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Journal of Autoimmunity Jun 2020Rheumatoid arthritis is a heterogeneous disease, which can be, based on data combining genetic risk factors and autoantibodies, sub-classified into ACPA-positive and... (Review)
Review
Rheumatoid arthritis is a heterogeneous disease, which can be, based on data combining genetic risk factors and autoantibodies, sub-classified into ACPA-positive and -negative RA. Presence of ACPA and RF as well as rising CRP-levels in some patients years before onset of clinical symptoms indicate that relevant immune responses for RA development are initiated very early. ACPA are highly specific for RA, whereas RF can also be found among healthy (elderly) individuals and patients with other autoimmune diseases or infection. The most important genetic risk factor for RA development, the shared epitope alleles, resides in the MHC class II region. Shared epitope alleles, however, only predispose to the development of ACPA-positive RA. Smoking is thus far the most important environmental risk factor associated with the development of RA. Studies on synovitis have shown the importance not only of adaptive but also of innate immune responses. In summary of the various results from immunological changes in blood and synovial tissue, the extension of the immune response from a diffuse myeloid to a lympho-myeloid inflammation appears to be associated with a more successful therapeutic response to biologics. With respect to advances in synovitis research, new targets for treatment against pathological subsets of immune cells or fibroblasts are already on the horizon. However, alternative strategies involving the microbiome may play an important role as well and research in this field is growing rapidly.
Topics: Animals; Arthritis, Rheumatoid; Autoantibodies; Autoantigens; Autoimmunity; Biomarkers; Disease Susceptibility; Environment; Genetic Predisposition to Disease; Humans; Microbiota; Prognosis; Rheumatoid Factor; Risk Factors
PubMed: 31980337
DOI: 10.1016/j.jaut.2019.102400 -
Disease Markers 2013Rheumatoid 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... (Review)
Review
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.
Topics: Arthritis, Rheumatoid; Autoimmune Diseases; Biomarkers; Humans; Immunoglobulin G; Prognosis; Rheumatoid Factor
PubMed: 24324289
DOI: 10.1155/2013/726598 -
PloS One 2019Antibodies are important for immunity and exist in several classes (IgM, IgD, IgA, IgG, IgE). They are composed of symmetric dimeric molecules with two antigen binding...
Antibodies are important for immunity and exist in several classes (IgM, IgD, IgA, IgG, IgE). They are composed of symmetric dimeric molecules with two antigen binding regions (Fab) and a constant part (Fc), usually depicted as Y-shaped molecules. Rheumatoid factors found in patients with rheumatoid arthritis are autoantibodies binding to IgG and paradoxically appear to circulate in blood alongside with their antigen (IgG) without reacting with it. Here, it is shown that rheumatoid factors do not react with native IgG in solution, and that their epitopes only become accessible upon certain physico-chemical treatments (e.g. heat treatment at 57 °C), by physical adsorption on a hydrophobic surface or by antigen binding. Moreover, chemical cross-linking in combination with mass spectrometry showed that the native state of IgG is a compact (closed) form and that the Fab parts of IgG shield the Fc region and thereby control access of rheumatoid factors and presumably also some effector functions. It can be inferred that antibody binding to pathogen surfaces induces a conformational change, which exposes the Fc part with its effector sites and rheumatoid factor epitopes. This has strong implications for understanding antibody structure and physiology and necessitates a conceptual reformulation of IgG models.
Topics: Arthritis, Rheumatoid; Epitopes; Humans; Immunoglobulin Fc Fragments; Immunoglobulin G; Protein Structure, Quaternary; Rheumatoid Factor; Structure-Activity Relationship
PubMed: 31199818
DOI: 10.1371/journal.pone.0217624 -
Frontiers in Immunology 2021Measurement of two groups of autoantibodies, rheumatoid factor (RF) and anti-citrullinated protein/peptide antibodies (ACPA) have gained increasing significance in the... (Review)
Review
Measurement of two groups of autoantibodies, rheumatoid factor (RF) and anti-citrullinated protein/peptide antibodies (ACPA) have gained increasing significance in the diagnosis and classification of rheumatoid arthritis (RA) over the last 65 years. Despite this rising importance of autoimmune serology in RA, there is a palpable lack of harmonization between different commercial RF and ACPA tests. While a minimal diagnostic specificity has been defined for RF tests, which almost always are related to an international reference preparation, neither of this applies to ACPA. Especially assays with low diagnostic specificity are associated with very low positive predictive values or post-test probabilities in real world settings. In this review we focus on issues of practical bearing for the clinical physician diagnosing patients who potentially have RA, or treating patients diagnosed with RA. We advocate that all clinically used assays for RF and ACPA should be aligned to a common diagnostic specificity of 98-99% compared to healthy controls. This high and rather narrow interval corresponds to the diagnostic specificity seen for many commercial ACPA tests, and represents a specificity that is higher than what is customary for most RF assays. Data on antibody occurrence harmonized in this way should be accompanied by test result-specific likelihood ratios for the target diagnosis RA on an ordinal or interval scale, which will provide the clinical physician with more granular and richer information than merely relating numerical values to a single cut-off point. As many physicians today are used to evaluate autoantibodies as positive or negative on a nominal scale, the introduction of test result-specific likelihood ratios will require a change in clinical mindset. We also discuss the use of autoantibodies to prognosticate future arthritis development in at-risk patients as well as predict severe disease course and outcome of pharmacological treatment.
Topics: Anti-Citrullinated Protein Antibodies; Arthritis, Rheumatoid; Disease Progression; Humans; Immunoassay; Likelihood Functions; Predictive Value of Tests; Randomized Controlled Trials as Topic; Reproducibility of Results; Rheumatoid Factor
PubMed: 34054878
DOI: 10.3389/fimmu.2021.685312 -
Clinical Reviews in Allergy & Immunology Oct 2022Autoantibodies represent a hallmark of rheumatoid arthritis (RA), with the rheumatoid factor (RF) and antibodies against citrullinated proteins (ACPA) being the most... (Review)
Review
Autoantibodies represent a hallmark of rheumatoid arthritis (RA), with the rheumatoid factor (RF) and antibodies against citrullinated proteins (ACPA) being the most acknowledged ones. RA patients who are positive for RF and/or ACPA ("seropositive") in general display a different etiology and disease course compared to so-called "seronegative" patients. Still, the seronegative patient population is very heterogeneous and not well characterized. Due to the identification of new autoantibodies and advancements in the diagnosis of rheumatic diseases in the last years, the group of seronegative patients is constantly shrinking. Aside from antibodies towards various post-translational modifications, recent studies describe autoantibodies targeting some native proteins, further broadening the spectrum of recognized antigens. Next to the detection of new autoantibody groups, much research has been done to answer the question if and how autoantibodies contribute to the pathogenesis of RA. Since autoantibodies can be detected years prior to RA onset, it is a matter of debate whether their presence alone is sufficient to trigger the disease. Nevertheless, there is gathering evidence of direct autoantibody effector functions, such as stimulation of osteoclastogenesis and synovial fibroblast migration in in vitro experiments. In addition, autoantibody positive patients display a worse clinical course and stronger radiographic progression. In this review, we discuss current findings regarding different autoantibody types, the underlying disease-driving mechanisms, the role of Fab and Fc glycosylation and clinical implications.
Topics: Arthritis, Rheumatoid; Autoantibodies; Humans; Rheumatoid Factor
PubMed: 34495490
DOI: 10.1007/s12016-021-08890-1 -
Clinical Chemistry and Laboratory... Sep 2022Rheumatoid factor (RF) is a well-established marker for the diagnosis and classification of rheumatoid arthritis (RA). Most studies evaluated IgM RF or...
OBJECTIVES
Rheumatoid factor (RF) is a well-established marker for the diagnosis and classification of rheumatoid arthritis (RA). Most studies evaluated IgM RF or isotype-nonspecific total RF assays. We evaluated the added value of IgA RF in this context.
METHODS
An international sample cohort consisting of samples from 398 RA patients and 1073 controls was tested for IgA RF with 3 commercial assays. For all RA patients and 100 controls essential clinical and serological data for ACR/EULAR classification were available.
RESULTS
The sensitivity of IgA RF for diagnosing RA was lower than the sensitivity of IgM RF. Differences in numerical values between IgA RF assays were observed. With all assays, the highest IgA RF values were found in patients with primary Sjögren's syndrome. Double positivity for IgM RF and IgA RF had a higher specificity for RA than either IgM RF or IgA RF. The sensitivity of double positivity was lower than the sensitivity of either IgA RF or IgM RF. Single positivity for IgA RF was at least as prevalent in controls than in RA patients. Adding IgA RF to IgM RF and anti-citrullinated protein antibodies (ACPA) did not affect RA classification. However, combined positivity for IgA RF, IgM RF and IgG ACPA had a higher specificity and lower sensitivity for RA classification than positivity for either of the antibodies.
CONCLUSIONS
IgA RF showed a lower sensitivity than IgM RF. Combining IgA RF with IgM RF and ACPA did not improve sensitivity of RA classification. Combined positivity (IgA-RF/IgM-RF/ACPA) increased specificity.
Topics: Arthritis, Rheumatoid; Humans; Immunoglobulin A; Immunoglobulin M; Peptides, Cyclic; Rheumatoid Factor; Sensitivity and Specificity
PubMed: 35790193
DOI: 10.1515/cclm-2022-0244 -
Respirology (Carlton, Vic.) Oct 2022
Topics: Arthritis, Rheumatoid; Humans; Lung Diseases, Interstitial; Rheumatoid Factor
PubMed: 35950227
DOI: 10.1111/resp.14343 -
Frontiers in Immunology 2022Rheumatoid arthritis is an autoimmune disease characterized by joint inflammation due to autoantibodies targeting multiple self-proteins. Most patients with poor...
Rheumatoid arthritis is an autoimmune disease characterized by joint inflammation due to autoantibodies targeting multiple self-proteins. Most patients with poor prognosis show elevated titers of IgM antibodies specifically binding to IgG. Such autoreactive antibodies are referred to as rheumatoid factor (RF). However, their biological function and contribution to disease progression remains elusive. We have recently shown that autoreactive antibodies are present in healthy individuals and play an important role in regulating physiological processes. This regulatory mechanism is determined by the class and affinity of the autoreactive antibody, as low-affinity autoreactive IgM neutralizes the recognized autoantigen while high-affinity IgM protects its autoantigen from degradation. Here, we show that RFs possessing a high affinity and mono-specificity to IgG have a stabilizing effect on IgG, whereas low-affinity polyreactive RFs neutralize IgG . These results suggest that autoreactive IgM antibodies recognizing IgG play a crucial role in regulating IgG homeostasis and that a disbalance between IgM-mediated IgG degradation and stabilization might affect the onset and progression of autoimmune diseases. Consequently, restoring this balance using low-affinity anti-IgG IgM might be a promising therapeutic approach for autoimmune diseases involving autoreactive IgG.
Topics: Humans; Rheumatoid Factor; Autoantibodies; Immunoglobulin M; Arthritis, Rheumatoid; Autoantigens; Homeostasis
PubMed: 36341420
DOI: 10.3389/fimmu.2022.1016263 -
The Israel Medical Association Journal... Jul 2019Serum rheumatoid factors are autoantibodies of different isotypes directed against the Fc fraction of immunoglobulin G (IgG) and represent paradigmatic autoantibodies... (Review)
Review
Serum rheumatoid factors are autoantibodies of different isotypes directed against the Fc fraction of immunoglobulin G (IgG) and represent paradigmatic autoantibodies that have been largely used in clinical practice for decades. Traditionally IgG has been associated with rheumatoid arthritis and more recently included also in the classification criteria for Sjӧgren's syndrome. Researchers have established that rheumatoid factors are positive in a variety of infectious, autoimmune, and neoplastic disorders, thus requiring a comprehensive evaluation of seropositive patients. Of note, hepatitis B and C viruses represent a crossroad that includes the high rheumatoid factor seroprevalence and chronic inflammatory disease, as well as progression to non-Hodgkin's lymphomas. Chronic antigen stimulation is the likely common ground of these processes and rheumatoid factors may represent mere bystanders or drivers of pathology. Mixed cryoglobulinemia and lymphoproliferative disease are prime examples of the deleterious effects of rheumatoid factor-B cell activity, possibly associated with hepatitis B and C. More importantly, they show a clear association in a physiological host response to infection, chronic inflammation, and the slide toward autoimmunity and malignancy. The association between hepatitis B and C infections and the appearance of serum rheumatoid factors is further supported by prevalence data, which support a coexistence of these markers in a significant proportion of cases, with viral infections being frequent causes of rheumatoid factors in patients without a rheumatic condition. We provide a comprehensive overview of the known connections between hepatitis B and C infections and rheumatoid factors.
Topics: Autoantibodies; Autoimmune Diseases; Autoimmunity; Cryoglobulinemia; Hepatitis B; Hepatitis C; Humans; Lymphoproliferative Disorders; Neoplasms; Rheumatoid Factor
PubMed: 31507125
DOI: No ID Found -
Mediators of Inflammation 2015Periodontitis (PD) and rheumatoid arthritis (RA) are immunoinflammatory diseases where leukocyte infiltration and inflammatory mediators induce alveolar bone loss,... (Review)
Review
Periodontitis (PD) and rheumatoid arthritis (RA) are immunoinflammatory diseases where leukocyte infiltration and inflammatory mediators induce alveolar bone loss, synovitis, and joint destruction, respectively. Thus, we reviewed the relationship between both diseases considering epidemiological aspects, mechanical periodontal treatment, inflammatory mediators, oral microbiota, and antibodies, using the keywords "periodontitis" and "rheumatoid arthritis" in PubMed database between January 2012 and March 2015, resulting in 162 articles. After critical reading based on titles and abstracts and following the inclusion and exclusion criteria, 26 articles were included. In the articles, women over 40 years old, smokers and nonsmokers, mainly constituted the analyzed groups. Eight studies broached the epidemiological relationship with PD and RA. Four trials demonstrated that the periodontal treatment influenced the severity of RA and periodontal clinical parameters. Nine studies were related with bacteria influence in the pathogenesis of RA and the presence of citrullinated proteins, autoantibodies, or rheumatoid factor in patients with PD and RA. Five studies investigated the presence of mediators of inflammation in PD and RA. In summary, the majority of the articles have confirmed that there is a correlation between PD and RA, since both disorders have characteristics in common and result from an imbalance in the immunoinflammatory response.
Topics: Animals; Arthritis, Rheumatoid; Humans; Inflammation; Periodontitis; Rheumatoid Factor
PubMed: 26347200
DOI: 10.1155/2015/259074