Anti-A2/RA33 autoantibodies are directed to the RNA binding region of the A2 protein of the heterogeneous nuclear ribonucleoprotein complex. Differential epitope recognition in rheumatoid arthritis, systemic lupus erythematosus, and mixed connective tissue disease

Undervalued and novel roles of heterogeneous nuclear ribonucleoproteins in autoimmune diseases: Resurgence as potential biomarkers and targets

Autoimmune diseases are mainly characterized by the abnormal autoreactivity due to the loss of tolerance to specific autoantigens, though multiple pathways associated with the homeostasis of immune responses are involved in initiating or aggravating the conditions. The heterogeneous nuclear ribonucleoproteins (hnRNPs) are a major category of RNA-binding proteins ubiquitously expressed in a multitude of cells and have attracted great attentions especially with their distinctive roles in nucleic acid metabolisms and the pathogenesis in diseases like neurodegenerative disorders and cancers. Nevertheless, the interplay between hnRNPs and autoimmune disorders has not been fully elucidated. Virtually various family members of hnRNPs are increasingly identified as immune players and are pertinent to all kinds of immune-related processes including immune system development and innate or adaptive immune responses. Specifically, hnRNPs have been extensively recognized as autoantigens within and even beyond a myriad of autoimmune diseases, yet their diagnostic and prognostic values are seemingly underestimated. Molecular mimicry, epitope spreading and bystander activation may represent major putative mechanisms underlying the presence of autoantibodies to hnRNPs. Besides, hnRNPs play critical parts in regulating linchpin genes expressions that control genetic susceptibility, disease-linked functional pathways, or immune responses by interacting with other components particularly like microRNAs and long non-coding RNAs, thereby contributing to inflammation and autoimmunity as well as specific disease phenotypes. Therefore, comprehensive unraveling of the roles of hnRNPs is conducive to establishing potential biomarkers and developing better intervention strategies by targeting these hnRNPs in the corresponding disorders. This article is categorized under: RNA in Disease and Development > RNA in Disease RNA Interactions with Proteins and Other Molecules > Protein-RNA Interactions: Functional Implications.

The XIST lncRNA is a sex-specific reservoir of TLR7 ligands in SLE

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease with a dramatic sex bias, affecting 9 times more women than men. Activation of Toll-like receptor 7 (TLR7) by self-RNA is a central pathogenic process leading to aberrant production of type I interferon (IFN) in SLE, but the specific RNA molecules that serve as TLR7 ligands have not been defined. By leveraging gene expression data and the known sequence specificity of TLR7, we identified the female-specific X-inactive specific transcript (XIST) long noncoding RNA as a uniquely rich source of TLR7 ligands in SLE. XIST RNA stimulated IFN-α production by plasmacytoid DCs in a TLR7-dependent manner, and deletion of XIST diminished the ability of whole cellular RNA to activate TLR7. XIST levels were elevated in blood leukocytes from women with SLE compared with controls, correlated positively with disease activity and the IFN signature, and were enriched in extracellular vesicles released from dying cells in vitro. Importantly, XIST was not IFN inducible, suggesting that XIST is a driver, rather than a consequence, of IFN in SLE. Overall, our work elucidated a role for XIST RNA as a female sex-specific danger signal underlying the sex bias in SLE.

Clinical significance of anti-rheumatoid arthritis 33 antibody in patients with systemic lupus erythematosus

Although anti-rheumatoid arthritis (RA) 33 antibodies have been reported to be present in various connective tissue diseases (CTDs), the clinical significance of anti-RA33 in CTDs is still obscure. This study was performed to explore the clinical significance of anti-RA33 in CTDs, especially systemic lupus erythematosus (SLE). A total of 565 patients with positive anti-nuclear antibodies who had been tested for anti-RA33 were included in this study and were further classified into RA33-positive and RA33-negative groups. The association between anti-RA33 and the clinical features of CTDs was examined. Receiver operating characteristic (ROC) analysis was performed to explore the diagnostic value of anti-RA33 in SLE and SLE-related organ involvement. The results showed that SLE was the most common disease in CTD patients positive for anti-RA33 (48.8%). Compared with the RA33-negative group, higher proportions of SLE-associated antibodies and SLE patients with a high disease activity as well as lower levels of serum complement components were observed in the RA33-positive group (all p < 0.05). Furthermore, CTD patients with positive anti-RA33 were more likely to suffer from mucocutaneous and hematological involvement as well as interstitial lung disease (all p < 0.05). ROC analysis revealed an area under the curve value of 0.634 (95% confidence interval: 0.587-0.681) for anti-RA33 in the diagnosis of SLE, with a specificity and sensitivity of 92.9% and 13.5%, respectively. Taken together, this study reveals a significant association between anti-RA33 and the clinical features of CTDs, especially SLE, indicating a potential clinical significance of anti-RA33 in the management of SLE.

The citrullinated/native index of autoantibodies against hnRNP-DL predicts an individual "window of treatment success" in RA patients

BACKGROUND

There is a need for biomarker to identify patients "at risk" for rheumatoid arthritis (risk-RA) and to better predict the therapeutic response and in this study we tested the hypothesis that novel native and citrullinated heterogeneous nuclear ribonucleoprotein (hnRNP)-DL autoantibodies could be possible biomarkers.

METHODS

Using protein macroarray and ELISA, epitope recognition against hnRNP-DL was analysed in sera from different developed RA disease and diagnosed SLE patients. Toll-like receptor (TLR) 7/9 and myeloid differentiation primary response gene 88 (MyD88)-dependency were studied in sera from murine disease models. HnRNP-DL expression in cultivated cells and synovial tissue was analysed by indirect immunofluorescence, immunoblot and immunohistochemistry.

RESULTS

HnRNP-DL was highly expressed in stress granules, citrullinated in the rheumatoid joint and targeted by autoantibodies either as native or citrullinated proteins in patient subsets with different developed RA disease. Structural citrullination dependent epitopes (SCEs) of hnRNP-DL were detected in 58% of the SLE patients although 98% of these sera were α-CCP-2-negative. To obtain a specific citrullinated signal value, we subtracted the native antibody value from the citrullinated signal. The citrullinated/native index of autoantibodies against hnRNP-DL (CNDL-Index) was identified as a new value for an "individual window of treatment success" in early RA and for the detection of RF IgM/α-CCP-2 seronegative RA patients (24-46%). Negative CNDL-index was found in SLE patients, risk-RA and early RA cohorts such as EIRA where the majority of these patients are DAS28-responders to methotrexate (MTX) treatment (87%). High positive CNDL-values were associated with more severe RA, shared epitope and parenchymal changes in the lung. Specifically, native α-hnRNP-DL is TLR7/9-dependent, associated with pain and ROC analysis revealed an association to initial MTX or etanercept treatment response, especially in seronegative RA patients.

CONCLUSION

CNDL-index defines people at risk to develop RA and the "window of treatment success" thereby closing the sensitivity gap in RA.

Insights into the treatment of rheumatoid arthritis: A paradigm in medicine

Insights into rheumatoid arthritis (RA) have slowly evolved over the last century, but with breathtaking speed over the last 2 decades. While only aspirin and parenteral gold were available in early 20th century, the efficacy of sulfasalazine, glucocorticoids and methotrexate was established around its middle. Identification of pathogenetic pathways was slow, and until today the role of T-cells is enigmatic, while it is clear that genetics via the shared epitope and other genes as well as environmental factors including the metagenome play major roles. More clarity evolved on importance of proinflammatory cytokines, especially TNF and IL-6. The activation of osteoclasts, the culprits of bony joint damage, is amplified by the proinflammatory cytokines. The realization of TNF's central role led to the successful introduction of TNF-inhibitors and subsequently also inhibitors of other cytokines and cells as well as signal transduction. In parallel, the evolution of outcomes research has contributed importantly to RA management. At the turn to the 21st century, improvement criteria and continuous indices were created, allowing reliable therapeutic response determination, including definition of endpoints like remission. Also our understanding of the role of disease activity relative to disease pathology has increased, ultimately fostering the treat-to-target concept and recommendations and, thus, optimal outcomes for RA patients as never been seen before. Similar developments are now ultimately being introduced in the field of psoriatic arthritis. Here many of these aspects are reviewed from a very personal perspective of the author in the hopes of further helping parients with chronic forms of arthritis.

Cellular and molecular perspectives in rheumatoid arthritis

Synovial immunopathology in rheumatoid arthritis is complex involving both resident and infiltrating cells. The synovial tissue undergoes significant neovascularization, facilitating an influx of lymphocytes and monocytes that transform a typically acellular loose areolar membrane into an invasive tumour-like pannus. The microvasculature proliferates to form straight regularly-branching vessels; however, they are highly dysfunctional resulting in reduced oxygen supply and a hypoxic microenvironment. Autoantibodies such as rheumatoid factor and anti-citrullinated protein antibodies are found at an early stage, often before arthritis has developed, and they have been implicated in the pathogenesis of RA. Abnormal cellular metabolism and mitochondrial dysfunction thus ensue and, in turn, through the increased production of reactive oxygen species actively induce inflammation. Key pro-inflammatory cytokines, chemokines and growth factors and their signalling pathways, including nuclear factor κB, Janus kinase-signal transducer, are highly activated when immune cells are exposed to hypoxia in the inflamed rheumatoid joint show adaptive survival reactions by activating. This review attempts to highlight those aberrations in the innate and adaptive immune systems including the role of genetic and environmental factors, autoantibodies, cellular alterations, signalling pathways and metabolism that are implicated in the pathogenesis of RA and may therefore provide an opportunity for therapeutic intervention.

Immunodiagnostic significance of anti-RA33 autoantibodies in Saudi patients with rheumatoid arthritis

The primary objective of this study was to evaluate and compare the immunodiagnostic significance and utility of anti-RA33 with anti-CCP, RF, and CRP in Saudi patients with rheumatoid arthritis. Methods. This was a prospective controlled clinical study conducted at King Abdul Aziz University Tertiary Medical Centre. The sera of 41 RA patients, 31 non-RA patients, and 29 healthy controls were collected. Anti-RA33 and anti-CCP were measured using commercially available ELISA principle kits. RF and CRP were measured using nephelometry. Results. Anti-RA33 antibodies had the lowest positive and negative predictive values and showed a sensitivity of 7.32% with 95.12% specificity. Of the other three markers (including anti-CCP antibodies, CRP, and RF), only anti-CCP showed specificity of 90.46% with sensitivity of 63.41% compared to non-RA patients + healthy control. There was a significant correlation with rheumatoid factor positivity with anti-CCP. With respect to CRP, a notable correlation was seen only with anti-RA33. Conclusion. Compared to rheumatoid factor, anti-CCP antibodies, and C-reactive proteins, the anti-RA33 autoantibodies seem to be not representing as an important additional immunodiagnostic marker in Saudi patients with established RA. RA33 may have more interest in early RA or less severe RA and other systemic connective tissue disorders.

The KDM2B- let-7b -EZH2 axis in myelodysplastic syndromes as a target for combined epigenetic therapy

Both DNA and histone methylation are dysregulated in the myelodysplastic syndromes (MDS). Based on preliminary data we hypothesized that dysregulated interactions of KDM2B, let-7b and EZH2 signals lead to an aberrant epigenetic landscape. Gene expression in CD34+ cells from MDS marrows was analyzed by NanoString miR array and validated by real-time polymerase chain reaction (PCR). The functions of KDM2B, let-7b and EZH2 were characterized in myeloid cell lines and in primary MDS cells. Let-7b levels were significantly higher, and KDM2B and EZH2 expression was lower in primary CD34+ MDS marrow cells (n = 44) than in healthy controls (n = 21; p<0.013, and p<0.0001, respectively). Overexpression of let-7b reduced EZH2 and KDM2B protein levels, and decreased cells in S-phase while increasing G0/G1 cells (p = 0.0005), accompanied by decreased H3K27me3 and cyclin D1. Silencing of KDM2B increased let-7b expression. Treatment with the cyclopentanyl analog of 3-deazaadenosine, DZNep, combined with the DNA hypomethylating agent 5-azacitidine, decreased levels of EZH2, suppressed methylation of di- and tri-methylated H3K27, and increased p16 expression, associated with cell proliferation. Thus, KDM2B, via let-7b/EZH2, promotes transcriptional repression. DZNep bypassed the inhibitory KDM2B/let-7b/EZH2 axis by preventing H3K27 methylation and reducing cell proliferation. DZNep might be able to enhance the therapeutic effects of DNA hypomethylating agents such as 5-azacitidine, currently considered standard therapy for patients with MDS.

Lungs, joints and immunity against citrullinated proteins in rheumatoid arthritis

Rheumatoid arthritis (RA) is a prototype for a criterion-defined inflammatory disease, for which the aetiology and initial molecular pathogenesis has been elusive for a long time. We describe in this Review how studies on the interplay between specific immunity, alongside genetic and environmental predisposing factors, provide new tools to understand the molecular basis of distinct subsets of the disease. A particular emphasis is on the possibility that pathogenic immune reactions might be initiated at other sites than the joints, and that the lungs could harbour such sites. New data strengthen this concept, showing that local immunity towards citrullinated proteins and accompanying inflammation might be present in the lungs early during disease development. This progress makes RA an interesting case for the future development of therapies that might be directed against disease-inducing immunity even before inflammation and destruction of joints has begun.

A study of erosive phenotypes in lupus arthritis using magnetic resonance imaging and anti-citrullinated protein antibody, anti-RA33 and RF autoantibody status

OBJECTIVES

The aims of this study were to investigate the extent of MRI-determined joint disease (erosion and synovitis) in SLE and to link this to autoantibody profiles known to be relevant to SLE, including ACPA, RF and anti-RA33 antibodies.

METHODS

Contrast-enhanced MRI of the hand and wrist was performed in 34 symptomatic SLE patients and in 15 RA patients with similar disease duration. Images were scored by two observers using the OMERACT rheumatoid arthritis MRI scoring (RAMRIS) system. Findings were correlated with clinical examination and autoantibody status.

RESULTS

Erosions were present at the wrist in 93% of SLE patients and at the MCP joints in 61% of SLE patients. Despite the high prevalence of MRI-determined erosion, only 8.8% of SLE patients were ACPA positive, although these patients had a higher burden of erosive disease. There was no positive correlation with anti-RA33 titres and erosion scores in the SLE patients, but there was a negative correlation with anti-RA33 titres and total bone oedema scores in the SLE patients. Ninety-three per cent of SLE patients had at least grade 1 synovitis at one or more MCP joints, and wrist joint synovitis was present in all the SLE patients.

CONCLUSION

An MRI-determined joint erosive phenotype is common in SLE, even in ACPA-negative cases. The conventional radiographic observation that anti-RA33 is not positively associated with erosion in patients with RA was also found to be the case in SLE patients.

Anti-hnRNP B1 (RA33) autoantibodies are associated with the clinical phenotype in Russian patients with rheumatoid arthritis and systemic sclerosis

Heterogeneous nuclear ribonucleoproteins (hnRNPs) are potent autoantigenic targets in systemic autoimmune rheumatic diseases (SARD). Loss of tolerance to the RA33 complex consisting of hnRNP A2 and its alternatively spliced variants B1 and B2 has been the interest of rheumatologists. A novel ELISA for the detection of anti-hnRNP B1 autoantibodies has been developed to investigate the prevalence thereof in 397 patients with SARD, including patients with rheumatoid arthritis (RA), spondyloarthropathy (SPA), juvenile chronic arthritis, systemic lupus erythematosus (SLE), systemic sclerosis (SSc), and Sjögren's syndrome (SS), in comparison to 174 controls. Anti-hnRNP B1 autoantibodies were significantly more prevalent in patients with SARD than controls (47/397, 11.8% versus 2/174, 1.1%; P < 0.001). In particular, anti-hnRNP B1 were found more frequently in the disease cohorts than in the controls and were present in 24/165 (14.5%) patients with RA, 6/58 (10.3%) SPA, 11/65 (16.9%) SSc, and 4/50 (8.0%) SLE. In RA patients, anti-hnRNP B1 autoantibodies correlated significantly with C-reactive protein levels and erythrocyte sedimentation rate, while in patients with SSc it was associated with features of arterial wall stiffness and presence of hypertension. Anti-hnRNP B1 autoantibodies occur in SARD and seem to be correlated with distinct clinical characteristics in patients with RA and SSc.

SPRi-based strategy to identify specific biomarkers in systemic lupus erythematosus, rheumatoid arthritis and autoimmune hepatitis

Background

Heterogeneous nuclear ribonucleoprotein (hnRNP) A2/B1 is a target for antinuclear autoantibodies in systemic Lupus erythematosus (SLE), rheumatoid arthritis (RA), and autoimmune hepatitis (AIH).

Aim

To monitor molecular interactions between peptides spanning the entire sequence of hnRNP A2/B1 and sera from patients and healthy controls.

Methods

Sera from 8 patients from each pathology and controls were passed across a surface plasmon resonance Imagery (SPRi) surface containing 39 overlapping peptides of 17 mers covering the human hnRNP B1. Interactions involving the immobilised peptides were followed in real time and dissociation rate constants k_off for each interaction were calculated.

Results

Several significant interactions were observed: i) high stability (lower k_off values) between P_55-70 and the AIH sera compared to controls (p= 0.003); ii) lower stability (higher k_off values) between P_118-133 and P_262-277 and SLE sera, P_145-160 and RA sera compared to controls (p=0.006, p=0.002, p=0.007). The binding curves and k_off values observed after the formation of complexes with anti-IgM and anti-IgG antibodies and after nuclease treatment of the serum indicate that i) IgM isotypes are prevalent and ii) nucleic acids participate in the interaction between anti-hnRNAP B1 and P_55-70 and also between controls and the peptides studied.

Conclusions

These results indicate that P_55-70 of hnRNP B1 is a potential biomarker for AIH in immunological tests and suggest the role of circulating nucleic acids, (eg miRNA), present or absent according to the autoimmune disorders and involved in antigen-antibody stability.

Emerging cell and cytokine targets in rheumatoid arthritis

Despite major progress in the treatment of rheumatoid arthritis (RA), strong unmet medical need remains, as only a minor proportion of patients reach sustained clinical remission. New approaches are therefore necessary, and include manipulation of regulatory T cells, which might be able to restore the disturbed immune system and could even lead to a cure if this restored regulation were to prove sustainable. Logistical and conceptual problems, however, beset this attractive therapeutic approach, including difficulties with ex vivo expansion of cells, specificity of targeting and the optimal time point of administration. Therefore, alternative avenues are being investigated, such as targeting B-cell effector functions and newly identified proinflammatory cytokines. On the basis of success with B-cell depleting therapy using anti-CD20 agents, further treatment modalities are now exploring direct or indirect interference in B-cell-mediated immunity with the use of agents directed against other B-cell surface molecules. Novel approaches target intracellular B-cell signalling and regulatory B cells. New cytokine-directed therapies target important proinflammatory mediators such as GM-CSF, new members of the IL-1 family, IL-6 and its receptor, IL-17, IL-20, IL-21, IL-23 as well as synovium-specific targets. This article reviews these emerging cell and cytokine targets with special focus on biologic agents, some of which might reach the clinic soon whereas others will require considerable time in development. Nevertheless, these exciting new approaches will considerably enhance our repertoire in the battle against this potentially devastating disease.

Nucleic acid-stimulated antigen-presenting cells trigger T cells to induce disease in a rat transfer model of inflammatory arthritis

Autoimmune responses to heterogeneous nuclear ribonucleproteins (hnRNP) occur in many systemic autoimmune diseases, particularly in patients with rheumatoid arthritis (RA) and systemic lupus erythematosus. In RA, humoral and/or cellular autoimmunity to hnRNP-A2/B1 is the most prominent anti-nuclear reactivity, being detectable in more than 50% of patients. However, its pathogenic role has not been fully elucidated yet. Here, we report that splenocytes from rats with pristane-induced arthritis transfer disease after in vitro restimulation with hnRNP-A/B antigens. Remarkably, disease transfer can be blocked by nuclease treatment of hnRNPs and is also achieved with splenocytes stimulated with hnRNP-A/B associated DNA or RNA oligonucleotides (ON) alone. Induction of proinflammatory cytokines in splenocytes stimulated with hnRNP-A/Bs or ONs involves Toll-like receptors (TLR) 7 and 9 but not TLR3. Furthermore, although T cells are the main mediators of disease transfer they require restimulation with TLR-activated antigen-presenting cells such as macrophages in order to become arthritogenic. Thus, the autoantigenic properties of hnRNPs appear to be mediated by their associated nucleic acids binding to TLR7 and 9. Our data explain the specific selection of hnRNP-A2/B1 as autoantigen in RA and reveal the requirement of interaction between innate and adaptive immunity to initiate and drive inflammation in autoimmune arthritis.

Immunodominant T-cell epitopes of hnRNP-A2 associated with disease activity in patients with rheumatoid arthritis

The heterogeneous nuclear ribonucleoprotein A2 (hnRNP-A2) has been described as an important autoantigen in rheumatoid arthritis (RA) since it is targeted by autoantibodies, autoreactive T cells, and is aberrantly expressed in synovial cells in patients. To identify hnRNP-A2-specific T-cell epitopes possibly associated with pathogenicity, we used an innovative approach. We first scanned 280 overlapping hnRNP-A2 peptides for binding to the RA-associated class II molecules HLA-DR4 and HLA-DR1, leading to a comprehensive selection of binders. The selected peptides were tested in IFN-gamma-specific ELISPOT assay: PBMC from 18% of RA patients showed a significant IFN-gamma response to hnRNP-A2 peptides, 15% to the overlapping sequences 117-133 and/or 120-133, whereas PBMC from healthy individuals tested negative. We measured proliferative responses to these two peptides in another cohort of patients with RA or osteoarthritis: positive responses were found in 28% of RA, but also in 11% of osteoarthritis patients and these responses could be blocked by anti-MHC class II Ab. Remarkably, the presence of 117/120-133-specific T cells was significantly associated with active disease in RA patients, and bone erosion appeared to be more common in T-cell positive patients. These data suggest involvement of hnRNP-A2 specific cellular autoimmune responses in RA pathogenesis.

The role of antibodies in inflammatory arthritis

Inflammatory arthritis presents in a variety of diseases, from rheumatoid arthritis to hepatitis. Antibodies to autoantigens or to microbial constituents are commonly associated with these conditions. In some cases, the antibodies have diagnostic and prognostic relevance. It cannot as yet be determined definitively that any of them mediate joint damage, although the evidence from animal models indicates that this mechanism is likely. The purpose of this article is to give an overview of the spectrum of antibodies found in a variety of inflammatory arthritides. The relevant animal models are also discussed.

Mass spectrometric and peptide chip epitope analysis on the RA33 autoantigen with sera from rheumatoid arthritis patients

As the potential of epitope chips for routine application in diagnostics relies on the careful selection of peptides, reliable epitope mapping results are of utmost interest to the medical community. Mass spectrometric epitope mapping in combination with peptide chip analysis showed that autoantibodies from patients who suffered from rheumatoid arthritis (RA) were directed against distinct surface structures on the full-length human autoantigen RA33 as well as against partial sequences. Using the combined mass spectrometric epitope extraction and peptide chip analysis approach, four sequence motifs on RA33 emerged as immuno-positive, showing that epitopes were not randomly distributed on the entire RA33 amino acid sequence. A sequential epitope motif ((245)GYGGG(249)) was determined on the C-terminal part of RA33 which matched with the Western blot patient screening results using the full-length protein and, thus, was regarded as a disease-associated epitope. Other epitope motifs were found on N-terminal partial sequences ((59)RSRGFGF(65), (111)KKLFVG(116)) and again on the C-terminal part ((266)NQQPSNYG(273)) of RA33. As recognition of these latter three motifs was also recorded by peptide chip analysis using control samples which were negative in the Western blot screening, these latter motifs were regarded as "cryptic epitopes". Knowledge of disease-associated epitopes is crucial for improving the design of a customized epitope peptide chip for RA and mass spectrometric epitope mapping pivotally assisted with selecting the most informative peptide(s) to be used for future diagnostic purposes.

Nucleic acid-associated autoantigens: pathogenic involvement and therapeutic potential

Autoimmunity to ubiquitously expressed macromolecular nucleic acid-protein complexes such as the nucleosome or the spliceosome is a characteristic feature of systemic autoimmune diseases. Disease-specificity and/or association with clinical features of some of these autoimmune responses suggest pathogenic involvement which, however, has been proven in only a few cases so far. Although the mechanisms leading to autoimmunity against nucleic acid-containing complexes are still far from being fully understood, there is increasing experimental evidence that the nucleic acid component may act as a co-stimulator or adjuvans via activation of nucleic acid-binding receptor systems such as Toll-like receptors in antigen-presenting cells. Dysregulated apoptosis and inappropriate stimulation of nucleic acid-sensing receptors may lead to loss of tolerance against the protein components of such complexes, activation of autoreactive T cells and formation of autoantibodies. This has been demonstrated to occur in systemic lupus erythematosus and seems to represent a general mechanism that may be crucial for the development of systemic autoimmune diseases. This review provides a comprehensive overview of the most thoroughly-characterized nucleic acid-associated autoantigens, describing their structure and biological function, as well as the nature and pathogenic importance of the reactivities directed against them. Furthermore, recent advances in immunotherapy such as antigen-specific approaches targeted at nucleic acid-binding antigens are discussed.

Anti-hnRNP and other autoantibodies in systemic sclerosis with joint involvement

OBJECTIVES

To investigate joint involvement in SSc and its relationship with autoantibody to the hnRNP and to anti-cyclic citrullinated peptide (anti-CCP).

METHODS

Sera from 55 SSc patients were investigated. Joint involvement was determined by clinical, radiological and ultrasonographical evaluation. Anti-hnRNP proteins A1 and A2 (anti-hnRNP-A1/A2) antibodies were determined by immunoblotting. Anti-CCP, ACA, anti-topo I (ATA), Sm, U1-RNP, ribosomal RNP, Ro/SSA, La/SSB autoantibody and RF were determined.

RESULTS

Six patients were positive for anti-hnRNP-A2 autoantibody and two were anti-A1 positive. Eight patients had joint erosions: seven of the eight patients positive for anti-hnRNP-A2 or A1 presented articular involvement (P < 0.04) and five of the eight erosive patients were positive for either of the two autoantibodies (P < 0.02). Of the four patients positive for anti-CCP, none had anti-hnRNP but three had erosive aspects. ATAs were found in 10 patients, six of which were also positive for anti-hnRNP (P < 0.05). RF was positive in 16 patients and in seven among those with articular involvement (P < 0.04). RF was significantly associated with anti-hnRNP in patients with erosive arthritis (P < 0.02), but not with the presence of anti-hnRNP alone. Epitope mapping of the three strongest anti-hnRNP-A2-positive sera recognized the same major epitope as patients with RA. SSc patients have higher incidence of erosions and anti-hnRNP-A2/A1 positivity. RF test and anti-hnRNP had a statistically significant diagnostic value for articular involvement.

CONCLUSIONS

These parameters might suggest that autoantibody to both hnRNP antigens might become a non-specific but useful marker for joint involvement in SSc patients and identify SSc patients prone to develop joint damage.

Endosomal Toll-like receptors in autoimmunity: mechanisms for clinical diversity

The endosomal Toll-like receptors (TLR3, TLR7 and TLR9) have been implicated in the pathogenesis of autoimmune diseases. Their signaling pathways show remarkable similarities and yet the outcomes following activation of each of these TLRs lead to clinically distinct autoimmune disease phenotypes. This review discusses how differences may arise at a molecular and cellular level to account for this diversity of responses. Understanding the roles of individual TLR pathways and the relationships between them and non-TLR innate immune pathways in the pathogenesis of diseases such as systemic lupus erythematosis highlights potential treatment targets for this spectrum of autoimmune diseases.

Candidate autoantigens identified by mass spectrometry in early rheumatoid arthritis are chaperones and citrullinated glycolytic enzymes

Introduction

The aim of our study was to identify new early rheumatoid arthritis (RA) autoantibodies.

Methods

Sera obtained from 110 early untreated RA patients (<6 months) were analyzed by western blot using HL-60 cell extract, separated on one-dimensional and two-dimensional gel electrophoresis (1-DE, 2-DE). Sera from 50 healthy blood donors and 20 patients with non-RA rheumatisms were used as controls for 1-DE and 2-DE, respectively. The immunoreactive proteins were identified by MALDI-TOF mass spectrometric analysis and the presence of potential sites of citrullination in each of these proteins was evaluated. FT-ICR mass spectrometry was used to verify experimentally the effect of citrullination upon the mass profile observed by MALDI-TOF analysis.

Results

The 110 1-DE patterns allowed detection of 10 recurrent immunoreactive bands of 33, 39, 43, 46, 51, 54, 58, 62, 67 and 70 kDa, which were further characterized by 2-DE and proteomic analysis. Six proteins were already described RA antigens: heterogeneous nuclear ribonucleoprotein A2/B1, aldolase, α-enolase, calreticulin, 60 kDa heat shock protein (HSP60) and BiP. Phosphoglycerate kinase 1 (PGK1), stress-induced phosphoprotein 1 and the far upstream element-binding proteins (FUSE-BP) 1 and 2 were identified as new antigens. Post-translational protein modifications were analyzed and potentially deiminated peptides were found on aldolase, α-enolase, PGK1, calreticulin, HSP60 and the FUSE-BPs. We compared the reactivity of RA sera with citrullinated and noncitrullinated α-enolase and FUSE-BP linear peptides, and showed that antigenicity of the FUSE-BP peptide was highly dependent on citrullination. Interestingly, the anti-cyclic citrullinated peptide antibody (anti-CCP2) status in RA serum at inclusion was not correlated to the reactivity directed against FUSE-BP citrullinated peptide.

Conclusions

Two categories of antigens, enzymes of the glycolytic family and molecular chaperones are also targeted by the early untreated RA autoantibody response. For some of them, and notably the FUSE-BPs, citrullination is involved in the immunological tolerance breakdown observed earlier in RA patients. Autoantibodies recognizing a citrullinated peptide from FUSE-BP may enhance the sensibility for RA of the currently available anti-CCP2 test.

Epitope spreading to citrullinated antigens in mouse models of autoimmune arthritis and demyelination

Introduction

Anti-citrullinated protein antibodies have a diagnostic role in rheumatoid arthritis (RA); however, little is known about their origins and contribution to pathogenesis. Citrullination is the post-translational conversion of arginine to citrulline by peptidyl arginine deiminase, and increased citrullination of proteins is observed in the joint tissue in RA and in brain tissue in multiple sclerosis (MS).

Methods

We applied synovial and myelin protein arrays to examine epitope spreading of B cell responses to citrullinated epitopes in both the collagen-induced arthritis (CIA) model for RA and the experimental autoimmune encephalomyelitis (EAE) model for MS. Synovial and myelin protein arrays contain a spectrum of proteins and peptides, including native and citrullinated forms, representing candidate autoantigens in RA and MS, respectively. We applied these arrays to characterise the specificity of autoantibodies in serial serum samples derived from mice with acute and chronic stages of CIA and EAE.

Results

In samples from pre-disease CIA and acute-disease EAE, we observed autoantibody targeting of the immunising antigen and responses to a limited set of citrullinated epitopes. Over the course of diseases, the autoantibody responses expanded to target multiple citrullinated epitopes in both CIA and EAE. Using immunoblotting and mass spectrometry analysis, we identified citrullination of multiple polypeptides in CIA joint and EAE brain tissue that have not previously been described as citrullinated.

Conclusions

Our results suggest that anti-citrulline antibody responses develop in the early stages of CIA and EAE, and that autoimmune inflammation results in citrullination of joint proteins in CIA and brain proteins in EAE, thereby creating neoantigens that become additional targets in epitope spreading of autoimmune responses.

Autoantibodies to the translational suppressors T cell intracytoplasmic antigen 1 and T cell intracytoplasmic antigen 1-related protein in patients with rheumatic diseases: increased prevalence in systemic lupus erythematosus and systemic sclerosis and correlation with clinical features

OBJECTIVE

T cell intracytoplasmic antigen 1 (TIA-1) and TIA-1-related protein (TIAR) are involved in posttranscriptional regulation of the expression of tumor necrosis factor alpha (TNFalpha) and other proteins. Given the pivotal role of TNFalpha in chronic inflammatory diseases, this study was undertaken to analyze sera from patients with systemic autoimmune diseases for the presence of autoantibodies to TIA proteins and to investigate the expression of these proteins in inflamed tissue.

METHODS

The presence of autoantibodies to TIA proteins in sera from 385 patients with rheumatic diseases and healthy controls was determined by immunoblotting using recombinant antigens. Expression of TIA proteins in skin and kidney tissue was analyzed by immunohistochemistry. Serum levels of TNFalpha were measured by enzyme-linked immunosorbent assay.

RESULTS

Autoantibodies to TIA-1 and/or TIAR were detected in 61% of patients with systemic lupus erythematosus (SLE), 42% of patients with systemic sclerosis (SSc), 15-31% of patients with other rheumatic diseases, and 6% of healthy controls. Compared with patients negative for anti-TIA antibody, anti-TIA antibody-positive SLE patients had higher disease activity (P = 0.01), elevated antibodies to double-stranded DNA (P = 0.0003), and increased serum TNFalpha levels (P = 0.018). In SLE patients, anti-TIAR antibodies were associated with lupus nephritis (P = 0.02), while in patients with SSc, anti-TIA-1 was associated with lung involvement (P = 0.02). Immunohistochemical analysis of skin and kidney tissue revealed aberrant expression of TIA proteins in skin lesions from SLE and SSc patients, as well as in glomerular cells from SLE patients.

CONCLUSION

Aberrant expression of TIA proteins in inflammatory tissue may lead to systemic autoantibody responses, particularly in SLE and SSc. Increased occurrence of anti-TIA autoantibodies in patients with severe organ involvement may point to a possible pathogenetic role.

Mixed connective tissue disease: what is behind the curtain?

Although there is still an emotional debate over the existence of mixed connective tissue disease, the evidence from animal models suggests that anti-U1RNP antibodies, similar to other autoantibodies in other connective tissue diseases (such as antisynthetase, anticentromere, and antitopoisomerase), play a pathophysiological role in this disease. Despite an antiendothelial effect of anti-U1RNP antibodies, which is reminiscent of anticentromere antibodies, patients with high-titer autoantibodies to U1RNP in the absence of anti-Sm antibodies do not usually have or develop typical systemic sclerosis. Instead, their severe Raynaud's syndrome is commonly accompanied by arthritis, which can be erosive, and by swollen/puffy hands and myositis. Pulmonary arterial hypertension is the major life-threatening complication in these patients and regular screening for this condition is essential.

Multiple specificities of autoantibodies against hnRNP A/B proteins in systemic rheumatic diseases and hnRNP L as an associated novel autoantigen

Spliceosomal small nuclear ribonucleoproteins (U-snRNPs) are frequent and specific targets of autoantibodies in systemic rheumatic diseases. The abundant, functionally related heterogeneous nuclear ribonucleoprotein complexes (hnRNPs) have later defined as a new target of autoantibodies, of which their immunochemical/immunogenic and pathogenic properties are still under investigation. Among hnRNP proteins, those belonging to the A/B type are considered as the major autoantigens targeted by antibodies in sera of patients suffering with rheumatoid arthritis (RA), systemic lupus erythematosus (SLE) and mixed connective tissue disease (MCTD). By performing an extensive screening using rat liver 40S hnRNP antigenic material, we document here the existence of multiple specificities of anti-hnRNP A/B autoantibodies in sera of Greek patients suffering with a spectrum of systemic rheumatic diseases. This included patients with SLE, Sjogren's syndrome (SS), Scleroderma (SSc) and a specific group of patients mostly with undifferentiated disease (UD patients). In total, four distinct types of anti-hnRNP A/B autoantibodies have been recognized. The first two referred to the known anti-hnRNPA2(RA33) and anti-hnRNP A1; the latter appearing very rarely. The third was of the new type selectively reacting with hnRNP B2 and an hnRNP A3 variant, while the fourth was a rare case of anti-hnRNP B2 alone. In addition, a novel specificity of autoantibodies against hnRNP L protein was identified in association with anti-hnRNP A/B antibodies. The co-existence within a serum of autoantibodies having variable specificity for hnRNP A/B and L autoantigens was shown. Specific immunochemical features of the identified autoantibodies are presented and a possible mechanism of autoepitope spreading within protein components of hnRNP complexes is discussed.

The spliceosomal autoantigen heterogeneous nuclear ribonucleoprotein A2 (hnRNP-A2) is a major T cell autoantigen in patients with systemic lupus erythematosus

A hallmark of systemic lupus erythematosus (SLE) is the appearance of autoantibodies to nuclear antigens, including autoantibodies directed to the heterogeneous nuclear ribonucleoprotein A2 (hnRNP-A2), which occur in 20% to 30% of SLE patients as well as in animal models of this disease. To investigate the underlying cellular reactivity and to gain further insight into the nature and potential pathogenic role of this autoimmune response we characterized the T cell reactivity against hnRNP-A2 in patients with SLE in comparison to healthy controls. Cellular proliferation of peripheral blood T cells to hnRNP-A2 was determined by [3H]thymidine incorporation and T cell clones (TCCs) specific for hnRNP-A2 were grown by limiting dilution cloning; IFNgamma, IL-4 and IL-10 in culture supernatants were measured by ELISA. Bioactivity of culture supernatants was determined by incubation of anti-CD3/anti-CD28 stimulated peripheral blood CD4+ T cells with supernatants of TCCs. Stimulation assays performed with peripheral blood mononuclear cells of 35 SLE patients and 21 healthy controls revealed pronounced proliferative responses in 66% of SLE patients and in 24% of the controls, which were significantly higher in SLE patients (p < 0.00002). Furthermore, hnRNP-A2 specific TCCs generated from SLE patients (n = 22) contained a relatively high proportion of CD8+ clones and mostly lacked CD28 expression, in contrast to TCCs derived from healthy controls (n = 12). All CD4+ TCCs of patients and all control TCCs secreted IFNgamma and no IL-4. In contrast, CD8+ TCCs of patients secreted very little IFNgamma, while production of IL-10 did not significantly differ from other T cell subsets. Interestingly, all CD8+ clones producing IL-10 in large excess over IFNgamma lacked expression of CD28. Functional assays showed a stimulatory effect of the supernatants derived from these CD8+ CD28- hnRNP-A2 specific TCCs that was similar to that of CD4+ CD28+ clones. Taken together, the pronounced peripheral T cell reactivity to hnRNP-A2 observed in the majority of SLE patients and the distinct phenotype of patient-derived CD8+ TCCs suggest a role for these T cells in the pathogenesis of SLE.

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.

MCTD: is it rare in India?

Mixed connective tissue disease (MCTD) has been rarely reported from India. Thus, we did a retrospective analysis of cases of MCTD seen at our hospital during the last 13 years. We found 16 cases among 441 patients with connective tissue disease. All the 16 patients (15 females) of MCTD fulfilled classification criteria by Kasukawa and at least one of the other two (Sharp's and Alarcon-Sergovia). Raynaud's phenomenon, sclerodactyly, puffy fingers, esophageal hypomotility, and pulmonary disease were the most common manifestations. At a median follow-up of 12 months (1-172), 12 patients developed features of limited scleroderma and three patients had pulmonary hypertension.

Heterogeneous nuclear ribonucleoprotein P2 is an autoantibody target in mice deficient for Mer, Axl, and Tyro3 receptor tyrosine kinases

Deficiencies in clearance of apoptotic cells predispose to the development of autoimmune disease. This is evident in mice lacking the receptor tyrosine kinases Tyro3, Axl, and Mer. Deficient mice exhibit an increased abundance of apoptotic cells in tissues and manifest diverse autoimmune conditions. To test these mice for the presence of autoantibodies to apoptotic cells, we generated spontaneous splenic B cell hybridomas and used a novel microscopy screen to detect Ab binding to apoptotic Jurkat cells. From hybridomas secreting IgG Abs reactive with apoptotic cells, we selected one that recreated the major serum specificity for apoptotic cells. The Ab LHC7.15 bound to an Ag that is differentially distributed between the nucleus and the cytoplasm in live and apoptotic cells. In late apoptotic cells, the Ag coalesces into aggregates that bleb from the cell surface. Immunopurification of the Ag, followed by mass spectrometry, identified a protein of 69 kDa whose partial sequence matched heterogeneous nuclear ribonucleoprotein P2. This multifunctional protein binds DNA, RNA, and several known ribonucleoprotein autoantigens. Our observations indicate that a ribonucleoprotein complex, formed and translocated to the cell surface in apoptosis, represents a potent stimulus for breaking tolerance and inducing systemic autoimmunity in mice with defective clearance of cell remnants.

Aberrant Expression of the Autoantigen Heterogeneous Nuclear Ribonucleoprotein-A2 (RA33) and Spontaneous Formation of Rheumatoid Arthritis-Associated Anti-RA33 Autoantibodies in TNF-α Transgenic Mice

Human TNF-alpha transgenic (hTNFtg) mice develop erosive arthritis closely resembling rheumatoid arthritis (RA). To investigate mechanisms leading to pathological autoimmune reactions in RA, we examined hTNFtg animals for the presence of RA-associated autoantibodies including Abs to citrullinated epitopes (anti-cyclic citrullinated peptide), heterogeneous nuclear ribonucleoprotein (hnRNP)-A2 (anti-RA33), and heat shock proteins (hsp) (anti-hsp). Although IgM anti-hsp Abs were detected in 40% of hTNFtg and control mice, IgG anti-hsp Abs were rarely seen, and anti-cyclic citrullinated peptide Abs were not seen at all. In contrast, >50% of hTNFtg mice showed IgG anti-RA33 autoantibodies, which became detectable shortly after the onset of arthritis. These Abs were predominantly directed to a short epitope, which was identical with an epitope previously described in MRL/lpr mice. Incidence of anti-RA33 was significantly decreased in mice treated with the osteoclast inhibitor osteoprotegerin and also in c-fos-deficient mice lacking osteoclasts. Pronounced expression of hnRNP-A2 and a smaller splice variant was seen in joints of hTNFtg mice, whereas expression was low in control animals. Although the closely related hnRNP-A1 was also overexpressed, autoantibodies to this protein were infrequently detected. Because expression of hnRNP-A2 in thymus, spleen, brain, and lung was similar in hTNFtg and control mice, aberrant expression appeared to be restricted to the inflamed joint. Finally, immunization of hTNFtg mice with recombinant hnRNP-A2 or a peptide harboring the major B cell epitope aggravated arthritis. These findings suggest that overproduction of TNF-alpha leads to aberrant expression of hnRNP-A2 in the rheumatoid joint and subsequently to autoimmune reactions, which may enhance the inflammatory and destructive process.

Identification of immunodominant autoantigens in rat autoimmune orchitis

Infection and inflammation of the genital tract are amongst the leading causes of male infertility. Experimental autoimmune orchitis (EAO) in the rat serves as a model for the investigation of inflammatory testicular impairment. In this study, experiments were conducted to identify the molecules that are responsible for eliciting the autoimmune attack on the testis. EAO was induced in in-bred Wistar rats by active immunization with testis homogenates (EAO group I). Development of disease was observed using histological techniques and a new non-invasive three-dimensional (3D) imaging technology for in vivo monitoring, termed flat-panel volumetric computed tomography (fpvCT). Examination of control and EAO testes demonstrated the superior image quality of high-resolution fpvCT. A proteomics approach using 2D SDS-PAGE and immunoblotting analysis with EAO sera identified 12 spots. Seven were subsequently identified by mass spectrometry as heat shock proteins 60 (Hsp60) and 70 (Hsp70), disulphide isomerase ER-60, alpha-1-anti-trypsin, heterogeneous nuclear ribonucleoprotein H1 (hnRNP H1), sperm outer dense fibre major protein 2 (ODF-2), and phosphoglycerate kinase 1. Hsp70, ODF-2, hnRNP H1, and ER-60 were identified by all EAO sera studied. To test the capacity of the identified proteins to elicit testicular autoimmune disease, recombinant proteins were used either individually or in combination to immunize rats (EAO group II). In all groups, the incidence of EAO was 25%. Inflammatory-type (ED1+) and resident (ED2+) macrophages, lymphocytes (CD45RA+), and dendritic cells (Ox-62+) were strongly increased in EAO group II animals, comparable to the testes of EAO I rats. Pre-immunization with a low dose of recombinant Hsp 70, hnRNP H1 or ODF-2 before induction of EAO with testis homogenate significantly delayed the onset of EAO but could not prevent disease. The identification of testicular autoantigens will allow a better understanding of disease pathogenesis and could provide a basis for the development of novel therapies for inflammation-based male infertility.

Antigen microarray profiling of autoantibodies in rheumatoid arthritis

OBJECTIVE

Because rheumatoid arthritis (RA) is a heterogeneous autoimmune disease in terms of disease manifestations, clinical outcomes, and therapeutic responses, we developed and applied a novel antigen microarray technology to identify distinct serum antibody profiles in patients with RA.

METHODS

Synovial proteome microarrays, containing 225 peptides and proteins that represent candidate and control antigens, were developed. These arrays were used to profile autoantibodies in randomly selected sera from 2 different cohorts of patients: the Stanford Arthritis Center inception cohort, comprising 18 patients with established RA and 38 controls, and the Arthritis, Rheumatism, and Aging Medical Information System cohort, comprising 58 patients with a clinical diagnosis of RA of <6 months duration. Data were analyzed using the significance analysis of microarrays algorithm, the prediction analysis of microarrays algorithm, and Cluster software.

RESULTS

Antigen microarrays demonstrated that autoreactive B cell responses targeting citrullinated epitopes were present in a subset of patients with early RA with features predictive of the development of severe RA. In contrast, autoimmune targeting of the native epitopes contained on synovial arrays, including several human cartilage gp39 peptides and type II collagen, were associated with features predictive of less severe RA.

CONCLUSION

Proteomic analysis of autoantibody reactivities provides diagnostic information and allows stratification of patients with early RA into clinically relevant disease subsets.

Does Mixed Connective Tissue Disease Exist? Yes

For patients who have combined features of rheumatoid arthritis, the limited cutaneous form of systemic sclerosis, and inflammatory myopathies, the concept of mixed connective tissue disease (MCTD) often helps to predict and diagnose organ problems and to educate the patient accordingly. With high titer IgG antibodies to U1 ribonucleoprotein (U1-snRNP), this concept is supported by a specific serologic marker, and autoantibodies to U1-snRNP and to heterogeneous nuclear ribonucleoprotein (hnRNP)-A2 display MCTD specificity with regard to the recognized epitopes. In addition, the association of MCTD with HLA-DR4 distinguishes it from systemic erythematosus lupus and systemic sclerosis, and speaks to its being a disease entity, rather than a mixture of yet undifferentiated collagen vascular diseases. The authors believe that the concept is useful in daily practice and accurate in the idea that MCTD constitutes a disease entity of its own.

Autoantibodies in the Pathogenesis of Mixed Connective Tissue Disease

Antibodies to U1-RNP are part of the clinical definition of mixed connective tissue disease (MCTD). These antibodies and other well-defined antibodies tend to arise together in affected patients. Although still speculative, hypotheses that link U1-RNP antibodies to the development of autoimmunity in MCTD and that associate U1-RNP antibodies with mechanisms of tissue injury in MCTD have emerged and are being tested. Salient features of these hypotheses include: (1) an antigen-driven response that is due to impaired clearance of potentially immunogenic self-antigens, (2) inadequate B- and T-cell tolerance to RNP autoantigens, and (3) immunogenic properties of the RNA component of targeted ribonucleoproteins. Further studies are needed to establish whether anti-RNP antibodies have prognostic importance that is relevant to practicing clinicians.

Mixed Connective Tissue Disease: Still Crazy After All These Years

Mixed connective tissue disease (MCTD) remains a controversial diagnosis. The classification criteria have changed significantly from the original description by Sharp and colleagues in 1972 after follow-up of the original and other MCTD patients. In this article we review the clinical, serologic, and genetic studies of MCTD published in the last 10 years and ask if this term is appropriate.

Autoantibody profiling as early diagnostic and prognostic tool for rheumatoid arthritis

BACKGROUND

Early treatment prevents progression of joint damage in rheumatoid arthritis (RA), but diagnosis in early disease is impeded by lack of appropriate diagnostic criteria.

OBJECTIVE

To study the value of rheumatoid factor (RF), anti-cyclic citrullinated peptide autoantibodies (anti-CCP), and anti-RA33 autoantibodies for diagnosis of RA and prediction of outcome in patients with very early arthritis.

METHODS

The prospective follow up inception cohort included 200 patients with very early (<3 months) inflammatory joint disease. Autoantibodies were measured at baseline and analysed in a tree based model which aimed at determining the added diagnostic value of testing for anti-CCP and anti-RA33 as compared with RF alone.

RESULTS

RA was diagnosed in 102 patients, while 98 developed other inflammatory arthropathies. Receiver operator curve analysis showed an optimum cut off level for RF at 50 U/ml, above which anti-CCP and anti-RA33 had no additional diagnostic value. Remarkably, RF >or=50 U/ml and anti-CCP showed similar sensitivity and high specificity for RA, but overlapped considerably. Anti-RA33 was less specific and did not correlate with RF or anti-CCP. Among patients with RA, 72% showed at least one of these three autoantibodies, compared with 15% of non-RA patients. RF >or=50 U/ml and anti-CCP were predictors of erosive disease, whereas anti-RA33 was associated with mild disease.

CONCLUSIONS

Stepwise autoantibody testing in early inflammatory joint disease, starting with RF, followed by anti-CCP (in patients with RF <50 U/ml), and finally anti-RA33, should be used as a sensitive and effective strategy for distinguishing patients with RA at high risk for poor outcome.

MCTD - Mixed Connective Tissue Disease. MCTD - Mixed Connective Tissue Disease

Mixed connective tissue disease is a disease entity characterized by overlapping symptoms of lupus erythematosus (LE), systemic sclerosis (SSc), polymyositis/dermatomyositis (PM/DM) and rheumatoid arthritis (RA). Diagnostic criteria include high titers of antibodies against U1RNP as well as the presence of at least 3 of 5 of the following clinical features: edema of hands, synovitis, myositis, Raynaud phenomenon and acroscierosis. In terms of the pathogenesis, genetic as well as infectious (viral) factors appear to play a role. The acceptance of MCTD as a distinct disease entity is controversial. Terms such as "undifferentiated connective tissue disease" or "overlapping syndromes" are not helpful. One-quarter of MCTD patients transform into LE, while one-third progress to SSc. Therapeutic recommendations are glucocorticoids in combination with immunosuppressive agents and endothelin receptor antagonists. Double blind studies are not available. The prognosis is relatively good. Causes of death include pulmonary hypertension, infections and both pulmonary and cardiac failure.

Autoantibodies against heterogeneous nuclear ribonucleoprotein B1 in CSF of MS patients

Heterogeneous nuclear ribonucleoproteins (hnRNPs) play an important role as the autoantigens in certain autoimmune disorders including neurological diseases such as HTLV-1-associated myelopathy/tropical spastic paraparesis and paraneoplastic neurological syndromes. To clarify their implication in multiple sclerosis (MS), we assayed antibodies (Abs) against hnRNP A and B proteins in sera and cerebrospinal fluid (CSF) of MS patients and compared the results with 25 patients with other neurological diseases (ONDs). Using recombinant hnRNP A1, A2, and B1 proteins and Western blotting for the assay, we found Abs against hnRNP B1 in CSF from 32 of 35 MS patients (91.4%) but not in any sera or CSF of the 25 OND patients. Most notably, no Abs against hnRNP B1 were found in sera of all 22 MS patients examined. Although Abs against hnRNP A1 and A2 were concomitantly found in CSF reacting with B1, their incidence and immunoreactivity were lower or weaker than those of anti-hnRNP B1 Abs. There was no correlation between the reactivity of CSF with hnRNP B1 and CSF parameters-such as the number of the cells and the IgG level-or clinical parameters-such as duration of illness and disease activity. The selective generation of Abs against hnRNP B1 in CSF was shown to be highly specific for MS, which makes them a disease marker.

[Autoantibodies in the diagnosis of rheumatoid arthritis. Utility of anti-cyclic citrullinated peptides]

Rheumatoid arthritis (RA) is one of the commonest inflammatory joint diseases, affecting about 1% of population. Despite its high prevalence, many aspects of its etiopathogeny remain unclarified. Recently, some important findings related to RA pathogenesis with a number of consequences on the treatment and prognosis of this aggressive disease have been reported. It is important to diagnose and to treat the disease early to avoid long-term damage. However, the search for a specific and sensitive serological test to early identify RA patients has yielded poor results. Autoantibodies are found in the sera of RA patients with a variable prevalence and have been classified into RA-specific and RA-unspecific antibodies. It has been recently demonstrated that many of those RA-specific autoantibodies recognize peptides that contain citrulline residues and, thus, a new test to measure the presence of anti-cyclic citrullinated peptides (CCP) antibodies has been developed. Research publications about the utility of anti-CCP antibodies not only in the diagnosis, but also in the prognosis, of RA are increasing exponentially. In fact, the value of the measurement of anti-CCP antibodies is already widely recognized. This review summarizes the most important data about the autoantibodies employed to date in the diagnosis of RA, including anti-CCP antibodies.

Advances in B-cell epitope analysis of autoantigens in connective tissue diseases

The characterization of autoantibody specificities in rheumatic diseases is important in both diagnostic and basic research areas. Identification of the epitopes recognized by autoantibodies and their clinical and biological significance is not a trivial task. Epitopes may range in complexity from simple linear sequences of amino acids to complex quaternary structures. In addition to this structural complexity the frequency with which an autoantigen and its epitopes are recognized in a patient population may be useful in diagnosis, defining disease subgroups, and may offer information on disease prognosis. In this review recent advances in the epitope mapping of autoantigens in connective tissue diseases are discussed, with particular emphasis placed on the methodologies used to identify epitopes and the classification of the structural features of epitopes. To illustrate the identification of epitope structure, clinically relevant autoantigens, including CENP-A, PM/Scl-100, fibrillarin, filaggrin, Ro-52, and dsDNA, are discussed as examples of each type of epitope.

Orderly Pattern of Development of the Autoantibody Response in (New Zealand White × BXSB)F1 Lupus Mice: Characterization of Target Antigens and Antigen Spreading by Two-Dimensional Gel Electrophoresis and Mass Spectrometry

Immunoblots of a two-dimensional PAGE-separated HL-60 cell proteomic map and mass spectrometry were combined to characterize proteins targeted by autoantibodies produced by male (New Zealand White x BXSB)F(1) (WB) mice that develop lupus and anti-phospholipid syndrome. Analysis of sera sequentially obtained from seven individual mice at different ages showed that six proteins, vimentin, heat shock protein 60, UV excision-repair protein RAD23, alpha-enolase, heterogeneous nuclear ribonucleoprotein L, and nucleophosmin, were the targets of the B cell autoimmune response, and that autoantibodies to them were synthesized sequentially in an orderly pattern that recurred in all the male WB mice analyzed: anti-vimentin first and anti-nucleophosmin last, with anti-RAD23 and anti-heat shock protein 60, then anti-alpha-enolase and anti-heterogeneous nuclear ribonucleoprotein L Abs occuring concomitantly. Anti-vimentin reactivity always appeared before anti-cardiolipin and anti-DNA Abs, suggesting that vimentin is the immunogen initiating the autoimmune process. The pattern of HL-60 proteins recognized by female WB sera differed from that of male sera, indicating that the Y chromosome-linked autoimmune acceleration gene is not an accelerator but a strong modifier of the autoimmune response. Thus, 1) combining two-dimensional PAGE and mass spectrometry constitutes a powerful tool to identify the set of Ags bound by autoantibodies present in a single serum and the whole autoantibody pattern of an autoimmune disease; 2) the diversification of the autoimmune response in male WB mice occurs in a predetermined pattern consistent with Ag spreading, and thus provides a useful model to further our understanding of the development of the autoantibody response in lupus.