To address whether the neutrophil recruitment observed during infection with the ExoU-producing strain is due to NF-κB activation and the consequent IL-8 induction, we investigated the effect of ExoU in P. aeruginosa-infected human epithelial respiratory and microvascular endothelial cell cultures, as well as in a murine model of pneumonia. This evidence concerns the gene NFKB1 and pneumonia.