Figure 5.

Decrease of the suppressive function of Tregs on antitumor effect through OX40 costimulation in vivo. NT2 tumor cells (5×10⁶ cells per animal) were inoculated on day −3 to FVB mice (n=20). Anti-OX40 mAb or rat IgG (300μg per animal injected i.p.) was injected on day −2 to neu-N mice (n=6 per group). On day 0, Tregs were isolated from the spleens of the injected neu-N mice using a MACS CD4⁺CD25⁺ regulatory T cell Isolation Kit. The Tregs (5×10⁵ cells/body) were adoptively transferred to the NT tumor inoculated FVB mice (n=6 per group) via their tail veins. As a control saline was injected into tail veins of FVB mice instead of adoptive transfer (n=8). 3T3 neu/GM vaccine cells (3×10⁶ total cells) were also given on day 0 to all the tumor inoculated FVB mice. Tumor size (mm²) was determined by measuring the tumor diameter along orthogonal axes. The mean tumor size is reported. “vaccine alone” indicates the tumor inoculated and vaccinated mice with saline injection. “vaccine + Tregs treated with rIgG” indicates the tumor inoculated and vaccinated mice which underwent adoptive transfer of Tregs with pretreatment of rIgG, and “vaccine + Tregs treated with OX40” indicates the tumor inoculated and vaccinated mice that underwent adoptive transfer of Tregs with pretreatment of OX40 costimulation. Statistical analysis was performed with the Students t -test.