Figure 4.

The role of CD4⁺ T cells and cytokines in priming tumor-specific CTL. Wild-type, CD4^−/−, γ-IFN^−/−, and IL-4^−/− mice were vaccinated with 10⁶ irradiated (50 Gy) B16-GM-CSF tumor cells. After 2 wk, splenocytes were isolated and cultured for 7 d with 5 μg/ml TRP-2 peptide and 10 U/ml IL-2. On day 7, live T cells were incubated with ⁵¹Cr-labeled MC57G targets at the indicated effector to target ratios in the presence of 1 μg/ml TRP-2 peptide or irrelevant peptide. The percent peptide-specific lysis is calculated as the difference between the percent specific lysis due to the TRP-2 peptide and the percent specific lysis due to the irrelevant peptide.