Normal ITAM-independent IFNγ production by CD45-deficient NK cells. (A) Mixed bone marrow chimeric mice (1:1 mixture of WT and CD45-deficient bone marrow) were infected with 5 × 10⁴ PFU of MCMV. Intracellular staining of NK cells for IFNγ at day 1.5 after infection (solid line) compared with NK cells from uninfected control mice (gray fill). WT splenocytes (left panel) gated on CD45⁺NK1.1⁺CD3⁻ and CD45-deficient splenocytes (right panel) gated on CD45⁻NK1.1⁺CD3⁻. Three independent sets of mixed bone marrow chimeras were made with approximately 10 mice per set. Similar results were seen in all groups of chimeric mice. (B) Enriched WT or CD45-deficient NK cells were incubated with IL-12 (20 ng/mL), IL-18 (10 ng/mL), and brefeldin A, followed by intracellular staining for IFNγ. A representative dataset is shown on top, and the average ± SEM of results from 5 independent experiments is shown below. NS indicates no significant differences between genotypes found using a 2-tailed unpaired t test.