title: A Molecular Analysis of the Shared Epitope Hypothesis: Binding of Arthritogenic Peptides to DRB1*04 Alleles.
abstract: The shared epitope hypothesis posits that amino acids QR/KRAA in positions 70-74 of the DRΒ1 chain are responsible for rheumatoid arthritis susceptibility. However, even DRB1*04 alleles containing the shared epitope vary greatly with respect to degrees of susceptibility. This study was undertaken to conduct a molecular examination of the shared epitope hypothesis by measuring binding of arthritogenic peptides to susceptibility and resistance alleles.
  
  
  
  We measured binding of native and citrullinated forms of vimentin(66-78) and α-enolase(11-25) and noncitrullinated type II collagen(258-272) to 88 class II alleles on Luminex beads (which includes alleles of many varying degrees of susceptibility and resistance). We expressed DRΒ1*04:01, *04:02, and *08:01 in T2 cells and mutated DRΒ1*04:01 at positions 67, 70, 71, 74, and 86 to corresponding residues in DRB1*04:02, *04:03, *04:04, *04:05, and *08:01. Finally, we measured responses of 4 DRΒ1*04:01 restricted collagen(258-272) T cell hybridomas against wild-type DRΒ1*04:01, *04:02, and all mutated alleles.
  
  
  
  The most susceptible allele, DRΒ1*04:01, preferentially bound citrullinated vimentin(66-78) and citrullinated α-enolase(11-25) over the native forms. DRΒ1*04:02 exhibited no preference for citrullinated peptides, and *08:01 preferred native peptides. Similarly, DRB1*04:01 bound collagen(258-272) , but *04:02 and *08:01 did not. Mutating DRΒ1*04:01 at positions 70, 71, 74, and 86 to the corresponding residues in DRΒ1*04:02 or *08:01 dramatically reduced the specificity for citrullinated peptides and collagen(258-272) binding.
  
  
  
  These observations demonstrate that while amino acids at positions 70, 71, and 74 within the shared epitope in DRΒ1 mediate binding and T cell responses of arthritogenic peptides, position 86 outside the shared epitope also plays a critical role.
authors: ClinImmune Labs and University of Colorado Anschutz Medical Campus, Aurora.
authors: Kirsten M
authors: KM
authors: Anderson
authors: ClinImmune Labs and University of Colorado Anschutz Medical Campus, Aurora.
authors: Christina L
authors: CL
authors: Roark
authors: ClinImmune Labs and University of Colorado Anschutz Medical Campus, Aurora.
authors: Mary
authors: M
authors: Portas
authors: ClinImmune Labs and University of Colorado Anschutz Medical Campus, Aurora.
authors: Michael T
authors: MT
authors: Aubrey
authors: Memphis VA Medical Center, Memphis, Tennessee.
authors: Edward F
authors: EF
authors: Rosloniec
authors: ClinImmune Labs and University of Colorado Anschutz Medical Campus, Aurora.
authors: Brian M
authors: BM
authors: Freed
mesh_terms: D001172:Arthritis, Rheumatoid / Q000235:genetics*; D002478:Cells, Cultured; D000939:Epitopes / Q000235:genetics*; D020022:Genetic Predisposition to Disease; D059811:HLA-DRB1 Chains / Q000235:genetics*; D006801:Humans; D010455:Peptides / Q000235:genetics
chemical_list: D000939:Epitopes; D059811:HLA-DRB1 Chains; C527195:HLA-DRB1*04 antigen; D010455:Peptides