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

Clinical significance of anti-Ro antibodies in rheumatoid arthritis

The objective of our study was to determine the frequency of anti-Ro antibodies in patients with rheumatoid arthritis (RA), their clinical significance and possible serologic and genetic associations. Consecutive patients with RA (ACR '87) were studied. Other connective tissues diseases were excluded. Demographic characteristics, extra articular manifestations, and treatment were reviewed. Presence of leukopenia, thrombocytopenia, hypergammaglobulinemia, hypocomplementemia, and cryoglobulinemia were consigned. Rheumatoid factor (RF), antinuclear antibodies (ANAs), anti-Ro, and anti-La were determined by ELISA in all patients; and HLA-DR was determined by PCR and oligotyping. X-rays of the hands and feet were evaluated by Larsen's score. The study included 106 patients, 94 women and 12 men; mean age was 50.3 +/- 11.4 years, mean disease duration was 11.2 +/- 6.8 years. Main extra articular manifestations were subcutaneous nodules, xerophthalmia, and xerostomia; 75.5% of the patients were RF+. Anti-Ro antibodies were detected in 12.2% of the patients. When positive and negative anti-Ro patients were compared, no significant difference in any studied variable was observed. According to our results, anti-Ro antibodies lack clinical relevance in patients with RA.

Rheumatoid arthritis and connective tissue disorders: India and South-East Asia

With a few exceptions, there remains a paucity of good epidemiological studies from India and South-East Asia. The overall impression is that the prevalence of rheumatoid arthritis (RA) is slightly less compared with the West and follows a milder course. There may be differences in the articular expression of the disease with the wrist and forefoot less commonly affected than in Caucasian studies. Extra-articular manifestations and erosive change are less frequent and severe. HLA DR4 does not correlate with seropositivity and severity of RA. The prevalence of SLE may be less in the Indian subcontinent than in the West. However, recent indications are that in South-East Asia and the Pacific region the prevalence morbidity and mortality are higher than in developed countries. An improvement in socio-economic conditions may be accompanied by an improvement in the survival of patients with SLE.

The clinical significance of autoantibody profiles in patients with systemic lupus erythematosus

We have evaluated the autoantibody profiles in the sera of 117 patients with systemic lupus erythematosus (SLE) and compared and contrasted the clinical and laboratory features of the disease of patients segregated according to an autoantibody profile. Using this approach we are able to demonstrate that autoantibody profiles identified subsets of patients with SLE. Patients with a negative autoantibody profile had fewer clinical and laboratory features of their disease when compared to the other subsets of patients. In contrast, patients with profile A (anti-nDNA and/or anti-Sm antibodies) had a statistically significant increase in malar rash, renal and hematologic involvement and hypocomplementemia when compared to patients with a negative profile. Patients with profile B (anti-nRNP antibodies) had a clinical pattern of disease different from that of patients with profile A and had a statistically significant increase in Raynaud's phenomenon when compared to patients with a negative profile. Patients with profile C (anti-SSA and/or anti-SSB antibodies) had a statistically significant increase in lupus-related rashes and photosensitivity. None of the lupus patients reviewed in this study has profile D (antibodies to centromere and/or Scl-70), this profile being seen largely in patients with scleroderma or one of its variants. Both patients with profile E (anti-histone antibodies) had drug-induced lupus. We conclude that the use of autoantibody profiles defines subsets of patients with lupus that may have clinical, therapeutic and prognostic implications.

Detection of antibodies to DNA: a technical assessment

Antibodies to DNA can be found in the circulation of the majority of patients with Systemic Lupus Erythematosus (SLE). They are quite specific for this disease, which makes their detection an important diagnostic aid to the clinician. Fluctuations in the level of anti-dsDNA in an individual patient generally parallel the clinical state of that patient. Furthermore, the presence of anti-dsDNA may precede the diagnosis of SLE by more than a year. Four methods relevant for the measurement of anti-dsDNA antibodies are discussed in this paper: the ELISA, the indirect immunofluorescence test on Crithidia luciliae, the PEG assay, and the Farr assay. Each of these methods detects a part of the spectrum of anti-dsDNA antibodies present in the circulation of an individual patient. The ELISA is the most sensitive method, whereas the Farr assay is the most specific for SLE. However, with the latter method only antibodies of a relative high avidity for DNA are detected. Mild forms of SLE, where patients only have anti-dsDNA of a low avidity in their circulation, may easily be missed by this technique. Clinically, high avidity anti-dsDNA is related with the more frequent occurrence of nephritis, whereas low avidity anti-dsDNA antibodies are more often found in patients with central nervous system involvement.

IgG antibodies from patients with primary Sjögren's syndrome and systemic lupus erythematosus recognize different epitopes in 60-kD SSA/Ro protein

Five synthetic peptides corresponding to the N-, the C- and a central domain in 60-kD SSA/Ro protein were prepared and tested with sera from 112 patients with systemic lupus erythematosus (SLE), 55 with primary Sjögren's syndrome (pSS) and 29 with rheumatoid arthritis. Among these five fragments, one representing residues 21-41, was recognized by antibodies in 57% of pSS patients. Interestingly, this peptide was recognized by only a few (less than or equal to 7%) of SLE sera, while 63% of pSS sera and 46% of SLE sera tested in parallel possessed antibodies reacting in ELISA with purified 60-kD SSA protein. The ELISA results were compared with the pattern of reactivity obtained in immunodiffusion and immunoblotting. The results indicate that the sensitivity of ELISA using peptide 21-41 and pSS sera was in the same range as immunoblotting and higher than immunodiffusion. Thus the peptide 21-41 proved useful for the detection of anti-SSA antibodies in the sera of patients with pSS. Furthermore, a positive ELISA using peptide 21-41 could be of potential use to discriminate pSS with systemic features from SLE. The fact that peptide 21-41 is recognized by antibodies in pSS but only by very few SLE sera implies that different mechanisms are involved in the anti-SSA immune response in these two autoimmune diseases.

Mapping of epitopes on U1 snRNP polypeptide A with synthetic peptides and autoimmune sera

The ability of synthetic peptides encompassing almost the entire sequence of snRNP U1A polypeptide to be recognized in ELISA by sera of autoimmune patients was investigated. Sera from 18 patients with mixed connective tissue disease (MCTD), 145 with systemic lupus erythematosus (SLE) and 120 with other rheumatic autoimmune diseases were tested with 13 overlapping peptides. Among them, peptide 257-282 and, to a lower extent, peptide 1-11 were recognized by MCTD, SLE and Sjögren's syndrome sera. In contrast, peptide 35-58 was recognized by 94% of MCTD and only 19% of SLE sera. It did not react with any of the other patient sera. The ELISA results were compared with the pattern of reactivity observed in immunoblotting. The results indicate that peptide 35-58 probably contains a major epitope recognized by MCTD autoantibodies. It is noteworthy that in snRNP particles, this region of U1A interacts with RNA and presents only limited homology with the corresponding sequence 32-50 of U2B''.

Anti-dsDNA: choice of assay in relation to clinical value

Antibodies to DNA are quite specific for systemic lupus erythematosus (SLE) and occur in the majority of SLE patients. Therefore, their detection is an important diagnostic aid to the clinician. Detection of anti-dsDNA may precede the diagnosis of SLE by more than a year. Fluctuations in the level of anti-dsDNA in an individual patient may give important information on the clinical status of the patient. Four of the most important methods developed for the measurement of anti-dsDNA antibodies will be discussed in this paper: the Farr assay, the PEG assay, the indirect immunofluorescence test on Crithidia luciliae and the ELISA. They will also be compared with one commercially available (Farr) assay, the Amersham anti-dsDNA kit. Each method, detects a part of the spectrum of anti-dsDNA antibodies produced by a patient. The Farr assay is the most specific for SLE; however, milder forms of the disease in which patients have only low avidity anti-dsDNA may easily be missed by this technique. Clinically, high avidity anti-dsDNA is related more frequently to the occurrence of nephritis, whereas low avidity anti-dsDNA antibodies are found more often in patients with central nervous system involvement. Traditionally, SLE is considered an immune-complex disease, in which inflammatory processes are initiated by local deposition of DNA/anti-dsDNA complexes. More recently, a major role was thought to be played by crossreactions of anti-dsDNA with tissue constituents. Our current view, however, is that such a crossreactivity plays only a minor role; we postulate that binding to glomerular constituents is caused by anti-dsDNA antibodies complexed with DNA and histones.

Anti-Sm sera are misdetected by counterimmunoelectrophoresis. A critical analysis of CIE and western blotting on the detection of human antinuclear antibodies

The ability of CIE and Western blotting to detect antibodies against the Sm, RNP and SS/B antigens was tested in 84 sera from SLE patients. CIE and Western blotting gave identical results for anti-RNP and anti-SS/B; positivity was detected in the same sera regardless of the technique used and no new positive sera were found by Western blotting among those classified by CIE as not showing immunological relationship to the anti-RNP and anti-SS/B references. CIE detected only half of the anti-Sm that were positive by Western blotting. The inability of CIE to detect sera positive for anti-Sm could not be ascribed to specific features of the sera, such as low titer or the lack of antibodies to the Sm antigens B/B' and/or D. The identity of a number of these new anti-Sm sera was confirmed by the utilization of an in vitro translation test, where the 'cell-free' translation products were immunoprecipitated with the new positive anti-Sm sera.

Primary Sjögren's syndrome presenting as a case of sarcoidosis and a suspected pancreatic tumour

A 45 year old man, previously diagnosed as having sarcoid, presented with signs and symptoms of a pancreatic malignancy. An explorative laparotomy, however, showed only chronic pancreatitis. He was found to have a raised erythrocyte sedimentation rate, normocytic normochromic anaemia, renal insufficiency, hypergammaglobulinaemia, and a strongly positive rheumatoid factor and antinuclear antibody titre. Bilateral hilar lymph node enlargement was noted on chest x ray. Subsequently, the patient complained of xerostomia and keratoconjunctivitis sicca. Large lymphocytic infiltrates and a shift in the relative number of IgA bearing plasma cells in favour of IgG and IgM bearing plasma cells were seen in tissue obtained by sublabial salivary gland biopsy. A transbronchial lung biopsy and review of the biopsies of the pancreas, the lung, liver, and a lymph node all failed to show granulomatous disease. These findings strongly suggested a diagnosis of Sjögren's syndrome instead of sarcoidosis. This case shows the difficulty sometimes encountered in differentiating between sarcoid and systemic Sjögren's syndrome, and the value of a sublabial salivary gland biopsy.

A comparison of assays used for the detection of antibodies to DNA

In this paper we will briefly compare four assays in use in our institute for the measurement of antibodies to DNA: the anti-DNA ELISA, the PEG assay, the indirect immunofluorescence test on Crithidia luciliae and the Farr assay. Although with the use of sera from defined patients with systemic lupus erythematosus (SLE) quite good correlations were obtained between the various assays, these correlations were lost upon the use in routine screening of sera of undefined patients. It will be shown that the Farr assay has the highest specificity to systemic lupus erythematosus, whereas the ELISA and the PEG assay are the most sensitive methods. In its present form, however, the ELISA is not suited for the detection of IgM anti-DNA. Furthermore, this technique alone also detects DNA/-anti-DNA complexes present in sera or hybridoma culture supernatants.

Antibodies to DNA in patients with systemic lupus erythematosus. Their role in the diagnosis, the follow-up and the pathogenesis of the disease

In this paper an overview of the present knowledge on antibodies against DNA will be presented. Diagnostic, prognostic and pathogenic aspects of anti-DNA will be highlighted. Detection of antibodies to DNA in the circulation of a patient by an assay selective for high avidity anti-DNA is highly diagnostic for SLE. Anti-DNA of low avidity occurs in rheumatic diseases other than SLE as well, making detection of such antibodies of less diagnostic value. Furthermore, data will be presented that show that the anti-DNA ELISA in its present form is not suited as a diagnostic tool. Not only disease features of SLE vary from patient to patient, anti-DNA avidity does so too. A relationship between anti-DNA avidity and clinical features can be found: high avidity anti-DNA is more abundant in patients with nephritis, low avidity anti-DNA in patients with CNS involvement. Prognostically, a steady increase of the level of high avidity anti-DNA generally heralds an upcoming exacerbation in a patient. Furthermore, 85% of the patients who do not have SLE at the time (high avidity) anti-DNA is detected in their serum, will develop the disease within the next few years. It is noteworthy, that patients with only low avidity anti-DNA in their circulation develop a more mild form of SLE; the (low) avidity of their anti-DNA seldomly increases during the course of their disease. The relevance of anti-DNA to the pathogenesis of SLE still is a matter of debate. On the one hand, the association of parameters of anti-DNA that determine the size of the complexes formed with DNA is in favour of the classical hypothesis, which states that SLE is primarily an immune complex disease. On the other hand, recent data on crossreactions of anti-DNA with phospholipids, glycosaminoglycans and other (poly-negative) structures plead for a role of such crossreactivities in the pathogenesis of SLE.

Presence of antibodies to ubiquitin during the autoimmune response associated with systemic lupus erythematosus

Sera from patients with systemic lupus erythematosus (SLE) were shown to react with both ubiquitin and a synthetic fragment of it (residues 22-45) in an ELISA and with ubiquitin in immunoblotting experiments. Close to 80% of lupus patients possessed ubiquitin antibodies, whereas only 55% of them possessed native DNA antibodies, a marker of SLE. Less than 16% of patients with other rheumatic autoimmune diseases possessed antibodies to ubiquitin. Our results indicate that the combined measurement of antibodies to native DNA and to ubiquitin could appreciably increase the detection of SLE cases (up to 85% in our study). It is suggested that ubiquitin, a heat shock protein, could be involved in antibody formation against ubiquitin-protein conjugates present during cellular injury and that this represents a major characteristic of the autoimmune response in SLE.

Routine testing for antinuclear antibodies: a comparison of immunofluorescence, counterimmunoelectrophoresis and immunoblotting

We compared the classical immunofluorescence test (IFT) and counterimmunoelectrophoresis method (CIE) with the new immunoblotting technique (IBT) for the detection of antinuclear antibodies (ANA). Sera from 200 patients were tested in all three assays. Patients were classified as having either rheumatic disease including rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), mixed connective tissue disease (MCTD), primary Raynaud's phenomenon or nonrheumatic disease. Within these broad categories, we observed that IFT and IBT showed a more or less comparable sensitivity and specificity (IFT: 0.54 and 0.82, respectively; IBT: 0.39 and 0.79, respectively). The CIE method combines a high specificity (0.99) with an extremely low sensitivity (0.08). By combining positive results obtained by IFT and IBT, a higher specificity (0.97) but a diminished sensitivity (0.24) is obtained. As IBT allows simultaneous discrimination between ANA of different specificities, we also tested for a correlation between the presence of anti-Sm, anti-RNP and anti-SS-B and the disease category. Only anti-SS-B discriminated significantly between rheumatic- and nonrheumatic disease. Anti-RNP was found in 50% of the SLE patients and in 50% of the MCTD patients; anti-Sm in 17% of the SLE patients and 25% of the MCTD patients. Anti-SS-B was found in 33% of the SLE patients. However, predictive rates of these ANA were low: 0.37 (anti-RNP), 0.67 (anti-Sm) and 0.43 (anti-SS-B). We conclude that from a practical point of view IFT is the preferable assay to screen for the presence of ANA. To characterize ANA specificities, however, the IBT is far superior to the CIE technique.

Antinuclear antibodies in patients with systemic lupus erythematosus: a comparison of counterimmunoelectrophoresis and immunoblotting

Traditionally, the method used mostly to identify antinuclear antibody (ANA) specificities is the counterimmunoelectrophoresis technique (CIE), in which a salt extract of rabbit thymus powder (so-called extractable nuclear antigen or ENA) serves as the source of antigen. Recently, the immunoblotting technique (IBT) has been introduced in the serology of antinuclear antibodies. A nuclear extract of HeLa cells is generally used as antigen in this method. In this paper, we compared both methods using sera of patients with active systemic lupus erythematosus (SLE). Only anti-Sm, anti-RNP, and Anti-SSB were taken into consideration, as the former technique only allowed the identification of these specificities. Within these restrictions, we found that, of 77 patients with SLE, 21 had CIE-detectable antibodies in their circulation and 29 IBT-detectable antibodies. Anti-RNP and anti-SSB were detected more frequently with the CIE than with the IBT; anti-Sm, on the other hand, was detected more frequently with the IBT than with the CIE. Several significant correlations were found between incidences of measured antibody specificities and disease features. The presence of anti-RNP (both if measured with the IBT or with the CIE) was found to be negatively correlated with nephritis. If measured with the IBT, the presence of anti-Sm correlated negatively with hematological disorders, and the presence of anti-SSB correlated positively with renal involvement.(ABSTRACT TRUNCATED AT 250 WORDS)

Is anticardiolipin activity a cross-reaction of anti-DNA or a separate entity?

Putative cross-reactions between anti-DNA and anticardiolipin activities were studied using sera of different patients and a panel of monoclonal antibodies to DNA. Sera were obtained from patients with systemic lupus erythematosus, from patients with syphilis, and from heroin addicts who showed a biologic false-positive result on the serologic test for syphilis. While the patients with syphilis and the heroin addicts had elevated levels of anticardiolipin antibodies in their circulation, no reactivity with DNA was observed in these sera. Sera from systemic lupus erythematosus patients often showed both anti-DNA and anticardiolipin activity. Although a correlation between anti-DNA and anticardiolipin titers was found, this did not always result from cross-reactivity of the same population of antibodies. In fact, we observed a relationship between cross-reactivity and antibody avidity. Anti-DNA of high avidity to DNA showed little cross-reactivity with cardiolipin. Anticardiolipin activity in such sera was based on the presence of specific anticardiolipin antibodies. Anti-DNA of low avidity was found to cross-react with cardiolipin. Among monoclonal antibodies to DNA, we found that cross-reactions with cardiolipin were rare: only 6 of 55 anti-DNA clones produced antibodies that also reacted with cardiolipin.

The clinical relevance of antinuclear antibodies in connective tissue diseases

Detection of antinuclear antibodies (ANA) is of growing relevance in the management of connective tissue diseases (CTD). ANA are useful diagnostic tools, since most CTD have a peculiar ANA profile, characterized either by restricted specificities, abnormally high titers, or both. Furthermore, the study of the intimate structure and function of nuclear antigens, and of their corresponding antibodies may provide important insights to understand both origin and pathogenesis of CTD. Finally, the more or less close association of ANA levels and/or specificity with certain signs or symptoms of CTD is of increasing help to the clinician in the correct monitoring and management of CTD.