title: Analysis of the specificity of anti-PM-Scl autoantibodies.
abstract: OBJECTIVE
  To compare the specificity of anti-PM-Scl autoantibodies in serum samples from 43 patients with myositis, scleroderma, or both.
  
  
  METHODS
  Anti-PM-Scl immunoprecipitates from HeLa cell extract were used as antigen for immunoblot analyses to determine the antigenic components. A series of complementary DNA fragments was expressed in Escherichia coli for immunoblot examination of the reaction with the 100-kd protein.
  
  
  RESULTS
  The immunoblot against immunoprecipitates was sensitive and specific for detecting reactions with components of the PM-Scl antigen: 42 of 43 sera (97.7%) reacted with the 100-kd, 27 of 43 (62.8%) with the 70-kd, and 5 of 43 (11.6%) with the 37-kd protein (not previously recognized as antigenic). Forty-one sera reacted with N-terminal protein S1 (amino acids 11-437), 39 with central protein S2 (amino acids 439-749), and 24 with C-terminal protein S3 (amino acids 750-882). Of 42 sera tested, 28 (66.7%) reacted most strongly with S1, and 6 (14.3%) reacted most strongly with S2. Absorption studies implied additional, conformational epitopes not present on the bacterially expressed antigen.
  
  
  CONCLUSIONS
  There was an overall similarity in reactivity to the PM-Scl antigen, but there were differences in the reactivity to the 70-kd and 37-kd proteins, as well as in the relative strength of the reactivity to the S2 protein.
authors.affiliation: Oklahoma Medical Research Foundation, Oklahoma City 73104.
authors.forename: Q
authors.initials: Q
authors.lastname: Ge
authors.forename: Y
authors.initials: Y
authors.lastname: Wu
authors.forename: E P
authors.initials: EP
authors.lastname: Trieu
authors.forename: I N
authors.initials: IN
authors.lastname: Targoff
mesh_terms: D000888:Antibodies, Anti-Idiotypic / Q000502:physiology*; D000918:Antibody Specificity; D000937:Antigen-Antibody Reactions / Q000502:physiology; D001324:Autoantigens / Q000276:immunology*; D005095:Exoribonucleases; D063326:Exosome Multienzyme Ribonuclease Complex; D006801:Humans; D015151:Immunoblotting; D009220:Myositis / Q000097:blood / Q000276:immunology*; D020648:Peptide Elongation Factor 1; D010445:Peptide Elongation Factors / Q000276:immunology; D011994:Recombinant Proteins / Q000276:immunology; D012595:Scleroderma, Systemic / Q000097:blood / Q000276:immunology*
chemical_list: D000888:Antibodies, Anti-Idiotypic; D001324:Autoantigens; D020648:Peptide Elongation Factor 1; D010445:Peptide Elongation Factors; D011994:Recombinant Proteins; D005095:Exoribonucleases; D063326:Exosome Multienzyme Ribonuclease Complex; C077044:EXOSC10 protein, human