Supplementary Figures 1 through 8 from Basophils Promote Tumor Rejection via Chemotaxis and Infiltration of CD8+ T Cells

Supplementary Figure 1 shows that DT application in Foxp3DTR and Foxp3.LuciDTR4 mice resulted in different degree of Treg depletion not only in tumor but also in blood, spleen and lymph nodes. Supplementary Figure 2 demonstrates Treg depletion in Foxp3DTR mice, but not Treg depletion in Foxp3.LuciDTR4 mice, induced complete rejection of established B16 tumors, similarly to what we observed with HCmel12 tumors. Supplementary Figure 3 shows that Adoptive cell reconstitution of Treg-depleted Foxp3DTR mice with increasing numbers of purified CD4+ CD25+ Tregs isolated from wild-type mice impaired rejection of HCmel12 tumors, indicating that relatively small number of Treg were able prevent immune-mediated tumor rejection. Supplementary Figure 4 demonstrates that Basophil depletion impaired infiltration of T cells into Treg-depleted B16 tumors and rejection of B16 tumors observed after Treg depletion in Foxp3DTR mice, which confirms our findings in HCmel12 setting. Supplementary Figure 5 shows that FcεRI was expressed only by basophils in HCmel12 tumors after Treg depletion in Foxp3DTR mice, showing that tumoral basophils can be selectively targeted by MAR-1 antibody, and basophil depletion resulted in reduced intratumoral expression of CCL3 and CCL4, indicating that basophils are the major source of intratumoral CCL3 and CCL4. Supplementary Figure 6 shows that Eosinophil depletion had no impact on rejection of HCmel12 tumors observed after Treg depletion in Foxp3DTR mice. Supplementary Figure 7 demonstrates that IL-3/anti-IL-3 antibody complex injection induced basophilia in not only in tumor but also in other organs in B16-OVA-bearing mice and this was associated with increased specific chemokines (CCL3 and CCL4) and cytokines (IL-4 and IL-13) in the tumor microenvironment. Supplementary Figure 8 shows that combination of adoptive transfer of tumor-specific CD8+ T cells with IL-3/anti-IL-3 antibody complex induces strong leukocyte subpopulation infiltration into B16-OVA tumors, in addition to OT-I CD8 T cells.