Type I IFN is dispensable for NK cell survival and memory formation in Rag2^−/− × Il2rg^−/− hosts. (A) NK cells from WT:Ifnar^−/− chimeric mice were cotransferred into Rag2^−/− × Il2rg^−/− hosts and infected with MCMV. Percentages of Ly49H⁺ NK cells in peripheral blood are shown for the indicated time points. (B–G) Percentages and phenotype of WT (CD45.1) and Ifnar^−/− (CD45.2) splenic NK cells are shown at days 7 (B–D) and 30 PI (E–G). Data are mean ± SEM and representative of three independent experiments with at least n = 4 biological replicates per condition.