At the end of the experiments, BAL was performed to enumerate the absolute number of PMNs in the intra-alveolar inflammatory exudates as described previously (27 (link)). In brief, lungs were lavaged by an intratracheal injection of 1 ml PBS followed by gentle aspiration. The procedure was repeated three times. After the collected BAL fluid was centrifuged, cell pellets were suspended in PBS. Cell suspension (300 μl) was cytocentrifuged on to a glass slide at 300 rpm for 5 min with a cytocentrifuge (Shandon). Slides were stained with Diff-Quick dye (Dade Behring) and examined at magnifications of 20× and 40× by light microscopy. The percentage of PMNs was calculated after counting 300 cells in randomly selected fields.