Immature single-positive CD8+ thymocytes represent the transition from Notch-dependent to Notch-independent T-cell development.

Early in T-cell development, cells proceed through stages that are critically dependent on signaling through the Notch receptor. As cells mature, thymocytes transition from being Notch dependent to being Notch independent, but the stage of development during which this transition occurs is unknown. We used an in vitro differentiation system in which thymocytes can be cultured in the presence or absence of a Notch ligand to identify the stage of development in which thymocytes transition from being Notch responsive to Notch non-responsive.