Antibodies to native and denatured deoxyribonucleic acid in systemic lupus erythematosus

Anti-dsDNA Testing Specificity for Systemic Lupus Erythematosus: A Systematic Review

BACKGROUND

Autoantibody specificity in autoimmune diseases is variable due to each patient's individual spectrum of autoantibodies and the inherent differences between detection methods and tests. Since false-positive results have downstream consequences, we conducted a comprehensive assessment of anti-double stranded DNA (anti-dsDNA) specificity from published studies of systemic lupus erythematosus (SLE).

METHODS

A systematic review (MEDLINE, Embase, Cochrane Central Register of Controlled Trials, and Database of Abstracts of Reviews of Effects) identified cross-sectional or case-control studies published January 2004 to August 2019, reporting anti-dsDNA test accuracy data in SLE. Study quality was assessed using Quality Assessment Tool for Diagnostic Accuracy Studies, version 2. A meta-analysis was conducted to estimate specificity by test method or named test where feasible.

RESULTS

Thirty studies were included covering 43 different tests. The Crithidia luciliae indirect immunofluorescence test (CLIFT) and fluorescence enzyme immunoassay methods are likely to be ≥ 90% specific (Euroimmun 97.8% (95% CI 96.2%-98.7%) 4 studies; EliA 94.7% (95% CI 91.7%-96.7%), 6 studies; CLIFT 98.7% (95% CI 96.7%-99.5%), 8 studies/7 tests]. For other test methods, specificity was not fully demonstrated to be ≥ 90% and/or the control group included healthy patients possibly overestimating specificity. More studies are required for NOVA Lite [96.0% (95% CI 87.2%-98.9%), 5 studies], chemiluminescence immunoassays [92.3% (95% CI 83.6%-96.6%), 6 studies/4 tests], multiplex immunoassays [89.3% (95% CI 86.1%-91.8%), 4 studies/2 tests], and Farr fluorescent immunoassays (no estimate, 2 studies). Specificity data reported for Farr radioimmunoassays [93.8% (95% CI 85.4-97.5%), 11 studies, 9 tests] and enzyme-linked immunosorbent assays [93.4% (95% CI 89.9%-95.7%), 15 studies/16 tests] lacked consistency.

CONCLUSION

Anti-dsDNA testing shows considerable variation in test specificity, with potential impact on the management of SLE patients. This review may help laboratory specialists and clinicians choose and interpret the appropriate anti-dsDNA test for their setting.

Precipitating anti-dsDNA peptide repertoires in lupus

Anti-double-stranded (ds)DNA autoantibodies are prototypical serological markers of systemic lupus erythematosus (SLE), but little is known about their immunoglobulin variable (IgV) region composition at the level of the secreted (serum) proteome. Here, we use a novel proteomic workflow based on de novo mass spectrometric sequencing of anti-dsDNA precipitins to analyse IgV subfamily expression and mutational signatures of high-affinity, precipitating anti-dsDNA responses. Serum anti-dsDNA proteomes were oligoclonal with shared (public) expression of immunoglobulin (Ig)G heavy chain variable region (IGHV) and kappa chain variable region (IGKV) subfamilies. IgV peptide maps from eight subjects showed extensive public and random (private) amino acid replacement mutations with prominent arginine substitutions across heavy (H)- and light (L)-chains. Shared sets of L-chain complementarity determining region 3 (CDR3) peptides specified by arginine substitutions were sequenced from the dominantly expressed IGKV3-20 subfamily, with changes in expression levels of a clonal L-chain CDR3 peptide by quantitative multiple reaction monitoring (MRM) paralleling the rise and fall of anti-dsDNA levels by Farr radioimmunoassays (RIA). The heavily mutated IgV peptide signatures of precipitating anti-dsDNA autoantibody proteomes reflect the strong selective forces that shape humoral anti-dsDNA responses in germinal centres. Direct sequencing of agarose gel precipitins using microlitre volumes of stored sera streamlines the antibody sequencing workflow and is generalizable to other precipitating serum antibodies.

Prozone-like phenomenon found in chemiluminescent enzyme immunoassay using magnetic particles for measurement of serum anti-single stranded DNA antibody titers: Definition and management

BACKGROUND

Serum anti-single stranded DNA antibody (anti-ssDNAab) is used as a marker for systemic lupus erythematosus. We found a 'prozone-like phenomenon,' which was different from an original prozone phenomenon, in chemiluminescent enzyme immunoassay using magnetic particles for the measurement of serum anti-ssDNAab titers. We investigated mechanisms of the prozone-like phenomenon and countermeasures to prevent it from being overlooked.

METHODS

This study examined 679 samples from patients tested for anti-ssDNAab titer at our hospital. In addition, the BF photometry OD value 2 (OD2), an index of optical density, was monitored simultaneously.

RESULTS

The undiluted samples with a prozone-like phenomenon showed extremely lower OD2. Those samples were able to be distinguished from other samples by setting OD2 criteria based on the 95% prediction interval. Significant differences (p < 0.05) were found in the titer ratios (ten-fold diluted against undiluted) between groups with >1.5 and other groups with <1.5 for the ratios of OD2.

CONCLUSIONS

We proposed two valuable methods to find a prozone-like phenomenon: one by setting OD2 criteria based on the 95% prediction interval and the other by analyzing the ratios both in titers and OD2 between undiluted and 10-fold diluted samples.

Biomarkers to guide clinical therapeutics in rheumatology?

PURPOSE OF REVIEW

The use of biomarkers in rheumatology can help identify disease risk, improve diagnosis and prognosis, target therapy, assess response to treatment, and further our understanding of the underlying pathogenesis of disease. Here, we discuss the recent advances in biomarkers for rheumatic disorders, existing impediments to progress in this field, and the potential of biomarkers to enable precision medicine and thereby transform rheumatology.

RECENT FINDINGS

Although significant challenges remain, progress continues to be made in biomarker discovery and development for rheumatic diseases. The use of next-generation technologies, including large-scale sequencing, proteomic technologies, metabolomic technologies, mass cytometry, and other single-cell analysis and multianalyte analysis technologies, has yielded a slew of new candidate biomarkers. Nevertheless, these biomarkers still require rigorous validation and have yet to make their way into clinical practice and therapeutic development. This review focuses on advances in the biomarker field in the last 12 months as well as the challenges that remain.

SUMMARY

Better biomarkers, ideally mechanistic ones, are needed to guide clinical decision making in rheumatology. Although the use of next-generation techniques for biomarker discovery is making headway, it is imperative that the roadblocks in our search for new biomarkers are overcome to enable identification of biomarkers with greater diagnostic and predictive utility. Identification of biomarkers with robust diagnostic and predictive utility would enable precision medicine in rheumatology.

Certain polyclonal antinuclear antibodies cross-react with the surface membrane of human lymphocytes and granulocytes

Five out of 24 human sera with antinuclear antibody (ANA) titers of 1250 or more contained ANA that bound in vitro to normal viable human mononuclear blood cells and granulocytes, but not to erythrocytes. The antibodies can be eluted off from the cell membranes and shown to possess ANA activity. Antinative DNA antibodies and lupus erythematosus factor were not recovered in eluates, indicating that they did not react with the cells. The cells absorbed 75%-87% of the ANA activity from three sera. ANA reacted with both T-lymphocyte-depleted and -enriched mononuclear cells. No or minimal amounts of ANA bound to mouse spleen cells in suspension; in contrast, the ANA eluted from human cells reacted with nuclei of smeared mouse spleen cells. The cross-reacting antibodies were predominantly IgG that bound well at 37 degrees C, and F(ab')2 fragments carried both activities. The ANA-binding plasma membrane antigen was resistant to trypsin and RNAse but was completely inactivated by glutaraldehyde. The data indicate that human leukocyte plasma membranes and cell nuclei from many species contain a cross-specific antigen. Alternatively, the antigen may be produced in the nucleus and somehow attach to the plasma membrane.

Binding of anti-DNA antibodies to oxidatively damaged DNA in spouses and relatives of patients with systemic lupus erythematosus

The prevalence of serum anti-DNA antibodies was evaluated by ELISA using oxidatively damaged DNA as antigen in 21 patients with systemic lupus erythematosus (SLE), in 9 spouses and in 15 first-degree relatives. These were compared with 12 healthy controls. There was no significant difference in the levels of serum antibodies detected between the group of spouses and normal controls with all results within the normal range of the assay. Binding of serum antibodies to the oxidatively damaged DNA was detectable in 12 (80%) of the relatives studied, and the range of values obtained overlapped significantly with the SLE patient group. The relevance of these antibodies to the immunopathology of SLE is unclear since they appear to be present in the absence of any clinical symptoms. However, they may be useful predictively as a marker for those individuals who are more likely to develop SLE.

The central role of chromatin in autoimmune responses to histones and DNA in systemic lupus erythematosus

To gain insight into the mechanisms of autoantibody induction, sera from 40 patients with systemic lupus erythematosus (SLE) were tested by ELISAs for antibody binding to denatured individual histones, native histone-histone complexes, histone-DNA subnucleosome complexes, three forms of chromatin, and DNA. Whole chromatin was the most reactive substrate, with 88% of the patients positive. By chi-square analysis, only the presence of anti-(H2A-H2B), anti-[(H2A-H2B)-DNA], and antichromatin were correlated with kidney disease measured by proteinuria > 0.5 g/d. SLE patients could be divided into two groups based on their antibody-binding pattern to the above substrates. Antibodies from about half of the patients reacted with chromatin and the (H2A-H2B)-DNA subnucleosome complex but displayed very low or no reactivity with native DNA or the (H3-H4)2-DNA subnucleosome complex. An additional third of the patients had antibody reactivity to chromatin, as well as to both subnucleosome structures and DNA. Strikingly, all sera that bound to any of the components of chromatin also bound to whole chromatin, and adsorption with chromatin removed 85-100% of reactivity to (H2A-H2B)-DNA, (H3-H4)2-DNA, and native DNA. Individual sera often bound to several different epitopes on chromatin, with some epitopes requiring quaternary protein-DNA interactions. These results are consistent with chromatin being a potent immunogenic stimulus in SLE. Taken together with previous studies, we suggest that antibody activity to the (H2A-H2B)-DNA component signals the initial breakdown of immune tolerance whereas responses to (H3-H4)2-DNA and native DNA reflect subsequent global loss of tolerance to chromatin.

Detection of anti-double and anti-single stranded DNA antibodies in chronic liver disease: significance of anti-double stranded DNA antibody in autoimmune hepatitis

Anti-DNA antibodies were determined by an enzyme-linked immunosorbent assay in 116 patients with chronic liver disease consisting of 21 cases of autoimmune hepatitis (AIH), 17 of primary biliary cirrhosis (PBC), and 78 of non-autoimmune-type of chronic liver disease. The assay was also performed on 83 patients with collagen disease, as a control group. Anti-double stranded DNA antibody (anti-dsDNA) was detected in 10/21 (48%) of the AIH patients and in 3/17 (17%) of the PBC patients, but not in those with other liver diseases. In contrast, anti-single stranded DNA antibody (anti-ssDNA) was positive not only in AIH and PBC, but also in those with non-autoimmune-types of chronic liver disease. Follow-up liver histology disclosed that the 2 patients with AIH who were positive for anti-dsDNA developed liver cirrhosis, whereas the 4 patients who were negative for anti-dsDNA, and those who showed a disappearance of anti-dsDNA following corticosteroid therapy, improved from chronic active to chronic persistent hepatitis.

Novel monoclonal antibodies to double stranded DNA that require Ca2+ or Mg2+ for their binding

Murine monoclonal antibody (MoAb) 2B5 (IgG2aK) was obtained by its binding on a solid phase to double-stranded (ds) DNA from one of the mutant CBA/K1(CBA/K1Jms-1prcg/1prcg) mice which were recently found, in our institute, to develop lymphadenopathy associated with the production of anti-double-stranded (ds) antibodies. MoAb 2B5 was highly specific for dsDNA, as shown by enzyme-linked immunosorbent assay (ELISA). The dsDNA binding of 2B5 was decreased dose-dependently by the chelating agent EDTA, being lost completely with 2.5-5.0 mM EDTA, whereas dsDNA on the solid phase remained intact after incubation with EDTA. Addition of Ca2+ or Mg2+ to antibody in culture supernatant that had lost dsDNA binding activity by dialysis against Ca2+ and Mg(2+)-free buffer restored its binding with dsDNA to the original level, indicating that MoAb 2B5 requires Ca2+ or Mg2+ for its binding with dsDNA. It is unknown whether MoAb 2B5 recognizes new conformational epitopes created in the presence of Ca2+ or Mg2+, but this MoAb should be useful in studies on the modes of interaction of DNA with antibodies and DNA-binding proteins.

Localization of nucleolar chromatin by immunocytochemistry and in situ hybridization at the electron microscopic level

Nucleoli are the morphological expression of the activity of a defined set of chromosomal segments bearing rRNA genes. The topological distribution and composition of the intranucleolar chromatin as well as the definition of nucleolar structures in which enzymes of the rDNA transcription machinery reside have been investigated in mammalian cells by various immunogold labelling approaches at the ultrastructural level. The precise intranucleolar location of rRNA genes has been further specified by electron microscopic in situ hybridization with a non-autoradiographic procedure. Our results indicate that the fibrillar centers are the sole nucleolar structures where rDNA, core histones, RNA polymerase I and DNA topoisomerase I are located together. Taking into account the potential value and limitations of immunoelectron microscopic techniques, we propose that transcription of the rRNA genes takes place within the confines of the fibrillar centers, probably close to the boundary regions to the surrounding dense fibrillar component.

Temporary breakdown of immunological tolerance to dsDNA and nucleohistone antigens in rabbits infected with rinderpest virus

The rabbit-passaged L strain of rinderpest virus (RV) causes the transient induction of anti-nuclear antibodies (ANA) in rabbits. It has been shown by an indirect immunofluorescence test that the target antigens of these ANA are DNA and/or DNA-histone complexes (nucleohistone). Here detailed examinations of the target antigens were carried out by ELISA, and it was revealed that rabbit sera contained three types of antibodies: antibodies reacting equally with both dsDNA and ssDNA; those reacting with ssDNA alone; and those reacting with nucleohistone. Epitopes recognized by the third type consisted of complexes of dsDNA and H2A + H2B or of dsDNA and H2B. All types of antibodies were antigen specific. Since the diversity of ANA among experimental rabbits was large, it was suggested that genetic background is important in the induction of anti-dsDNA antibodies in this system. Moreover, early induction of antibodies to nucleohistone and the rapid disappearance of ANA suggest that B cell proliferation/maturation for continuous production of ANA requires factors other than RV infection. This system may help elucidate the mechanisms of ANA induction and the development of autoimmune diseases.

A monoclonal anti-double-stranded DNA autoantibody binds to a 94-kDa cell-surface protein on various cell types via nucleosomes or a DNA-histone complex

A crude supernatant of hybridoma secreting a monoclonal anti-double-stranded (ds)DNA antibody (PME77 mAb), used to stain fibroblasts (CVI cells) in immunofluorescence, gives a punctuated staining of variable intensity. We had suggested that anti-DNA antibodies bind to cell-surface protein(s) of several cells. When the mAb of this crude supernatant was purified on a dsDNA-cellulose column and a histone-Trisacryl column, the mAb no longer bound to the cell surface. Only when dsDNA plus purified histones was added to the purified antibody did the immune complex strongly and uniformly stain again the cell surface of CVI cells. No significant staining was observed if either DNA or histones were omitted. A signal 94-kDa protein from membrane fractions of CVI, Raji, and RINm cell lines was visualized in immunoblots when mAb-DNA-histone complexes were applied to the nitrocellulose strips. No polypeptide was seen if one component was omitted. This 94-kDa protein behaved like a plasma membrane protein since it required the use of detergent to be solubilized and was quantitatively recovered in the Triton X-114 detergent-rich phase. Moreover, a brief treatment of living cells with trypsin cleared off this protein. Purified nucleosomes could be substituted to DNA-histone complexes, giving rise to identical results. Finally, purified polyclonal anti-DNA antibodies from sera of systemic lupus erythematosus patients labeled a 94-kDa protein provided that DNA-histone complexes were added. Anti-DNA autoantibodies could be pathogenic when they are bound to nucleosomes.

Calibration of target amounts of DNA in hybridization experiments using monoclonal anti-nucleoside antibodies

Two anti-nucleoside monoclonal antibodies (A-16 and G-K21) were raised after immunizing mice with adenosine or guanosine coupled to bovine serum albumin by periodate oxidation. They were selected for their ability to detect these immunogens and single-stranded DNA in an enzyme-linked immunosorbent assay test. The antibodies were purified from ascitic fluids, their isotypes were determined and their ability to detect DNAs and RNAs on nitrocellulose membranes was tested. They belonged to the IgG1 subclass and were both able to recognize picogram amounts of single-stranded DNAs on nitrocellulose sheets, whatever the origin of the nucleic acid, but were unable to detect RNA efficiently. The same monoclonal antibodies were used to estimate minute amounts of target staphylococci DNAs to permit standardization of non-radioactive hybridization experiments for detection of antibiotic resistance genes.

Structure and function of anti-DNA autoantibodies derived from a single autoimmune mouse

Four monoclonal anti-DNA antibodies derived from a single autoimmune MRL/lpr mouse were studied. Three of these antibodies showed similarities in DNA binding; the fourth had a much higher specific activity for single-stranded DNA and, in addition, was unique in binding double-stranded DNA and cardiolipin. Complete nucleotide sequences of heavy- and light-chain variable regions demonstrated that all four antibodies are clonally related. The sequences also showed numerous somatic mutations, the distribution of which suggests that positive selection by antigen operated on these clonally related autoantibodies.

Thymine and guanine base specificity of human myeloma proteins with anti-DNA activity

To further our understanding of the molecular basis of DNA-autoantibody interactions, we have characterized the specificities of three IgG human myeloma proteins that bind DNA. We measured their binding to synthetic single- and double-stranded homopolynucleotides, random and alternating copolymers, oligonucleotides, and nucleotides or nucleosides conjugated to non-nucleic acid carriers. All three antibodies bound single-stranded nucleic acids, including both polyribonucleotides and polydeoxyribonucleotides. They varied in relative affinities for polynucleotides of varying base composition. Polymers containing the purines guanine or hypoxanthine and/or the pyrimidine thymine were most reactive with all three proteins. A myeloma protein that reacted with poly(G), poly(I), or poly(dT) also bound to the corresponding nucleosides or nucleotides conjugated to bovine serum albumin. None of the antibodies reacted with base-paired double-helical polynucleotides (double-stranded RNA, RNA-DNA hybrid or double-stranded DNA). The results indicate that base specificity is prominent in their reactions and that the accessible epitopes in single-stranded polynucleotides become masked upon base pairing in double-stranded helices. These findings suggest a model in which positions N1 and O6 of guanine and hypoxanthine and N3 and O4 of thymine interact with amino acids of the antibody-combining site.

Antibodies to DNA

Antibodies that recognize specific conformational variations of DNA structure provide sensitive reagents for testing the extent to which such conformational heterogeneity occurs in nature. A most dramatic recent example has been the development and application of antibodies to left-handed Z-DNA. They provided the first identification of Z-DNA in fixed nuclei and chromosomes, and of DNA sequences that form Z-DNA under the influence of supercoiling. Antibodies have also been induced by chemically modified DNA and by synthetic polydeoxyribonucleotides that differ from the average B-DNA structure. These antibodies recognize only the features that differ from native DNA. In most experiments, native DNA itself is not immunogenic. Antibodies that do react with native DNA occur in sera of patients with autoimmune disease, but even monoclonal anti-DNA autoantibodies usually react with other polynucleotides as well. Anti-DNA antibodies, especially those of monoclonal origin, provide a model for the study of protein-nucleic acid recognition.

DNA affinity column chromatography: application in the isolation of distinct antibody populations from SLE sera

An improved method was developed for purification of anti-DNA antibodies by single-stranded DNA (ssDNA), or double-stranded DNA (dsDNA) affinity column chromatography. The effectiveness of this method was examined by measuring the recoveries and purifications of various monoclonal and polyclonal antibodies. Results showed that this method gave good recoveries and purifications of anti-DNA antibodies. Furthermore, by this method, it was possible to isolate antibody populations with distinct specificities from polyclonal antibodies, as shown by enzyme linked immunosorbent assay (ELISA). Therefore, this method should be useful for characterization of polyclonal antibodies in the sera of patients with systemic lupus erythematosus (SLE) as well as of autoimmune lupus mice.

The fine specificity of IgG antiguanosine antibodies in systemic lupus erythematosus

The antigen specificity, isotype, and subclass of antinuclear antibodies may be related to their pathogenicity in systemic lupus erythematosus (SLE). Our laboratory found that IgG antibodies that bound the nucleoside, guanosine, occurred frequently in SLE patients. In contrast, sera from healthy subjects contained IgM but not IgG antiguanosine antibodies. The present studies were designed to characterized the fine specificity of IgG antiguanosine antibodies in SLE and compare them with IgM antiguanosine antibodies in normal sera. Serum antinuclear antibodies from six healthy subjects and six SLE patients were isolated by affinity binding to guanosine and measured by an enzyme-linked immunosorbent assay (ELISA). IgM in normal sera, and both IgM and IgG in SLE sera bound guanosine. IgM antiguanosine antibodies in normal sera were polyspecific and bound other nucleosides and 1-methylguanosine but not denatured DNA (ssDNA). In contrast, IgG antiguanosine antibodies from the SLE patients bound guanosine and ssDNA but not other nucleosides or 1-methylguanosine. SLE IgM antiguanosine antibodies had the same fine specificity and bound guanosine and ssDNA but not any of the other nucleosides. These results suggest that SLE IgG and IgM antiguanosine antibodies have fine specificity in contrast to the polyspecific IgM antibodies in normal sera. In addition, subclass analysis indicated that all SLE patients had either IgG1 or IgG3 subclass of antiguanosine antibodies that bind complement. Characterizing the isotype, subclass, and fine antigen specificity of antiguanosine antibodies should assist in evaluating their potential pathogenicity in SLE.

Anti-DNA antibodies: the choice of assays for routine diagnostic work

Sixty-six sera from 23 patients with systemic lupus erythematosus (SLE), 26 sera from patients with rheumatoid arthritis (RA), and 22 sera from normal healthy subjects were tested for the presence of antibodies against native (ds) DNA by the Crithidia luciliae immunofluorescence test and by the Farr assay, and for the presence of antibodies against denaturated (ss) DNA by the enzyme-linked immunosorbent assay (ELISA). Anti-dsDNA antibodies were detected in 57% of the SLE patients by the Crithidia test and in 65% by the Farr assay. Two of the RA sera were positive in the Crithidia test, whereas all were Farr negative. Anti-ssDNA antibodies of IgG class could be detected in 74% of the SLE patients and in none of the RA sera, while anti-ssDNA antibodies of IgM class were found in 26% of the SLE patients and in one RA serum. There was a good correlation between the results of the Farr assay and the IgG-anti-ssDNA ELISA but no agreement was found between the results of the Farr assay and the Crithidia test. We also measured the amount of C-reactive protein (CRP) in the sera but no correlation was seen between the levels of CRP and anti-DNA antibodies. We conclude that the demonstration of anti-ssDNA antibodies of IgG class is a good screening method in the diagnosis of SLE, and that antibodies against native DNA should be determined, preferably both by the Crithidia test and the Farr assay to confirm the diagnosis and in the follow-up of the patients.

Characterization of a human monoclonal IgM with antibody activity to dsDNA

We report here the characterization and fine specificity of a human monoclonal IgM lambda reacting with double stranded DNA. The purified IgM and its Fab fragment bind to DNA in the Farr or Crithidia lucilae assays as well as in an immunoenzymatic test. In the latter case, binding was inhibited by native DNA, by DNA alternative co-polymers and by some homopolymers only, but not by monodeoxyribonucleotides and ribonucleotides. Since cardiolipin and phosphatidic acid were good inhibitors, these data suggest that the monoclonal IgM reacts with the sugar phosphate backbone of deoxyribonucleic acids. Interestingly, the patient was affected with both Waldenström's macroglobulinaemia and pernicious anaemia without any symptoms of systemic lupus erythematosus.

Effect of corticosteroids on serum antinuclear antibodies in man

The effect of prednisone on serum levels of IgG antibodies to viral and bacterial antigens was measured and compared to its effect on IgG antibodies to nuclear antigens in 8 patients with systemic lupus erythematosus. Prednisone at 15-80 mg/day (mean 55 mg/day) for 14-30 days (mean 19 days) lowered the serum IgG by an average of 22% (p less than 0.005). An even greater reduction in IgG antinuclear antibodies occurred (mean 43%, p less than 0.001) including responses to double stranded DNA, single stranded DNA, and the nucleosides, adenosine, guanosine, cytidine and thymine riboside. In contrast, there was no alteration in serum IgG antibody levels to influenza virus vaccine and pneumococcal vaccine antigens. These results suggest that prednisone has a selective effect on the expression of autoimmunity which may, in part, be responsible for its clinical efficacy in systemic lupus erythematosus.

Anti-phospholipid antibodies and biological false positive serological test for syphilis in patients with systemic lupus erythematosus

Utilizing a newly developed solid phase enzyme immunoassay for the detection of anti-phospholipid antibodies, we found that 41.7% of sera from patients with active systemic lupus erythematosus (SLE) had the anti-cardiolipin antibody and 22.7% of sera were positive for the anti-phosphatidylinositol (PI) antibody. But antibodies to lecithin, cephalin and sphingomyelin were rarely found in this assay. We also examined antibodies to the VDRL (Venereal Disease Research Laboratory) antigen which consists of cardiolipin-cholesterol-lecithin mixtures. The incidence of the anti-VDRL antibody in the IgG class was 29.2% and 25% in the IgM class, and the magnitude of these antibodies correlated well with the incidence of biological false positive serological test for syphilis (BFP-STS), but no association between the anti-VDRL antibody titre and the anti-cardiolipin antibody titre was observed. Furthermore, the cardiolipin binding activity of sera from patients with SLE was inhibited by DNA and poly(I), both of which have polynucleotide backbones structurally similar to the phosphodiester groups of cardiolipin. On the contrary, these polynucleotides failed to inhibit the PI and the VDRL binding of SLE sera. These observations may support the concept that the anti-cardiolipin antibody in sera from patients with SLE might be a part of the anti-DNA antibodies, which are serologically polymorphic in that they can react with a variety of polynucleotides, but differ from the BFP reactors.

Cross-reactivity of anti-DNA antibodies with proteoglycans

Ten sera of patients with systemic lupus erythematosus (SLE) were tested in an enzyme linked immunosorbent assay for their ability to react with glycosaminoglycans, constituents of proteoglycans, in relation to their anti-DNA reactivity. The SLE sera reacted with hyaluronic acid and chondroitin sulphate and this reactivity correlated with the anti-DNA activity of these sera. By contrast, sera obtained from patients with other autoimmune diseases or normal sera lacked any of these reactivities. Anti-DNA antibodies purified by affinity chromatography with either oligo dT cellulose or Cibracon blue F3Ga Sepharose reacted with DNA as well as with hyaluronic acid. The cross-reactivity of anti-DNA antibodies could be confirmed by the reaction of a mouse monoclonal anti-DNA antibody with DNA, hyaluronic acid, and chondroitin sulphate. This pattern of cross-reactivities of anti-DNA antibodies suggests that several compounds can function as antigenic targets for these antibodies provided that their structures contain repeating negatively charged groups.

Immune complex glomerulonephritis in hydralazine-induced SLE

Renal disease, a major feature of systemic lupus erythematosus (SLE), rarely occurs in drug-induced SLE. Immune complex glomerulonephritis has been demonstrated in a few cases of SLE following procainamide or anticonvulsant therapy but has not been documented in association with hydralazine-induced SLE despite the recognition of this syndrome 30 years ago. We report the clinical and renal pathologic findings in a patient with hydralazine-induced lupus nephritis and review the renal pathologic material in earlier reports of hydralazine-induced SLE.

Specificity of anti-nucleoside antibodies in systemic lupus erythematosus

The titer of IgG antinucleoside antibodies in the sera of 162 individuals was determined by an enzyme-linked immunosorbent assay. The nucleosides used in the assay were adenosine, cytidine, guanosine, and thymine-riboside conjugated to human serum albumin. The specificity of IgG antinucleoside antibodies was indicated by appropriate reduction in antibody binding after solid-phase adsorptions of antibody with specific immobilized nucleoside conjugates. Disease-associated increases in serum IgG antibodies to cytidine and guanosine but not to adenosine or thymine-riboside occurred in patients with systemic lupus erythematosus (SLE). The epitope density of nucleosides in the conjugates and differences in the sensitivity of each nucleoside assay were not responsible for disease-associated IgG antinucleoside antibody responses. These findings support a possible pathogenic role for cytidine and guanosine as antigens or crossreactive antigenic determinants in some patients with SLE.

Suppression of NZB/NZW murine nephritis by administration of a syngeneic monoclonal antibody to DNA. Possible role of anti-idiotypic antibodies

Suppression of circulating antibodies to double-stranded DNA was achieved in NZB/NZW f1 female mice by repeated administration of an IgG2a monoclonal antibody to DNA. Deaths from nephritis were delayed; glomerular deposition of IgG and of the cationic IgG DNA antibodies characteristic of murine lupus nephritis were diminished. Quantities of circulating antibodies to single-stranded DNA were not reduced compared with untreated or IgG myeloma-treated control mice. Antibodies directed against the monoclonal anti-DNA appeared in the circulation of treated mice after three inoculations of the idiotype. Those antibodies did not react with another monoclonal anti-DNA of the same allotype. One monoclonal anti-idiotypic antibody was obtained in hybridoma cultures derived from a spleen of a treated mouse. Cross-reactive or common idiotypes were found in 30-50% of NZB/NZW f1 sera and monoclonal DNA antibodies. Deletions of portions of the spectrotype of antibodies to DNA were found in sera containing anti-idiotypic antibodies, suggesting suppression of clones producing antibodies with isoelectric points similar to that of the immunizing idiotype. Deletions of some of the anti-idiotypic antibodies also occurred as the mice aged. Rheumatoid factors were not detectable in any sera. Therefore, administration of an antibody to DNA bearing an idiotype occurring with high frequency in NZB/NZW f1 females resulted in relatively specific suppression of the antibody response to double-stranded DNA, as well as suppression of nephritis. Reduction of anti-DNA synthesis by anti-idiotypic antibodies may have been an important suppressive mechanism. Experiments are in progress to test this hypothesis.

Antibodies to nucleic acids in systemic lupus erythematosus and rheumatoid arthritis patients and their relatives

Sera of systemic lupus erythematosus (SLE) patients contain antibodies to double-stranded and single-stranded DNA while antibodies found in rheumatoid arthritis sera are specific mainly to single-stranded DNA. Anti-RNA antibodies in the both cases are directed against double-stranded RNA and belong to the IgM class while anti-DNA antibodies are IgG. Genetic variance analysis based on family correlations suggests that the synthesis of antibodies to DNA is subject to different modes of gene regulations in systemic lupus erythematosus and rheumatoid arthritis patients. In the case of SLE, a high degree of genetic determination is demonstrated, due mainly to the X-chromosomal component of the general phenotypic variance. The failures in the immunoregulation system that are responsible for anti-RNA antibody production are rather similar in the two groups of patients and involve a combination of environmental and autosomal factors.

Monoclonal autoantibody directed toward histone and capable of inducing LE cell formation

LE cell formation is one feature of systemic lupus erythematosus exhibited by virtually all mice of the NZB/NZW strain and is the result of accumulation of antibodies directed against components of cell nuclei. A hybrid cell line which produces antibodies capable of inducing LE cell formation in vitro has been isolated in a hybridoma fusion using the splenocytes of unimmunized NZB/NZW mice. These monoclonal autoantibodies provide an intense staining of the chromatin in cells of a number of divergent species and tissues. They bind strongly to the histone rich (2 M NaCl) fraction of extracted, isolated nuclei. Further analyses using the antibodies in immune precipitations and in antibody labeling of capillary blots on nitrocellulose sheets of calf thymus histone demonstrate that the antibodies are directed against histones and are capable of reacting with H1, H2a, H2b, H3, and H4 histones individually. In contrast to human autoantibodies with histone specificity, no cross-reactivity of this monoclonal autoantibody with the lymphocyte surface could be detected by either immunofluorescence or immunoelectron microscopy.

Antibodies cross-reactive with DNA and cardiolipin in patients with systemic lupus erythematosus

Using a modified solid phase radioimmunoassay (RIA), sera from 11 patients with systemic lupus erythematosus (SLE) that had high DNA binding activities were analysed for their ability to cross-react with phospholipids. Polyspecific anti-DNA antibodies that reacted with both ssDNA and dsDNA had the ability to cross-react with phospholipids, especially cardiolipin. The relationship between biological false-positive serological tests for syphilis (BFP-STS) and the magnitude of serum anti-DNA antibody levels is also discussed.

Generation and characterization of three murine monoclonal nucleotide binding anti-ssDNA autoantibodies

Three murine monoclonal anti-ssDNA autoantibodies have been produced by fusion of spleen cells from NZB/NZW F1 hybrid mice with Sp 2/0-Ag 14 murine myeloma cells. Specificity studies characterizing monoclonal anti-ssDNA autoantibodies revealed binding patterns for nucleotides. Clone E-4-1 showed preferential binding with mono-, di- and polyguanosine. Clones E-4-4 and E-11-1 specifically bound mono-, di- and polythymidine. Results of inhibition studies indicated an order of reactivity for each monoclonal autoantibody: polynucleotide greater than dinucleotide greater than mononucleotide. In a fluorescence immune assay, using aminonaphthyl derivatives of nucleotides, all three monoclonal antibodies exhibited a low affinity (5 x 10(4)-10(5) M-1) for the homologous mononucleotides. The affinity of clone E-4-1 increased approximately 10-fold when a dinucleotide derivative was used relative to a mononucleotide fluorescent ligand.

Monoclonal autoantibodies: an approach to studying autoimmune disease

Hybridoma technology has paved the way for new insights into mechanisms of autoimmunity and autoimmune disease. Autoantibodies and autoantigens can now be studied at the level of the individual molecule. The specificity of the autoimmune reaction, as well as its pathogenetic role in disease, may be more accurately assessed. Monoclonal autoantibodies which bind to red blood cells, IgG, DNA, RNA and ribonucleoprotein complexes have been prepared by several groups of investigators. The initial molecular and functional characterization of these immunoglobulins and their corresponding antigens is described.

Specificity in systemic lupus erythematosus of antibodies to double-stranded DNA measured with the polyethylene glycol precipitation assay

Recently, a new radioimmunoassay--the polyethylene glycol (PEG) assay--was introduced to measure antibodies to double-stranded (ds) DNA. In this method, polyethylene glycol precipitation of formed 3H-DNA/antiDNA complexes is used instead of the ammonium sulfate precipitation used in the Farr assay. In contrast to the Farr assay, with which only high-avidity antibodies to dsDNA are detected, the PEG assay also reportedly measures anti-dsDNA of relatively low avidity. We studied whether this gain in antibody measurement results in loss of specificity for systemic lupus erythematosus. When the PEG assay was applied to a selected panel of 440 sera from patients with various well-defined autoimmune diseases and to a group of 197 normal human control sera, matched sex and age to the patients, the method was found to be fairly specific for systemic lupus erythematosus, although the sera from some patients with myasthenia gravis and some with autoimmune liver disease were also found positive. Screening of 352 additional serum specimens, sent to our laboratory for diagnostic reasons, revealed that, with the PEG assay, an extra population of relatively low-avidity antibodies to dsDNA--missed by the Farr assay--was detected. Upon clinical evaluation, we found that the patients in whom such antibodies were detected generally fulfilled a number of the preliminary criteria of the American Rheumatism Association for systemic lupus erythematosus, but that this diagnosis often was not made. We claim that the presence of low-avidity antiDNA characterizes a milder form of the disease in which patients often show only a single clinical feature of the disease. We conclude that results of the PEG assay add valuable diagnostic and clinical information to results obtained by the Farr assay.

Monoclonal murine anti-nucleic acid antibody with double-stranded specificity

The NZB/NZW F1 murine model for the autoimmune disease systemic lupus erythematosus (SLE) has been employed in somatic cell hybridizations to develop hybridoma autoantibodies with double-stranded (ds) DNA specificity. Monoclonal anti-DNA antibodies from one hybridoma cell line were purified and analysed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and isoelectric focusing. Results of comparative binding studies with tritiated [3H]-colicin E1 plasmid DNA probes suggested preferential binding for the native DNA conformation relative to single-stranded DNA. [3H]dsDNA binding was inhibited by several ribohomopolymers (poly G, U and I) but not by free nucleotides, indicating that the phosphodiester-ribose backbone may contribute to the binding specificity of the clonotype.

Binding specificity of a monoclonal anti-DNA antibody

To investigate the interaction of DNA and anti-DNA antibodies in the immune complex disease of systemic lupus erythematosus, the fine specificity of binding of a monoclonal anti-DNA antibody was determined. This antibody, termed Cll, was derived from the fusion of spleen cells from an autoimmune MRL-lpr/lpr mouse with the myeloma cell line M45. In a solid-phase ELISA assay to measure anti-DNA activity, Cll showed preference for single stranded compared to double stranded DNA of animal origin. The Cll antibody also bound some deoxyribohomopolymers as well as ribohomopolymers, but failed to bind synthetic DNA duplexes. Defined size oligonucleotides with a size range of 2-(12-18) failed to inhibit the binding of Cll to single stranded DNA. This pattern of binding is consistent with the recognition of a unique structural determinant that can be represented by a variety of nucleic acids. The absence of antigenic activity among the oligonucleotides suggests that an extended polynucleotide structure is required for antibody binding, possibly because of a bivalent or 'monogamous' mode of interaction. The binding properties of Cll further suggest that its ability to participate in immune complex formation may be limited by the nature of the available DNA antigen.

Autoantibodies to nucleosomal proteins: antibodies to HMG-17 in autoimmune diseases

The relative amounts of autoantibodies against defined nucleosomal proteins present in serums from patients with systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and mixed connective tissue disease (MCTD) have been examined by an enzyme-linked immunoassay. Autoantibodies to nucleosomal proteins were detected in 45 percent of the patients with SLE, 18 percent of the MCTD patients, and none of the RA patients. The results suggest that, in SLE, antibodies are formed against a subset of nucleosomes which contain protein HMG-17.

Specificity of mouse hybridoma antibodies to DNA

Utilizing the somatic cell hybridization technique, we established 12 clones of mouse hybridoma from MRL/Mp-lpr/lpr(MRL/1) and NZB X NZW(B/W F1) mice, which produce antibodies reacting mainly with ssDNA (anti-ssDNA) and 2 clones from B/W F1 mice, which produce antibodies reacting with both ssDNA and dsDNA (anti-ss/dsDNA). By means of a competitive inhibition radioimmunoassay with synthetic polynucleotides, the anti-ssDNA antibodies were classified into 5 types, in terms of the DNA base specificity. The anti-ss/dsDNA antibodies had polyspecific reactivity to a wide range of polynucleotides, including synthetic RNA.

Fluorescent nucleotides: application in a fluorescence immune assay

A fluorescence immune assay designed to measure anti-nucleotide antibody activity is described based on the synthesis of a fluorescent nucleotide probe possessing a low fluorescence quantum yield when free in aqueous solution (neutral pH). The fluorophore, AmNS (1-naphthylamine-5-sulfonic acid), was covalently conjugated to various phosphate derivatives of nucleotides through carbodiimide activation to form the fluorescent probe. The quantum yield (phi) of the fluorescent nucleotide in solution (neutral pH) was approximately 0.025 based on an excitation maximum of 320 nm and an emission maximum of 460 nm. Anti-nucleotide antibodies elicited in rabbits and mice served as standard immunological reagents in development of the fluorescence assay. Upon binding of an AmNS-nucleotide conjugate with homologous anti-nucleotide antibodies, the fluorescence quantum yield of the conjugate was significantly enhanced (12-35 x). Fluorescence enhancement was not obtained upon incubation of the fluorescent probe with normal Ig, non-immune rabbit sera and murine ascites fluid, or bovine and rabbit serum albumin. Nucleotide inhibition reactions were quantitatively measured in the fluorescence assay. Nucleotide binding results obtained with the fluorescence assay were correlated with a modified radioimmune Farr assay.