Figure 5.

GM-CSF promotes tumor control through its activities on eosinophils. (A–E) Eo-Cre × Csf2rb^fl/fl mice and their Cre-negative littermates were subcutaneously injected with 5 × 10⁵ MC38 cells and analyzed after 15 d with respect to their tumor weights and volumes (A) as well as their intratumoral frequencies of IFN-γ⁺ and TNF-α⁺ CD4⁺ T cells (B), IFN-γ⁺ and TNF-α⁺ CD8⁺ T cells (C; PMA/ionomycin), and IFN-γ⁺ CD8⁺ T cells upon stimulation with MC38-specific peptide (D; n = 13–14 tumors per genotype). Frequencies of effector memory cells are shown as well (E). Data in A–E are pooled from two independent studies. (F–H) WT C57BL/6 mice (F and G, n = 15–22 tumors per group) and Eo-Cre × Csf2rb^fl/fl mice and their Cre-negative littermates (H, n = 6–14 tumors per group) were injected with MC38 cells and treated three times weekly with recombinant GM-CSF or IL-5 as indicated. The tumor weights and volumes at the study endpoint are plotted for two (IL-5) and three (GM-CSF) independently conducted, pooled studies in F and G and a representative study of two in H. (I–M) Csf2ra^−/− mice and WT controls were injected with MC38 cells and analyzed after 15 d with respect to their tumor weights and volumes (I and J) and their intratumoral frequencies of IFN-γ⁺ and TNF-α⁺ CD4⁺ T cells and of IFN-γ⁺ and TNF-α⁺ CD8⁺ T cells (K and L; PMA/ionomycin, n = 13–17), and of IFN-γ⁺ CD8⁺ T cells upon stimulation with MC38-specific peptide (M; n = 4–10). Data in I–L are pooled from three independent studies; data in M are from one representative study of three. *, P < 0.05; **, P < 0.01; and ***, P < 0.001; n.s., not significant; as calculated by Mann–Whitney test.