LAB^−/− resting NK cells are hyperresponsive to NK1.1 stimulation, whereas LAB/LAT^−/− NK cells are hyporesponsive. (A) Freshly purified DX5⁺ cells were isolated from spleens of the indicated strains. The cells were stimulated with rat IgG, anti-NK1.1, or PMA and ionomycin and assayed for intracellular IFNγ as in Figure 6. The data presented are representative of 3 independent experiments.