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Autoimmune diseases are numerous and heterogeneous, with a broad spectrum of clinical presentations and unpredictable courses. Treatment options include such medications as analgesics and nonsteroidal antiinflammatory drugs, disease-modifying antirheumatic drugs, biological agents, and glucocorticoids. If the disease is diagnosed early, the major treatment goal is remission with no active inflammation and no functional deterioration. Numerous mouse and human studies have improved our understanding of the contribution of different immune mediators to the pathogenesis of autoimmune diseases. Despite these advances, the main causes of the breakdown of immune tolerance that lead to the development of autoimmune diseases remain largely unknown. A large proportion of the risk for developing an autoimmune disease is attributable to genetic factors. For example, HLA regions contribute to approximately half of the genetic susceptibility for rheumatoid arthritis (RA).7 Genomewide association studies have identified variants in potentially pathogenic genes in non-HLA regions, including PTPN22 8 [protein tyrosine phosphatase, non-receptor type 22 (lymphoid)], the TRAF1–C5 locus [ TRAF1 (TNF receptor-associated factor 1) to C5 (complement component 5)], PADI4 (peptidyl arginine deiminase, type IV), and STAT4 (signal transducer and activator of transcription 4). Other polymorphisms located in genes coding for the cytokines tumor necrosis factor (TNF), interleukin-1 (IL-1), IL-6, IL-4, and IL-5 seem to be related to an aggressive disease phenotype. Epigenetics and microRNAs are receiving increasing attention as mechanisms that interact with the genome in leading to the persistent inflammatory response in autoimmune disease. The clinical management of autoimmune diseases presents a considerable challenge to healthcare providers. The lack of definition of disease subsets in individuals with early autoimmune disease is one of the key gaps in the field. In this Q&A, 3 experts discuss recent developments in the area of early diagnosis of autoimmune diseases and their implications for improved treatment strategies. Can you highlight some recent …

Rheumatoid arthritis (RA) is an autoimmune disease characterized by autoantibodies against citrullinated antigens. The importance of citrulline for the epitopes bound by these autoantibodies, referred to as ACPA (anti-citrullinated peptide/protein antibodies), was first described in 1998. In addition to citrullinated proteins, cyclic citrullinated peptides (CCP) can also be used as test substrates for detecting ACPA. The standard test for these antibodies is the second-generation CCP (CCP2) test, which is one of the best in terms of sensitivity and specificity. The generation of ACPA is an early event in the disease course, and is dependent on the presence of certain MHC class II alleles. ACPA in the inflamed synovium have been shown to associate with citrullinated antigens to form immune complexes, resulting in progression of the inflammatory process. The involvement of ACPA in the chronicity of RA is probably the reason why ACPA-positive patients have a more erosive disease course than ACPA-negative patients. The presence of ACPA has been included in the 2010 RA classification criteria. Thus, it is important to further standardize ACPA testing, for example by including an internal serum standard, which may lead to a better distinction between low and high ACPA levels.

The most specific biomarker associated with the diagnosis of rheumatoid arthritis (RA) is autoantibodies to citrullinated peptides/proteins (ACPA). Though recognized as an important marker of progressive erosive disease its use has been hampered by doubt about what is a positive versus a negative reaction in the several assays that have become available commercially. This review intends to indicate that the CCP2 assay has the highest specificity and sensitivity in stratified studies that encompass sera from RA patients and non-RA inflammatory controls compared to other ACPA tests. Still, larger and strictly stratified studies are highly warranted to substantiate this conclusion.

To identify peripheral blood autoantibody and cytokine profiles that characterise clinically relevant subgroups of patients with early rheumatoid arthritis using arthritis antigen microarrays and a multiplex cytokine assay.Serum samples from 56 patients with a diagnosis of rheumatoid arthritis of6 months' duration were tested. Cytokine profiles were also determined in samples from patients with psoriatic arthritis (PsA) and ankylosing spondylitis (n = 21), and from healthy individuals (n = 19). Data were analysed using Kruskal-Wallis test with Dunn's adjustment for multiple comparisons, linear correlation tests, significance analysis of microarrays (SAM) and hierarchical clustering software.Distinct antibody profiles were associated with subgroups of patients who exhibited high serum levels of tumour necrosis factor (TNF)alpha, interleukin (IL)1beta, IL6, IL13, IL15 and granulocyte macrophage colony-stimulating factor. Significantly increased autoantibody reactivity against citrullinated epitopes was observed in patients within the cytokine "high" subgroup. Increased levels of TNFalpha, IL1alpha, IL12p40 and IL13, and the chemokines eotaxin/CCL11, monocyte chemoattractant protein-1 and interferon-inducible protein 10, were present in early rheumatoid arthritis as compared with controls (p0.001). Chemokines showed some of the most impressive differences. Only IL8/CXCL8 concentrations were higher in patients with PsA/ankylosing spondylitis (p = 0.02).Increased blood levels of proinflammatory cytokines are associated with autoantibody targeting of citrullinated antigens and surrogate markers of disease activity in patients with early rheumatoid arthritis. Proteomic analysis of serum autoantibodies, cytokines and chemokines enables stratification of patients with early rheumatoid arthritis into molecular subgroups.

Rheumatoid arthritis (RA) is a common, systemic autoimmune disease characterized by chronic inflammation of the synovium, that can lead to progressive joint destruction and in many cases results in severe disability and poor quality of life. With the availability of more sophisticated and effective therapies and with increasing evidence that the first few months of disease represent an unique therapeutic opportunity and that such early therapeutic intervention is crucial in preventing irreversible joint damage, it is widely accepted that early and accurate diagnosis of RA is critical in disease management. Within the last three years a growing number of publications have reported that the second generation anti-CCP (cyclic citrullinated peptide) test may become the marker of choice for diagnosing early RA as it appears to be highly specific for the disease with a sensitivity comparable to the widely used but less specific rheumatoid factor test. Additionally, anti-CCP2 positivity can predict future development of RA in both asymptomatic individuals and in patients with undifferentiated arthritis. Furthermore, antibody levels at presentation can correlate with progression to erosive disease.

Rheumatoid arthritis (RA) is a common systemic autoimmune disease with a prevalence of about 1% worldwide [1]. The American College of Rheumatology (ACR) criteria for the classification of RA [2] are not very well suited to diagnose RA at an early stage of the disease [3, 4], because these criteria rely heavily on the expression of clinical symptoms of RA. In early RA these clinical parameters are often not (yet) manifest. Therefore, a specific and sensitive (serological) marker, which is present very early in the disease, is needed. A good marker should ideally not only indicate the development of the disease, but also be able to predict its erosive or non-erosive progression. The serological parameter that meets these requirements for a good and useful marker for early RA is the anti-citrullinated protein antibody. The sensitivity of this antibody is comparable to that of the rheumatoid factor (RF) (approximately 80%), but its specificity is much higher, about 98%. Several assays have been developed to detect this class of autoantibodies, which are termed anti-CCP because the most sensitive test is based upon cyclic citrullinated peptides. This review will discuss the potential of this autoantibody system for the diagnosis and prognosis of RA.

Rheumatoid arthritis (RA) is a chronic, destructive autoimmune disease affecting the joints. With more sophisticated and effective therapies becoming available and with the understanding that early intervention is crucial in preventing irreversible joint damage, it is more and more important to diagnose RA at a very early stage in the disease. To facilitate diagnosis during the early stages of the disease, when often not all clinical symptoms are manifest, a good serological marker is needed. Antibodies directed to citrullinated proteins provide this ability. The most sensitive assay to detect these antibodies is the so-called anti-cyclic citrullinated peptide (CCP) enzyme-linked immunosorbent assay (ELISA) assay. In this review, the diagnostic and prognostic potential and the general utility in clinical practice of anti-CCP antibodies are discussed. Furthermore, we elaborate on the mechanisms involved in the generation of citrullinated autoantigens and the possible role of the anti-CCP antibodies and their antigens in the disease.

Introduction Autoimmune serology has become a potentially powerful tool for experienced clinicians. However, it currently is not being used optimally due to lack of widely used standardized assays, local working conditions, traditions, different technology, cost constraints by medical insurers, and ability on the part of clinicians to correctly interpret the results of certain assays. New serologic technologies and assays are developed by laboratory scientists and the commercial industry at a very fast pace and may eventually lead to better reproducibility in confirming a diagnosis and estimating prognosis, ultimately improving the quality of clinical care. To achieve this goal, the accuracy of such testing must be demonstrated in studies involving sufficiently large patient populations before a new assay can be accepted for clinical use. In the past, there have been very few studies with a prospective, unbiased, multicenter design. Thus, the clinical accuracy of certain laboratory diagnostic studies is still unknown. To be useful in a clinical day-to-day diagnostics setting, the differential diagnostic potential and performance characteristics of a test must be known so that clinical misinterpretation, false diagnoses, and potentially harmful treatment can be avoided. The degree to which an assay will give false-positive or false-negative results is important. To aid in developing a followup and therapeutic strategy in a given patient, the prognostic significance of identifying a certain autoantibody in a patient with clinical findings of an autoimmune disease should be known. Presence of autoantibodies indicating a poor prognosis in the clinical setting of early signs of disease should lead to appropriate followup and monitoring of risk manifestations. Such findings should also evoke early awareness of the potential need for effective treatment, before irreversible organ damage takes place. Factual knowledge about these matters necessitates close collaboration between patients, experienced and motivated clinicians, and laboratory scientists, as well as cooperation with the diagnostics industry. Once a diagnostic assay has been developed, standardized postmarketing surveillance and quality assurance by manufacturers and laboratories alike should be mandatory (1).

SUMMARY Coimmunoprecipitation studies with SW5, a frequently used and specific mouse monoclonal antibody (mAb) directed against the human La autoantigen, led to the identification of a functionally unrelated 80 000 MW protein, designated early endosome antigen 2 (EEA2). EEA2 appeared to be directly targeted by mAb SW5. Because an RNA-binding domain, a structural element of La containing the SW5-epitope, was not discernable in the primary structure of EEA2, the SW5-epitope on EEA2 was determined. Coiled-coil region 3 of EEA2 appeared to contain the epitope recognized by SW5. The SW5 epitope regions of La and EEA2 share a limited sequence homology and probably share a higher degree of structural similarity at the tertiary level. Most likely, the most critical determinants for recognition by SW5 reside in elements adopting alpha-helical conformations. These data indicate that the application of specific mAbs to purify and characterize (functionally) interacting proteins can be severely obscured by the cross-reactivity of mAbs with structurally, but not functionally, similar proteins.

Objective To understand the regulation of anti–citrulline-containing peptide antibody (anti-CCP) production in rheumatoid arthritis (RA), production of anti-CCP by B cells derived from peripheral blood (PB), bone marrow (BM), and synovial fluid (SF) was examined. Methods Purified PB and SF B cells were isolated by negative selection and then cultured in the absence or presence of L–CD40 ligand cells and interleukin-10 or anti-CD3–activated T cells. Total IgM and IgM–anti-CCP were detected after 14 days of culture by enzyme-linked immunosorbent assay. Enzyme-linked immunospot assays were performed to analyze the frequency of cells that spontaneously produced IgM–anti-CCP in BM and SF B cells. Results IgM–anti-CCP autoantibodies were induced in PB B cells from healthy controls and RA patients following coculture with activated T cells or application of the CD40 activation system, whereas no production could be detected when PB B cells were cultured in the absence of a stimulus. SF and BM B cells from anti-CCP–seropositive RA patients, but not anti-CCP–seronegative patients, actively produced IgM–anti-CCP without stimulation. The frequency of spontaneous production of IgM–anti-CCP among the IgM-secreting cells ranged from 2.2% to 25%. Conclusion These results indicate the presence of B cell precursors for anti-CCP autoantibodies that are able to produce antibodies upon stimulation in the PB B cell repertoire of healthy controls and patients with RA. In contrast, B cells that actively secreted anti-CCP were specifically present in the BM and SF compartment of anti-CCP–seropositive RA patients. The local presence of anti-CCP–secreting cells in the inflamed joints provides evidence for an antigen-driven maturation of CCP-specific B cells at the site of inflammation in RA.

Objective. Proteins that are phosphorylated during apoptosis are commonly precipitated by autoantibodies found in the sera of patients with systemic lupus erythematosus. We sought to determine whether scleroderma autoantigens such as small nucleolar RNPs (snoRNP) also associate with phosphoproteins in response to various cellular stressors. Methods. We screened a panel of monoclonal antibodies derived from mice exposed to mercury, a well-characterized murine model of the anti-snoRNP autoimmune response, for the ability to selectively precipitate phosphoproteins from radiolabeled lysates prepared from Jurkat T cells subjected to stressful stimuli. Results. Monoclonal antibodies reactive with snoRNPs precipitated a phosphoprotein complex (pp42, pp34, and pp23) from lysates prepared from apoptotic cells. Several novel phosphoproteins (pp62 and pp18) were also observed. The phosphorylation and/or recruitment of these proteins to the snoRNP complex is induced by multiple apoptotic stimuli (e.g., Fas ligation, anisomycin, or ultraviolet irradiation), an effect that is blocked by overexpression of Bcl-2. We were unable to demonstrate an association of the phosphoprotein complex with snoRNPs in cells treated with the xenobiotic agent mercury. The snoRNP-associated phosphoprotein complex is composed of serine/arginine (SR) splicing factors, including SRp40. Conclusion. The association of phosphorylated SR proteins with snoRNPs in cells undergoing apoptosis suggests that the immune response to fibrillarin that characterizes a subset of patients with scleroderma may be related to cell death induced by apoptotic stimuli (e.g., Fas ligation, irradiation, or chemical toxins), or by exposure to mercury.

Systemic lupus erythematosus (SLE) is an autoimmune disease that is characterized by the presence of high immunoglobulin serum titers, but the mechanism by which these arise remains unclear. It has been suggested that the disease is associated with specific antibody features, including variable gene use, the presence of charged complementarity-determining region residues and/or an aberrant process of secondary light chain rearrangement. To study this in more detail, we compared variable, diversity and joining gene segment use, somatic mutation, and heavy and light chain pairings in single peripheral IgG(+) B cells between one normal (209 B cells) and two SLE (156 B cells) donors. In contrast to others, we found no systematic differences, indicating that the memory B cell repertoires in normal and SLE donors are shaped in a similar way.

Objective To determine the performance characteristics of enzyme-based immunoassay (EIA) kits for the detection of antinuclear and other autoantibodies of defined specificities. Methods Nine manufacturers of EIA kits to detect antibodies of defined specificities participated in a study in which they received coded sera from the Centers for Disease Control and Prevention. These coded sera contained different dilutions of antibody of one specificity mixed with sera containing antibodies of other specificities. The manufacturers were asked to use their standard technology to determine antibody content and send the data to a committee of the International Union of Immunological Societies for analysis. The data were analyzed for sensitivity and specificity in the detection of anti–double-stranded DNA (anti-dsDNA), anti–single-stranded DNA, antihistone, anti-Sm, anti–U1 RNP, anti-SSA/Ro, anti-SSB/La, anti–Scl-70 (DNA topoisomerase I), anticentromere, and anti–Jo-1 antibodies. In addition, replicate samples were included in the coded sera to evaluate the precision of each EIA method. Results Lack of sensitivity and specificity was most evident in the anti-dsDNA and anti-Sm kits, although 2 kits for anti-dsDNA achieved acceptable sensitivity and specificity. Generally, anti-SSA/Ro, anti-SSB/La, anti–Scl-70, anticentromere, and anti–Jo-1 kits performed well. Many false-positive results were obtained with a multiple myeloma serum containing cryoprecipitates, but multiple myeloma sera without cryoprecipitates presented no problem in the EIA system. Precision, based on evaluation of replicate samples, varied from very good to poor. Conclusion No single manufacturer was clearly superior to others in terms of their products' overall sensitivity, specificity, and precision. Areas that needed improvement were in kits for the detection of antibodies to dsDNA and to Sm antigen. Some EIA kits achieved good sensitivity and specificity. Individual manufacturers were informed of the performance of their respective kits so they could take measures to correct perceived deficiencies and thus improve the reliability of a group of important diagnostic assays used in the evaluation of systemic rheumatic diseases.

Objective. To define the fine specificity of the 10 reference sera used for determination of antinuclear antibodies (ANA) and ANA subsets which are available from the Arthritis Foundation (AF) and from the Centers for Disease Control and Prevention (CDC). Methods. AF/CDC sera were assessed by experienced laboratory staff, using indirect immunofluorescence and Western blotting. Results. The original assignment of fluorescence patterns to 4 reference sera was confirmed, and the fluorescence intensities were determined using reference fluorescent beads. On Western blots, sera AF/CDC2 (anti—SS-B/La) and AF/CDC7 (anti—SS-A/Ro) did not detect Ro antigens, sera AF/CDC9 and AF/CDC10 appeared to be monospecific anti—Scl-70 and anti—Jo-1 sera, respectively, serum AF/CDC4 (anti—U1 small nuclear RNP) recognized the 70-kd band, and serum AF/CDC5 recognized the Sm antigen with its multiple bands. Semiquantitative analyses revealed that AF/CDC5, AF/CDC2, and AF/CDC10 were strongly reactive sera, whereas AF/CDC4 and AF/CDC9 were much weaker and should be used at lower dilutions on Western blots. Conclusion. The AF/CDC ANA reference sera, originally described as reference reagents for indirect immunofluorescence and double immunodiffusion techniques, are also useful for Western blotting. The data presented herein further support the use of these sera for reference purposes.

Antibodies against naked U1RNA can be found in sera from patients with overlap syndromes of systemic lupus erythematosus (SLE) in addition to antibodies directed to the proteins of U1 ribonucleoproteins (U1RNP). We investigated the reactivity of these U1RNA specific autoantibodies with the native U1RNP particle both in vitro and inside the cell. For this purpose a method was developed to purify human autoantibodies directed to specific regions of U1RNA. The antibodies are specifically directed to either stemloop II or stemloop IV of U1RNA and do not crossreact with protein components of U1RNP. Both types of antibody are able to precipitate from cell extracts native U1snRNPs containing most, if not all, protein components. Immunofluorescence patterns indicate that the antigenic sites on the RNA, i.e. the stem of stemloop II and the loop of stemloop IV, are also available after fixation of the cells. Immunoelectron microscopy employing anti-stemloop IV antibodies and purified, complete U1snRNP particles showed that stemloop IV is located within the body of the U1RNP complex, which also comprises the Sm site and the common Sm proteins. The anti-U1RNA autoantibodies described in this paper recognize native U1RNP particles within the cell and can therefore be used as tools to study mechanisms involved in splicing of pre-mRNA.

In recent years, the detection and characterization of (novel) autoantibodies is becoming increasingly important for the early diagnosis of autoimmune diseases. The idiopathic inflammatory myopathies (IIM, also indicated with myositis) are a group of systemic autoimmune disorders that involve inflammation and weakness of skeletal muscles. One of the hallmarks is the infiltration of inflammatory cells in muscle tissues. A number of myositis-specific autoantibodies have been identified and these may be associated with distinct IIM subclasses and clinical symptoms. Here, we review all myositis-specific autoantibodies identified today as well as their target proteins, together with their clinical associations in IIM patients. Post-translational modifications that might be associated with the generation of autoantibodies and the development of the disease are discussed as well. In addition, we describe well established autoantibody detection techniques that are currently being used in diagnostic laboratories, as well as novel multiplexed methods. The latter techniques provide great opportunities for the simultaneous detection of distinct autoantibodies, but may also contribute to the identification of novel autoantibody profiles, which may have additional diagnostic and prognostic value. The ongoing characterization of novel autoantibody specificities emphasizes the complexity of processes involved in the development of such autoimmune diseases.

The literature of the last 4 years confirms that the anti-CCP2 test is a very useful marker for the early and specific diagnosis of rheumatoid arthritis (RA). The anti-CCP2 test is very specific for RA (95-99%) and has sensitivity comparable to that of the rheumatoid factor (70-75%). The antibodies can be detected very early in the disease and can be used as an indicator for the progression and prognosis of RA. In this review, these interesting properties and some future possibilities of this diagnostic test are discussed.

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

Item does not contain fulltext Immunization of mammals with central nervous system (CNS)-derived proteins or peptides induces experimental autoimmune encephalomyelitis (EAE), a disease resembling the human autoimmune disease multiple sclerosis (MS). Both diseases are accompanied by destruction of a part of the of the myelin sheaths, which surround neurites in the CNS. Previous studies in MS have described alterations in the citrullination of myelin basic protein, one of the main protein constituents of the myelin sheath. Here, we show that, also during the development of EAE in mice, hypercitrullination occurs in the areas of the spinal cord that show the highest degree of inflammation and that myelin basic protein and glial fibrillary acidic protein are among the hypercitrullinated proteins. We conclude that hypercitrullination of myelin proteins in the CNS is a common phenomenon in demyelinating disease. Hypercitrullination may cause conformational changes in proteins, so the affected proteins may be involved in the pathogenesis of CNS autoimmune disease by acting as autoreactive T-cell epitopes. This is the first report in which hypercitrullination of CNS proteins in EAE is described and in which proteins other than myelin basic protein are reported to be citrullinated during autoimmune-mediated CNS inflammation.

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Item does not contain fulltext OBJECTIVE: Antibodies directed toward citrullinated proteins (e.g., anti-cyclic citrullinated peptide antibodies) are highly specific for rheumatoid arthritis (RA) and are produced locally at the site of inflammation. Although the presence of citrullinated proteins in rheumatoid synovium has been described in the literature, it is uncertain whether their presence is specific for RA. The present study was undertaken to investigate this. METHODS: The local production of the anti-citrullinated protein antibodies was investigated by comparing the concentration of the antibodies (corrected for the total amount of IgG present) in paired samples of serum and synovial fluid from RA patients. The presence of citrullinated proteins in the synovial tissue was investigated by immunohistochemical analysis of synovial tissue from RA patients and from patients with other arthropathies, using a variety of specific antibodies to citrullinated proteins. RESULTS: In RA patients, anti-citrullinated protein antibodies constituted a 1.4-fold higher proportion of IgG in synovial fluid compared with serum, which is indicative of a local production of the antibodies. Immunohistochemical staining of citrullinated proteins was observed in the lining layer, the sublining layer, and in extravascular fibrin deposits in inflamed synovial tissue from RA as well as non-RA patients. CONCLUSION: The presence of citrullinated proteins in the inflamed synovium is not specific for RA, but rather, it may be an inflammation-associated phenomenon. The high specificity of the anti-citrullinated protein antibodies is, therefore, most likely the result of an abnormal humoral response to these proteins.

Contains fulltext : 58480.pdf (Publisher’s version ) (Closed access) Objective. The functional role of HLA class II molecules in the pathogenesis of rheumatoid arthritis (RA) is unclear. HLA class II molecules are involved in the interaction between T and B lymphocytes required for long-lived B cell responses and generation of high-affinity IgG antibodies. We undertook this study to investigate the relationship between HLA class II gene polymorphisms and RA-specific IgG antibodies against cyclic citrullinated peptides (anti-CCP antibodies). Methods. High-resolution HLA-DR and DQ typing and anti-CCP-2 antibody testing were performed on 268 RA patients from the Early Arthritis Clinic cohort at the Department of Rheumatology of the Leiden University Medical Center. The presence of anti-CCP antibodies was analyzed in carriers of the different DR and DQ alleles. Disease progression was measured over a period of 4 years by scoring radiographs of the hands and feet using the Sharp/van der Heijde method. Results. Carriership of the individual alleles HLA-DRBt*0401, DRB1*1001, DQB1*0302, and DQBI*0501 was associated with the presence of antiCCP antibodies. Carriers of DQ-DR genotypes containing proposed RA susceptibility alleles were significantly more often anti-CCP antibody positive. Carriership of one or two HLA-DRB1 shared epitope (SE) alleles was significantly associated with production of anti-CCP antibodies (odds ratio [OR] 3.3, 95% confidence interval [95% CI] 1.8-6.0 and OR 13.3, 95% CI 4.6-40.4, respectively). An increased rate of joint destruction was observed in SE+, anti-CCP+ patients (mean Sharp score 7.6 points per year) compared with that in SE-, anti-CCP+ patients (2.4 points per year) (P = 0.04), SE+, anti-CCP- patients (1.6 points per year) (P < 0.001), and SE-, anti-CCP- patients (1.6 points per year) (11 < 0.001). Conclusion. HLA class II RA susceptibility alleles are associated with production of anti-CCP antibodies. Moreover, more severe disease progression is found in RA patients with both anti-CCP antibodies and SE alleles.

Item does not contain fulltext OBJECTIVE: To compare the autoantigenicity of the recently described N-terminally elongated PM-Scl-75 protein with that of PM-Scl-100 and the originally defined PM-Scl-75 polypeptide, and to determine its value for analyzing sera from patients with the polymyositis (PM)/scleroderma overlap syndrome. METHODS: Serum samples obtained from patients with the PM/scleroderma overlap syndrome and from patients with several other diseases were analyzed for the presence of autoantibodies reactive with recombinant PM-Scl-100 and PM-Scl-75 (both the original and the longer form) proteins, in an enzyme-linked immunosorbent assay (ELISA). RESULTS: Autoantibodies recognizing the longer PM-Scl-75 protein isoform were detected in 28% of the patients with PM/scleroderma. This percentage is slightly higher than that for PM-Scl-100 (25%) and is significantly higher than that for the previously defined PM-Scl-75 protein (11%). In addition, we identified a significant number of patients who had anti-PM-Scl-75 but not anti-PM-Scl-100 antibodies. This finding contrasts with what has been previously reported for the shorter version of the PM-Scl-75 protein. CONCLUSION: Our data indicate that use of the long PM-Scl-75 isoform in addition to PM-Scl-100 in ELISAs significantly increases the number of patients in whom anti-PM-Scl autoantibodies can be detected.

Using the recombinant La (SS-B) protein or a phosphorylated peptide derived thereof 27 La-specific human recombinant autoantibodies were selected from anti-La-positive systemic lupus erythematosus and systemic sclerosis patient-derived combinatorial phage display antibody libraries. Binding of these anti-La antibodies to various isoforms of the La protein present in normal and apoptotic cell extracts was analysed by Western blotting. Twenty-four of the selected antibodies recognize most, if not all isoforms of La, whereas three are exclusively reactive with the protein phosphorylated at serine-366. Sequence analysis of the selected antibodies showed a restricted spectrum of diversity in their VH germline gene usage. Remarkably, the recombinant antibodies recognizing exclusively the phosphoserine-366-containing isoform of La displayed a spleckled nucleoplasmic staining pattern in immunofluorescence analysis of HeLa and HEp-2 cells. This pattern differed markedly from those obtained with anti-La antibodies recognizing all isoforms of the La protein. Colocalization experiments with marker antibodies for spliceosomal UsnRNPs and RNA polymerase III subunits revealed that the anti-phosphorylated La antibodies stain the same nucleoplasmic speckles as anti-UsnRNP antibodies. In contrast to anti-UsnRNP antibodies the anti-phosphorylated La antibodies did not stain the Cajal bodies. In addition, no colocalization of phosphorylated La with RNA polymerase III was observed. Potential functional implications of the accumulation of phosphorylated La in nucleoplasmic speckles are discussed.

Item does not contain fulltext OBJECTIVE: Antibodies directed to citrulline-containing proteins are highly specific for rheumatoid arthritis (RA) and can be detected in up to 80% of patients with RA. Citrulline is a nonstandard amino acid that can be incorporated into proteins only by posttranslational modification of arginine by peptidylarginine deiminase (PAD) enzymes. The objective of this study was to investigate the presence of anticitrulline antibodies, PAD enzymes, and citrullinated antigens in mouse models of both acute and chronic destructive arthritis: streptococcal cell wall (SCW)-induced arthritis and collagen-induced arthritis (CIA), respectively. METHODS: Synovial tissue biopsy specimens were obtained from naive mice, mice with CIA, and mice with SCW-induced arthritis. The expression of messenger RNA (mRNA) for PAD enzymes was analyzed by reverse transcriptase-polymerase chain reaction; the presence of PAD proteins and their products (citrullinated proteins) was analyzed by Western blotting and by immunolocalization. The presence of anticitrullinated protein antibodies was investigated by an anti-cyclic citrullinated peptide (anti-CCP) enzyme-linked immunosorbent assay (ELISA) and an ELISA using in vitro citrullinated fibrinogen. RESULTS: In both mouse models, PAD type 2 (PAD2) mRNA was present in the synovium but was not translated into PAD2 protein. In contrast, PAD4 mRNA, although absent from healthy synovium, was readily transcribed and translated by polymorphonuclear neutrophils infiltrating the synovial tissue during inflammation. As a consequence, several synovial proteins were subjected to citrullination. One of these proteins was identified as fibrin, which has been reported to be citrullinated also in synovium of patients with RA. Although generation of citrullinated antigens during synovial inflammation in the mice was eminent, no anti-CCP antibodies could be detected. CONCLUSION: Citrullination of synovial antigens is an active process during joint inflammation in both mice and humans, but the induction of autoantibodies directed to these proteins is a more specific phenomenon, detectable only in human RA patients.

Citrullination and the immune response to citrullinated proteins have been fundamental for the early recognition of rheumatoid arthritis by serological tests and a better understanding of its pathophysiology. In the first years after the initial publications, the focus was on the antibodies directed to citrullinated proteins. It is now realized that citrullinating enzymes and citrullinated proteins may have important roles in the maintenance of the inflammatory processes in the joints. There is also accumulating evidence for a direct role of citrullination in tissue destruction in the rheumatoid synovium. Here we will discuss the development and importance of anti-citrullinated protein antibodies in rheumatoid arthritis as well as recent findings implicating citrullination in the pathophysiology of rheumatoid arthritis.

The anti-PM/Scl autoantibodies are known to characterize a subset of autoimmune patients with myositis, scleroderma (Scl), and the PM/Scl overlap syndrome. The major autoantigens that are recognized by anti-PM/Scl autoantibodies are designated PM/Scl-100 and PM/Scl-75. These autoantigens have been reported to associate into a large complex consisting of 11 to 16 proteins and to play a role in ribosome synthesis. Recently, it was discovered that the PM/Scl complex is the human counterpart of the yeast (Saccharomyces cerevisiae) exosome, which is an RNA-processing complex consisting of 11 3' → 5' exoribonucleases. To date, 10 human exosome components have been identified, although only some of these were studied in more detail. In this review, we discuss some recent advances in the characterization of the PM/Scl complex.

An inception cohort of 238 patients having peripheral joint synovitis of less than 12 months duration was evaluated clinically and followed prospectively for 1 year to determine the clinical significance of a number of rheumatoid arthritis (RA) associated autoantibodies. Serum samples collected at the time of the initial evaluation were tested for rheumatoid factor (RF) and antibodies to Sa (anti-Sa), RA-33, (pro)filaggrin [antifilaggrin antibody (AFA)], cyclic citrullinated peptide (anti-CCP), calpastatin, and keratin [antikeratin antibody (AKA)]. RF had a sensitivity of 66% and a specificity of 87% for RA. Anti-Sa, AFA, and anti-CCP all had a specificity of more than 90%, but a sensitivity of less than 50% for this diagnosis. Overall, there was a high degree of correlation between AFA, AKA, anti-Sa or anti-CCP, this being highest between anti-Sa and anti-CCP (odds ratio, 13.3; P < 0.001). Of the 101 patients who were positive for at least one of these four autoantibodies, 57% were positive for only one. Finally, anti-SA identified a subset of predominantly male RA patients with severe, erosive disease. Anti-SA, AFA and anti-CCP are all specific for early RA but, overall, have little additional diagnostic value over RF alone. Although these antibodies may preferentially recognize citrullinated antigens, the modest degree of concordance between them in individual patient sera suggests that it is unlikely a single antigen is involved in generating these responses., Introduction: A spectrum of autoantibodies is now known to be specifically associated with RA. There continues to be uncertainty as to what stage of the disease each of these autoantibodies develop, and whether they are associated with unique clinical features. Aims: To help address these questions, a spectrum of autoantibodies known to be associated with RA in a cohort of patients with early synovitis was evaluated. Methods: An inception cohort of 238 patients having peripheral joint synovitis of less than 12 months duration was evaluated clinicially then followed prospectively for 1 year. Patients were classified as having RA on the basis of fulfilling the 1987 criteria. Serum samples collected at the time of the initial evaluation were tested for anti-Sa and anti-RA-33 using immunoblotting, and to (pro)filaggrin (AFA), anti-CCP, and calpastatin (anti-RA-1) using enzyme-linked immunosorbent assay techniques. AKA were detected using immunoflurescence on human epidermal tissue. RF was tested by nephelometry. HLA-DRB1 alleles were determined using sequence specific primers. Initial and 1 year radiographs were evaluated for the presence of erosions. Results: Of the 238 patients with synovitis of recent onset in the cohort, 106 (45%) met RA criteria, 102 (96%) of whom met the criteria on their initial visit. Diagnoses in the remaining patients included 22 (9%) with reactive arthritis, 14 (6%) with psoriatic arthritis or another form of spondylarthropathy, 11 (5%) with another well-defined rheumatic diagnosis, and 85 (36%) with undifferentiated arthritis. The RA patients were significantly older than the nonRA patients (46 ± 13 versus 39 ± 13; P < 0.001), had higher mean swollen joint count (13.8 ± 9.7 versus 2.3 ± 2.3; P < 0.001), and higher C-reactive protein (CRP) level (1.9 ± 1.9 versus 1.6 ± 2.4; P < 0.01). Table 1 summarizes the prevalence of the various RA associated antibodies in patients diagnosed as having RF-positive (RF+) RA, RF-negative (RF-) RA, and nonRA. Regarding the characteristics of these tests, RF had the highest sensitivity at 66%, and all the other antibodies individually were less than 50% sensitive. AFA, anti-Sa, anti-CCP were greater than 90% specific for RA, while RF and AKA were 80-90% specific, and anti-RA-33 and anti-RA-1 was not specific for this diagnosis. The data further indicate that adding any one of AFA, AKA, anti-Sa, or anti-CCP to RF increases the specificity for RA from 80 to 90%. In the absence of RF, the presence of one or more of these antibodies carried a sensitivity of only 31% for RF- RA, with anti-Sa being the most specific at 98%. Overall, there was a high degree of correlation between AFA, AKA, anti-Sa or anti-CCP, this being highest between anti-Sa and anti-CCP (odds ratio, 13.3; P < 0.001). Despite this high level of correlation, of the 101 patients who were positive for at least one of these four autoantibodies, 57% were positive for only one, suggesting considerable variability in individual reactivity patterns. RA has been shown in multiple populations to be associated with HLA-DRB1 alleles encoding for the shared epitope (SE). In this study, as illustrated in Table 2, the presence of each of these autoantibodies was significantly associated with having two shared epitope alleles, even when only the RA patients were considered. Patients with anti-Sa antibodies were predominantly male (61% versus 28%; P

We have investigated the fate of the RNA components of small ribonucleoprotein particles in apoptotic cells. We show that the cytoplasmic Ro ribonucleoprotein-associated Y RNAs are specifically and rapidly degraded during apoptosis via a caspase-dependent mechanism. This is the first study describing the selective degradation of a specific class of small structural RNA molecules in apoptotic cells. Cleavage and subsequent truncation of Y RNAs was observed upon exposure of cells to a variety of apoptotic stimuli and were found to be inhibited by Bcl-2, zinc, and several caspase inhibitors. These results indicate that apoptotic degradation of Y RNAs is dependent on caspase activation, which suggests that the nucleolytic activity responsible for hY RNA degradation is activated downstream of the caspase cascade. The Y RNA degradation products remain bound by the Ro60 protein and in part also by the La protein, the only two proteins known to be stably associated with intact Ro ribonucleoprotein particles. The size of the Y RNA degradation products is consistent with the protection from degradation of the most highly conserved region of the Y RNAs by the bound Ro60 and La proteins. Our results indicate that the rapid abrogation of the yet unknown function of Y RNAs might be an early step in the systemic deactivation of the dying cell.

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Diagnosis of early rheumatoid arthritis can be significantly hastened by the screening for serological markers such as autoantibodies. This Viewpoint discusses the merits of this new field of serological screening, focusing on the anti-cyclic citrullinated peptide tests and their value as diagnostic tools for rheumatoid arthritis.

Objective. To determine any clinical or genetic markers of differentiation and outcome in a previously described cohort of 46 patients with mixed connective tissue disease (MCTD). Methods. Patients were clinically evaluated, chart notes reviewed, and HLA subtyping and immunology profiles performed where possible. Eleven had died and 7 were lost to followup. Results. MCTD had differentiated into systemic lupus erythematosus in 12 patients and into systemic sclerosis in 13. The latter was associated with HLA-DR5 (P = 0.038), and nondifferentiation was associated with HLA-DR2 or DR4 (P = 0.007). Three HLA-DR4 positive patients had MCTD that evolved into rheumatoid arthritis. Erosive and/or deforming arthritis was associated with HLA-DR1 or DR4 (P = 0.015). HLA-DR3 was associated with interstitial lung fibrosis (P = 0.044) and keratoconjunctivitis sicca (0.001 < P < 0.01). Severe Raynaud's phenomenon predicted higher mortality (0.01 < P < 0.05). Conclusion. We suggest that MCTD is, for most patients, an intermediate stage in a genetically determined progression to a recognized connective tissue disease. Those whose disease remains undifferentiated might be considered a distinct subset.

The La (SS-B) autoimmune antigen is an RNA-binding protein that is present in both nucleus and cytoplasm of eukaryotic cells. The spectrum of RNAs that interact with the La antigen includes species which also bind to the interferon-inducible protein kinase PKR. We have investigated whether the La antigen can regulate the activity of PKR and have observed that both the autophosphorylation of the protein kinase that accompanies its activation by dsRNA and the dsRNA-dependent phosphorylation of the alpha subunit of polypeptide chain initiation factor eIF-2 by PKR are inhibited in the presence of recombinant La antigen. This inhibition is partially relieved at higher concentrations of dsRNA. Once activated by dsRNA the protein kinase activity of PKR is insensitive to the La antigen. We have demonstrated by a filter binding assay that La is a dsRNA binding protein. Furthermore, when recombinant La is incubated with a 900 bp synthetic dsRNA or with naturally occurring reovirus dsRNA it converts these substrates to single-stranded forms. We conclude that the La antigen inhibits the dsRNA-dependent activation of PKR by binding and unwinding dsRNA and that it may therefore play a role in the regulation of this protein kinase in interferon-treated or virus-infected cells.

The U1 snRNP particle contains the following antigenic components: the specific proteins U1-A, U1–70K and U1-C, of which the U1–70K and the Ul-A polypeptides are the major targets of human autoantibodies (reviewed in [1]) Ul snRNA [2, 3].

The presence or absence of antibodies to citrullinated peptides/proteins (ACPA) is an important parameter that helps a clinician set a diagnosis of early rheumatoid arthritis and, hence, initiate treatment. There are several commercial tests available to measure ACPA levels, although it can be difficult to decide what the best test for a given clinical question is. We analyzed literature data in which the diagnostic and other properties of various ACPA tests are compared. The results show that for diagnostic purposes the CCP2 test has the highest specificity, the highest sensitivity in stratified studies and the highest positive predictive value. For the prediction of future joint destruction the CCP2, MCV, and CCP3 tests may be used. The ability to predict the likelihood of not achieving sustained disease-modifying antirheumatic drug-free remission was highest for the CCP2 test. Finally, the levels of anti-CCP2 and anti-CCP3 (and possibly anti-mutated citrullinated vimentin) in rheumatoid arthritis patients are not significantly influenced by TNFalpha blocking agents.

There is increasing evidence that autoantibodies and immune complexes (ICs) contribute to synovitis in rheumatoid arthritis (RA), yet the autoantigens incorporated in ICs in RA remain incompletely characterised.We used the C1q protein to capture ICs from plasma derived from human RA and control patients. Antibodies specific for immunoglobulin were used to detect ICs, and fibrinogen antibodies were used to detect fibrinogen-containing ICs. RA and control plasma were separated by liquid chromatography, and fractions then characterised by ELISA, immunoblotting and mass spectrometry. Immunohistochemical staining was performed on rheumatoid synovial tissue.C1q-immunoassays demonstrated increased levels of IgG (p = 0.01) and IgM (p = 0.0002) ICs in plasma derived from RA patients possessing anti-cyclic citrullinated peptide (CCP+) autoantibodies as compared with healthy controls. About one-half of the anti-CCP+ RA possessed circulating ICs containing fibrinogen (p = 0.0004). Fractionation of whole RA plasma revealed citrullinated fibrinogen in the high molecular weight fractions that contained ICs. Positive correlations were observed between fibrinogen-containing ICs and anti-citrullinated fibrinogen autoantibodies, anti-CCP antibody, rheumatoid factor and certain clinical characteristics. Immunohistochemical staining demonstrated co-localisation of fibrinogen, immunoglobulin and complement component C3 in RA pannus tissue. Mass spectrometry analysis of immune complexes immunoprecipitated from RA pannus tissue lysates demonstrated the presence of citrullinated fibrinogen.Circulating ICs containing citrullinated fibrinogen are present in one-half of anti-CCP+ RA patients, and these ICs co-localise with C3 in the rheumatoid synovium suggesting that they contribute to synovitis in a subset of RA patients.

Modifications occurring on autoantigens during cell death have been proposed to have a role in the initiation of autoimmune diseases. Patients suffering from mixed connective tissue disease (MCTD) produce autoantibodies directed to U1 small nuclear ribonucleoprotein (snRNP), and antibodies against a 70 kDa protein component, the U1-70K (70K) protein, are the most prominent. During apoptosis, 70K is cleaved by caspase-3 to a 40 kDa product, which remains associated with the complex. Autoantibodies preferentially recognizing the apoptotic form of 70K have been described previously, and an apoptosis-specific epitope on 70K has been identified. This study shows that 29 of 53 (54%) MCTD sera preferentially recognize the apoptotic form of 70K over intact 70K. Moreover, we show that antibodies directed to an apoptosis-specific epitope on 70K are more specifically associated with MCTD than other anti-70K antibodies, suggesting that apoptotic 70K is a better antigen for the detection of these antibodies in MCTD patients. Longitudinal analysis of 12 MCTD patients showed in several patients that early sera are relatively enriched with antibodies recognizing an apoptosis-specific epitope, and that the levels of these apoptosis-specific antibodies decrease in time. These findings indicate that the early detection of apoptotic 70K is of considerable interest for anti-U1 snRNP-positive patients.

Antibodies against cyclic citrullinated peptide (CCP) and rheumatoid factors (RFs) have been demonstrated to predate the onset of rheumatoid arthritis (RA) by years. A nested case–control study was performed within the Northern Sweden Health and Disease study cohort to analyse the presence of shared epitope (SE) genes, defined as HLA-DRB1*0404 or DRB1*0401, and of anti-CCP antibodies and RFs in individuals who subsequently developed RA. Patients with RA were identified from among blood donors whose samples had been collected years before the onset of symptoms. Controls matched for age, sex, and date of sampling were selected randomly from the same cohort. The SE genes were identified by polymerase chain reaction sequence-specific primers. Anti-CCP2 antibodies and RFs were determined using enzyme immunoassays. Fifty-nine individuals with RA were identified as blood donors, with a median antedating time of 2.0 years (interquartile range 0.9–3.9 years) before presenting with symptoms of RA. The sensitivity for SE as a diagnostic indicator for RA was 60% and the specificity was 64%. The corresponding figures for anti-CCP antibodies were 37% and 98%, and for RFs, 17–42% and 94%, respectively. In a logistic regression analysis, SE (odds ratio [OR] = 2.35), anti-CCP antibodies (OR = 15.9), and IgA-RF (OR = 6.8) significantly predicted RA. In a combination model analysis, anti-CCP antibodies combined with SE had the highest OR (66.8, 95% confidence interval 8.3–539.4) in predicting RA, compared with anti-CCP antibodies without SE (OR = 25.01, 95% confidence interval 2.8–222.2) or SE without anti-CCP antibodies (OR = 1.9, 95% confidence interval 0.9–4.2). This study showed that the presence of anti-CCP antibodies together with SE gene carriage is associated with a very high relative risk for future development of RA.

Antibodies directed to citrullinated proteins (anti-cyclic citrullinated peptide) are highly specific for rheumatoid arthritis (RA). Recent data suggest that the antibodies may be involved in the disease process of RA and that several RA-associated genetic factors might be functionally linked to RA via modulation of the production of anti-cyclic citrullinated peptide antibodies or citrullinated antigens.

Antibodies directed to the Sa antigen are highly specific for rheumatoid arthritis (RA) and can be detected in approximately 40% of RA sera. The antigen, a doublet of protein bands of about 50 kDa, is present in placenta and in RA synovial tissue. Although it has been stated that the Sa antigen is citrullinated vimentin, experimental proof for this claim has never been published. In this study, we investigated the precise nature of the antigen. Peptide sequences that were obtained from highly purified Sa antigen were unique to vimentin. Recombinant vimentin, however, was not recognized by anti-Sa reference sera. In vivo, vimentin is subjected to various post-translational modifications, including citrullination. Since antibodies to citrullinated proteins are known to be highly specific for RA, we investigated whether Sa is citrullinated and found that Sa indeed is citrullinated vimentin. Anti-Sa antibodies thus belong to the family of anticitrullinated protein/peptide antibodies. The presence of the Sa antigen in RA synovial tissue, and the recent observation that vimentin is citrullinated in dying human macrophages, make citrullinated vimentin an interesting candidate autoantigen in RA and may provide new insights into the potential role of citrullinated synovial antigens and the antibodies directed to them in the pathophysiology of RA.

The presence of anti-α-fodrin autoantibodies has been reported to be a highly specific and sensitive test for the diagnosis of Sjogren's syndrome (SjS). We looked (in Nijmegen) for anti-α-fodrin, anti-Ro60, and anti-La autoantibodies in a cohort of 51 patients with rheumatic diseases (primary SjS [21], secondary SjS [6], rheumatoid arthritis [RA] [12], systemic lupus erythematosus [SLE] [6], and scleroderma [6]) and in 28 healthy subjects, using ELISA, immunoblotting, and immunoprecipitation. The same samples were analyzed with an alternative anti-α-fodrin ELISA in Hanover. The Nijmegen ELISA of the sera from primary SjS showed sensitivities of 43% and 48% for IgA- and IgG-type anti-α-fodrin antibodies, respectively. The Hanover ELISA showed sensitivities of 38% and 10% for IgA- and IgG-type anti-α-fodrin antibodies, respectively. The ELISAs for α-fodrin showed six (Nijmegen) and four (Hanover) anti-α-fodrin-positive RA sera. IgA and IgG anti-fodrin antibodies were also present in four patients with secondary SjS. The sensitivities of Ro60 and La-antibodies in the Nijmegen ELISA were 67% and 62%, respectively. Unlike anti-α-fodrin antibodies, all anti-Ro60 and anti-La positive sera could be confirmed by immunoblotting or RNA immunoprecipitation. Thus, anti-Ro and anti-La autoantibodies were more sensitive than anti-α-fodrin autoantibodies in ELISA and were more frequently confirmed by other techniques. Anti-La antibodies appear to be more disease-specific than anti-α-fodrin antibodies, which are also found in RA sera. Therefore, the measurement of anti-α-fodrin autoantibodies does not add much to the diagnosis of Sjogren's syndrome.

The diagnosis of rheumatoid arthritis (RA) is primarily based on clinical symptoms, so it is often difficult to diagnose RA in very early stages of the disease. A disease-specific autoantibody that could be used as a serological marker would therefore be very useful. Most autoimmune diseases are characterized by a polyclonal B-cell response targeting multiple autoantigens. These immune responses are often not specific for a single disease. In this review, the most important autoantibody/autoantigen systems associated with RA are described and their utility as a diagnostic and prognostic tool, including their specificity, sensitivity and practical application, is discussed. We conclude that, at present, the antibody response directed to citrullinated antigens has the most valuable diagnostic and prognostic potential for RA.

The autoantigenic polymyositis/scleroderma (PM/Scl) complex was recently shown to be the human homologue of the yeast exosome, which is an RNA-processing complex. Our aim was to assess whether, in addition to targeting the known autoantigens PM/Scl-100 and PM/Scl-75, autoantibodies also target recently identified components of the PM/Scl complex. The prevalence of autoantibodies directed to six novel human exosome components (hRrp4p, hRrp40p, hRrp41p, hRrp42p, hRrp46p, hCsl4p) was determined in sera from patients with idiopathic inflammatory myopathy (n = 48), scleroderma (n = 11), or the PM/Scl overlap syndrome (n = 10). The sera were analyzed by enzyme-linked immunosorbent assays and western blotting using the affinity-purified recombinant proteins. Our results show that each human exosome component is recognized by autoantibodies. The hRrp4p and hRrp42p components were most frequently targeted. The presence of autoantibodies directed to the novel components of the human exosome was correlated with the presence of the anti-PM/Scl-100 autoantibody in the sera of patients with idiopathic inflammatory myopathy (IIM), as was previously found for the anti-PM/Scl-75 autoantibody. Other clear associations between autoantibody activities were not found. These results further support the conception that the autoimmune response may initially be directed to PM/Scl-100, whereas intermolecular epitope spreading may have caused the autoantibody response directed to the associated components.

The induction of autoantibodies to U1 small nuclear ribonucleoprotein (U1 snRNP) complexes is not well understood. We present evidence that healthy individuals with cytomegalovirus (CMV) infection have an increased frequency and quantity of antibodies to ribonucleoprotein, directed primarily against the U1-70k protein. A significant association between the presence of antibodies to CMV and antibodies to the total RNP targeted by the immune response to the spliceosome (to both the Sm and RNP; Sm/RNP) was found for patients with systemic lupus erythematosus (SLE) but not those with mixed connective-tissue disease. CMV thus may play a role in inducing autoimmune responses in a subset of patients with systemic lupus erythematosus.