Plasminogen-deficiency prevents severe inflammation.

<p>(A) Histopathological analysis of lungs from infected WT and PLG-KO mice inoculated with A/PR/8/34 virus (day 3 post-infection) or A/Netherlands/602/09 virus (day 5 post-infection). Thin sections of lungs obtained from infected and uninfected WT and PLG-KO mice (as indicated) were stained with hematoxilin end eosin (HE) to evaluate histopathological changes. Note the marked infiltration of inflammatory cells in the lungs of infected WT mice, which was largely absent in the lungs of PLG-KO mice. The results shown are representative for two-three mice for both groups. Immunohistochemistry (IHC) using a monoclonal antibody for the influenza A virus nucleoprotein was used to detect virus-infected cells. Cells positive for the presence of viral antigen stained red. (B) Cytokine levels in BAL were assessed by ELISA on the indicated days post inoculation of WT (black bars) and PLG-KO mice (white bars) with IAV A/PR/8/34 or A/Netherlands/602/09. Data represent mean ± s.e.m. of 3–6 mice per group.