title: IgG subclass distribution of autoantibodies differs between renal and extra-renal relapses in patients with systemic lupus erythematosus.
abstract: BACKGROUND
  IgG subclasses of autoantibodies differ in their potential to induce an inflammatory response as they interact differentially with complement and Fcgamma receptors.
  
  
  METHODS
  The IgG subclass distribution of anti-nucleohistone and anti-dsDNA antibodies was analysed longitudinally in patients with systemic lupus erythematosus before and at the moment of an extra-renal (n=23) or a renal relapse (n=l7). Kidney biopsy specimens of patients with a renal relapse were analysed for IgG subclass deposition.
  
  
  RESULTS
  IgG1 anti-nucleohistone and IgG1 anti-dsDNA antibodies were present in plasma of 39 out of 40 patients. At the moment of a relapse, IgG2 and IgG3 anti-nucleohistone and IgG2 anti-dsDNA antibodies were more frequently present in patients with renal disease compared with those with extra-renal disease. Increases in levels of IgG1 anti-dsDNA were observed in 10 out of 11 patients prior to a renal relapse but only 10 out of 22 patients with an extra-renal relapse (91 vs 45%, P=0.02). Rises in IgG2 anti-dsDNA occurred at an equally low rate prior to both renal and extra-renal relapses. A rise in IgG2 anti-nucleohistone antibodies preceded a renal relapse in eight of 11 patients and an extra-renal relapse in only four out of 22 patients (73 vs 18%, P=0.006). In kidney biopsies all IgG subclasses could be detected. IgG1 and IgG2 subclass antibodies to nucleohistone and to dsDNA are the predominant subclasses found in plasma of lupus patients with renal disease.
  
  
  CONCLUSIONS
  The frequent occurrence of a rise in IgG2 anti-nucleohistone and IgG1 anti-dsDNA in patients prior to a renal relapse suggests that, besides IgG1 subclass autoantibodies, IgG2 subclass antibodies to nucleohistone have a particular pathophysiological role in lupus nephritis.
authors.affiliation: Department of Clinical Immunology, University Hospital, 9700 RB Groningen, The Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: Bijl
authors.forename: H M
authors.initials: HM
authors.lastname: Dijstelbloem
authors.forename: W W
authors.initials: WW
authors.lastname: Oost
authors.forename: H
authors.initials: H
authors.lastname: Bootsma
authors.forename: R H W M
authors.initials: RH
authors.lastname: Derksen
authors.forename: J
authors.initials: J
authors.lastname: Aten
authors.forename: P C
authors.initials: PC
authors.lastname: Limburg
authors.forename: C G M
authors.initials: CG
authors.lastname: Kallenberg
mesh_terms: D000328:Adult; D000974:Antibodies, Antinuclear / Q000032:analysis; D001323:Autoantibodies / Q000032:analysis*; D001707:Biopsy, Needle; D003430:Cross-Sectional Studies; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000032:analysis*; D008137:Longitudinal Studies; D008180:Lupus Erythematosus, Systemic / Q000276:immunology* / Q000473:pathology; D008181:Lupus Nephritis / Q000276:immunology* / Q000473:pathology; D008297:Male; D011336:Probability; D011379:Prognosis; D012680:Sensitivity and Specificity; D018709:Statistics, Nonparametric
chemical_list: D000974:Antibodies, Antinuclear; D001323:Autoantibodies; D007074:Immunoglobulin G