title: Antiflagellin antibodies recognize the autoantigens Toll-Like Receptor 5 and Pals 1-associated tight junction protein and induce monocytes activation and increased intestinal permeability in Crohn's disease.
abstract: OBJECTIVE
  Bacterial flagellin is considered an important antigen in Crohn's disease (CD) as it activates innate immunity through Toll-Like Receptor 5 (TLR5) engagement and induces an elevated adaptive immune response. Little is known about the presence of an autoimmune process in CD. We aimed to identify pathogenically relevant autoantigen targets in CD.
  
  
  METHODS
  We screened a random peptide library with pooled sera of patients with active CD. Transepithelial flux of [3H] mannitol in T84 human intestinal epithelial cell line was used to study the epithelial barrier function. Monocyte activation was evaluated by surface expression of activation markers and by production of pro-inflammatory cytokines. Gene modulation of T84 cells exposed to antipeptide antibodies was analysed by gene array.
  
  
  RESULTS
  We identified a peptide that shares homology with Salmonella typhimurium flagellin and with self-antigens such as TLR5 and cell junction protein, Pals 1-associated tight junction protein. The affinity-purified antipeptide antibodies recognized the self-antigens and induced increased intestinal epithelial cell permeability. Moreover, the antibodies induced monocyte activation upon binding TLR5. Finally, in cultured intestinal cells (T84) the purified antibodies induced the modulation of clusters of proinflammatory genes similar to the one induced by the engagement of TLR5 by its natural ligand flagellin.
  
  
  CONCLUSIONS
  Antibodies directed against an immunodominant peptide of flagellin recognize self-antigens and are functionally active suggesting the presence of an autoimmune process that can both facilitate loss of tolerance to intestinal microflora by increasing cell permeability and amplify the innate immunity involvement through a novel mechanism of TLR5 activation.
authors.affiliation: Section of Internal Medicine, Department of Clinical and Experimental Medicine, University of Verona, Verona, Italy. claudio.lunardi@univr.it
authors.forename: C
authors.initials: C
authors.lastname: Lunardi
authors.forename: C
authors.initials: C
authors.lastname: Bason
authors.forename: M
authors.initials: M
authors.lastname: Dolcino
authors.forename: R
authors.initials: R
authors.lastname: Navone
authors.forename: R
authors.initials: R
authors.lastname: Simone
authors.forename: D
authors.initials: D
authors.lastname: Saverino
authors.forename: L
authors.initials: L
authors.lastname: Frulloni
authors.forename: E
authors.initials: E
authors.lastname: Tinazzi
authors.forename: D
authors.initials: D
authors.lastname: Peterlana
authors.forename: R
authors.initials: R
authors.lastname: Corrocher
authors.forename: A
authors.initials: A
authors.lastname: Puccetti
mesh_terms: D000293:Adolescent; D000328:Adult; D000906:Antibodies / Q000276:immunology*; D001324:Autoantigens / Q000276:immunology; D003424:Crohn Disease / Q000276:immunology*; D005260:Female; D005408:Flagellin / Q000276:immunology*; D006801:Humans; D007413:Intestinal Mucosa / Q000166:cytology / Q000378:metabolism; D007416:Intestinal Perforation; D008213:Lymphocyte Activation; D008297:Male; D008565:Membrane Proteins / Q000276:immunology*; D008875:Middle Aged; D009000:Monocytes / Q000276:immunology*; D009703:Nucleoside-Phosphate Kinase / Q000276:immunology*; D019151:Peptide Library; D010539:Permeability; D019108:Tight Junctions / Q000276:immunology; D051198:Toll-Like Receptor 5 / Q000276:immunology*; D055815:Young Adult
chemical_list: D000906:Antibodies; D001324:Autoantigens; D008565:Membrane Proteins; D019151:Peptide Library; D051198:Toll-Like Receptor 5; D005408:Flagellin; D009703:Nucleoside-Phosphate Kinase; C501307:MPP5 protein, human