Figure 4
Requirement for ICOS-expressing cell populations to generate survival benefit with RT. (a) (i) Experimental design. 2 × 105 CT26 cells were implanted subcutaneously into the flanks of Balb/c mice on day 0. On day 14 all mice in radiation groups were treated with 12 Gy radiation to the tumor using CT guidance. Mice were injected i.p. with 0.25 mg/kg ICOS antibody or in control groups, mice were treated with equivalent dose of isotype control antibody on days 14 and day 21. For depletion groups mice were treated with 250 µg of anti-CD8β, 200 µg anti-CD4(GK1.5), or 100 µl anti-Asialo GM1 (NK depletion) one day prior to radiation and weekly thereafter for duration of animal survival (Blue box indicates duration of depletion). Mice were followed for survival and blood was analyzed weekly by FACS analysis. (ii) Overall survival curves for mice treated as in (i). (b) Representative flow plots. (c) Flow plots for ICOS expression on relevant cell subsets in ICOS antibody treated or isotype treated groups. ****p < 0.0001, ***p < 0.001, **p < 0.01, *p < 0.05 as determined by Log-rank test. N = 10 mice per group and experiments were repeated at least 2x. For the OS shown in (ii) two experiments were combined for analysis.
