FIGURE 6.

Blocking Notch signaling attenuates the CTL activity of OVA-specific CD8⁺ T cells. A, C57BL/6 mice were immunized with E.G7-OVA cells (box symbols) or EL4 cells, as a mock control (triangles). After 16 days, we harvested splenocytes from these mice, pretreated them in vitro with DMSO (filled symbols) or with GSI (open symbols), and stimulated them with OVA-specific E.G7 cells for 5 days. Live CD8⁺ T cells were isolated and an Ag-specific cytotoxicity assay, using europium (Eu)-loaded target cells, was used to determine the percentage of specific lysis. B, C57BL/6 mice were fed control chow or chow containing GSI (LY chow) beginning 3 days before immunizing with E.G7-OVA (box symbols) or EL4 (triangles) cells and continuing until splenocytes were harvested 16 days later. Splenocytes were stimulated with OVA-specific E.G7 cells for 5 days, live CD8⁺ T cells isolated from the splenocytes of control-fed (closed symbols) and GSI-fed (open symbols) mice and the europium cytotoxicity assay was performed as in A. For specific lysis, 5000 target cells (T), OVA-specific E.G7-OVA, or EL4 (as control) were used with 25,000, 50,000, or 100,000 effector (E) CD8⁺ cells, for E:T ratios of 5:1, 10:1, and 20:1, respectively. Results shown in the cytotoxicity assays represent the mean ± SD of three independent replicates. Data are representative of three independent replicates.