Depletion of NK cells during priming results in reduced DC activation and CTL activity. Mice were treated as described in Figure 2, except that NK cell depletion was performed as described in “Materials and methods.” (A) Histograms of CD80 and CD86 distribution of CD11c⁺ I-A/I-E ⁺ cells isolated from Peyer patches with (right panels) or without (left panels) NK cell depletion. ^*P < .01 compared with the pBud control group; ^**P < .05 compared with the pBud control group depleted of NK cells. (B) Mice vaccinated with pH60/Surv were not depleted (▪) or were depleted of NK cells before vaccination (♦) or after vaccination (⋄). Splenocytes were stimulated in vitro with irradiated CT-26 colon carcinoma cells for 5 days and were used in a standard ⁵¹Cr-release assay against these tumor cells. ^*P < .05 compared with nondepletion or postvaccination depletion groups. (Top panels) Distribution of CD4 and CD8 T cells obtained from undepleted or NK-cell depleted mice. (C) In vitro-stimulated splenocytes isolated from vaccinated mice either not depleted (▪)or depleted (○) of CD8 cells and used in a ⁵¹Cr release assay against CT-26 target cells. ^*P < .01 compared with the nondepletion group. All experiments were repeated at least once and yielded similar results.