FIG. 8.

Induction of TNF-α by various S. enterica serovar Typhimurium mutants in RAW264.7 cells (A) and IL-8 production in nonpolarized T84 cells (B). Macrophages were stimulated with the heat-killed bacteria at an MOI of 0.1:1 and incubated for 8 h. T84 cells were infected with live bacteria at an MOI of 10:1 and incubated for 1 h. After incubation, the cells were washed and incubated in gentamicin (100 μg/ml)-containing medium for 1 h, after which the cells were washed and incubated in an antibiotic-free medium for 12 h. TNF-α and IL-8 levels were determined by an ELISA. Three independent experiments were performed in duplicate, and an asterisk indicates a value that is statistically significantly different from the value for WT S. enterica serovar Typhimurium (P ≤ 0.05, as determined by Student's t test). The arithmetic means ± standard deviations are shown. The difference between the values for the lpp DKO- and lpp-msbB TKO-infected macrophages was also statistically significant.