Clinical and pathophysiologic relevance of autoantibodies in rheumatoid arthritis.

Rheumatoid arthritis (RA) is an autoimmune/inflammatory disease affecting 0.5 to 1% of adults worldwide and frequently leads to joint destruction and disability. Early diagnosis and early and effective therapy may prevent joint damage and lead to better long-term results. Therefore, reliable biomarkers and outcome measures are needed. Refinement of the understanding of molecular pathways involved in disease pathogenesis have been achieved by combining knowledge on RA-associated genes, environmental factors and the presence of serological elements. The presence of autoantibodies is a distinctive feature of RA. Rheumatoid Factor and Anti-Citrullinated Protein Antibodies are the two most remarkable autoantibodies in RA and provide different clinical and pathophysiological information. They precede the onset of disease symptoms and predict a more severe disease course, indicating a pathogenetic role in RA. Therefore, they promote a more accurate prognosis and contribute for a better disease management. Several RA-associated autoantibody systems have been identified: Anti-Carbamylated Antibodies, Anti-BRAF, Anti-Acetylated, Anti-PAD4 antibodies and others. Hopefully, the characterization of a comprehensive array of novel autoantibody systems in RA will provide unique pathogenic insights of relevance for the development of diagnostic and prognostic approaches compatible with an effective personalized medicine.

The idiotypic network in the regulation of autoimmunity: Theoretical and experimental studies.

The regulation of autoimmunity is a key issue in fundamental immunology. Despite outstanding achievements on this front, we currently have more questions than answers. The idea of an immune network as a regulatory mechanism is quite attractive, since it enables us to explain the selectivity (specificity), and moreover the clonality, of the regulation. Nevertheless it remains unclear how this mysterious network of immune cells is organized, how it operates, and how it exerts control over autoimmunity. This article presents an attempt to understand how the immune network functions and how it controls autoreactivity. We present a mathematical model of the immune network that is based on principles of immune network organization and function that we arrived at from a survey of the available literature. To test the principles on which the mathematical model is based, we studied the model and compared the different responses to antigen that it generated with the results obtained from experimental studies of immune response. The modeled kinetics of idiotype and anti-idiotype in response to the administration of antigen are in good agreement with the experimental kinetics of idiotypic and anti-idiotypic antibodies. To obtain evidence of the existence of idiotypic mechanisms for regulating autoimmunity, we studied a mathematical model containing autoclones and compared the model results with data from experimental studies in a model of autoimmune hemolytic anemia in mice. Because the results from the theoretical and the experimental studies coincide, there is justification to conclude that autoreactive lymphocytes are normal components of the immune network within which they are regulated. We discuss a possible molecular/cellular mechanism for negative control of autoreactive cells as affected by anti-idiotypic antibodies.

False human immunodeficiency virus test results associated with rheumatoid factors in rheumatoid arthritis.

OBJECTIVE: To investigate if immunological factors associated with rheumatoid arthritis (RA) affect the result of human immunodeficiency virus (HIV) screening by electrochemiluminescence immunoassay (ECLIA) and enzyme-linked immunosorbent assay (ELISA). METHODS: 100 RA cases were enrolled from January 2012 to February 2013 into this study. HIV screening was conducted with ECLIA detecting both HIV-1 p24 antigen, HIV-1 and HIV-2 antibodies, with ELISA and colloidal gold method detecting HIV-1 and HIV-2 antibodies. The samples producing positive results were submitted to the Center for Disease Control for confirmation using Western blotting method. The antibody titers of rheumatoid factors (RF) including RF-IgG, RF-IgM, RF-IgA, and CCP-IgG were analyzed by ELISA. RESULTS: The HIV positive-rate determined by ECLIA was significantly higher than that by ELISA and colloidal gold method (P<0.01). The false-positive rate of HIV screening was associated with antibody titers of RF-IgG, RF-IgM, RF-IgA, and CCP-IgG in RA (P<0.01). CONCLUSIONS: Immunological factors, including RF and anti-CCP antibody, may influence the screening of HIV by ECLIA, producing false-positive result.

The effect of paraproteins and rheumatoid factor on four commercial immunoassays for vancomycin: implications for laboratorians and other health care professionals.

BACKGROUND: Paraproteins, immunoglobulins (Igs), which are elevated in various autoimmune disorders, are known to interfere with various laboratory immunoassays, including vancomycin (VANC). Rheumatoid factor (RF), a known immunoassay interferant, may cause falsely elevated results. OBJECTIVES: The aims of this study were to (1) evaluate the effect of 3 paraproteins (IgA, IgG, and IgM) on 4 commercial VANC immunoassays [fluorescence polarization immunoassay; enzyme multiplied immunoassay; 2 particle-enhanced turbidimetric inhibition immunoassays]; (2) determine the concentration at which the effect is obtained, and (3) examine the influence of RF on the VANC methods. METHOD: Serum and plasma pools from patients prescribed VANC and a spiked VANC pool (20 mg/L) were each mixed 1:1 with individual patient specimens containing IgA (6-63 g/L), IgG (6-54 g/L), IgM (3-30 g/L) (n = 4 for each Ig), and a patient RF pool (196 IU/L). The mixtures (n = 39) were split and distributed for VANC analysis. RESULTS: IgA and IgG in serum and plasma did not affect any of the VANC immunoassays. RF added to plasma specimens did not interfere, but in serum, elevated VAN results were observed. IgM did not affect the fluorescence polarization immunoassay and enzyme multiplied immunoassay methods but did attenuate VANC concentrations by both particle-enhanced turbidimetric inhibition immunoassays (Siemens, Beckman Coulter), with a more pronounced effect on the latter, producing concentrations >20% lower than expected in the patient serum and spiked plasma pools. The effect was progressively negative at effective IgM concentrations of 10 and 15 mg/L. CONCLUSIONS: This phenomenon is a major analytical and clinical issue that must be communicated to health care professionals caring for patients receiving VANC, so optimal therapy is achieved.

Hepatitis C virus-related arthritis and rheumatoid arthritis: could they be different aspects of the same disease?

The role played by HCV in the genesis of many autoimmune disorders has been reported in several studies. In particular, the onset of arthritis has been described in about 2-3 percent of HCV infection cases. At present, this HCV-related arthritis is classified as a reactive arthritis, but a real distinction of this form from classical rheumatoid arthritis is often difficult. In this presentation, the Authors distinguish two arthritic forms observed in HCV-related arthritis patients: one, characterized by asymmetrical oligoarticular-involvement, and another, with poly-articular symmetrical involvement. The Authors suggest that the latter can be considered as a form of rheumatoid arthritis, because of the similarity of the main clinical aspects and laboratory findings (rheumatoid factor, anti-cyclic citrullinated peptide antibodies) to those of classical rheumatoid arthritis, which make the two forms indistinguishable. Therefore, HCV could be considered the etiologic agent of a limited number of cases of rheumatoid arthritis.

Factores predictores de respuesta a terapias biológicas en la artritis reumatoide / Predictors of response to biologic therapies in rheumatoid arthritis

El desarrollo de las terapias biológicas ha supuesto un gran avance en el manejo de la artritis reumatoide (AR) al haber demostrado efectividad en el control de la clínica y daño radiológico. Sin embargo, entre un 20-40% de los pacientes no van a responder a estas terapias, lo que determina un alto coste económico a la vez que los expone a posibles efectos adversos, por lo que se precisa de la identificación de factores predictores de respuesta a ellos. Estos se revisan en el actual trabajo en función de su evidencia científica y se clasifican en genéticos y no genéticos. A pesar de su extensa búsqueda, en la actualidad no disponemos de potentes predictores que puedan ser utilizados en la práctica clínica diaria. Posiblemente a día de hoy sólo los factores séricos, positividad del factor reumatoide (FR) y anticuerpos antipéptido citrulinado (anti-CCP), permiten predecir la respuesta a determinados biológicos. En un futuro, probablemente gracias a las nuevas tecnologías basadas en la genómica, transcriptómica y proteómica se identificarán predictores genéticos que permita seleccionar pacientes idóneos para una determinada terapia biológica(AU)

The advent of biological therapies has revolutionized the management of rheumatoid arthritis, demonstrating effectiveness in controlling clinical and radiological damage. However, 20 to 40% of the patients will not respond to these therapies, which are associated to a very high cost. In addition, non-responder patients are exposed to possible adverse effects. For these reasons, we need to identify predictors of response to these treatments. These predictors are reviewed in this evidence-based paper and classified into genetic and non-genetic. Despite extensive search, nowadays there are no predictors powerful enough to be used in regular clinical practice. Serum factors, the presence of rheumatoid factor and anti-cyclic citrullinated peptide antibodies, are the only factors currently being used to predict the response to specific biological therapy. In the future, probably thanks to new technologies based on genomics, transcriptomics and proteomics, it will be possible to identify genetic predictors of response to biological drugs that will allow us to select suitable patients for a specific biological therapy(AU)

Response to rituximab and timeframe to relapse in rheumatoid arthritis patients: association with B-cell markers.

OBJECTIVE: Rituximab is used to deplete B cells and control disease activity, mainly in patients with rheumatoid arthritis (RA) who have not responded to anti-tumor necrosis factor (TNF) therapy. Response rates and time to relapse vary significantly among treated individuals. The objective of this study was to monitor the response of seropositive and seronegative RA patients to rituximab and correlate relapse with B-cell markers in the two groups. METHODS: Seventeen RA patients (eight seropositive for rheumatoid factor [RF+] and nine seronegative [RF-]) were treated with two cycles of rituximab. After treatment, all patients were re-evaluated at the outpatient clinic, and rituximab was readministered when disease relapse was confirmed by clinical-laboratory measures (Disease Activity Score [DAS]-28). CD20+ cells and CD20 receptor expression levels were estimated at initiation, relapse, and re-evaluation timepoints, and were compared between the two groups. RESULTS: Seropositive patients responded favorably to treatment compared with the seronegative group. The mean time to relapse was 337.5 +/- 127.0 days for the RF+ patients versus 233.3 +/- 59.6 days for the RF- patients (p = 0.043), despite more aggressive concomitant treatment in the seronegative group. The DAS28 decrease 3 months after treatment was 1.695 +/- 1.076 in seropositive patients versus 0.94 +/- 1.62 in seronegative patients. At relapse, CD20 receptor expression (molecules/cell) was higher in RF+ patients than in their RF- counterparts, despite a significantly lower percentage of CD20+ cells. CONCLUSION: Rituximab treatment is efficient in both seropositive and seronegative RA. However, seropositive RA patients tend to respond favorably compared with seronegative patients. The differential CD20 receptor expression in the two groups at relapse potentially suggests a different pathogenetic mechanism of relapse and merits further investigation.

Anti-citrullinated protein/peptide antibodies (ACPA) in rheumatoid arthritis: specificity and relation with rheumatoid factor.

Anti-citrullinated protein/peptide antibodies (ACPA) are highly specific and sensitive markers for rheumatoid arthritis (RA). For instance, for the anti-CCP2 assay, sensitivities ranging from 55% to 80% and specificities ranging from 90% to 98% have been reported. Despite their high specificity, recent reports have suggested that ACPA may be found in some patients with other rheumatic autoimmune diseases, including psoriatic arthritis, systemic lupus erythematosus and Sjögren's syndrome. Also, the differences between the classical rheumatoid factor (RF) and ACPA, as well as the complementarity between both tests have recently been demonstrated more clearly. Indeed, both antibody systems have a different association with specific RA features like extra-articular manifestations, a different association with the HLA shared epitope and, behave differently following anti-TNF therapy.

Comparison of CpG s-ODNs, chromatin immune complexes, and dsDNA fragment immune complexes in the TLR9-dependent activation of rheumatoid factor B cells.

Synthetic single-stranded oligodeoxynucleotides (15-30 bp) containing CpG motifs and phosphorothioate backbones (CpG s-ODN), immune complexes consisting of anti-nucleosome mAbs and mammalian chromatin (chromatin IC), and immune complexes consisting of anti-hapten mAbs and haptenated-double stranded DNA fragments ( approximately 600 bp) can all effectively stimulate transgenic B cells expressing a rheumatoid factor receptor by a TLR9-dependent process. However, differential sensitivity to both s-ODN and small molecule inhibitors suggests that stimulatory CpG sODN and chromatin IC may either access TLR9 via different routes or depend on discrete activation parameters. These data have important implications regarding the therapeutic application of TLR9 inhibitors to the treatment of systemic autoimmune diseases.

[Neutrophils in rheumatoid inflammation]. / Il neutrofilo nella flogosi reumatoide.

For many years a secondary role in the pathogenesis of rheumatoid arthritis has been ascribed to neutrophil, relatively to the inflammatory response's evaluation. This cell was considered lacking in a peculiar activity and ever depending on lymphocytes and monocytes. During the recent years the neutrophil has been recognized as a cytokines producing cell, really able to modulate its role in joints inflammation. In the light of the latest information it's possible reconsider the role of this cell, looking at it like a moderate co-protagonist in the expression of rheumatoid damage, regarding both to joint inflammation and the maintenance of the damage itself. On the grounds of these knowledge, polymorphonuclear granulocyte could be also chosen as target of the newest therapies in the treatment of this disease. The aim of this short review is to focus the activity of neutrophils in rheumatoid arthritis, trying to follow them through their migration from blood to sinovial tissue and to understand the dynamic relation with the cytokine network, that from these cells pathway depends.

Rheumatoid factor B cell tolerance via autonomous Fas/FasL-independent apoptosis.

Normal individuals do not express the high-affinity autoantibodies specific for self-IgG (rheumatoid factors, RF) that are commonly seen in rheumatoid arthritis patients. Studies of transgenic mice expressing a human IgM rheumatoid factor have shown that one mechanism by which higher affinity RF B cells are tolerized to IgG is through abortive RF B cell activation followed by deletion in the absence of T cell help. We show that RF B cell deletion occurs through an intrinsic apoptotic mechanism that is independent of the Fas/FasL pathway and does not involve active killing by T cells, as it occurs in RAG-1-deficient RF transgenic mice to the same extent as in the parental RF transgenic line.

Are autoantibodies active players or epiphenomena?

Autoantibodies have the potential of pathogenicity in several diseases. In rheumatoid arthritis (RA), however, this has not been ultimately proven. RA is characterized by a variety of autoantibodies. Newer insights into characteristics of rheumatoid factors indirectly suggest their pathogenetic involvement. In contrast, antibodies to collagen, despite the availability of an experimental model, do not appear to be pathogenetic in man. Anti-hnRNP antibodies, particularly anti-A2/RA33, are present in RA and experimental models of RA, and therefore, aside from their diagnostic value in established and early RA, could also be involved in the disease process. The nature of Sa, another target antigen in RA, has not yet been elucidated. Filaggrin is the antigen recognized by antikeratin antibodies and antiperinuclear factor; however, citrullin is the target amino acid in filaggrin, and anticitrullin antibodies have a high predictive value. Among a series of cartilage proteins, most have not yet been characterized sufficiently; one, gp39, appears to be of particular interest. Whether or not these antibodies are involved in RA pathogenesis is not yet known. It can be speculated that autoimmunity to some, if not all, of these autoantigens mirrors events important in the development of RA, but further studies on T-cell reactivities and in experimental models are needed to fully understand the involvement.

Differential clearance of glycoforms of IgG in normal and autoimmune-prone mice.

In order to understand better the origins of the elevated levels of the glycoform of IgG that lacks galactose on both arms of the oligosaccharide chain (G0%) located in the Fc, which occurs in man and mouse with age, and in particular in autoimmune disease, we investigated the clearance of two glycosylated forms of IgG2a and IgG1 in normal (BALB/c) and autoimmune-prone (MRL/1pr, MRL/+, and non-obese diabetic (NOD)) mice. To investigate the possibility of different rates of catabolism, enzymatically generated glycoforms of monomeric IgG1 and IgG2a (fully glycosylated or G0%), were iodinated and injected into the tail vein of the mice. We found that the G0% IgG2a remained in circulation significantly longer than the fully glycosylated variants, in all of the mouse strains tested. In contrast, the two forms of IgG1 had similar kinetics in all the autoimmune-prone mice, whereas in BALB/c, there was a longer half-life (t1/2) for G0% IgG1. These data suggest that there may be differences in the ability of the IgG glycoforms to bind to the Fc gamma receptors, in particular Fc gamma RI. The clearance rates were found to vary among the strains studied, with MRL/1pr having the fastest catabolic rates for all glycoforms and IgG subclasses tested. This appeared to be due to the presence of circulating IgG and IgM rheumatoid factors (RF). There were significantly increased frequencies and titres for both IgM and IgG RF in MRL/1pr mice compared with the other strains. In contrast, interferon-gamma, known to induce the Fc gamma RI, was found to be similar in the sera, in all of the strains of mice examined. These results suggest that RF probably play an important biological function in the MRL/1pr mice and aid in the clearance of circulating IgG. Our study shows that the state of glycosylation of IgG affects the t1/2 in vivo, and that by removing the terminal sugars (sialic acid and galactose), the antibody (IgG2a) will remain in circulation significantly longer. These observations may thus provide a partial explanation for the increase in relative percentage of this glycoform that occurs with age.

[Current data on rheumatoid factors]. / Actualité des facteurs rhumatoïdes.

Rheumatoid factors are autoantibodies against the Fc fragment of IgGs. The polyclonal rheumatoid factors found in autoimmune diseases are distinct from the monoclonal rheumatoid factors produced in lymphoproliferative disorders in that they rarely express public idiotypes, are relatively specific for their Fc, and exhibit increased affinity. They may be derived from natural rheumatoid factors. The role of the latter is unclear but may involve presentation of immune complex antigens to T cells.