Role of TNFα and IFNγ in the induction of DC maturation by NK cells. (A) DCs were cultured for 2 days in the presence of different stimuli and then analyzed for expression of CD83. ▪ indicates iDCs that were cultured alone or cocultured with an allogeneic polyclonal NK-cell line either in the absence or in the presence of the indicated Abs. □ indicates iDCs that were cultured in the presence of supernatant derived from NK cells stimulated by plastic-bound anti-NKp30 mAb (NK SUP). Where indicated, supernatants were incubated for 30 minutes at 4°C with anti-TNFα, anti-IFNγ, or a mixture of both antibodies before culture with iDCs. Results are representative of 6 independent experiments. (B) A series of NK clones were stimulated with plastic-bound anti-NKp30 mAb (IgM isotype) overnight. Supernatants were then harvested and analyzed for TNFα (▪) and IFNγ (▦) content by specific ELISA. The same supernatants were also tested for their capability to induce DC maturation in a 2-day culture with immature DCs. ▵ indicates the percent of CD83⁺ DCs after the culture with each NK clone–derived supernatant.