L. pneumophila infection activates IL-8 promoter in epithelial cells. (A) Schematic representation of the IL-8 reporter constructs, demonstrating locations of several known binding sites for transcription factors. (B) L. pneumophila infection increases IL-8 promoter activity in a dose-dependent fashion. The -1481-luciferase construct (40 ng) containing IL-8 promoter spanning -1,481 to +44 bp was transfected into A549 cells, and the cells were subsequently infected with varying concentrations of L. pneumophila AA100jm for 48 h before luciferase assay. Luciferase activity is presented as a fold induction relative to the basal level measured in uninfected cells. (C) 5' deletion analysis of the IL-8 promoter. The indicated luciferase reporter constructs (40 ng) derived from the IL-8 promoter were transfected into A549 cells, and the cells were subsequently infected with AA100jm strain (MOI of 100) for 48 h. The activities are expressed relative to that of cells transfected with -50-luc without further treatment, which was defined as 1. Data are mean ± SD values of three independent experiments. *, P < 0.05; **, P < 0.01 (compared to uninfected cells).