Figure 1. Dendritic cells are required for the priming of NK cells.

(A-D) CD11c DTR tg mice or RAG1^-/- CD11c DTR tg were injected with diphtheria toxin (DT) to ablate all CD11c^high DC (open symbols). Control mice received PBS injections (solid symbols). One day after DT injection, mice were injected i.p. with the indicated TLR ligands or an agonistic anti-CD40 antibody or with control injections of PBS or control Ig (not shown). NK cell effector functions were determined 18h after stimulation. IFN-γ production by highly purified splenic NK cells in response to immobilized anti-NKR-P1C/NK1.1, anti-Ly49D and anti-NKG2D antibodies (A). Cytotoxicity (B) and IFN-γ production (C) of NK cells against RMA-S/H60 targets. Similar results were obtained with RMA-S and YAC-1 targets (data not shown). The percentage of NK1.1⁺CD3⁻ cells in the lymphocyte populations was determined prior to the cytotoxicity assay and lymphocyte numbers were adjusted to contain the same number of NK cells. Thus, an NK cell:target ratio of 6:1 is equivalent to a 100-200:1 splenocyte:target ratio. Granzyme B (D) expression by NK cells. IFN-γ production and granzyme B expression were determined by intracellular cytokine staining and electronic gating on NK cells. Error bars display s.d. (n=3) and results are representative of at least three separate experiments.

(E) Groups of CD11c DTR tg mice were injected with DT (open squares). Control mice received PBS injections (solid squares). Some mice received two injections of anti-asialo GM1 antiserum to deplete all NK cells (open circles) and control mice received equal amounts of normal rabbit serum (NRS). One day later, mice were injected with TLR3 ligand or PBS. Antibody-dependent cytotoxicity (ADCC) of NK cells was evaluated against RMA cells pre-incubated with anti-Thy1.2 or control antibodies 18h after TLR stimulation.