and 16 (H4p^ac), H2B peptide acetylated at lysine 12 (H2Bp^ac), H3 peptide trimethylated at lysine 27 (H3p^me), and their unmodified equivalents. SLE patients displayed a higher reactivity with the modified equivalent of each peptide. Reactivity with H4p^ac showed both a high sensitivity (89%) and specificity (91%) for SLE, while H2Bp^ac exhibited a high specificity (96%) but lower sensitivity (69%). Reactivity with H3p^me appeared not specific for SLE. Anti-H4p^ac and anti-H2Bp^ac reactivity demonstrated a high correlation with disease activity. Moreover, patients reacting with multiple modified histone peptides exhibited higher SLEDAI and lower C3 levels. SLE patients with renal involvement showed higher reactivity with H2B/H2Bp^ac and a more pronounced reactivity with the modified equivalent of H3p^me and H2Bp^ac. In conclusion, reactivity with H4p^ac and H2Bp^ac is specific for SLE patients and correlates with disease activity, whereas reactivity with H2Bp^ac is in particular associated with lupus nephritis.

Future Perspectives on Pathogenesis of Lupus Nephritis: Facts, Problems, and Potential Causal Therapy Modalities

Divergent incommensurable models have been developed to explain the pathogenesis of lupus nephritis. Most contemporary models favor a central role for anti-chromatin antibodies. How they exert their pathogenic effect has, however, endorsed conflicts that at least for now preclude insight into definitive pathogenic pathways. The following paradigms are contemporarily in conflict with each other: i) the impact of anti-double-stranded DNA (dsDNA) antibodies that cross-react with inherent renal antigens, ii) the impact of anti-dsDNA antibodies targeting exposed chromatin in glomeruli, and iii) the impact of relative antibody avidity for dsDNA, chromatin fragments, or cross-reacting antigens. Aside from these three themes, the pathogenic role of T cells in lupus nephritis is not clear. These different models should be tested through a collaboration between scientists belonging to the different paradigms. If it turns out that there are different pathogenic pathways in lupus nephritis, the emerging pathogenic mechanism(s) may be encountered with new individual causal therapy modalities. Today, therapy is still unspecific and far from interfering with the cause(s) of the disorder. This review attempts to describe what we know about processes that may cause lupus nephritis and how such basic processes may be affected if we can specifically interrupt them. Secondary inflammatory mechanisms, cytokine signatures, activation of complement, and other contributors to inflammation will not be discussed herein; rather, the events that trigger these factors will be discussed.

Murine and Human Lupus Nephritis: Pathogenic Mechanisms and Theoretical Strategies for Therapy

Lupus nephritis is one of the most serious manifestations of systemic lupus erythematosus, and represents one of the criteria implemented to classify systemic lupus erythematosus. Although studied for decades, no consensus has been reached related to the basic cellular, molecular, and immunologic mechanism(s) responsible for lupus nephritis. No causal treatments have been developed; therapy is approached mainly with nonspecific immunosuppressive medications. More detailed insight into disease mechanisms therefore is indispensable to develop new therapeutic strategies. In this review, contemporary knowledge on the pathogenic mechanisms of lupus nephritis is discussed based on recent data in murine and human lupus nephritis. Specific focus is given to the effect of anti-double-stranded DNA/antinucleosome antibodies in the kidneys and whether they bind exposed chromatin fragments in glomeruli or whether they bind inherent glomerular structures by cross-recognition. Overall, the data presented here favor the exposed chromatin model because we did not find any indication to substantiate the anti-double-stranded DNA antibody cross-reacting model. At the end of this review we present data on why chromatin fragments are expressed in the glomeruli of patients with lupus nephritis, and discuss how this knowledge can be used to direct the development of future therapies.

Diagnostic value of progranulin in patients with lupus nephritis and its correlation with disease activity

The aim of this study was to explore whether progranulin (PGRN) can be a useful marker not only for accurate diagnosis of patients with active lupus nephritis (LN), but also for prediction of the disease activity in this population. A total of 154 LN patients were enrolled in this study, 76 of which were diagnosed as having active LN and 78 as having stable LN. Additionally, 71 age-matched non-LN patients were enrolled as controls. The serum and urine PGRN levels of each study population were measured using the enzyme-linked immunosorbent assay method. The diagnostic performance of both indicators and their correlation with the disease activity of LN were systematically investigated using receiver operating characteristic (ROC) analysis and correlation analysis. The active LN population had significantly higher serum and urine PGRN levels than the other two populations. ROC analysis further demonstrated that these two indicators, particularly in combination, appear to have a strong performance in discriminating active LN patients from the rest of the LN population. In the active LN population, serum and urine PGRN levels were not only significantly correlated with SLEDAI score, rSLEDAI score, and activity index, but also had a considerable association with several key markers reflecting the disease activity of LN, including serum levels of complement component 3 and ds-DNA. Nevertheless, neither of the two indicators were correlated with the pathological classification of LN, chronicity index, serum creatinine level, and 24-h urine protein levels. Our findings demonstrate that PGRN may have great potential as a diagnostic factor for active LN and as a predictor for its disease activity.

Reactivity in ELISA with DNA-loaded nucleosomes in patients with proliferative lupus nephritis

Autoantibodies against nucleosomes are considered a hallmark of systemic lupus erythematosus (SLE). We compared in patients with proliferative lupus nephritis the diagnostic usefulness of a dsDNA-loaded nucleosome ELISA (anti-dsDNA-NcX) with ELISAs in which dsDNA or nucleosomes alone were coated. First, we analysed whether DNA loading on nucleosomes led to masking of epitopes by using defined monoclonal anti-DNA, anti-histone and nucleosome-specific autoantibodies to evaluate the accessibility of nucleosomal epitopes in the anti-dsDNA-NcX ELISA. Second, autoantibody levels were measured in these 3 ELISAs in 100 patients with proliferative lupus nephritis (LN) before immunosuppressive treatment and in 128 non-SLE disease controls. In patients with LN inter-assay comparisons and associations with clinical and serological parameters were analysed. The panel of monoclonal antibodies revealed that all epitopes were equally accessible in the anti-dsDNA-NcX ELISA as in the two other ELISAs. Patients with proliferative lupus nephritis were positive with dsDNA-loaded nucleosomes in 86%, with DNA in 66% and with nucleosomes in 85%. In the non-lupus disease control group these frequencies were 1.6% (2 out of 128) for both the anti-dsDNA-NcX and the anti-dsDNA ELISA and 0% in the anti-nucleosome ELISA. The levels in the anti-dsDNA-NcX ELISA were high in a group of patients with LN that showed absent reactivity in the anti-DNA or low levels in the anti-nucleosome ELISA. Anti-dsDNA-NcX positivity was associated with higher SLEDAI scores within this group. Within nucleosome-based ELISAs, we propose the anti-dsDNA-NcX ELISA as the preferred test system.

Co-Positivity for Anti-dsDNA, -Nucleosome and -Histone Antibodies in Lupus Nephritis Is Indicative of High Serum Levels and Severe Nephropathy

OBJECTIVE

To characterize the significance of correlated autoantibodies in systemic lupus erythematosus (SLE) and its complication lupus nephritis (LN) in a large cohort of patients.

METHODS

Clinical data were statistically analyzed in 1699 SLE patients with or without nephritis who were diagnosed and treated during 2002-2013 in the northeast region of China. Reactivity to a list of 16 autoantibodies was detected by the serum test Euroline ANA profile (IgG). Serum titers of the anti-nucleosome autoantibodies were measured by ELISA assays. Kidney biopsies were examined by pathologists. Immune complex deposition was identified by immunohistochemistry stain.

RESULTS

Simultaneous positivity of anti-dsDNA, -nucleosome and -histone antibodies (3-pos) was prevalent in SLE patients with LN compared to Non-renal SLE patients (41% vs 11%, p< 0.001). Significant correlations were found between any two of the above three anti-nucleosome antibodies in LN patients. In comparison to non-3-pos cohorts, 3-pos patients with LN had significantly higher serum levels of the three antibodies and more active disease; was associated with type IV disease; suffered from more severe renal damages; received more intensive treatment and had worse disease outcome. The serum levels of these three autoantibodies in 3-pos LN patients were significantly decreased when they underwent clinical recovery.

CONCLUSIONS

Simultaneous reactivity to anti-dsDNA, -nucleosome and -histone antibodies by Euroline ANA profile (IgG) may indicate severe nephropathy in patients with SLE.

The anti-DNA antibody: origin and impact, dogmas and controversies

The inclusion of 'the anti-DNA antibody' by the ACR and the Systemic Lupus International Collaborating Clinics (SLICC) as a criterion for systemic lupus erythematosus does not convey the diverse origins of these antibodies, whether their production is transient or persistent (which is heavily influenced by the nature of the inducing antigens), the specificities exerted by these antibodies or their clinical impact-or lack thereof. A substantial amount of data not considered in clinical medicine could be added from basic immunology evidence, which could change the paradigms linked to what 'the anti-DNA antibody' is, in a pathogenic, classification or diagnostic context.

Enhanced activation of dendritic cells by autologous apoptotic microvesicles in MRL/lpr mice

Introduction

Systemic lupus erythematosus is associated with a persistent circulation of modified autoantigen-containing apoptotic debris that might be capable of breaking tolerance. We aimed to evaluate apoptotic microvesicles obtained from lupus or control mice for the presence of apoptosis-associated chromatin modifications and for their capacity to stimulate dendritic cells (DC) from lupus and control mice.

Method

Apoptotic microvesicles were in vitro generated from splenocytes, and ex vivo isolated from plasma of both MRL/lpr lupus mice and normal BALB/c mice. Microvesicles were analyzed using flow cytometry. Bone marrow-derived (BM)-DC cultured from MRL/lpr or BALB/c mice were incubated with microvesicles and CD40 expression and cytokine production were determined as measure of activation.

Results

Microvesicles derived from apoptotic splenocytes or plasma of MRL/lpr mice contained more modified chromatin compared to microvesicles of BALB/c mice, and showed enhanced activation of DC, either from MRL/lpr or BALB/c mice, and consecutively an enhanced DC-mediated activation of splenocytes. The content of apoptosis-modified chromatin in microvesicles of apoptotic splenocytes correlated with their potency to induce interleukin-6 (IL-6) production by DC. Microvesicle-activated MRL/lpr DC showed a significant higher production of IL-6 and tumor growth factor-β (TGF-β) compared to BALB/c DC, and were more potent in the activation of splenocytes.

Conclusion

Apoptotic microvesicles from MRL/lpr mice are more potent activators of DC, and DC from MRL/lpr mice appear relatively more sensitive to activation by apoptotic microvesicles. Our findings indicate that aberrations at the level of apoptotic microvesicles and possibly DC contribute to the autoimmune response against chromatin in MRL/lpr mice.

Anti-dsDNA and Antichromatin Antibody Isotypes in Serologically Active Clinically Quiescent Systemic Lupus Erythematosus

OBJECTIVE

Serologically active clinically quiescent (SACQ) patients with systemic lupus erythematosus (SLE) are clinically quiescent despite serologic activity. Since studies suggest that antichromatin antibodies are more sensitive than anti-dsDNA antibodies in detecting active SLE, and that immunoglobulin (Ig) G, in particular complement-fixing subclasses, may be more pathogenic than IgM, we investigated the levels of anti-dsDNA and antichromatin isotypes in SACQ patients as compared to non-SACQ patients with SLE.

METHODS

Levels of IgM, IgA, IgG, and IgG1-4 antichromatin and anti-dsDNA were measured by ELISA. SACQ was defined as ≥ 2 years with the SLE Disease Activity Index 2000 (SLEDAI-2K) at 2 or 4 from serologic activity, during which patients could be taking antimalarials, but not corticosteroids or immunosuppressives. Unselected non-SACQ patients with SLE were used as comparators. SACQ patient serum samples were further stratified based on subsequent development of flare, defined as clinical SLEDAI-2K ≥ 1 and/or treatment initiation. Nonparametric statistics were used, and generalized estimating equations were applied to account for multiple samples in the same patient.

RESULTS

SACQ patients' complement-fixing antichromatin and anti-dsDNA IgG subclasses were significantly higher than those of non-SACQ patients. When the sample drawn latest in a SACQ period was analyzed, there was no difference between antichromatin or anti-dsDNA isotype or IgG subclass levels between patients who flared and those who remained SACQ, nor were consistent trends seen when samples were examined during SACQ and flare in the same patient.

CONCLUSION

The SACQ phenotype does not arise from a lack of pathogenic anti-dsDNA and/or antichromatin autoantibodies. Neither increases in antichromatin nor anti-dsDNA isotype or IgG subclass levels were predictive of or coincident with flare in SACQ patients.

Acetylated histones contribute to the immunostimulatory potential of neutrophil extracellular traps in systemic lupus erythematosus

In addition to disturbed apoptosis and insufficient clearance of apoptotic cells, there is recent evidence for a role of neutrophils in the aetiopathogenesis of systemic lupus erythematosus (SLE). In response to various stimuli, neutrophils can rapidly release DNA fibres decorated with citrullinated histones and anti-microbial peptides. These structures are referred to as neutrophil extracellular traps (NETs). In addition to apoptotic cell-derived microparticles, these NETs may comprise a further source of autoantigens, able to drive the autoimmune response in SLE. Our group recently identified specific histone modifications occurring during apoptosis that play an important role in the autoimmune response in SLE. In the current study, we evaluated the presence and immunostimulatory potential of these previously identified histone modifications in NETs. Compared to NETs from healthy donors, the histones present in NETs formed by SLE-derived neutrophils contain increased amounts of acetylated and methylated residues, which we previously observed to be associated with apoptosis and SLE. Treatment of neutrophils with histone deacetylase (HDAC) inhibitor Trichostatin A (TSA), prior to induction of NETosis, induced NETs containing hyperacetylated histones, endowed with an increased capacity to activate macrophages. This implies that specific histone modifications, in particular acetylation, might enhance the immunostimulatory potential of NETs in SLE.

The role of antigen specificity in the binding of murine monoclonal anti-DNA antibodies to microparticles from apoptotic cells

Antibodies to DNA (anti-DNA) are the serological hallmark of systemic lupus erythematosus and markers of underlying immune system disturbances. These antibodies bind to both single-stranded and double-stranded DNA, mediating pathogenesis by forming immune complexes. As shown recently, DNA in blood exists in both free and particulate forms, with DNA representing an important component of microparticles. Microparticles are membrane-bound vesicles containing nuclear molecules, released by membrane blebbing during cell death and activation. A panel of monoclonal NZB/NZW F1 anti-DNA antibodies was tested for binding to microparticles generated from apoptotic THP-1 and Jurkat cells. These studies showed that only certain anti-DNA antibodies in the panel, specific for double-stranded DNA, bound to microparticles. Binding to particles was reduced by soluble DNA or DNase treatment. Together, these results indicate that particle binding is a feature of only certain anti-DNA antibodies, reflecting immunochemical properties of the antibodies and the nature of the exposed DNA antigens.

The pathogenesis and diagnosis of systemic lupus erythematosus: still not resolved

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease with various clinical manifestations affecting different tissues. A characteristic feature of SLE is the presence of autoantibodies against double-stranded (ds)DNA, histones and nucleosomes, and other chromatin components. SLE is a prototype type III hypersensitivity reaction. Local deposition of anti-nuclear antibodies in complex with released chromatin induces serious inflammatory conditions by activation of the complement system. The severe renal manifestation, lupus nephritis, is classified based on histological findings in renal biopsies. Apoptotic debris, including chromatin, is present in the extracellular matrix and circulation of patients with SLE. This may be due to an aberrant process of apoptosis and/or insufficient clearance of apoptotic cells/chromatin. The non-cleared apoptotic debris may lead to activation of both the innate and adaptive immune systems. In addition, an aberrant presentation of peptides by antigen-presenting cells, disturbed selection processes for lymphocytes, and deregulated lymphocyte responses may be involved in the development of autoimmunity. In the present review, we briefly will summarize current knowledge on the pathogenesis of SLE. We will also critically discuss and challenge central issues that need to be addressed in order to fully understand the pathogenic mechanisms involved in the development of SLE and in order to have an improved diagnosis for SLE. Disappointingly, in our opinion, there are still more questions than answers for the pathogenesis, diagnosis, and treatment of SLE.

The spectrum of anti-chromatin/nucleosome autoantibodies: independent and interdependent biomarkers of disease

Autoantibodies directed to chromatin components date back to the discovery of the LE cell and the LE cell phenomenon circa 1950, and subsequent evidence that major components of that reaction were chromatin components and histones in particular. Over time, immunoassays ranging from ELISA and line immunoassays to more modern bead-based assays incorporated histone and DNA mixtures, purified histones, and purified nucleosomes leading to a more thorough understanding of the genesis and pathogenetic relationships of antibodies to chromatin components in systemic lupus erythematosus and other autoimmune conditions. More recently, interest has focussed on other components of chromatin such as high mobility group (HMG) proteins both as targets of B cell responses and pro-inflammatory mediators. This review will focus on immunoassays that utilize chromatin components, their clinical relationships, and newer evidence implicating HMG proteins and DNA neutrophil extracellular traps (NETs) as important players in systemic autoimmune rheumatic diseases.

Serology of Lupus Erythematosus: Correlation between Immunopathological Features and Clinical Aspects

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by the aberrant production of a broad and heterogenous group of autoantibodies. Even though the presence of autoantibodies in SLE has been known, for more than 60 years, still nowadays a great effort is being made to understand the pathogenetic, diagnostic, and prognostic meaning of such autoantibodies. Antibodies to ds-DNA are useful for the diagnosis of SLE, to monitor the disease activity, and correlate with renal and central nervous involvements. Anti-Sm antibodies are highly specific for SLE. Anti-nucleosome antibodies are an excellent marker for SLE and good predictors of flares in quiescent lupus. Anti-histone antibodies characterize drug-induced lupus, while anti-SSA/Ro and anti-SSB/La antibodies are associated with neonatal lupus erythematosus and photosensitivity. Anti-ribosomal P antibodies play a role in neuropsychiatric lupus, but their association with clinical manifestations is still unclear. Anti-phospholipid antibodies are associated with the anti-phospholipid syndrome, cerebral vascular disease, and neuropsychiatric lupus. Anti-C1q antibodies amplify glomerular injury, and the elevation of their titers may predict renal flares. Anti-RNP antibodies are a marker of Sharp's syndrome but can be found in SLE as well. Anti-PCNA antibodies are present in 5–10% of SLE patients especially those with arthritis and hypocomplementemia.

Reflections on Lupus 2013: butterflies, wolves and prophecies

The recently concluded Tenth International Congress on Systemic Lupus Erythematosus (SLE) held in Buenos Aires was a resounding success. This overview summarizes some of the origins of the First International Congress held in Calgary, Canada in 1986, predictions offered by past Congress Presidents, and a perspective on the trends in autoantibody testing, which remains one of the key approaches to the early and accurate diagnosis of SLE. The last few decades have witnessed a remarkable proliferation of new diagnostic technologies including addressable laser bead immunoassays and, more recently, chemiluminescence and lateral flow technologies that could find a clinical niche in point-of-care diagnostics. Against the backdrop of these constantly emerging technologies, indirect immunofluorescence has remained the platform of choice for many laboratories and diagnosticians. The notion that autoantibodies are pathogenic has been challenged by evidence that some autoantibodies are protective, some may have catalytic capacity while others may be neutral or have no function at all. The latter notion of functionless or "junk" autoantibodies needs to be taken under some advisement, because there was a time when a great proportion of the human genome was considered to include "junk DNA". The butterfly as a symbol of hope and progress in SLE research over the past 27 years since the First International Congress on SLE is almost certainly to be even more appropriate when future Congresses are held in Geneva (2015), Melbourne (2017) and eventually one in 2050.

Major pathogenic steps in human lupus can be effectively suppressed by nucleosomal histone peptide epitope-induced regulatory immunity

Low-dose tolerance therapy with nucleosomal histone peptide epitopes blocks lupus disease in mouse models, but effect in humans is unknown. Herein, we found that CD4(+)CD25(high)FoxP3(+) or CD4(+)CD45RA(+)FoxP3(low) T-cells, and CD8(+)CD25(+)FoxP3(+) T-cells were all induced durably in PBMCs from inactive lupus patients and healthy subjects by the histone peptide/s themselves, but in active lupus, dexamethasone or hydroxychloroquine unmasked Treg-induction by the peptides. The peptide-induced Treg depended on TGFβ/ALK-5/pSmad 2/3 signaling, and they expressed TGF-β precursor LAP. Lupus patients' sera did not inhibit Treg induction. The peptide epitope-induced T cells markedly suppressed type I IFN related gene expression in lupus PBMC. Finally, the peptide epitopes suppressed pathogenic autoantibody production by PBMC from active lupus patients to baseline levels by additional mechanisms besides Treg induction, and as potently as anti-IL6 antibody. Thus, low-dose histone peptide epitopes block pathogenic autoimmune response in human lupus by multiple mechanisms to restore a stable immunoregulatory state.

Lupus nephritis: enigmas, conflicting models and an emerging concept

Autoantibodies to components of chromatin, which include double-stranded DNA (dsDNA), histones and nucleosomes, are central in the pathogenesis of lupus nephritis. How anti-chromatin autoantibodies exert their nephritogenic activity, however, is controversial. One model assumes that autoantibodies initiate inflammation when they cross-react with intrinsic glomerular structures such as components of membranes, matrices or exposed nonchromatin ligands released from cells. Another model suggests glomerular deposition of autoantibodies in complex with chromatin, thereby inducing classic immune complex-mediated tissue damage. Recent data suggest acquired error of renal chromatin degradation due to the loss of renal DNaseI enzyme activity is an important contributing factor to the development of lupus nephritis in lupus-prone (NZBxNZW)F1 mice and in patients with lupus nephritis. Down-regulation of DNaseI expression results in reduced chromatin fragmentation and in deposition of extracellular chromatin-IgG complexes in glomerular basement membranes in individuals who produce IgG anti-chromatin autoantibodies. The main focus of the present review is to discuss whether exposed chromatin fragments in glomeruli are targeted by potentially nephritogenic anti-dsDNA autoantibodies or if the nephritogenic activity of these autoantibodies is explained by cross-reaction with intrinsic glomerular constituents or if both models coexist in diseased kidneys. In addition, the role of silencing of the renal DNaseI gene and the biological consequences of reduced chromatin fragmentation in nephritic kidneys are discussed.

Kallikrein transduced mesenchymal stem cells protect against anti-GBM disease and lupus nephritis by ameliorating inflammation and oxidative stress

Previously we have shown that kallikreins (klks) play a renoprotective role in nephrotoxic serum induced nephritis. In this study, we have used mesenchymal stem cells (MSCs) as vehicles to deliver klks into the injured kidneys and have measured their therapeutic effect on experimental antibody induced nephritis and lupus nephritis. Human KLK-1 (hKLK1) gene was transduced into murine MSCs using a retroviral vector to generate a stable cell line, hKLK1-MSC, expressing high levels of hKLK1. 129/svj mice subjected to anti-GBM induced nephritis were transplanted with 10⁶ hKLK1-MSCs and hKLK1 expression was confirmed in the kidneys. Compared with vector-MSCs injected mice, the hKLK1-MSCs treated mice showed significantly reduced proteinuria, blood urea nitrogen (BUN) and ameliorated renal pathology. Using the same strategy, we treated lupus-prone B6.Sle1.Sle3 bicongenic mice with hKLK1-MSCs and demonstrated that hKLK1-MSCs delivery also attenuated lupus nephritis. Mechanistically, hKLK1-MSCs reduced macrophage and T-lymphocyte infiltration into the kidney by suppressing the expression of inflammation cytokines. Moreover, hKLK1 transduced MSCs were more resistant to oxidative stress-induced apoptosis. These findings advance genetically modified MSCs as potential gene delivery tools for targeting therapeutic agents to the kidneys in order to modulate inflammation and oxidative stress in lupus nephritis.

Robust microarray production of freshly expressed proteins in a human milieu

PURPOSE

In vitro transcription/translation (IVTT) systems are widely used in proteomics. For clinical applications, mammalian systems are preferred for protein folding and activity; however, the level of protein obtained is low. A new system extracted from human cells (1-Step Human Coupled IVT (HCIVT)) has the potential to overcome this problem and deliver high yields of protein expressed in a human milieu.

EXPERIMENTAL DESIGN

Western blots and self-assembled protein microarrays were used to test the efficiency of protein synthesis by HCIVT compared to rabbit reticulocyte lysate (RRL). The arrays were also used to measure the immune response obtained from serum of patients exposed to pathogens or vaccine.

RESULTS

HCIVT performed better than RRL in all experiments. The yield of protein synthesized in HCIVT is more than ten times higher than RRL, in both Western blot and protein microarrays. Moreover, HCIVT showed a robust lot-to-lot reproducibility. In immune assays, the signals of many antigens were detected only in HCIVT-expressed arrays, mainly due to the reduction in the background signal and the increased levels of protein on the array.

CONCLUSION AND CLINICAL RELEVANCE

HCIVT is a robust in vitro transcription and translation system that yields high levels of protein produced in a human milieu. It can be used in applications where protein expression in a mammalian system and high yields are needed. The increased immunogenic response of HCIVT-expressed proteins will be critical for biomarker discovery in many diseases, including cancer.

Role of Structure-Based Changes due to Somatic Mutation in Highly Homologous DNA-Binding and DNA-Hydrolyzing Autoantibodies Exemplified by A23P Substitution in the VH Domain

Anti-DNA autoantibodies are responsible for tissue injury in lupus. A subset of DNA-specific antibodies capable of DNA cleavage can be even more harmful after entering the living cells by destroying nuclear DNA. Origins of anti-DNA autoantibodies are not fully understood, and the mechanism of induction of DNA-cleaving activity remains speculative. The autoantibody BV04-01 derived from lupus-prone mouse is the only DNA-hydrolyzing immunoglobulin with known 3D structure. Identification and analysis of antibodies homologous to BV04-01 may help to understand molecular bases and origins of DNA-cleaving activity of autoantibodies. BLAST search identified murine anti-DNA autoantibody MRL-4 with sequences of variable region genes highly homologous to those of autoantibody BV04-01. Despite significant homology to BV04-01, not only MRL-4 had no DNA-cleaving activity, but also reversion of its unusual P23 mutation to the germline alanine resulted in a dramatic loss of affinity to DNA. Contrary to this effect, transfer of the P23 mutation to the BV04-01 has resulted in a significant drop in DNA binding and almost complete loss of catalytic activity. In the present paper we analyzed the properties of two homologous autoantibodies and mutants thereof and discussed the implications of unusual somatic mutations for the development of autoantibodies with DNA-binding and DNA-hydrolyzing activity.

Simultaneous positivity for anti-DNA, anti-nucleosome and anti-histone antibodies is a marker for more severe lupus nephritis

OBJECTIVE

The purpose of this study is to examine autoantibody profile of systemic lupus erythematosus (SLE) patients with lupus nephritis (LN) and to establish the correlation between the antibody reactivity and disease activity of LN.

METHODS

Autoantibodies and serological parameters were measured and analyzed in 589 SLE patients. The associations of the co-positivity of anti-dsDNA, -nucleosome and -histone antibodies (3-pos) with clinical, serological and outcome parameters were analyzed.

RESULTS

At the study entry, the prevalence for anti-dsDNA (61.52 % vs. 34.11 %, P < 0.0001), anti-nucleosome (56.09 % vs. 37.21 %, P = 0.0002) and anti-histone (49.35 % vs. 33.33 %, P = 0.0013) antibodies in patients with LN were significantly higher than that in patients without LN. Patients with 3-pos had a higher proportion of proliferative renal lesions (class III + IV). The incidence of a poor renal outcome (7.14 % vs. 2.52 %, P = 0.0174) in LN patients with 3-pos was significantly higher than those without 3-pos. Moreover, the rate of remission (73.63 % vs. 82.37 %, P = 0.0245) was significantly reduced and recurrence increased (58.90 % vs. 23.44 %, P < 0.0001) in 3-pos patients as compared to that in non 3-pos within the LN group.

CONCLUSION

Our data indicate a strong association between the 3-pos and renal disease activities, especially proliferative glomerulonephritis. The ability of 3-pos to predict renal flares may lead to major additional benefits in the follow-up of these patients.