Fig. 6: IFN-I enhances nasal colonization and drives the induction of neutrophil and macrophage apoptosis.

WT and IFNAR^−/− mice were colonized with streptomycin resistant Newman (2 × 10⁸ CFU/nose). At 24 h post-colonization, the NT was excised and digested for flow cytometry. Cells isolated from the nasal tissue were sequentially stained with Apotracker, Zombie NIR and extracellular markers to identify neutrophils (CD11b⁺LY6G^high) and macrophages (CD11b⁺LY6G^low-midF4/80⁺) via flow cytometry. Apotracker/Zombie NIR double positive cells are deemed apoptotic cells. Results are shown as Zombie NIR vs apotracker gated on neutrophils (A and B) and macrophages (C and D) with a representative plots and pooled absolute counts of apoptotic cells. On day 7, WT and IFNAR^−/− mice were culled to excise and homogenize the nasal tissue (E) for CFU enumeration. Data is expressed as mean ± SD and statistically assessed using a two-way ANOVA with a Šidák multiple comparisons post-test to compare absolute counts of late apoptotic cells or using an unpaired T test for CFU enumeration (P value * <0.05, ** <0.01 and *** <0.001).