title: Antibodies to N-homocysteinylated albumin and haemoglobin in patients with rheumatoid arthritis: a potential new marker of disease severity.
abstract: OBJECTIVE
  To investigate whether anti-Nε-homocysteinylated albumin (anti-N-Hcy-Alb) and haemoglobin (anti-N-Hcy-Hb) antibodies occur in rheumatoid arthritis (RA) and whether they are associated with RA activity and/or severity.
  
  
  METHODS
  Plasma total homocysteine (tHcy) and serum anti-N-Hcy-Alb and -Hb antibodies levels were determined in 76 RA patients (12 men and 64 women, median age 56 years) and 80 age- and sex-matched controls.
  
  
  RESULTS
  RA patients compared to healthy controls demonstrated elevated tHcy [median (IQR), 13.20 (3.80) vs. 9.45 (3.25) μmol/L; p < 0.000001] and anti-N-Hcy-Alb and -Hb antibodies [absorbance at 490 nm, median (IQR), 0.546 (0.085) vs. 0.452 (0.056) and 0.649 (0.106) vs. 0.532 (0.057), respectively; all p < 0.000001]. In RA patients, RA radiological class was a strong independent predictor of tHcy [β (SE), 0.59 (0.11); p = 0.000001] and anti-N-Hcy-Alb [0.36 (0.12); p = 0.003] and -Hb [0.49 (0.11); p = 0.00007] antibodies. The number of swollen joints, but not C-reactive protein (CRP), interleukin 6 (IL-6), positive rheumatoid factor (RF), or anti-cyclic citrullinated peptide (anti-CCP) antibodies, showed independent effects on anti-N-Hcy-Alb [β (SE), 0.36 (0.11); p = 0.001] and -Hb [0.25 (0.11); p = 0.02] antibodies. Anti-N-Hcy-Hb antibodies, but not those against N-Hcy-Alb, were positively correlated with RA functional class and RA duration. No effect of any medications on tHcy or anti-N-Hcy-protein antibodies was observed.
  
  
  CONCLUSIONS
  This study is the first to show that RA is characterized by enhanced autoimmune response to Nε-homocysteinylated proteins detectable in circulating blood, which is related to some clinical measures of RA severity.
authors.affiliation: Institute of Rheumatology , Warsaw , Poland.
authors.forename: A
authors.initials: A
authors.lastname: Nowakowska-Plaza
authors.forename: D P
authors.initials: DP
authors.lastname: Potaczek
authors.forename: P
authors.initials: P
authors.lastname: Gluszko
authors.forename: A
authors.initials: A
authors.lastname: Undas
mesh_terms: D000328:Adult; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000097:blood / Q000175:diagnosis* / Q000276:immunology*; D001323:Autoantibodies / Q000097:blood* / Q000276:immunology; D015415:Biomarkers / Q000097:blood; D005260:Female; D006454:Hemoglobins / Q000276:immunology*; D006710:Homocysteine / Q000031:analogs & derivatives* / Q000276:immunology; D006801:Humans; D008297:Male; D008875:Middle Aged; D012709:Serum Albumin / Q000276:immunology*; D012720:Severity of Illness Index
chemical_list: D001323:Autoantibodies; D015415:Biomarkers; D006454:Hemoglobins; C502359:N-homocysteinylated albumin; D012709:Serum Albumin; D006710:Homocysteine