title: Autoantibodies to hLAMP-2 in ANCA-negative pauci-immune focal necrotizing GN.
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.
authors.affiliation: Clinical Institute of Pathology, Medical University of Vienna, Austria; and.
authors.forename: Andrea
authors.initials: A
authors.lastname: Peschel
authors.forename: Neil
authors.initials: N
authors.lastname: Basu
authors.forename: Alexandra
authors.initials: A
authors.lastname: Benharkou
authors.forename: Ricarda
authors.initials: R
authors.lastname: Brandes
authors.forename: Markus
authors.initials: M
authors.lastname: Brown
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Rees
authors.forename: Renate
authors.initials: R
authors.lastname: Kain
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D019268:Antibodies, Antineutrophil Cytoplasmic / Q000276:immunology; D001323:Autoantibodies / Q000097:blood; D015331:Cohort Studies; D005260:Female; D005921:Glomerulonephritis / Q000276:immunology*; D006801:Humans; D052119:Lysosomal-Associated Membrane Protein 2 / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D055815:Young Adult
chemical_list: D019268:Antibodies, Antineutrophil Cytoplasmic; D001323:Autoantibodies; C497811:LAMP2 protein, human; D052119:Lysosomal-Associated Membrane Protein 2