Levels of effector gene expression determined by RT-PCR in Salmonella SL1344. (A) Representative PCR results for effector mRNA expression. Mdh was used as the internal control. Control: Salmonella without treatment; TNF-α: Salmonella treated with TNF-α. (B) and (C) The relative intensity of PCR bands (Control vs. TNF-α-pretreated Salmonella). There were 3 repeated experiments performed in all controls and TNF-α treated groups. First, the densitometry value of each indicated effector gene was divided by the value for the Mdh band. Next, the obtained values were compared with the corresponding control values. The relative fold changes are shown in Figure 1B and 1C with the control group value set as "1" and compared to the TNF-α treated groups. Data are reported as the mean ± SD of three independent experiments. *P < 0.05 was considered significant.