Figure 4.

Training of lung epithelial A549 cells triggers an enhanced production of IL-6 (A, C) and IL-8 (B, D) upon a stimulation by S. aureus. Human lung epithelial A549 cells (20,000 cells/well) were seeded in wells of flat-bottom 24-well plates. Afterwards, the cells were either pre-treated with β-glucan or MDP, or cultivated in the growth medium for 24 h, followed by a 5-day incubation prior to infection with S. aureus for 100 minutes, and then incubated for an additional 24 h as described in Material and Methods. Supernatants were collected (i) from control cells at the end of experiment (black bar graph), (ii) from cells exposed solely to inducers followed by a 5-day resting time and then incubated for an additional 24 h (grey bar graph), (iii) from cells incubated in the cultivation medium for 24 h, followed by a 5-day resting time before an exposure to S. aureus (yellow bar graph) and (iv) from inducer pretreated-cells that were infected with S. aureus after a 5-day resting time (red bar graph). The production of IL-6 and IL-8 was measured by ELISA. The vertical red dashed lines differentiate bar graphs corresponding to MOI’s 60:1 and 100:1. Data are presented as mean +/- SD. Each experiment was done in triplicate. The differences among the groups corresponding to different treatments were assessed by analysis of variance (ANOVA) followed by a Tukey’s Honestly Significant Difference test. (*) P-values ≤ 0.05 were considered to be significant.