Effect of variable doses of antilymphocyte serum on T cell depletion and cardiac allograft survival.
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M N Hylkema
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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.
Animals↗
Specificity of monoclonal anti-nucleosome auto-antibodies derived from lupus mice.
Recently, anti-nucleosome antibodies, which do not bind to DNA or to individual histones, have been identified in longitudinal studies in lupus mice. These anti-nucleosome antibodies occur early in spontaneous SLE and are formed prior to other anti-nuclear specificities. However, nucleosomal epitopes are yet to be fully characterized. We selected a panel of six monoclonal anti-nucleosome antibodies (mAbs) (#2, #32, #34, PL2-6, LG8-1 and LG10-1) derived from lupus mice. These mAbs were tested in ELISA on subnucleosome structures and on a panel of 53 histone peptides, covering the entire sequence of the five histones. Two mAbs reacted with one of these peptides, but the reactivity hardly exceeded the background reactivity. Based on the nucleosome and subnucleosome ELISA we identified different recognition patterns. Three mAbs showed the highest reactivity towards the intact nucleosome. For two of them (#32 and LG8-1) the nucleosomal epitope was primarily located on H2A-H2B/DNA, whereas for mAb #34 this primary epitope was located on H3/H4/DNA. Two mAbs (#2 and PL2-6) showed the highest reactivity with H2A-H2B/DNA and one mAb (LG10-1) recognized H3-H4/DNA. In the subnucleosome ELISA all but one (mAb #32) recognized more than one epitope, including DNA complexed to a variety of cationic molecules. Comparing these reactivities we identified for all mAbs one specific nucleosomal epitope, whereas reactivity with other subnucleosomes was comparable to the reactivity towards DNA complexed with cationic molecules. In inhibition experiments both in ELISA and in immunofluorescence it was found that only one of the mAbs (i.e. PL2-6), recognizing an epitope on H2A-H2B/DNA as primary epitope, could be inhibited by H2A-H2B/DNA in fluid phase. The two mAbs recognizing an epitope on H3-H4/DNA as primary epitope could be inhibited by H3-H4/DNA in fluid phase. From these analyses, we conclude first that for these nucleosome specific mAbs linear histone peptides are not very important. Second, that these mAbs all recognize different epitopes on both H2A/H2B-DNA and H3/H4-DNA and third that some solid phase H2A/H2B-DNA epitopes are not expressed on fluid phase H2A/H2B-DNA. Our findings suggest that in SLE the nucleosome can act as auto-antigen and that there is no immunodominant beta cell epitope within the nucleosome.
Animals↗
Significance of anti-nuclear and anti-extracellular matrix autoantibodies for albuminuria in murine lupus nephritis; a longitudinal study on plasma and glomerular eluates in MRL/l mice.
The relationship between autoantibody reactivities and nephritis in systemic lupus erythematosus (SLE) is unclear. We studied MRL/l mice which developed a considerable albuminuria (either mice with short ( < 1 week) or heavy and prolonged (3 weeks) albuminuria) and compared them with non-albuminuric age-matched controls, with young (12 weeks old) non-albuminuric mice and with mice which were followed for 36 weeks and did not develop albuminuria. In a longitudinal prospective study on plasma samples we correlated a variety of anti-nuclear reactivities and reactivities against extracellular matrix (ECM) components, with the onset of albuminuria. We found that at the onset of albuminuria, anti-DNA was higher while anti-nucleosome and anti-H2A/H2B-DNA subnucleosome reactivities were lower compared with age-matched non-albuminuric mice. We also studied glomerular eluates of these mice in ELISA and in indirect immunofluorescence (IF). In the eluates we found with IF that anti-glomerular basement membrane (GBM)-tubular basement membrane (TBM) antibodies were already present in 12-week-old non-albuminuric mice. These eluates showed no anti-nuclear antibodies. In eluates of albuminuric mice more immunoglobulin was deposited, and anti-ECM, anti-DNA and anti-nucleosome reactivities were higher than in eluates of age-matched non-albuminuric mice. The deposition of anti-nucleosome antibodies preceded the deposition of anti-DNA antibodies since they were deposited to a greater extent in mice with a short albuminuria. We conclude that anti-GBM-TBM antibodies are the first autoantibodies that deposit in glomeruli of MRL/l mice at an early age. The onset of albuminuria is associated with additional deposition of both anti-ECM and anti-nuclear (anti-nucleosome and anti-DNA) antibodies, but the difference with non-albuminuric mice seems to be more quantitative than qualitative.
Albuminuria↗
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.
Animals↗
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.
Antibodies, Antinuclear↗
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.
Albuminuria↗
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.
Animals↗
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.
Antibodies, Antinuclear↗
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.
Animals↗
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)
Antibodies, Antinuclear↗