FIG. 4.

Cytokine production and NF-κB and MAPK activation in response to P. aeruginosa or E. coli in wild-type (WT) and RICK-deficient (RICK knockout [KO]) macrophages prestimulated with heat-killed E. coli. (A to D) Macrophages were left untreated (−) or stimulated with heat-killed E. coli (HKEC) for 24 h and then infected with P. aeruginosa strain PAK (A and B) or E. coli (C and D) at various macrophage/bacterium ratios for 24 h. Cell-free supernatants were analyzed for the production of IL-1β and IL-6 by ELISAs. Values that were significantly different from the control value (no pretreatment) are indicated as follows: *, P < 0.05; **, P < 0.01. The results of this experiment are representative of those of three independent experiments. (E) Whole-cell extracts were immunoblotted with the indicated antibodies (p p38, phosphorylated p38), and (F) the band density was determined by dividing the density of phosphorylated forms by unphosphorylated forms.