Polyanions inhibit the binding of autoantibodies with some cellular proteins

Effect of polyanions on reaction of the Ig from sera of patients with systemic lupus erythematosus and scleroderma with cellular proteins was studied by immunoblotting. It has been shown that dextran sulfate, heparin, denatured DNA and poly I inhibited the binding of autoantibodies with some polypeptides. The molecular weight of these antigens was determined. The molecular mechanism of immunological reactions studied and it's role in pathogenesis of autoimmune diseases is discussed.     

Detection of autoantibodies against phenylalanyl-, tyrosyl-, and tryptophanyl-tRNA-synthetase and anti-idiotypic antibodies to it in serum from patients with autoimmune diseases]

Sera of patients bearing autoimmune diseases (rheumatoid arthritis and systemic lupus erythematosus) and sera of clinically healthy donors were examined by ELISA for the presence of autoantibodies against tryptophanyl-, tyrosyl- and phenylalanyl-tRNA synthetases. Pure bovine synthetases served as antigens. It was shown that in patients with both autoimmune diseases all three enzyme autoantibodies were revealed at serum dilution 1/1600-1/3200. Moreover, by means of monoclonal antibodies against the same enzymes used for immunoaffinity sorption, antiidiotypic antibodies of IgG type against autoantibodies were detected. A conclusion has been made that autoimmune diseases are characterized by autoimmune response for many aminoacyl-tRNA synthetases irrespectively of their quaternary structure, intracellular location etc both at the level of primary and secondary antibodies.     

The use of post‐translationally modified peptides for detection of biomarkers of immune‐mediated diseases

Biomarkers are decision‐making tools at the basis of clinical diagnostics and essential for guiding therapeutic treatments. In this context, autoimmune diseases represent a class of disorders that need early diagnosis and steady monitoring. These diseases are usually associated with humoral or cell‐mediated immune reactions against one or more of the body's own constituents. Autoantibodies fluctuating in biological fluids can be used as disease biomarkers and they can be, thus, detected by diagnostic immunoassays using native autoantigens. However, it is now accepted that post‐translational modifications may affect the immunogenicity of self‐protein antigens, triggering an autoimmune response and creating neo‐antigens. In this case, post‐translationally modified peptides represent a more valuable tool with respect to isolated or recombinant proteins. In fact, synthetic peptides can be specifically modified to mimic neo‐antigens and to selectively detect autoantibodies as disease biomarkers. A ‘chemical reverse approach’ to select synthetic peptides, bearing specific post‐translational modifications, able to fishing out autoantibodies from patients' biological fluids, can be successfully applied for the development of specific in vitro diagnostic/prognostic assays of autoimmune diseases. Herein, we report the successful application of this approach to the identification of biomarkers in different autoimmune diseases, such as systemic lupus erythematosus, rheumatoid arthritis and multiple sclerosis. Copyright © 2009 European Peptide Society and John Wiley & Sons, Ltd.     

Features of autoantigens

The major cellular antigens recognized by autoantibodies in SLE and other systemic autoimmune diseases have been identified and characterized over the past 25 years. The pioneering studies of Eng Tan demonstrate the importance of autoantibodies as diagnostic markers. However, why certain autoantibodies, such as anti-Sm, are pathognomonic of SLE, while others are markers of othe autoimmune disease subsets, remains unanswered. This central question continues to drive much current research into the pathogenesis of SLE. Features of the autoantigens recognized by autoantibodies may provide important clues to the causes of lupus. Most autoantigens in systemic autoimmunity are multicomponent nucleoprotein complexes. These particles are encountered by the immune system as units, resulting in the tandem production of autoantibodies recognizing several components of the same complex. However, the intermolecular-intrastructural spreading of autoimmunity is regulated by mechanisms that at present are defined poorly. Also unexplained is the observation that the antigenic determinants recognized by autoantibodies are restricted and frequently correspond to active sites or functional domains. Analysis of experimental models of autoimmunity suggests that altering the structure of autoantigens, due to abnormal protein-protein interactions, hapten binding, altered degradation, or other mechanisms, could help to explain both the restricted patterns of autoantibody spreading and the selective targeting of antigenic sites. This may be a worthwhile area for further investigation of the pathogenesis of systemic autoimmune diseases.Abbreviations MCTD mixed connective tissue disease - PM/DM polymyositis / dermatomyositis - SLE Systemic lupus erythematosus - SSc systemic sclerosis - SVT simian virus 40 large T antigen     

RNA recognition by autoantigens and autoantibodies

The La, Ro, Sm and RNP autoantigens have been intensely studied over the past decade since cDNAs encoding autoantigens have become available. Most of these autoantigens are closely associated with RNA in RNP particles and molecular studies have provided insights into their modes of recognition and binding to RNA. For example, a common RNA Recognition Motif (RRM) was found to be a critical component of the RNA-binding domain of these autoantigens and the three dimensional structure of the RRM has been solved. As described in other articles in this series, the presence of La, Ro, Sm and RNP autoantibodies correlates with disease subsets, such as Sjogren's syndrome, systemic lupus erythematosus and other connective tissue diseases. Immunological analysis of sera from autoimmune patients using recombinant autoantigens has revealed that multiple epitopes reside along the proteins and these represent both continuous and discontinuous (conformational) autotopes. Findings to date support a model of autoantibody induction which involves the direct presentation of proteinaceous autoantigens to the immune system. Circumstantial evidence has suggested that immunological crossreactivity between systemic autoantigens and structural components of infectious agents may play an initial role in the autoimmune response to certain antigens. However, the etiology of autoimmune diseases is probably multifactoral with genetic and other immune features acting on the organismal level. In addition, RNA molecules themselves can be autoantigens with higher order structural conformations which are recognized by RNP-type autoantibodies. Immune crossreactivity and/or direct presentation may generate autoantibodies reactive with conformational RNA epitopes. If crossreactivity with components of cellular or infectious agents give rise to RNA epitopes, they may represent structural or functional mimetics of the primary epitopes that actually drive the response. These ideas are discussed with respect to the role of mimetic processes in molecular recognition during autoimmunity.     

Autoantibodies from an SLE patient immunostain the Barr body

To identify specific autoimmune disorders that produce autoantibodies against the mammalian Barr body, sera from 185 autoimmune patients were screened using indirect immunofluorescence on human fibroblasts. Serum from a patient with systemic lupus erythematosus immunostained epi- topes concentrated at the Barr body in female fibroblasts. Such autoantibodies provide a novel tool for characterization of Barr body composition and structure.     

Patients with Systemic Lupus Erythematosus Have Higher Prevalence of Thyroid Autoantibodies: A Systematic Review and Meta-Analysis

Background

Thyroid autoimmunity is considered the most common type of organ-specific autoimmune disorder and can be associated with other autoimmune endocrine disorders or non-endocrine diseases. Systemic lupus erythematosus is a prototypical autoimmune disorder with multifactorial etiology. The pathogenesis and development of the disease may result from a loss of immune tolerance and the resulting synthesis of autoantibodies against nuclear antigens. Autoimmune factors may be common features of both thyroid autoimmunity and systemic lupus erythematosus, making it likely that both conditions may coexist within some patients.

Methods and Findings

A number of studies have investigated whether an association between thyroid autoimmunity and systemic lupus erythematosus exists. However, the results of these studies have been inconsistent. Furthermore, most of these studies have had relatively small sample sizes, which have rendered them insufficiently powerful to determine whether there is an association between systemic lupus erythematosus and thyroid autoimmunity. The main objective of this meta-analysis is to provide reliable estimates of the extent of any association between thyroid autoimmunity and systemic lupus erythematosus by combining the primary data from all relevant studies. Literature databases were searched, including the Medline, Embase, Web of Science, Chinese Wanfang and CBM databases, from January 1970 to May 2014. A total of 1076 systemic lupus erythematosus cases and 1661 healthy controls were included in this study. From these data, the odds ratio (OR) and the corresponding 95% confidence interval (95% CI) were calculated. The meta-analysis results showed that the prevalence of thyroid autoantibody positivity in patients with systemic lupus erythematosus was higher than in healthy controls (TgAb: OR = 2.99, 95% CI = 1.83–4.89; TPOAb: OR = 2.20, 95% CI = 1.27–3.82, respectively).

Conclusion

The results of this meta-analysis suggest that thyroid autoimmunity is more prevalent in patients with systemic lupus erythematosus than in a control group.     

Antinuclear antibody-keratinocyte interactions in photosensitive cutaneous lupus erythematosus

Autoimmune diseases are characterized by various circulating autoantibodies, especially antinuclear antibodies (ANA). It has been a long-standing issue as to whether and/or how ANA interact with epidermal cells to produce skin lesions. Of these ANA, the anti-SS-A/Ro antibody is the most closely associated with photosensitivity in patients with systemic lupus erythematosus (SLE) and its subgroups, including subacute cutaneous lupus erythematosus (SCLE) and neonatal lupus erythematosus (NLE). SS-A/Ro antigens are present in the nucleus and cytoplasm, and interestingly, ultraviolet B (UVB) light translocates these antigens to the surface of the cultured keratinocytes. Thus, anti-SS-A/Ro antibodies in the sera can bind to the relevant antigens expressed on the UVB-irradiated keratinocyte surface, and have been speculated to be an important inducer of antibody-dependent keratinocyte damage. This interaction between the anti-SS-A/Ro antibodies and UVB-irradiated keratinocytes may induce the skin lesions through a cytotoxic mechanism. This review will focus on the involvement of antibody-dependent cellular cytotoxicity in the pathogenesis of the skin lesions observed in photosensitive cutaneous lupus erythematosus.     

Use of synthetic peptides for the detection and quantification of autoantibodies

Summary and conclusions The rapid progress made over the last 10 years in the identification of individual autoantigens and in the localization of the epitopes involved, has resulted in a parallel reduction in the complexity of the antigen required for the detection of autoantibodies. The ability to use synthetic peptides as antigens is a remarkable culmination of this process considering that many antigenic particles contain multiple proteins (eg. Sm consist of 8 or more individual proteins).Despite the fact that patients with SLE have a polyclonal hypergammaglobulinemia, excellent correlations between ELISAs utilizing the P2 or SmB/B synthetic peptides, ELISAs utilizing r proteins and immunoblotting were obtained [28, 38, 50]. However, false positive/non-specific binding to a P2-BSA-glutaraldehyde conjugate has been observed with serum from old MRL/lpr mice (unpublished observations). In addition, some of the results obtained in human autoimmune diseases suggest that non-specific binding may be problematic in some instances. It is difficult, at present, to know whether the higher frequencies of detection of autoantibodies to certain synthetic peptide antigens reflect increased sensitivity or decreased specificity.Synthetic peptide antigens have beeen used to detect autoantibodies in both organ specific and multisystem autoimmune diseases. In only a small number of cases have these reagents been rigorously tested for sensitivity and specificity. Despite this, synthetic peptides have been shown to be valuable for detection and quantification of autoantibodies in certain clinical situations. Undoubtedly, further progress in epitope mapping of autoantigens coupled with technological advances in protein synthesis and improved prediction of protein structure will lead to a large number of synthetic peptide antigens for research and clinical applications. It is unlikely that short synthetic peptides will substitute for native proteins in all instances since some autoantibodies show a striking preference for conformational epitopes.Abbreviations r recombinant - SLE systemic lupus erythematosus     

Human monoclonal multiple-organ-reactive autoantibodies distinguished by mouse monoclonal anti-idiotypic antibodies: expression of idiotopes in humans with and without autoimmune diseases

Previously we reported on the production and characteristics of a number of human monoclonal autoantibodies. All of these autoantibodies were of the IgM class and reacted with antigens in multiple organs. In this study we generated IgG murine monoclonal anti-idiotypic antibodies against five human monoclonal autoantibodies, (i.e., MOR-h2, MOR-h3, MOR-h4, CG1, and CG2). These anti-idiotypic antibodies reacted strongly with the corresponding human monoclonal autoantibody, but minimally or not at all with other human monoclonal autoantibodies. By using these anti-idiotypic antibodies as probes, we screened sera obtained from normal individuals and patients with insulin-dependent diabetes mellitus, Hashimoto's thyroiditis, and systemic lupus erythematosus for the expression of idiotopes. Our study showed that the idiotopes recognized by three of the anti-idiotypic antibodies, i.e., anti-CG1, anti-CG2, and anti-MOR-h2, were not expressed, but the idiotopes recognized by two of the anti-idiotypic antibodies, i.e., anti-MOR-h3 and anti-MOR-h4, were expressed in normal individuals. In patients with autoimmune disorders, there was no increase in the expression of the CG1, CG2, and MOR-h2 idiotopes, but 45 and 23% of the patients with systemic lupus erythematosus showed a significant increase in the expression of the MOR-h3 and MOR-h4 idiotopes respectively. These findings show that there is widespread expression in the B cell repertoire of certain autoantibody-associated idiotopes.     

Inhibition of caspase-3-mediated poly(ADP-ribose) polymerase (PARP) apoptotic cleavage by human PARP autoantibodies and effect on cells undergoing apoptosis

Autoantibodies directed to nuclear antigens are serological hallmarks of autoimmune rheumatic diseases such as systemic lupus erythematosus. Although much more is known about the molecular identity and functions of targeted self-antigens, with few exceptions, evidence that autoantibodies to these targets have a particular function and contribute directly to the pathological process is lacking. Here we show that human autoantibodies reacting with the zinc fingers of poly(ADP-ribose) polymerase involved in the recognition of damaged DNA totally prevent the cleavage of poly(ADP-ribose) polymerase by caspase-3, a process that normally occurs during early apoptosis. Furthermore, these antibodies, which are frequent in certain autoimmune rheumatic and bowel diseases, affect the characteristic features of apoptosis and increase cell survival ex vivo. This new observation is important, because failure to remove autoimmune or abnormal cells can give rise to prolonged autoimmune stimulation and tumor formation.     

Genetic susceptibility to autoimmune disorders: clues from gene association and gene expression studies

Susceptibility to autoimmune disorders results from the interaction of multiple genetic factors that regulate the threshold of autoreactivity. Genome-wide microsatellite screens and large-scale single nucleotide polymorphism (SNP) association studies have identified chromosomal loci that are associated with specific disorders including systemic lupus erythematosus, rheumatoid arthritis, juvenile arthritis, multiple sclerosis, and diabetes. Numerous candidate gene association studies have in turn investigated the association of specific genes within these chromosomal regions, with susceptibility to autoimmune diseases (e.g. FcgammaReceptors, TYK2 and systemic lupus). More recently, large-scale differential gene expression studies performed on selected tissues from patients with autoimmune disorders, have led to the identification of gene signatures associated with the activation of specific pathways in these diseases (e.g. interferon signature in lupus). In the future, integrated analyses of gene (and protein) expression together with SNP data will allow us to sketch an intelligible picture of the genesis of autoimmunity in humans. This review sets out to illustrate how the most recent advances in the field of systemic lupus erythematosus, rheumatoid arthritis and juvenile arthritis have led to a better understanding of these disorders.     

The role of Toll-like receptors in chronic inflammation

The role of Toll-like receptors (TLRs) in innate immunity and their ability to recognise microbial products has been well characterised. TLRs are also able to recognise endogenous molecules which are released upon cell damage and necrosis and have been shown to be present in numerous autoimmune diseases. Therefore, the release of endogenous TLR ligands during inflammation and consequently the activation of TLR signalling pathways may be one mechanism initiating and driving autoimmune diseases. An increasing body of circumstantial evidence implicates a role of TLR signalling in systemic lupus erythematosus (SLE), atherosclerosis, asthma, type 1 diabetes, multiple sclerosis, bowl inflammation and rheumatoid arthritis (RA). Although at present their involvement is not comprehensively defined. However, future therapies targeting individual TLRs or their signalling transducers may provide a more specific way of treating inflammatory diseases without global suppression of the immune system.     

益生菌对自身免疫病的作用及机制研究现状

自身免疫病是机体免疫功能紊乱而导致组织器官受损的一类疾病,包括类风湿关节炎、系统性红斑狼疮、多发性硬化症、自身免疫性肝炎等。糖皮质激素及免疫抑制剂是治疗自身免疫病的常用药物,但长期使用会产生代谢紊乱、免疫低下、继发感染等副作用。随着肠道菌群与自身免疫病相关研究的进展,益生菌干预自身免疫病成为一大研究热点。研究证实,益生菌缓解自身免疫病安全有效,有望成为辅助疗法甚至替代疗法。本文就益生菌缓解类风湿关节炎、系统性红斑狼疮、多发性硬化症、自身免疫性肝炎等的作用及相关机制进行综述。     

Fcgamma receptors in the initiation and progression of systemic lupus erythematosus

Systemic lupus erythematosus, a systemic autoimmune disorder, is characterized by the production of autoantibodies to nuclear constituents and inflammatory lesions in multiple organ systems. Although the pathogenesis of the disease is largely unknown, recent studies have suggested that disturbances in apoptosis and/or clearance of apoptotic cells may play an important role in the induction and perpetuation of autoantibody production. When autoantibodies subsequently complex to autoantigens present on apoptotic cells, ligation of Fcgamma receptor will result in inflammation and disease development. Indeed, mice deficient in activating Fcgamma receptors were protected against inflammation in models of immune complex-mediated autoimmune disease, whereas deletion of the inhibitory Fcgamma receptors increased autoantibody production and susceptibility to immune complex-induced inflammation. Additionally, functional polymorphisms in Fcgamma receptors were shown to be associated with development of human systemic lupus erythematosus. This review focuses on the role of Fcgamma receptors in the initiation of autoantibody production, inflammatory handling of immune complexes, and disease development in systemic lupus erythematosus.     

Molecular and structural properties of three autoimmune IgG monoclonal antibodies to histone H2B

In systemic autoimmune diseases such as lupus the immune system produces autoantibodies to nuclear antigens including DNA and histone molecules. In the present study, we describe three monoclonal IgG antibodies that have been obtained from lupus-prone MRL/lpr mice. These three antibodies react with the amino terminus of histone H2B, a region of the molecule that is accessible in chromatin. Using a series of overlapping H2B synthetic peptides and structural analogues, we have mapped the different epitopes recognized by these antibodies. We have also sequenced the combining sites (variable regions) of the antibodies and modeled their interactions with the corresponding epitopes. Overall, the data suggest that the mechanisms of interaction with antigen are different for each of the three antibodies, even though they all react with the amino-terminal domain of the histone H2B molecule. The results also suggest that the binding between these antibodies and histone H2B is different from that between most antibodies and conventional protein antigens since the heavy chain complementarity-determining region 3 appears to play only a limited role in the three antibodies tested. The study of the interaction between self-antigens and spontaneously occurring autoantibodies may help us elucidate the mechanisms driving the expansion of self-reactive lymphocytes.     

Spinal cord injury triggers systemic autoimmunity: evidence for chronic B lymphocyte activation and lupus-like autoantibody synthesis

Clinical and experimental data indicate that spinal cord injury (SCI) elicits pathological T-cell responses. Implicit in these data, but poorly understood, is that B lymphocytes (B cells) also contribute to the delayed pathophysiology of spinal trauma. Here, for the first time, we show that experimental spinal contusion injury elicits chronic systemic and intraspinal B cell activation with the emergence of a B cell-dependent organ-specific and systemic autoimmune response. Specifically, using sera from spinal cord injured mice, immunoblots reveal oligoclonal IgG reactivity against multiple CNS proteins. We also show SCI-induced synthesis of autoantibodies that bind nuclear antigens including DNA and RNA. Elevated levels of anti-DNA antibodies are a distinguishing feature of systemic lupus erythematosus and, via their ability to cross-react with neuronal antigens, can cause neuropathology. We show a similar pathologic potential for the autoantibodies produced after SCI. Thus, mammalian SCI produces marked dysregulation of B cell function (i.e. autoimmunity) with pathological potential.     

Human RNA helicase A is a lupus autoantigen that is cleaved during apoptosis

Proteolytic cleavage by caspases is the central event in cells undergoing apoptosis. Cleaved proteins are often targeted by autoantibodies, suggesting that the cleavage of self Ags enhances immunogenicity and is prone to induce an autoimmune response. We found autoantibodies that immunoprecipitated a 140-kDa RNA-associated protein, provisionally designated Pa, in 11 of 350 patient sera that were positive for antinuclear Abs in an immunofluorescence test. The Pa protein gave rise to three fragments with m.w. ranging from 120-130 kDa during anti-Fas-activated apoptosis. Pure caspase-3 cleaved the Pa protein into a 130-kDa fragment corresponding to the largest of these three products. Peptide sequence analysis of a tryptic digest from immunoaffinity-purified Pa showed 100% identity to human RNA helicase A (RHA). The identity of Pa with RHA was further confirmed by immunoblotting with rabbit anti-RHA Ab using anti-Pa immunoprecipitates as substrates. All 10 anti-RHA-positive patients who were clinically analyzed were diagnosed as having systemic lupus erythematosus, and 7 of them had lupus nephritis. RHA is a multifunctional protein with roles in cellular RNA synthesis and processing. Inactivation of RHA by cleavage may be an important part of the process leading to programmed cell death. The cleaved RHA fragments that are produced during apoptosis may trigger an autoimmune response in systemic lupus erythematosus.     

Studies on precipitating and hemagglutinating antibodies in systemic lupus erythematosus

We studied the precipitating and hemagglutinating autoantibodies in the sera of patients with various connective tissue diseases in general and lupus in particular. Saline soluble extract of goat thymus had adequate antigenic materials as compared to other organs. Twenty per cent of patients with systemic lupus erythematosus were positive for precipitating autoantibodies by immunodiffusion and 44% by counterimmunoelectrophoresis. Normal human subjects, nonrheumatic disease patients and patients with rheumatoid arthritis and progressive systemic sclerosis were all negative. Forty seven per cent of positive systemic lupus erythematosus sera showed two precipitin systems. Enzyme sensitivities were used as the basis of identification of most of the antigenic specificities. Passive hemagglutination was carried out to identify antibodies to non-histone nuclear protein and nuclear ribonucleo-protein antigens. Thirty eight % of systemic lupus erythematosus patients were positive by this technique. Passive hemagglutination although a highly sensitive technique could not detect antibodies against antigenic systems other than non-histone nuclear protein and nuclear ribonucleoprotein.     

Autoantibodies to components of the mitotic apparatus

Autoantibodies directed to a variety of cellular antigens and organelles are a feature of autoimmune diseases. They have proven useful in a clinical setting to establish diagnosis, estimate prognosis, follow disease progression, alter therapy, and initiate new investigations. Cellular and molecular biologists have used autoantibodies as probes to identify molecules involved in key cellular processes. One of the most interesting sets of autoantibodies are those that target antigens within the mitotic apparatus (MA). The MA includes chromosomes, spindle microtubules and centrosomes. The identification, localization, function, and clinical relevance of MA autoantigens is the focus of this review. Abbreviations: ATP – adenosine triphosphate; CENP – centromere protein; CREST – calcinosis, Raynaud's phenomenon, esophageal dysmotility, sclerodactyly, telangiectasia; HMG – high mobility group; IB – intercellular bridge; IIF – indirect immunofluorescence; MAPs – microtubule associated proteins; NuMA – nuclear mitotic apparatus; NOR – nucleolar organizer; PBC – primary biliary cirrhosis; PM – polymyositis; Pol I, II, III – RNA polymerases; RA-rheumatoid arthritis; SLE – systemic lupus erythematosus; SS – Sjögren's syndrome; SSc – systemic sclerosis; topo – topoisomerase.