title: Crossreactive autoantibodies directed against cutaneous and joint antigens are present in psoriatic arthritis.
abstract: BACKGROUND
  Psoriatic arthritis (PsA) is a chronic inflammatory disease of unknown origin, characterized by erosions and new bone formation. Diagnosis of PsA is mainly clinical and there are no biomarkers available. Moreover in PsA autoantibodies have not been described so far. Indeed an autoimmune origin has been suggested but never proven. Aim of the study was to investigate the possible presence of autoantibodies typically associated with PsA.
  
  
  METHODS
  We used pooled IgG immunoglobulins derived from 30 patients with PsA to screen a random peptide library in order to identify disease relevant autoantigen peptides.
  
  
  RESULTS
  Among the selected peptides, one was recognised by nearly all the patients' sera. The identified peptide (PsA peptide: TNRRGRGSPGAL) shows sequence similarities with skin autoantigens, such as fibrillin 3, a constituent of actin microfibrils, desmocollin 3, a constituent of the desmosomes and keratin 78, a component of epithelial cytoskeleton. Interestingly the PsA peptide shares homology with the nebulin-related anchoring protein (N-RAP), a protein localized in the enthesis (point of insertion of a tendon or ligament to the bone), which represents the first affected site during early PsA. Antibodies affinity purified against the PsA peptide recognize fibrillin, desmocollin, keratin and N-RAP. Moreover antibodies directed against the PsA peptide are detectable in 85% of PsA patients. Such antibodies are not present in healthy donors and are present in 13/100 patients with seroposive rheumatoid arthritis (RA). In seronegative RA these antibodies are detectable only in 3/100 patients.
  
  
  CONCLUSIONS
  Our results indicate that PsA is characterized by the presence of serum autoantibodies crossreacting with an epitope shared by skin and joint antigens.
authors.affiliation: Institute Giannina Gaslini, Genova, Italy.
authors.forename: Marzia
authors.initials: M
authors.lastname: Dolcino
authors.affiliation: Department of Medicine, University of Verona, Verona, Italy.
authors.forename: Claudio
authors.initials: C
authors.lastname: Lunardi
authors.affiliation: University of Genova, Genova, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Ottria
authors.affiliation: Department of Medicine, University of Verona, Verona, Italy.
authors.forename: Elisa
authors.initials: E
authors.lastname: Tinazzi
authors.affiliation: Department of Medicine, University of Verona, Verona, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Patuzzo
authors.affiliation: Institute Giannina Gaslini, Genova, Italy; University of Genova, Genova, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Puccetti
mesh_terms: D015535:Arthritis, Psoriatic / Q000276:immunology*; D001323:Autoantibodies / Q000276:immunology / Q000302:isolation & purification*; D001324:Autoantigens / Q000276:immunology*; D015153:Blotting, Western; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology*; D007596:Joints / Q000276:immunology*; D019151:Peptide Library; D012867:Skin / Q000276:immunology*
chemical_list: D001323:Autoantibodies; D001324:Autoantigens; D007074:Immunoglobulin G; D019151:Peptide Library