title: Autoantibodies against the catalytic domain of BRAF are not specific serum markers for rheumatoid arthritis.
abstract: BACKGROUND
  Autoantibodies to the catalytic domain of v-raf murine sarcoma viral oncogene homologue B1 (BRAF) have been recently identified as a new family of autoantibodies involved in rheumatoid arthritis (RA). The objective of this study was to determine antibody responses to the catalytic domain of BRAF in RA and other autoimmune diseases. The association between RA-related clinical indices and these antibodies was also assessed.
  
  
  RESULTS
  The presence of autoantibodies to the catalytic domain of BRAF (anti-BRAF) or to peptide P25 (amino acids 656-675 of the catalytic domain of BRAF; anti-P25) was determined in serum samples from patients with RA, primary Sjögren's syndrome (pSS), systemic lupus erythematosus (SLE), and healthy controls by using indirect enzyme-linked immunosorbent assays (ELISAs) based on the recombinant catalytic domain of BRAF or a synthesized peptide, respectively. Associations of anti-BRAF or anti-P25 with disease variables of RA patients were also evaluated. Our results show that the BRAF-specific antibodies anti-BRAF and anti-P25 are equally present in RA, pSS, and SLE patients. However, the erythrocyte sedimentation rate (ESR) used to detect inflammation was significantly different between patients with and without BRAF-specific antibodies. The anti-BRAF-positive patients were found to have prolonged disease, and active disease occurred more frequently in anti-P25-positive patients than in anti-P25-negative patients. A weak but significant correlation between anti-P25 levels and ESRs was observed (r = 0.319, p = 0.004).
  
  
  CONCLUSIONS
  The antibody response against the catalytic domain of BRAF is not specific for RA, but the higher titers of BRAF-specific antibodies may be associated with increased inflammation in RA.
authors.affiliation: National Center for Clinical Laboratories, Beijing Hospital, Beijing, People's Republic of China.
authors.forename: Wenli
authors.initials: W
authors.lastname: Li
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.forename: Shipeng
authors.initials: S
authors.lastname: Sun
authors.forename: Yu
authors.initials: Y
authors.lastname: Sun
authors.forename: Yang
authors.initials: Y
authors.lastname: Pan
authors.forename: Lunan
authors.initials: L
authors.lastname: Wang
authors.forename: Rui
authors.initials: R
authors.lastname: Zhang
authors.forename: Kuo
authors.initials: K
authors.lastname: Zhang
authors.forename: Jinming
authors.initials: J
authors.lastname: Li
mesh_terms: D000917:Antibody Formation / Q000276:immunology; D000918:Antibody Specificity / Q000276:immunology; D001172:Arthritis, Rheumatoid / Q000097:blood* / Q000276:immunology*; D001323:Autoantibodies / Q000276:immunology*; D015415:Biomarkers / Q000378:metabolism; D001799:Blood Sedimentation; D016022:Case-Control Studies; D020134:Catalytic Domain / Q000276:immunology*; D003710:Demography; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D006801:Humans; D008875:Middle Aged; D048493:Proto-Oncogene Proteins B-raf / Q000097:blood / Q000737:chemistry* / Q000276:immunology*; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism
chemical_list: D001323:Autoantibodies; D015415:Biomarkers; D011994:Recombinant Proteins; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf