IκBζ and IFN-γ expression in human NK cells. IκBζ and IFN-γ expression was evaluated in CD56⁺ selected human NK cells over time in response to recombinant IL-12 and IL-18 (10 ng/mL each). (A) Time course of IκBζ, IFN-γ, and IL-8 protein expression for IL-12 and IL-18 stimuli in human NK cells (2 × 10⁶ cells/mL) as assessed by immunoblot of cell lysates for IκBζ and ELISA of supernatants for IFN-γ and IL-8. (B) Time course of IκBζ, IFN-γ, and IL-8 mRNA expression in human NK cell by quantitative PCR. Immunoblot is representative of 3 independent experiments and bar graphs represent the mean ± SEM for 3 experiments. Values in the undetectable range have been assigned a random insignificant number and plotted in the graph. Vertical lines have been inserted to indicate a repositioned gel lane. RCN indicates relative copy number.