MHC-independent T cells

胸腺产生仅识别与MHC或MHC样分子相关的抗原配体的MHC限制性abT细胞。我们假设，在胸腺选择过程中，CD 4和CD 8辅助受体可能对更广泛的abTCR库施加MHC特异性，因为它们结合并有效地隔离酪氨酸激酶Lck，从而阻止不参与任一辅助受体的非MHC配体的TCR信号传导。使用缺乏CD 4和CD 8以及MHC（Quad-deficient）的小鼠，我们证实在体内没有辅助受体的情况下，ab胸腺细胞可以通过非MHC配体发出信号。此外，我们通过将CD 4转基因引入Quad-deficient小鼠来测试辅助受体的关键作用。然而，野生型CD 4对Lck的隔离阻断了ab型胸腺细胞上非MHC配体的信号传导，而引入无尾形式的CD 4则没有。我们的结论是，在没有LCK螯合辅受体，胸腺细胞可以通过非MHC配体的信号。因此，⑶ 4及⑶ 8通过防止胸腺细胞被非MHC配体选择而对广泛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.