NK-subset activation in B6 mice infected with Listeria monocytogenes. At the indicated time points, splenocytes from Listeria-infected B6 mice were harvested and immediately stained with mAbs. The results are depicted as the percentage ± SEM of cells in each subset (gated also for NK1.1⁺CD3^- phenotype) with intracellular IFN-γ (n = 3 mice). A repetition of the experiment yielded similar results.