Rheumatoid factors: what's new?

Increased Rheumatoid Factor production in patients with severe COVID-19

BACKGROUND

Searching for Rheumatoid Factors (RF) in patients with coronavirus disease (COVID-19) has rarely been described.

OBJECTIVES

To investigate the association between RF isotypes (IgM, IgA, and IgG) and different clinical presentations of COVID-19 in a series of Tunisian patients.

STUDY DESIGN

Eighty-two COVID-19 patients were enrolled in this study. Symptomatic cases were recruited from the Department of COVID-19 and the intensive care unit (ICU) of the University Hospital of Mahdia, Tunisia, from January 2021 to March 2021. Different RF isotypes were assessed using a commercial enzyme-linked immunosorbent assay (ELISA).

RESULTS

Forty-one patients (50%) had RF of any isotype. Thirty-two patients (39%) were tested positive for RF-IgM. Symptomatic forms of the disease were associated with RF-IgM positivity (p = 0.005). The mean concentration of RF-IgM was higher in the severe form than in the moderate and asymptomatic forms (p = 0.006).

CONCLUSIONS

Our study suggests that the production of RF-IgM isotype is increased in patients with severe COVID-19.

Recent Advances in Biosensors for Diagnosis of Autoimmune Diseases

Over the last decade, autoimmune diseases (ADs) have undergone a significant increase because of genetic and/or environmental factors; therefore, their simple and fast diagnosis is of high importance. The conventional diagnostic techniques for ADs require tedious sample preparation, sophisticated instruments, a dedicated laboratory, and qualified personnel. For these reasons, biosensors could represent a useful alternative to these methods. Biosensors are considered to be promising tools that can be used in clinical analysis for an early diagnosis due to their high sensitivity, simplicity, low cost, possible miniaturization (POCT), and potential ability for real-time analysis. In this review, recently developed biosensors for the detection of autoimmune disease biomarkers are discussed. In the first part, we focus on the main AD biomarkers and the current methods of their detection. Then, we discuss the principles and different types of biosensors. Finally, we overview the characteristics of biosensors based on different bioreceptors reported in the literature.

Rheumatoid factor recognizes specific domains of the IgG heavy chain complexed with HLA class II molecules

OBJECTIVE

We previously reported that RF recognized the IgG heavy chain (IgGH)/RA-susceptible HLA class II molecule complex. In the present study, we investigated the molecular mechanisms underlying HLA binding to and the RF recognition of IgGH.

METHODS

We synthesized various types of IgGH segments, including VH, CH1, CH2 and CH3, and transfected them with or without HLA class II molecules into the Human Embryonic Kidney 293T cell line. IgGH single domains linked with the HLA-Cw3 peptide, which binds to the binding groove of the HLA class II molecule, were also synthesized. The expression of IgGH domains on the cell surface and their recognition by RF were examined using flow cytometry.

RESULTS

Flag-tagged IgGH segments containing CH1 (CH1, VH-CH1, CH1-CH2, VH-CH1-CH2, CH1-CH2-CH3 and VH-CH1-CH2-CH3) were clearly presented on the cell surface by HLA-DR4, while segments without the CH1 domain were expressed at a low level, and the CH3 single domain was only weakly detected on the cell surface, even with HLA-DR4. We then transfected IgGH single domains linked to the Cw3 peptide together with HLA-DR4 and showed that RF-containing sera from RA patients only recognized the CH3 domain and none of the other single domains. When various segments without the Cw3 peptide were transfected with HLA-DR4, only the CH1-CH2-CH3 segment and full-length IgGH were detected by the sera of RA patients.

CONCLUSION

The CH1 domain of IgGH binds to the RA-susceptible HLA-DR molecule and is expressed on the cell surface. RF specifically recognizes the CH3 domain of the IgGH/HLA-DR4 complex.

Screening epitope peptides based on a phage-displayed random peptide and peptide microarrays to contribute to improving the diagnostic efficiency of systemic lupus erythematosus

BACKGROUND

Systemic lupus erythematosus (SLE) is one of the most common autoimmune diseases in China. At present, there are hundreds of autoantibodies in SLE patients; however, only a dozen of the autoantibodies can be routinely detected, and the available diagnostic antibodies are not sufficient for diagnosis or differential diagnosis of SLE patients with atypical clinical manifestations or other autoimmune diseases. Therefore, it is necessary to find new diagnostic markers to improve the diagnostic effect of SLE.

METHODS

The displayed random peptide library and peptide microarray were combined to identify SLE-related epitope peptides. A case-control design was used. The IgG antibodies in the sera from SLE patients, healthy controls, and other autoimmune disease controls underwent a reaction with the phage-display random peptide library, respectively. Selected epitope peptides were used to construct a peptide chip. A total of 644 serum samples (including 296 SLE patients, 168 disease controls, and 180 healthy controls) were used for further screening and verification. Peptides with an area under the curve (AUC) > 0.650 were further verified by ELISA. Finally, 500 serum samples (including 200 SLE patients, 150 disease controls, and 150 healthy controls) were used to verify and evaluate the diagnostic and differential diagnostic efficacy of the selected peptides.

RESULTS

After the previous screening, five epitope peptides (SLE_P19, SLE_P20, SLE_P27, SLE_P28, and SLE_P29) may have potential as SLE diagnostic markers. Additionally, SLE_P27 was superior to the other four peptides in the diagnosis and differential diagnosis of SLE and rheumatoid arthritis (RA). The AUC of SLE_P27 was 0.938, the sensitivity was 76.00%, the specificity was 92.70%, the positive likelihood ratio was 10.411, the negative likelihood ratio was 0.259, and the accuracy was 84.40%. The diagnostic efficacy of SLE can be increased by combining the five selected peptides with the anti-double stranded DNA antibody (anti-dsDNA)and anti-Smith antibodies (anti-Sm).

CONCLUSIONS

In this study, we identified five peptides that may serve as potential biomarkers for SLE diagnosis using the strategy of combining the displayed random peptide library with the peptide microarray. The combination of selected peptides and existing autoantibodies can significantly improve the diagnostic efficiency. These specific peptides are expected to be new diagnostic markers for SLE.

Modification of the structural stability of human serum albumin in rheumatoid arthritis

Differential scanning calorimetry (DSC) can indicate changes in structure and/or concentration of the most abundant proteins in a biological sample via heat denaturation curves (HDCs). In blood serum for example, HDC changes result from either concentration changes or altered thermal stabilities for 7-10 proteins and has previously been shown capable of differentiating between sick and healthy human subjects. Here, we compare HDCs and proteomic profiles of 50 patients experiencing joint-inflammatory symptoms, 27 of which were clinically diagnosed with rheumatoid arthritis (RA). The HDC of all 50 subjects appeared significantly different from expected healthy curves, but comparison of additional differences between the RA and the non-RA subjects allowed more specific understanding of RA samples. We used mass spectrometry (MS) to investigate the reasons behind the additional HDC changes observed in RA patients. The HDC differences do not appear to be directly related to differences in the concentrations of abundant serum proteins. Rather, the differences can be attributed to modified thermal stability of some fraction of the human serum albumin (HSA) proteins in the sample. By quantifying differences in the frequency of artificially induced post translational modifications (PTMs), we found that HSA in RA subjects had a much lower surface accessibility, indicating potential ligand or protein binding partners in certain regions that could explain the shift in HSA melting temperature in the RA HDCs. Several low abundance proteins were found to have significant changes in concentration in RA subjects and could be involved in or related to binding of HSA. Certain amino acid sites clusters were found to be less accessible in RA subjects, suggesting changes in HSA structure that may be related to changes in protein-protein interactions. These results all support a change in behavior of HSA which may give insight into mechanisms of RA pathology.

Differential effects of periodontal microbiome on the rheumatoid factor induction during rheumatoid arthritis pathogenesis

Association between exposure to periodontal bacteria and development of autoantibodies related to rheumatoid arthritis (RA) has been widely accepted; however, direct causal relationship between periodontal bacteria and rheumatoid factor (RF) is currently not fully understood. We investigated whether periodontal bacteria could affect RF status. Patients with preclinical, new-onset, or chronic RA underwent periodontal examination, and investigation of subgingival microbiome via 16S rRNA sequencing. Degree of arthritis and RF induction was examined in collagen-induced arthritis (CIA) mice that were orally inoculated with different periodontal bacteria species. Subsequently, single-cell RNA sequencing analysis of the mouse spleen cells was performed. Patients with preclinical RA showed an increased abundance of the Porphyromonadacae family in the subgingival microbiome compared to those with new-onset or chronic RA, despite comparable periodontitis severity among them. Notably, a distinct subgingival microbial community was found between patients with high-positive RF and those with negative or low-positive RF (p=0.022). Oral infections with the periodontal pathogens P. gingivalis and Treponema denticola in CIA mice similarly enhanced arthritis score, but resulted in different levels of RF induction. Genes related to B cell receptor signaling, B cell proliferation, activation, and differentiation, and CD4⁺ T cell costimulation and cytokine production were involved in the differential induction of RF in mice exposed to different bacteria. In summary, periodontal microbiome might shape RF status by affecting the humoral immune response during RA pathogenesis.

Autoantibodies and Rheumatologic Manifestations in Hepatitis C Virus Infection

HCV is a virus that can cause chronic infection which can result in a systemic disease that may include many rheumatologic manifestations such as arthritis, myalgia, sicca syndrome, cryoglobulinemia vasculitis as well as other non-rheumatological disorders (renal failure, onco-haematological malignancies). In this population, the high frequency of rheumatoid factor (45-70%), antinuclear (10-40%) and anticardiolipin (15-20%) antibodies is a B-cell mediated finding sustained by the infection. However, the possibility that a primitive rheumatic pathology may coexist with the HCV infection is not to be excluded thus complicating a differential diagnosis between primitive and HCV-related disorders.

Rheumatoid factor positivity in antineutrophil cytoplasmic antibody-associated vasculitis: a distinct clinical entity or innocent bystander?

OBJECTIVE

To investigate the significance of rheumatoid factor (RF) positivity in antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) patients.

METHODS

AAV patients were divided into groups as follows: RF (+)/ANCA (+) (n = 94), RF (-)/ANCA (+) (n = 80), RF (+)/ANCA (-) (n = 15), and RF (-)/ANCA (-) (n = 25). Their clinical data, organ involvement patterns, laboratory data, and patient outcomes were assessed. Kaplan-Meier analysis and propensity score matching (PSM) were performed to compare outcomes and analyse differences between the groups.

RESULTS

Of the 214 patients, RF and ANCA positivity was found in 109 (50.9%) and 174 (81.3%) patients, respectively. RF (+)/ANCA (+) patients more frequently presented with general manifestations (58.5%) than the other groups. Additionally, compared with those of RF (-)/ANCA (+) group, RF (+)/ANCA (+) patients were older, had higher white blood cell, neutrophil, platelet counts, and acute phase reactants; however, creatinine and albumin levels were lower. The end-stage kidney disease-free survival rate was significantly higher in the RF (+)/ANCA (+) group (p= 0.013), while the proportion of renal involvement was comparable to the RF (-)/ANCA (+) group. PSM showed no difference in patient outcomes between the two groups after adjustment.

CONCLUSION

RF positivity was associated with a distinct phenotype in AAV patients. In particular, difference was observed in clinical features and outcomes between RF (+)/ANCA (+) and RF (-)/ANCA (+) groups, although the direct prognostic implication of RF was not evident.

Folate-methotrexate loaded bovine serum albumin nanoparticles preparation: an in vitro drug targeting cytokines overwhelming expressed immune cells from rheumatoid arthritis patients

The study planned to estimate biological parameters linked to rheumatoid arthritis (RA) patients, detecting the influence of MTX and biotherapy treatments on these parameters and synthesizing methotrexate bovine serum albumin nanoparticles linked to folate (FA-MTX-BSA NPs) to reduce the overwhelming expression of inflammatory cytokines. Inflammatory parameters showed significant increases in newly diagnosed and MTX-receiving groups while no changes were observed in the biotherapy-maintained group. MTX-loaded BSA nanoparticles were fabricated by the desolvation method and further linked to activated folic acid to obtain FA-MTX-BSA NPs. FA-MTX-BSA NPs were successfully characterized within the nanoscale range using different screening techniques. FA-MTX-BSA NPs showed an in vitro release in a sustained manner. The potential of MTX, MTX-BSA NPs, and FA-MTX-BSA NPs in inducing cytokine level reduction was detected. Significant decreases in interleukin- 1 beta (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α) levels were obtained in cultures treated with FA-MTX-BSA NPs compared to the untreated culture in a dose-dependent pattern. Furthermore, FA-MTX-BSA NPs comparing with MTX and MTX-BSA NPs exhibited a significant advanced effect in decreasing cytokines levels. Accordingly, the conjunction of BSA NPs and MTX linked to folate potentially reduced cytokines manifestation in RA.

Socioeconomic inequality in patients with rheumatoid arthritis: a systematic review and meta-analysis

BACKGROUND

Rheumatoid arthritis is a chronic inflammatory and systemic autoimmune disease associated with synovial fluid inflammatory lesions and articular changes. The aim of the present study was to determine socioeconomic inequality in RA patients using a meta-analysis approach.

METHODS

A systematic search of national and international databases of SID, MagIran, Google Scholar, Cochrane, Embase, ScienceDirect, Scopus, PubMed, and Web of Science (WoS) was conducted to find articles published from 1988 to March 2020. Random effects model was used for analysis and heterogeneity of studies was investigated using I² index. Data analysis was then carried out using Comprehensive Meta-Analysis (Ver. 2).

RESULTS

A total of 51 articles with a total sample size of 48,195 individuals were included in the meta-analysis in all the components. The results showed that 18.9% (95% CI: 4.9-13.25%) of patients were single patients, 70.6% (95% CI: 63.5-76.8%) were married, 31.6% (95% CI: 24.5-39.7%) had low economic status, 52.1% (95% CI: 5.8-44.53%) had moderate economic status, level of education was below diploma in 33% (95% CI: 27.1-39.5%) of cases, 36.2% (95% CI: 27.3-46.1%) were smokers, and 8.8% (95% CI: 2.8-24.1%) of patients were unemployed.

CONCLUSION

The results of the present study indicate high socioeconomic inequality in RA patients in the main components of the study. Hence, to improve the aforementioned status and find causes and do the monitoring at all levels, appropriate solutions must be adopted by providing feedback to policy-makers.

KEY POINTS

• The results showed that 18.9% (95% CI: 4.9-13.25%) of patients were single patients. • 70.6% (95% CI: 63.5-76.8%) were married and 31.6% (95% CI: 24.5-39.7%) had low economic status. • 52.1% (95% CI: 5.8-44.53%) had moderate economic status; 36.2% (95% CI: 27.3-46.1%) were smokers.

Biomarkers in Rheumatoid Arthritis

The utilization and identification of biomarkers in rheumatoid arthritis (RA) to facilitate timely diagnosis and the optimal management of the disease is an area of active investigation. This review focuses on biomarkers available for routine clinical use, details potential investigational biomarkers, and raises outstanding clinical questions.

Increased disease activity in early arthritis patients with anti-carbamylated protein antibodies

The initial management of rheumatoid arthritis (RA) has a high impact on disease prognosis. Therefore, we need to select the most appropriate treatment as soon as possible. This goal requires biomarkers of disease severity and prognosis. One such biomarker may be the presence of anti-carbamylated protein antibodies (ACarPA) because it is associated with adverse long term outcomes as radiographic damage and mortality. Here, we have assessed the ACarPA as short-term prognostic biomarkers. The study was conducted in 978 prospective early arthritis (EA) patients that were followed for two years. Our results show the association of ACarPA with increased levels of all the disease activity measures in the first visit after arthritis onset. However, the associations were more significant with the high levels in local measures of inflammation and physician assessment than with the increases in systemic inflammation and patient-reported outcomes. More notably, disease activity was persistently increased in the ACarPA positive patients during the two years of follow-up. These differences were significant even after accounting for the presence of other RA autoantibodies. Therefore, the ACarPA could be considered short-term prognostic biomarkers of increased disease activity in the EA patients.

Rheumatoid Factor: A Novel Determiner in Cancer History

Simple Summary

Rheumatoid factors are autoantibodies that characterize different autoimmune diseases, in particular rheumatoid arthritis, but that can also be found in the sera of the general healthy population. They have been mainly studied in the context of autoimmune diseases, but some evidence have suggested an association between their presence and the predisposition to develop cancer as well as a facilitation of cancer growth and progression in oncologic patients. In this review, for the first time we thus analyze and discuss the possible roles that these autoantibodies can assume in tumor history, from determiners of a heightened susceptibility of developing cancer to drivers of a reduced response to immunotherapies.

Abstract

The possible interplay between autoimmunity and cancer is a topic that still needs to be deeply explored. Rheumatoid factors are autoantibodies that are able to bind the constant regions (Fc) of immunoglobulins class G (IgGs). In physiological conditions, their production is a transient event aimed at contributing to the elimination of pathogens as well as limiting a redundant immune response by facilitating the clearance of antibodies and immune complexes. Their production can become persistent in case of different chronic infections or diseases, being for instance a fundamental marker for the diagnosis and prognosis of rheumatoid arthritis. Their presence is also associated with aging. Some studies highlighted how elevated levels of rheumatoid factors (RFs) in the blood of patients are correlated with an increased cancer risk, tumor recurrence, and load and with a reduced response to anti-tumor immunotherapies. In line with their physiological roles, RFs showed in different works the ability to impair in vitro anti-cancer immune responses and effector functions, suggesting their potential immunosuppressive activity in the context of tumor immunity. Thus, the aim of this review is to investigate the emerging role of RFs as determiners of cancer faith.

IgA immunoglobulin isotype of rheumatoid factor in primary Sjögren's syndrome

Primary Sjögren’s syndrome (pSS) is an autoimmune disease with autoantibodies overproduction, including rheumatoid factors (RF). RF-IgA, IgG immunoglobulin classes are suggested as potential biomarkers of pSS. We studied 76 patients with pSS (ACR/Eular 2017); laboratory tests included ESR, C-reactive protein, concentrations of gamma globulins, RF, Anti-SS-A/Ro, and anti-SS-B/La. Eye dryness and keratoconjunctivitis sicca were confirmed with Schirmer’s test, the ocular staining score (OSS) using lissamine green, fluorescein staining and biopsy of minor salivary gland with the histopathological evaluation. Differences between groups were analyzed with U Mann–Whitney test. Correlations between quantitative variables were assessed with the Spearman correlation coefficient.. The best diagnostic values of immunoglobulin concentration for discriminating pSS patients and healthy individuals are for RF-IgA. With cut-off of 21.5 EU/mL, the sensitivity is 72% and specificity is 100%. Very high specificity (100%) is also obtained for RF-IgM concentration of 74.1 EU/mL. Sensitivity is, however, smaller than that for RF-IgA and amounted to 61%. The RF-IgG is the poorest indicator of pSS with 51% of sensitivity and 95% of specificity. To summarize RF-IgA strongly associate with anti-SS-A and anti-SS-B autoantibodies. Both RF-IgA and RF-IgM may be used as diagnostic tools for pSS. Conclusions: among the three studied rheumatoid factor subtypes, RF-IgA showed the best diagnostic accuracy for pSS. RF-IgA correlated with anti-SS-A/Ro and anti-SS-B antibodies even more closely than RF-IgM. The assessment of the RF-IgA serum concentration may be helpful in the process of establishing pSS diagnosis.

From Rheumatoid Factor to Anti-Citrullinated Protein Antibodies and Anti-Carbamylated Protein Antibodies for Diagnosis and Prognosis Prediction in Patients with Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic systemic inflammatory disease mainly involving synovial inflammation and articular bone destruction. RA is a heterogeneous disease with diverse clinical presentations, prognoses and therapeutic responses. Following the first discovery of rheumatoid factors (RFs) 80 years ago, the identification of both anti-citrullinated protein antibodies (ACPAs) and anti-carbamylated protein antibodies (anti-CarP Abs) has greatly facilitated approaches toward RA, especially in the fields of early diagnosis and prognosis prediction of the disease. Although these antibodies share many common features and can function synergistically to promote disease progression, they differ mechanistically and have unique clinical relevance. Specifically, these three RA associating auto-antibodies (autoAbs) all precede the development of RA by years. However, while the current evidence suggests a synergic effect of RF and ACPA in predicting the development of RA and an erosive phenotype, controversies exist regarding the additive value of anti-CarP Abs. In the present review, we critically summarize the characteristics of these autoantibodies and focus on their distinct clinical applications in the early identification, clinical manifestations and prognosis prediction of RA. With the advancement of treatment options in the era of biologics, we also discuss the relevance of these autoantibodies in association with RA patient response to therapy.

IgM-Rheumatoid factor confers primary resistance to anti-PD-1 immunotherapies in NSCLC patients by reducing CD137+T-cells

Background

ICIs have strongly improved the outcome of NSCLC patients. However, primary and secondary resistance occur during treatment in most of the patients, with several of them developing fast progressions. Autoantibodies can be related with a dysfunctional immune system, although their association with immune-based anti-cancer therapies has never been investigated. Moreover, so far no reliable predictive factor is currently available to aid in treatment selection. CD137⁺T-cells are largely known to be the anti-tumor activated effector cells, but they have never been associated with the response to immunotherapies.

Methods

Forty-two patients with metastatic NSCLC receiving anti-PD-1 ICIs at Sant'Andrea Hospital and Policlinico Umberto I, from June 2016 to September 2018 were enrolled. Circulating levels of IgM-Rheumatoid Factor were evaluated at baseline and correlated with patients clinical response following the anti-PD-1 treatment. IgM-RF interaction and effect on T-cells in vivo and in vitro were investigated.

Findings

IgM-RF in NSCLC patient sera strongly predicted the development of early progression to ICIs. Also, a significant reduction of progression-free survival rate in anti-PD-1 treated patients could be identified when patients were stratified based on IgM-RF positivity and titers. IgM-RF bound preferentially circulating naïve and central memory T-cells and a significant reduction of CD137⁺ anti-tumor T effector cells was found in IgM-RF positive patients. In addition, a higher percentage of CD137⁺T-cells in peripheral blood of NSCLC patients at baseline resulted as a strong independent prognostic factor for a better outcome in terms of PFS and OS after the anti-PD-1 treatment. Furthermore, T-cells exposed to IgM-RF showed a robust defect in their migratory ability in response to CCL19 chemokine.

Interpretation

In this study we showed that serum IgM-RF can be regarded as predictive factor for the development of early progression and prognostic factor of a reduced progression-free survival and overall-survival in anti-PD-1 treated NSCLC patients. The ability of IgM-RF to bind naïve and central memory T-cells and impair their migration could make account for the reduction of the tumor-reactive CD137⁺ T-cells population that may cause a non-effectiveness of these T-cells targeting drugs.

Fundings

AIRC, MIUR and Sapienza University of Rome.

Age-associated changes in the circulating human antibody repertoire are upregulated in autoimmunity

Background

The immune system undergoes a myriad of changes with age. While it is known that antibody-secreting plasma and long-lived memory B cells change with age, it remains unclear how the binding profile of the circulating antibody repertoire is impacted.

Results

To understand humoral immunity changes with respect to age, we characterized serum antibody binding to high density peptide microarrays in a diverse cohort of 1675 donors. We discovered thousands of peptides that bind antibodies in age-dependent fashion, many of which contain di-serine motifs. Peptide binding profiles were aggregated into an “immune age” by a machine learning regression model that was highly correlated with chronological age. Applying this regression model to previously-unobserved donors, we found that a donor’s predicted immune age is longitudinally consistent over years, suggesting it could be a robust long-term biomarker of humoral immune ageing. Finally, we assayed serum from donors with autoimmune disease and found a significant association between “accelerated immune ageing” and autoimmune disease activity.

Conclusions

The circulating antibody repertoire has increased binding to thousands of di-serine peptide containing peptides in older donors, which can be represented as an immune age. Increased immune age is associated with autoimmune disease, acute inflammatory disease severity, and may be a broadly relevant biomarker of immune function in health, disease, and therapeutic intervention.

Patients with Interstitial Lung Disease Secondary to Autoimmune Diseases: How to Recognize Them?

The diagnostic assessment of patients with Interstitial Lung Disease (ILD) can be challenging due to the large number of possible causes. Moreover, the diagnostic approach can be limited by the severity of the disease, which may not allow invasive exams. To overcome this issue, the referral centers for ILD organized Multidisciplinary Teams (MDTs), including physicians and experts in complementary discipline, to discuss the management of doubtful cases of ILD. MDT is currently considered the gold standard for ILD diagnosis, but it is not often simple to organize and, furthermore, rheumatologists are still not always included. In fact, even if rheumatologic conditions represent a common cause of ILD, they are sometimes difficult to recognize, considering the variegated clinical features and their association with all possible radiographic patterns of ILD. The first objective of this review is to describe the clinical, laboratory, and instrumental tests that can drive a diagnosis toward a possible rheumatic disease. The secondary objective is to propose a set of first-line tests to perform in all patients in order to recognize any possible rheumatic conditions underlying ILD.

An Overview of the Intrinsic Role of Citrullination in Autoimmune Disorders

A protein undergoes many types of posttranslation modification. Citrullination is one of these modifications, where an arginine amino acid is converted to a citrulline amino acid. This process depends on catalytic enzymes such as peptidylarginine deiminase enzymes (PADs). This modification leads to a charge shift, which affects the protein structure, protein-protein interactions, and hydrogen bond formation, and it may cause protein denaturation. The irreversible citrullination reaction is not limited to a specific protein, cell, or tissue. It can target a wide range of proteins in the cell membrane, cytoplasm, nucleus, and mitochondria. Citrullination is a normal reaction during cell death. Apoptosis is normally accompanied with a clearance process via scavenger cells. A defect in the clearance system either in terms of efficiency or capacity may occur due to massive cell death, which may result in the accumulation and leakage of PAD enzymes and the citrullinated peptide from the necrotized cell which could be recognized by the immune system, where the immunological tolerance will be avoided and the autoimmune disorders will be subsequently triggered. The induction of autoimmune responses, autoantibody production, and cytokines involved in the major autoimmune diseases will be discussed.

Label-free electrochemical impedimetric immunosensor for sensitive detection of IgM rheumatoid factor in human serum

The authors report a label-free and direct detection of rheumatoid factor- Immunoglobulin M (IgM-RF) based on an impedimetric-interdigitated wave type microelectrode array (IDWμE). IDWμE was functionalized with a self-assembled monolayer (SAM) of thioctic acid for antigen immobilization. The SAM functionalized IDWμE were characterized by atomic force microscopy, Energy Dispersive X-Ray Spectroscopy, and X-ray photoelectron spectroscopy. The covalent immobilization of IgG-Fc onto the SAM modified electrode arrays was characterized morphologically via AFM and electrochemically via cyclic voltammetry and electrochemical impedance spectroscopy. Impedimetric measurements in the presence of redox probe (Potassium ferrocyanide and potassium ferricyanide) showed a significant change in both the impedance spectrum and charge transfer resistance upon IgM-RF binding. Impedance measurements were target specific and linear with an increase in IgM-RF concentrations between 1 and 200 IU mL^-1 in redox probe and human serum, respectively. The sensor showed detection limits of 0.6 IU mL^-1 in the presence of redox probe and 0.22 IU mL^-1 in the human serum. The biosensor exhibited good reproducibility (relative standard deviation (RSD), 4.96%) and repeatability (RSD, 2.31%) with an acceptable selectivity towards IgM-RF detection. The sensor also showed a good stability for 3 weeks at 4 °C in 1X PBS. Therefore, the sensitive and stable immunosensor exhibiting IDWμE features can be integrated with a miniaturized potentiostat to develop a sensing system that detects IgM-RF for point-of-care applications.

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.

Laboratory Evaluation of Spasmodic Dysphonia

OBJECTIVES

To evaluate the utility of comprehensive laboratory evaluation in patients with spasmodic dysphonia (SD).

STUDY DESIGN

Retrospective chart review.

METHODS

A review of the medical records of 40 patients diagnosed with spasmodic dysphonia from 2009-2018 was preformed to evaluate abnormal test results that were significant when compared with abnormal results of the general population and for any other clinically relevant pathology.

RESULTS

Erythrocyte sedimentation rate, ceruloplasmin levels, and anti-AChR were found to be elevated at levels considered statistically significant (p <0.05). Furthermore, we found levels of cholesterol, thyroid-stimulating hormone (TSH), T3, fasting blood glucose, creatine kinase, immunoglobulin, antinuclear antibody (ANA), and alpha-fetoprotein (AFP) levels to be abnormal at a greater rate in our population, but these were not statistically significant. Workup revealed several underlying conditions including thyroid neoplasms, hypothyroidism, and laryngopharyngeal reflux. Additionally, brain MRI revealed age-related ischemic pathology in an elevated number of patients, but with no obvious clinical sequalae.

CONCLUSION

There is an association between serological values and spasmodic dysphonia that can aid in diagnosing pathology, as well as establishing a directed workup. Additionally, our study shows the utility of comprehensive evaluation in identifying undetected disease.

Rheumatoid factor isotype and Ro epitope distribution in primary Sjögren syndrome and rheumatoid arthritis with keratoconjunctivitis sicca

Primary Sjögren syndrome (pS) is associated with autoantibodies such as rheumatoid factor (RF) and anti-nuclear antibodies such as anti-Ro (SS-A) and/or La (SS-B). Recent developments within autoimmune diagnostics allow quantitation of RF subclasses and anti-Ro epitopes. Will this refinement by autoimmune diagnostics help predicting development of extraglandular manifestations (EGM) in pS patients? A cohort of pS and rheumatoid arthritis (RA) patients with keratoconjunctivitis sicca (n = 35 and 16, resp) was included. Of the pS patients, 54% developed one or more EGM. Antibodies quantitated were IgM-RF, IgA-RF, IgG-RF, anti-Ro52, and anti-Ro60. Upon analysis of RF isotypes, pS patients generally displayed higher IgA-RF concentrations than RA patients (126 versus 49 U/ml, p = 0.015), while the dominant RF isotype in RA patients was IgM-RF (82.5 versus 38 U/ml, p = 0.012). No differences were observed regarding IgG-RF concentrations. In pS without/with EGM, the median RF IgM concentrations were similar, while RF IgA and IgG concentrations tended to be lower in pS patients with EGM > 1. Both Ro epitopes were strongly recognized by almost all pS patients, independent from EGM, while these antibodies were absent in RA patients. Primary Sjögren syndrome and RA patients have distinct serological profiles when analysing RF and Ro-specific antibodies. A longitudinal study of switched RF isotypes in pS patients is worthwhile from an immunological point of view, but its value is limited regarding identification of pS patients prone to developing EGM or RA patients prone to developing secondary sicca symptoms.

Estimation of Posturographic Trajectory Using k-Nearest Neighbors Classifier in Patients with Rheumatoid Arthritis and Osteoarthritis

Rheumatoid arthritis (RA) and osteoarthritis (OA) are common rheumatic diseases and account for a significant percentage of disability. Posturography is a method that assesses postural stability and quantitatively evaluates postural sways. The objective of this study was to estimate posturographic trajectories applying pattern recognition algorithms. To this end, k-nearest neighbors (k-NN) classifier was used to differentiate between healthy subjects and patients with OA and RA. The following parameters of trajectories were computed: radius of sways, developed area, total length, and two directional components of sways: length of left-right and forward-backward motions. Posturographic tests were applied with eyes open and closed, and with biofeedback control. We found that in RA, the radius of sways, the trajectory area, and the biofeedback coordination were related to the patients' condition. The trajectory dynamics in OA patients were smaller compared to those in RA patients. The smallest misclassification errors were observed after feature selection in the biofeedback test compared with the eyes open and closed tests. We conclude that the estimation of posturographic trajectory with k-NN classifier could be helpful in monitoring the condition of RA patients.

Increased amount of phosphorylated proinflammatory osteopontin in rheumatoid arthritis synovia is associated to decreased tartrate-resistant acid phosphatase 5B/5A ratio

Background

Osteopontin (OPN) is an immunoregulatory protein which production increases in both rheumatoid arthritis (RA) and osteoarthritis (OA). Phosphorylated osteopontin (Phospho-OPN) is known to increase macrophage and osteoclast activation, this process is controlled by extracellular tartrate-resistant acid phosphatase (TRAcP), also a biomarker for RA. Here, we evaluated the phosphorylation status of OPN in RA and OA synovia, as well as its correlation with TRAcP isoforms.

Methods

Synovial tissue and fluid were obtained from 24 RA (14 seropositive and 10 seronegative) and 24 OA patients. Western blotting was used to analyze the extent of OPN phosphorylation. TRAcP isoforms were measured in synovial fluid using ELISA; immunohistochemistry assessed the distribution of OPN and TRAcP expressing cells in the synovial tissue, especially distinguishing between the TRAcP isoforms.

Results

Full-length OPN was more phosphorylated in RA than in OA (p<0.05). The thrombin cleaved C-terminal end of OPN was also more phosphorylated in RA (p<0.05). RA patients had a lower concentration of TRAcP 5B and higher concentration of less active 5A in their synovial fluid compared to OA patients. The TRAcP 5B/5A ratio was decreased in RA and correlated negatively with the amount of phospho-OPN (p<0.05). TRAcP positive cells for both isoforms were found all along the synovial lining; OPN antibody staining was localized in the extracellular matrix.

Conclusion

Our data suggests that in RA the synovial fluid contains insufficient amounts of TRAcP 5B which increase levels of the proinflammatory phospho-OPN. This may lead to increased macrophage and osteoclast activation, resulting in the increased local inflammation and bone resorption present in RA joints.

Immunization of BALB/c mice with pigeon IgY induces the production of anti-IgG autoantibodies

The breakdown of immunological tolerance due to the activation of autoreactive B and T cells triggers physiopathological processes. An example of such conditions is the production of IgG autoantibodies specific for the Fc portion of IgG (anti-Fcγ IgG). Previous reports have shown that patients with pigeon-related hypersensitivity pneumonitis exhibit an increase in the serum levels of anti-Fcγ IgG. There is no in vivo model for the study of this condition and the immunological mechanisms of tolerance breakdown associated with sensitization by pigeon antigens are still unknown. In this work, we show that the repeated immunization of BALB/c mice with pigeon IgY during 16-weeks induces the production of anti-Fcγ IgG and keeps their high levels for seven weeks. The late appearance of anti-Fcγ IgG autoantibodies in the plasma is similar to what has been reported in other experimental autoimmune models. With the occurrence of anti-Fcγ IgG, there is a reduction in the proportion of Foxp3 + cells (regulatory T cells, Tregs) within the population of splenic CD4 + CD25 + T cells. Thus, our data showed that the immunization of BALB/c mice with IgY promotes the production of anti-Fcγ IgG along with a decrease in Tregs in the spleen. We propose that immunization of mice with pigeon antigens, like IgY can provide a model to study the immunological mechanisms involved in the development of pigeon-related hypersensitivity pneumonitis.

Laboratory Evaluation of Vocal Fold Paralysis and Paresis

OBJECTIVES

This study aimed to assess the value of comprehensive laboratory evaluation in patients with vocal fold paralysis or paresis.

STUDY DESIGN

This is a retrospective chart review.

METHODS

Records of 231 patients with vocal fold paralysis or paresis were reviewed to determine whether there is a significant increase in the number of abnormal test results compared with rates of abnormal results for these tests in the general population and whether testing resulted in clinically important diagnosis. Laboratory data were collected from charts from initial visits from 2010 to 2014 and compared with national data.

RESULTS

When controlled for age and sex, white blood cell count was found to have a significantly higher rate of abnormal test results (P < 0.001) in patients with vocal fold paralysis or paresis than the general population. Although hemoglobin, thyroid-stimulating hormone, and thyroid antibody tests were more likely to be abnormal in our patient population, the trend was not statistically significant. Further, the prevalence of syphilis and myasthenia gravis was found to be higher in these subjects than their respective national prevalences, and the incidence of Lyme disease was found to be higher than the national prevalence of Lyme disease. Several patients were diagnosed with medically important conditions such as diabetes, thyroid dysfunction, syphilis, myasthenia gravis, and Lyme disease based on these tests.

CONCLUSION

This study suggests that comprehensive testing of patients with vocal fold movement disorders results in diagnoses that would be missed without a comprehensive evaluation, some of which are important medically, although their causal relationship to vocal fold paralysis or paresis was not investigated or established.

Development of a polystyrene latex-based reagent for rheumatoid factor detection

A rapid, specific and sensible polystyrene latex-based reagent has been developed to detect rheumatoid factor (RF) in human sera. Detection of RF is one of the criteria for rheumatoid arthritis (RA) diagnosis. RF includes immunoglobulins IgG, IgM or IgA targeting human-IgG Fc region, found in sera of 70–90% of patients with RA. Spherical, clean polystyrene particles of 480±80 nm with a Z-potential of -28 mV were synthesized. Purified gamma-globulin human blood fraction, used as IgG source, was adsorbed on particles in glycine-buffered saline with a fivefold excess of the immunoglobulins needed to saturate the calculated total surface area of the particles. The reagent was calibrated against the World Health Organization international serum reference preparation and tested with commercial positive and negative RF controls. Reactivity of the developed diagnostic reagent with human sera, either positive or negative for RF, was evaluated. The sera were tested both intact and following complement inactivation. When complement-inactivated sera were used, our reagent showed 100% coincidence of results with a commercial diagnostic kit of specificity of 80% and sensibility of 93%. The in-house reagent developed in the present work is easy to prepare and at relatively low cost, making it ideal for RF detection in low-income settings.

Cross-reactive and pre-existing antibodies to therapeutic antibodies--Effects on treatment and immunogenicity

The potential for immunogenicity is an ever-present concern during the development of biopharmaceuticals. Therapeutic antibodies occasionally elicit an antibody response in patients, which can result in loss of response or adverse effects. However, antibodies that bind a drug are sometimes found in pre-treatment serum samples, with the amount depending on drug, assay, and patient population. This review summarizes published data on pre-existing antibodies to therapeutic antibodies, including rheumatoid factors, anti-allotype antibodies, anti-hinge antibodies, and anti-glycan antibodies. Unlike anti-idiotype antibodies elicited by the drug, pre-formed antibodies in general appear to have little consequences during treatment. In the few cases where (potential) clinical consequences were encountered, antibodies were characterized and found to bind a distinct, unusual epitope of the therapeutic. Immunogenicity testing strategies should therefore always include a proper level of antibody characterization, especially when pre-formed antibodies are present. This minimizes false-positives, particularly due to rheumatoid factors, and helps to judge the potential threat in case a genuine pre-dose antibody reactivity is identified.

Balancing benefits and risks of glucocorticoids in rheumatic diseases and other inflammatory joint disorders: new insights from emerging data. An expert consensus paper from the European Society for Clinical and Economic Aspects of Osteoporosis and Osteoarthritis (ESCEO)

PURPOSE

This consensus review article considers the question of whether glucocorticoid (GC) therapy is still relevant in the treatment of rheumatic diseases, with a particular focus on rheumatoid arthritis (RA), and whether its side effects can be adequately managed. Recent basic and clinical research on the molecular, cellular and clinical effects of GCs have considerably advanced our knowledge in this field. An overview of the subject seems appropriate.

METHODS

This review is the result of a multidisciplinary expert working group, organised by European Society for Clinical and Economic Aspects of Osteoporosis and Osteoarthritis. The recent literature was surveyed and the salient evidence synthetized.

RESULTS

The pathophysiological basis of RA (and other inflammatory rheumatic diseases) now strongly implicates the adaptive immune system in addition to innate mechanisms. The molecular effect of GCs and differential GC sensitivity is better understood, although exploiting this knowledge is still in its infancy. The newer treatment strategies of early and aggressive control of RA have gr eatly improved clinical outcomes, but improvements are still possible. Newer targeted anti-inflammatory drugs have made an important impact, yet they too are associated with numerous side effects.

DISCUSSION

Short durations of moderate doses of GCs are generally well tolerated and have a positive benefit/risk ratio. Patients should be assessed for fracture risk and bone preserving agents and be prescribed calcium and vitamin D supplementation.

CONCLUSIONS

Within a strategy of a disease modifying approach to inflammatory disease, combination therapy including a GC is effective approach.

Prevalence of positive autoimmune biomarkers in the brucellosis patients

Brucellosis is a chronic infectious disease with articular involvement. Discrimination between brucellosis and rheumatologic disorders is difficult in regions endemic for brucellosis. There are few studies about the rate of positive autoantibodies as rheumatologic biomarkers in brucellosis, and the prevalence is variable. In this study, the rheumatologic tests were studied in brucellosis patients. This cross sectional study was performed in two teaching hospitals in Tehran, Iran. Forty-nine patients with brucella infection and 42 healthy participants were enrolled in this study. Brucellosis was diagnosed on the basis of the clinical symptoms and positive serology for brucellosis. Rheumatic factor (RF) and antinuclear antibodies (ANA) were evaluated in all patients. Cyclic citrullinated peptides antibody (ACPA) and anti-double strand DNA (anti-dsDNA) were checked in all patients and control groups. Out of 49 patients, 15 (30.6 %) were RF positive and 4 (8.2 %) were ANA positive. Anti-dsDNA was concurrently positive with ANA in 1 patient (2 %) but ACPA titer was positive in 8 patients (16.3 %). None of the patients with positive autoantibody biomarkers fulfilled the criteria for rheumatologic disorders. The rate of positive RF in healthy people was significantly lower than patient group (2.4 vs. 30.6 %), but the positiveness rate of other biomarkers did not have significant difference in two groups. Sixty percent of the patients with positive RF and 75 % with positive ACPA had skeletal involvement (P < 0.05). Autoantibody biomarkers can be positive in brucellosis. Rheumatologists should be aware of brucellosis in patients with musculoskeletal involvement and positive autoantibody biomarkers in endemic regions.

Fingerprinting of anti-citrullinated protein antibodies (ACPA): specificity, isotypes and subclasses

Anti-citrullinated protein antibodies (ACPA) are a family of rheumatoid arthritis (RA)-specific autoantibodies that recognize the amino acid citrulline, resulting from the post-translational modification of arginine. Peptidyl arginine deiminase, the enzyme responsible for citrullination, is present in humans in different isoforms with different tissue distribution, enzymatic activity and target specificity; nonetheless, the number of proteins citrullinated in physiological or pathological conditions is wide, but not every citrullinated protein is a target for antibodies. In pre-RA patients the immune response to citrullinated antigens is initially restricted, expands with time and, after the onset of the disease, is relatively stable. ACPA are heterogeneous in terms of not only fine specificity but also isotype and IgG subclasses usage. This heterogeneity may be relevant for the immunopathogenesis of RA, conditioning the interaction of antibodies with complement and Fc receptors.

Rheumatoid Arthritis is Associated with IgG Antibodies to Human Endogenous Retrovirus Gag Matrix: A Potential Pathogenic Mechanism of Disease?

Objective.

Human endogenous retrovirus (HERV)-K10 has been implicated in the etiology and pathogenesis of rheumatoid arthritis (RA). A secondary immune response to this virus might suggest an antigen-driven response in patients. The Gag region of HERV-K10 could provide a key epitope important for immunological reactivity. We investigated the presence of IgG antibodies to this region and assessed its significance in RA.

Methods.

We determined an antigenic peptide on the matrix segment of HERV-K10 and developed an ELISA system to detect IgG antibodies in patients with RA and controls. The presence of antibodies to the matrix peptide (denoted as MAG1: RIGKELKQAGRKGNI) was correlated with patient details.

Results.

On screening patients’ serum, we found a significantly higher mean IgG antibody response to MAG1 in 30 patients with RA as compared to 23 patients with inflammatory bowel disease (p = 0.003), 29 patients with osteoarthritis (p = 0.001), and 43 healthy individuals (p = 0.002). Reactivity was not observed to a control peptide possessing a nonhomologous amino acid sequence. On evaluating clinical details with serological activity, no correlation with disease duration (p = 0.128), sex (p = 0.768), or rheumatoid factor status (p = 0.576) was found.

Conclusion.

A significantly elevated IgG antibody response to an HERV-K10 Gag matrix peptide was observed in patients with RA, suggesting that the exposure of HERV-K10 may cause a secondary, antigenic driven immune response in RA.

Prevalence of anti-Neu5Gc antibodies in patients with hypothyroidism

BACKGROUND

N-Glycolylneuraminic acid (Neu5Gc) is a sialic acid synthesized by animals, but not by humans or birds. However, it can be incorporated in human cells and can trigger immune response. In the present study, we detected anti-Neu5Gc antibodies in samples of the general population and of patients suffering from hypothyroidism/Hashimoto's disease, which is known to have autoimmune origin.

METHODS

Antibodies were measured using enzyme-immunosorbent techniques.

RESULTS

Serum anti-Neu5Gc IgG antibodies were higher in patients with hypothyroidism (mean: 14.8 ± 15.9 μg/mL, median: 10.0 μg/mL, P = 0.0003, Mann-Whitney) and even higher in the group with Hashimoto's thyroiditis (mean: 31.1 ± 16.3 μg/mL, median: 27.2 μg/mL, P = 0.0000, Mann-Whitney) compared to the general population (mean: 5.3 ± 4.7 μg/mL, median : 4 μg/mL). All anti-TPO positive samples had anti-Neu5Gc antibody concentration higher than the mean value of the general population while anti-TPO concentration was increased as anti-Neu5Gc concentration increased. Low concentrations of IgA and IgM antibodies were measured in both general population and patient groups.

CONCLUSION

The increased values of anti-Neu5Gc antibodies in patients with hypothyroidism/Hashimoto's disease and the correlation of anti-TPO incidence with increased anti-Neu5Gc concentration raise the possibility of an association between anti-Neu5Gc antibody development and autoimmune hypothyroidism.

Posturography in patients with rheumatoid arthritis and osteoarthritis

The purpose of the paper was to investigate the usefulness of posturographic analysis in patients with rheumatoid arthritis (RA) and osteoarthritis (OA). RA is a chronic inflammatory disorder responsible for destruction of active and passive components of joints. It is the most common autoimmune disease, and the second most common form of arthritis after OA. OA is a chronic disorder characterized by irreversible changes in the joint structure developing with advancing age. Both diseases lead to the destruction of many parts of the motor system, cause pain, weakness, and damage of ligaments, muscles, bones, and articular cartilage. The etiology of the diseases remains unknown. In the present study, evaluation of body balance in the standing position was performed by means of Pro-Med force plate system. Three posturographic tests were applied: with eyes open, closed, and with the biofeedback--under conscious visual control of body movements. The following posturographic parameters were measured: the radius of sways, the developed area, and the total length of posturograms, and also two directional components of sways: the length of left-right (in frontal plane) and forward-backward (in sagittal plane) motions. The results demonstrate that the biofeedback test is most useful in the evaluation of instability in rheumatic patients; it is more powerful than the other posturographic tests evaluated.

Anticyclic citrullinated peptide antibody and rheumatoid factor in south Tunisian patients with rheumatoid arthritis: association with disease activity and severity

OBJECTIVE

To explore relationships between immunological status, clinical features, radiographic damage, disease activity, and functional disability in Tunisian patients with rheumatoid arthritis (RA).

MATERIALS AND METHODS

The study was carried out in 112 patients with RA. Demographic characteristics, disease duration, disease activity score 28 (DAS28), the Health Assessment Questionnaire (HAQ), and the Sharp/van der Heijde score were collected. Anticyclic citrullinated peptide antibody (anti-CCP) and rheumatoid factor (RF) were performed.

RESULTS

We found that anti-CCP positivity was associated with longer disease duration (P = 0.001), presence of RF (P = 4.89 × 10(-8) ), and night pain positivity (P = 0.025). Patients with positive RF had more night pain and higher anti-CCP positivity (for all P ≤ 0.05). Anti-CCP titer was correlated with disease duration (P = 0.034) and Sharp total score (P = 1.2 × 10(-4) ). Moreover, there was a significant correlation between RF and anti-CCP antibodies titers (P = 0.011). Indeed, DAS28 correlated with HAQ (P = 1.8 × 10(-7) ) and morning stiffness duration (P = 0.045). In multivariate regression analysis, the main factors associated with anti-CCP titers were radiographic damage (P = 1.625 × 10(-4) ) and RF (P = 0.013). For DAS28, only HAQ (P = 2.9 × 10(-4) ) was associated.

CONCLUSION

These findings suggest that anti-CCP antibodies are associated with RF and more severe joint damage. Moreover, disease activity is associated with functional disability.

Rheumatoid factors: clinical applications

Rheumatoid factors are antibodies directed against the Fc region of immunoglobulin G. First detected in patients with rheumatoid arthritis 70 years ago, they can also be found in patients with other autoimmune and nonautoimmune conditions, as well as in healthy subjects. Rheumatoid factors form part of the workup for the differential diagnosis of arthropathies. In clinical practice, it is recommended to measure anti-cyclic citrullinated peptide antibodies and rheumatoid factors together because anti-cyclic citrullinated peptide antibodies alone are only moderately sensitive, and the combination of the two markers improves diagnostic accuracy, especially in the case of early rheumatoid arthritis. Furthermore, different rheumatoid factor isotypes alone or in combination can be helpful when managing rheumatoid arthritis patients, from the time of diagnosis until deciding on the choice of therapeutic strategy.

The frequency of antibodies against cyclic citrullinated peptides and rheumatoid factor in healthy population: a field study of rheumatoid arthritis from northern Turkey

Rheumatoid arthritis (RA) is a chronic, systemic and an autoimmune disease characterized by inflammation of the synovial membrane that affects approximately 1 % of the total world population. Rheumatoid factor (RF) is a widely used auto antibody in diagnosis of the RA and found positive in 50-80 % of the patients but with a lower specificity. On the other hand, anti-cyclic citrullinated peptide (anti-CCP) is the latest serological marker with a specificity around 98 %. This field survey was conducted in different regions to investigate the frequency of RF and anti-CCP and also frequency of RA in a northern province of Turkey. This study was conducted in 70 local areas (12 urban and 58 rural) in the province of Tokat, which is located in northern Turkey. The population of Tokat was reported to be 828,000 at the last census and about 530,000 individuals aged > 18 years old. The study population of 941 subjects (462 male and 479 female; urban 501 and rural 440) was selected by random sampling method among 530,000 individuals. Of the 941 healthy controls assigned to the study, 479 of them were female (51 %) and 462 of them were males (49 %), and median age of all participants was 41 ± 17. Twenty-six subjects were RF positive (2.8 %), and 9 patients were anti-CCP positive (1 %). The presence of both RF and anti-CCP antibodies has also been shown in two patients (0.2 %). In conclusion, we demonstrated that the frequency of RA was 0.53 %, RF presence was 2.8 %, and anti-CCP presence was 1 % in total 941 healthy subjects enrolled into study.

The effectiveness of Echinacea extract or composite glucosamine, chondroitin and methyl sulfonyl methane supplements on acute and chronic rheumatoid arthritis rat model

The study aimed to investigate the effect of the oral administration for 15 days of either Echinacea (E) or genuphil (a composite of chondroitin sulphate, glucosamine and methyl sulfonyl methane [GCM]) nutraceutical supplements on female rat model of acute or chronic arthritis induced by bacterial outer membrane protein (OMP) from faecal flora of healthy and rheumatic humans. Anti-cyclic citrullinated peptide (anti-CCP2), C-reactive protein (CRP) and rheumatoid factor (RF) values increased ( p < 0.05) in both arthritic groups as compared to normal values. The rheumatic markers anti-CCP2, CRP and RF values decreased significantly in E- and GCM-treated groups compared to arthritic none-treated acute or chronic groups. The results of RF values of GCM-treated groups in acute and chronic models decreased exhibiting no statistical difference compared with the normal value. Histological examinations of the hind paw sections revealed moderate inflammation, oedema and mild proliferation of synovial cells in acute arthritic rats and more damage to cartilage and bone with severe inflammation in chronic ones. Echinacea acute treated group showed edema with proliferated synovial membrane and partial damage in cartilage and bone. While in the E -chronic treated group, rough edge with destructed cartilage and bone existed. However, the acute GCM group revealed mild cartilage damage. But the chronic GCM group showed mild synovial cells proliferation and revealed no inflammation with mild cartilage damage edge. Results demonstrated the OMP arthropathic property and through promising light on arthritis treatment using E- or GCM, with the advantage of GMC results over that of E -. The composite GCM is needed for further studies over the dose and duration to assess its preventive effects against the bacterial OMP arthrogenicity.

Proteolysis activity of IgM antibodies from rheumatoid arthritis patients' sera: evidence of atypical catalytic site

The IgM antibodies from rheumatoid arthritis (RA) patients' sera were screened for peptide hydrolyzing activity. Recovery of structurally intact IgM antibodies (Abs), in a single step, was achieved using a weak anion-exchange methacrylate monolith disk. The IgM Abs from patients' sera hydrolyzed the Pro-Phe-Arg-4-methyl-coumaryl-7-amide (PFR-MCA) substrate appreciably compared to the healthy donors. The apparent K(m) values of IgM Abs from patients' sera were between 0.4 and 0.7 mM. Furthermore, IgM Abs displayed 5 to 10-folds greater proteolysis activity than IgG Abs, recovered from the same pathological serum. The proteolysis activity, as a function, was found to be independent of IgM-RF titer value. Affinity labeling approach targeted at the catalytic site histidine was studied, using a specific irreversible inhibitor, N-α-tosyl-L-lysine chloromethyl ketone (TLCK). Despite modification of catalytic His, observation of serine protease like activity suggest presence of an atypical catalytic framework in a few pathological IgM Abs.

Linkage and association studies of joint morbidity from rheumatoid arthritis

OBJECTIVE

To investigate the relationship between genetic variations of rheumatoid arthritis (RA) susceptibility in terms of joint morbidity.

METHODS

We used data from Genetic Analysis Workshop 15. The Illumina linkage panel IV included 5858 single-nucleotide polymorphisms (SNP), with 5744 SNP passing quality control filters. The phenotypic variables analyzed were the level of rheumatoid factor (RF) and score on the Joint Alignment and Motion (JAM) scale. We modified the scale, dividing by RF values relevant to disease severity. Linkage analysis for affected sibling pairs was done using the MERLIN program, and family-based association tests were carried out using PLINK and FBAT software.

RESULTS

We found a high peak (LOD = 3.29; NPL Z = 4.07) near the HLA-DRB1 region on chromosome 6. The linkage at 6p24 at rs1410766 [LOD = 2.66; nonparametric linkage (NPL) Z = 3.23] was statistically significant. Two other regions also showed possible linkage peaks: chromosome 7q30 at rs322812 (LOD = 2.47; NPL Z = 3.39) and chromosome 15p34 at rs347117 (LOD = 1.95; NPL Z = 2.80). For the family-based association study, 7 SNP related to clinical RA severity were detected.

CONCLUSION

Genetic variations may lead to an enhanced risk of joint damage and increased levels of RF. Further studies are needed to elucidate the roles of other genes involved in RA and to explore whether the clinical signs of RA are associated with particular genetic variations.