IFN-I signaling on hematopoietic cell lineage helps protect mice from lethal influenza infection.

Bone marrow (BM) cells from naïve WT (W) or Ifnar1^−/− (K) mice were grafted to lethally irradiated WT or Ifnar1^−/− recipient mice. (A–C) Sets of BM grafted mice were challenged with influenza PR8 virus (1×10⁵ pfu) and analyzed at 3 dpi. (A) Number of monocytes (Mo) and neutrophils (N) were determined. (B) Expression levels of MCP-1 and KC were measured in BALF. (C) Monocytes in the lung were pooled and cultured for 4 h to measure chemokine production in vitro. Values are mean + SD of triplicate experiments with n>4 for each group. (D) Mice were challenged with lethal dose of influenza PR8 (1×10⁵ pfu) and survival was monitored for 2 weeks. W→W (n = 17), K→W (n = 16), W→K (n = 16), and K→K (n = 11). Data were pooled from three independent experiments.