Figure 4.

Antigen-specific CD8⁺ T cells are critical for SC1-mediated tumor control, and protection from tumor rechallenge.

(a-d) BALB/c mice were engrafted with CT26 cells and treated with four doses of SC1 or vehicle (saline) every 5 d. (a) The percentage of gp70-specific CD8⁺ T cells in blood (at d 21 after tumor inoculation, three independent experiments), spleens and tumors (on d 26, 2 independent experiments) was measured by tetramer staining by flow cytometry. (b) Lymphocytes were isolated from blood at d 21 (n = 5) (left) and from tumors at d 26 (n = 3) (right) and the number of IFNγ-producing cells was measured by ELISpot. (c) BALB/c mice (n = 10) were injected s.c. with CT26 cells, then treated with anti-CD8 antibody prior to each i.v. dose of SC1 or vehicle (saline). Tumor growth over time is shown. (d) Mice were treated as described in Figure 2(b), and all SC1-treated, tumor-free mice (n = 4) were rechallenged s.c. with CT26 cells on d 77 after the first tumor injection. Control mice (n = 5). Tumor growth in mice is shown (left). The percentage of gp70-specific CD8⁺ T cells in the blood at d 90 after first CT26 tumor inoculation (d 13 after the CT26 tumor rechallenge) was measured by tetramer staining (right). Data shown as mean ± s.e.m, of the indicated numbers of mice. p*<0.05, p**<0.01, p***<0.001, using Mann–Whitney test (A, B, and D), one-way ANOVA-test (C).