Effect of Plg/Pla treatment in an LPS-induced pleurisy model. Mice received an i.pl. injection of LPS (250 ng per cavity) or PBS. After 8 hours of challenge, mice were treated with Plg (2 µg per cavity, i.pl.) or Pla (2 µg per cavity, i.pl.). PBS (vehicle, i.pl.) was injected in both unchallenged control mice and LPS-challenged mice. Ten hours later, the pleural cells were harvested, and cytospin preparations were analyzed for the number of neutrophils per cavity (A) as well as the percentage of apoptosis (B) and efferocytosis (C). In the same experimental settings, Plg (2 µg) was incubated with the serine protease inhibitor aprotinin (17.5 µg) for 1 hour at 37°C prior to i.pl. injection (D,E). Results are expressed as the mean ± SEM of at least 4 mice in each group. **P < .01; ***P < .001 when compared with unchallenged mice; ^###P < .001 when compared with untreated mice. (F) Neutrophils isolated from peripheral blood of healthy human donors were cultured in 96-well cell culture plates (10⁶ cells per well) with or without LPS (500 ng/mL) for 1 hour, and thereafter with or without Plg/Pla (2 µg/mL) for an additional 5 hours. Then, cytospin preparations were stained with May-Grünwald-Giemsa and counted for apoptosis (F). Representative figures are shown in (G). Arrows indicate apoptotic neutrophils. Scale bars, 10 µm. Original magnification ×20. **P < .01 when comparing LPS-treated group with untreated (UT) neutrophils; ^#P < .05 when comparing LPS-treated cells alone and LPS-treated cells after incubation with Plg or Pla. In vitro experiments were performed twice with different donors in biological triplicates.