title: Nucleosomes and C1q bound to glomerular endothelial cells serve as targets for autoantibodies and determine complement activation.
abstract: Various studies indicate a role for both anti-nucleosome and anti-C1q autoantibodies in glomerulonephritis in patients with systemic lupus erythematosus. However, a causal relationship between these autoantibodies and the development of lupus nephritis has not been fully established. Since injury of the endothelium is a major target in lupus nephritis we assessed the interaction of C1q and nucleosomes with glomerular endothelial cells in vitro in the presence or absence of autoantibodies against these antigens. We demonstrate a direct and dose-dependent binding of both nucleosomes and C1q to immortalized human glomerular endothelial cells (GEnC) in vitro, which in part is mediated by cell surface heparan sulfate. We demonstrate that nucleosomes and C1q serve as targets for monoclonal and polyclonal antibodies as well as for anti-nuclear autoantibodies from patients with systemic lupus erythematosus. An additive effect of anti-C1q autoantibodies on anti-nucleosome mediated complement activation was observed. Furthermore, we showed that the activation of complement on glomerular endothelial cells is mediated by the classical pathway since the deposition of C3 on GEnC is abrogated by MgEGTA and does not occur in C1q-depleted serum. Taken together, our studies demonstrate a direct binding of both nucleosomes and C1q to glomerular endothelial cells in vitro. The subsequent binding of autoantibodies against nucleosomes in patients with systemic lupus erythematosus is potentially pathogenic and autoantibodies against C1q seem to have an additional effect.
authors.affiliation: Department of Nephrology, Leiden University Medical Centre, Albinusdreef 2, 2300 ZA, Leiden, the Netherlands. J.O_flynn@lumc.nl
authors.forename: Joseph
authors.initials: J
authors.lastname: O'Flynn
authors.forename: Roelof
authors.initials: R
authors.lastname: Flierman
authors.forename: Pieter
authors.initials: P
authors.lastname: van der Pol
authors.forename: Angelique
authors.initials: A
authors.lastname: Rops
authors.forename: Simon C
authors.initials: SC
authors.lastname: Satchell
authors.forename: Peter W
authors.initials: PW
authors.lastname: Mathieson
authors.forename: Cees
authors.initials: C
authors.lastname: van Kooten
authors.forename: Johan
authors.initials: J
authors.lastname: van der Vlag
authors.forename: Jo H
authors.initials: JH
authors.lastname: Berden
authors.forename: Mohamed R
authors.initials: MR
authors.lastname: Daha
mesh_terms: D001323:Autoantibodies / Q000276:immunology*; D001324:Autoantigens / Q000276:immunology*; D002469:Cell Separation; D003167:Complement Activation / Q000276:immunology; D015922:Complement C1q / Q000276:immunology*; D042783:Endothelial Cells / Q000276:immunology; D005434:Flow Cytometry; D006801:Humans; D007678:Kidney Glomerulus / Q000276:immunology*; D008181:Lupus Nephritis / Q000276:immunology*; D009707:Nucleosomes / Q000276:immunology*
chemical_list: D001323:Autoantibodies; D001324:Autoantigens; D009707:Nucleosomes; D015922:Complement C1q