T-cell receptor recognition of HLA-DQ2-gliadin complexes associated with celiac disease

Celiac disease is a T cell-mediated disease induced by dietary gluten, a component of which is gliadin. 95 of individuals with celiac disease carry the HLA (human leukocyte antigen)-DQ2 locus. Here we determined the T-cell receptor (TCR) usage and fine specificity of patient-derived T-cell clones specific for two epitopes from wheat gliadin, DQ2.5-glia-alpha1a and DQ2.5-glia-alpha2. We determined the ternary structures of four distinct biased TCRs specific for those epitopes. All three TCRs specific for DQ2.5-glia-alpha2 docked centrally above HLA-DQ2, which together with mutagenesis and affinity measurements provided a basis for the biased TCR usage. A non-germline encoded arginine residue within the CDR3beta loop acted as the lynchpin within this common docking footprint. Although the TCRs specific for DQ2.5-glia-alpha1a and DQ2.5-glia-alpha2 docked similarly, their interactions with the respective gliadin determinants differed markedly, thereby providing a basis for epitope specificity.