Characteristics of antinuclear antibodies in rheumatoid arthritis. Reactivity of rheumatoid factor with a histone-dependent nuclear antigen

Stratified distribution of Th17 and Treg cells in patients with multi-stage rheumatoid arthritis

OBJECTIVE

Rheumatoid arthritis (RA) is a typical, progressive autoimmune disease. Its occurrence and development are associated with dysregulation of T and B cell numbers. However, the specific immune characteristics of different RA courses remain incompletely defined. Here, we describe the peripheral blood lymphocyte subsets, particularly CD4 + T subsets, of different RA courses with a focus on early RA (Ea-RA).

METHODS

In all, 131 patients with Ea-RA, 117 with advanced RA (Ad-RA), and 109 with treated RA (Tr-RA) were enrolled. We collected general clinical data. Whole blood samples obtained from the patients and 97 healthy controls (HCs) were analysed via flow cytometry.

RESULTS

Decreased absolute NK cell numbers and increased CD4/CD8 T cell ratios were observed in different RA groups, including Ea-RA, compared to healthy controls. In Ea-RA patients, the Th17 and Treg cell numbers were similar to those in HCs. We performed k-means clustering based on the profiles of Th17 and Treg cells for patients with multi-stage of RA. We identified three patient types: type A characterised by relatively low Treg and Th17 cell numbers, type B with moderate levels of Treg cells and levels of Th17 cells similar to that of type C patients, and type C with high levels of Treg cells and levels of Th17 cells similar to that of type B patients.

CONCLUSION

The immune characteristics of Ea-RA patients differ from those of HCs; an immune system disorder is apparent although no differences in Th17 and Treg levels were evident between Ea-RA patients and HCs. We found distributional heterogeneities of Th17 and Treg cells in patients with multi-stage of RA. Stratified management based on such heterogeneity may serve as a useful novel immunotherapy allowing of early intervention.

Diagnosing rheumatoid arthritis disease using fuzzy expert system and machine learning techniques

Rheumatoid Arthritis (RA) is a very common autoimmune disease that causes significant morbidity and mortality, and therefore early diagnosis and treatment are important. Early diagnosis of RA and knowing the severity of the disease are very important for the treatment to be applied. The diagnosis of RA usually requires a physical examination, laboratory tests, and a review of the patient’s medical history. In this study, the diagnosis of RA was made with two different methods using a fuzzy expert system (FES) and machine learning (ML) techniques, which were designed and implemented with the help of a specialist in the field, and the results were compared. For this purpose, blood counts were taken from 286 people, including 91 men and 195 women from various age groups. In the first method, an FES structure that determines the severity of RA disease has been established from blood count using the laboratory test results of CRP, ESR, RF, and ANA. The FES result that determines RA disease severity, the Anti-CCP level that is used to distinguish RA disease, and the patient’s medical history were used to design the Decision Support System (DSS) that diagnoses RA disease. The DSS is web-based and publicly accessible. In the second method, RA disease was diagnosed using kNN, SVM, LR, DT, NB, and MLP algorithms, which are widely used in machine learning. To examine the effect of the patient’s history on RA disease diagnosis, two different models were used in machine learning techniques, one with and one without the patient’s history. The results of the fuzzy-based DSS were also compared with the diagnoses made by the specialist and the diagnoses made according to the 2010 ACR / EULAR RA classification criteria. The performed DSS has achieved a diagnostic success rate of 94.05% on 286 patients. In the study of machine learning techniques, the highest success rate was achieved with the LR model. While the success rate of the model was 91.25 % with only blood count data, the success rate was 97.90% with the addition of the patient’s history. In addition to the high success rate, the results show that the patient’s history is important in diagnosing RA disease.

Frequency of ANA/DFS70 in Relatives of Patients with Rheumatoid Arthritis Compared to Patients with Rheumatoid Arthritis and a Healthy Population, and its Association with Health Status

INTRODUCTION

DFS70 ANAs have attracted interest due to their frequency in individuals with no clinical evidence of systemic autoimmune rheumatic disease, groups with genetic risk for rheumatoid arthritis (RA) were not assessed.

OBJECTIVE

To determine the frequency of ANA and DFS70 ANA in blood relatives (BR) of people with RA compared to patients with early RA (ERA), and control individuals, and its association with health status.

METHODOLOGY

A cross-sectional study with an analytical component. Sixty ERA patients, 60 BR and 120 control individuals paired by age and sex were studied. Hep2-ANA and DFS70 ANA were studied. The absolute and relative frequencies and associations were established using logistic regression models, with a significance level of 95%.

RESULTS

43% ANA in ERA, 30% in BR, and 25.8% in control individuals 1:80. The fine dense granular pattern based on conventional Hep2 was found in 12.9% of the positive samples, and 1.66% of the total samples. There was no detection of DFS70 ANAs in patients with ERA. In ERA there was an association between the presence of ANA and inflamed joints (p=.02), CRP (p=.01), DAS28CRP (p=.03) and HAQ (p=.04). There was an association between ANA and elevated CRP (p=.05) in the BR. In the control individuals, there was an association between ANA and painful joints (p=02). In DFS70 ANA individuals we observed an association between a normal ESR p=.032, BR (-), p=.044 and absence of painful joints, p=.039.

CONCLUSIONS

The frequency of DFS70 ANA in the groups studied was low, none of the patients with ERA was positive. The presence of DFS70 ANA was only confirmed in systemically healthy individuals.

Stratification of Nuclear Homogeneous Patterns on HEp-2 Cells Based on Neutrophil Nuclear Staining

Antinuclear antibody (ANA) testing is used to diagnose systemic autoimmune rheumatic disease (SARD). Nuclear homogeneous patterns on ANA-HEp-2 cells can result from anti-double-stranded DNA (dsDNA), anti-nucleosome, anti-histone, anti-Scl-70, or anti-dense fine speckles 70 (DFS70) antibodies (Abs). This study aimed to find a way to discriminate DFS70 Abs from others by way of assessing neutrophil nuclear staining on anti-neutrophil cytoplasmic antibody (ANCA) testing. Nuclear staining on ANCA-neutrophils was assessed to stratify nuclear homogeneous patterns on ANA-HEp-2 cells. Enrolled subjects included (1) young individuals with a dense fine speckled pattern on ANA testing (young non-SARD group, n=71) and patients with (2) systemic lupus erythematosus (SLE group, n=35); (3) rheumatoid arthritis possibly with histone, nucleosome Abs, and others (RA group, n=51); and (4) diffuse systemic sclerosis with Scl-70 Abs (diffuse SSc group, n=19). Negative rates (95% confidence interval) of neutrophil nuclear staining were 97.2% (90.2%-99.7%) in the young non-SARD group, 2.9% (0.1%-14.9%) in the SLE group, 3.9% (0.5%-13.5%) in the RA group, and 47.4% (24.5%-71.1%) in the diffuse SSc group. The negative rate of the young non-SARD group was significantly higher than those of the other groups (all p<0.05). In conclusion, this study suggests that the assessment of nuclear staining on ANCA-neutrophils can help to stratify nuclear homogeneous patterns on ANA-HEp-2 cells and thus to determine whether the ANA pattern is attributed to DFS70 Abs, which can be found in healthy individuals, especially in young individuals.

Detection of 16α-Hydroxyestrone-histone 1 Adduct as High-Affinity Antigen for Rheumatoid Arthritis Autoantibodies

Increased concentrations of 16α-hydroxyestrone (16α-OHE₁) have been observed in rheumatoid arthritis (RA), but the underlying mechanism of this remains elusive. Here we aimed to identify the role played by 16α-OHE₁ in RA. In 40 RA patients, the specificities of antibodies from the sera of these patients were checked by direct binding, inhibition ELISA, and quantitative precipitation titration. Competition ELISA was also used for the estimation of 16α-OHE₁ in the serum of different RA patients. RA IgG from a patient's sera showed strong recognition to 16α-OHE₁-H₁ (histone 1) adduct in comparison to control subjects (p < 0.001), as the formation of this adduct brings out various biochemical changes that might generate neo-epitopes, which have been well-recognized by these antibodies. The affinity of RA antibodies for 16α-OHE₁-H₁ (1.10 × 10^- 7 M) was high, as detected by the Langmuir plot. Comparing RA patients to the controls, no significant differences were detected in the level of 16α-OHE₁ or 2-hydroxyestrone/16α-OHE₁ ratio. 16α-OHE₁-H₁ might have an antigenic role and function as a high-affinity antigen for RA autoantibodies and, therefore, could be used as a biomarker for this disease.

Historical observations contributing insights on etiopathogenesis of rheumatoid arthritis and role of rheumatoid factor

When studies on rheumatoid arthritis (RA) that were made many decades ago and could be considered "historical" in nature are analyzed in the context of recent observations, important insights on RA and on the function of rheumatoid factor (RF) become apparent. RF in the role of antibody to immune complexes (ICs) appears to be involved in activation of the complement system and in the production of chemotactic and inflammatory mediators, creating a condition that can be sustained and reinitiated. In the synovial cavity, a state of nonresolving inflammation is produced with the formation of citrullinated protein antigen-antibody complexes or other forms of ICs. This is followed by a second wave of IC production in the form of RF acting as antibody reactive with the initial ICs. Both of these processes are associated with complement consumption and production of inflammatory mediators. We present a model of an initiation phase of RA that might represent an example of repetitive formation of ICs and complement-mediated inflammation. Targeting therapy at this phase of RA to break the cycles of recurrent inflammation might be a novel approach to aid in further control of the disease.

Dr Eng M. Tan: a tribute to an enduring legacy in autoimmunity

At the age of ninety years, Dr Eng Meng Tan has had a remarkable impact on the accumulated knowledge of autoimmune diseases, including seminal findings in systemic lupus erythematosus (SLE) and a wide range of other autoimmune diseases. Dating to the first description of the Sm (Smith) autoantibody in SLE, his focus has been the use of autoantibodies as probes to identify and elucidate novel cellular molecules and then translating these discoveries into biomarkers and immunoassays for a wide range of these diseases and, later, cancer. He led efforts to standardize autoantibody nomenclature and testing protocols. Through his mentorship a great number of trainees and collaborators have had remarkably successful careers, and by that virtue he has garnered a remarkable continuing legacy.

Anti-CCP in systemic lupus erythematosus patients: a cross sectional study in Brazilian patients

Recently, it has been found that some lupus patients may have anti-cyclic citrullinated peptide antibodies (anti-CCP), although the clinical significance of such finding is not well established. Systemic lupus erythematosus (SLE) patients may have joint complaints that are very similar to those observed in rheumatoid arthritis (RA). In early stages of disease, this form of arthritis can be difficult to differentiate from RA, so it is not rare that some SLE patients are initially misdiagnosed to have this disease. This study aims to investigate the prevalence of anti-CCP in SLE patients from Southern Brazil and its association with clinical and serological profiles. One hundred nine SLE patients were studied for anti-CCP and compared with data of 156 RA patients and 100 healthy volunteers. Comparison of clinical and autoantibody profile of anti-CCP-positive and anti-CCP-negative SLE patients was done. All SLE patients positive of anti-CCP were submitted to hand and feet X-rays. Anti-CCP was positive in 15 of 109 SLE patients, and one of them had confirmed the diagnosis of rhupus. This prevalence was significantly higher than in healthy controls (p = 0.0004) and lower than in RA patients (p < 0.0001). No relationship could be found with clinical profile, including joint complaints. SLE patients with anti-CCP had higher prevalence of anti-Ro (p = 0.02) and anti-La (p = 0.004) autoantibodies, in comparison with those negative to anti-CCP. We found that 13.7% of Brazilian patients with SLE have positive anti-CCP. Patients with anti-CCP showed higher prevalence of anti-Ro and anti-La autoantibodies than those negative for anti-CCP. Only a careful and prolonged follow-up will reveal the real clinical value of these markers in each patient individually.

Antigen specificity of antihistone antibodies in connective tissue disease patients with anti-U1RNP antibodies

To determine the prevalence of antibodies to individual histone components in collagen disease patients with anti-U1RNP antibodies. Serum samples were examined by enzyme-linked immunosorbent assay. Patients with mixed connective tissue disease (MCTD) and systemic sclerosis (SSc) showed similar levels and patterns of antihistone antibody (AHA) reactivities to individual histones: IgG responses to H2B or H3 and IgM responses to H2B were highest. However, both IgG and IgM AHAs against outer portion of chromatin (H1, H2A, or H2B) were generally higher in SLE compared with other diseases. SLE or SSc patients with anti-U1RNP antibodies showed generally higher AHA levels than in those without them. Thus, the pattern of reactivities to each histone component was dependent on the disease, while the intensity was dependent on both the disease and anti-U1RNP antibodies. The antigenic stimulus in SLE may be different from other connective tissue diseases and is more likely to be native chromatin.

Progress in the use of biochemical and biological markers for evaluation of rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic systemic inflammatory autoimmune disorder which is predominant in females. The exact etiology remains undefined. Recently, a large number of biochemical and biologic markers, which are useful in the diagnosis, prognosis, and monitoring therapy of RA, have been reported. The new markers include genetic markers, filaggrin, citrulline containing peptides, A2/RA33, cytokines, joint and collagen breakdown products, and bone turnover markers. No laboratory tests in and of themselves are diagnostic of RA. The new markers have been employed in monitoring RA patients during treatment and following the course of the disease. With the development of innovative therapies for RA, many of the biochemical and biologic markers will be useful.

Antinuclear antibody testing in systemic autoimmune disease

This article discusses the use and interpretation of antinuclear antibody (ANA) testing in connective tissue diseases. Methods of ANA detection are discussed and analyzed in detail as is the role of ANAs in systemic lupus, scleroderma, and polymyositis, connective tissue diseases with prominent pulmonary involvement.

Antigen specificity of antihistone antibodies in systemic sclerosis

OBJECTIVES

The aim of the study was to determine the prevalence and clinical significance of antibodies to individual histone components in systemic sclerosis (SSc).

METHODS

Serum samples from patients with limited cutaneous SSc (lSSc; n = 42) and diffuse cutaneous SSc (dSSc; n = 28) were examined for IgG and/or IgM antibodies to individual histone components and complexes by enzyme linked immunosorbent assay (ELISA).

RESULTS

The level of IgG antibody to total histones was significantly higher in lSSc and dSSc than in normal controls. The level of IgM antibody to total histones was significantly higher in lSSc, but not in dSSc, than in normal controls. IgG antibody to total histones tended to be increased in dSSc when compared with that in lSSc. On the other hand, IgM antibody to total histones tended to be increased in lSSc when compared with that in dSSc. Although SSc showed various antihistone specificities, H2B, H2A-H2B, (H2A-H2B)-dsDNA were main antigens recognised by IgG antibodies in both lSSc and dSSc. Although IgM antibodies to H2B and H2A-H2B were also detected in both lSSc and dSSc, serum samples from lSSc patients exhibited highest IgM reactivity with H1.

CONCLUSION

SSc may be included among conditions in which heterogeneous antihistone antibodies are produced. IgM antibodies to the most accessible histone H1 may be related to mild clinical features (lSSc) and IgG antibodies to the inner core molecules of native histone such as H2B or complexes including H2B may be associated with severe clinical features (dSSc) in Ssc.

Epstein-Barr virus-transformed human B lymphocytes produce natural antibodies to histones

To study the mechanism(s) responsible for the appearance of Epstein-Barr virus (EBV)-induced anti-histone autoantibodies, peripheral blood B lymphocytes from healthy donors were infected with EBV and the resulting lymphoblastoid cell lines were tested for secretion of antibodies reacting with histones. It was found that EBV-transformed cells produce IgM antibody reactive with histones and that the frequency of EBV-inducible circulating B lymphocytes that produce antibodies to histones is at least 10(-5). Moreover, in cultures of tonsillar lymphoid cells, the enrichment in CD5+ B lymphocytes increases the percentage of EBV-transformed cultures making anti-histone IgM antibodies. EBV may therefore, also in vivo, induce natural anti-histone antibody by polyclonal B-cell activation without any requirement of antigen to trigger antibody response.

Autoantibodies in D-penicillamine-induced myasthenia gravis: a comparison with idiopathic myasthenia and rheumatoid arthritis

The distribution of autoantibodies was studied in patients with rheumatoid arthritis (RA) treated by D-penicillamine and who developed myasthenia gravis (MG). The anti-human acetylcholine receptor (AChR) antibodies were specifically associated with clinical symptoms of MG without any difference in the pattern of specificities in idiopathic (id-MG) or in induced MG (DPen-MG). Conversely, anti-nuclear antibodies were elevated in DPen-MG sera compared to id-MG sera (P less than 0.001) but were also compared to patients with RA treated by D-penicillamine (or thiopronine) and who did not develop MG. Anti-denatured DNA antibodies were enhanced in sera from treated patients, whether they had presented or not a MG disease. Anti-histone antibodies were associated with RA. These observations suggest that the immunological imbalance in RA patients, can be increased by a drug treatment which may trigger the appearance of a second autoimmune disease such as MG, where anti-AChR antibodies are associated with anti-nuclear antibodies.

Polyclonal human rheumatoid factors cross-reacting with histone H3: characterization of an idiotope on the H3 binding site

The development of highly sensitive immunoassays has made the detection of the multireactivity of antibodies a relatively common phenomenon. Polyreactivity is frequent in human auto antibodies, especially in rheumatoid factors (RFs), but the structural basis and the significance of this phenomenon remain substantially unknown. Recently, we showed that the double reactivity of a human monoclonal RF with histones was probably due to two distinct binding sites. However, cross-reactivity seems more frequent among polyclonal RFs occurring during autoimmune diseases than with monoclonal RFs. We studied double-reactive (IgG and histone H3) polyclonal RFs in a patient suffering from primary Sjögren's syndrome. We showed by means of affinity chromatographies that H3 cross-reactive RFs were only a small subset of the total patient's RFs and that this subset was enriched in IgA class. Competitive inhibition experiments suggested the existence of two distinct binding sites for IgG and H3. These results were confirmed by showing the selective sensitivity to acid treatment of the histone binding site and by producing a murine antiidiotope monoclonal antibody BII 2.1 defining an idiotope on bireactive RF apparently linked to the H3 binding site. This idiotope was absent in a panel of monoclonal RF, one of them cross-reacting with histone H3. This report extends previous results concerning a monoclonal RF to the polyclonal RFs which occur during autoimmune diseases.

Monoclonal antibody 6B6.6 defines a cross-reactive kappa light chain idiotope on human monoclonal and polyclonal rheumatoid factors

Mouse monoclonal antibody (MAb) 6B6.6 was raised against a cross-reactive idiotope (CRI) present on the light chains of 2 human IgM paraproteins with rheumatoid factor (RF) activity. The MAb inhibited the IgG-binding activity of these proteins, and thus appears to react with an epitope located at or near the RF-binding site. Enzyme-linked immunosorbent assay (ELISA) and Western immunoblotting studies indicate that the 6B6.6 CRI is associated with kappa IIIa sub-subgroup light chains, is not related to the Wa, Po, and Bla RF cross-idiotypic specificities, and is clearly distinct from the kappa IIIb-associated CRI detected by MAb 17.109. Using an ELISA, we detected 6B6.6 CRI in 59% of 107 sera and 48% of 50 synovial fluids from patients with seropositive rheumatoid arthritis (RA). However, the quantities of CRI-positive RF were small, and the amount of CRI-positive RF did not correlate with the amount of IgM-RF. The 6B6.6 CRI was shown to occur primarily in the IgM fraction of RA sera by both chromatographic studies and isotype-specific ELISA, although small quantities appeared to be associated with IgA and IgG in some sera. The presence of 6B6.6 CRI on both monoclonal and polyclonal RF is consistent with the view that both are derived, at least in part, from a common gene pool. However, its occurrence in relatively low levels suggests that the number of germline genes encoding for RF is large or that extensive mutation occurs in the course of RF expression in RA.

Antihistone antibodies in rheumatoid arthritis and Felty's syndrome

Although antihistone antibodies are frequently detected in patients with systemic lupus erythematosus, they appear to be uncommon or present only at low levels in rheumatoid arthritis (RA) patients. We used an enzyme-linked immunosorbent assay to study sera from 42 patients with RA, and we confirmed that antihistone antibodies mainly occurred at low levels in these patients. In contrast, 83% of 24 patients with Felty's syndrome had antihistone antibodies, often at high levels. Thus, antihistone antibodies may be a common autoimmune abnormality in patients with Felty's syndrome but not in other patients with RA. In addition, we demonstrated that some rheumatoid factors have cross-reactive antihistone antibody activity.

Reactivity of antinuclear antibodies with histones and other antigens in juvenile rheumatoid arthritis

Antinuclear antibodies are found in serum samples from most children with juvenile rheumatoid arthritis (JRA), but the antigenic specificities of these antibodies are not known. Using an immunoblot technique, we found that JRA patients' sera react with a variety of proteins in the nuclei of HEp-2 cells. Antibody to histone H1 was found in 42% of the JRA serum samples. An IgG antibody to a 45-kd protein was found in serum samples from some patients without uveitis, but it was not found in any sample from patients with uveitis. The immunoblot reactivity patterns do not appear to be useful in distinguishing between disease onset types or disease course types in patients with JRA.

Autoantibody profile in juvenile chronic arthritis

Patients with juvenile chronic arthritis (JCA) may be subdivided into a minority, who carry IgM rheumatoid factor and have erosive polyarthritis resembling adult rheumatoid arthritis, and the majority (90%), who are seronegative by conventional means. Between 30 and 60% of patients with JCA have positive antinuclear antibodies (ANAs) according to the choice of substrate for indirect immunofluorescence. The importance of ANAs is the frequent development of associated asymptomatic chronic iridocyclitis, which may impair vision causing worse handicap than the arthritis, which remains predominantly pauciarticular in two thirds of these young children. ANA positive patients rarely possess antibodies to deoxyribonucleic acid (DNA) or extractable nuclear antigens (ENA), and current studies suggest that several different nuclear antigens, including histones, may be involved.

Monocyte Fc receptor function in rheumatoid arthritis. Enhanced cell-binding of IgG induced by rheumatoid factors

Monocytes from 11 patients with rheumatoid arthritis and 10 control subjects were purified by countercurrent elutriation. Rheumatoid arthritis monocytes had more cell-associated IgG (P less than 0.001) and bound more 125I-labeled heat-aggregated IgG in vitro (P less than 0.02) than did monocytes from control subjects. Interaction of rheumatoid factor (RF) with monocytes was then investigated. Purified 125I-labeled IgM-RF and IgG-RF bound directly to monocytes from normal individuals. Furthermore, preincubation of normal monocytes with RF augmented subsequent binding of aggregated IgG to the cells. We conclude that monocyte-associated RF can enhance binding of IgG-containing immune complexes to the cells and can exaggerate the measured number of Fc receptors. Such cell-bound RF may affect clearance of immune complexes by the reticuloendothelial system in vivo.

The Ro/SSA autoantigen as an immunogen. Some anti-Ro/SSA antibody binds IgG

The rheumatic disease autoantigen, Ro/SSA, was immunogenic to a rabbit host. The heteroimmune rabbit serum bound the Ro/SSA particle in immunoblots and in an ELISA. Both the rabbit anti-Ro/SSA and a human prototype anti-Ro/SSA serum also bound IgG; and moreover, IgG inhibited both rabbit and human anti-Ro/SSA activity. Anti-IgG activity of the rabbit and human anti-Ro/SSA sera bound Ro/SSA by Western blot and solid-phase assays. In addition, purified Ro/SSA inhibited the anti-IgG activity of the anti-Ro/SSA sera from rabbit and man. Affinity purification of the IgG- and Ro/SSA-binding fractions of the rabbit anti-Ro/SSA demonstrated that both the anti-Ro/SSA and anti-IgG activities were concentrated in these fractions. These data show that Ro/SSA and IgG share epitopes that are bound by anti-Ro/SSA antibody. Inhibition experiments suggest that this antibody is found in most human anti-Ro/SSA autoimmune sera and that the epitope(s) are found in the F(ab')2 fragment of IgG.

Complement-activating abilities of defined antinuclear antibodies

A complement-fixing immunofluorescence assay on HEp-2 cells was used to assess the ability of various antinuclear antibodies (ANA) to activate complement. Sera which contained only specific antibodies to nuclear RNP, SS-B/La, centromere, Sm antigen, double-stranded DNA, and/or nuclear histone were selected. Relative abilities of various ANA to activate complement were determined from the ratio of titers of C3, C4, or properdin-fixing ANA to the IgG ANA titers. Nuclear RNP-anti-RNP complexes activated and deposited significantly more complement C3 than other ANA (P less than 0.02). Antibodies to SS-B/La, centromere, and Sm activated more complement than anti-DNA or antihistone (P less than 0.02). Antihistone antibodies activated the least complement. These studies demonstrate that different ANA have significantly different orders of complement-activating capabilities when bound to their respective nuclear antigens.

Diffuse interstitial lung disease in rheumatoid arthritis. Views on immunological and HLA findings

Immunological parameters including HLA typing were studied in 32 patients with rheumatoid arthritis (RA) associated diffuse interstitial lung disease (DILD) and in 32 age- and sex-matched RA control patients. The male RA patient group with DILD also included patients with other intrathoracic manifestations and had a higher prevalence of HLA-B8 and Dw3 than did healthy controls, thus agreeing with our earlier results that RA patients with this antigen combination are prone to multiple intrathoracic complications. Patients with DILD had higher titres of rheumatoid factor (RF) and lower complement (C4) levels than matched RA controls. The RF titre was in inverse correlation with C3 and C4 levels, suggesting that RF immune complexes may also promote rheumatoid lung disease via activation of the classical pathway of complement.

Characterisation of non-histone nuclear proteins cross reactive with purified rheumatoid factors

In order to examine the interactions between isolated rheumatoid factors (RFs) and cell nuclear antigens we have prepared 10 RFs by affinity chromatography against IgG coupled to Sepharose. Of these, seven cross reacted with cell nuclei on indirect immunofluorescence. The nuclear antigen appeared to be DNA histones by indirect immunofluorescence on rat liver, though on immunoblotting the rheumatoid factors also reacted with three non-histone polypeptides which were identified in the soluble fraction of nuclear extracts. We were unable to show any relationship between these polypeptides and rheumatoid arthritis nuclear antigen. These reactions represent a hitherto unrecognised phenomenon, which extends the range of antigens recognised by rheumatoid factors. We suggest that the immunopathogenic significance of RFs may not be restricted to their reactivity with IgG, and that non-histone nuclear proteins merit further investigation.

Antinuclear antibodies in autoimmune disease. Significance and pathogenicity

A large number of antigen-antibody systems have been described in association with connective tissue diseases. However, with the exception of antibodies to dsDNA, none of them have yet been successfully implicated in the pathogenesis of autoimmune diseases. It is also unclear why specific ANA are associated just with certain diseases, for example, anti-Sm with systemic lupus erythematosus. Although many questions remain about what triggers ANA production and whether these antibodies are innocent bystanders or disease inducers or enhancers, ANA serology can still be very useful to the clinician.

Patterns of antihistone antibody specificity in systemic rheumatic disease. I Systemic lupus erythematosus, mixed connective tissue disease, primary sicca syndrome, and rheumatoid arthritis with vasculitis

A new fluorimetric assay was used to measure the relative amounts of antibodies to individual nuclear histones in sera from 102 patients with systemic lupus erythematosus (SLE), mixed connective tissue disease, primary sicca syndrome, and rheumatoid arthritis with vasculitis. In SLE sera, the predominant responses were to histones H-1, H-2B, and H-3, with marked elevations of binding to H-1 and H-2B in one-third of the patients, and to H-3 in one-fourth; antibodies of both the IgG and IgM classes were also detected. In a few SLE sera, the pattern of histone response differed or was restricted to 1 immunoglobulin class. In mixed connective tissue disease, only 2 of 9 sera showed elevated histone binding activity, the response being predominantly to H-3 in 1 patient and to H-1 and H-2B in the other. Binding to H-2B was also prominent in 2 of 3 patients with primary sicca syndrome. The highest antihistone reactivity and the most heterogeneous response patterns were observed in patients who had rheumatoid arthritis with vasculitis; 6 of 8 of those sera had elevated histone reactivity. In SLE, the highest histone binding results were found among patients with a history of photosensitivity. Histones are closely associated with DNA in the nucleosome, and we speculate that antihistone antibodies could arise as a result of damage to DNA, induced by drugs or irradiation.

Antinuclear antibody determination: the present state of diagnostic and clinical relevance

Determination of antinuclear antibodies (ANA) will gain in diagnostic significance if a specific type of ANA can be related to a defined clinical disorder. The past decade has brought us quite a lot of papers dedicated to this subject. Yet, with exception of the DNA/anti-DNA system, observed correlations have remained scarce or contradictory. Also, still little is known about the pathogenic role of ANA. Perhaps more recent approaches using biochemical technologies will provide us with highly purified nuclear antigens necessary to study possible correlations at a more sophisticated level.

Identification of multiple Epstein-Barr virus-induced nuclear antigens with sera from patients with rheumatoid arthritis

By means of the protein immunoblot technique, the Epstein-Barr virus (EBV) nuclear antigen (EBNA) could be identified in a variety of EBV-transformed cell lines with anti-EBNA-positive sera from normal donors. The molecular weight of EBNA expressed in each of the cell lines varied between 70,000 and 75,000 and was dependent upon the strain of infecting virus. In contrast, 15 of 21 sera from patients with rheumatoid arthritis identified antigens in addition to EBNA. The most prominent of these antigens had molecular weights of 110,000 to 115,000 and 92,000. All of the EBV genome-positive cell lines except for QIMR-GOR and cell lines containing the P3HR-1 virus expressed these antigens. The antigens were not present in the EBV genome-negative Ramos and BJAB cell lines, nor were they identified with EBV seronegative sera, indicating that they were EBV related. There was no direct correlation between the presence of antibodies in sera to EBNA, viral capsid antigen or early antigen, and reaction with the 92,000-molecular-weight antigen in immunoblots, indicating that this antigen was distinct from previously described EBV-related antigens.

Multiple autoantigen binding capabilities of mouse monoclonal antibodies selected for rheumatoid factor activity

We report that approximately 1/4 of monoclonal rheumatoid factors produced by hybridomas derived from fusions of spleen cells from MRL/lpr/lpr mice with systemic lupus erythematosus (SLE) and arthritis exhibited multiple reactivities with other autoantigens, including dDNA , histones, and/or cytoskeletal-cytoplasmic elements. The patterns of reactivities of most of these clones differed, indicating that each had a separate B cell ancestor. Studies with eluted antibodies demonstrated that a single species of antibody molecules was responsible for the observed multiple reactivities. Inhibition experiments suggested that an antibody combining site may be large enough to accommodate dissimilar epitopes. These findings may provide further insights into the generation and extent of antibody diversity as well as the etiopathogenesis of systemic autoimmune diseases.

The significance of IgM antinuclear antinuclear antibody in rheumatoid arthritis and other connective tissue diseases

An investigation of the incidence of IgG and IgM antinuclear antibodies (ANA) in patients with connective tissue diseases showed that IgM ANA predominated in rheumatoid arthritis, whilst in systemic lupus erythematosus IgG antibodies were more common. Patients with other connective tissue diseases less frequently had antinuclear antibodies and there was little difference in the incidence of IgG and IgM antibodies. Cross reacting rheumatoid factors contributed to the IgM antinuclear activity of rheumatoid sera. IgM ANA was not related to disease activity in patients with rheumatoid arthritis. Immunoglobulin class differences of ANA in rheumatoid arthritis and systemic lupus erythematosus may reflect the differing pathological processes of these two diseases and may be of value in their differential diagnosis.

Autoantibodies to nonhistone nuclear antigens and their clinical significance

Identification of the immunologic specificity of antinuclear antibodies (ANAs) in the various systemic rheumatic diseases has become increasingly important. The standard immunofluorescence technique may enable detection of antibodies to nuclear antigens present in abundance in the nucleus, such as DNA, histones, Sm, nuclear ribonucleoprotein (nRNP), and SS-B/La. The nuclear antigens present in low concentrations, such as SS-A, proliferating cell nuclear antigen (PCNA), rheumatoid arthritis nuclear antigen (RANA), and Ku antigens, are unique to cell types, and their detection requires special substrates or reagent systems. Anti-Sm, anti-Scl-70, anticentromere, and anti-PM-1 are characteristic serologic markers for systemic lupus erythematosus, scleroderma, the CREST syndrome of scleroderma, and polymyositis, respectively. Distinct profiles of ANA characterize different rheumatic diseases. A number of ANAs are found in SLE, whereas other diseases are characterized by the presence or absence of a certain ANA or by differences in mean ANA titers. Specific ANAs have been used to isolate and characterize nuclear antigens at molecular and functional levels.

Histone antibodies in systemic lupus erythematosus. A possible diagnostic tool

Antibodies to total histones and histone fractions H1, H2a-H4, H2b, and H3 were measured in serum samples from 61 patients with systemic lupus erythematosus (SLE), 33 with rheumatoid arthritis, 17 with systemic sclerosis, and 20 with various other diseases by use of a sensitive immunoenzymatic assay. Histone antibodies were present in 52.4% of the SLE samples whereas only 1 of the samples from other diseases was positive (systemic sclerosis). The presence of these antibodies in SLE patients was not associated with any specific clinical manifestations, but was correlated with activity of the disease: 87% (20 of 23) of patients with active SLE, in particular 9 of 9 not yet treated, showed histone antibody whereas only 18% (4 of 22) of samples from patients with inactive SLE were positive. We believe that the measurement of histone antibodies would be a useful addition to the present laboratory parameters (antinuclear and double-stranded DNA antibodies and circulating immune complexes) for the diagnosis and progression of systemic lupus erythematosus, particularly since they seem to appear during or just before the onset of an active phase and tend to be absent during remission.

Specificity of hidden 19S IgM rheumatoid factor in patients with juvenile rheumatoid arthritis

Hidden 19S IgM rheumatoid factors (RF)-i.e., RF detected in the IgM-containing fraction after separation of the serum at an acid pH-have been found in 68% of patients with seronegative juvenile rheumatoid arthritis (JRA). Inhibition studies utilizing a hemolytic assay for RF were performed to determine the specificity of hidden 19S IgM RF. Sera from 14 children with JRA were separated by gel filtration at pH 4.05. Two were seropositive for RF and 12 were seronegative; the latter had high titer hidden 19S IgM RF. The IgM-containing fractions were preincubated with monomeric human IgG, rabbit IgG, or bovine IgG, and the complement-dependent hemolytic assay ws performed. The RF in the IgM fraction from the 2 seropositive patients were inhibited most strongly by rabbit IgG, whereas hidden RF in the IgM fraction of 9 seronegative patients were inhibited markedly by human IgG (homologous IgG equal to autologous IgG), poorly by rabbit IgG, and not at all by bovine IgG. Further inhibition studies with the hidden 19S IgM RF demonstrated inhibition by the human IgG1 subclass in all patients and only minimal inhibition by the IgG3 subclass in 3 patients. Inhibition with IgG1 Fc fragments produced by papain and thermolysin digestion demonstrated inhibition by only those fragments that contained the G1m (a) antigenic area which is found in the C gamma 3 homology area of the IgG1 molecule. These data indicate that hidden 19S IgM RF possibly circulate as immune complexes bound to the IgG1 molecule and the binding chiefly occurs in th G1m (a) homology area.

DNA in synovial fluid and the circulation of patients with arthritis

DNA levels were measured in synovial fluids and sera of 106 patients with rheumatoid arthritis (RA), osteoarthritis (OA), gout, pseudogout, and posttraumatic arthritis (TRA). In synovial fluids, the highest concentration was found in rheumatoid arthritis (mean +/- SE 18 +/- 3 microgram/ml for seropositive and 9 +/- 1 microgram/ml for seronegative variants), gout and pseudogout (17 +/- 3 microgram/ml). In contrast, the levels in patients with OA or acute TRA were very low: 0.8 +/- 0.1 microgram/ml an 1.1 +/- 0.2 microgram/ml, respectively. The differences between the means of the first disease group and OA or TRA is statistically significant. A similar pattern was observed for DNA levels in the circulation: in rheumatoid arthritis, the mean concentration was 135 +/- 28 ng/ml and 164 +/- 39 ng/ml for seropositive and seronegative RA, respectively. Again the levels in OA and TRA were much lower, 52 +/- 18 ng/ml and 0 ng/Ml, respectively. The latter are not significantly different from the mean levels of 95 normal, healthy controls (14 +/- 3 ng/ml), whereas the concentration of DNA in the serum of RA patients is significantly higher than in OA, TRA, or normal controls. Serial determinations of DNA and other criteria of disease activity (leukocytes and protein levels in synovial fluid, blood sedimentation rate) in individual patients revealed a strong correlation of elevated values with active episodes. THe results suggest that these parameters reflect tissue damage.