.tcr/cd3 Mediated T Cell Activation And Apoptotic Signal Transduction Pathway

TCR/CD3 complex signaling results in both activation and apoptosis. Previous studies in our lab showed that stable transfectant expressing a chimeric protein (CD8ε) fused extracellular and transmembrane domains of CD8α and intracellular domain of CD3ε could induce cell death by apoptosis of T lymphocytes stimulated with anti-CD8 mAb. The Jurkat cells with expression of wild-type chimeric CD8ε were termed as TJK. The Jurkat cells with expression of mutations of Y170F and Y181F in CD3e-ITAM were termed as T1JK, T2JK, and T3JK, respectively. Anti-CD8 mAb induced TJK to death by AICD, but T1JK, T2JK, and T3JK fail to death under the same condition, suggesting that CD3ε induces activation-induced cell death (AICD) independently, and Y170 and Y181 of CD3ε-ITAM are necessary for this process.In this thesis, the involvements of PI3K/Akt and Ras/Raf signal pathway during activation-induced apoptosis mediated by CD3ε were studied. And the functions of the two tyrosines in the CD3ε-ITAM were explored. The results showed that the expression and kinase activity of were increased in the wild type of TJK, while there was no visible change of PI3K/Akt kinase activity in the tyrosine-mutated cells. Wortmannin, a specific inhibitor for PI3K could inhibit the expression and kinase activity of Akt. Furthermore, it could block the activation of CPP32 and the TJK fails to death. When TJK was transfected by dominant negative PI3K plasmid DNA of CMV-myc-Δp110, CPP32 was obviously inhibited in the cells stimulated by anti-CD8 mAb, suggesting that both activation and apoptosis of T lymphocytes could be regulated well by...