The role of glutamic or aspartic acid in position four of the epitope binding motif and thyrotropin receptor-extracellular domain epitope selection in Graves' disease

J Clin Endocrinol Metab. 2010 Jun;95(6):2909-16. doi: 10.1210/jc.2009-2393. Epub 2010 Apr 14.


Context: Development of Graves' disease (GD) is related to HLA-DRB1*0301 (DR3),and more specifically to arginine at position 74 of the DRB1 molecule. The extracellular domain (ECD) of human TSH receptor (hTSH-R) contains the target antigen.

Objective and design: We analyzed the relation between hTSH-R-ECD peptides and DR molecules to determine whether aspartic acid (D) or glutamic acid (E) at position four in the binding motif influenced selection of functional epitopes.

Results: Peptide epitopes from TSH-R-ECD with D or E in position four (D/E+) had higher affinity for binding to DR3 than peptides without D/E (D/E-) (IC(50) 29.3 vs. 61.4, P = 0.0024). HLA-DR7, negatively correlated with GD, and DRB1*0302 (HLA-DR18), not associated with GD, had different profiles of epitope binding. Toxic GD patients who are DR3+ had higher responses to D/E+ peptides than D/E- peptides (stimulation index 1.42 vs. 1.22, P = 0.028). All DR3+ GD patients (toxic + euthyroid) had higher responses, with borderline significance (Sl; 1.32 vs. 1.18, P = 0.051). Splenocytes of DR3 transgenic mice immunized to TSH-R-ECD responded to D/E+ peptides more than D/E- peptides (stimulation index 1.95 vs. 1.69, P = 0.036). Seven of nine hTSH-R-ECD peptide epitopes reported to be reactive with GD patients' peripheral blood mononuclear cells contain binding motifs with D/E at position four.

Conclusions: TSH-R-ECD epitopes with D/E in position four of the binding motif bind more strongly to DRB1*0301 than epitopes that are D/E- and are more stimulatory to GD patients' peripheral blood mononuclear cells and to splenocytes from mice immunized to hTSH-R. These epitopes appear important in immunogenicity to TSH-R due to their favored binding to HLA-DR3, thus increasing presentation to T cells.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Amino Acid Substitution
  • Animals
  • Antigen Presentation
  • Aspartic Acid / immunology*
  • Epitopes / immunology*
  • Extracellular Space / immunology*
  • Glutamic Acid / immunology*
  • Graves Disease / immunology*
  • HLA Antigens / metabolism
  • HLA-DR Antigens / immunology
  • HLA-DR Antigens / metabolism
  • HLA-DR3 Antigen / immunology
  • HLA-DR7 Antigen / immunology
  • Humans
  • Immunization
  • Lymphocytes / drug effects
  • Lymphocytes / immunology
  • Mice
  • Receptors, Thyrotropin / immunology*


  • Epitopes
  • HLA Antigens
  • HLA-DR Antigens
  • HLA-DR3 Antigen
  • HLA-DR7 Antigen
  • Receptors, Thyrotropin
  • Aspartic Acid
  • Glutamic Acid