Notch signaling is important for human CD8⁺ T cell priming. Primary naive CD8⁺ T cells were cocultured with autologous Mart-1 peptide–loaded moDCs (3 µg/mL peptide), both isolated from an HLA-A2–typed healthy donor, as described in the Methods. Inhibition of Notch during CD8⁺ T-cell priming, either via (A) GSI (10 μM) or (B) soluble DLL4-Fc (5 μg/mL) resulted in diminished expansion of Mart-1–specific CD8⁺ T cells, as reflected by A2/Mart-1-tetramer staining using flow cytometry. The results shown are from 2 different donors. Similar results were obtained in 5 independent experiments.