FIG. 3.

S. Typhimurium has enhanced replication in cells stimulated with TLR ligands. (A) RAW 264.7 cells were treated with PBS, LPS, poly(I:C), PG, or CpG-ODN for 20 h before infection with wild-type S. Typhimurium. The increase in intracellular bacteria between 2 to 18 h postinfection is shown as the mean with standard errors from three technical replicates from 4 to 10 experiments normalized to the PBS control. The absolute replication value (ARV) for the PBS control is given above the control bar, and the number of experiments used to produce the data is given above each treatment group. Asterisks represent significant differences from the PBS control (P < 0.05; one-way analysis of variance). (B) Intracellular replication of S. Typhimurium (ST) in J774 cells pretreated with CpG DNA prior to infection. Data are the means with standard errors. (C) The enhanced replication of S. Typhimurium in TLR ligand-treated cells is blocked by IFN-γ. RAW 264.7 cells were treated with IFN-γ in addition to PBS, LPS, poly(I:C), PG, or CpG-ODN or with PBS alone for 20 h before infection. Intracellular bacterial replication for the treatment groups was normalized to the PBS control and is shown as the mean with standard errors from three technical replicates from three to six experiments. The absolute replication value (ARV) for the PBS control is given above the control bar, and the number of experiments used to produce the data is given above each treatment group. Asterisks represent significant differences (P < 0.05, one-way analysis of variance) compared to the PBS control not treated with IFN-γ.