The helper effect of IL-18–conditioned NK cells is dependent on IL-2 and IL-12. MLR were carried out with DC, cytokine-conditioned NK cells and allogeneic naive CD4⁺ T cells in the presence of a neutralizing Ab against IL-2 (A), IL-12 (B), or a combination of both (C). IFN-γ was measured in MLR supernatants by ELISA after 5 days. Data are from 1 representative experiment of 3. ***P < .001.