Figure 4. The allogeneic DRibble vaccination in combination with anti-OX40 antibody mediated a potent antitumor response and required both CD4⁺ and CD8⁺ T-cell subsets for its efficacy.

(a) To evaluate whether allo-DRibbles can confer anti-tumor immunity against 4T1, we administrated allo-DRibbles from C57MG (b,c) or MMC (d) mammary carcinoma cells. BALB/c mice bearing 13-day 4T1 tumors were established as in Fig 2 and treated with DRibbles from C57MG tumors, 4T1 tumors, followed by two boosts with DC s.c. at 2 day interval. Anti-OX40 (100 μg) was injected i.p along with each immunization. C57MG allo-DRibbles resulted in 80% cure rate of BALB/c mice bearing 4T1 tumors. To determine the role of CD4⁺ or CD8⁺ T cells for the anti-tumor efficacy, 4T1 tumor cells (30,000) were injected into the right mammary pads of BALB/c mice. At day 5, mice with palpable tumors were divided into four experimental groups: untreated, DRibble vaccination and anti-OX40, DRibble vaccination and anti-OX40 with CD8 depletion, DRibble and anti-OX40 with CD4 depletion. Anti-CD8 (100 μg) and anti-CD4 (200 μg) was given twice i.p. to deplete CD8⁺ and CD4⁺ T cells respectively on day 5, 9. Mice received DRibbles (i.n., 20 μg) from MMC tumors on day 6. Anti-OX40 (100 μg) was given i.p. at day 6 and 9. Tumor growth was measured every other day on weekdays starting from day 10 (c), and mouse survival was monitored (d). Independent experiments were performed two times. *P < 0.05; **P < 0.01.