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

A central event in celiac disease (CD) is the recognition by TCRs of gluten epitopes presented by specific HLAs, with HLA-DQ2 being associated with 95% of CD cases. The molecular basis for these interactions are now revealed by crystal structures of TCRs from individuals with CD in complex with wheat gliadin epitopes presented by HLA-DQ2. 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-α1a and DQ2.5-glia-α2. We determined the ternary structures of four distinct biased TCRs specific for those epitopes. All three TCRs specific for DQ2.5-glia-α2 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 CDR3β loop acted as the lynchpin within this common docking footprint. Although the TCRs specific for DQ2.5-glia-α1a and DQ2.5-glia-α2 docked similarly, their interactions with the respective gliadin determinants differed markedly, thereby providing a basis for epitope specificity.