Epitope mapping with synthetic peptides of 52-kD SSA/Ro protein reveals heterogeneous antibody profiles in human autoimmune sera.

The reactivity of autoantibodies present in the sera of 489 patients with Sjögren's syndrome (SS), systemic lupus erythematosus (SLE) and other autoimmune diseases was investigated by ELISA using recombinant 52-kD SSA/Ro protein (rRo52) and 39 overlapping synthetic peptides representing the entire sequence of Ro52. We report that IgG antibodies reacting with rRo52 were present in the sera of a large number of patients with SS (67% of patients with primary SS and 46% of patients with SS associated with SLE), whereas they were less frequent (10-25%) in SLE, rheumatoid arthritis (RA), juvenile chronic arthritis (JCA) and mixed connective tissue disease (MCTD), and absent in scleroderma. Among the 39 peptides tested, five were recognized by sera from 30-65% of patients with SS, namely peptides representing residues 2-11, 107-122, 107-126, 277-292 and 365-382. Patients with JCA had raised levels of IgG antibodies reacting with peptides 2-11 and 365-382, and 51% of patients with MCTD had raised levels of IgG antibodies reacting with peptide 365-382. None of the five peptides was recognized by more than 20% of sera from patients with SLE and RA. Interestingly, and of importance in the field of diagnostic tests based on peptides, the reactivity of antibodies to the Ro52 synthetic peptides varied greatly according to the origin of sera. Inhibition experiments using either patients' sera or antibodies induced in rabbits against Ro52 peptides showed that the four domains 2-11, 107-122, 277-292 and 365-382 are accessible on the surface of the Ro52 protein. These regions may thus be involved in the induction of specific antibodies in autoimmune patients.     

Clinical significance of anti-RNP and anti-Sm autoantibodies as determined by immunoblotting and immunoprecipitation in sera from patients with connective tissue diseases.

Antibodies to Sm and RNP antigens have been detected by immunoblotting and immunoprecipitation of small nuclear ribonucleoproteins in 168 sera from patients with connective tissue diseases previously characterized by immunodiffusion. Anti-RNP and anti-Sm antibodies immunoprecipitated U1 and U1-U6 snRNA respectively. By immunoblotting anti-Sm reacted with B-B' and D polypeptides and we have distinguished two types of anti-RNP sera: 1) 'full spectrum' anti-RNP sera reacted with the 68 kD, A, C and B-B' polypeptides; 2) 'partially reactive' anti-RNP sera reacted with various combinations of these polypeptides but not the four of them. A strong specificity of anti-Sm antibodies for systemic lupus erythematosus (SLE) was found with all three methods but immunoblotting was more sensitive and detected anti-Sm in 76% of SLE sera. Sera containing a high titer of 'full spectrum' anti-RNP without anti-Sm activity were only detected in mixed connective tissue disease (MCTD) whereas anti-68 kD antibodies alone seemed to be less specific. This strong association between 'full spectrum' anti-RNP antibodies and MCTD supports the hypothesis that MCTD is a distinct clinical entity associated with a specific serologic marker.     

Antibody responses against polypeptide components of Epstein-Barr virus-induced early diffuse antigen in patients with connective tissue diseases

The specific humoral response against polypeptide components of Epstein-Barr virus (EBV), the induced early diffuse antigen (EA-D), in patients with connective tissue diseases, including systemic lupus erythematosus (SLE) and mixed connective tissue disease (MCTD), was investigated by using the immunoblotting technique. The EA(D)-positive sera from patients with infectious mononucleosis (IM), nasopharyngeal carcinoma (NPC), immunocompromised patients (renal transplant recipients and patients with AIDS) as well as the EA(D)-negative sera from patients with Burkitt's lymphoma and from clinically healthy subjects served as controls. Seven major antigenic polypeptides with molecular weights of 33 kDa, 35 kDa, 52 kDa, 54 kDa, 56 kDa, 58 kDa, and 134 kDa were detected reproducibly by the EA(D)-positive reference sera and, in particular, by each of the NPC sera tested. The EA(D)-positive sera from the other groups showed various combinations of detection patterns and few samples reacted with all the major EA(D) polypeptides. Seventy-three percent of sera from SLE and 47% of sera from MCTD were found to react with EA(D). Sixty-one percent of sera from SLE vs. 5% from MCTD detected all the EA(D) polypeptides. These results could either reflect perturbations of the immune response linked to the autoimmune disease or suggest a possible pathogenic role of EBV.     

Purification of the Sm nuclear autoantigen. Detection and clinical significance of IgM antibody

Sm antigen from rabbit thymus acetone powder was purified using a combination of ammonium sulphate precipitation, DEAE-Sephacel and hydroxyapatite chromatography. This preparation was devoid of previously identified nuclear antigens including ribonucleoprotein (U1-RNP), proliferating cell nuclear antigen (PCNA), Sjögren''s syndrome antigen A (SS-A/Ro), Sjögren''s syndrome antigen B (SS-B/La), Sjögren''s lupus antigen (SL), scleroderma antigen 70 (Scl-70), DNA and histones. The purified material was used in an enzyme linked immunosorbent assay (ELISA) to detect anti-Sm antibody. All sera with precipitating Sm antibody detected by immunodiffusion gave reactions in ELISA greater than 0.40 OD405 and contained predominantly IgG anti-Sm antibody. Of 112 sera which did not have anti-Sm by immunodiffusion there were five which gave reactions greater than 0.40 OD405. Four of these five sera contained only IgM antibody and the fifth contained both IgM and IgG. Of these five, one came from a ''normal'' control who had a positive anti-nuclear antibody (ANA), facial rash and diabetes, two were from patients with systemic lupus erythematosus (SLE) and two were from patients with mixed connective tissue disease (MCTD). These findings demonstrate that there are patients whose anti-Sm response may be restricted to IgM and in some of these patients the clinical presentation may be different from that of classical SLE.     

Sm抗原纯化及ELISA检测Sm抗体的初步研究

从小牛胸腺中盐析出来的Sm/RNP提取物经DEAE Bio-Ge1 A层析即为Sm抗原。在PAGE检测时Sm抗原在BSA之前有几条染色带。 血清学研究显示,Sm抗原仅与Sm阳性和Sm/RNP阳性血清发生反应,不与RNP阳性血清发生反应。经Sm抗原吸收后,Sm阳性和Sm/RNP阳性血清与Sm抗原的反应降低至接近正常人水平,而上述血清与RNP抗原的反应设有明显降低。结果表明,Sm与RNP已完全分开。ELISA方法检测Sm抗体有10/18的SLE和2/4MCTD是阳性,在14例RA、硬皮病和其它疾病中为阴性。     

Detection of autoantibodies in a quantitative immunoassay using recombinant ribonucleoprotein antigens.

A human cDNA expression library was screened with anti-ribonucleoprotein (RNP) antibodies from patients with connective tissue diseases. Three cDNA clones were isolated encoding 70 kD, A and B" ribonucleoprotein autoantigens which were expressed as beta-galactosidase fusion proteins. Antigens were purified and used to develop sensitive ELISAs suitable for the routine screening of large series of sera from patients with connective tissue diseases. More than 400 sera were tested both by ELISA and by immunoblotting. The ELISA was found to be at least as sensitive as immunoblotting and very specific. Anti-70 kD antibodies were found in 94% of patients with mixed connective tissue disease (MCTD), in 4% of patients with other connective tissue diseases but not in normal controls. Furthermore, the use of recombinant 70 kD antigen enabled us to discriminate between anti-70 kD antibodies present in anti-Sm and in anti-(U1) RNP sera. Recombinant A antigen contained at least two autoantibody-reactive sites; one unique for the A protein and another cross-reactive with anti-B" antibodies. Antibodies reactive with the unique site were found in 83% of MCTD patients, in 4% of patients with other connective tissue diseases and not in normal controls. Antibodies against the cross-reactive B" epitope present on A and B" recombinant antigens, were found in high titres in a small percentage of patients with systemic lupus erythematosus (SLE, 5%) and rheumatoid arthritis (RA, 2%).     

Elevated immunoglobulin G antibodies to the proline-rich amino-terminal region of Epstein-Barr virus nuclear antigen-2 in sera from patients with systemic connective tissue diseases and from a subgroup of Sjögren's syndrome patients with pulmonary involvements

Associations of Epstein-Barr virus (EBV) and autoimmune diseases have been hypothesized. We have analysed IgG antibodies to EBV nuclear antigen (EBNA)-2 in sera from Japanese patients with autoimmune systemic connective tissue diseases (CTD), exemplified by systemic lupus erythematosus (SLE), primary Sjogren's syndrome (SS), rheumatoid arthritis (RA), systemic sclerosis (SSc) and secondary SS (classical CTDs complicated with SS). An enzyme-linked immunosorbent assay (ELISA) which uses glutathione-S-transferase polypeptides fused to EBV nuclear antigen (EBNA)-2 and EBNA-1 was developed. Ratios of IgG antibody reactivity to whole IgG concentrations of sera were calculated to normalize EBNA-2 and EBNA-1 antibody levels to the hypergammaglobulinaemia that occurs in CTD. The ELISA optical density OD(450) readings of IgG antibodies to both the amino-terminal aa 1-116 of EBNA-2 and carboxyl-terminal aa 451-641 of EBNA-1 were elevated significantly in patients with SLE, primary SS, RA, SSc and secondary SS when compared to EBNA-1. The OD readings were divided by serum IgG concentrations to normalize for the hypergammaglobulinaemia. The specific levels of IgG antibodies to the amino-terminal region of EBNA-2 were elevated in patients with SLE, primary SS or RA, as well as those with secondary SS complicated with SLE or RA. The EBNA-2 amino-terminal region contains a polyproline tract and a proline-rich sequence and has considerable amino acid sequence homology with many cellular proline-rich proteins. High ratios of EBNA-2 aa 1-116 to EBNA-1 aa 451-641 IgG antibody levels which probably suggest reactivation of EBV latent infection were associated significantly with pulmonary involvement in SS patients. These results are consistent with the hypothesis that the sequence similarity between the amino-terminal region of EBNA-2 and proline-rich cellular proteins is associated with pathogenesis in a subpopulation of CTD patients, possibly by the molecular mimicry-epitope shift mechanism.     

Prevalence of systemic autoimmune rheumatic diseases and clinical significance of ANA profile: data from a tertiary hospital in Shanghai,China

It is necessary and useful to explore prevalence of various systemic autoimmune rheumatic diseases (SARDs) in patients with suspicion of having SARDs and to characterize antinuclear antibodies (ANA) profile for identifying different populations (SARDs and non‐SARDs). A total of 5024 consecutive patients with available medical records were investigated, whose sera had been tested for ANA profile, including ANA, anti‐dsDNA and anti‐extractable nuclear antigen (ENA) antibodies, between 31 January 2012 and 26 March 2014. Only 594 (11.8%) patients were diagnosed with SARDs of those suspected with SARDs. The prevalence of systemic lupus erythematosus (SLE) was highest (3.2%), followed by rheumatoid arthritis (RA) (2.5%), primary Sjögren's syndrome (pSS) (1.7%), ankylosing spondylitis (AS) (1.5%), etc. Of females, SLE also showed the highest prevalence (6%), while of males, AS showed the highest prevalence (1.9%). The prevalence of most SARDs was closely associated with age, except mixed connective tissue disease (MCTD), and the variation characteristics among different age groups were different among various SARDs. The prevalence of ANA was significantly increased in most SARD patients [especially in SLE, systemic sclerosis (SSc) and MCTD]. For anti‐ENA antibodies, in contrast to some autoantibodies associated with multiple SARDs (e.g. anti‐SSA, SSB, nRNP), others were relatively specific for certain diseases, such as anti‐dsDNA, Sm, histone, nucleosome and Rib‐P for SLE, anti‐SCL‐70 for SSc and anti‐Jo‐1 for polymyositis/dermatomyositis (PM/DM). Of note, ANA profile appeared to be of little significance for AS, ANCA‐associated vasculitis (AAV), polymyalgia rheumatic (PMR), adult‐onset Still's disease (ASD) and Behcet's disease (BD). The younger were more likely to have the presence of anti‐dsDNA, Sm, histone or Rib‐P for SLE, and anti‐SSA for RA or MCTD. No significant differences for frequencies of ANA and anti‐ENA autoantibodies were found between sexes in most SARDs, with the exception of RA and AS. The present study suggests that, of patients with SARDs‐like clinical manifestations, the proportion of those with true SARDS is small, for most of whom tests for autoantibodies are necessary and useful to help make a prompt and precise diagnosis.     

Heterogeneity of ribosomal autoantibodies from human, murine and canine connective tissue diseases

Antiribosomal auto-antibodies (anti-Rib.Ab) have been studied in connective tissue diseases (human, dog and mouse) by immunoblotting after one-dimensional (1D) or two-dimensional (2D) gel electrophoresis of rat ribosomes. Anti-Rib.Ab could be found in systemic lupus erythematosus (SLE), rheumatoid arthritis (RA) and other connective tissue diseases (progressive systemic sclerosis, PSS; Sj?gren syndrome, SjS; mixed connective tissue disease, MCTD; and dermatomyositis, DM with the frequencies 41.7%, 54.6% and 33%, respectively. Immunoblotting after 1D gel electrophoresis showed the great heterogeneity of ribosomal proteins recognized by the anti-Rib.Ab. In the SLE, however, the most frequent antibodies stained bands of the 40S subunit: 30 kDa (34% of positive sera), 19.5 kDa (24.5%) and 43 kDa (17%). In RA, the 25-kDa band of the 60S subunit was the most common (54% of positive sera). In the other human connective tissue diseases, there was no particular predominance. In the MRL/1, anti-Rib.Ab were very frequent (92.6%). The 43-kDa band of the 40S subunit was found in 100% of positive sera. Seventeen out of nineteen dogs with SLE gave positive results on immunoblot, and all of them stained the 43-kDa band of the 40S subunit. 2D gel electrophoresis gave identification of Po, L7, L5, Sb, S19, S13 and L2 proteins in SLE, S3 and SjS, L35a and L37a in RA, and L7, S6 and/or L7a in MRL/1.     

The presence of immunosuppressive ''p15E-like'' factors in the serum and urine of patients suffering from malign and benign breast tumours.

Autoantibodies in sera from patients with systemic lupus erythematosus (SLE) and onchocerciasis recognize calreticulin (CaR), a calcium-binding protein, as antigen. In this study we present the immunological properties of two synthetic peptides prepared to correspond to the 1-24 and 7-24 amino acid sequence of CaR. In contrast to information previously reported for the recombinant protein, the CaR-peptide analogues appeared immunoreactive to anti-Ro/SSA autoimmune sera. Human sera from patients with SLE, Sjögren's syndrome (SS), rheumatoid arthritis (RA), as well as mixed connective tissue disease (MCTD), demonstrated a positive autoimmune response (binding of antibodies), to the CaR-peptide analogues. These findings suggest that anti-calreticulin autoantibodies are not restricted to any disease specificity.     

Autoantibodies to poly(ADP-ribose)polymerase in autoimmune diseases

Antibodies to various nuclear proteins are frequently found in sera of patients affected by connective tissue diseases and other autoimmune diseases. We investigated the specificity of circulating autoantibodies to poly(ADP-ribose)polymerase (pADPRP) in different autoimmune and connective tissue diseases: Systemic Lupus Erythematosus (SLE), Rheumatoid Arthritis (RA), Progressive Systemic Sclerosis (PSS), Sjogren's Syndrome (SS), Undifferentiated Connective Tissue Disease (UCTD), Cryptogenic Fibrosing Alveolitis (CFA) and Sarcoidosis. pADPRP was purified from calf thymus. Antibody specificity was detected by ELISA, western blot and enzyme activity precipitation. Positive values (mean O.D. values + 3 S.D. of 36 normal controls) were obtained in 7/15 SLE patients, 1/18 RA patients, 1/30 PSS, 3/14 SS, 0/5 UCTD, 5/21 CFA and 4/25 Sarcoidosis. The positive sera also recognized the pADPRP protein when tested by western blot. Furthermore the enzyme activity was inhibited after immunoprecipitation by some highly positive sera.     

An antibody reacting with splenic red pulp macrophages in the sera of patients with rheumatic diseases

An antibody was detected in the sera of patients with certain rheumatic diseases that reacted with the cytoplasm of the splenic red pulp (SRP) cells of adult mice. This antibody was detected in the sera of all patients with mixed connective tissue disease (MCTD), 53% of patients with systemic lupus erythematosus (SLE), 42% with Sj?gren's syndrome (SS), and 10% with rheumatoid arthritis (RA). However, this antibody was found neither in the sera from patients with other types of rheumatic diseases nor in healthy volunteers. The screening of this antibody may be useful in diagnoses of MCTD, SLE, and SS. In the present study, we also performed the characterization of the cells reacting with this antibody. The cells proved to be acid phosphatase positive phagocytes in the SRP, that is, red pulp macrophages. Moreover, a histochemical analysis of the reacting antigen in these cells has demonstrated that its antigenic activity is NaIO4 and RNase sensitive, suggesting that the antigen may be associated with RNA.     

Antibodies against polypeptides of purified Epstein-Barr virus in sera from patients with connective tissue diseases.

Antibodies to Epstein-Barr virus (EBV) were investigated in patients with systemic lupus erythematosus (SLE) and mixed connective tissue disease (MCTD) by immunoblotting using purified virus. Compared with sera from Epstein-Barr virus seropositive healthy individuals who served as control, sera from patients less frequently recognized several polypeptides. In particular, a 100 kDa envelope polypeptide was recognized by 92% of healthy subjects and only 11% of patients (P less than 0.001). On the other hand, 62% of the patient sera had antibodies to the 42 kDa envelope polypeptide, whereas these antibodies were only present in 4% of the sera from the control subjects (P less than 0.001). These results could reflect either perturbations of the immune response associated with connective tissue disorders or a possible pathogenic role of EBV.     

Levels of antibodies against C1q and 60 kDa family of heat shock proteins in the sera of patients with various autoimmune diseases

Previously a strong positive correlation was found between antibodies to C1q (C1qAb) and antibodies against human heat shock protein (hsp60) and mycobacterial hsp65 in HIV infected patients. Here the levels of these antibodies were measured in the sera of patients with different autoimmune diseases (122 systemic lupus erythematosus (SLE), 55 systemic sclerosis, 33 undifferentiated connective tissue disease (UCTD), 27 primary Raynaud syndrome, 21 rheumatoid arthritis (RA), 14 polymyositis/dermatomyositis (PM/DM), and 192 healthy blood donors. The prevalence of IgG C1qAb was found to be high (P<0.0001 as compared to the healthy controls) only in the SLE group. The levels of the anti-hsp60 (P=0.0094) and anti-hsp65 (P=0.0108) antibodies were high only in the UCTD patients. No correlation was found between the C1qAb and anti-hsp antibodies in any group except a significant (P=0.011) positive correlation between C1qAb and hsp65 antibodies in the patients with UCTD. These findings indicate that the autoantibodies against C1q are heterogeneous: in different diseases different types of C1qAb may dominate.     

Antibodies to nRNP, Sm, Ro(SSA) and La(SSB) detected by ELISA: their specificity and inter-relations in connective tissue disease sera

The profile of autoantibodies to four soluble cellular ribonucleoproteins nRNP, Sm Ro(SSA) and La(SSB) was determined using ELISA with immuno-affinity-purified antigens in a connective tissue disease population. Compared with immunodiffusion, results using ELISA showed greater sensitivity but lower specificity and low titres of antibodies were frequently found in the sera of patients with connective tissue diseases other than systemic lupus erythematosus. This was true even for antibodies to Sm which have been considered highly specific for SLE. Antibodies to these antigens were predominantly of the IgG class and were capable of fixing complement irrespective of the clinical context. As previously demonstrated by immunodiffusion strong associations between anti-nRNP and anti-Sm and between anti-Ro(SSA) and anti-La(SSB) were detected by ELISA, while antibodies to nRNP and to Ro(SSA) identify distinctive serological groups. The observation that certain antibodies are closely linked suggests a relationship between the immune responses to particular antigens, and this might be explained by biological links between the antigens.     

Lupus autoantibodies discriminate between the highly homologous Sm polypeptides B/B' and SmN by binding an epitope restricted to B/B'.

The ubiquitous Sm polypeptides B/B' (28 and 29 kD) and the highly homologous tissue-specific Sm N polypeptide (29 kD) share several autoepitopes recognized by systemic lupus erythematosus (SLE) sera. Previous studies on the antigenicity of nuclear antigens recognized by human autoantibodies have not discriminated between ubiquitous and tissue-specific forms. We set out to examine whether a tissue-specific nuclear antigen, Sm N, is autoantigenic in SLE by comparing the immunoreactivity of the most unique sequences in this polypeptide. Synthetic peptides from the two regions of least sequence homology that occur between Sm N and Sm B/B', a dodecamer (amino acid residues 179-190 containing five substitutions) and an undecamer (residues 203-213 containing four substitutions) were coupled to a carrier protein. These conjugates were used to quantify IgG anti-peptide antibodies in sera from patients with SLE. Of 43 sera with anti-Sm specificity, six bound to the B/B' 179-190 peptide but not to the N version. None of 17 anti-Sm-negative SLE sera bound these peptides. The second region of least sequence homology between N and B/B' (203-213) was not antigenic. Our data suggest that a subset of SLE patients with anti-Sm reactivity have IgG autoantibodies capable of discriminating between Sm N and SmB/B' polypeptides by binding a previously unreported SmB/B'-specific autoepitope. The data also indicate that brain and heart-specific anti-Sm antibodies do not exist in SLE sera, suggesting that these tissues do not participate in the induction or maintenance of the autoimmune anti-Sm response.     

Autoantibodies directed against the amino-terminal domain I of human calpastatin (ACAST-DI Ab) in connective tissue diseases. High levels of ACAST-DI Ab are associated with vasculitis in lupus

To identify new autoantibody populations in patients with rheumatic diseases, a cDNA expression library was immunoscreened with a rheumatoid arthritis (RA) patient's serum which contains autoantibodies binding to uncharacterized polypeptides by Western-blotting. One clone encoding the amino-terminal region (Nt) [domain L and half of domain I] of human calpastatin was selected. Different fragments of the selected cDNA were prepared and the corresponding recombinant polypeptides were produced by in vitro translation and analysed by Western blotting. Most RA sera bound to recombinant amino-terminal region and domain I but not to domain L. This prompted us to use a recombinant polypeptide corresponding to the domain I of calpastatin as the antigen in a solid-phase ELISA to test sera from patients with various systemic rheumatic diseases and healthy controls.Anti-calpastatin domain I antibodies (ACAST-DI Ab), were detected by ELISA in RA, systemic lupus erythematosus (SLE), Sj?gren's syndrome and control sera at respective frequencies of 10, 9, 0 and 1%. These Ab did not have prognostic value in early RA; high levels were significantly associated with vasculitis in SLE. Antibodies reacting with the calpastatin amino-terminal region are produced during systemic rheumatic diseases and are predominantly directed against domain I. High levels of these Ab may constitute a marker of vasculitis in SLE.     

Clinical application of anti double-stranded and single-stranded DNA antibodies measurements by enzyme-linked immunosorbent assay (ELISA) using E. coli plasmid DNA]

Anti double-stranded (ds) and single-stranded (ss) DNA IgG antibodies were detected in patients with various connective tissue diseases by RECOMBIGEN ELISA Anti ds-DNA Kit and ELISA Anti ss-DNA Kit (Nippon DPC Co) using E. coli plasmid DNA. High levels of anti ds-DNA and anti ss-DNA antibodies were mostly found and distributed in patients with systemic lupus erythematosus(SLE) and allied disorders. The sensitivity of Anti ds-DNA Kit was higher than that of current ELISA kit using calf thymus DNA antigen. In SLE patients with anti DNA antibodies sixty per cent of sera were reacted with both ds- and ss-DNA antigens, and forty per cent of sera were reacted only with ss-DNA antigen; there was no sample reacted positively with ds-DNA antigen alone. RECOMBIGEN ELISA Anti ds-DNA Kit and ELISA Anti ss-DNA Kit are highly sensitive and useful methods to detect anti ds- and/or ss-DNA IgG antibodies in patients with SLE.     

Anti‐centrosome antibodies: Prevalence and disease association in Chinese population

Anti‐centrosome antibodies are rare findings with undefined clinical significance in clinical research. We aimed at investigating the prevalence and clinical significance of anti‐centrosome antibodies in Chinese population. Testing results of total of 281,230 ANA‐positive sera were retrospectively obtained from West China Hospital Sichuan University in China between 2008 and 2017. We retrospectively collected and analysed the clinical and laboratory data of the patients with positive anti‐centrosome antibody. Of the 356 453 patients tested, 281 230 patients had positive antinuclear antibodies (ANAs, 78.9%), but only 78 patients with positive anti‐centrosome antibodies (0.022%), of which 74.4% are females. Diagnoses were established in 69 of 78 patients: 37 cases were autoimmune diseases, mainly including undifferentiated connective tissue diseases (UCTD, 9/37), rheumatoid arthritis (RA, 6/37), Sjögren's syndrome (SS, 5/37) and primary biliary cirrhosis (PBC, 5/37), and the remaining were other autoimmune conditions. The most frequent clinical symptoms of the anti–centrosome‐positive patients were arthralgia and eyes and mouth drying. Additionally, 86.7% of anti‐centrosome antibodies were not associated with other ANA profiles; however, when associated, the most frequent ANA was anti‐U1RNP. Anti‐centrosome antibodies are featured by a low prevalence and female gender predominance. They are correlated with some specific diseases, both autoimmune diseases, especially UCTD, RA, SS and PBC, and non‐autoimmune diseases, such as infection and cancer, which suggests that they might be potential supporting serological markers of these diseases.     

Distribution and antigen specificity of anti-U1RNP antibodies in patients with systemic sclerosis.

Systemic sclerosis (SSc) is a generalized connective tissue disease which is characterized by the presence of several autoantibodies. To determine the prevalence and antigen specificity of anti-U1RNP antibodies (anti-U1RNP) in patients with SSc, serum samples from 223 patients with SSc, 117 patients with systemic lupus erythematosus (SLE), 18 patients with mixed connective tissue disease (MCTD) and 40 healthy control subjects were examined by indirect immunofluorescent analysis (IIF), double immunodiffusion, and immunoblotting using nuclear extract of HeLa cells. Eighteen of the 223 (8%) serum samples from patients with SSc were shown to be positive for anti-U1RNP. The frequency of anti-U1RNP positivity in limited cutaneous SSc (14%) was significantly higher than that in those with diffuse cutaneous SSc (3%). Anti-Sm antibodies were detected in patients with SLE positive for anti-U1RNP, but not in those with SSc positive for anti-U1RNP or those with MCTD. Immunoblotting demonstrated that anti-70-kD antibodies were detected more often in patients with SSc positive for anti-U1RNP and in those with MCTD than in those with SLE. Furthermore, anti-U1RNP was closely correlated with pulmonary fibrosis and joint involvement in patients with SSc. These results suggest that anti-70-kD antibodies are useful in the classification of patients with anti-U1RNP.