Figure 4.

Lack of DNAM-1 impairs NK cell and CD8 T cell cytotoxicity. (A) Differential expression of DNAM-1 ligands on B16F10 and YAC cells. B16F10 and YAC-1 cells were analyzed for the expression of CD155 and CD112 by flow cytometry. Open histograms represent staining with the respective antibody, whereas shaded histograms show isotype staining. These data represent three independent experiments. (B and C) Lack of DNAM-1 affects NK cell–mediated death of tumor cells lacking NKG2D ligands. IL-2–activated purified NK cells were tested for cytotoxic activity against (B) YAC and (C) B16F10 targets in a standard 4-h ⁵¹Cr release assay. Each data point is the mean ± SEM of two independent experiments done in triplicate for each effector/target ratio. (D) Reduced killing of B16 cells pulsed with OVA peptide by DNAM-1^−/− CD8 T cells. Splenocytes from OT-1 transgenic mice were stimulated with OVA peptide 257–264 and cultured in vitro for 15 d in the presence of 20 U/ml IL-2. Antigen-specific cytotoxicity was assessed using B16 cells, either pulsed or not pulsed with 100 pg/ml OVA peptide 257–264. Naive WT OT-1 CD8⁺ T cells did not kill peptide-pulsed target cells. The data represent two independent experiments.