Inhibition of Notch signaling impairs acquisition of effector function by human CD8⁺ T cells. Human naive CD8⁺ T cells were cultured as described for Figure 2 in the presence or absence of (A) GSI (10 μM), (B) soluble DLL4-Fc (5 μg/mL), or the respective controls. Inhibition of Notch signaling during T cell priming reduced the amounts of IFNγ- and TNFα-producing CD8⁺ T cells. N = 5. (C) The inhibitory effect of GSI was independent of the strength of the stimulus; titration of the Mart-1 peptide to a lower dosage did not alter the inhibitory effect. As a measure for cytotoxic capacity, (D) intracellular levels of Granzyme B or (E) cell surface expression of CD107a was determined. Inhibition of Notch signaling reduced the expression of both cytolytic markers. Data are representative of 2 independent experiments.