In vivo ANA is a fixation artifact: nucleosome-complexed antinucleosome autoantibodies bind to the cell surface and are internalized

It has been suggested that binding of anti-double-standed DNA antibodies to cell surfaces, followed by internalization and nuclear binding (so called in vivo ANA) is of pathophysiological significance for tissue damage in systemic lupus erythematosus. We have shown before that pathogenic antinuclear antibodies complexed to nucleosomal antigens can bind to heparan sulfate in the glomerular basement membrane in vivo. Because nucleosomes are also reported to bind to the cell surface, we hypothesized that in vivo ANA is a property of antinuclear antibodies bound to nucleosomal antigens. Therefore, we studied three antinucleosome monoclonal antibodies (mAb) that exhibit in vivo ANA as seen by immunofluorescence in mice inoculated intraperitoneally with the hybridoma producing the mAb. The same mAb complexed to nucleosomal antigens after intravenous injection into mice induced in vivo ANA, in contrast to purified noncomplexed mAb. To study this in more detail, we incubated complexed mAb with various cell lines and found binding to the cell surface and subsequent internalization into cytoplasmic vesicles. However, no binding to the nucleus was observed by immunoelectron microscopy (IEM) and confocal laser microscopy. Noncomplexed mAb did not bind to the cell surface. Next, from mice bearing the hybridomas producing the mAb intraperitoneally, a small part of the kidney was snap frozen in liquid N2, fixed with acetone, and studied in immunofluorescence, whereas the remaining part of the kidney was fixed in vivo by renal perfusion with a mixture of 0.01 M sodium periodate, 0.075 M lysine HCl, 0.0375 M Na2HPO4, and 2% paraformaldehyde (PLP) and studied in both immunofluorescence and IEM. In the acetone-fixed kidney sections obtained without in vivo fixation we again observed in vivo ANA. However, after in vivo PLP perfusion fixation, no nuclear binding was found. In IEM, localization in cytoplasmic vesicles was seen. In conclusion, antinucleosome antibodies complexed to nucleosomal antigens can bind to the cell surface and are transported into the cytoplasm, but do not bind to the nucleus. The reported nuclear localization of antinuclear antibodies is caused by a fixation artifact.

Heparan sulfate staining of the glomerular basement membrane in relation to circulating anti-DNA and anti-heparan sulfate reactivity: a longitudinal study in NZB/W F1 mice

Reactivity of serum antibodies with heparan sulfate (HS) has been associated with human and murine lupus nephritis, although the aetiological significance of this association is not clear. Recent work from our laboratories showed that binding of these antibodies to HS could be mediated by histone containing immune complexes. In human lupus nephritis we found a strong decrease in HS staining in the glomerular basement membrane (GBM). The aim of this study was to elucidate the correlation in experimental systemic lupus erythematosus (SLE) between albuminuria, staining of HS in the GBM and anti-DNA and anti-HS reactivity in plasma. We therefore studied NZB/W F1 mice during different stages of glomerular disease and compared them with age matched control NZB/W F1 mice without albuminuria. Anti-DNA and anti-HS reactivity were measured in longitudinally collected plasma samples and correlated with the onset of albuminuria, staining of HS in the glomerular basement membrane and deposition of immunoglobulins (Ig). HS staining was significantly decreased in the glomerular capillary loops of mice with prolonged proteinuria in comparison with age matched control mice (P = 0.0013). This decreased HS staining was correlated with increased Ig deposition in the capillary loops (tau = -0.42, P < 0.001), albuminuria (tau = -0.508, P < 0.001) and a decreased in anti-DNA levels measured in plasma (tau = 0.758, P < 0.005). Altered anti-HS reactivity in plasma did correlate with increased Ig deposition in the kidney (tau = 0.33, P < 0.05) but was not correlated with decreased staining of HS in the kidney. In conclusion, our study demonstrates that disappearance of staining of HS in the glomerular capillary loops is associated with albuminuria, increased Ig deposition in the glomerulus and decreased anti-DNA reactivity in plasma. Our findings are compatible with a model in which interaction ('masking') of HS with immune complexes consisting of anti-DNA antibodies and nucleosomes takes place.

Screening psychiatric admissions for anticardiolipin antibody

Anticardiolipin antibody (aCL) may provide an instrument for screening in neuropsychiatric syndromes due to cerebral ischemia. Thirty-five psychiatric patients, aCL-positive on admission, were matched against aCL-negative patients. Their clinical records on admission and after 2-years of follow-up were analyzed without knowledge of aCL results. An inventory was made of cerebrovascular and systemic vascular symptoms. In 13 out of 35 aCL-positive cases, vascular morbidity, suggesting ischemic causes of central nervous system pathology, could be demonstrated during follow-up and none in the comparison group. No correlation was found, however, between Hachinski ischemic scores on admission and aCL-positivity. Yet, if only on the basis of increased incidence of subsequent ischemia, the aCL-IgG/M isotype appears to be a valuable predictor of vascular neuropsychiatric symptoms.

No evidence for an independent role of anti-heparan sulphate reactivity apart from anti-DNA in lupus nephritis

The presence of anti-heparan sulphate (HS) reactivity in serum is closely related to the occurrence of nephritis in patients with systemic lupus erythematosus (SLE). Since patients with lupus nephritis in general also have high titres of anti-DNA antibodies, we wanted to clarify the relationship between anti-HS and anti-DNA reactivity in serum. Therefore, we studied longitudinally six patients with lupus nephritis who experienced 12 exacerbations of their disease, and five SLE patients without nephritis experiencing 10 periods of non-renal disease exacerbations. In addition, we tested single serum samples of another 24 patients obtained during a renal disease exacerbation and 22 sera of patients without nephritis. The sera of all patients were tested for anti-DNA (Farr assay) and anti-HS reactivity (ELISA). We confirmed that SLE patients during renal exacerbations have a significantly higher anti-HS reactivity than patients without nephritis (P < 0.003). In addition, patients with nephritis also had higher titres of anti-DNA antibodies during renal exacerbations than during non-renal exacerbations (P < 0.01). A correlation between anti-DNA and anti-HS reactivity was observed (r = 0.40, P < 0.02), which in itself explains the correlation between nephritis and anti-HS reactivity. Comparing sera from nephritis and non-nephritis patients matched for anti-DNA titre, we found no difference in anti-HS reactivity, and therefore must conclude that the anti-HS reactivity is a direct reflection of anti-DNA reactivity.

Characterization of murine monoclonal antibodies against 60-kD Ro/SS-A and La/SS-B autoantigens

Small cytoplasmic ribonucleoproteins (scRNPs) are important autoantigens in patients with systemic lupus erythematosus and Sjögren's syndrome. MoAbs against these proteins were made by immunization of BALB/c mice with purified human recombinant 60-kD Ro/SS-A or 50-kD La/SS-B proteins. Five stable hybridoma cell lines were obtained, of which four secreted anti-Ro/SS-A antibodies (clones 1D8, 1D11, 2G10 and 6G8) and one produced anti-La/SS-B antibodies (clone 7F6). The MoAbs were further characterized using four different immunoassays: immunofluorescence, immunoblotting, RNA precipitation combined with Northern blotting, and recombinant protein precipitation. All four MoAbs against Ro/SS-A recognized the native protein and one of them (2G10) recognized also intact scRNP particles. Interestingly, hY3-RNA was reproducibly not efficiently precipitated by MoAb 2G10. Epitope mapping using deletion mutants of the 60-kD Ro/SS-A antigen showed that MoAb 1D8 recognized the C-terminal part of this protein, while 1D11 and 2G10 recognized distinct epitopes in the region between the RNP motif and the putative zinc finger domain. The epitopes recognized by these MoAbs are highly conserved among species, and the epitope recognized by MoAb 2G10 may be identical to an autoepitope recognized by sera of patients. This is the first report describing the isolation and characterization of MoAbs of the IgG class against the 60-kD Ro/SS-A and La/SS-B autoantigens obtained by immunization with purified human recombinant proteins. These MoAbs can be of great use in studying the cellular processes in which scRNPs are involved, and may help to determine why these scRNPs become autoantigenic in autoimmune diseases.

Ro/SS-A and La/SS-B: autoantigens in Sjögren's syndrome?

Sjögren's syndrome is characterized serologically by the presence of autoantibodies against Ro/SS-A and La/SS-B. The mechanisms by which these autoantibodies arise is not clear at this moment. B cells capable of producing antibodies to Ro/SS-A and La/SS-B seem to be present in every individual; whether or not an individual indeed makes these antibodies is governed by T cells. Recent experiments from us and from others indicate that T cell tolerance towards Ro/SS-A and La/SS-B can be broken by immunization of normal mice with recombinant human Ro/SS-A or La/SS-B. The specificity of the T cells directing the anti-Ro/SS-A and anti-La/SS-B autoantibody response in these animals has not yet been elucidated. T cells may either be directed against foreign epitopes present on the human immunogen or they may be truly autoreactive. In patients with Sjögren's syndrome, a comparable immunization route might encompass product of viral origin directing the T cell response via RNA/protein complexes. Putative candidates comprise viruses that make use of RNAse polymerase-III, such as Epstein Barr virus, adenovirus, vesicular stomatitis virus en rabies virus.

Decrease of heparan sulfate staining in the glomerular basement membrane in murine lupus nephritis

Recently we found in biopsies of human lupus nephritis a nearly complete loss of heparan sulfate (HS) staining in the glomerular basement membrane (GMB). To clarify the relationship between HS staining and albuminuria in lupus nephritis, we studied MRL/lpr mice with short (< 7 days) or prolonged duration of albuminuria (14-21 days) and compared these with mice of different ages without albuminuria. Kidney sections were stained for mouse immunoglobulin (Ig), HS, heparan sulfate proteoglycan (HSPG)-core protein and laminin in immunofluorescence. In mice with prolonged albuminuria HS staining in the glomerular capillary loops had almost completely disappeared, whereas staining was unaltered in non-albuminuric mice (P = 0.001). In mice with short duration of albuminuria, there was a tendency toward a decrease of HS staining (P = 0.06). The expression of HSPG-core protein and other extra cellular matrix (ECM) components was unaltered in all groups. HS staining correlated inversely with albuminuria (rs = -0.55; P < 0.001) and with staining of Ig deposits in the capillary loops (rs = -0.74; P < 0.001). Despite the nearly complete loss of HS staining in the GBM in mice with prolonged albuminuria, there was no change in glomerular HS content as assessed by agarose electrophoresis and HS inhibition ELISA. We conclude that the development of albuminuria in MRL/lpr mice is accompanied by a loss of HS staining in the GBM, probably due to the masking of HS by deposits of Ig. In vitro studies revealed that autoantibodies complexed to nucleosomal antigens can inhibit the binding of the anti-HS monoclonal antibody to HS. Whether this also occurs in vivo remains to be determined.

Prostaglandin-E2 is a potent inhibitor of human interleukin 12 production

During human immunodeficiency virus infection and allergic diseases, characterized by a dominant T helper (Th) 2 response, overproduction of prostaglandin E2 (PGE2) is observed. In this paper we studied the effect of PGE2 on interleukin (IL)-12 synthesis, because this cytokine has been described to be essential in induction of Th1 responses. IL-12 synthesis was induced in monocytes that were stimulated with Neisseria meningitidis-derived lipopolysaccharide in whole blood cultures. PGE2 almost completely inhibited lipopolysaccharide induced IL-12 production, whereas IL-6 production was only partially inhibited by PGE2. In contrast, the production of IL-10 was approximately twofold enhanced at these conditions. The effects of PGE2 were due to its cAMP-inducing capacity, since they could be mimicked by other cAMP inducers. Recombinant human IL-10 also inhibited IL-12 and IL-6 production. However, the inhibitory effect of PGE2 on IL-12 production was independent of IL-10 since neutralizing anti-IL-10 antibodies were unable to reverse this inhibition. These results suggest that the capacity of an antigen to induce PGE2 synthesis may play a crucial role in the development of either a Th1 or Th2 response.

Pathophysiology of lupus nephritis: the role of nucleosomes

Lupus nephritis is regarded as an immune complex mediated disease. Since anti-DNA antibodies are present in the circulation and in diseased glomeruli of patients with lupus nephritis, these antibodies have been assigned a pivotal role in the initiation of lupus nephritis. It remains however unclear how these antibodies become localized in the glomerulus. Contrary to the classical concept of glomerular deposition of DNA/anti-DNA complexes, it has been suggested that anti-DNA antibodies can interact with intrinsic glomerular antigens. Some anti-DNA antibodies can cross-react with heparan sulphate (HS), which is such an intrinsic constituent of the glomerular basement membrane (GBM). Serum HS reactivity coincides with the occurrence of lupus nephritis. It was found that this HS reactivity was exhibited by anti-DNA antibodies complexed to nucleosomes and not by the antibody itself. Nucleosomes are DNA/histone complexes, present in the nucleus, which are released by dying cells. The histone part of the nucleosome is responsible for the binding to the GBM. Recently, it has become clear that also anti-nucleosome antibodies can bind to HS in the GBM via nucleosomes. These nucleosome-containing immune complexes exhibit anti-DNA reactivity in ELISA and Farr assay. It is now thought that nucleosomes released by dying cells bind to anti-DNA or anti-nucleosome antibodies in the circulation, giving rise to nephritogenic immune complexes. Alternatively, nucleosomes may bind to the GBM and serve then as planted antigen for subsequent binding of antibodies via an in situ mechanism. Binding of antibodies via both mechanisms leads to complement activation and damage of the GBM.(ABSTRACT TRUNCATED AT 250 WORDS)

A new ELISA for the detection of anti-heparan sulfate reactivity, using photobiotinylated antigen

Autoantibodies reacting with a great variety of autoantigens are characteristic for the autoimmune disease systemic lupus erythematosus (SLE). Although reactivity with heparan sulfate (HS) in sera of patients with SLE is found in association with the occurrence of nephritis, the aetiological significance of this association is not clear. The assay which is generally used to measure anti-HS reactivity is subject to false-positive results, as a consequence of the binding of negatively charged moieties within immune complexes to the precoat employed (protamine sulfate). Therefore, we have developed a new ELISA in which photobiotinylated HS is efficiently and reproducibly bound to streptavidin-coated wells. We compared the new ELISA with the classical anti-HS ELISA by testing culture supernatants of 20 murine monoclonal antibodies (mAb) to DNA (containing free anti-DNA and anti-DNA/nucleosome immune complexes) and preparations of these mAb (containing only free anti-DNA), purified under dissociating conditions. In the classical anti-HS ELISA, 14 out of 20 of the culture supernatants reacted positively with HS; after purification no reactivity remained. The discrepancy must be due to anti-DNA/nucleosome immune complexes present in the culture supernatants. In the new ELISA only four out of 20 culture supernatants and one of the purified preparations reacted with HS. This latter reactivity is probably not specific, since this mAb also reacted with streptavidin alone. To find out whether there is a correlation between the occurrence of nephritis and anti-HS reactivity, measured in this new anti-HS ELISA, we tested sera of patients with a renal- or non-renal exacerbation of SLE in the newly developed anti-HS ELISA. We observed a correlation between anti-HS reactivity and nephritis.

Psychiatric symptoms before systemic lupus erythematosus is diagnosed

Psychiatric symptoms are rarely reported as an initial feature of systemic lupus erythematosus (SLE). Nevertheless, many patients have the feeling that psychiatric symptoms occurred before they were diagnosed as having SLE. This feeling was confirmed by an enquiry among members of the Dutch Lupus Patients Society: half of them had experienced psychiatric complaints before SLE was diagnosed. Two-thirds of these patients searched for professional help for these complaints. This motivated us to study whether SLE patients were admitted into psychiatric hospitals without being diagnosed as having SLE. Sera from 2121 patients admitted to a psychiatric hospital and from 500 controls matched for sex and age were tested for the presence of antinuclear antibodies (ANA) and antibodies to DNA. ANA were found in 3% of patients, as well as controls. Anti-DNA antibodies were found in 1% of both patients and controls. Two out of 114 patients psychiatric patients with ANA and/or anti-DNA antibodies had SLE and/or Sjögren's syndrome. We concluded that SLE is not an important cause of admission to psychiatric hospitals. Routine tests for the determination of antinuclear and anti-DNA antibodies on admissions in these hospitals thus would not seem useful. To study whether patients with another chronic disease also had psychiatric complaints before being diagnosed, we performed the same enquiry among members of the Dutch Sarcoidosis Patients Society. The results were almost equal to those of the enquiry of the members of the Dutch Lupus Patients Society. Why members of both societies so often report psychiatric symptoms before their disease is diagnosed should be a subject of further studies.

Anti-nucleosome antibodies complexed to nucleosomal antigens show anti-DNA reactivity and bind to rat glomerular basement membrane in vivo

Histones can mediate the binding of DNA and anti-DNA to the glomerular basement membrane (GBM). In ELISA histone/DNA/anti-DNA complexes are able to bind to heparan sulfate (HS), an intrinsic constituent of the GBM. We questioned whether histone containing immune complexes are able to bind to the GBM, and if so, whether the ligand in the GBM is HS. Monoclonal antibodies (mAbs) complexed to nucleosomal antigens and noncomplexed mAbs were isolated from culture supernatants of four IgG anti-nuclear mAbs. All noncomplexed mAbs showed strong anti-nucleosome reactivity in ELISA. One of them showed in addition anti-DNA reactivity in noncomplexed form. The other three mAbs only showed anti-DNA reactivity when they were complexed to nucleosomal antigens. After renal perfusion a fine granular binding of complexed mAbs to the glomerular capillary wall and activation of complement was observed in immunofluorescence, whereas noncomplexed mAbs did not bind. Immuno-electron microscopy showed binding of complexes to the whole width of the GBM. When HS in the GBM was removed by renal heparinase perfusion the binding of complexed mAb decreased, but did not disappear completely. We conclude that anti-nucleosome mAbs, which do not bind DNA, become DNA reactive once complexed to nucleosomal antigens. These complexed mAbs can bind to the GBM. The binding ligand in the GBM is partly, but not solely, HS. Binding to the GBM of immune complexes containing nucleosomal material might be an important event in the pathogenesis of lupus nephritis.

Clinical evaluation of a modified ELISA, using photobiotinylated DNA, for the detection of anti-DNA antibodies

The measurement of anti-dsDNA antibodies is important for the diagnosis and the follow-up of patients with systemic lupus erythematosus (SLE). For routine detection of anti-dsDNA, the Farr assay and the immunofluorescence technique (IFT) on Crithidia luciliae proved to be very useful. The anti-dsDNA ELISA is not used for routine purposes in our institute since it is flawed by false-positive results due to binding of negatively charged (immune) complexes to the employed precoat (protamine sulphate). Recently, a new anti-dsDNA ELISA has been described in which photobiotinylated dsDNA is coated to streptavidin coated plates. To investigate whether this modified ELISA is more specific than the classical anti-dsDNA ELISA, we tested sera of patients with SLE (n = 51), myasthenia gravis (MG, n = 25), rheumatoid arthritis (RA, n = 25) and Sjögren's syndrome (SS, n = 23) and sera of healthy blood bank donors (BBD, n = 25). In both assays the sera of the SLE patients gave significantly higher values than the sera of healthy blood bank donors. In the classical ELISA, 84% of the sera from patients with RA and 28% of sera of patients with MG were found positive. For the modified assay the figures were 8% and 24%, respectively. This modified ELISA was further studied and clinically evaluated by comparing it with the classical anti-DNA ELISA and two other anti-DNA assays (Farr assay and IFT), using 500 sera sent to our institute for routine anti-DNA determination and sera of an additional 75 healthy blood bank donors. Quantitatively, both ELISAs showed the same high degree of correlation with the IFT. The modified ELISA gave a better correlation with the Farr assay than the classical anti-DNA ELISA. From our data we conclude that the ELISA using photobiotinylated DNA is a more reliable assay than the classical anti-DNA ELISA.

Autoimmunity and filariasis. Autoantibodies against cytoplasmic cellular proteins in sera of patients with onchocerciasis

Onchocerciasis or "river blindness" is a vector-borne tropical disease resulting from infection with the filarial nematode Onchocerca volvulus. Disease manifestations include dermatitis, rheumatic complaints, and blindness. Recent findings have suggested an autoimmune etiology for the occurrence of chorioretinopathy, a disease of the eye which together with sclerosing keratoconjunctivitis is responsible for approximately 400,000 onchocerciasis-related cases of blindness. The identification of onchocerciasis as an important cause of tropical rheumatism prompted us to evaluate serologically the presence of systemic autoimmune disease in onchocerciasis patients and local controls from a hyperendemic area in Sierra Leone. In both groups there was a marked autoimmune response against cytoplasmic non-RNA-associated proteins consisting of autoantibodies against five major Ag with respective m.w. of 35, 51, 64, 83, and 110 kDa. These five proteins are novel autoantigens that could be distinguished from calreticulin, the human homologue of the onchocercal Ag RAL-1, and known autoantigens such as the 50-kDa La/SS-B or 52- and 60-kDa Ro/SS-A proteins by immunoblotting and ELISA assays. Furthermore, autoantibody reactivity against calreticulin was significantly higher in O. volvulus-infected individuals than in endemic controls. Autoantibody reactivity against the five major autoantigens, anti-calreticulin reactivity, and antibody reactivity against the 65-kDa arthritis-associated mycobacterial heat shock protein were intercorrelated as parts of an onchocerciasis-associated autoimmune response. The implication of autoimmunity in the disease pathogenesis of onchocerciasis could have important consequences for future research on therapeutical regimens, pathogenetic mechanisms, and serological diagnosis of onchocerciasis.

Autoimmunity and filariasis. Autoantibodies against cytoplasmic cellular proteins in sera of patients with onchocerciasis

Onchocerciasis or "river blindness" is a vector-borne tropical disease resulting from infection with the filarial nematode Onchocerca volvulus. Disease manifestations include dermatitis, rheumatic complaints, and blindness. Recent findings have suggested an autoimmune etiology for the occurrence of chorioretinopathy, a disease of the eye which together with sclerosing keratoconjunctivitis is responsible for approximately 400,000 onchocerciasis-related cases of blindness. The identification of onchocerciasis as an important cause of tropical rheumatism prompted us to evaluate serologically the presence of systemic autoimmune disease in onchocerciasis patients and local controls from a hyperendemic area in Sierra Leone. In both groups there was a marked autoimmune response against cytoplasmic non-RNA-associated proteins consisting of autoantibodies against five major Ag with respective m.w. of 35, 51, 64, 83, and 110 kDa. These five proteins are novel autoantigens that could be distinguished from calreticulin, the human homologue of the onchocercal Ag RAL-1, and known autoantigens such as the 50-kDa La/SS-B or 52- and 60-kDa Ro/SS-A proteins by immunoblotting and ELISA assays. Furthermore, autoantibody reactivity against calreticulin was significantly higher in O. volvulus-infected individuals than in endemic controls. Autoantibody reactivity against the five major autoantigens, anti-calreticulin reactivity, and antibody reactivity against the 65-kDa arthritis-associated mycobacterial heat shock protein were intercorrelated as parts of an onchocerciasis-associated autoimmune response. The implication of autoimmunity in the disease pathogenesis of onchocerciasis could have important consequences for future research on therapeutical regimens, pathogenetic mechanisms, and serological diagnosis of onchocerciasis.

Maternal autoantibodies and congenital heart block: no evidence for the existence of a unique heart block-associated anti-Ro/SS-A autoantibody profile

One of the rare examples of the transfer of autoimmune disease from mother to (unborn) child is the neonatal lupus syndrome. This syndrome comprises the development of fetal heart disease (congenital heart block) or neonatal skin rash and is specifically associated with maternal anti-Ro/SS-A autoantibodies. Previous studies have suggested that especially maternal autoantibody reactivity against the 52 kDa protein of the Ro/SS-A antigen and/or against the La/SS-B antigen is responsible for the development of congenital heart block (CHB). To determine the CHB-associated antibody response in more detail, we analysed the presence of autoantibodies in sera from mothers of children with isolated heart block. All 14 mothers of children with congenital heart block were positive for anti-Ro/SS-A antibodies. Remarkably, their antibody profile, including recognition of different Ro/SS-A proteins and autoantibody levels against these proteins, did not differ from anti-Ro/SS-A positive mothers of healthy children. In contrast, all 8 anti-Ro/SS-A negative mothers had children with acquired heart block. We conclude from our data that maternal anti-Ro/SS-A antibodies are essential for CHB but that fine analysis of this autoantibody response does not predict the occurrence of CHB.

Antinuclear antibodies in routine analysis: the relevance of putative clinical associations

Defined antinuclear antibodies (ANA), such as antibodies to Ro/SS-A, La/SS-B, Sm, and nRNP, are often present in serum samples from patients with systemic lupus erythematosus (SLE) or other connective tissue diseases (CTD). Most data on associations between the presence of these antibodies and defined disease features have been obtained with the use of predefined groups of patients. In this work the issue of disease associations was approached from a different angle: patients suspected of having CTD were selected on the presence of these ANA in their serum samples and clinical data were subsequently scored according to a defined protocol. It was then tried to relate measured ANA and clinical symptoms. No correlation was observed between the presence of antibodies to Ro/SS-A and specific clinical symptoms. The presence of antibodies to La/SS-B was associated with the diagnosis of Sjögren's syndrome combined with leukocytopenia. In patients positive for antibodies to Sm a significantly increased incidence of skin lesions, such as butterfly rashes and discoid lesions, was seen, together with signs of myocarditis. Myocarditis was also found to be associated with the presence of antibodies to nRNP. The data presented in this study show that previously reported associations of these ANA with clinical symptoms are not confirmed when unselected patients are used.

Anti-DNA antibodies can bind to the glomerulus via two distinct mechanisms

It is generally assumed that antibodies to double stranded DNA (anti-DNA) play a pivotal role in the pathogenesis of SLE nephritis. Recently, we reported that anti-DNA antibodies can bind to heparan sulphate proteoglycan (HSPG), a constituent of the glomerular basement membrane (GBM), via histones and DNA. We postulated that these histone/DNA/anti-DNA complexes can bind via their histone part to the glomerulus in vivo. To test this hypothesis we performed in vitro binding studies with isolated GBM loops and renal perfusion studies in the rat using histones, DNA and an anti-DNA monoclonal antibody (mAb) with high avidity for dsDNA. A strong granular binding of anti-DNA mAb to isolated GBM loops occurred via histones and DNA and a moderate granular binding was found via DNA alone. Anti-DNA mAb alone did not bind to the GBM loops. After perfusion of histones, DNA and immediately thereafter anti-DNA, we found with immunoelectron microscopy (IEM) a strong binding to endothelial cells in the glomerulus and to a lesser extent in the GBM. When the anti-DNA mAb was injected i.v. one hour after perfusion of histones and DNA, we observed a strong fine granular binding to the capillary wall by immunofluorescence (IF) in a membranous pattern along with some minor mesangial deposits. After perfusion of DNA alone followed by anti-DNA mAb, binding in the glomerulus was less than with histones and DNA, and was more restricted to the mesangium. No direct binding to the glomerulus was observed after perfusion with anti-DNA mAb alone, histones and anti-DNA mAb, or histones, DNA and a control mAb.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of heavy and light chain use of lupus-associated anti-La/SS-B and anti-Sm autoantibodies reveals two distinct underlying immunoregulatory mechanisms

The immunoregulatory mechanisms involved in autoimmune diseases are still unclear. One approach to elucidating these mechanisms involves evaluation of the clonality of the lymphocytes involved in autoimmunity. Molecular analysis of the rearrangement patterns of antigen receptor genes in T cells and B cells has produced ambiguous results. The present study focuses on the analysis of the autoantibodies themselves, being the end products of autoimmune reactivity. Heavy and light chain use of autoantibodies and of total IgG was determined in sera containing anti-La/SS-B and/or anti-Sm antibodies, two autoantibody specificities associated with rheumatic diseases such as systemic lupus erythematosus and Sjögren's syndrome. From our experiments, the anti-La/SS-B response emerges as an oligoclonal, IgG1-restricted B-cell response associated with sharply elevated levels of total serum IgG1-kappa. These characteristics are in sharp contrast to the polyclonal, IgG-subclass-unrestricted anti-Sm response which is accompanied by normal or slightly elevated total serum IgG levels. These findings suggest that anti-La/SS-B autoantibodies, in contrast to anti-Sm autoantibodies, are the product of a restricted oligoclonal B-cell response and thus may be the consequence of a (virally triggered) benign B-cell lymphoma.

Quantification of glomerular epithelial cell adhesion by using anti-DNA antibodies in ELISA

A sensitive and reproducible microassay is described for quantification of adhesion of cells to matrix-coated 96-wells plates under different experimental conditions. For this purpose glomerular visceral epithelial cells (GVEC) were used. Attached GVEC were fixed with methanol and incubated with a monoclonal anti-DNA antibody. Following standard procedures, the amount of bound antibody was quantified by ELISA. A positive linear relationship in the range of 800-5000 cells per well was found between OD values and cell numbers obtained by hand-counting (r = 0.94, p less than 0.001). The assay is 10 to 100 times more sensitive than most other adhesion assays. The applicability of the ELISA assay was demonstrated by manipulation of the temperature during adhesion and by using different concentrations of the matrix-molecules fibronectin, EHS-laminin and collagen type I. The ELISA assay was found to be unaffected by non-specific interaction of anti-DNA antibodies with the matrix molecules used for coating. The assay was neither affected by potential release of DNA from the GVEC under these different experimental conditions. In conclusion, this cell adhesion microassay is simple, reliable, sensitive, and cost-effective, since it requires small amounts of GVEC and reagents.

The development of a quantitative assay for the detection of anti-Ro/SS-A and anti-LA/SS-B autoantibodies using purified recombinant proteins

A characteristic of patients with autoimmune diseases such as Sjögren's syndrome and systemic lupus erythematosus is the presence of anti-Ro/SS-A and anti-La/SS-B autoantibodies in their circulation. In order to investigate specific autoantibody levels in the sera of these patients quantitative assays for the detection of both anti-Ro/SS-A and anti-La/SS-B reactivity were developed. Ro/SS-A (60 kDa) and La-SS-B (50 kDa) cDNAs were cloned and expressed in E. coli as non-fusion proteins. These were purified to homogeneity using two different purification protocols. With these recombinant antigens, specific enzyme-linked immunosorbent assays (ELISAs) were developed. 40 sera positive for anti-Ro/SS-A autoantibodies in counterimmunoelectrophoresis (CIE) were tested in both the Ro/SS-A and La/SS-B ELISA. Activity values reproducibly ranged from 1536 to 120,000 U in the Ro/SS-A ELISA and from 763 to 2,500,000 U in the La/SS-B ELISA. The suitability of these ELISAs as screening assays was further investigated by testing 200 sera sent to our laboratory for routine detection of autoantibodies to extractable nuclear antigen (ENA: anti-Sm, anti-RNP, anti-Ro/SS-A and anti-La/SS-B). Both ELISAs showed a high sensitivity and specificity (Ro/SS-A ELISA 85% and 94%, La/SS-B ELISA 100% and 98% respectively), when compared to the standard assays, the RNA-precipitation assay and the HeLa immunoblotting test. From these data we conclude that a quantitative analysis of both anti-Ro/SS-A and anti-La/SS-B autoantibodies is now possible using purified recombinant non-fusion proteins. For screening purposes the La/SS-B ELISA showed a great improvement in sensitivity for the detection of anti-La/SS-B activity in comparison to the La/SS-B CIE, while the Ro/SS-A ELISA almost equalled the performance of the Ro/SS-A CIE.

Changes in clinical features of patients with systemic lupus erythematosus followed prospectively over 2 decades

In the past decades the general concept of the disease course and the prognosis of systemic lupus erythematosus (SLE) has changed dramatically. The improvement in prognosis of our SLE patients is often said to be related to the growing awareness of the disease. This study focussed on whether or not the clinical features at the onset of the disease, and at diagnosis, and the clinical course as well as the age at the onset of the disease had changed during the past decades. No obvious differences were observed in the age at the onset of the disease or in the age at diagnosis. Of the 22 clinical signs studied, only the prevalence of Raynaud's phenomenon at the onset of the disease had increased during the past 20 years. At diagnosis, the prevalence of oral ulcers and false positive syphilis test had decreased. Only small differences in the type but not in the number of exacerbations were observed; in the past 20 years, the prevalence of renal involvement increased from 20% to 43%. However, this was not significant. Our results did not support the theory that during the past 2 decades the disease had changed in its expression, neither did we find that the disease is presently diagnosed at an earlier age, as would be expected from the increased awareness of the disease.

Autoantibodies and their target antigens in Sjögren's syndrome

The subject of this review is the humoral autoimmune response in Sjögren's syndrome. Autoantibodies in this disease are primarily directed against the Ro/SS-A and La/SS-B autoantigens and against IgG (rheumatoid factor). The Ro/SS-A and La/SS-B autoantigens consist of a number of antigenic proteins coupled to small RNA molecules. These RNA-protein particles are present in all human cells and are strongly conserved throughout various species. Anti-Ro/SS-A and anti-La/SS-B autoantibodies can be detected using counter-immunoelectrophoresis, immunoblotting technique, ELISA or RNA precipitation assays. The preferred method of screening for anti-Ro/SS-A antibodies in human sera is counter-immunoelectrophoresis; anti-La/SS-B antibodies are best detected with the immunoblotting technique. Anti-Ro/SS-A antibodies are found in 60% of patients with Sjögren's syndrome, but are not specific markers for this disease. Anti-La/SS-B antibodies are present in approximately 40% of patients with Sjögren's syndrome; the only other disease where the antibody has been detected is systemic lupus erythematosus (15% positive). The origin and possible pathogenetic role of autoantibodies in Sjögren's syndrome is still unclear. Our view is that the current evidence supports a mechanism whereby autoantibodies are the product of an oligoclonal B-cell proliferation. The only instance where autoantibodies probably play a direct pathogenetic role is the occurrence of congenital heart block in the offspring of anti-Ro/SS-A and anti-La/SS-B positive mothers.