<p>(A) MMP2/9 activity in lungs of uninfected control mice (<i>left panel</i>) or those 6 days after infection (<i>right panel</i>). Gelatinase activity was measured by <i>in situ</i> zymogram and visualized by green fluorescence after enzymatic cleavage to release fluorochrome from a quencher (scalebar = 50 µm). Images are representative of multiple mice. (B) MMP9 secretion by cells from BAL and lung from Ly5.1 recipient mice that received BM from either <i>Mmp9</i><sup>−/−</sup> (<i>clear bars</i>) or C57BL/6 (<i>grey bars</i>) donors was measured by ELISPOT. Mean ± SEM (n = 5–7, representative of two independent experiments). (C) Ly6G+ lung neutrophils (<i>red</i>) and MMP9+ cells (<i>green</i>), and their colocalization (<i>merge, right panel</i>) were visualized by immunofluorescence of infected lung 6 days after infection (scalebar = 50 µm). Images are representative of multiple mice.</p
