title: IgA1-containing immune complexes in IgA nephropathy differentially affect proliferation of mesangial cells.
abstract: BACKGROUND
  Sera of patients with IgA nephropathy (IgAN) contain circulating immune complexes (CIC) composed of galactose-deficient IgA1 complexed with antiglycan antibodies. The role of these CIC in the pathogenesis of IgAN is not known.
  
  
  METHODS
  We studied how proliferation of cultured mesangial cells (MC) is affected by CIC prepared from sera of IgAN patients and healthy control subjects using size-exclusion chromatography. CIC-containing fractions were added to serum-starved MC in culture, and cell proliferation was measured using (3)H-thymidine incorporation. The results were confirmed by staining MC using an antibody against proliferating cell nuclear antigen.
  
  
  RESULTS
  The incubation of starved MC with serum fractions with M(r) 800 to 900 kD, rich with galactose-deficient IgA1, stimulated proliferation, while fractions with smaller complexes were inhibitory. Furthermore, CIC-containing larger molecular mass fractions isolated from serum of an IgAN patient collected during an episode of macroscopic hematuria stimulated MC proliferation more than CIC obtained during a subsequent quiescent phase. To examine the role of IgA, we removed IgA1 from serum before fractionation. The resultant IgA1-depleted fractions were devoid of stimulatory IgA-CIC. Sera of IgAN patients were also fractionated after addition of desialylated galactose-deficient polymeric IgA1 to form additional immune complexes. Supplementation with a small quantity of this IgA1 increased cellular proliferation in assays using serum fractions of M(r)>/=800 to 900 kD; uncomplexed IgA1 did not affect MC proliferation significantly. In contrast, supplementation with a larger quantity of this IgA1 inhibited cellular proliferation in assays using serum fractions of M(r) 700 to 800 kD.
  
  
  CONCLUSIONS
  Overall, these findings suggest that CIC containing aberrantly glycosylated IgA1 affect proliferation of MC in vitro and, thus, likely play a role in the pathogenesis of IgAN.
authors.affiliation: Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA. jannovak@uab.edu
authors.forename: Jan
authors.initials: J
authors.lastname: Novak
authors.forename: Milan
authors.initials: M
authors.lastname: Tomana
authors.forename: Karel
authors.initials: K
authors.lastname: Matousovic
authors.forename: Rhubell
authors.initials: R
authors.lastname: Brown
authors.forename: Stacy
authors.initials: S
authors.lastname: Hall
authors.forename: Lea
authors.initials: L
authors.lastname: Novak
authors.forename: Bruce A
authors.initials: BA
authors.lastname: Julian
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Wyatt
authors.forename: Jiri
authors.initials: J
authors.lastname: Mestecky
mesh_terms: D000328:Adult; D000936:Antigen-Antibody Complex / Q000502:physiology*; D049109:Cell Proliferation; D005260:Female; D005920:Glomerular Mesangium / Q000166:cytology*; D005922:Glomerulonephritis, IGA / Q000209:etiology / Q000276:immunology*; D006801:Humans; D007070:Immunoglobulin A / Q000502:physiology*; D007074:Immunoglobulin G / Q000502:physiology; D008297:Male
chemical_list: D000936:Antigen-Antibody Complex; D007070:Immunoglobulin A; D007074:Immunoglobulin G