Figure 2
The capacity of different Salmonella strains to downregulate MHC expression on the surface of porcine macrophages, the Salmonella invasion capacity in macrophages, and the effect of different Salmonella strains on macrophage viability and reactive oxygen species (ROS) production. A. The average mean PAMinf/PAMuninf ratios (± standard deviation) measured in the FL-5 channel, 0 h (grey bars) and 24 h (black bars) post inoculation (pi) with different Salmonella strains or an Escherichia coli strain. The values were calculated from the ratios obtained from 3 independent experiments and an asterisk refers to a significantly different average mean fluorescence ratio (p ≤ 0.05). Salmonella Typhimurium strains are indicated with ♦. PAMinf and PAMuninf: infected and uninfected porcine alveolar macrophages, respectively. B. The invasion capacity in porcine macrophages of different Salmonella strains. Salmonella Typhimurium strains are indicated with ♦. Salmonella invasiveness was expressed as the percentage relative to the invasion capacity of strain 112910a ± standard deviations. Each bar represents the average of three independent experiments. An asterisk (*) indicates a statistically significant difference in invasion capacity (p ≤ 0.05). C. Macrophage viability is expressed as the average percentage of viable cells at 24 h post inoculation ± standard deviation relative to viable uninfected macrophages (negative control). Each bar represents the average of three independent experiments conducted in triplicate. Salmonella Typhimurium strains are indicated with ♦. An asterisk (*) indicates a statistically significant difference in macrophage viability (p ≤ 0.05). D. ROS production of macrophages inoculated with different Salmonella strains. The ROS production of infected macrophages was expressed relative to the ROS production of phorbol 12-myristate 13-acetate (PMA) treated macrophages (positive control). Each bar represents the average of two independent experiments conducted in triplicate. Salmonella Typhimurium strains are indicated with ♦