Anti-cyclic citrullinated peptide positivity in non-rheumatoid arthritis disease samples: citrulline-dependent or not?

BACKGROUND: Antibodies directed against citrullinated proteins (eg anti-cyclic citrullinated peptide (CCP)) have excellent diagnostic and good prognostic potential for rheumatoid arthritis. Type 1 autoimmune hepatitis (AIH-1) is a chronic liver disease characterised by a variety of serum autoantibodies. Recently, in a large group of patients with AIH-1 without clear rheumatoid arthritis overlap, a relatively high percentage (9%) of anti-CCP2 positivity was scored. OBJECTIVES: To characterise the citrulline-dependence of the observed anti-CCP2 positivity in AIH-1 sera as well as in other groups of patients without rheumatoid arthritis (mainly rheumatic diseases). METHODS: Serum samples of 57 patients with AIH-1 and 66 patients without rheumatoid arthritis, most of them reported as anti-CCP positive, were tested for citrulline-specific reactivity with a second generation anti-CCP kit, with the citrullinated and the corresponding non-citrullinated (arginine-containing) antigen. A subset of AIH-1 sera was also tested with a CCP1 ELISA (and arginine control). RESULTS: The anti-CCP2 reactivity of most non-rheumatoid arthritis rheumatic diseases samples (87-93%) was citrulline-specific, whereas a relatively high percentage of AIH-1 samples (42-50%) turned out to be reactive in a citrulline-independent manner. The use of citrullinated and non-citrullinated CCP1 peptides confirmed a high occurrence of citrulline-independent reactivity in AIH-1 samples. CONCLUSIONS: In rheumatoid arthritis and most non-rheumatoid arthritis rheumatologic disease sera, anti-CCP positivity is citrulline-dependent. However in some patients, particularly patients with AIH-1, citrulline-independent reactivity in the anti-CCP2 test can occur. A positive CCP test in a non-rheumatic disease (eg liver disease) should therefore be interpreted with care, and preferably followed by a control ELISA with a non-citrullinated antigen.

Anti-signal recognition particle autoantibodies: marker of a necrotising myopathy.

OBJECTIVE: To elucidate the clinical importance of the anti-signal recognition particle (SRP) autoantibody in patients with myositis. METHODS: Retrospective systematic assessment of the clinical, laboratory and histological characteristics of 23 anti-SRP-positive patients from six European centres. Data were compared with a large group of anti-SRP-negative patients with myositis published previously. RESULTS: Clinically, patients with anti-SRP autoantibodies often had a severe symmetric proximal muscle weakness resulting in marked disability, dysphagia and highly elevated levels of serum creatine kinase. Three patients had typical dermatomyositis rashes. The disease was associated with the occurrence of extramuscular signs and symptoms including interstitial lung disease. No association was found with an increased risk of cardiac involvement, and the disease carried a reasonably favourable prognosis with most patients responding to treatment. None of the patients had the typical histological features of myositis. Most muscle biopsy specimens showed the presence of necrotic muscle fibres and no inflammatory infiltrates. CONCLUSIONS: Anti-SRP autoantibodies are associated with a syndrome of a necrotising myopathy in the spectrum of immune-mediated myopathies that differs from typical polymyositis. Further studies are needed to elucidate the pathogenesis and to clarify the role of the anti-SRP autoantibodies in this unique disease.

Long-term outcome in polymyositis and dermatomyositis.

BACKGROUND: Although polymyositis and dermatomyositis are regarded as treatable disorders, prognosis is not well known, as in the literature long-term outcome and prognostic factors vary widely. AIM: To analyse the prognostic outcome factors in polymyositis and adult dermatomyositis. METHODS: We determined mortality, clinical outcome (muscle strength, disability, persistent use of drugs and quality of life) and disease course and analysed prognostic outcome factors. RESULTS: Disease-related death occurred in at least 10% of the patients, mainly because of associated cancer and pulmonary complications. Re-examination of 110 patients after a median follow-up of 5 years showed that 20% remained in remission and were off drugs, whereas 80% had a polycyclic or chronic continuous course. The cumulative risk of incident connective tissue disorder in patients with myositis was significantly increased. 65% of the patients had normal strength at follow-up, 34% had no or slight disability, and 16% had normal physical sickness impact profile scores. Muscle weakness was associated with higher age (odds ratio (OR) 3.6; 95% confidence interval (CI) 1.3 to 10.3). Disability was associated with male sex (OR 3.1; 95% CI 1.2 to 7.9). 41% of the patients with a favourable clinical outcome were still using drugs. Jo-1 antibodies predicted the persistent use of drugs (OR 4.4, 95% CI 1.3 to 15.0). CONCLUSIONS: Dermatomyositis and polymyositis are serious diseases with a disease-related mortality of at least 10%. In the long term, myositis has a major effect on perceived disability and quality of life, despite the regained muscle strength.

Clinical characteristics of patients with myositis and autoantibodies to different fragments of the Mi-2 beta antigen.

OBJECTIVES: To assess the clinical implications of autoantibodies directed against different parts of the Mi-2 beta autoantigen in patients with myositis. METHODS: A systematic assessment of the clinical, laboratory, and histological characteristics of 48 anti-Mi-2 positive patients from six European centres was made. Anti-Mi-2 autoantibodies were determined with an ELISA using four overlapping fragments spanning the entire amino acid sequence of the autoantigen. Data were compared with results for a large group of anti-Mi-2 negative patients with myositis published previously. RESULTS: Anti-Mi-2 autoantibodies were found in dermatomyositis, polymyositis, and inclusion body myositis. In general, myositis with anti-Mi-2 autoantibodies was characterised by relatively mild disease, sometimes accompanied by extra-muscular symptoms, including arthralgia, arthritis, Raynaud's phenomenon, and interstitial lung disease. Cardiac disease was not seen, and treatment response was fair. No differences were found between patients with autoantibodies to different fragments of the Mi-2 beta antigen, except for a potentially increased risk of cancer in patients with antibodies directed to the N-terminal fragment of the autoantigen. CONCLUSIONS: Anti-Mi-2 autoantibodies are not a marker of a specific subtype of myositis. No significant differences between patients with autoantibodies to different fragments of the Mi-2 beta autoantigen are found, with the possible exception of an increased risk of cancer in patients with antibodies to the N-terminal fragment.

High specificity of myositis specific autoantibodies for myositis compared with other neuromuscular disorders.

Myositis specific autoantibodies (MSAs) are proven to be specific for myositis compared with other inflammatory connective tissue diseases. Their specificity compared, however, with other neuromuscular disorders, which are included in the differential diagnosis of patients in whom the diagnosis myositis is under consideration, is unknown. We prospectively screened sera from 107 patients with various neuromuscular disorders for the most common MSAs and compared the results with the findings in a group of 97 myositis patients, published previously. Special attention was paid to patients with facioscapulohumeral muscular dystrophy (FSHD), an autosomal dominant muscle disease with marked inflammation in skeletal muscle tissue. Only one patient in the neuromuscular disorders group tested positive for an MSA, compared with 41 in the myositis group, resulting in a specificity of 99%. None of the FSHD patients tested positive. We conclude that the tested MSAs are highly specific for myositis and that they are not merely associated with muscle inflammation.

Autoantibodies to cyclic citrullinated peptides predict progression to rheumatoid arthritis in patients with undifferentiated arthritis: a prospective cohort study.

OBJECTIVE: Rheumatoid arthritis (RA) is a common, severe, chronic inflammatory joint disease. Since the disease may initially be indistinguishable from other forms of arthritis, early diagnosis can be difficult. Autoantibodies seen in RA can be detected years before clinical symptoms develop. In an inception cohort of patients with recent-onset arthritis, we undertook this study to assess the predictive value of RA-specific autoantibodies to cyclic citrullinated peptides (CCPs) in patients with undifferentiated arthritis (UA). METHODS: Anti-CCP2 antibody tests were performed at baseline in 936 consecutive, newly referred patients with recent-onset arthritis. Patients who could not be properly classified 2 weeks after inclusion were categorized as having UA. Patients with UA were followed up for 3 years and evaluated for progression of their disease to RA as defined by the American College of Rheumatology (ACR) 1987 revised criteria. RESULTS: Three hundred eighteen of 936 patients with recent-onset arthritis were classified as having UA and were available for analysis. After 3 years of followup, 127 of 318 UA patients (40%) had been classified as having RA. RA had developed in 63 of 249 patients (25%) with a negative anti-CCP test and in 64 of 69 patients (93%) with a positive anti-CCP test (odds ratio 37.8 [95% confidence interval 13.8-111.9]). Multivariate analysis of the presence of anti-CCP antibodies and parameters from the ACR criteria identified polyarthritis, symmetric arthritis, erosions on radiographs, and anti-CCP antibodies as significant predictors of RA. CONCLUSION: Testing for anti-CCP antibodies in UA allows accurate prediction of a substantial number of patients who will fulfill the ACR criteria for RA.

Expression and activity of citrullinating peptidylarginine deiminase enzymes in monocytes and macrophages.

BACKGROUND: Antibodies directed to proteins containing the non-standard amino acid citrulline, are extremely specific for rheumatoid arthritis (RA). Peptidylcitrulline can be generated by post-translational conversion of arginine residues. This process, citrullination, is catalysed by a group of calcium dependent peptidylarginine deiminase (PAD) enzymes. OBJECTIVE: To investigate the expression and activity of four isotypes of PAD in peripheral blood and synovial fluid cells of patients with RA. RESULTS: The data presented here show that citrullination of proteins by PAD enzymes is a process regulated at three levels: transcription-in peripheral blood PAD2 and PAD4 mRNAs are expressed predominantly in monocytes; PAD4 mRNA is not detectable in macrophages, translation-translation of PAD2 mRNA is subject to differentiation stage-specific regulation by its 3' UTR, and activation-the PAD proteins are only activated when sufficient Ca(2+) is available. Such high Ca(2+) concentrations are normally not present in living cells. In macrophages, which are abundant in the inflamed RA synovium, vimentin is specifically citrullinated after Ca(2+) influx. CONCLUSION: PAD2 and PAD4 are the most likely candidate PAD isotypes for the citrullination of synovial proteins in RA. Our results indicate that citrullinated vimentin is a candidate autoantigen in RA.

Polymyositis: an overdiagnosed entity.

BACKGROUND: According to widely used criteria (Bohan and Peter criteria, 1975), dermatomyositis (DM) is differentiated from polymyositis (PM) only by skin changes. More recent criteria also include histopathologic characteristics enabling the distinction between PM and DM and the differentiation of sporadic inclusion body myositis (s-IBM) from PM. The authors investigated the applicability of diagnostic features for diagnosing PM and DM. METHODS: The authors performed a retrospective follow-up study of 165 patients with 1) a previous diagnosis of myositis; 2) subacute onset of symmetric, proximal weakness; and 3) an evaluation between 1977 and 1998 excluding other neuromuscular disorders. RESULTS: The diagnoses at initial evaluation based on clinical, laboratory, and histopathologic criteria were PM, 9 (5%); DM, 59 (36%; 54 isolated, 3 with associated connective tissue disease [CTD], 2 with associated malignancy); unspecified myositis (perimysial/perivascular infiltrates, no PM or DM), 65 (39%; 38 isolated myositis, 26 with associated CTD, 1 with malignancy); and possible myositis (necrotizing myopathy, no inflammatory infiltrates), 32 (19%; 29 isolated myositis, 3 with associated CTD). At follow-up evaluation, five of the nine patients with PM had typical s-IBM features. None of the remaining four patients complied with the assumed typical signs of PM. Ten of the 38 patients with isolated unspecified myositis had been diagnosed with a CTD. CONCLUSIONS: Polymyositis is an overdiagnosed entity. At evaluation, more than half the patients with autoimmune myositis cannot be specifically diagnosed with polymyositis or dermatomyositis. A quarter of patients with isolated unspecified myositis subsequently developed connective tissue disease.

[The anti-synthetase syndrome: muscle disease and multisystem disorder at the same time]. / Het antisynthetasesyndroom: spierziekte en tevens multisysteemaandoening.

In three women, aged 60, 45 and 38 years, who presented with exertional dyspnoea (due to lung fibrosis) and Raynaud's phenomenon, dermatomyopathy and Raynaud's phenomenon, and symmetrical arthralgia and myalgia, respectively, the anti-synthetase syndrome was diagnosed. The anti-synthetase syndrome consists of myositis, idiopathic interstitial lung disease, polyarthritis and Raynaud's phenomenon. The syndrome is characterised by the presence of autoantibodies directed against aminoacyl-tRNA synthetases. A thorough knowledge of this syndrome is required to anticipate manifestations of the disease, which can sometimes be masked and are not always part of the treating physician's field of specialty. The patients were treated with immunosuppressive therapy (azathioprine, prednisone, methotrexate) and recovered considerably.

Modifications of arginines and their role in autoimmunity.

Posttranslational modifications of proteins often perform a key role in the biological functioning of proteins. Some of these modifications also change the immunogenicity of proteins and peptides and create 'self'-antigens which might induce autoimmune responses. In particular modifications of arginines within a defined protein context can lead to a specific B-cell immune response. This review discusses the generation of such modifications and their relevance for autoimmunity.

Recombinant anti-P protein autoantibodies isolated from a human autoimmune library: reactivity, specificity and epitope recognition.

The ribosomal P proteins are specific and important autoantigens in patients affected by systemic lupus erythematosus. In this study, we describe for the first time the selection and characterization of recombinant human monoclonal anti-P protein (auto)-antibody fragments from an autoimmune patient-derived phage display antibody library. The selected recombinant anti-P antibodies specifically recognize the P proteins in immunofluorescence assays on HEp-2 cells and in immunoblotting assays, and they immunoprecipitate the P proteins under native conditions. Using both anti-P-positive patient sera and the selected recombinant anti-P antibodies, the immunodominant epitope was determined and shown to be located at the C-terminal end of the P proteins (amino acids 111-115). Inhibition of in vitro protein translation demonstrated that interaction of the monoclonal patient-derived anti-P antibodies with their native epitope functionally inhibits the activity of the P proteins on the ribosome, confirming the notion that patient autoantibodies are often directed to the functional centre of their autoantigenic target.

Caspase-mediated cleavage of the U snRNP-associated Sm-F protein during apoptosis.

Recent studies have implicated the dying cell as a potential reservoir of modified autoantigens that might initiate and drive systemic autoimmunity in susceptible hosts. The spliceosomal Sm proteins are recognized by the so-called anti-Sm autoantibodies, an antibody population found exclusively in patients suffering from systemic lupus erythematosus. We have studied the effects of apoptosis on the Sm proteins and demonstrate that one of the Sm proteins, the Sm-F protein, is proteolytically cleaved in apoptotic cells. Cleavage of the Sm-F protein generates a 9-kDa apoptotic fragment, which remains associated with the U snRNP complexes in apoptotic cells. Sm-F cleavage is dependent on caspase activation and the cleavage site has been located near the C-terminus, EEED(81) downward arrow G. Use of different caspase inhibitors suggests that besides caspase-8 other caspases are implicated in Sm-F cleavage. A C-terminally truncated mutant of the Sm-F protein, representing the modified form of the protein, is capable of forming an Sm E-F-G complex in vitro that is recognized by many anti-Sm patient sera.

[Early diagnosis of rheumatoid arthritis with a test based upon a specific antigen: cyclic citrullinated peptide]. / Vroegdiagnostiek van reumatoïde artritis met een test op basis van een specifiek antigeen: cyclisch gecitrullineerd peptide.

In patients with rheumatoid arthritis (RA), joint erosions occur at a very early stage of the disease before clinical symptoms can be detected. Early treatment with currently available antirheumatic drugs may stop or delay the development of such erosions. A simple and specific diagnostic test is needed for treatment to be initiated at an early stage. The specificity of the routinely used rheumatoid factor (RF) test is too low for that purpose. A novel autoantibody, directed to citrullinated antigens in the synovium, seems to provide a new starting point. These citrullinated autoantigens (e.g. fibrin) are specifically present in inflamed synovia and the antibodies for these are locally produced. The autoantibodies can be detected in the blood of the patients with RA years before the first clinical signs are manifest, and high titres appear to correlate strongly with erosive disease. The test for cyclic citrullinated peptide, which has recently become available, has a specificity of 98-99% and a sensitivity of 75-80%.

Autoantibodies against small nucleolar ribonucleoprotein complexes and their clinical associations.

Sera from patients suffering from systemic autoimmune diseases such as systemic lupus erythematosus (SLE) and systemic sclerosis (SSc) have been shown to contain reactivities to nuclear components. Autoantibodies specifically targeting nucleolar antigens are found most frequently in patients suffering from SSc or SSc overlap syndromes. We determined the prevalence and clinical significance of autoantibodies directed to nucleolar RNA-protein complexes, the so-called small nucleolar ribonucleoprotein complexes (snoRNPs). A total of 172 patient sera with antinucleolar antibodies were analysed by immunoprecipitation. From 100 of these patients clinical information was obtained by chart review. Autoantibodies directed to snoRNPs were detected not only in patients suffering from SSc and primary Raynaud's phenomenon (RP), but also in patients suffering from SLE, rheumatoid arthritis (RA) and myositis (PM/DM). Antibodies against box C/D small snoRNPs can be subdivided in antifibrillarin positive and antifibrillarin negative reactivity. Antifibrillarin-positive patient sera were associated with a poor prognosis in comparison with antifibrillarin negative (reactivity with U3 or U8 snoRNP only) patient sera. Anti-Th/To autoantibodies were associated with SSc, primary RP and SLE and were found predominantly in patients suffering from decreased co-diffusion and oesophagus motility and xerophthalmia. For the first time autoantibodies that recognize box H/ACA snoRNPs are described, identifying this class of snoRNPs as a novel autoantigenic activity. Taken together, our data show that antinucleolar patient sera directed to small nucleolar ribonucleoprotein complexes are found frequently in other diseases than SSc and that categorization of diagnoses and clinical manifestations based on autoantibody profiles seems particularly informative in patient sera recognizing box C/D snoRNPs.

Clinical and serological characteristics of 125 Dutch myositis patients. Myositis specific autoantibodies aid in the differential diagnosis of the idiopathic inflammatory myopathies.

The idiopathic inflammatory myopathies (IIM) are a heterogeneous group of systemic diseases that include the familiar disease entities of dermatomyositis (DM), polymyositis (PM), and inclusion body myositis (IBM). A subset of patients has unique autoantibodies which are specific for IIM (myositis specific autoantibodies; MSAs). We studied the clinical and serological characteristics of IIM in 125 Dutch patients. Sera were analysed by immunoblotting, enzyme-linked immunosorbent assay, and immunoprecipitation. The most frequently encountered MSA was the anti-Jo-1 autoantibody (20%), followed by anti-tRNAHis (6%), anti-Mi-2 (6%), and anti-SRP (4%). The presence of certain MSAs was clearly associated with specific clinical characteristics. Anti-Jo-1 and anti-tRNAHis were associated with the anti-synthetase syndrome, anti-SRP with PM with severe myalgia and arthralgia and a moderate response to immunosuppressive treatment. A novel finding was the presence of anti-Mi-2, not only in DM, but also in PM. MSAs were frequently present in DM/PM sera, but were hardly ever detected in the sera of IBM patients. The few IBM patients with MSAs demonstrated a significant response to immunosuppressive treatment. It can be concluded that MSAs define specific clinical syndromes within the spectrum of IIM and that they can assist in the differential diagnosis and treatment plan of these enigmatic disorders by virtually excluding IBM by their presence, and by potentially identifying a subgroup of steroid-responsive IBM patients.

Myositis-specific autoantibodies: overview and recent developments.

Myositis-specific autoantibodies (MSAs) are found in almost half the patients with an idiopathic inflammatory myopathy (IIM). Several clinical and epidemiological studies have suggested that MSAs are associated with specific clinical characteristics. Some of these associations are well-defined and are of clinical significance ( eg, anti-Jo-1 and the anti-synthetase syndrome), others are less well established and can cause unnecessary anxiety for both patients and physicians ( eg, anti-SRP and cardiac involvement). In this review, an overview is given of the various MSAs, their biochemical background, their clinical usefulness, and the promises they hold for a better understanding of IIM.