Figure 5. NK and CD8⁺ T cells as well as IFNγ and perforin were required for the antitumor effect of IL-33.

(A) 1×10⁵ 4T1-vector or 4T1-IL-33 cells were injected into the mammary fat pad of BALB/c mice. 30 days after inoculation, CD8⁺ T cells were purified from the spleens of these mice and re-stimulated with irradiated 4T1 cells for 72h. The level of IFNγ was then measured by ELISA. Results are mean ±SEM of three independent experiments. *P<0.05, two-tailed unpaired Student’s t-test. (B) Mice were inoculated i.d. with 1×10⁵ 4T1 tumor cells (n = 5). These mice were injected intraperitoneally with anti-CD8, or anti-asialo GM1 antibodies, or control IgG four times before and after tumor inoculation (day -2, 1, 7, 14). Kaplan-Meier survival curves are shown and the Log-Rank test was performed. P=0.0018. (C) 2×10⁵ B16-vector or B16-IL-33 cells were injected i.d. into WT B6, IFNγ−/− B6 or perforin−/− B6 mice and the size of the tumor was monitored every two days. Tumor diameters (mean ±SEM) were presented here. Five mice were in each group. * P<0.05, determined by Mann-Whitney Test. Comparison was performed between the B16-IL-33: WT and B16-IL-33: IFNγ−/− groups. The difference between the B16-IL-33: WT and B16-IL-33: perforin−/− groups was significance from days 13 to 19.