Autoantibodies to hLAMP-2 in ANCA-negative pauci-immune focal necrotizing GN

J Am Soc Nephrol. 2014 Mar;25(3):455-63. doi: 10.1681/ASN.2013030320. Epub 2013 Nov 7.

Abstract

Pauci-immune focal necrotizing GN (piFNGN) is usually associated with ANCAs that are thought to be pathogenic. However, 10%-15% of patients are ANCA negative and the cause of their injury is unknown. We previously reported a high frequency of autoantibodies to human lysosome-associated membrane protein-2 (hLAMP-2) in ANCA-associated piFNGN, and have now investigated whether the same is true in ANCA-negative patients. Of 11 patients, 8 (73%) had anti-hLAMP-2 antibodies detected by ELISA and confirmed by immunoblotting and indirect immunofluorescence. The autoantibodies from all 8 patients bound to native LAMP-2 purified from human glomeruli and recombinant hLAMP-2 expressed in ldlD cells, both with molecular masses of 110 kD. However, in contrast to anti-LAMP-2 antibodies from ANCA-positive patients, these antibodies from ANCA-negative patients failed to bind the more complexly glycosylated native neutrophil hLAMP-2 (190 kD). Treatment with the deglycosylating enzyme, endo-β-galactosidase, reduced the mass of neutrophil hLAMP-2 to 110 kD and enabled autoantibody binding. Similarly, pretreating neutrophils with endo-β-galactosidase or neuraminidase converted ANCA assay results from negative to positive. Finally, IgG from LAMP-2-positive ANCA-negative patients bound specifically to normal human kidney sections and to human glomerular endothelial cells in culture. In conclusion, in patients with ANCA-negative piFNGN, we have identified autoantibodies to hLAMP-2 that bind native glomerular but not neutrophil hLAMP-2, suggesting a role in pathogenesis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Antibodies, Antineutrophil Cytoplasmic / immunology
  • Autoantibodies / blood
  • Cohort Studies
  • Female
  • Glomerulonephritis / immunology*
  • Humans
  • Lysosomal-Associated Membrane Protein 2 / immunology*
  • Male
  • Middle Aged
  • Young Adult

Substances

  • Antibodies, Antineutrophil Cytoplasmic
  • Autoantibodies
  • LAMP2 protein, human
  • Lysosomal-Associated Membrane Protein 2