title: Glomerular IgG subclasses in idiopathic and malignancy-associated membranous nephropathy.
abstract: BACKGROUND
  In idiopathic membranous nephropathy (MN), antibodies directed towards the glomerular phospholipase A2 receptor (PLA2R) have mainly been reported to be of IgG4 subclass. However, the role of the different IgG subclasses in the pathogenesis of MN, both in idiopathic MN and in secondary cases, is still unclear. In this retrospective study, we test the hypothesis that the absence of glomerular IgG4 and PLA2R in patients with MN indicates malignant disease.
  
  
  METHODS
  The distribution pattern of glomerular IgG subclasses and PLA2R was studied in 69 patients with idiopathic MN and 16 patients with malignancy-associated MN who were followed up for a mean of 83 months.
  
  
  RESULTS
  A significant correlation between the absence of IgG4 and PLA2R and malignancy-associated MN was found. Thus, IgG4 was positive in 45 of 69 patients (65%) with idiopathic MN but only in 5 of 16 patients (31%) with malignancy-associated MN. The other IgG subclasses did not differ statistically between the groups, IgG2-positivity being present in more than 94% of patients in both groups. Thirty-five of 63 patients (56%) with idiopathic MN and 3 of 16 (19%) patients with malignancy-associated MN had glomerular deposits of PLA2R.
  
  
  CONCLUSIONS
  We have found that the absence of glomerular IgG4 and PLA2R is common in patients with malignancy-associated MN. In our material, IgG2 could not be used as a marker of underlying malignant disease. Finally, neither IgG1 nor IgG3 seems to be involved in the pathogenesis of MN.
authors.affiliation: Institute of Medicine, Sahlgrenska Academy , University of Gothenburg , Gothenburg , Sweden.
authors.forename: Jennie
authors.initials: J
authors.lastname: Lönnbro-Widgren
authors.affiliation: Institute of Neuroscience and Physiology, Sahlgrenska Academy , University of Gothenburg , Gothenburg , Sweden.
authors.forename: Kerstin
authors.initials: K
authors.lastname: Ebefors
authors.affiliation: Institute of Biomedicine, Sahlgrenska Academy , University of Gothenburg , Gothenburg , Sweden.
authors.forename: Johan
authors.initials: J
authors.lastname: Mölne
authors.affiliation: Institute of Neuroscience and Physiology, Sahlgrenska Academy , University of Gothenburg , Gothenburg , Sweden.
authors.forename: Jenny
authors.initials: J
authors.lastname: Nyström
authors.affiliation: Institute of Medicine, Sahlgrenska Academy , University of Gothenburg , Gothenburg , Sweden.
authors.forename: Börje
authors.initials: B
authors.lastname: Haraldsson
keywords: cancer; glomerulonephritis; kidney; membranous nephropathy; proteinuria