Figure 7
CTL-mediated tumor-specific cytotoxicityin vitroand abrogation by the depletion of immune cell subsetsin vivo.(A)51Cr-release assay. LL/2 cells were labeled with 51Cr and incubated with activated T cells isolated from mice immunized with vaccines or naive mice at 80:1, 40:1, 20:1 and 10:1 T: E ratios for 4 hours. Spleen T lymphocytes derived from mice treated with vaccine co-expression IL-18 and GM-CSF showed higher cytotoxicity against parental LL/2 cells than those from the other groups. Each data point indicates means ± SD. Experiments were performed in triplicate and repeated three times. **P < 0.01. (B-F) Antitumor immunity was abrogated by anti-CD4 (GK1.5), anti-CD8 (clone2.43), anti-NK (PK136) monoclonal antibody (mAb) produced in hybridoma cell and isotype control rat IgG for 6 times, respectively. Tumor volume was measured. Depletion of CD4 T lymphocytes (C) and CD8 T lymphocytes (D) showed complete abrogation of the antitumor activity of vaccine co-expression IL-18 and GM-CSF (P > 0.05, n = 7). In contrast, treatment with anti-NK (E) or isotype rat IgG (F) had no effect (P < 0.01, n = 7). Each data point indicates means ± SD.