title: Immunoblotting detection of so-called 'antikeratin antibodies': a new assay for the diagnosis of rheumatoid arthritis.
abstract: OBJECTIVE
  To assess the diagnostic value for rheumatoid arthritis (RA), of an immunoblotting assay based on the rat oesophagus epithelium antigens recognised by the so-called 'antikeratin antibodies' ('AKA'), antigens that have been identified as three non-cytokeratin proteins (referred to as A, B and C proteins).
  
  
  METHODS
  After polyacrylamide gel electrophoresis in non-denaturing conditions and electrotransfer of an epithelial extract, the immunoreactivities to the A, B and C proteins of a series of serum samples from 88 patients with RA and 100 patients with non-rheumatoid rheumatic diseases, were semiquantitatively evaluated.
  
  
  RESULTS
  A total of 81.8% of RA serum samples recognised the three proteins, while 91% of non-RA serum samples only weakly recognised the A and B proteins but not the C protein. Only in the group of RA patients, were the titres of the antibodies to the A, B and C proteins found to be significantly correlated with each other and with the titres of 'AKA' detected by the standard indirect immunofluorescence (IIF) method. For a diagnostic specificity of 99%, the diagnostic sensitivities of the detection of the A and B proteins were 50% and 43.2%, respectively, when those of the detection of 'AKA' by IIF and of IgM-rheumatoid factor by enzyme-linked immunosorbent assay were 42% and 54%, respectively. In contrast, at a same specificity of 99%, the diagnostic sensitivity of the detection of the C protein was significantly higher with a value of 70.5%.
  
  
  CONCLUSIONS
  This immunoblotting assay which is the first immunochemical method proposed for the detection of 'AKA, should be validated on larger series of patients but can already be considered as a very powerful test for the serological diagnosis of RA.
authors.affiliation: Department of Biology and Pathology of the Cell, Purpan School of Medicine, University of Toulouse III, France.
authors.forename: V
authors.initials: V
authors.lastname: Gomès-Daudrix
authors.forename: M
authors.initials: M
authors.lastname: Sebbag
authors.forename: E
authors.initials: E
authors.lastname: Girbal
authors.forename: C
authors.initials: C
authors.lastname: Vincent
authors.forename: M
authors.initials: M
authors.lastname: Simon
authors.forename: J
authors.initials: J
authors.lastname: Rakotoarivony
authors.forename: M
authors.initials: M
authors.lastname: Abbal
authors.forename: B
authors.initials: B
authors.lastname: Fournié
authors.forename: G
authors.initials: G
authors.lastname: Serre
mesh_terms: D001172:Arthritis, Rheumatoid / Q000175:diagnosis* / Q000276:immunology; D001323:Autoantibodies / Q000097:blood*; D001324:Autoantigens / Q000276:immunology; D004591:Electrophoresis, Polyacrylamide Gel; D004848:Epithelium / Q000276:immunology; D004947:Esophagus / Q000276:immunology; D006801:Humans; D015151:Immunoblotting / Q000379:methods*; D007633:Keratins / Q000276:immunology*; D012217:Rheumatoid Factor / Q000097:blood; D012680:Sensitivity and Specificity
chemical_list: D001323:Autoantibodies; D001324:Autoantigens; D007633:Keratins; D012217:Rheumatoid Factor