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

Abstract

IntroductionHistones 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. (J. Clin. Invest. 1994. 94:568-577.)

Critical comparative analyses of anti–α‐actinin and glomerulus‐bound antibodies in human and murine lupus nephritis

“…On the basis of the results presented above, serum antibodies and antibodies eluted from kidneys of individual B/W or BALB/c mice were further analyzed for binding to ␣-actinin, dsDNA, and H1. DNase I and heparan sulfate were included as control antigens in all ELISAs, because these ligands bind dsDNA (35) and nucleosomes (16,25).…”

“…It is unlikely that nucleosomes, if bound to these antibodies, could mediate binding to both anionic (DNA) and cationic (H1) structures. Nucleosomes are reported to bind anionic heparan sulfate or type IV collagen through protruding tails of cationic histones (16,25,38). In this respect, anti-dsDNA antibody-bound nucleosomes should be repelled by H1 rather than bound to it.…”

“…Their variable region structures and dsDNA specificity have been characterized previously (24). In selected experiments, mAb 163p64.1 and 163p77 were made nucleosome-free, according to the protocol described by Kramers et al (25). Monoclonal anti-H1 antibody was provided by BioSite (Täby, Sweden), and goat anti-␣-actinin and rabbit anti-type IV collagen antibodies were from Santa Cruz Biotechnology (Santa Cruz, CA).…”

CD4+ T Cells from (New Zealand Black × New Zealand White)F1 Lupus Mice and Normal Mice Immunized Against Apoptotic Nucleosomes Recognize Similar Th Cell Epitopes in the C Terminus of Histone H3

“…3 High levels of nucleosomespecific Abs are often detectable in the serum of patients and young mice with lupus before the appearance of Abs to its individual components, dsDNA and histones (1,2). Nucleosomes are also important for mediating tissue lesions, especially glomerulonephritis (3)(4)(5)(6).…”

“…Moreover, elevated plasma levels of nucleosomes have been observed in lupus patients (7,8), and a positive correlation (9,10) or absence of correlation (11) has been found between the level of these circulating nucleosomes and active disease. Compelling evidence is also accumulating to suggest that some (but not all) anti-nucleosome Abs are nephritogenic and that their level can be increased in active lupus (3,4,11,12). Amoura et al (11) further demonstrated an inverse correlation between nucleosome plasma levels and serum anti-nucleosome Ab activity.…”