Figure 5. H1N1-infected Mmp-9^–/– mice had lower early-phase BAL PMN and macrophage counts but higher late-phase BAL lymphocyte counts than H1N1-infected WT mice.

WT and Mmp-9^–/– mice (8–12 mice/group) were infected with an LD₂₀ inoculum of H1N1 by the intranasal route, or not infected as a control [UC, 9 mice]). At postinfection intervals, all leukocytes (A), PMNs (B), macrophages (C), and lymphocytes (D) were counted in bronchoalveolar lavage (BAL) samples. The box-and-whisker plots show the medians and the 25th and 75th percentiles, and the whiskers show the 10th and 90th percentiles. Data were analyzed with 1-way ANOVAs followed by pair-wise testing with Mann-Whitney U tests. *P < 0.05 versus the group indicated.