L. pneumophila infection activates IL-8 promoter in Jurkat cells. (A) Jurkat cells transfected with -1481-luc were infected with L. pneumophila Corby at the indicated MOI values for 6 h. The luciferase activities were expressed relative to cells transfected with -1481-luc followed by mock-infection. *, P < 0.01, as determined by the Student t test. (B) Reporter assay using plasmid DNA containing serial deletions in 5'-flanking region of the IL-8 gene. (Left) Schematic representation of the IL-8 reporter constructs, demonstrating locations of several known binding sites for transcription factors. (Right) The indicated luciferase reporter constructs were transfected into Jurkat cells, and the cells were subsequently infected with Corby strain (MOI of 100) for 6 h. The activities are expressed relative to that of cells transfected with -50-luc followed by mock-infection, which was defined as 1. The numbers on the bars depict fold induction relative to the basal level measured in uninfected cells. (C) Relative importance of AP-1, NF-IL-6, and NF-κB binding sites in IL-8 promoter. Wild-type and mutated plasmids were transfected into Jurkat cells. The transfected cells were infected without or with Corby. The activities are expressed relative to that of cells transfected with -133-luc followed by mock-infection, which was defined as 1. Luciferase activities were normalized based on the Renilla luciferase activity from phRL-TK. The numbers on the bars depict fold induction relative to the basal level measured in uninfected cells. LUC, luciferase. Graph data are mean ± SD values of three experiments.