Notch signaling is required for induction of an innate T cell development program in human thymus. Homo sapiens

CD4 CD8 double positive (DP) thymocytes progressively shut down Notch signaling after β-selection allowing progression of the DP program and positive selection of conventional CD4 and CD8 single positive T cells. In contrast, innate CD8+ T cells are selected from DP precursors shortly after β-selection. Here, we investigated whether notch signaling is required for the initiation of the innate T cell developmental program upon TCR engagement. We show that, after β-selection, Notch activation limits progression to late DP cells and favors the development of TCRαβ/CD3 expressing CD8dim early DP progenitors. TCR engagement in these Notch dependent TCRαβ+ early DP precursors does not induce prominent apoptosis, but rather induces T-bet expression by an mTOR-dependent mechanism. Our findings indicate that Notch signaling drives the launch of an innate effector program in response to TCR agonist selection in the thymus. Overall design: Three samples are analyzed. The first sample comes from native thymus tissue. CD34+ postnatal thymocytes were transduced to express either TCRalpha (second sample) or TCRbeta (third sample). Subsequently, the transduced thymocytes were cultured on OP9-DL1 cells. When the cells were double positive, the cells were harvested sorted for immature CD3+ DP cells transgenic for the TCR.