Mature T cells bearing αβ T cell receptors react with foreign antigens bound to alleles of major histocompatibility complex proteins (MHC) that they were exposed to during their development in the thymus, a phenomenon known as positive selection. The structural basis for positive selection has long been debated. Here, using mice expressing one of two different T cell receptor β chains and various MHC alleles, we show that positive selection-induced MHC bias of T cell receptors is affected both by the germline encoded elements of the T cell receptor α and β chain and, surprisingly, dramatically affected by the non germ line encoded portions of CDR3 of the T cell receptor α chain. Thus, in addition to determining specificity for antigen, the non germline encoded elements of T cell receptors may help the proteins cope with the extremely polymorphic nature of major histocompatibility complex products within the species.

带有αβT细胞受体的成熟T细胞与外源抗原反应，这些抗原与在胸腺发育过程中接触的主要组织相容性复合蛋白（MHC）等位基因结合，这种现象称为阳性选择。积极选择的结构基础长期以来一直在争论。在这里，我们使用表达两个不同T细胞受体β链和各种MHC等位基因之一的小鼠，表明正选择诱导的T细胞受体MHC偏向性受T细胞受体α和β链的种系编码元件的影响，以及令人惊讶地，T细胞受体α链的CDR3的非种系编码部分极大地影响了它。因此，除了确定对抗原的特异性外，