Autoantibodies In Rheumatoid Arthritis Research Articles

A predominant involvement of the triple seropositive patients and others with rheumatoid factor in the association of smoking with rheumatoid arthritis

The major environmental risk factor for rheumatoid arthritis (RA) is smoking, which according to a widely accepted model induces protein citrullination in the lungs, triggering the production of anti-citrullinated protein antibodies (ACPA) and RA development. Nevertheless, some research findings do not fit this model. Therefore, we obtained six independent cohorts with 2253 RA patients for a detailed analysis of the association between smoking and RA autoantibodies. Our results showed a predominant association of smoking with the concurrent presence of the three antibodies: rheumatoid factor (RF), ACPA and anti-carbamylated protein antibodies (ACarPA) (3 Ab vs. 0 Ab: OR = 1.99, p = 2.5 × 10–8). Meta-analysis with previous data (4491 patients) confirmed the predominant association with the concurrent presence of the three antibodies (3 Ab vs. 0 Ab: OR = 2.00, p = 4.4 ×10–16) and revealed that smoking was exclusively associated with the presence of RF in patients with one or two antibodies (RF+1+2vs. RF−0+1+2: OR = 1.32, p = 0.0002). In contrast, no specific association with ACPA or ACarPA was found. Therefore, these results showed the need to understand how smoking favors the concordance of RA specific antibodies and RF triggering, perhaps involving smoking-induced epitope spreading and other hypothesized mechanisms.

The Impact of Cigarette Smoking on Risk of Rheumatoid Arthritis: A Narrative Review.

Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic inflammation and subsequent proliferation of synovial tissues, which eventually leads to cartilage and bone destruction without effective treatments. Anti-citrullinated cyclic peptide/protein antibody (ACPA) and rheumatoid factor (RF) are two main characteristic autoantibodies found in RA patients and are associated with unfavorable disease outcomes. Although etiologies and causes of the disease have not been fully clarified yet, it is likely that interactive contributions of genetic and environmental factors play a main role in RA pathology. Previous works have demonstrated several genetic and environmental factors as risks of RA development and/or autoantibody productions. Among these, cigarette smoking and HLA-DRB1 are the well-established environmental and genetic risks, respectively. In this narrative review, we provide a recent update on genetic contributions to RA and the environmental risks of RA with a special focus on cigarette smoking and its impacts on RA pathology. We also describe gene–environmental interaction in RA pathogenesis with an emphasis on cigarette smoking and HLA-DRB1.

Past infections are associated with low levels of anti-citrullinated protein autoantibodies in rheumatoid arthritis.

Background : Rheumatoid arthritis (RA), an autoimmune disease of unknown etiology, is believed to occur as the result of actions of genetic and environmental factors. In this study, we examined the relation of past histories about infectious diseases with the levels anti-citrullinated protein autoantibodies (ACPA) in RA. Methods : Results of a questionnaire about histories of infectious diseases were obtained from 85 patients with RA, and were analyzed. Results : Significantly lower level of ACPA was detected in patients with the history of tonsillitis, otitis media or urinary cystitis than in those without it. There was no difference in the level of ACPA in RA patients between with and without cold / influenza, rubella, chickenpox, herpes labialis or herpes zoster. When RA patients were divided into two groups, high-level and low-level ACPA, multiple logistic regression analysis revealed that the history of otitis media was a significantly independent factor for the low level of ACPA. There was no significant relation between the level of rheumatoid factor and histories of infectious diseases. Conclusion : This study clarified that the past history of otitis media is associated with the low level of ACPA in RA. J. Med. Invest. 67 : 182-188, February, 2020.

Disordered Antigens and Epitope Overlap Between Anti–Citrullinated Protein Antibodies and Rheumatoid Factor in Rheumatoid Arthritis

Anti-citrullinated protein antibodies (ACPAs) and rheumatoid factor (RF) are commonly present in rheumatoid arthritis (RA) without a clear rationale for their coexistence. Moreover, autoantibodies develop against proteins with different posttranslational modifications and native proteins without obvious unifying characteristics of the antigens. We undertook this study to broadly evaluate autoantibody binding in seronegative and seropositive RA to identify novel features of reactivity. An array was created using a total of 172,828 native peptides, citrulline-containing peptides, and homocitrulline-containing peptides derived primarily from proteins citrullinated in the rheumatoid joint. IgG and IgM binding to peptides were compared between cyclic citrullinated peptide (CCP)-positive RF+, CCP+RF-, CCP-RF+, and CCP-RF- serum from RA patients (n = 48) and controls (n = 12). IgG-bound and endogenously citrullinated peptides were analyzed for amino acid patterns and predictors of intrinsic disorder, i.e., unstable 3-dimensional structure. Binding to IgG-derived peptides was specifically evaluated. Enzyme-linked immunosorbent assay confirmed key results. Broadly, CCP+RF+ patients had high citrulline-specific IgG binding to array peptides and CCP+RF- and CCP-RF+ patients had modest citrulline-specific IgG binding (median Z scores 3.02, 1.42, and 0.75, respectively; P < 0.0001). All RA groups had low homocitrulline-specific binding. CCP+RF+ patients had moderate IgG binding to native peptides (median Z score 2.38; P < 0.0001). The highest IgG binding was to citrulline-containing peptides, irrespective of protein identity, especially if citrulline was adjacent to glycine or serine, motifs also seen in endogenous citrullination in the rheumatoid joint. Highly bound peptides had multiple features predictive of disorder. IgG from CCP+RF+ patients targeted citrulline-containing IgG-derived peptides. Disordered antigens, which are frequently citrullinated, and common epitopes for ACPAs and RF are potentially unifying features for RA autoantibodies.

Exposure to ambient air pollution and autoantibody status in rheumatoid arthritis.

To evaluate the relationship between air pollutant (AP) exposure and rheumatoid arthritis (RA) autoantibody status METHODS: We performed a cross sectional study utilizing enrollment data from participants in the Veterans Affairs rheumatoid arthritis registry. HLA-DRB1 shared epitope (SE), smoking, rheumatoid factor (RF), and anti-cyclic citrullinated peptide antibody (ACPA) status were collected. Mean exposure levels were obtained for AP (NO2, SO2, particulate matter [PM2.5, PM10], and ozone) from air quality monitoring stations at patients' residential zip codes in the year prior to enrollment. Multivariable logistic and ordinary least squares regression models were used to determine independent associations of AP with RA seropositivity and autoantibody concentration. The cohort included 557 veterans (90% male, 76% Caucasian), with mean age of 70 years and mean disease duration of 13 years. The majority were HLA-DRB1 SE, RF, and ACPA positive (73%, 79%, and 76%, respectively). In univariate models, PM2.5 exposure was associated with higher ACPA concentration (p = 0.009). Similarly, in multivariable regression models, PM2.5 exposure was independently associated with higher ACPA concentration (p = 0.037). Current smoking independently predicted RF and ACPA positivity and titers, while HLA-DRB1 SE alleles were associated with RF positivity and ACPA positivity and titers. In an elderly cohort of RA patients, fine particulate matter (PM2.5) exposure independently predicted higher ACPA concentration. Further study of fine particulate matter in the pathogenesis of RA is warranted. Key Points • A study that integrates both genetic and environmental exposure data, relative to RA autoantibody status. • Of different air pollutants measures, exposure to fine particulate matter (PM2.5) appears to be most closely linked to ACPA titers.

Circulating levels of free 25(OH)D increase at the onset of rheumatoid arthritis.

ObjectiveEpidemiological studies suggest vitamin D deficiency as a potential risk factor for rheumatoid arthritis (RA) development, a chronic autoimmune disorder highly prevalent in indigenous North American (INA) population. We therefore profiled the circulating levels of 25-hydroxyvitaminD [25(OH)D], an active metabolite of vitamin D, in a cohort of at-risk first-degree relatives (FDR) of INA RA patients, a subset of whom subsequently developed RA (progressors).Methods2007 onward, serum samples from INA RA patients and FDR were collected at the time of a structured baseline visit and stored at -20°C. Anti-citrullinated protein antibodies (ACPA), 25(OH)D, hs-CRP, vitamin-D binding protein (VDBP) and parathyroid hormone (PTH) levels were determined using ELISA and rheumatoid factor (RF) seropositivity was determined by nephelometry.ResultsWe demonstrate that 25 (OH) D concentrations were lower in winter than summer (P = 0.0538), and that serum 25(OH)D levels were higher in samples collected and stored after 2013 (P<0.0001). Analysis of samples obtained after 2013 demonstrated that 37.6% of study participants were 25(OH)D insufficient (<75nmol/L). Also, seropositive RA patients and FDR had lower 25(OH)D levels compared to ACPA-/FDR (P<0.05, P<0.01 respectively). Linear regression analysis showed 25(OH)D insufficiency was inversely associated with presence of RA autoantibodies. Longitudinal samples from 14 progressors demonstrated a consistent increase in 25(OH)D levels at the time they exhibited clinically detectable joint inflammation, without any significant change in VDBP or PTH levels. Spearman rank correlation analysis showed significant association between 25(OH)D and PTH levels, both in RA patients and progressors at RA onset time.ConclusionWe demonstrate that 25(OH)D levels in serum increased at RA onset in progressors. The potential role that vitamin D metabolites and their downstream effects play in RA transition requires further investigation.

Citrullination facilitates cross-reactivity of rheumatoid factor with non-IgG1 Fc epitopes in rheumatoid arthritis

Rheumatoid factor (RF) and anti-citrullinated protein antibodies (ACPAs) are the two most prevalent autoantibodies in rheumatoid arthritis (RA), and are thought to have distinct autoantigen targets. Whilst RF targets the Fc region of antibodies, ACPAs target a far broader spectrum of citrullinated peptides. Here we demonstrate significant sequence and structural homology between proposed RF target epitopes in IgG1 Fc and the ACPA target fibrinogen. Two of the three homologous sequences were susceptible to citrullination, and this modification, which occurs extensively in RA, permitted significant cross-reactivity of RF+ patient sera with fibrinogen in both western blots and ELISAs. Crucially, this reactivity was specific to RF as it was absent in RF− patient and healthy control sera, and could be inhibited by pre-incubation with IgG1 Fc. These studies establish fibrinogen as a common target for both RF and ACPAs, and suggest a new mechanism in RF-mediated autoimmune diseases wherein RF may act as a precursor from which the ACPA response evolves.

Cytokines (IL-15, IL-21, and IFN-γ) in rheumatoid arthritis: association with positivity to autoantibodies (RF, anti-CCP, anti-MCV, and anti-PADI4) and clinical activity

Rheumatoid arthritis (RA) is an autoimmune disease characterized by synovial membrane damage and autoantibody production. RA is a heterogeneous disease, where cytokines such as IL-15, IL-21, and IFN-γ have been associated. However, their association with the autoantibodies has not been clearly described. The aim of this study was to evaluate the relationship between the cytokines IL-15, IL-21, and IFN-γ with the autoantibodies (RF, anti-CCP, anti-MCV, and anti-PADI4) in RA and disease activity. This study included 153 RA patients and 80 control subjects (CS). The levels of IL-15, IL-21, IFN-γ, anti-CCP, anti-MCV, and anti-PADI4 were quantified by ELISA, whereas RF was quantified by turbidimetry. The disease activity was evaluated by the indices disease activity score 28-erythrocyte sedimentation rate (DAS28-ESR), clinical disease activity index (CDAI), and simple disease activity index (SDAI). The serum levels of IL-15, IL-21, and IFN-γ, and autoantibodies were increased in RA patients, compared with CS (p < 0.05). A correlation was found between IL-21 and anti-CCP and anti-MCV (p < 0.05). According to RA evolution, RF, anti-CCP, and anti-MCV had higher levels in early RA. In addition, increased levels of IL-21 were observed in RA seropositive patients (RF/anti-CCP/anti-MCV). The higher levels of both cytokines and autoantibodies were observed in moderate activity, evaluated by the three indices. Our results suggest that the increased soluble levels of IL-15, IL-21, and IFN-γ are involved in the inflammatory network in RA. However, IL-21 serum levels are associated with higher titers of autoantibodies (RF, anti-CCP, and anti-MCV) and IL-15 with moderate activity. Key Points • IL-15, IL-21, and IFN-y are associated with the immunopathology of RA, but not significantly with the evolution of the disease. • RF, anti-CCP, and anti-MCV had higher levels in early than established RA. • IL-21 has an association with RF, anti-CCP, and anti-MCVand, for this reason, could be proposed as a disease biomarker. • Patients with activity moderate of disease showed higher levels of RF, anti-CCP, anti-MCV, and IL-15.

Osteoporosis Pathophysiology, Epidemiology, and Screening in Rheumatoid Arthritis

To review the burden of osteoporosis (OP) in rheumatoid arthritis (RA) and to describe the OP screening strategies applied in RA. RA is an inflammatory condition that predisposes patients to development of OP. OP in RA has a multifactorial pathogenesis with systemic inflammation and glucocorticoid use playing major roles. Newer studies have reported an intriguing association between RA autoantibodies and the development of OP. OP screening strategies in RA patients include clinical and vitamin D assessment, biochemical markers of bone remodeling, and bone imaging evaluations, particularly dual-energy X-ray absorptiometry (DXA). Fragility fractures are an important comorbidity of RA. OP screening strategies are both feasible and effective in RA patients and recommended by most specialty organizations. Given the considerable exposure to factors related to OP development, such as pro-inflammatory cytokines and glucocorticoid treatment, special attention should be directed to biochemical and DXA results in RA patients.

Novel autoantibodies in rheumatoid arthritis.

Rheumatoid factor and antibodies against cyclic citrullinated peptides represent a diagnostic hallmark in rheumatoid arthritis (RA). However, over the last decades many other autoantibodies have been identified. Several proteins can trigger an aberrant autoimmune response in their native form while others acquire this feature after post-translational modifications such as citrullination, carbamylation or acetylation. It is of interest that also the enzymes catalyzing such post-translational modifications (e.g. the protein arginine deiminases) can transform themselves into autoantibodies in RA. The purpose of this review article is to provide an overview of relevant literature published over the last years regarding novel autoantibodies and their possible diagnostic and prognostic significance in RA.

Neutrophil extracellular traps exert both pro- and anti-inflammatory actions in rheumatoid arthritis that are modulated by C1q and LL-37

ObjectiveNeutrophil extracellular traps (NET), produced by activated polymorphonuclear neutrophils (PMN), are supposed to play a role in the pathogenesis of rheumatoid arthritis (RA), a chronic inflammatory autoimmune disease characterized by anti-citrullinated protein antibodies (ACPA). Indeed, NET contain citrullinated autoantigens and some RA autoantibodies recognize NET. However, the mechanisms by which NET trigger or perpetuate the inflammatory process in RA are hitherto not elucidated. We hypothesized that, in addition to citrullination, NET might also contain stimulatory proteins and directly activate inflammatory target cells, as PMN and macrophages. MethodsNET antigenic and inflammatory properties were analyzed in 157 healthy donors (HD) and RA patients, the largest analysis reported so far. Primary PMN and monocyte-derived macrophages were isolated and immunoglobulin G (IgG) purified. NET were induced (NETosis), isolated and quantified. NET antigenicity was analyzed by fluorescence microscopy. PMN and macrophages were stimulated with NET with/without ACPA, C1q, LL-37 or lipopolysaccharide (LPS) and cell activation was estimated by flow cytometry and ELISA. ResultsPMN from RA patients produced more NET than HD PMN. We next dissected how NET mechanistically affect inflammatory cells. Particularly, we show for the first time that RA and HD NET activated both resting macrophages and PMN, but importantly RA NET were more stimulatory, leading to secretion of inflammatory cytokines and up-regulation of HLA/CD86/CD11b. IgG from ACPA-positive RA patients specifically recognized RA and even HD NET. Nevertheless, NET-induced cell activation occurs independently of immune complex formation with ACPA. Likewise, endosomal acidification was not required. Notably, we also report that complement C1q increased the NET stimulatory activity on macrophages only, due to higher expression of C1q receptors, which was further supported by the LL-37 antimicrobial peptide. In contrast, NET specifically inhibited interleukin (IL)-6 secretion by LPS-activated macrophages and not PMN, especially with C1q/LL-37. This inhibition was not mediated by NET-derived proteases or LPS neutralization and was associated with the simultaneous induction of IL-10 secretion. ConclusionWe show that NET possess both pro- and anti-inflammatory properties depending on target cells, their activation levels and C1q/LL-37. Thus, independently of ACPA, NET modulate RA chronic inflammation via this new dual activity we identified. In addition, NET may trigger autoimmunity in RA as ACPA recognize NET antigens but not non-activated PMN. Therefore, we conclude that excess of NETosis together with enhanced NET activity participate to RA pathogenesis at different levels.

Differential ACPA Binding to Nuclear Antigens Reveals a PAD-Independent Pathway and a Distinct Subset of Acetylation Cross-Reactive Autoantibodies in Rheumatoid Arthritis.

Rheumatoid arthritis (RA) associated anti-citrullinated protein autoantibodies (ACPA) target a wide range of modified proteins. Citrullination occurs during physiological processes such as apoptosis, yet little is known about the interaction of ACPA with nuclear antigens or apoptotic cells. Since uncleared apoptotic cells and neutrophil extracellular trap (NET) products have been postulated to be central sources of autoantigen and immunostimulation in autoimmune disease, we sought to characterize the anti-nuclear and anti-neutrophil reactivities of ACPA. Serology showed that a subset of anti-CCP2 seropositive RA patients had high reactivity to full-length citrullinated histones. In contrast, seronegative RA patients displayed elevated IgG reactivity to native histone compared to controls, but no citrulline-specific reactivity. Screening of 10 single B-cell derived monoclonal ACPA from RA patients revealed that four ACPA exhibited strong binding to apoptotic cells and three of these had anti-nuclear (ANA) autoantibody reactivity. Modified histones were confirmed to be the primary targets of this anti-nuclear ACPA subset following immunoprecipitation from apoptotic cell lysates. Monoclonal ACPA were also screened for reactivities against stimulated murine and human neutrophils, and all the nuclear-reactive monoclonal ACPA bound to NETs. Intriguingly, one ACPA mAb displayed a contrasting cytoplasmic perinuclear neutrophil binding and may represent a different NET-reactive ACPA subset. Notably, studies of CRISPR-Cas9 PAD4 KO cells and cells from PAD KO mice showed that the cytoplasmic NET-binding was fully dependent on PAD4, whilst nuclear- and histone-mediated NET reactivity was largely PAD-independent. Our further analysis revealed that the nuclear binding could be explained by consensus-motif driven ACPA cross-reactivity to acetylated histones. Specific acetylated histone peptides targeted by the monoclonal antibodies were identified and the anti-modified protein autoantibody (AMPA) profile of the ACPA was found to correlate with the functional activity of the antibodies. In conclusion, when investigating monoclonal ACPA, we could group ACPA into distinct subsets based on their nuclear binding-patterns and acetylation-mediated binding to apoptotic cells, neutrophils, and NETs. Differential anti-modified protein reactivities of RA-autoantibody subsets could have an important functional impact and provide insights in RA pathogenesis.

UBASH3A gene polymorphisms and expression profile in rheumatoid arthritis

Objectives: Recent evidence has demonstrated that UBASH3A play a pivotal role in multiple autoimmune diseases. In this study, we explored the association between UBASH3A gene single-nucleotide polymorphisms (SNPs) and rheumatoid arthritis (RA) in a Chinese Han population. We also comparatively evaluated the UBASH3A expression profile in peripheral blood mononuclear cells (PBMCs) from patients with RA and healthy controls.Methods: Four UBASH3A polymorphisms (rs1893592, rs11203203, rs2277798, and rs3788013) were studied in 553 patients with RA and 587 controls in a Chinese population. Genotyping was performed using the Fluidigm 192.24 Dynamic Array Integrated Fluidic Circuit (IFC). For gene expression study, UBASH3A mRNA levels of 30 RA patients and 31 healthy individuals were assessed by real-time quantitative polymerase chain reaction (RT-qPCR). Data were analyzed by SPSS 19.0 software.Results: A significant association between rs1893592 polymorphism and RA was found under all genetic models (all p<.05). We also discovered a significant association between rs3788013 polymorphism and RA in the allele and genotype distributions, as well as the recessive model (all p<.05). Moreover, we found the genotype distribution and allele frequency of rs1893592 were significantly associated with RF phenotype in the RA patients (χ2 = 6.786, p=.034; χ2 = 4.534, p=.033; respectively). We also found the genotype distribution and allele frequency of rs2277798 were significantly associated with anti-CCP phenotype in the RA patients (χ2 = 7.873, p=.020; χ2 = 4.473, p=.034; respectively). However, we did not detect any significant associations between rs11203203 and RA susceptibility and autoantibody profiles (all p>.05). The mRNA expression of UBASH3A was increased in PBMCs of patients with RA when compared to healthy controls (p=.001).Conclusions: Our observations suggested that the dysregulation of UBASH3A might be associated with the pathogenesis of RA, and UBASH3A gene polymorphisms (rs1893592 and rs3788013) might contribute to RA susceptibility in Chinese Han population.

The Clinical Value of Autoantibodies in Rheumatoid Arthritis.

Rheumatoid arthritis (RA) is a highly heterogeneous syndrome in terms of clinical presentation, progression, and response to therapy. In such a complicated context, the identification of disease-related biomarkers would be undoubtedly helpful in assisting tailored approaches for every patient. Despite remarkable efforts, however, progress in new biomarker development and validation is dramatically slow. At present, none of the candidate genetic, cellular, or molecular biomarker has yet surpassed the clinical value of RA-specific autoantibodies, including rheumatoid factor (RF) and anti-citrullinated protein autoantibodies (ACPA). Rather, recent years have witnessed significant advancements in our understanding of the multiple roles that RF and ACPA play in RA pathophysiology. This has helped clarifying the mechanistic basis of the clinical associations of autoantibodies in RA. In this short review, we will briefly summarize the effector functions of RF and ACPA, and analyse how autoantibodies may help subclassifying RA patients in terms of clinical presentation and response to therapy.

Autoantibodies to heat shock proteins 60, 70, and 90 in patients with rheumatoid arthritis

Heat shock proteins (HSP) have been reported to impact immune responses and to be associated with rheumatoid arthritis (RA). Recently, we provided evidence for a role of autoantibodies to Hsp40 in patients with RA. In this study, we aimed at investigating the humoral autoimmune response to Hsp60, Hsp70, and Hsp90 in RA patients (n = 39). In comparison with healthy controls (n = 40), circulating IgG, IgM, and IgA autoantibodies against Hsp60, Hsp70, and Hsp90 were significantly increased in RA patients. Non-parametric statistical analysis, however, revealed no significant association between anti-HSP and disease activity or disease progression. On the other hand, positive correlations between serum levels of anti-Hsp60 IgG and IL-4 (Th2-like cytokine) or between serum levels of anti-Hsp90 IgG and IFN-ɣ (Th1-like cytokine) were found to be statistically significant in RA. In addition, a significant inverse correlation was found for serum levels of anti-Hsp70 IgM and TNF-α (Th1-like cytokine) in RA. Our results suggest a pronounced anti-Hsp60, anti-Hsp70, and anti-Hsp90 humoral autoimmune response in RA patients that seems not to be directly linked to RA pathophysiology, however, may have a potential modulatory impact on inflammatory status in this disease. Further investigations are needed to clarify the role of anti-HSP autoantibodies in RA.

Association of high titers of anti-carbamylated protein antibodies with decreased bone mineral density in early arthritis patients.

Rheumatoid arthritis (RA) has a negative impact on bone that is partly mediated by anti-citrullinated proteins antibodies (ACPA). These antibodies are associated with erosions, and with juxta-articular and systemic bone loss. Other RA autoantibodies, the anti-carbamylated protein antibodies (anti-CarPA), are independently associated with erosions. However, we do not know if they are also associated with juxta-articular and systemic bone loss. Here, we have addressed this question with data from 548 early arthritis (EA) patients. Bone mineral density (BMD) was assessed by dual-energy x-ray absorptiometry at the lumbar spine (LS), total hip (TH) and metacarpophalangeal joints (MCP). The 25.9% anti-CarPA positive patients did not show significant differences in BMD Z-scores with the negative patients. Nevertheless, this result was due to the similarity between negative and low-positive (below the median of the positive) patients, whereas the high-positive patients showed significant decrease of BMD at LS (β = -0.39, p = 0.01) and TH (β = -0.30, p = 0.02); but not at the juxta-articular bone of MCP. Given the overlap between anti-CarPA and ACPA, we included the two autoantibodies in an analysis that showed significantly lower BMD Z-scores at LS and TH (p< 0.01) only in the ACPA positive/anti-CarPA high-positive subgroup. However, the similar coefficients of regression between the ACPA positive/anti-CarPA high-positive and the ACPA negative/anti-CarPA high-positive subgroups (β = -0.50 vs. -0.52 at LS, and β = -0.37 vs. -0.30 at TH) suggested an independent association. Overall, these results support a contribution of anti-CarPA to systemic bone loss in EA patients.

An update on research advances in rheumatoid arthritis: from clinic to basic science

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease characterised by breach of self-tolerance and production of autoantibodies, particularly rheumatoid factor (RF) and anti-citrullinated protein antibodies (ACPA). Many events can lead to loss of tolerance in RA and they include genetic, environmental and epigenetic factors as well as post-translational modifications. Current therapies in RA tend to treat symptoms or slow down the disease progression but no cure exists at the moment. This review provides a summary of the main recent research advances regarding new therapies in RA and new studies about the effect of genetic, environment and epigenetics in this autoimmune disease. Moreover, it summarises the present knowledge about the role of “new” autoantibodies in RA focussing on anti-carbamylated protein antibodies (anti-CarP), anti-hinge antibodies, anti-acetylated protein antibodies and anti-malondialdehyde-acetaldehyde adducts (MAA) antibody. Finally, a brief summary on the recent role of Fab N-glycosylation is reported.

Detection of 16α-Hydroxyestrone-histone 1 Adduct as High-Affinity Antigen for Rheumatoid Arthritis Autoantibodies.

Increased concentrations of 16α-hydroxyestrone (16α-OHE1) have been observed in rheumatoid arthritis (RA), but the underlying mechanism of this remains elusive. Here we aimed to identify the role played by 16α-OHE1 in RA. In 40 RA patients, the specificities of antibodies from the sera of these patients were checked by direct binding, inhibition ELISA, and quantitative precipitation titration. Competition ELISA was also used for the estimation of 16α-OHE1 in the serum of different RA patients. RA IgG from a patient's sera showed strong recognition to 16α-OHE1-H1 (histone 1) adduct in comparison to control subjects (p < 0.001), as the formation of this adduct brings out various biochemical changes that might generate neo-epitopes, which have been well-recognized by these antibodies. The affinity of RA antibodies for 16α-OHE1-H1 (1.10 × 10- 7 M) was high, as detected by the Langmuir plot. Comparing RA patients to the controls, no significant differences were detected in the level of 16α-OHE1 or 2-hydroxyestrone/16α-OHE1 ratio. 16α-OHE1-H1 might have an antigenic role and function as a high-affinity antigen for RA autoantibodies and, therefore, could be used as a biomarker for this disease.

Smoking is not linked to the development of anti-peptidylarginine deiminase 4 autoantibodies in rheumatoid arthritis

BackgroundDefining environmental factors responsible for development of autoimmunity in rheumatoid arthritis (RA) is critical for understanding mechanisms of disease initiation and propagation. Notably, a history of cigarette smoking has been implicated in the genesis of RA and is associated with worse disease outcomes. Antibodies to peptidylarginine deiminase 4 (PAD4) are also associated with more severe RA. A subset of patients who have PAD4 autoantibodies that cross-react with PAD3 (anti-PAD3/4) are at the highest risk for interstitial lung disease, and this risk is augmented by a history of cigarette smoking. It is unclear, however, if smoking is etiologically linked to the development of anti-PAD4 antibodies.MethodsPatients were included in this study if they had physician-diagnosed RA as well as DNA, serum, and a date-matched clinical assessment (n = 274). Anti-PAD4 and anti-CCP antibodies were measured by immunoprecipitation and ELISA, respectively; shared epitope (SE) status was determined by HLA-DRβ1 genotyping. Logistic regression analysis was used to evaluate associations of smoking with PAD4 antibodies, with adjustment for relevant demographic and clinical features. Stratified analyses by disease duration and shared epitope status were also performed.ResultsAnti-PAD4 antibodies were present in 25% of RA patients, with 50% of these individuals having anti-PAD3/4 cross-reactive antibodies. Anti-PAD4 antibodies were significantly associated with a longer disease duration, SE alleles, and anti-CCP antibodies. Importantly, there were no significant differences in smoking history between anti-PAD4 positive and negative groups in univariate analyses, stratified analyses, or multivariable models. However, an inverse relationship between smoking and anti-PAD4 antibodies was suggested by a lower prevalence of current smokers among patients with anti-PAD3/4 antibodies compared to antibody negative individuals (p = 0.04). Further, the lowest levels of anti-PAD4 antibodies were observed in current smokers (p = 0.14), and a significant association of SE and anti-PAD4 antibodies was only present among never smokers (p = 0.01).ConclusionsSmoking history was not associated with anti-PAD4 antibodies in patients with RA. The finding that anti-PAD4 antibodies were not associated with smoking suggests that other environmental factors may contribute to the development of autoimmunity to PAD4 in these patients.

Association between Rheumatoid Arthritis and Pulmonary Hypertension: Data from the French Pulmonary Hypertension Registry

Background: Precapillary pulmonary hypertension (PH), and particularly pulmonary arterial hypertension (PAH), is a life-threatening complication of connective tissue diseases (systemic sclerosis, systemic lupus erythematosus, and mixed connective tissue disease). The relationship between PH and rheumatoid arthritis (RA) has not been clearly established. Objectives: The aim of the study was to evaluate the relationship between precapillary PH and RA. Methods: We identified patients with PH and suspected RA included in the French PH Registry between 1 May 2004 and 31 December 2012 and evaluated the prevalence of confirmed RA in this population. RA phenotypes, clinical, functional, and hemodynamic data, and patient outcomes were recorded. Results: RA was confirmed in 20 patients (70% female; mean age 52 years) with precapillary PH, including 10 patients with PAH, 6 with severe PH due to lung disease, and 4 with chronic thromboembolic PH. The prevalence of RA was 0.35% (95% CI: 0.23–0.54) in the French PH Registry and 0.58% (95% CI: 0.30–1.11) in idiopathic PAH, comparable to that in the general population. The RA phenotype was characterized by the presence of specific RA autoantibodies and joint erosions in 75% of the patients. The outcomes of PH in the RA patients were unremarkable compared to those in other patients from the registry, and RA therapies had no major impact on the cardiopulmonary parameters. Conclusion: When precapillary PH occurs in RA patients, all PH subsets may be identified. The RA prevalence in the French PH Registry is similar to that in the general population, which does not support a specific association or an indication for PH screening in RA patients.