Neutralization of LPS in vitro by BPI-containing A549 cell supernatant and lung lavage fluid. LPS was preincubated with supernatant derived from AdhBPI- or AdDl70.3-infected A549 cells (A-B) or lung lavage fluids from AdhBPI- or AdDl70.3-infected C57BL/6 mice (C) and was then added to alveolar macrophage culture. In some experiments, A549 cell supernatant or lung lavage fluid was treated with goat anti-BPI or control serum before incubation with LPS and macrophages (D). Concentration of TNF-α (A,C-D) and MIP-2 (B) in supernatant was determined using ELISA. Results are expressed as means ± SEM from triplicate wells, representative of 2 independent experiments. The difference between AdhBPI and AdDl70.3 is statistically significant (P ≤ .012, P ≤ .000 004, and P ≤ .000 007 for .0025, 0.25, and 25 μL, respectively, for TNF-α in panel A; and P ≤ .02, P ≤ .0001, and P ≤ .000 003 for .0025, 0.25, and 25 μL, respectively, for MIP-2 in panel B; P ≤ .000 0006 for 25 μL in panel C).