Effect of CpG-ODN on CD8 and NK cells. Mice bearing four day-old intracranial GL261 tumors were treated with intratumoral CpG-ODN (3μg/injection), control ODN (3μg/injection), and PBS once (one inj.) or four (four inj.) times as described in Fig. 1. Twenty-four hr after the last injection, brain, spleen, and blood were harvested and analyzed by flow cytometry for the percentage of CD8 (top panel) and NK (bottom panel) cells. P values for significant differences between treatment groups are provided above each bar graph. Significant differences between one and four injections for each treatment is represented as *: p<0.05, **: p<0.001, ***: p<0.0001. n=4 mice for each treatment group. Data is representative of two separate experiments.