FIG. 4.

Control of influenza A virus infection is STAT1 and STAT2 dependent but IFN-α/β independent. (A) Cohorts of 6- to 8-week-old 129Sv mice of the indicated genotypes were infected i.n. with 100 PFU of influenza virus A/HK-X31. Titers (expressed as fluorescent focus units per gram of lung tissue) were determined by fluorescent focus assay of lung homogenates collected on day 3 after infection. (B) Susceptibility of 129SvEv wild-type, IFNAR^−/−, STAT1^−/−, and STAT2^−/− mice to influenza virus was compared following infection with 100 PFU. Five or six 6- to 8-week-old mice of each strain were used. The percent survival for each group is shown.