Article Text

PDF

OP0071 A pathogenic anti-dna antibody binds to alpha-actinin in renal mesangial cells
  1. C Putterman,
  2. B Deocharan
  1. Division of Rheumatology, Albert Einstein College of Medicine, Bronx, NY, USA

Abstract

Background Anti-DNA antibodies have been demonstrated to play an important role in the pathogenesis of nephritis in systemic lupus erythematosus. One mechanism by which anti-DNA antibodies may contribute to nephritis is by cross-reactivity with renal antigens. However, the identity of this renal antigen remains elusive.

Objectives To identify the target antigen bound by a pathogenic anti-DNA antibody in renal tissue.

Methods Western blotting and immunoprecipitations of total cell lysate from mesangial cell lines derived from the autoimmune MRL-lpr/lpr mouse (lpr-mc) and a non-autoimmune BALB/c mouse (mc), with R4A, a pathogenic murine IgG2b anti-DNA antibody, and with 95, a non-pathogenic antibody derived from R4A by site-directed mutagenesis. The immunoprecipitated protein was identified by matrix assisted laser desorption ionisation mass spectrometry (MALDI-MS) of tryptic digests.

Results The pathogenic anti-DNA antibody R4A, but not control isotype-matched antibodies, bound to and immunoprecipitated a 100 kD protein from mesangial cell lysates. Binding was more pronounced using lpr-mc rather than non-autoimmune mc lysate. Little effect on binding was seen after treatment of the cell lysate or R4A with DNAse, while proteinase K treatment abolished binding. Preliminary MALDI-MS analysis revealed that alpha-actinin, an actin bundling protein that plays a role in experimental nephritis models, is present in the protein band immunoprecipitated by R4A. R4A, but not 95, binds to immobilised alpha-actinin by ELISA; Furthermore, double stranded DNA significantly inhibited the binding of R4A to the 100 kD mesangial cell protein, as well as to purified alpha-actinin. Serum of MRL-lpr/lpr lupus mice with active disease contain high-titer antibodies to alpha-actinin.

Conclusion The nephritogenicity of some anti-DNA antibodies may be mediated via cross-reactivity with a glomerular antigen. Variations in the display of the cross-reactive antigen in the target organ between individuals may underlie differential susceptibility to anti-DNA antibody induced renal disease.

Statistics from Altmetric.com

Request permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.