title: New classification of the shared epitope in rheumatoid arthritis: impact on the production of various anti-citrullinated protein antibodies.
abstract: OBJECTIVE
  HLA-DR [shared epitope (SE)] alleles have recently been re-classified into S1, S2, S3P and S3D groups. S2 and S3P have been associated with increased risk for RA. We assessed the impact of S1, S2, S3P and S3D alleles on anti-citrullinated protein antibody (ACPA) production. Instead of comparing allele-carriers to non-carriers, we studied each allele group individually, using the X/X (non-SE) genotype as reference.
  
  
  METHODS
  Serum and genomic DNA samples of 91 RA patients and 78 healthy controls were obtained. Various ACPAs and IgM RF were determined by ELISA. HLA-DRB1 genotyping and subtyping was performed by PCR. HLA-DRB1 alleles were re-classified as described above. Correlations between SE and ACPAs were determined.
  
  
  RESULTS
  Not only S2 and S3P, but, to a lesser extent, S1 and S3D alleles also predisposed to anti-cyclic citrullinated peptide (CCP) production (P < 0.0001, P = 0.004, P = 0.01 and P = 0.027, respectively), with the following hierarchy of association: S2+S3P > S1+S3D > X/X. Similar associations were observed for anti-citrullinated vimentin. Anti-citrullinated fibrinogen (CF) exerted a different association pattern with the strongest correlation with S1 alleles [odds ratio (OR) 16.00; P = 0.05]. In addition, HLA-DRB1*15 alleles may represent a special predisposing effect for anti-CF antibody production. Finally, in this study, RF production was associated only with the HLA-DRB1*0401 SE allele (P = 0.04).
  
  
  CONCLUSIONS
  Our approach of comparing individual S allele carriers with X/X genotype patients allowed us to perform unequivocal analyses and demonstrate new associations. Thus, novel subgroups of RA could be identified with potential relevance for prognosis and therapy.
authors.affiliation: Laboratory of Immunology, 3rd Department of Medicine, University of Debrecen Medical and Health Science Center, 98 Nagyerdei street, Debrecen, H-4012, Hungary.
authors.forename: Agnes
authors.initials: A
authors.lastname: Gyetvai
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Szekanecz
authors.forename: Lilla
authors.initials: L
authors.lastname: Soós
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Szabó
authors.forename: Andrea
authors.initials: A
authors.lastname: Fekete
authors.forename: Anikó
authors.initials: A
authors.lastname: Kapitány
authors.forename: Marius
authors.initials: M
authors.lastname: Teodorescu
authors.forename: Sándor
authors.initials: S
authors.lastname: Sipka
authors.forename: Gyula
authors.initials: G
authors.lastname: Szegedi
authors.forename: Gabriella
authors.initials: G
authors.lastname: Lakos
mesh_terms: D000328:Adult; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000235:genetics / Q000276:immunology*; D001323:Autoantibodies / Q000096:biosynthesis*; D000939:Epitopes / Q000276:immunology*; D005260:Female; D005787:Gene Frequency; D020022:Genetic Predisposition to Disease; D005838:Genotype; D006684:HLA-DR Antigens / Q000235:genetics* / Q000276:immunology; D059811:HLA-DRB1 Chains; D006579:Heterozygote; D006801:Humans; D008297:Male; D008875:Middle Aged; D010456:Peptides, Cyclic / Q000276:immunology*; D012217:Rheumatoid Factor / Q000032:analysis; D012307:Risk Factors
chemical_list: D001323:Autoantibodies; D000939:Epitopes; D006684:HLA-DR Antigens; D059811:HLA-DRB1 Chains; C553505:HLA-DRB1*04:01 antigen; D010456:Peptides, Cyclic; C487763:cyclic citrullinated peptide; D012217:Rheumatoid Factor