Figure 4.

Immature DCs matured via necrotic supernatants are able to induce antigen-specific CD8⁺ effector cells. Cocultures of immature DCs were supplemented with nothing, MCM, or supernatants (sup) of apoptotic (UVB-irradiated B-LCL) or necrotic (frozen–thawed B-LCL) cells and incubated for 48 h. They were collected, unpulsed or pulsed with 1 μg/ml influenza matrix peptide for 1 h, and cocultured with 2 × 10⁵ syngeneic T cells at a ratio of 1:30 for 7 d to allow for the activation of CD8⁺ effector cells. Responding T cells were collected and restimulated with autologous DCs that were untreated or pulsed with matrix peptide (MP) for 18 h. The induction of influenza matrix peptide–specific CD8⁺ T cells was measured in an IFN-γ ELISPOT assay (A). Alternatively, 7-d cocultures were directly tested for matrix peptide–specific CTL activity in a 4-h chromium-release assay using matrix peptide–pulsed T2 cells as targets (B). Results are representative of three experiments, and the values shown represent the mean of triplicate wells.