Human airway epithelial cells express the BPI gene and produce the BPI protein. (A) This panel shows that A549 human lung epithelial cells and human SAECs constitutively express the BPI gene. Buffy coat from whole blood stimulated with lipopolysaccharide served as a positive control. Total RNA was isolated, and BPI mRNA was examined by RT-PCR. 18S ribosomal RNA was used as a loading control. (B) This panel shows that by flow cytometric analysis, A549 cells, SAECs, and neutrophils all stained positively for BPI protein. Permeabilized cells were stained with monoclonal antibody to BPI, murine IgG control, and/or murine anti-human anticytokeratin monoclonal antibody, followed by FITC-conjugated goat antimouse antibody. Fluorescence intensity was well above background staining with control IgG.