Autoantibodies in systemic sclerosis

Emerging roles of SnoRNAs in the pathogenesis and treatment of autoimmune disorders

SnoRNAs (small non-coding RNAs) have recently gained prominence in autoimmune diseases, revealing their crucial role in modulating the immune response and contributing to disease pathogenesis. Initially known for their involvement in ribosomal RNA processing and modification, molecular biology and genomics advancements have uncovered their broader impact on cellular function, especially in autoimmune disorders. Autoimmune diseases represent conditions characterized by the immune system's erroneous attacks on self-tissues, encompassing disorders like systemic lupus erythematosus, rheumatoid arthritis, and multiple sclerosis. The complex etiology of these conditions involves a delicate interplay of genetic and environmental factors. Emerging evidence suggests that snoRNAs initially recognized for their housekeeping roles, extend their influence on immune regulation through diverse mechanisms. SnoRNAs have been implicated in epigenetic modification, directly affecting the gene expression profiles of immune cells. Their ability to guide site-specific changes on ribosomal RNAs and other non-coding RNAs can significantly influence the translation of proteins involved in immune response pathways. Moreover, snoRNAs interact with key immune-related proteins, modulating their functions and subsequently impacting immune cell development, activation, and tolerance. Dysregulation of snoRNA expression has been observed in various autoimmune diseases, underscoring their potential as biomarkers for disease diagnosis, prognosis, and therapeutic targets. Manipulating snoRNA expression or activity is a promising therapeutic intervention avenue, offering the potential for personalized treatment strategies in autoimmune diseases. However, there remains a need for comprehensive research efforts to elucidate the precise molecular mechanisms underlying snoRNA-mediated immune modulation. Further investigations in this domain are essential to unravel the potential of snoRNAs in autoimmune disorders.

Autoreactive B cell responses targeting nuclear antigens in systemic sclerosis: Implications for disease pathogenesis

A hallmark of disease pathogenesis of systemic sclerosis (SSc) is the presence of autoreactive B cell responses targeting nuclear proteins. Almost all SSc-patients harbour circulating antinuclear autoantibodies of which anti-topoisomerase 1, anti-centromere protein, anti-RNA polymerase III and anti-fibrillarin autoantibodies (ATA, ACA, ARA and AFA, respectively) are the most common and specific for SSc. In clinical practice, autoantibodies serve as diagnostic biomarkers and can aid in the identification of clinical phenotypes of the disease. However, factors driving disease progression in SSc are still poorly understood, and it is difficult to predict disease trajectories in individual patients. Moreover, treatment decisions remain rather empirical, with variable response rates in clinical trials due to patient heterogeneity. Current evidence has indicated that certain patients may benefit from B cell targeting therapies. Hence, it is important to understand the contribution of the antinuclear autoantibodies and their underlying B cell response to the disease pathogenesis of SSc.

Combinations of scleroderma hallmark autoantibodies associate with distinct clinical phenotypes

Systemic sclerosis (SSc) is characterized by the presence of SSc-specific or SSc-associated antibodies (SSc-Abs): anti-topoisomerase I (ATA), anti-centromere (ACA), anti-RNA polymerase III (ARA), anti-U3RNP (U3RNP), anti-U1RNP (U1RNP), anti-PmScl (PmScl), anti-Ku (Ku) and anti-Th/To (Th/To), each being associated with specific clinical features and prognosis. The detection of more than one SSc-Abs in SSc patients is rare and only few data about these patients' clinical phenotype is available. The aim of our study was to evaluate the frequency and the disease's features associated with the presence of > 1 SSc-Abs positivity in a large cohort of SSc patients. The autoantibody profiles of 2799 SSc patients from February 2001 to June 2017 were retrospectively reviewed. Patients with > 1 SSc-Abs were identified. Clinical features were collected and compared to a large historical cohort of SSc patients with single SSc-Ab positivity. SSc patients were excluded if previously treated with rituximab, intravenous immunoglobulins or stem cell transplantation. Non-parametric tests were used for statistical analysis. Nearly 5% of SSc patients from our cohort had ≥ 2 autoantibody positivity, and 2.3% (n = 72) had ≥ 2 SSc-Abs positivity. Th e most common combination was U1RNP and ATA (35%). These patients were younger than patients with single autoantibody positivity and showed more commonly a diffuse cutaneous SSc form. They also had higher rates of overlap features compared to ATA patients. Other combinations included U1RNP and ACA (13%), ATA and ACA (7%) and U1RNP and PmScl (5%). In our study we observed that, while infrequently, SSc patients can present with a combination of two SSc-Abs and that the double positivity can influence their clinical phenotype compared to patients with single SSc-Ab positivity. The importance of re-testing SSc-Abs in patients with changing clinical phenotypes was also highlighted, as this may confer a differing risk stratification.

The management of autoimmunity in patients with cholestatic liver diseases

Cholestatic liver diseases are rare diseases that often lead to cirrhosis and its consequent complications. In addition to liver-related morbidity, patients with cholestatic liver diseases often suffer from autoimmune diseases that affect several organs and tissues. The robust and efficient data collection and collaboration between hepatologists and rheumatologists have led to significant advancements in understanding the relationship between the cholestatic liver diseases and associated autoimmune diseases. In this paper, we discuss the cholestatic liver diseases (primary biliary cirrhosis, primary sclerosing cholangitis and immunoglobulin G4 associated cholangitis) and associated autoimmune diseases.

Primary biliary cirrhosis: What do autoantibodies tell us?

Primary biliary cirrhosis (PBC) is a chronic, progressive, cholestatic, organ-specific autoimmune disease of unknown etiology. It predominantly affects middle-aged women, and is characterized by autoimmune-mediated destruction of small- and medium-size intrahepatic bile ducts, portal inflammation and progressive scarring, which without proper treatment can ultimately lead to fibrosis and hepatic failure. Serum autoantibodies are crucial tools for differential diagnosis of PBC. While it is currently accepted that antimitochondrial antibodies are the most important serological markers of PBC, during the last five decades more than sixty autoantibodies have been explored in these patients, some of which had previously been thought to be specific for other autoimmune diseases.

Methods to detect antifibrillarin antibodies in patients with systemic sclerosis (SSc): a comparison

Autoantibodies against nucleolar antigens are common in systemic sclerosis (SSc). They include autoantibodies against fibrillarin (Fb), which are serological markers for SSc. Fb is associated with the evolutionally-conserved box C/D of small nucleolar RNAs (snoRNAs). We compared indirect immunofluorescence (IIF), Western blot (WB), and immunoprecipitation (IPP) of total small RNAs assays to determine which of these techniques is most specific for the detection of snoRNPs. We also examined the frequency and specificity of autoantibodies from SSc patients to snoRNAs, snRNAs, and scRNAs, and concluded that 1) IIF can not determine autoantibody specificity against Fb, 2) 36% of SSc sera were false-negative by WB, and 3) by IPP, anti-Fb autoantibodies from SSc patients can bind U3, U8, U13, U15, and U22 snoRNAs.

Combining EL4-B5-based B-cell stimulation and phage display technology for the successful isolation of human anti-Scl-70 autoantibody fragments

Scl-70 is the major antigen recognised by autoantibodies in the sera of patients with systemic sclerosis (SSc). The autoantibodies that specifically react with Scl-70 are highly characteristic of the disease and represent valuable markers for the diagnosis of SSc. We describe a novel strategy for cloning autoantibody fragments starting with a small blood sample from an SSc patient. B cells isolated from the collected peripheral blood mononuclear cells (PBMCs) were cultured in vitro using the EL4-B5 system. Anti-Scl-70 IgG-producing cells were pooled for RNA preparation followed by the generation of phagemid libraries of approximately 10(7) independent single-chain Fvs (scFvs). The screening of these libraries by phage display allowed us to isolate four anti-Scl-70 scFvs following three rounds of biopanning. About 10 times more starting blood material was needed to generate scFv libraries of similar size from PBMCs of an SSc patient and only two anti-Scl-70 scFvs were isolated after three rounds of phage selection. Together, this work shows that functional autoantibody fragments can be advantageously cloned after in vitro expansion of B cells. The isolated anti-Scl-70 autoantibody fragments represent useful tools for calibrating SSc diagnostic assays.

Coexistence of antitopoisomerase I and anticentromere antibodies in patients with systemic sclerosis

BACKGROUND

Antibodies targeting DNA topoisomerase I (ATA) or centromere proteins (ACA) are associated with clinical subsets of patients with systemic sclerosis (SSc). The occurrence of those autoantibodies is considered to be mutually exclusive.

OBJECTIVE

To describe the clinical and immunogenetic data of three patients who are co-expressing both antibodies, and then review previous publications.

METHODS

Both antibodies were detected by different methods, including indirect immunofluorescence technique, enzyme linked immunosorbent assay, immunodiffusion, and immunoblot. Patients were HLA typed by serological and molecular genetic methods. Data were extracted from published reports for comparison. The search for published studies was through Medline and other database research programmes.

RESULTS

During routine laboratory diagnostics over several years three patients with scleroderma and coincidence of ATA and ACA were identified: patient 1 with diffuse SSc, Raynaud's phenomenon, puffy fingers and fingertip necrosis, contractures, and calcinosis; patient 2 with diffuse SSc, Raynaud's phenomenon, oedema of the hands, and interstitial calcinosis of hands, knees, and shoulders, and pulmonary fibrosis; patient 3 with scleroderma of hands, forearms, and face, Raynaud's phenomenon, puffy fingers, finger contractures, fingertip necrosis, and calcinosis. All three patients studied were carriers of HLA alleles known to be associated with these autoantibodies. In serial measurements the concentrations of the two antibodies showed independent or even reverse fluctuations. Screening of 100 patients with ACA for ATA and vice versa disclosed no further patients with coincidence of these antibodies. Twenty eight cases of ACA/ATA coexistence in 5423 patients (0.52%) with SSc or SSc associated symptoms were found in an analysis of published studies.

CONCLUSION

The expression of ATA and ACA is not totally mutually exclusive, but coincidence is rare (<1% of patients with SSc). Patients with both autoantibodies often have diffuse scleroderma and show immunogenetic features of both antibody defined subsets of SSc.

Anti-topoisomerase I (anti-Scl-70) antibodies in patients with systemic lupus erythematosus

OBJECTIVE

To investigate the presence and clinical significance of anti-Scl-70 antibodies in patients with systemic lupus erythematosus (SLE).

METHODS

Levels of antibodies against Scl-70 were determined by a commercial clinical enzyme-linked immunosorbent assay (ELISA) during routine evaluation. Results were verified by an additional ELISA with a characterized bovine Scl-70, by ELISA with a recombinant human topoisomerase I, by Western blot, and by double diffusion in agar gel. Disease activity was estimated retrospectively by the Systemic Lupus Activity Measure (SLAM).

RESULTS

Of 128 consecutive SLE patients, 25% were positive for anti-Scl-70 antibody; this antibody activity was cognate in nature. No SLE patient could be classified as also having systemic sclerosis. The levels of anti-Scl-70 were significantly correlated with the SLAM score for the entire cohort (r = 0.563, P < 0.001) and for 7 individual patients with multiple longitudinal measurements (r = 0.755-0.951, P < 0.001; n = 6) (r = 0.378, P < 0.05; n = 1). A significant correlation was also found between the levels of anti-Scl-70 and anti-double-stranded DNA antibodies (r = 0.558, P < 0.001). Patients with anti-Scl-70 had significantly higher risk of pulmonary hypertension (P < 0.01) and renal involvement (P < 0.001) than patients without this antibody.

CONCLUSION

Anti-Scl-70 antibody is present in a significant subset of patients with SLE. For this subset, it offers a good correlate of disease activity and suggests increased risk for pulmonary hypertension and nephritis.

Diversity and plasticity of the anti-DNA topoisomerase I autoantibody response in scleroderma

OBJECTIVE

To examine domain recognition by anti-DNA topoisomerase I (anti-DNA topo I, or anti-topo I) antibodies over time in scleroderma patients.

METHODS

Serial serum samples from scleroderma patients with known reactivity to Scl-70, a 70-kd topo I breakdown product, were tested by immunoblot for IgM, IgG, IgA, kappa, and lambda reactivity to Scl-70 and 8 overlapping recombinant peptide fragments (F1-F8) that span the human topo I molecule.

RESULTS

IgM, IgG, kappa, and lambda anti-topo I antibodies in both early-disease and late-disease serum samples preferentially recognized the Scl-70 molecule rather than the F1-F8 peptides, suggesting preferential recognition of conformational determinants on Scl-70 throughout the disease course. Amounts of both primary and secondary anti-topo I antibodies to Scl-70 varied over time, including increases in primary antibody responses late in the disease course. Striking variability in recognition of the F1-F8 peptides by IgM, IgG, IgA, kappa, and lambda anti-topo I antibodies was seen in serial samples. Most often, the change in FI-F8 recognition from one sample to the next was unpredictable, although occasionally patterns of antibody recognition were reciprocal in serial samples. Of note, in several patients, what could have been interpreted as domain spreading among F1-F8 in 2 successive samples was just a part of changing antibody reactivity to these peptides that again became more restricted in a third sample.

CONCLUSION

Titers and immunodominant domains recognized by both primary and secondary anti-topo I antibodies are highly variable over time. This suggests continual antigen presentation and regulation of the anti-topo I antibody response in scleroderma, even late in the disease course.

Centrosome proteins: a major class of autoantigens in scleroderma

Autoantibodies to intracellular antigens are a hallmark of autoimmune diseases, although their role in disease pathogenesis is unclear. Centrosomes are organelles involved in the organization of the mitotic spindle and they are targets of autoantibodies in systemic sclerosis (SSc). We used recombinant centrosome autoantigens, centrosome-specific antibodies, and immunoassays to demonstrate that a significant proportion of SSc patients exhibited centrosome reactivity. Two centrosome proteins cloned in our laboratory were used to screen 129 SSc sera by Western blotting. The same sera were screened by immunofluorescence using centrosome-specific antibodies to distinguish centrosomes from nuclear speckles commonly stained by SSc sera. Using these criteria, 42.6% of SSc patients were autoreactive to centrosomes, a larger percentage than reacted with all other known SSc autoantigens. Most centrosome-positive sera reacted with both centrosome proteins and half were negative for other routinely assayed SSc autoantibodies. By these criteria, we have identified a novel class of SSc autoreactivity. Only a small percentage of normal individuals and patients with other connective tissue diseases had centrosome reactivity. These results demonstrate that centrosome autoantibodies are a major component of autoreactivity in SSc and thus have potential in disease diagnosis. Centrosome autoantigens may be useful in studying the development of autoantibodies and chronic inflammation in SSc and perhaps other autoimmune diseases.

Immunologic abnormalities in scleroderma

The immune system abnormalities of scleroderma are diverse and in association with vascular and mesenchymal cell abnormalities, contribute to the organ system dysfunction and clinical expression of the disease. Recent insights into novel immune regulatory pathways, immune reactivity to self-antigens, and the potential association of persistent fetal cells and disease expression may serve to increase our understanding of this enigmatic disease.

Analysis of IgG subclasses of human antitopoisomerase I autoantibodies suggests chronic B cell stimulation

Antitopoisomerase I autoantibodies are highly specific of scleroderma and are mainly IgG. The present study was designed to evaluate the prevalence of each IgG antitopoisomerase I subclass. An ELISA for the detection of IgG antitopoisomerase I subclasses was standardized and used to study the antibodies from 49 antitopoisomerase I-positive patients identified from a total of 541 patients. Correlations and multivariate analysis were performed to determine the frequency of associations between the IgG antitopoisomerase I subclasses. All IgG antitopoisomerase I subclasses were found. Twelve patients (24.5%) had all four IgG antitopoisomerase I subclasses, 13 (26.5%) had three, 16 (32.7%) had two, and 7 (14.3%) had only one antitopoisomerase I subclass. The presence of all four IgG antitopoisomerase I subclasses suggests that this specific B-cell is the target of multiple activation pathways which indicate that there is a complex T-cell-cytokine-driven process. Together with the absence of other autoantibodies in these sera, our results support the concept of a multiple but highly selected and chronic B-cell activation in scleroderma patients with antitopoisomerase I.

Diffuse lung disease: product of genetic susceptibility and environmental encounters

Diffuse (interstitial) lung disease comprises a wide variety of conditions, individually relatively uncommon but collectively being found in approximately 50 per 100,000 population. Some of these diseases are of known aetiology but others are not. It has been suggested that the environment is a major contributory factor in this group of diseases. However, since not all individuals exposed to a common environment develop interstitial diseases, it can be hypothesised that there is a genetic predisposition to their development. These diseases cause major morbidity and mortality due to lung injury and fibrosis. It follows that, if individuals who are genetically predisposed to develop diseases characterised by lung injury and fibrosis can be identified, then management strategies can be designed which will attempt to identify and treat early disease and, in the longer term, to develop targeted genetic interventional approaches to treatment.

Systemic sclerosis. A vascular perspective

The horizon is bright for SSc in a vascular context. Surrogate markers can now be routinely used in the management of the active patient; new cytokines, such as VEGF, can be studied along with the known abnormalities of the cytokine cascade (TGF beta 1, PDGF) for a more integrated understanding of the vascular pathogenesis of SSc (Fig. 6); and combination therapies can be applied before vascular insufficiency leads to vital organ failure. Thus, despite reimbursement and research funding constraints, the future for both the SSc patient and the investigator of SSc is optimistic when based on a firm biologic foundation.

Sensitivity and specificity of anti-Jo-1 antibodies in autoimmune diseases with myositis

OBJECTIVE

To determine the sensitivity and specificity of anti-Jo-1 in systemic sclerosis (SSc) patients with and without myositis.

METHODS

Immunoblots on HeLa nuclei were used to screen sera from 554 consecutive connective tissue disease patients. Those who had 45-55-kd bands, all patients with polymyositis/dermatomyositis (PM/DM), and a random selection of SSc, Raynaud's disease, systemic lupus erythematosus, and rheumatoid arthritis patients were also studied by anti-Jo-1 enzyme-linked immunosorbent assay and by immunoblots on rabbit pooled aminoacyl-transfer RNA synthetase.

RESULTS

Anti-Jo-1 was present only in 8 of the 40 PM/DM patients.

CONCLUSION

Anti-Jo-1 is specific for PM/DM.