The role of antibodies in inflammatory arthritis

Alpha-mangostin: Anti-inflammatory and antioxidant effects on established collagen-induced arthritis in DBA/1J mice

Rheumatoid arthritis (RA) is an autoimmune disease that causes physical disability in people worldwide. Despite progress made in RA treatment in the past decade, new drugs with high efficacy but few long-term adverse effects are still needed. This study focused on evaluating the therapeutic potential of α-mangostin on established collagen-induced arthritis (CIA) in DBA/1J mice. Arthritic DBA/1J mice were orally administered with two doses of α-mangostin (10 and 40 mg/kg) daily, for 33 days. Alpha-mangostin significantly decreased the clinical score in the short term at both doses and decreased the histopathological score at the higher dose. This improvement was accompanied by a reduction on serum levels of anti-collagen IgG2a autoantibodies and of the production of LIX/CXCL5, IP-10/CXCL10, MIG/CXCL9, RANTES/CCL5, IL-6 and IL-33 in the joints of CIA mice. Alpha-mangostin also exhibited an anti-oxidant effect decreasing the NADPH oxidase activity and lipid peroxidation and preserving the levels of reduced glutathione in the arthritic joints. In vitro this xanthone demonstrated modulatory properties on LPS-activated dendritic cells, although in Th1 and Th17-polarized lymphocytes promotes a pro-apoptotic phenotype. Altogether this study illustrates the capacity of α-mangostin to ameliorate the early clinical and histological signs of established CIA by reducing the inflammatory and oxidative responses.

The Role of Autoantibodies in Bone Metabolism and Bone Loss

Many autoimmune diseases are associated with deranged bone metabolism. The resulting localized or systemic bone loss can compromise the quality of life of patients by causing local bone deformities or fragility fractures. There is emerging evidence that antibodies have a direct impact on key players of bone homeostasis, in particular osteoclasts. Clinical and pre-clinical studies provide insight into the function of autoantibodies related to Rheumatoid Arthritis (rheumatoid factor, anti-citrullinated protein antibodies, and anti-carbamylated protein antibodies) and their inflammation-independent interaction with bone cells. Furthermore, we summarize the current knowledge about neutralizing antibodies to the antiresorptive protein osteoprotegerin, which have been described in patients with Coeliac Disease, Rheumatoid Arthritis, and Spondyloarthritis.

The IL-20 receptor axis in immune-mediated inflammatory arthritis: novel links between innate immune recognition and bone homeostasis

The treatment of rheumatoid arthritis (RA) and spondyloarthritis (SpA) was transformed a little over a decade ago by the introduction of agents neutralizing the pro-inflammatory cytokine tumour necrosis factor (TNF)-α. Nevertheless, some patients do not achieve remission and the inhibition of the normal immune system with current drugs increases the risk of infection. The interleukin (IL)-20 receptor (IL-20R) axis is pivotal for tissue homeostasis. By contrast, this axis does not seem to directly activate cells of the immune system. Thus, modulation of the IL-20R axis might not result in increased risk of infection. The IL-20R axis consists of the three cytokines IL-19, IL-20, and IL-24 (termed the IL-20R cytokines) and their shared receptors. All three cytokines bind the receptor complex of IL-20R2/IL-20R1 whereas only IL-20 and IL-24 also bind the receptor complex of IL-20R2/IL-22R1. This short review describes how the IL-20R axis could be a novel link between innate immune recognition and bone homeostasis. The IL-20R cytokines are produced in response to both danger-associated molecular patterns and immune complexes formed by RA-associated autoantibodies. This could be of importance because these mediators can thus be present even in situations without inflammation. IL-19 shows anti-inflammatory properties in arthritis through IL-20R1. IL-20 and IL-24 through IL-22R seem to participate in the recruitment of mononuclear cells to the synovial joint and to sites of bone erosion in particular. Our results indicate that dual inhibition of IL-20 and IL-24 or attenuation of the shared IL-22R subunit could have a beneficial effect on radiographic progression, especially in seropositive RA.

Determination of specificity and sensitivity of anti-RA 33 in diagnosis of early rheumatoid arthritis

Background:

Rheumatoid arthritis is a chronic inflammatory disease with uncertain etiology. It is characterized by symmetric polyarthritis in peripheral joints. Its diagnosis is based on clinical findings and serologic tests. However, its diagnosis is rarely conclusive in early course of the disease. So, its early diagnosis could be difficult. The present study was designed to evaluate the role of anti -RA33; an auto-antibody against RA33 in early diagnosis of the disease.

Materials and Methods:

forty three patients with RA who had been visited in a rheumatology clinic were randomly selected. Their disease has been diagnosed by a rheumatologist. They served as the case group. 55 persons were also chosen from healthy individuals who had attended in other clinic. They served as control. Their age and sex were matched with the case group. Anti-RA33 and RF titers were measured in their blood sample using standard methods.

Findings:

RF and anti-RA33 titers had significant correlation in the case group (p=0.015). Anti -RA33 test had 98% sensitivity, 20% specificity, 50% positive predictive value, and 90% negative predictive value.

Conclusion:

Anti -RA33 could have diagnostic and prognostic importance in diagnosis and evaluation of patients with RA, and its differentiation from other small joint disorders, particularly when the other serologic tests are negative.

A simple set of validation steps identifies and removes false results in a sandwich enzyme-linked immunosorbent assay caused by anti-animal IgG antibodies in plasma from arthritis patients

Rheumatoid arthritis (RA) and spondyloarthritis (SpA) are chronic diseases characterized by activation of the immune system and production of antibodies. Thus, rheumatoid factor, anti-animal IgG antibodies and heterophilic antibodies in plasma samples from arthritis patients can interfere with immunoassays such as sandwich enzyme-linked immunosorbent assay (ELISA) systems often used in arthritis research. However, standard methodologies on how to test for false results caused by these antibodies are lacking. The objective of this study was to design a simple set of steps to validate a sandwich ELISA before using it for measuring analytes in plasma from arthritis patients. An interleukin-24 (IL-24) sandwich ELISA system was prepared with a monoclonal mouse capture antibody and a polyclonal goat detection antibody and tested for interference by rheumatoid factor, anti-animal IgG antibodies and heterophilic antibodies. Plasma samples from 23 patients with RA and SpA were used. No differences were found between plasma samples measured in wells coated with anti-IL-24 specific antibody and in wells coated with isotype control antibody (false positive results), and recombinant human IL-24 was not recovered in spiked samples (false negative results). This interference was removed after preincubating the plasma samples from patients with arthritis with goat or bovine IgG, suggesting that anti-animal IgG antibodies found in the plasma of the arthritis patients caused the false results. Additional testing showed that the signal-to-noise ratio could be increased by titration of the capture and detection antibodies and by using the ELAST amplification system. Finally, the calculated concentration of IL-24 was increased in ethylenediaminetetraacetic acid (EDTA) plasma compared to heparin plasma and serum and decreased with repetitive freeze/thaw cycles of the samples illustrating how sample handling could additionally contribute to the variations reported by different laboratories in measurement of the same analyte. This study proposes a simple set of validation steps to evaluate and optimize a sandwich ELISA before using it for measuring analytes in plasma from arthritis patients. Anti-animal IgG antibodies are also present in healthy individuals, suggesting that validation of ELISA systems for measuring non-arthritis samples could also be improved by this simple set of validation steps.

Interstitial lung disease in the connective tissue diseases

The connective tissue diseases (CTDs) are inflammatory, immune-mediated disorders in which interstitial lung disease (ILD) is common and clinically important. Interstitial lung disease may be the first manifestation of a CTD in a previously healthy patient. CTD-associated ILD frequently presents with the gradual onset of cough and dyspnea, although rarely may present with fulminant respiratory failure. Infection and drug reaction should always be ruled out. A diagnosis of idiopathic ILD should never be made without a careful search for subtle evidence of underlying CTD. Treatment of CTD-ILD typically includes corticosteroids and immunosuppressive agents.

Proteins derived from neutrophil extracellular traps may serve as self-antigens and mediate organ damage in autoimmune diseases

Neutrophils are the most abundant leukocytes in circulation and represent one of the first lines of defense against invading pathogens. Neutrophils possess a vast arsenal of antimicrobial proteins, which can be released from the cell by a death program termed NETosis. Neutrophil extracellular traps (NETs) are web-like structures consisting of decondensed chromatin decorated with granular and cytosolic proteins. Both exuberant NETosis and impaired clearance of NETs have been implicated in the organ damage of autoimmune diseases, such as systemic lupus erythematosus (SLE), small vessel vasculitis (SVV), and psoriasis. NETs may also represent an important source of modified autoantigens in SLE and SVV. Here, we review the autoimmune diseases linked to NETosis, with a focus on how modified proteins externalized on NETs may trigger loss of immune tolerance and promote organ damage.

Autoantibodies produced at the site of tissue damage provide evidence of humoral autoimmunity in inclusion body myositis

Inclusion body myositis (IBM) belongs to a group of muscle diseases known as the inflammatory myopathies. The presence of antibody-secreting plasma cells in IBM muscle implicates the humoral immune response in this disease. However, whether the humoral immune response actively contributes to IBM pathology has not been established. We sought to investigate whether the humoral immune response in IBM both in the periphery and at the site of tissue damage was directed towards self-antigens. Peripheral autoantibodies present in IBM serum but not control serum recognized self-antigens in both muscle tissue and human-derived cell lines. To study the humoral immune response at the site of tissue damage in IBM patients, we isolated single plasma cells directly from IBM-derived muscle tissue sections and from these cells, reconstructed a series of recombinant immunoglobulins (rIgG). These rIgG, each representing a single muscle-associated plasma cell, were examined for reactivity to self-antigens. Both, flow cytometry and immunoblotting revealed that these rIgG recognized antigens expressed by cell lines and in muscle tissue homogenates. Using a mass spectrometry-based approach, Desmin, a major intermediate filament protein, expressed abundantly in muscle tissue, was identified as the target of one IBM muscle-derived rIgG. Collectively, these data support the view that IBM includes a humoral immune response in both the periphery and at the site of tissue damage that is directed towards self-antigens.

Effect of a cocoa flavonoid-enriched diet on experimental autoimmune arthritis

Previously we established that a cocoa-enriched diet in young rats reduces specific antibody production and the T helper (Th) lymphocyte proportion in lymphoid tissues. The aim of the present study was to ascertain the modulatory ability of a cocoa flavonoid-enriched diet on collagen-induced arthritis (CIA), which is mediated by anti-collagen autoantibody response and Th lymphocyte activation. Female Louvain (LOU) rats were fed with a cocoa-enriched diet, beginning 2 weeks before CIA induction. Hind-paw swelling and serum cytokine and anti-collagen antibody concentrations were determined. Anti-collagen antibody-secreting cell counts and lymphocyte subset proportions were established in inguinal lymph nodes (ILN). Reactive oxygen species (ROS), nitric oxide (NO) and TNFα produced by peritoneal macrophages were determined. Although arthritic cocoa-fed rats showed a similar hind-paw swelling time course as the arthritic animals fed a standard diet, the cocoa intake was able to decrease specific IgG2a, IgG2b and IgG2c titres. Moreover, cocoa intake in CIA rats reduced ROS production, TNFα and NO release from peritoneal macrophages, and decreased the Th:cytotoxic T cell ratio in ILN. In conclusion, a cocoa flavonoid-enriched diet in LOU rats with CIA produced no effect on hind-paw swelling but was able to modulate the specific antibody response and also the Th lymphocyte proportion, as well as the synthesis of pro-inflammatory mediators from peritoneal macrophages. Therefore, a cocoa-enriched diet could be a good adjuvant therapy in disorders with oxidative stress or autoimmune pathogenesis.