Disruption of PTEN enhances pulmonary neutrophil accumulation and reduces bacterial burden in neutropenia-related pneumonia. (A) PTEN depletion does not affect the amount of circulating neutrophils. The complete blood count (CBC) and white blood cell count of each sample were analyzed using a Hemavet 850 hematology system. (B) Histologic analysis of lungs reveals bacterial colonies and polymerized fibrin in the pulmonary parenchyma. Lungs were fixed with Bouin solution, and 6-μm sections were stained with H&E. (C) Total numbers of neutrophils in BALF were quantified as described in Figure 1A. (D) MPO activity, an indicator of tissue neutrophil accumulation, was determined using an EnzChek MPO activity assay kit (Invitrogen, Carlsbad, CA). (E) Bacterial colonies in histologic lung sections were quantified and expressed as colony numbers in each ×400 field. (F,G) Bacterial killing in inflamed lungs. Live bacteria in lung homogenates were assessed with the colony assay as described in Figure 3B,C. (H) Pulmonary edema formation was quantified as the percentage of edema in the total parenchymal region using IPlab imaging software. All data are presented as mean (± SD; n ≥ 4 mice in each group). **P < .01, ***P < .001 versus WT.