MHC-independent T cells

胸腺产生 MHC 限制性 abT 细胞，仅识别与 MHC 或 MHC 样分子相关的抗原配体。我们假设 CD4 和 CD8 辅助受体可能在胸腺选择过程中对更广泛的 abTCR 库施加 MHC 特异性，因为它们结合并有效隔离酪氨酸激酶 Lck，从而阻止不与任一辅助受体结合的非 MHC 配体的 TCR 信号传导。使用 CD4 和 CD8 以及 MHC（四缺陷）缺陷的小鼠，我们发现在体内缺乏辅助受体的情况下，ab 胸腺细胞可以通过非 MHC 配体发出信号。此外，我们通过将 CD4 转基因引入 Quad 缺陷小鼠中来测试辅助受体的关键作用。野生型 CD4 对 Lck 的隔离会阻断 ab 胸腺细胞上非 MHC 配体的信号传导，而引入无尾形式的 CD4 则不会。我们得出的结论是，在缺乏辅助受体 Lck 隔离的情况下，胸腺细胞可以通过非 MHC 配体发出信号。因此，CD4 和 CD8 通过阻止胸腺细胞被非 MHC 配体选择，对广泛的 abTCR 库施加 MHC 特异性。

The thymus produces MHC-restricted abT cells that only recognize antigenic ligands in association with MHC or MHC-like molecules. We hypothesized that CD4 and CD8 coreceptors might be impose MHC-specificity on a broader abTCR repertoire during thymic selection because they bind and effectively sequester the tyrosine kinase Lck, thereby preventing TCR signaling by non-MHC ligands that do not engage either coreceptor. Using mice deficient for both CD4 and CD8 as well as MHC (Quad-deficient), we discoverd that ab thymocytes can be signaled by non-MHC ligands in the absence of coreceptors in vivo. In addition, we tested the critical role of coreceptors by introducing CD4 transgenes into Quad-deficient mice. Whereas sequestration of Lck by wild-type CD4 blocked signaling by non-MHC ligands on ab thymocytes, introducing a tailless form of CD4 didnt. We conclude that in the absence of Lck sequestration by coreceptors, thymocytes can be signaled by non-MHC ligands. Therefore, CD4 and CD8 impose MHC-specificity on a broad abTCR repertoire by preventing thymocytes to be selected by non-MHC ligands.