title: Identification of GP2, the major zymogen granule membrane glycoprotein, as the autoantigen of pancreatic antibodies in Crohn's disease.
abstract: OBJECTIVE
  The aetiopathogenesis of Crohn's disease, an inflammatory bowel disease (IBD), is not yet fully understood. Autoimmune mechanisms are thought to play a role in the development of Crohn's disease, but the target antigens and the underlying pathways have not been sufficiently identified.
  
  
  METHODS
  Based on data from immunoblotting and matrix-assisted laser desorption ionisation time-of-flight (MALDI-TOF) mass spectrometry, the major antigenic target of pancreatic autoantibodies (PABs), which are specific for Crohn's disease, was identified. Specificity of autoantibody reactivity was confirmed by enzyme-linked immunosorbent assay (ELISA) and indirect immunofluorescence (IIF) using purified rat and human recombinant GP2 synthesised in transiently transfected mammalian HEK 293 cells. Real-time polymerase chain reaction (rt-PCR) and IIF were used to detect mRNA and antigen localisation in human colon biopsies.
  
  
  RESULTS
  The major zymogen granule membrane glycoprotein 2 (GP2) was identified as the autoantigen of PABs in Crohn's disease. PAB-positive sera from patients with Crohn's disease (n = 42) displayed significantly higher IgG reactivity to rat GP2 in ELISA than either PAB-negative sera (n = 31), or sera from patients with ulcerative colitis (n = 49), or sera from blood donors (n = 69) (p<0.0001, respectively). Twenty-eight (66%) and 18 (43%) of 42 PAB-positive sera demonstrated IgG and IgA reactivity to human recombinant GP2 in IIF, respectively. Patients with PAB-negative Crohn's disease (n = 31) were not reactive. GP2 mRNA transcription was significantly higher in colon biopsies from patients with Crohn's disease (n = 4) compared to patients with ulcerative colitis (n = 4) (p = 0.0286). Immunochemical staining confirmed GP2 expression in human colon biopsies from patients with Crohn's disease.
  
  
  CONCLUSIONS
  Anti-GP2 autoantibodies constitute novel Crohn's disease-specific markers, the quantification of which could significantly improve the serological diagnosis of IBD. The expression of GP2 in human enterocytes suggests an important role for anti-GP2 response in the pathogenesis of Crohn's disease.
authors: Institute of Immunology, Technical University Dresden, Fetscherstrasse 74, 01307 Dresden, Germany.
authors: D
authors: D
authors: Roggenbuck
authors: G
authors: G
authors: Hausdorf
authors: L
authors: L
authors: Martinez-Gamboa
authors: D
authors: D
authors: Reinhold
authors: T
authors: T
authors: Büttner
authors: P R
authors: PR
authors: Jungblut
authors: T
authors: T
authors: Porstmann
authors: M W
authors: MW
authors: Laass
authors: J
authors: J
authors: Henker
authors: C
authors: C
authors: Büning
authors: E
authors: E
authors: Feist
authors: K
authors: K
authors: Conrad
mesh_terms: D000328:Adult; D000368:Aged; D000818:Animals; D000918:Antibody Specificity; D001323:Autoantibodies / Q000276:immunology*; D001324:Autoantigens / Q000032:analysis* / Q000235:genetics / Q000276:immunology; D003093:Colitis, Ulcerative / Q000235:genetics / Q000276:immunology; D003106:Colon / Q000276:immunology; D003424:Crohn Disease / Q000235:genetics / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D058851:GPI-Linked Proteins; D006801:Humans; D007070:Immunoglobulin A / Q000276:immunology; D007074:Immunoglobulin G / Q000276:immunology; D008297:Male; D008562:Membrane Glycoproteins / Q000032:analysis* / Q000235:genetics / Q000276:immunology; D008875:Middle Aged; D010179:Pancreas / Q000276:immunology*; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D011994:Recombinant Proteins / Q000276:immunology; D022142:Secretory Vesicles / Q000276:immunology; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014158:Transcription, Genetic; D055815:Young Adult
chemical_list: D001323:Autoantibodies; D001324:Autoantigens; C489339:GP2 protein, human; D058851:GPI-Linked Proteins; D007070:Immunoglobulin A; D007074:Immunoglobulin G; D008562:Membrane Glycoproteins; D012333:RNA, Messenger; D011994:Recombinant Proteins