(A-J) Mice were inoculated with B16F10 cells on day 0. (A-D) On day 6, 9, and 12 mice were treated with cGAMP (A-B 10 μg, C-D 0.1 μg) encapsulated in Ace-DEX microparticles (MPs) by i.t. administration. On day 15, mice were sacrificed and tumors were processed and stained for the presence of tumor infiltrating leukocytes by flow cytometry (n=9–10 mice, mean ± SEM over 2 experiments). (E-J) On day 5, mice received their first i.p. injection of 400 μg of either an isotype control, or an αCD4, αCD8, or αNK1.1 depletion antibody. Mice continued to receive this dose twice a week for the reminder of the study. On day 6, 9, and 12 mice were treated with either PBS or 10 μg cGAMP encapsulated in Ace-DEX MPs. Tumor volume was monitored every 3 days for 30 days. The isotype control groups are repeated in panels E-G. (n=10 mice, mean ± SEM over 2 experiments). A-D. One-way ANOVA, E-G. Two-way ANOVA, *p < 0.05, **p < 0.01, ****p < 0.0001, #p< 0.05, ##p < 0.01, ###p<0.001, †p< 0.05