title: Production of a novel class of polyreactive pathogenic autoantibodies in BXD2 mice causes glomerulonephritis and arthritis.
abstract: OBJECTIVE
  The BXD2 mouse strain spontaneously develops glomerulonephritis and erosive arthritis. The goal of this study was to identify the antigenic target proteins and epitopes and to unravel the mechanisms by which the related conditions arise in BXD2 mice.
  
  
  METHODS
  Individual hybridomas isolated from the spleen of a 10-month-old BXD2 mouse were injected intraperitoneally into nonautoimmune mice for evaluation of pathogenicity of each autoantibody. Autoantigens were immunoprecipitated with the pathogenic autoantibody L3A4. Autoantigens were identified using enzyme-linked immunosorbent assay, Western blotting, 2-dimensional gel electrophoresis, and matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MS) and tandem MS. Antigenic epitopes were determined using a high-throughput epitope mapping method.
  
  
  RESULTS
  The production of autoantibodies in BXD2 mice occurred in an orderly progression, with peak levels of autoantibodies to nitrotyrosine (NT)-modified enolase, Ro, alpha-actin, and heat-shock proteins (HSPs) preceding peak levels of antihistone, anti-DNA, and rheumatoid factor. Two monoclonal autoantibodies, L3A4 and T56G10, were identified that could induce immune complexes, renal disease, and/or arthritis. Both L3A4 and T56G10 were polyreactive, and each reacted with separate sets of autoantigens. The antigenic targets of L3A4 consisted of NT-modified enolase, ATP5b, alpha-actin, and Hsp70 family proteins including Hspa5 and Hsp74. The antigenic epitopes of NT-modified enolase and Hspa5 exhibited sequence homology and cross-reactivity, suggesting that epitope spreading may occur through a molecular mimicry mechanism.
  
  
  CONCLUSIONS
  The polyreactivity of autoantibodies that target a novel class of autoantigens may enable these autoantibodies to induce erosive arthritis or glomerulonephritis either by direct pathogenic mechanisms or indirectly via Fc or immune complex deposition.
authors.affiliation: University of Alabama at Birmingham, 701 South 19th Street, Birmingham, AL 35294, USA.
authors.forename: Hui-Chen
authors.initials: HC
authors.lastname: Hsu
authors.forename: Tong
authors.initials: T
authors.lastname: Zhou
authors.forename: Helen
authors.initials: H
authors.lastname: Kim
authors.forename: Stephen
authors.initials: S
authors.lastname: Barnes
authors.forename: PingAr
authors.initials: P
authors.lastname: Yang
authors.forename: Qi
authors.initials: Q
authors.lastname: Wu
authors.forename: Juling
authors.initials: J
authors.lastname: Zhou
authors.forename: Bruce A
authors.initials: BA
authors.lastname: Freeman
authors.forename: Ming
authors.initials: M
authors.lastname: Luo
authors.forename: John D
authors.initials: JD
authors.lastname: Mountz
mesh_terms: D000818:Animals; D001168:Arthritis / Q000276:immunology*; D001323:Autoantibodies / Q000096:biosynthesis* / Q000276:immunology; D000091342:Endoplasmic Reticulum Chaperone BiP; D005921:Glomerulonephritis / Q000276:immunology*; D051379:Mice
chemical_list: D001323:Autoantibodies; D000091342:Endoplasmic Reticulum Chaperone BiP; C000717248:Hspa5 protein, mouse