Heterogeneity of T cells specific for a particular peptide/HLA-DQ complex

Whether T cells specific for a particular peptide/HLA-DQ complex are restricted with respect to TCR usage has not been fully established. TCR usage of T cells specific for a peptide presented by a given HLA-DQ molecule has not been studied before. We therefore sequenced the TCR genes of five different TCCs derived from the same donor, which were specific for a p21 ras-derived synthetic peptide presented by the HLA-DQ(alpha 1*0102,beta*0602) (DQ6) molecule. We found that these T cells which recognized the same peptide/HLA-DQ complex used highly diverse TCRs. However, dose-response experiments using various truncations of the p21 ras-derived peptide revealed that the peptide fine specificities of the five TCCs were not completely identical. This may explain the heterogeneity in TCR usage.