| Popis: |
Signal transduction through the αβ CD3 T cell receptor (TCR) can induce vastly different cellular responses at different stages of T cell differentiation. The earliest form of TCR mediated signalling is seen in immature CD4+8 thymocytes in which ligation of CD3e induces maturation to the CD4+8 double positive (DP) stage (Levelt et al., 1992). At the DP stage, signal transduction through the TCR leads to negative or positive selection, corresponding either to deletion of the thymocytes or to their further maturation to CD4+ or CD8+ single positive (SP) mature thymocytes (v. Boehmer, 1988). Signal transduction through the TCR of resting peripheral T cells leads, under most circumstances, to induction of transcriptional activities and of cell division, i.e. to activation. Activated T cells are again able to respond to TCR signalling, mostly by secretion or exocytosis of preformed or de novo synthetized effector molecules (reviewed in Moller, 1989). |
