The immunologic homunculus in rheumatoid arthritis

Resveratrol Attenuates Rheumatoid Arthritis Induce Neutrophil Extracellular Traps via TLR-4 Mediated Inflammation in C57BL/6 Mice

The objective of this study was to evaluate whether RSV inhibits neutrophil extracellular traps (NETs) that induce joint hyperalgesia in C57BL/6 mice after adjuvant-induced arthritis. A subplantar injection of Freund's complete adjuvant was administered to C57BL/6 mice on day 0 for immunization in the AIA model. Resveratrol (RSV, 25 mg/kg) was administered intraperitoneally once daily starting on day 22 and continuing for two weeks. The effects of mechanical hyperalgesia and edema formation have been assessed in addition to histopathological scoring. Mice were sacrificed on day 35 to determine cytokine levels and PADI4 and COX-2 expression levels. ELISA was used to quantify neutrophil extracellular traps (NETs) along with neutrophil elastase-DNA and myeloperoxidase-DNA complexes in neutrophils. An immunohistochemical stain was performed on knee joints to determine the presence of nuclear factor kappa B p65 (NF-kappaB p65). AIA mice were found to have higher levels of NET in joints and their joint cells demonstrated an increased expression of the PADI4 gene. Treatment with RSV in AIA mice (25 mg/kg, i.p.) significantly (P<0.05) inhibited joint hyperalgesia, resulting in a significant increase in mechanical threshold, a decrease in articular edema, a decrease in the production of inflammatory cytokines, increased COX-2 expression, and a decrease in the immunostaining of NF-kappaB. Furthermore, treatment with RSV significantly reduced the amount of neutrophil elastase (NE)-DNA and MPO-DNA complexes, which were used as indicators of NET formation (P<0.05). This study indicates that RSV reduces NET production and hyperalgesia by reducing inflammation mediated by PADI4 and COX-2. According to these data, NETs contribute to joint pain and resveratrol can be used to treat pain in RA through this pathway.

Intra-articular nanoparticles based therapies for osteoarthritis and rheumatoid arthritis management

Osteoarthritis (OA) and rheumatoid arthritis (RA) are chronic and progressive inflammatory joint diseases that affect a large population worldwide. Intra-articular administration of various therapeutics is applied to alleviate pain, prevent further progression, and promote cartilage regeneration and bone remodeling in both OA and RA. However, the effectiveness of intra-articular injection with traditional drugs is uncertain and controversial due to issues such as rapid drug clearance and the barrier afforded by the dense structure of cartilage. Nanoparticles can improve the efficacy of intra-articular injection by facilitating controlled drug release, prolonged retention time, and enhanced penetration into joint tissue. This review systematically summarizes nanoparticle-based therapies for OA and RA management. Firstly, we explore the interaction between nanoparticles and joints, including articular fluids and cells. This is followed by a comprehensive analysis of current nanoparticles designed for OA/RA, divided into two categories based on therapeutic mechanisms: direct therapeutic nanoparticles and nanoparticles-based drug delivery systems. We highlight nanoparticle design for tissue/cell targeting and controlled drug release before discussing challenges of nanoparticle-based therapies for efficient OA and RA treatment and their future clinical translation. We anticipate that rationally designed local injection of nanoparticles will be more effective, convenient, and safer than the current therapeutic approach.

Identifying the hub genes and immune infiltration related to pyroptosis in rheumatoid arthritis

Rheumatoid arthritis (RA) is one of the most common autoimmune joint disorders globally, but its pathophysiological mechanisms have not been thoroughly investigated. Pyroptosis significantly correlates with programmed cell death. However, targeting pyroptosis has not been considered as a therapeutic strategy in RA due to a lack of systematic studies on validated biomarkers. The present study aimed to identify hub pyroptosis biomarkers and immune infiltration in RA. The gene expression profiles of synovial tissues were obtained from the Gene Expression Omnibus (GEO) database to identify differentially expressed pyroptosis genes (DEPGs). Meanwhile, the CIBERSORT algorithm was used to explore the association between immune infiltration and RA. Consequently, two hub DEPGs (EGFR and JUN) were identified as critical genes in RA. Through gene ontology and pathway enrichment analysis. EGFR and JUN were found to be primarily involved in the ErbB signaling pathway, PD-1 checkpoint pathway, GnRH signaling pathway, etc. Furthermore, for immune infiltration analysis, the pyroptosis genes EGFR and JUN were closely connected with four and one immune cell types, respectively. Overall, this study presents a novel method to identify hub DEPGs and their correlation with immune infiltration, which may provide novel perspectives into the diagnosis and treatment of patients with RA.

Neutrophil extracellular traps mediate joint hyperalgesia induced by immune inflammation

OBJECTIVE

To evaluate the role of neutrophil extracellular traps (NETs) in the genesis of joint hyperalgesia using an experimental model of arthritis and transpose the findings to clinical investigation.

METHODS

C57BL/6 mice were subjected to antigen-induced arthritis (AIA) and treated with Pulmozyme (PLZ) to degrade NETs or Cl-amidine to inhibit NET production. Oedema formation, the histopathological score and mechanical hyperalgesia were evaluated. NETs were injected intra-articularly in wild type (WT), Tlr4-/-, Tlr9-/-, Tnfr1-/- and Il1r-/- mice, and the levels of cytokines and Cox2 expression were quantified. NETs were also quantified from human neutrophils isolated from RA patients and individual controls.

RESULTS

AIA mice had increased NET concentration in joints, accompanied by increased Padi4 gene expression in the joint cells. Treatment of AIA mice with a peptidyl arginine deiminase 4 inhibitor or with PLZ inhibited the joint hyperalgesia. Moreover, the injection of NETs into joints of naïve animals generated a dose-dependent reduction of mechanical threshold, an increase of articular oedema, inflammatory cytokine production and cyclooxygenase-2 expression. In mice deficient for Tnfr1, Il1r, Tlr4 and Tlr9, joint hyperalgesia induced by NETs was prevented. Last, we found that neutrophils from RA patients were more likely to release NETs, and the increase in synovial fluid NET concentration correlated with an increase in joint pain.

CONCLUSION

The findings indicate that NETs cause hyperalgesia possibly through Toll-like receptor (TLR)-4 and TLR-9. These data support the idea that NETs contribute to articular pain, and this pathway can be an alternative target for the treatment of pain in RA.

Neutrophil extracellular traps mediate articular cartilage damage and enhance cartilage component immunogenicity in rheumatoid arthritis

Rheumatoid arthritis (RA) is characterized by synovial joint inflammation, cartilage damage, and dysregulation of the adaptive immune system. While neutrophil extracellular traps (NETs) have been proposed to play a role in the generation of modified autoantigens and in the activation of synovial fibroblasts, it remains unknown whether NETs are directly involved in cartilage damage. Here, we report a new mechanism by which NET-derived elastase disrupts cartilage matrix and induces release of membrane-bound peptidylarginine deiminase-2 by fibroblast-like synoviocytes (FLSs). Cartilage fragments are subsequently citrullinated, internalized by FLSs, and then presented to antigen-specific CD4+ T cells. Furthermore, immune complexes containing citrullinated cartilage components can activate macrophages to release proinflammatory cytokines. HLA-DRB1*04:01 transgenic mice immunized with NETs develop autoantibodies against citrullinated cartilage proteins and display enhanced cartilage damage. Inhibition of NET-derived elastase rescues NET-mediated cartilage damage. These results show that NETs and neutrophil elastase externalized in these structures play fundamental pathogenic roles in promoting cartilage damage and synovial inflammation. Strategies targeting neutrophil elastase and NETs could have a therapeutic role in RA and in other inflammatory diseases associated with inflammatory joint damage.

Autoantibody Biomarkers in Rheumatic Diseases

Autoantibodies encountered in patients with systemic rheumatic diseases bear clinical significance as a biomarker to help or predict diagnosis, clinical phenotypes, prognosis, and treatment decision-making. Furthermore, evidence has accumulated regarding the active involvement of disease-specific or disease-associated autoantibodies in the pathogenic process beyond simple association with the disease, and such knowledge has become essential for us to better understand the clinical value of autoantibodies as a biomarker. This review will focus on the current update on the autoantibodies of four rheumatic diseases (rheumatoid arthritis, myositis, systemic sclerosis, and anti-neutrophil cytoplasmic antibody associated vasculitis) where there has been a tremendous progress in our understanding on their biological effects and clinical use.

Identification of differentially expressed genes in synovial tissue of rheumatoid arthritis and osteoarthritis in patients

Rheumatoid arthritis (RA) and osteoarthritis (OA) are the common joints disorder in the world. Although they have showed the analogous clinical manifestation and overlapping cellular and molecular foundation, the pathogenesis of RA and OA were different. The pathophysiologic mechanisms of arthritis in RA and OA have not been investigated thoroughly. Thus, the aim of study is to identify the potential crucial genes and pathways associated with RA and OA and further analyze the molecular mechanisms implicated in genesis. First, we compared gene expression profiles in synovial tissue between RA and OA from the National Center of Biotechnology Information (NCBI) Gene Expression Omnibus (GEO) database. Gene Expression Series (GSE) 1919, GSE55235, and GSE36700 were downloaded from the GEO database, including 20 patients of OA and 21 patients of RA. Differentially expressed genes (DEGs) including "CXCL13," "CD247," "CCL5," "GZMB," "IGKC," "IL7R," "UBD///GABBR1," "ADAMDEC1," "BTC," "AIM2," "SHANK2," "CCL18," "LAMP3," "CR1," and "IL32." Second, Gene Ontology analyses revealed that DEGs were significantly enriched in integral component of extracellular space, extracellular region, and plasma membrane in the molecular function group. Signaling pathway analyses indicated that DEGs had common pathways in chemokine signaling pathway, cytokine-cytokine receptor interaction, and cytosolic DNA-sensing pathway. Third, DEGs showed the complex DEGs protein-protein interaction network with the Coexpression of 83.22%, Shared protein domains of 8.40%, Colocalization of 4.76%, Predicted of 2.87%, and Genetic interactions of 0.75%. In conclusion, the novel DEGs and pathways between RA and OA identified in this study may provide new insight into the underlying molecular mechanisms of RA.

Synovial fibroblast-neutrophil interactions promote pathogenic adaptive immunity in rheumatoid arthritis

Rheumatoid arthritis (RA) is characterized by synovial joint inflammation and by development of pathogenic humoral and cellular autoimmunity to citrullinated proteins. Neutrophil extracellular traps (NETs) are a source of citrullinated autoantigens and activate RA synovial fibroblasts (FLS), cells crucial in joint damage. We investigated the molecular mechanisms by which NETs promote proinflammatory phenotypes in FLS, and whether these interactions generate pathogenic anti-citrulline adaptive immune responses. NETs containing citrullinated peptides are internalized by FLS through a RAGE-TLR9 pathway promoting FLS inflammatory phenotype and their upregulation of MHC class II. Once internalized, arthritogenic NET-peptides are loaded into FLS MHC class II and presented to Ag-specific T cells. HLADRB1*0401 transgenic mice immunized with mouse FLS loaded with NETs develop antibodies specific to citrullinated forms of relevant RA autoantigens implicated in RA pathogenesis as well as cartilage damage. These results implicate FLS as mediators in RA pathogenesis, through the internalization and presentation of NET citrullinated peptides to the adaptive immune system leading to pathogenic autoimmunity and cartilage damage.

Differential activation of endocrine-immune networks by arthritis challenge: Insights from colony-specific responses

Rheumatoid arthritis (RA) is a chronic inflammatory condition with variable clinical presentation and disease progression. Importantly, animal models of RA are widely used to examine disease pathophysiology/treatments. Here, we exploited known vendor colony-based differences in endocrine/immune responses to gain insight into inflammatory modulators in arthritis, utilizing the adjuvant-induced arthritis (AA) model. Our previous study found that Sprague-Dawley (SD) rats from Harlan develop more severe AA, have lower corticosteroid binding globulin, and have different patterns of cytokine activation in the hind paw, compared to SD rats from Charles River. Here, we extend these findings, demonstrating that Harlan rats show reduced hypothalamic cytokine responses to AA, compared to Charles River rats, and identify colony-based differences in cytokine profiles in hippocampus and spleen. To go beyond individual measures, probing for networks of variables underlying differential responses, we combined datasets from this and the previous study and performed constrained principal component analysis (CPCA). CPCA revealed that with AA, Charles River rats show activation of chemokine and central cytokine networks, whereas Harlan rats activate peripheral immune/hypothalamic-pituitary-adrenal networks. These data suggest differential underlying disease mechanism(s), highlighting the power of evaluating multiple disease biomarkers, with potential implications for understanding differential disease profiles in individuals with RA.

Function of the sympathetic supply in acute and chronic experimental joint inflammation

Joints are densely innervated by postganglionic sympathetic nerve fibers. These fibers control the blood flow in the joint and vascular permeability, either directly or indirectly, in cooperation with leukocytes. Chemical sympathectomy or suppression of adrenergic signaling significantly reduces inflammatory processes in the initial acute state of inflammation whereas the same procedures may increase inflammation at later stages. These findings indicate that the sympathetic nervous system supports the development of inflammation but may reduce inflammation at more chronic stages. During chronic inflammation the density of sympathetic nerve fibers in synovial tissue is reduced but other tyrosine hydroxylase-positive cells secreting noradrenaline appear in the inflamed joint. In addition to local vascular effects in the joint, the sympathetic nervous system influences numerous immune processes in the joint and in lymphoid organs. Hence the net effect of the sympathetic nervous system on inflamed tissue results from local sympathetic effects in the joint as well as from sympathetic influences on major systemic immune processes.

Induction of proliferation and pro-inflammatory cytokine production in rheumatoid arthritis peripheral blood mononuclear cells by a 65 KDa chondrocyte membrane-specific, constitutive target autoantigen (CH65)

OBJECTIVE

To analyze proliferation and pro-inflammatory cytokine production of peripheral blood mononuclear cells (PBMC) from rheumatoid arthritis (RA) patients following stimulation with a purified chondrocyte membrane-associated autoantigen (CH65).

METHODS

CH65 was highly purified from bovine chondrocyte membranes by solubilization and ion exchange chromatography. PBMC of RA patients (n = 37; 28 seropositive, nine seronegative) and non-arthritic donors (n = 20) were isolated by ficoll centrifugation and used in cell proliferation assays. The levels of interleukin (IL)-1, tumo necrosis factor (TNF) and IL-6 produced after stimulation with CH65 were determined by enzyme-linked immunosorbent assay (ELISA). Statistical analysis was performed using Mann-Whitney U-test and Spearman rank test and the software SPSS 13.0^TM (SPSS Inc.; Chicago, IL, USA).

RESULTS

Peripheral blood mononuclear cells exhibited a strong proliferative response to purified CH65 in approximately 50% of the RA patients (seropositive > seronegative), with a maximum reactivity at 0.15 or 0.30 μg/mL culture medium. In contrast, PBMC from normal donors did not show a proliferative response to CH65 at any dose. The proliferative response in RA patients peaked at days 7-9 and returned to control levels at day 13, indicating an antigen-driven process. CH65-stimulated RA PBMC produced moderate to high amounts of IL-1, TNF and IL-6. This was comparable to the response after exposure to isolated whole chondrocyte membranes or purified collagen type II.

CONCLUSION

These results demonstrate a significant cellular immune response to CH65 protein in RA patients. Given the high similarity between bovine and human CH65, the results suggest a pathogenetic involvement of this molecule as a cartilage-specific potential target autoantigen in RA.

Adaptive immunity in rheumatic diseases: bystander or pathogenic player?

Rheumatic diseases comprise a wide spectrum of different conditions. Some are caused by disturbances of the adaptive immune system, while defects in innate immune responses have been identified for others. In between are a variety of multifactorial diseases for which the evidence for a causative involvement of the adaptive immune system is still controversial. In these cases, availability of novel drugs that target key players of the adaptive immune system have improved our understanding of the relevance of adaptive immunity to the disease process, but it has also generated unprecedented findings. Rheumatoid arthritis (RA) is a prototypic example of a disease in which the relative contribution of adaptive immunity to disease pathogenesis is incompletely understood. Although numerous markers have been identified that reflect an activated adaptive immune system, several caveats render interpretation of these findings difficult. For one, the very early immune responses initiating disease are likely to take place before an individual is identified as a patient, and are thus difficult to study in the human. Furthermore, increasing evidence points to pathogenetically distinct subgroups within the clinical diagnosis RA, offering the possibility that adaptive immune responses might be relevant to one subgroup but not the other. In addition, many indications for an adaptive immune system involvement are based on associations for which the underlying mechanism is often unknown. Finally, therapeutic interventions targeting the adaptive immune system have generated heterogeneous results. The present review addresses these issues by placing adaptive immune responses in the context of rheumatic diseases, and by reviewing the evidence for a contribution of adaptive immunity to RA.

Cytokine measurements and possible interference from heterophilic antibodies--problems and solutions experienced with rheumatoid factor

Cytokines are important in the understanding of the immune process in health and disease and are valuable indicators in diagnostics. Measurements of cytokines are based on immunometric methods, and it is important to understand possible pitfalls in these methods to produce reliable cytokine data. This paper focuses on obtaining optimal measurements when applying enzyme-linked immunosorbent assay (ELISA) or multiplex immunoassays (MIA). Cytokines are measured in serum or plasma, as well as in various other body fluids, all containing a series of antibodies and the possibility of interference from these. Some antibodies, such as heterophilic and human anti-animal antibodies, are able to interfere with all immunoassays, but the immunometric techniques are most prone to serious interference from this source. Another type, rheumatoid factor (RF) is a composite of different autoimmune antibodies which can be present in both blood and synovial fluid. RF is present in some arthritic diseases as well as in some other medical conditions. When present, especially RF IgM is known to interfere with the immunometric measurements. A possible and affordable solution to diminish this interference is PEG precipitation, but other efficient, but more expensive, methods, such as precipitation using Protein L or commercially available blocking agents, are also available. Interference of RF is at present not tested in all cytokine assays, but degree of interference from RF, human anti-animal and heterophilic antibodies, as well as from other possible disease-specific antibodies, must always be considered when developing and applying new assays for cytokine measurements.

Nucleic Acid programmable protein arrays: versatile tools for array-based functional protein studies

Protein microarrays offer a global perspective on the function of expressed gene products. However, technical issues related to the stability and dynamic range of microarrays printed with purified protein have hampered their widespread adoption. Taking an alternate approach, the Nucleic Acid Programmable Protein Array (NAPPA) is constructed by spotting protein-encoding plasmid DNA at high density, in addressable fashion, on an array surface. Proteins are subsequently generated in situ just prior to experimentation using cell-free expression systems. As such, the NAPPA platform offers a unique and viable alternative that circumvents many of the inherent limitations of spotted protein arrays, enabling diverse functional protein studies including protein-small molecule, protein-protein, antigen-antibody, and protein-nucleic acid interactions. It further offers a versatile and adaptable platform amenable to a variety of capture modalities and expression systems, and, most importantly, construction of the array is accessible to any lab with an array printer and laser slide scanner. This unit is intended to provide a reference for investigators wishing to generate arrays based on this platform, and details (1) the basic construction of cDNA-based protein microarrays from DNA isolation to printing and development, (2) quality-control efforts taken to ensure the usefulness and integrity of microarray data, and (3) a particular example of the application of self-assembling protein arrays to screen for blood-borne antibody biomarkers.

Rheumatoid factor and its interference with cytokine measurements: problems and solutions

Use of cytokines as biomarkers for disease is getting more widespread. Cytokines are conveniently determined by immunoassay, but interference from present antibodies is known to cause problems. In rheumatoid arthritis (RA), interference of rheumatoid factor (RF) may be problematic. RF covers a group of autoantibodies from immunoglobulin subclasses and is present in 65–80% of RA patients. Partly removal of RF is possible by precipitation. This study aims at determining the effects of presence of RF in blood and synovial fluid on cytokine measurements in samples from RA patients and finding possible solutions for recognized problems. IL-1β, IL-4, IL-6, and IL-8 were determined with multiplex immunoassays (MIA) in samples from RA patients prior to and after polyethylene glycol (PEG 6000) precipitation. Presence of RF does interfere with MIA. PEG 6000 precipitation abolishes this RF interference. We recommend PEG precipitation for all immunoassay measurements of plasma samples from RA patients.

Expression of Mycobacterium leprae HSP65 in tobacco and its effectiveness as an oral treatment in adjuvant-induced arthritis

Transgenic plants are able to express molecules with antigenic properties. In recent years, this has led the pharmaceutical industry to use plants as alternative systems for the production of recombinant proteins. Plant-produced recombinant proteins can have important applications in therapeutics, such as in the treatment of rheumatoid arthritis (RA). In this study, the mycobacterial HSP65 protein expressed in tobacco plants was found to be effective as a treatment for adjuvant-induced arthritis (AIA). We cloned the hsp65 gene from Mycobacterium leprae into plasmid pCAMBIA 2301 under the control of the double 35S promoter from cauliflower mosaic virus. Agrobacterium tumefaciens bearing the pChsp65 plasmid was used to transform tobacco plants. Incorporation of the hsp65 gene was confirmed by PCR, reverse transcription-PCR, histochemistry, and western blot analyses in several transgenic lines of tobacco plants. Oral treatment of AIA rats with the HSP65 protein allowed them to recover body weight and joint inflammation was reduced. Our results suggest a synergistic effect between the HSP65 expressed protein and metabolites presents in tobacco plants.

Molecular signatures and new candidates to target the pathogenesis of rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic, inflammatory joint disease of unknown etiology and pronounced interpatient heterogeneity. To characterize RA at the molecular level and to uncover pathomechanisms, we performed genome-wide gene expression analysis. We identified a set of 1,054 genes significantly deregulated in pair-wise comparisons between RA and osteoarthritis (OA) patients, RA and normal donors (ND), or OA and ND. Correlation analysis revealed gene sets regulated identically in all three groups. As a prominent example secreted phosphoprotein 1 (SPP1) was identified to be significantly upregulated in RA compared with both OA and ND. SPP1 expression was found to correlate with genes expressed during an inflammatory response, T-cell activation and apoptosis, suggesting common underlying regulatory networks. A subclassification of RA patients was achieved on the basis of proteoglycan 4 (PRG4) expression, distinguishing PRG4 high and low expressors and reflecting the heterogeneity of the disease. In addition, we found that low PRG4 expression was associated with a more aggressive disease stage, which is in accordance with PRG4 loss-of-function mutations causing camptodactyly-arthropathy-coxa vara-pericarditis syndrome. Altogether we provide evidence for molecular signatures of RA and RA subclasses, sets of new candidate genes as well as for candidate gene networks, which extend our understanding of disease mechanisms and may lead to an improved diagnosis.

Exercise prevents the effects of experimental arthritis on the metabolism and function of immune cells

Active lymphocytes (LY) and macrophages (MPhi) are involved in the pathophysiology of rheumatoid arthritis (RA). Due to its anti-inflammatory effect, physical exercise may be beneficial in RA by acting on the immune system (IS). Thus, female Wistar rats with type II collagen-induced arthritis (CIA) were submitted to swimming training (6 weeks, 5 days/week, 60 min/day) and some biochemical and immune parameters, such as the metabolism of glucose and glutamine and function of LY and MPhi, were evaluated. In addition, plasma levels of some hormones and of interleukin-2 (IL-2) were also determined. Results demonstrate that CIA increased lymphocyte proliferation (1.9- and 1.7-fold, respectively, in response to concanavalin A (ConA) and lipopolysaccharide (LPS)), as well as macrophage H(2)O(2) production (1.6-fold), in comparison to control. Exercise training prevented the activation of immune cells, induced by CIA, and established a pattern of substrate utilization similar to that described as normal for these cells. Exercise also promoted an elevation of plasma levels of corticosterone (22.2%), progesterone (1.7-fold) and IL-2 (2.6-fold). Our data suggest that chronic exercise is able to counterbalance the effects of CIA on cells of the IS, reinforcing the proposal that the benefits of exercise may not be restricted to aerobic capacity and/or strength improvement.

Autoantibodies in rheumatoid arthritis: rheumatoid factors and anticitrullinated protein antibodies

Rheumatoid arthritis (RA) is a systemic inflammatory autoimmune disease, characterized by chronic, erosive polyarthritis and by the presence of various autoantibodies in serum and synovial fluid. Since rheumatoid factor (RF) was first described, a number of other autoantibodies have been discovered in RA patients. The autoantigens recognized by these autoantibodies include cartilage components, chaperones, enzymes, nuclear proteins and citrullinated proteins. However, the clinical significances and pathogenic roles of these antibodies are largely unknown except for RF and anticitrullinated protein antibodies (ACPAs), whose clinical usefulness has been acknowledged due to their acceptable sensitivities and specificities, and prognostic values. This review presents and discusses the current state of the art regarding RF and ACPA in RA.

Polymorphisms of COTL1 gene identified by proteomic approach and their association with autoimmune disorders

To select candidate genes, we attempted to comparative analysis of protein levels between rheumatoid arthritis (RA) patients and healthy controls by two-dimensional electrophoresis (2-DE) and matrix-assisted laser desorption ionization mass spectrometry (MALDI-TOF-MS). We identified 17 proteins that showed up- or down-regulated spots in RA patients. We found that coactosin-like1 (COTL1) were highly expressed in RA patients compared with healthy controls. We performed a case-control study to determine whether the COTL1 gene polymorphisms were associated with RA and systemic lupus erythematosus (SLE). The genotype frequency of c.-1124G>T and the allelic frequency of c.484G>A in RA patients, and the genotype frequency of c.484G>A in SLE patients were significantly different from healthy controls (P=0.009, 0.027, and 0.025, respectively). We also investigated the correlation with the levels of rheumatoid factor (RF) and anti-cyclic citrullinated peptide (CCP) antibody in RA patients, and anti-nuclear antibodies (ANA) in SLE patients. The c.484G>A polymorphism in RA patients has significant association with the levels of anti-CCP antibody (P=0.03). Our findings demonstrated that c.-1124G>T and c. 484G>A polymorphisms of the COTL1 gene might be associated with the genetic susceptibility of autoimmune disorders.

Autoantibodies to glucose‐6‐phosphate isomerase are elevated in the synovial fluid of rheumatoid arthritis patients

OBJECTIVE

This study investigated whether anti-glucose-6-phosphate isomerase (GPI) antibody in the synovial fluid is specifically related to human rheumatoid arthritis (RA).

METHODS

Synovial fluid was collected from patients with RA, osteoarthritis (OA), gout, Behcet's disease, or ankylosing spondylitis. GPI-binding activity was measured in the synovial fluid using a surface plasmon resonance (SPR) biosensor.

RESULTS

The mean level of anti-GPI signal in the synovial fluid of RA patients was significantly elevated compared with that of OA patients (2.84 +/- 1.41 AU versus 1.19 +/- 0.42 AU, respectively; p < 0.0001). Anti-GPI signals in the synovial fluids of patients with non-rheumatoid arthritis, such as gout, Behcet's disease, or ankylosing spondylitis were significantly lower than in the synovial fluid of RA patients (p < 0.005), and were similar to those of OA patients.

CONCLUSION

Our study indicates that anti-GPI antibody in the synovial fluid is specifically related to RA, and suggests that GPI and its autoantibody might be important in the pathogenesis of human RA.

Lactobacillus casei potentiates induction of oral tolerance in experimental arthritis

Probiotics have been shown to exert beneficial effects on modulation of diverse diseases. However, no information is available for the effect of probiotics in the induction of oral tolerance in autoimmune diseases. The main purpose of this study was to elucidate whether Lactobacillus casei (L. casei) affect the induction of oral tolerance in experimental rheumatoid arthritis (RA). Type II collagen (CII) alone or together with L. casei was orally administered into collagen-induced arthritis (CIA) rats, and its effects on the clinical and histopathological aspects of RA were investigated. Co-administration of L. casei with CII more effectively suppressed clinical symptoms, paw swelling, lymphocyte infiltration and destruction of cartilage tissues of experimental arthritis than the rats treated with CII alone. The enhanced therapeutic efficacy was associated with an increase in anti-inflammatory cytokines (IL-10 and TGF-beta) while decreasing pro-inflammatory cytokines (IL-1beta, IL-2, IL-6, IL-12, IL-17, IFN-gamma and TNF-alpha). Co-administration of L. casei with CII more effectively suppressed CII-reactive T cell proliferation and the levels of Th1-type IgG isotypes (IgG2a and IgG2b), while up-regulating Foxp3 expression levels and the population of Foxp3(+) CD4(+) T cells. Our study provides evidence that L. casei could potentiate antigen-specific oral tolerance and suppress Th1-type immune responses of arthritic inflammation.

B-cell involvement in the pathogenesis of RA-is there a contribution of the sympathetic nervous system?

The pathogenesis of rheumatoid arthritis (RA), the most common rheumatic disease, is still an unsolved puzzle. For many years, T-cells were the main focus of research, but recently, the B-cell drew more and more attention not least, due to the observation in humans that the anti-CD20 antibody Retuximab, which selectively depletes subsets of B-cells, lessens disease symptoms. A second novel approach to understand pathomechanisms that contribute to the development and progression of arthritis focuses on the sympathetic nervous system, which is known to moderate the function of immune cells, e.g., the B-cell, and therefore, is tied into a complex neuroimmune network that influences the course of the disease. This review first discusses current research that shows the significance of B-cells in the pathogenesis of RA. It then gives a short review of knowledge regarding the role of the sympathetic nervous system (1) in RA pathogenesis and (2) in modulating B-cell responses. Finally, the hypothesis is introduced that the sympathetic nervous system via modulating B-cell function, e.g., antibody production, influences the development and progression of RA.

Arthritis induced by posttranslationally modified (citrullinated) fibrinogen in DR4-IE transgenic mice

Rheumatoid arthritis (RA) is a common autoimmune disease that afflicts the synovium of diarthrodial joints. The pathogenic mechanisms inciting this disease are not fully characterized, but may involve the loss of tolerance to posttranslationally modified (citrullinated) antigens. We have demonstrated that this modification leads to a selective increase in antigenic peptide affinity for major histocompatibility complex (MHC) class II molecules that carry the RA-associated shared epitope, such as HLA-DRB1*0401 (DR4). We describe the induction of arthritis in DR4-IE transgenic (tg) mice with citrullinated fibrinogen, a protein commonly found in inflamed synovial tissue and a frequent target of autoantibodies in RA patients. The disease induced in these mice was characterized by synovial hyperplasia followed by ankylosis, but lacked a conspicuous polymorphonuclear cell infiltrate. Immunological analysis of these mice through T cell epitope scanning and antibody microarray analysis identified a unique profile of citrulline-specific reactivity that was not found in DR4-IE tg mice immunized with unmodified fibrinogen or in wild-type C57BL/6 mice immunized with citrullinated fibrinogen, two conditions where arthritis was not observed. These observations directly implicate citrullinated fibrinogen as arthritogenic in the context of RA-associated MHC class II molecules.

Découverte et structure cristallographique d’une apolipoprotéine humaine

We report the serendipitous discovery of a human plasma phosphate binding protein (HPBP). This 38 kDa protein is co-purified with paraoxonase (PON1). The association between HPON1 and HPBP is modulated by phosphate and calcium concentrations. The HPBP X-ray structure solved at 1.9 A resolution is similar to the prokaryotic phosphate solute-binding proteins (SBPs) associated with ATP binding cassette transmembrane transporters, though phosphate-SBPs have never been characterized or predicted from nucleic acid databases in eukaryotes. However, HPBP belongs to the family of ubiquitous eukaryotic proteins named DING, meaning that phosphate-SBPs are also widespread in eukaryotes. The absence of complete genes for eukaryotic phosphate-SBP from databases is intriguing, but the astonishing 90% sequence conservation of genes between evolutionary distant species suggests that the corresponding proteins play an important function. HPBP is the first identified transporter capable of binding phosphate ions in human plasma. Thus it is thought to become a new predictor and a potential therapeutic agent for phosphate-related diseases such as atherosclerosis.

Autoantibodies in rheumatoid arthritis: a review

Emerging insights into the importance of B cells in the pathogenesis of rheumatoid arthritis (RA) as highlighted by the efficacy of B cell depletion is one factor that has contributed to the upsurge of interest in the potential role of autoantibodies both as disease markers and with respect to a pathogenic role. Since the initial description of rheumatoid factor (RF), a large number of both disease-specific and non-specific autoantibodies have been described in patients with RA including antibodies to type II collagen (CII), immunoglobulin binding protein (BiP) and antibodies directed at citrullinated peptides (anti-CCP) and other citrullinated proteins such as vimentin (anti-Sa) . Despite some overlap the serological profile of RA does appear to be distinct from other diseases such as SLE . Although the precise mechanisms responsible for the formation of these antibodies have not been well defined their presence must reflect the interaction between T and B cells believed to be relevant to the pathogenesis of RA. The specificity of the association of such factors as anti-CCP and anti-BiP with RA may reflect unique pathogenic events leading to the processing and presentation of the "cryptic self" . Ease of measurement and stability make autoantibodies attractive diagnostic and prognostic markers particularly in early disease when it may be difficult to distinguish self-limiting synovitis from persistent disease . The purpose of this article is to provide an overview of the current state of knowledge of the spectrum of autoantibodies thus far characterised in individuals with rheumatoid arthritis, and discuss their diagnostic, prognostic and pathogenetic relevance.

Serendipitous discovery and X-ray structure of a human phosphate binding apolipoprotein

We report the serendipitous discovery of a human plasma phosphate binding protein (HPBP). This 38 kDa protein is copurified with the enzyme paraoxonase. Its X-ray structure is similar to the prokaryotic phosphate solute binding proteins (SBPs) associated with ATP binding cassette transmembrane transporters, though phosphate-SBPs have never been characterized or predicted from nucleic acid databases in eukaryotes. However, HPBP belongs to the family of ubiquitous eukaryotic proteins named DING, meaning that phosphate-SBPs are also widespread in eukaryotes. The systematic absence of complete genes for eukaryotic phosphate-SBP from databases is intriguing, but the astonishing 90% sequence conservation between genes belonging to evolutionary distant species suggests that the corresponding proteins play an important function. HPBP is the only known transporter capable of binding phosphate ions in human plasma and may become a new predictor of or a potential therapeutic agent for phosphate-related diseases such as atherosclerosis.

Limited VH gene usage in B-cell clones established with nurse-like cells from patients with rheumatoid arthritis

OBJECTIVES

Nurse-like stromal cells (NLC) in synovia and bone marrow of patients with rheumatoid arthritis (RA) can support pseudoemperipolesis, protect from apoptosis and enhance immunoglobulin production of peripheral blood B cells isolated from healthy individuals, suggesting the profound contribution of hyperactivation of B cells in RA. In the course of establishing RA-NLC from RA patients, we observed the growth of B cells in the presence of RA-NLC.

METHODS

We cloned B cells from the synovium or bone marrow of RA patients using the limiting dilution technique. For established clones, nucleotide sequences of immunoglobulin and surface antigens were investigated. To investigate the dependence of these clones on NLC, differences in the proliferation and the amount of immunoglobulin produced in the presence or absence of NLC were compared. Immunocytochemical staining of various cells was performed using the antibody these clones produced.

RESULTS

Nine B-cell clones established from RA patients showed RA-NLC-dependent growth. These B-cell clones expressed CD19, CD20, CD38, CD39 and CD40, suggesting that the cloned cells were mature and activated. All clones secreted immunoglobulins in culture media, which were specific for intracellular components of various cell lines, including RA-NLC. Interestingly, we found limited usage of immunoglobulin heavy-chain variable regions (VH) among B-cell clones from RA patients. These repertoires were reported to be detected preferentially in fetal livers.

CONCLUSION

The present study provides a novel insight into the involvement of RA-NLC in the immunopathogenesis of RA via an autoreactive B cell development and/or activation mechanism.

Sympathetic neurotransmitters in joint inflammation

This article demonstrates the dual pro- and anti-inflammatory role of the sympathetic nervous system (SNS) in inflammatory joint disease (IJD) by way of distinct adrenoceptors. The dual role of the SNS depends on involved compartments, timing of distinct effector mechanisms during the inflammatory process, availability of respective adrenoceptors on target cells, and an intricate shift from beta-to-alpha adrenergic signaling in the progressing course of the inflammatory disease (beta-to-alpha adrenergic shift). Additional critical points for the dual role of the SNS in inflammation are the underlying change of immune effector mechanisms during the process of disease progression and the behavior of sympathetic nerve fibers in inflamed tissue (nerve fiber loss). This is accompanied by a relative lack of anti-inflammatory glucocorticoids in relation to inflammation. In quintessence, in early stages of IJD, the SNS plays a predominantly proinflammatory role, whereas in late stages of the disease the SNS most probably exerts anti-inflammatory effects. Because patients who have rheumatoid arthritis most often present in the chronic phase of the disease, support of anti-inflammatory sympathetic pathways can be a promising therapeutic option.

Antiferritin antibodies discovered by phage display expression cloning are associated with radiographic damage in rheumatoid arthritis

OBJECTIVE

Several autoantibodies have been described in individuals with rheumatoid arthritis (RA), leading to interest in the use of such antibodies as diagnostic or prognostic markers in RA as well as in their relevance to disease pathology. The objective of this study was to use a phage display expression cloning system to identify novel autoantibody targets in RA.

METHODS

We used immunoscreening of a phage-displayed complementary DNA (cDNA) library to isolate a cDNA clone encoding the ferritin heavy chain polypeptide. Antiferritin antibody levels in patients with early and established RA, healthy controls, and disease controls were measured by enzyme-linked immunosorbent assay. Antibody-positive and antibody-negative individuals were compared with respect to disease severity as measured by the modified Larsen score, demographic variables, rheumatoid factor status, and carriage of HLA-DRB1 shared epitope alleles.

RESULTS

Antiferritin antibodies were present in 60 (16%) of 366 patients with established RA, 23 (19%) of 118 patients with early RA, 2 (2.7%) of 73 healthy blood donors, 2 (2.1%) of 94 individuals with osteoarthritis, and 2 (2.1%) of 97 patients with systemic lupus erythematosus (P < 0.01, RA patients versus healthy and disease controls). Antiferritin antibodies were more common in men than in women (28.4% versus 12.2%; P < 0.001), and antiferritin levels were associated with the severity of joint damage (P = 0.01).

CONCLUSION

Antiferritin antibodies are observed in a subset of patients with RA, are present early in the disease course, and are associated with the severity of radiographic damage. Further studies are required to explore their potential as diagnostic and prognostic markers in RA.

Association of autoantibodies to glucose-6-phosphate isomerase with extraarticular complications in rheumatoid arthritis

OBJECTIVE

In the K/BxN mouse model, autoantibodies against glucose-6-phosphate isomerase (GPI) cause arthritis. The relevance of this model for human disease remains a subject of controversy. We set out to determine whether GPI autoantibodies occur in patients with rheumatoid arthritis (RA) and, if so, at what stage of the RA.

METHODS

Using an enzyme-linked immunosorbent assay, serum from 131 RA patients and 28 healthy controls was tested for autoantibodies against recombinant human GPI. Patients were grouped according to disease duration and presence of rheumatoid nodules, rheumatoid vasculitis, and Felty's syndrome, which are extraarticular complications of RA.

RESULTS

Elevated levels of autoantibodies against GPI were present in 5% of patients with uncomplicated RA and 4% of controls. In RA complicated by extraarticular manifestations, anti-GPI antibodies were observed in 18% of patients with rheumatoid nodules, 45% of patients with rheumatoid vasculitis, and 92% of patients with Felty's syndrome.

CONCLUSION

In patients with RA, autoantibodies to GPI are associated with the occurrence of extraarticular complications.

Integrated evolutionary, immunological, and neuroendocrine framework for the pathogenesis of chronic disabling inflammatory diseases

The pathogenesis of chronic disabling inflammatory diseases (CDIDs) is poorly understood. Current concepts that focus on abnormalities of the immune system are, in our view, incomplete. Here we propose that chronic disruption of homeostasis through abnormal neuronal and endocrine host responses to transient inflammatory reactions contributes to the appearance of CDIDs. Coordinated reactions of the supersystems (immune, nervous, endocrine, and reproductive) that maintain homeostasis have been evolutionarily conserved to respond to and eliminate foreign agents over a period of days to a few weeks. If the responses of these supersystems fail to return to normal after elimination of the pathogen, a continuous aggressive immune response is created; this situation can trigger development of CDIDs. Maladaptation of the supersystems during CDIDs has not been evolutionarily conserved but is nevertheless still prevalent because a large proportion of these diseases tend to appear after the reproductive phase. We propose that this integrated systems hypothesis may permit better identification of a patient at risk or in the early stages of developing a CDID such as rheumatoid arthritis and enable more coordinated intervention than is presently attempted.

The use and abuse of commercial kits used to detect autoantibodies

The detection of autoantibodies in human sera is an important approach to the diagnosis and management of patients with autoimmune conditions. To meet market demands, manufacturers have developed a wide variety of easy to use and cost-effective diagnostic kits that are designed to detect a variety of human serum autoantibodies. A number of studies over the past two decades have suggested that there are limitations and concerns in the use and clinical application of test results derived from commercial kits. It is important to appreciate that there is a complex chain of users and circumstances that contributes to variations in the apparent reliability of commercial kits. The goal of this review is to identify the principal links in this chain, to identify the factors that weaken the chain and to propose a plan of resolution. It is suggested that a higher level of commitment and partnership between all of the participants is required to achieve the goal of improving the quality of patient care through the use of autoantibody testing and analysis.

The role of B cells in rheumatoid arthritis: mechanisms and therapeutic targets

Our understanding of the role of B cells as part of the immune system has been remarkably expanded in the past few years. Autoimmunity, the production of autoantibodies or the activation and expansion of autoimmune T cells, is relatively common, whereas the development of autoimmune diseases with destruction of tissue is much less frequent. In rheumatoid arthritis, the autoantigen(s) involved in tissue damage and their role in disease have not been fully elucidated. Recent data suggest that the impact of B cells in rheumatoid arthritis may be of significance; therefore, a depleting anti-B cell therapy appears to be another therapeutic strategy. This review will focus on recent findings of the role of B cells in rheumatoid arthritis and the implications to target B cells in this disease.

Clonal analysis of B cells in the synovial membrane of patients with rheumatoid arthritis

OBJECTIVE

To investigate the clonal characteristics of B cells in the synovial membranes of rheumatoid arthritis (RA) patients.

METHODS

The clonality of B cells at separate sites of the synovial membrane and other tissues from RA patients were investigated by a reverse transcriptase-polymerase chain reaction with a VH framework 3 consensus primer and a subsequent single-strand conformation polymorphism analysis.

RESULTS

Several dominant bands were observed in all synovial membrane samples and some of the dominants bands were common among the 2 or 3 separate regions of each synovial sample. The persistent existence of clonal B cells was observed in metachronous synovial fluid samples.

CONCLUSION

Infiltrating B cells are oligoclonal and antigen-driven mechanisms may play a role in the generation of clonal B cells in RA synovium. The stable presence of B cell clones in synovial fluid suggests the involvement of these clones in the perpetuation of the chronic inflammation in RA.

Detection of antibodies to deiminated recombinant rat filaggrin by enzyme-linked immunosorbent assay: a highly effective test for the diagnosis of rheumatoid arthritis

OBJECTIVE

To assay antifilaggrin autoantibodies, we developed an enzyme-linked immunosorbent assay (ELISA) using a "citrullinated" recombinant rat filaggrin. Our objectives were to assess its value for diagnosing rheumatoid arthritis (RA) and to compare the results with those obtained using 4 other reference methods for detection of antifilaggrin autoantibodies, including the commercially available ELISA that uses a modified "citrullinated" synthetic peptide derived from the sequence of human filaggrin (CCP-ELISA).

METHODS

We analyzed 711 sera from patients with well-characterized rheumatic diseases, including 240 patients with RA. Antifilaggrin autoantibodies were detected by an ELISA using a recombinant rat filaggrin deiminated in vitro as immunosorbent (ArFA-ELISA). The results considered were the differences between the optical densities obtained on deiminated and nondeiminated proteins. Antibodies to rat esophagus epithelium were detected by indirect immunofluorescence, while antibodies to human filaggrin were detected by immunoblotting and by a recently described ELISA using a deiminated recombinant human filaggrin. Finally, CCP-ELISA was performed according to the manufacturer's recommendations.

RESULTS

At the titer thresholds allowing diagnostic specificities of 0.95, 0.985, and 0.99 to be reached, the diagnostic sensitivities of the ArFA-ELISA were 0.76, 0.67, and 0.65, respectively. At these 3 thresholds, the sensitivities were significantly higher than those of the 4 other tests. Despite incomplete overlapping of the 5 tests, the high diagnostic performance of the ArFA-ELISA allows us to propose this test to replace all the other methods for antifilaggrin autoantibody detection.

CONCLUSION

ArFA-ELISA appears to be the most efficient test among those available for the detection of antifilaggrin autoantibodies, in terms of diagnostic accuracy for RA. Its diagnostic performance in early RA and its prognostic value are currently under evaluation.

Rheumatoid factors: host resistance or autoimmunity?

Rheumatoid factors (RFs), autoantibodies that bind to the Fc portion of IgG, are important in the immune response. RF-committed B-cells exist in the circulating lymphocyte pool in a high frequency (approximately 1-2 %) in normal individuals and in patients with pathological conditions associated with the sustained levels of circulating RF, such as rheumatoid arthritis (RA), Sjogren's syndrome (SS), and mixed cryoglobulinemia, associated with hepatitis C virus infection. RFs are induced by many infectious entities (viruses, bacteria, parasites) as a consequence of a secondary immune response to the pathogen, but usually the response is transient. It is likely that RFs play an important role in the host's defense against infection, both at the cellular level, where the RF B-cell can be an antigen presenting cell which can promote the antipathogen response, and at the humoral level, where RFs can contribute to the mopping up of the IgG antipathogen antibodies by contributing to immune complex formation and clearance. There has been much research on RFs in chronic pathological conditions, and the literature pertaining to their origin, structure, binding specificities, and possible roles in disease are discussed. The importance of the host defense, sometimes at the expense of an autoimmune response, is a balance that needs to be considered in light of a possible outcome of health or disease.

Presence of autoantibodies to the glycolytic enzyme alpha-enolase in sera from patients with early rheumatoid arthritis

OBJECTIVE

To identify a new autoantigen/autoantibody population in rheumatoid arthritis (RA) sera.

METHODS

Following a population-based recruitment effort, 255 patients with very early arthritis (median disease duration 4 months) were studied using different clinical, biologic, and radiologic assessments. After a followup period of 1 year, patients were classified as having RA (n = 145), non-RA rheumatic diseases (n = 70), and undifferentiated arthritis (n = 40). Patients' sera were analyzed by one-dimensional (1D) and 2D Western blotting. The recognized 50-kd protein was analyzed by matrix-assisted laser desorption ionization-time-of-flight (MALDI-TOF) mass spectrometry (MS). RA serum reactivities were evaluated against the recombinant protein synthesized by an in vitro coupled transcription-translation system.

RESULTS

On 1D Western blots, 36 of the 145 RA sera bound to a 50-kd polypeptide. On 2D Western blots, anti-50-kd+ RA sera recognized a triplet of isoelectric point 6.5-7.0 and a molecular mass of 50 kd. The 3 spots of the triplet were analyzed by MALDI-TOF MS and were shown to correspond to human alpha-enolase. A goat anti-enolase antiserum, which recognized a band comigrating with the 50-kd antigen on 1D Western blots, gave a labeling pattern on 2D Western blots similar to that observed with anti-50-kd+ RA sera. Among the 36 RA sera that identified alpha-enolase in protein maps, only 8 recognized the recombinant (unmodified) alpha-enolase. The specificity of anti-alpha -enolase antibodies for RA was 97.1%. Half of the anti-alpha -enolase-positive RA patients were negative for both rheumatoid factor and antifilaggrin antibodies. The presence of anti-alpha-enolase antibodies was the greatest predictive factor of radiologic progression in the first 66 RA patients included.

CONCLUSION

Autoantibodies to alpha-enolase, an enzyme of the glycolytic pathway, are present in the sera of patients with very early RA and have potential diagnostic and prognostic value for RA.

Value of laboratory tests in early prediction of rheumatoid arthritis

OBJECTIVE

To determine which laboratory test or tests at presentation best predicted a diagnosis of rheumatoid arthritis (RA) 2 years later.

METHODS

Two hundred seventy patients with early arthritis seen in 7 hospitals underwent comprehensive evaluations at 6-month intervals for 2 years, when the diagnosis of RA was assessed by 5 rheumatologists. The sensitivity and specificity of each test at the first visit for discriminating between RA (38%, n = 98) and non-RA patients were determined. Optimal cutoffs for continuous tests were derived from receiver operating characteristic curves. Sensitivity and specificity of test combinations selected by multiple logistic regression were determined.

RESULTS

IgM rheumatoid factor (RF) by enzyme-linked immunosorbent assay, IgG-antikeratin antibody (AKA), and latex test had the strongest associations with RA. These 3 tests formed the most powerful combination for distinguishing RA from non-RA.

CONCLUSION

IgM-RF, IgG-AKA, and the latex test are the best laboratory tests for discriminating between patients with and without RA. Combining these tests slightly improves diagnostic value.

The pathogenesis of rheumatoid arthritis: a guide to therapy

The cause of rheumatoid arthritis (RA) is unknown; however, extensive research has yielded great insight into its pathogenesis. Lymphocytes play a significant role, but a lesser role in the perpetuation of late disease. The rheumatoid synovium is composed primarily of fibroblasts and monocytes that produce inflammatory cytokines, of which interleukin-1 and tumor necrosis factor are of key importance. Potential regulatory mechanisms balancing the effects of these cytokines are inadequate to prevent joint damage and subsequent disability. These cytokines seem responsible for stimulating destructive processes in the joint via induction of prostaglandins, angiogenesis, chemokines, adhesion molecules, osteoclastogenesis, and matrix metalloproteinases. This review discusses recent research findings in the immunopathogenesis of RA with respect to potential targets for therapy.

High in vivo expression of interleukin-17 receptor in synovial endothelial cells and chondrocytes from arthritis patients

OBJECTIVE

To evaluate the presence of interleukin-17 (IL-17) and the expression of IL-17 receptor (IL-17R) in joint tissues from subjects with different arthritides.

METHODS

Immunohistochemistry was used on frozen synovial and cartilage biopsies to identify cells expressing IL-17 and IL-17R.

RESULTS

IL-17 staining was present only in synovial biopsies of rheumatoid arthritis (RA) (seven out of nine cases). IL-17R was expressed by all synovial biopsies evaluated except for three cases of post-traumatic arthritis (PTA). Vascular endothelial cells mainly expressed IL-17R. The percentage of IL-17R(+) vessels was the highest in RA synovium and the lowest in PTA. Chondrocytes from all types of arthritides were negative for IL-17 staining, but expressed IL-17R; the highest percentage of positive chondrocytes was found in seronegative spondylarthritis and the lowest in RA.

CONCLUSIONS

IL-17-positive cells are found exclusively in RA. On the other hand, synovial endothelial cells and chondrocytes expressing IL-17R are found in the majority of patients with different types of arthritis. This finding suggests a role for a second ligand for IL-17R, which could be either a different cytokine or a different isoform of IL-17.

Pathogenesis of rheumatoid arthritis. The role of T cells and other beasts

The evidence coming from the different experimental approaches reviewed in this article strongly supports the hypothesis that RA is T-cell driven at all stages of the disease. Although the effector phases responsible for the events that lead to joint destruction involve several different cell types, cytokines, and other mediators, T cells still direct operations behind the scenes. Direct experimental proof of this proposition in patients is still lacking, but the development of nondepleting modulating CD4 monoclonal antibodies may provide new tools to test this hypothesis. In this respect, it is encouraging that using one such reagent, we have recently shown that not only did the activity of the disease improve but, more importantly, the inflammatory indices and production of non-T-cell cytokines were reduced. This is not to dissimilar from the results of experiments described in animals, where by blocking synovial T cells, the production of IL-1 beta and TNF alpha could be decreased by more than 90%. From this perspective, it may be predicted that by modulating T cells in the joint, it is possible to achieve our ultimate goal of permanently switching off the disease.