Racial differences in the distribution of systemic sclerosis-related serum antinuclear antibodies

Systemic and localized scleroderma in children: current and future treatment options

Scleroderma is a group of rare and complex diseases with varied clinical manifestations. The most obvious manifestation of the diseases is skin hardening and sclerosis. Scleroderma can be divided into two main subgroups: systemic and localized. The systemic form, also known as systemic sclerosis, involves diffuse skin involvement and potentially severe visceral involvement. Localized scleroderma on the other hand is more common in children and usually confined to a specific region of the body with no internal organ involvement. The juvenile forms of systemic sclerosis and localized scleroderma are important conditions in children because of the clinical severity and substantial mortality of systemic scleroderma and the major growth defects associated with childhood-onset localized disease even if the active disease itself is self-limited. The pathogenic pathways of the various forms of scleroderma are only partially defined, but the main defect in scleroderma is abnormal collagen deposition leading to eventual fibrosis in the skin as well as multiple organ systems such as the heart and lungs in juvenile systemic sclerosis. Therapeutics are divided into three main subgroups for systemic sclerosis: antifibrotics, anti-inflammatories, and vasodilators. For localized disease, anti-inflammatories, vitamin D analogs, and UV irradiation have been investigated. However, the infrequency of scleroderma in the pediatric population plus the fact that this disease is very often self-limiting makes randomized controlled trials very difficult. It is for this reason that most data on treatment modalities for this disease have been extrapolated from studies in adult patients. There is no one therapy for systemic sclerosis or localized scleroderma that has proven to be very effective or significantly disease modifying. However, current therapeutic strategies must be initiated early in the disease course for maximum beneficial clinical effects. New interventions such as autologous stem cell transplant and cytokine-directed therapies are under investigation as potential treatments for this complex disease.

Anti-DNA topoisomerase II α autoantibodies in Japanese patients with systemic sclerosis

The pathogenesis and etiology of systemic sclerosis (SSc) remain unknown, but the presence of several autoantibodies is recognized as one of its prominent features. The clinical significance of anti-DNA topoisomerase II alpha antibody (anti-topo II alpha Ab) remains unknown in Japanese patients with SSc. To determine the prevalence and clinical correlation of anti-topo II alpha Ab in Japanese patients with SSc. Serum samples were obtained from 103 Japanese patients with SSc. Control serum samples were obtained from 43 healthy Japanese volunteers. Anti-topo II alpha Abs were determined by enzyme linked-immunosorbent assay.IgG anti-topo II alpha Ab levels were significantly increased in SSc patients (n=103) compared to normal controls (n=43; P<0.005). IgG or IgM anti-topo II alpha Ab was detected in 19% (20/103) of SSc patients when absorbance values higher than the mean+2SD of control serum samples were considered positive. By contrast, IgG or IgM anti-topo II alpha Ab was observed in only 7% (3/43) of healthy individuals. The presence of pulmonary fibrosis was more frequently detected in SSc patients with IgG anti-topo II alpha Ab than those without the Ab (P<0.05). Moreover, % DLco and % VC were significantly decreased in SSc patients with anti-topo II alpha Ab relative to those without the Ab (P<0.05 and P<0.01, respectively). The elevated levels of both erythrocyte sedimentation rate and C-reactive protein were also more frequently observed in SSc patients positive for IgG anti-topo II alpha Ab (P<0.005). The results of the present study indicate that anti-topo II alpha Ab represent one of the autoantibody specificities detected on SSc patients and may be regarded a serological marker of pulmonary fibrosis in Japanese patients with SSc.

Enzyme-linked immunosorbent assay for detection of anti-RNA polymerase III antibody: analytical accuracy and clinical associations in systemic sclerosis

OBJECTIVE

We have recently developed an enzyme-linked immunosorbent assay (ELISA) for detection of anti-RNA polymerase III (anti-RNAP III) antibody, using a recombinant fragment containing the immunodominant epitope as the antigen source. This study was conducted to assess the analytical accuracy and clinical associations of the anti-RNAP III ELISA in patients with systemic sclerosis (SSc).

METHODS

To evaluate analytical sensitivity and specificity of the ELISA, both immunoprecipitation tests and ELISA were used to detect anti-RNAP III antibody in 534 SSc sera from patients at 3 medical centers. Sera from 522 SSc patients and 516 controls, including patients with other connective tissue diseases and blood bank donors, were also evaluated to assess the clinical sensitivity and specificity of the ELISA. Clinical findings in anti-RNAP III antibody-positive SSc patients were compared between patient groups stratified according to anti-RNAP III antibody levels determined by the ELISA.

RESULTS

In SSc patients, our ELISA showed analytical sensitivity of 91% and analytical specificity of 99% compared with the immunoprecipitation assay (a gold standard for detection of anti-RNAP III antibody). The additional analysis using a large series of SSc and control sera showed that clinical sensitivity and specificity of the ELISA with respect to the diagnosis of SSc were 17% and 98%, respectively. A high level of anti-RNAP III antibody was associated with diffuse cutaneous SSc, higher maximum total skin score, and increased frequency of tendon friction rubs.

CONCLUSION

The anti-RNAP III ELISA is analytically accurate and clinically specific. With this assay, testing for anti-RNAP III antibody can be made routinely available.

Rheumatic diseases in minority populations

Rheumatic diseases are expressed in all ethnic populations, but differ in prevalence, genetic associations, clinical features, and responses to interventions. Most data describing these differences do so in reference to and comparisons with white populations. These are sparse data that evaluate differences within minority populations where there is more homogeneity of external factors, such as social, cultural, and behavioral attitudes. This article reviews the features that are unique to various rheumatic diseases within minority populations.

Effective Use of Autoantibody Tests in the Diagnosis of Systemic Autoimmune Disease

Screening for disease-specific autoantibodies may be useful in asymptomatic ANA-positive individuals as a means of evaluating the risk of developing a systemic autoimmune disease such as systemic lupus erythematosus (SLE), polymyositis/dermatomyositis (PM/DM), scleroderma (SSc), Sjögren's syndrome (SS), rheumatoid arthritis (RA), or primary biliary cirrhosis (PBC) in the future. In patients with known or suspected systemic autoimmune disease, a panel of disease-specific markers may help to establish a diagnosis and to assess the prognosis. The great strides in autoantibody testing over the last 20 years make it feasible to use specific autoantibody markers to improve diagnostic accuracy in systemic autoimmune disease. New technology enabling screening for multiple autoantibodies may further enhance the clinical usefulness of autoantibody testing, making it possible to diagnose autoimmune disease in its earliest stages and to intervene before serious end organ damage occurs.

Computer-assisted classification of HEp-2 immunofluorescence patterns in autoimmune diagnostics

Indirect immunofluorescence with HEp-2 cells presents the major screening method for detection of autoantibodies in systemic autoimmune diseases. Hereby, a large variety of autoantibody entities can be detected and recognized by at least partially typic fluorescence patterns. Currently, this method requires highly specialized technicians and resists automatization. Nevertheless, requirements of good laboratory practice, especially standardization and documentation are hampered by the common microscopic technique. Here, we present a computer-assisted system for classification of interphase HEp-2 immunofluorescence patterns in autoimmune diagnostics. Designed as an assisting system, representative patterns are acquired by an operator with a digital microscope camera and transferred to a personal computer. By use of a novel software package based on image analysis, feature extraction and machine learning algorithms, relevant characteristics describing patterns could be found out. Our results show that identification of positive fluorescence and pre-differentiation between most important HEp-2 staining patterns can be performed by this system. Results and documentation of fluorescence patterns can be integrated into the laboratory system. To enable the usage of such a system in routine diagnostics, accuracy of this system and correct recognition of interferring patterns must be further improved.

Ethnicity and race and systemic sclerosis: how it affects susceptibility, severity, antibody genetics, and clinical manifestations

Most studies have suggested that ethnic factors impact significantly on systemic sclerosis. Extensive epidemiologic studies have been carried out in white individuals, and limited data suggest that blacks are affected twice as frequently; Japanese patients have a lower prevalence than whites. This highest rate that has been described has been in Choctaw Native Americans. Blacks have a lower age at onset, as well as a higher frequency of diffuse skin involvement, pulmonary disease, and an overall worse prognosis than whites. Limited data in Hispanics and Native Americans suggest that they have more severe disease than whites. Whites have the highest frequency of anti-centromere antibodies (associated with limited skin involvement and less pulmonary fibrosis), whereas blacks have a higher frequency of anti-ribonucleoprotein and fibrillarin autoantibodies; the latter is a nucleolar antibody associated with a poorer prognosis. Ethnic differences are also seen for associations with non-major histocompatibility complex genes, such as FBN1 (fibrillin) genes, in Choctaws and Japanese and SPARC (osteonectin) in whites, Hispanics, and Choctaws. Although these facts do not entirely rule out socioeconomic factors associated with ethnicity, nevertheless ethnicity has an important impact on the pathogenesis of systemic sclerosis, perhaps because of genetic factors.

The prevalence and clinical significance of anti-U1 RNA antibodies in patients with systemic sclerosis

We studied the prevalence and clinical significance of anti-U1 RNA antibodies in patients with systemic sclerosis. The presence of anti-U1 RNA antibodies was determined using immunoprecipitation in systemic sclerosis patients with anti-U1 RNP antibodies (n=36), antitopoisomerase I antibodies (n=20), or anticentromere antibodies (n=20), mixed connective tissue disease patients (n=23), systemic lupus erythematosus patients with anti-U1 RNP antibodies (n=26), and normal controls (n=20). Moreover, antigen specificities for anti-U1 RNP antibodies were examined in patients with systemic sclerosis by immunoblotting and enzyme-linked immunosorbent assay. Anti-U1 RNA antibodies was detected in 22 of 36 systemic sclerosis patients (61%) with anti-U1 RNP antibodies, 14 of 23 patients (61%) with mixed connective tissue disease, and eight of 26 systemic lupus erythematosus patients (31%) with anti-U1 RNP antibodies. Anti-U1 RNA antibodies were not detected in other groups. As for systemic sclerosis patients, the frequencies of pulmonary fibrosis and reduced percentage diffusion capacity for carbon monoxide were significantly greater in patients with anti-U1 RNA antibodies than in those without (76%vs 18%, p<0.005; 82%vs 27%, p<0.005, respectively). Moreover, patients with anti-U1 RNA antibodies had significantly lower percentage diffusion capacity for carbon monoxide and percentage vital capacity values than those without (51.9+/-16.8 vs 79.4+/-16.4, p<0.01; 83.8+/-21.4 vs 101.4+/-12.9, p<0.05, respectively). Regarding the antigen specificities of anti-U1 RNP antibodies in systemic sclerosis patients, the frequency of anti-70 kDa antibodies determined by immunoblotting was significantly higher in patients with anti-U1 RNA antibodies than in those without (77%vs 43%, p<0.05). This finding was also confirmed by enzyme-linked immunosorbent assay for anti-70 kDa antibodies (86%vs 43%, p<0.05). These results indicate that anti-U1 RNA antibodies may be a serologic indicator for pulmonary fibrosis in systemic sclerosis patients with anti-U1 RNP antibodies.

Identification of an immunodominant epitope on RNA polymerase III recognized by systemic sclerosis sera: application to enzyme-linked immunosorbent assay

OBJECTIVE

To characterize an immunodominant epitope on RNA polymerase III (RNAP III) recognized by systemic sclerosis (SSc) sera and to develop an enzyme-linked immunosorbent assay (ELISA) for the detection of serum anti-RNAP I/III antibodies.

METHODS

RNAP III-specific subunits RPC62 and RPC155 were generated in a bacterial expression system as a series of recombinant fragments. Reactivities to these recombinant fragments were examined by immunoblots and/or ELISA in 16 SSc sera containing anti-RNAP I/III antibodies, 89 SSc sera lacking anti-RNAP I/III antibodies, 61 systemic lupus erythematosus (SLE) sera, and 61 healthy control sera.

RESULTS

Anti-RNAP I/III-positive SSc sera recognized several distinct epitopes on RPC62 and RPC155 in various combinations, but the fragment encoding amino acids at positions 732-1166 of RPC155 was recognized by all 11 anti-RNAP I/III-positive SSc sera tested. Carboxyl- and amino-terminal deletion studies showed that at least 130 amino acids at positions 891-1020 of RPC155 were necessary for the antibody binding, but strong reactivity required an additional amino-terminal extension. When a purified recombinant fragment containing the immunodominant epitope was used as the antigen source in an ELISA, elevated antibody reactivity was detected in all 16 anti-RNAP I/III-positive SSc sera, but in no anti-RNAP I/III-negative SSc, SLE, or healthy control sera, representing a sensitivity of 100% and a specificity of 100%.

CONCLUSION

A major epitope commonly recognized by SSc sera containing anti-RNAP I/III antibodies was identified on RPC155. The ELISA using a recombinant fragment expressing the immunodominant epitope should be a valuable tool for routine screening for anti-RNAP I/III antibodies in clinical diagnostic laboratories.

[Immunological diagnosis of scleroderma]

Systemic sclerosis is characterized by a fibrosis and a microvascular injury. These vascular lesions can affect internal organs causing severe visceral damages. The pathogenesis of this disease is complex but some immunological disorders with a production of antinuclear auto-antibodies can be useful to the clinicians, especially for an early diagnosis and to distinguish the scleroderma/myositis overlap syndromes. This review presents the target antigens and the methods of detection of the different antinuclear auto-antibodies. Sensitivity, specificity and clinical association between the antinuclear auto-antibodies and the different subclasses of scleroderma are also presented in detail.

Increased prevalence of autoantibodies to ku antigen in African American versus white patients with systemic lupus erythematosus

OBJECTIVE

To investigate whether the widely varying estimates of the prevalence of anti-Ku autoantibodies are explained by racial/ethnic differences.

METHODS

Consecutive African American or white patients who met the 1982 criteria for systemic lupus erythematosus (SLE) and who were evaluated over 10 years in North Carolina, Florida, and New York were tested by immunoprecipitation of K562 cell extract for anti-Ku as well as anti-nuclear RNP (nRNP)/Sm, anti-Ro/SSA, and anti-La/SSB autoantibodies.

RESULTS

Anti-Ku autoantibodies were detected in sera from 18 of 155 African American patients with SLE (12%) versus 0 of 126 white patients (P < 0.0001, by Fisher's exact test). Anti-nRNP (63% versus 16%; P < 0.0001) and anti-Sm (23% versus 7%; P < 0.0004) autoantibodies were also more common in the African American subset. The 2 groups had comparable frequencies of anti-Ro/SSA and anti-La/SSB autoantibodies.

CONCLUSION

Anti-Ku antibodies are common in African American patients with SLE but rare in whites, probably explaining the different estimates of their prevalence. In African Americans, the frequency is comparable with that of anti-La/SSB. Along with anti-Ku, anti-nRNP and anti-Sm autoantibodies are also overrepresented in African Americans, suggesting that a group of specificities is characteristically associated with SLE in African Americans.

Anti-fibrillarin antibodies in systemic sclerosis

OBJECTIVES

To investigate the nature and extent of organ involvement in anti-fibrillarin antibody (AFA)-positive patients within a UK systemic sclerosis (SSc) population.

METHODS

We investigated 1026 consecutive patients with SSc. AFA was identified by the characteristic clumpy nucleolar and coilin body pattern of staining in interphase cells and staining of fibrillarin in metaphase cells by indirect immunofluorescence using HEp-2 cells. Identity of the 34-kDa fibrillarin protein was confirmed by immunoprecipitation from [(35)S]methionine-labelled HeLa cell extract.

RESULTS

AFA was detected in 42 patients (4.1%) with early disease onset (mean age 36 yr). Sixteen (38%) patients had limited cutaneous (lcSSc) and 26 (62%) diffuse cutaneous SSc (dcSSc). All eight Afro-Caribbean patients with AFA had dcSSc whereas the Caucasians were equally divided between dcSSc and lcSSc. Within the dcSSc subgroup, 54% had myositis, 35% had pulmonary hypertension, 15% had cardiac involvement and 23% had renal involvement.

CONCLUSIONS

AFA identifies young SSc patients with frequent internal organ involvement, especially pulmonary hypertension, myositis and renal disease. In contrast to previous reports, AFA was not restricted to dcSSc patients in Caucasians.

An immunodominant epitope on DNA topoisomerase I is conformational in nature: heterogeneity in its recognition by systemic sclerosis sera

OBJECTIVE

To characterize an immunodominant epitope recognized by anti-DNA topoisomerase I (topo I) antibody, a major autoantibody in sera of patients with systemic sclerosis (SSc).

METHODS

Topo I fragments were generated as fusion proteins using a bacterial expression system as well as polypeptides translated in vitro using a eukaryotic expression system. Reactivities to the 2 preparations of recombinant topo I polypeptides in anti-topo I-positive sera from SSc patients of varied ethnic backgrounds were examined by immunoblotting, immunoprecipitation, and/or enzyme-linked immunosorbent assay.

RESULTS

The fragment encoding amino acids 489-573 of topo I was recognized by 98 of 100 anti-topo I-positive SSc sera. Both carboxyl- and amino-terminal deletion studies as well as competitive inhibition assays using topo I synthetic peptides showed that a region of > or =52 amino acids (512-563) was necessary for recognition by anti-topo I antibodies. The minimum epitope region and conformation required for this reactivity were variable among sera from Caucasian, African American, Japanese, and Choctaw SSc patients.

CONCLUSION

An immunodominant epitope recognized by anti-topo I autoantibody is located in the region of amino acids 489-573 of the topo I protein and is largely conformational in nature. The recognition pattern of this region by anti-topo I-positive sera is heterogeneous and is influenced by ethnic background.

Influence of ethnic background on clinical and serologic features in patients with systemic sclerosis and anti-DNA topoisomerase I antibody

OBJECTIVE

To investigate the effect of ethnicity on clinical and serologic expression in patients with systemic sclerosis (SSc) and anti-DNA topoisomerase I (anti-topo I) antibody.

METHODS

Clinical and serologic features, as well as HLA class II allele frequencies, were compared among 47 North American white, 15 North American black, 43 Japanese, and 12 Choctaw Native American SSc patients with anti-topo I antibody.

RESULTS

The frequency of progressive pulmonary interstitial fibrosis was lower, and cumulative survival rates were better in white compared with black and Japanese patients. Sera of white and black patients frequently recognized the portion adjacent to the carboxyl terminus of topo I, sera of Japanese patients preferentially recognized the portion adjacent to the amino terminus of topo I, and sera of Choctaw patients recognized both portions of topo I. Anti-RNA polymerase II and anti-SSA/Ro antibodies were present together with anti-topo I antibody more frequently in sera of Japanese patients than in sera of white patients. The HLA-DRB1 alleles associated with anti-topo I antibody differed; i.e., DRB1*1101-*1104 in whites and blacks, DRB1*1502 in Japanese, and DRB1*1602 in Choctaws. Multivariate analysis showed that ethnic background was an independent determinant affecting development of severe lung disease as well as survival.

CONCLUSION

Clinical and serologic features in SSc patients were strongly influenced by ethnic background. The variability of disease expression in the 4 ethnic groups suggests that multiple factors linked to ethnicity, including genetic and environmental factors, modulate clinical manifestations, disease course, and autoantibody status in SSc.

Autoantibodies to RNA polymerases recognize multiple subunits and demonstrate cross-reactivity with RNA polymerase complexes

OBJECTIVE

To determine the subunit specificity of autoantibody directed to RNA polymerases (RNAP) I, II, and III, which is one of the major autoantibody responses in patients with systemic sclerosis (SSc).

METHODS

Thirty-two SSc sera with anti-RNAP antibodies (23 with anti-RNAP I/III, 5 with anti-RNAP I/III and II, and 4 with anti-RNAP II alone) were analyzed by immunoblotting using affinity-purified RNAP and by immunoprecipitation using 35S-labeled cell extracts in which RNAP complexes were dissociated. Antibodies bound to individual RNAP subunits were eluted from preparative immunoblots and were further analyzed by immunoblotting and immunoprecipitation.

RESULTS

At least 15 different proteins were bound by antibodies in anti-RNAP-positive SSc sera in various combinations. All 9 sera immunoprecipitating RNAP II and all 28 sera immunoprecipitating RNAP I/III recognized the large subunit proteins of RNAP II and III, respectively. Reactivity to RNAP I large subunits was strongly associated with bright nucleolar staining by indirect immunofluorescence. Affinity-purified antibodies that recognized a 62-kd subunit protein cross-reacted with a 43-kd subunit protein and immunoprecipitated both RNAP I and RNAP III. Antibodies that recognized a 21-kd subunit protein obtained from sera that were positive for anti-RNAP I/III and II antibodies immunoprecipitated both RNAP II and RNAP III.

CONCLUSION

Anti-RNAP antibodies recognize multiple subunits of RNAP I, II, and III. Moreover, the results of this study provide the first direct evidence that antibodies that recognize shared subunits of human RNAPs or epitopes present on different human RNAP subunits are responsible for the recognition of multiple RNAPs by SSc sera.

African-American race and antibodies to topoisomerase I are associated with increased severity of scleroderma lung disease

STUDY OBJECTIVES

To determine whether African-American race is independently associated with lung disease in scleroderma.

DESIGN

Retrospective review.

SETTING

University medical center in Baltimore.

PATIENTS

One hundred one patients with diffuse cutaneous scleroderma with available serum samples.

MEASUREMENTS

Patients underwent lung function testing as part of their routine clinical care. Percent predicted values adjusted for race were calculated for FVC, single-breath carbon monoxide diffusing capacity (Dco), and FEV1. Serum samples were assayed for the presence of antibodies to topoisomerase I and RNA polymerase II.

RESULTS

Scleroderma patients of African-American race had lower percent predicted values than white patients for FVC (p<0.002), Dco (p<0.0001), and FEV1 (p<0.0001). Antibodies to topoisomerase I but not antibodies to RNA polymerase II were also associated with lung function. African-American scleroderma patients were distinct from white patients in having younger age of onset and higher prevalence of antibodies to topoisomerase I. In multivariate analyses accounting for sex, age, smoking history, years of scleroderma symptoms, and RNA polymerase II antibody status, African-American race and topoisomerase I antibody status independently predicted lower lung function.

CONCLUSION

African-American race and antibodies to topoisomerase I are independent risk factors for scleroderma lung disease.

Immunoglobulin allotype gene polymorphisms in systemic sclerosis: interactive effect of MHC class II and KM genes on anticentromere antibody production

OBJECTIVE

To examine potential interactions between immunoglobulin (Ig)-allotype gene polymorphisms and susceptibility to systemic sclerosis (SSc) as well as serological expression in SSc patients.

METHODS

IgG heavy chain allotypes G1M(f, z), G2M(n+, n-), G3M(b, g) and Ig light chain allotype KM(1, (1, 2), 3) were genotyped in 105 Japanese SSc patients and 47 race matched normal controls using polymerase chain reaction (PCR) based methods. Associations of each Ig allotype with SSc related antinuclear antibodies were examined in combination with or without MHC class II alleles.

RESULTS

GM/KM genotypic and allelic frequencies were similar in SSc patients and in normal controls. Frequencies of G1M(f) and G2M(n+) were significantly decreased in anticentromere antibody (ACA) positive SSc patients compared with ACA negative SSc patients (p = 0.04 and 0.02, respectively). Conversely, the presence of DQB1*0501 and KM(1, 2) significantly increased the risk of ACA positivity.

CONCLUSION

Ig allotype gene polymorphisms were not associated with susceptibility to SSc. Instead, the results suggested that MHC class II and KM genes are associated with autoimmune responses by interactively promoting the production of ACA.

Analysis of IgG subclasses of human antitopoisomerase I autoantibodies suggests chronic B cell stimulation

Antitopoisomerase I autoantibodies are highly specific of scleroderma and are mainly IgG. The present study was designed to evaluate the prevalence of each IgG antitopoisomerase I subclass. An ELISA for the detection of IgG antitopoisomerase I subclasses was standardized and used to study the antibodies from 49 antitopoisomerase I-positive patients identified from a total of 541 patients. Correlations and multivariate analysis were performed to determine the frequency of associations between the IgG antitopoisomerase I subclasses. All IgG antitopoisomerase I subclasses were found. Twelve patients (24.5%) had all four IgG antitopoisomerase I subclasses, 13 (26.5%) had three, 16 (32.7%) had two, and 7 (14.3%) had only one antitopoisomerase I subclass. The presence of all four IgG antitopoisomerase I subclasses suggests that this specific B-cell is the target of multiple activation pathways which indicate that there is a complex T-cell-cytokine-driven process. Together with the absence of other autoantibodies in these sera, our results support the concept of a multiple but highly selected and chronic B-cell activation in scleroderma patients with antitopoisomerase I.

Clinical setting of patients with systemic sclerosis by serum autoantibodies

Associations of antinuclear (ANA) and anticardiolipin (aCL) antibodies with clinical manifestations were analyzed in patients with systemic sclerosis (SSc). We studied 105 SSc patients: 28 had limited cutaneous SSc (lcSSc) involving fingers; 36 had intermediate cutaneous SSc involving limbs and face; 33 had diffuse cutaneous SSc (dcSSc) involving the trunk; 8 had a sclerosis sine scleroderma. Clinical manifestations and instrumental and laboratory findings were considered to calculate a disease score. Serum anticentromere (ACA), anti-topoisomerase I (anti-topo I) antibodies, and aCL (of IgG/IgA/IgM classes) were investigated by conventional methods. ACA positive patients (n=18), compared to ACA negative, showed higher prevalence of IcSSc (p < 0.001), lower prevalence of restrictive ventilatory defect (p=0.006), and lower disease score (p=0.008). Anti-topo I positive patients (n= 70) showed lower prevalence of lcSSc (p =0.001) compared to anti-topo I negative. In aCL positive patients (n=27) widespread skin and visceral involvement occurred more frequently than in aCL negative. The association with myocardial ischemia or necrosis (p=0.010) was significant. Occurrence of ACA excluded the coexistence of anti-topo I (p < 0.001), and aCL (p=0.037). aCL positive patients showed higher disease score in comparison with ACA positive patients (p=0.003). In conclusion ACA recognize patients with a mild disease. aCL in contrast to ACA are better than anti-topo I in recognizing the most severe pictures of SSc.

Antinuclear antibody in systemic sclerosis (scleroderma)

The presence of autoantibodies to intracellular molecules is the hallmark immunologic finding of SSc. Recent sophisticated methods have contributed to characterization of unidentified antigens of ANA in sera from patients with SSc. Antibodies to RNA polymerases are the third major SSc-specific ANA, in addition to anti-topo I and anticentromere antibodies, and it is now possible to identify over 85% of SSc patients. These antibodies have proved helpful in diagnosis of this disease. An immunogenetic predisposition to synthesis of the ANAs has been unveiled. Both antigen-driven and molecular mimicry hypotheses have been proposed for ANA production in SSc. Although the role of ANAs in the pathogenesis of SSc is not yet known, it is logical to assume that the origin of ANAs is linked to the causes of this disease because each antibody is associated with its own unique constellation of clinical features.

Clinical significance of antinuclear antibodies in systemic rheumatic diseases

Autoantibodies directed to intracellular antigens can be detected in many systemic rheumatic diseases. In this review, we discuss the clinical significance of antinuclear antibodies (ANA) associated with systemic lupus erythematosus (SLE), Slögren's syndrome, scleroderma and polymyositis/dermatomyositis, the immunogenetic factors associated with these four autoimmune diseases, and the possible role of autoantibodies in the etiopathogenesis of autoimmune disease. The antibodies associated with systemic rheumatic diseases serve as important tools in the initial diagnosis, and they are also useful in the evaluation of prognosis. However, for correct conclusions, the autoantibody findings should be carefully considered and interpreted in clinical context.

Detection of autoantibodies to nucleolar transcription factor NOR 90/hUBF in sera of patients with rheumatic diseases, by recombinant autoantigen-based assays

OBJECTIVE

We attempted to clarify the clinical characteristics of Japanese patients with autoantibodies to nucleolar transcription factor NOR 90/hUBF (anti-NOR 90) and to analyze the autoantigenic epitopes recognized by anti-NOR 90.

METHODS

Ninety-one patient sera containing anti-nucleolar antibodies (ANoA) by indirect immunofluorescence were collected. Immunoblottings were performed using recombinant fusion proteins expressed from several cloned complementary DNA (cDNA) encoding the NOR 90/hUBF autoantigen.

RESULTS

Anti-NOR 90 were detected in sera from 9 (9.9%) of 91 patients with ANoA. Seven of these patients were diagnosed as having Sjögren's syndrome, 4 had concomitant rheumatoid arthritis, 1 had concomitant systemic sclerosis (SSc), and 2 had SSc alone. All 9 sera were reactive with more than 2 recombinant fusion proteins from cDNA encoding separate regions on the hUBF polypeptide.

CONCLUSION

The results suggest that while anti-NOR 90 antibodies are rare, they are associated with Sjögren's syndrome in Japanese patients, and that autoimmunity is targeted toward at least 2 separate regions (amino acids 89-310 and 310-633) of the hUBF polypeptide.

Autoantibodies to fibrillarin in systemic sclerosis (scleroderma). An immunogenetic, serologic, and clinical analysis

OBJECTIVE

To determine the frequency, clinical associations, and any major histocompatibility complex correlations of antifibrillarin antibodies in patients with systemic sclerosis (SSc).

METHODS

Antifibrillarin antibodies were determined by indirect immunofluorescence, immunoblotting, and immunoprecipitation, and HLA class II alleles by DNA oligotyping, in a large cohort of SSc patients.

RESULTS

Antifibrillarin was found in 8% of 335 SSc sera and was significantly more common in blacks (16%) than whites (5%), in males (33%) than females (14%), and in patients with cardiac, renal, or gut involvement. The HLA class II haplotype DRB1*1302, DQB1*0604 was found significantly more frequently in SSc patients with antifibrillarin compared with race-matched normal controls and 260 SSc patients without antifibrillarin. In addition, 1 or more of the HLA-DQB1 alleles *0604, *0301, *0602, and/or *0302 was found in all antifibrillarin-positive patients, and 62% of the antifibrillarin-positive patients had 2 of these HLA-DQB1 alleles, a highly significant difference from both race-matched normal controls and antifibrillarin-negative SSc patients.

CONCLUSION

Antifibrillarin, although an infrequent nucleolar autoantibody, is a marker for severe SSc, especially in blacks and males, and is strongly associated with a unique HLA haplotype, as well as with combinations of certain HLA-DQB1 alleles.

Sensitivity and specificity of anti-Jo-1 antibodies in autoimmune diseases with myositis

OBJECTIVE

To determine the sensitivity and specificity of anti-Jo-1 in systemic sclerosis (SSc) patients with and without myositis.

METHODS

Immunoblots on HeLa nuclei were used to screen sera from 554 consecutive connective tissue disease patients. Those who had 45-55-kd bands, all patients with polymyositis/dermatomyositis (PM/DM), and a random selection of SSc, Raynaud's disease, systemic lupus erythematosus, and rheumatoid arthritis patients were also studied by anti-Jo-1 enzyme-linked immunosorbent assay and by immunoblots on rabbit pooled aminoacyl-transfer RNA synthetase.

RESULTS

Anti-Jo-1 was present only in 8 of the 40 PM/DM patients.

CONCLUSION

Anti-Jo-1 is specific for PM/DM.

Molecular biology of autoantigens in rheumatic diseases

The advent of molecular biologic techniques has provided new approaches that are of great utility to the study of autoimmune-mediated responses. In the past few years, there has been a remarkable accumulation of knowledge concerning the molecular identity and function of autoantigens, and further consolidation for the use of autoantibodies as diagnostic markers in clinical rheumatology. The understanding of basis methodologies in molecular biology applied to the study of autoantigens, in particular, techniques for cloning and analyzing genes that are important in rheumatic diseases, is valuable for both basic scientists and clinicians interested in diagnostic and prognostic markers of various connective tissue diseases.

HLA class II genes associated with anticentromere antibody in Japanese patients with systemic sclerosis (scleroderma)

OBJECTIVE

To define further HLA class II gene associations with anticentromere antibody (ACA), a major serum antinuclear antibody in patients with systemic sclerosis (SSc).

METHODS

HLA class II genes were determined using polymerase chain reaction/restriction fragment length polymorphisms in 94 Japanese patients with SSc (22 ACA positive and 72 ACA negative) and 50 race matched normal control subjects.

RESULTS

Frequency of DQB1*0501 was increased in ACA positive SSc patients compared with ACA negative SSc patients (36% versus 13%; p = 0.02, odds ratio = 4.0, 95% confidence interval 1.1 to 13.9), but the association of ACA with a polar amino acid at position 26 in the DQB1 beta 1 domain, which was demonstrated in white North Americans, was not observed in Japanese. The DRB1*0101, *0405, and *1302 alleles were associated with high ACA titres, whereas DRB1*1502 was associated with low ACA titres and a low frequency of centromere protein C (CENP-C) reactivity.

CONCLUSIONS

These results suggest that the ACA response is associated with multiple HLA class II genes and that ACA positive SSc patients are heterogeneous in terms of immunogenetic background.

T cell proliferative response induced by DNA topoisomerase I in patients with systemic sclerosis and healthy donors

The in vitro T cell proliferative response to DNA topoisomerase I (topo I) was examined in 26 systemic sclerosis (SSc) patients with anti-topo I antibody, 10 SSc patients without anti-topo I antibody, and 21 healthy donors. Using recombinant fusion proteins encompassing the entire human topo I amino acid sequence, a topo I-specific proliferative response was detected in PBMC cultures from 25 (96%) anti-topo I-positive SSc patients, 4 (40%) anti-topo I-negative SSc patients, and 13 (62%) healthy donors. Molecular typing at MHC class II loci revealed that all SSc patients and healthy donors having either DRB1*1501,2 (DR15), DRB1*1101,3,4 (DR11), or DRB1*07 (DR7) were responders. Characterization of the topo I-induced T cell proliferative response showed that (a) the responding cells were CD4+ T cells; (b) antigen-presenting cells were necessary for the response; (c) the response was restricted by HLA-DR, and to a lesser extent by HLA-DQ; and (d) the estimated frequency of the responding T cells determined by limiting dilution analysis was 1/9,277-1/24,853. PBMC cultures from anti-topo I-positive SSc patients showed a high T cell proliferative response after only 3 d of culture with topo I. Anti-topo I-negative SSc patients and healthy donors had no proliferative response after 3 d, but did respond after 7 d of culture. T cell proliferative responses to six truncated topo I fragments tested individually showed different patterns of T cell proliferation that were dependent upon the responder's HLA-DR alleles. These results indicate that T cells reactive with topo I are components of the normal T cell repertoire, and that the topo I-specific T cell proliferative response is not associated with the presence or absence of SSc or anti-topo I antibody, but is restricted by MHC class II alleles.

Major histocompatibility complex class II gene associations with anti-U1 small nuclear ribonucleoprotein antibody. Relationship to immunoreactivity with individual constituent proteins

OBJECTIVE

To better define immunogenetic associations with the anti-U1 ribonucleoprotein (U1 RNP) autoantibody response.

METHODS

HLA class II alleles were determined by genotyping in 49 Japanese rheumatic disease patients with anti-U1 RNP antibody and 43 race-matched healthy controls. Immunoreactivities to U1 RNP constituent proteins (70K, A, B/B', and C) were detected by immunoblots using purified HeLa cell Sm antigen, and antibody titer was determined by passive hemagglutination assay.

RESULTS

DQB1*0302 was significantly more frequent in anti-U1 RNP-positive patients than in controls (43% versus 14%; odds ratio [OR] = 4.6, corrected P = 0.03). All anti-U1 RNP-positive patients had either a DQB1*0601, *0602, *0301, *0302, or *0303 allele, which share tyrosine at position 30, and the amino acid sequence Thr, Arg, Ala, Glu, Leu, Asp, and Thr at positions 71-77 in the DQB1 beta 1 domain. In contrast, one of these alleles was found in 81% of the controls (OR = 24, P = 0.002). In addition, anti-U1 RNP antibody was associated with unique DQB1*0302; DRB1*0401 haplotype. Anti-70K reactivity and antibody titer were positively associated with a basic amino acid residue, arginine or histidine, at position 13 (DR2 or DR4) and were negatively associated with the amino acid sequence Ile, Leu, Glu, and Asp at positions 67-70, which was present in some of the DR5-, DR6-, and DR8-associated alleles, in the DRB1 beta 1 domain. Anti-C reactivity was strongly associated with DR2, particularly with DRB1*1502.

CONCLUSION

The several shared epitopes located on HLA-DRB1 and DQB1 genes control the anti-U1 RNP autoantibody response.

Autoantibodies in systemic sclerosis

There are 3 major autoantibodies in sera from patients with scleroderma: 1) anticentromere antibodies (ACA), 2) anti-topoisomerase I (anti-topo I), and 3) anti-RNA polymerases. Each is present in about 25% of patients and are mutually exclusive. ACA are found in patients with primary and secondary Raynaud's disease and in patients with primary biliary cirrhosis. Anti-topo I and anti-RNA polymerases are found exclusively in scleroderma. Each autoantibody is present in specific subsets of scleroderma patients. ACA and anti-topo I have been well studied and their presence and titer are stable over time. The anti-topo I and ACA are of all three isotypes, recognize multiple epitopes on the antigens and have stable cross reactive or private idiotypes. The antigen, topoisomerase I, has domains which have homology to viral proteins. Other autoantibodies predominantly recognize nucleolar antigens, are found in less than 15% of patients, and are not specific for scleroderma.

Autoantibodies in scleroderma and tightskin mice

There is much evidence to suggest that scleroderma in human patients is caused by a fundamental defect in the immune system. In tightskin mice, the scleroderma syndrome is associated with autoimmunity, particularly autoantibodies interacting with scleroderma target antigens.