Perforin-mediated killing is critical for the elimination of allogeneic DCs by host NK cells in vivo. (A) B6 WT, B6 pfp^−/− or (B) IL-12Rβ2^−/− mice, all CD8-depleted, were injected, or not, with anti-NK1.1 PK136 mAb and then immunized with equal numbers of CFSE^low-B6 DCs and CFSE^high-BALB/c DCs. (A) Data are mean plus or minus SEM of 3 mice per group and are from one representative experiment of 4 performed. (B) Data are mean plus or minus SEM of 4 mice per group. (C) B6 CD8^−/− and (D) CD8^−/−pfp^−/− mice were injected with equal numbers of CFSE-labeled BALB/c DCs (green) and CMTMR-labeled B6 DCs (red). Forty-eight hours after immunization, draining lymph nodes were harvested and prepared for confocal microscopy analysis. Lymph node sections were stained anti-B220 and anti-PNAd mAbs (blue). Data are the percentage of CFSE BALB/c DCs among control CMTMR B6 DCs. Data were pooled from 2 independent experiments. Data are mean plus or minus SEM of individual lymph nodes (4 or 5 mice per group). **P < .01. N.S. indicates not significant.