FIG. 3.

Effect of IFN-γ on the course of EC infection with S. aureus. (A) Monolayers of 2 × 10⁵ ECs per well were cultured for 72 h in culture medium alone (open bars) or supplemented with 500 U/ml IFN-γ (closed bars), washed, exposed to about 3 × 10⁷ S. aureus organisms for the indicated time intervals, washed, and treated with lysostaphin followed by immediate determination of the percentage of infected cells. (B) EC monolayers were also cultured for 72 h in culture medium alone (open circles) or with 500 U/ml IFN-γ (closed circles), washed, infected for 1 h with approximately 10⁸ S. aureus organisms, washed, and treated with lysostaphin. The percentage of infected cells was determined at the indicated time points during the 1-h infection period. (C) Some of the infected EC cultures described for panel B were additionally cultured for up to 72 h in plain culture medium (i.e., in the absence of IFN-γ). The percentages of infected cells were determined at the indicated time points during this postinfection culture period. All values represent means ± standard deviations for three (B and C) or four (A) experiments with ECs from different donors. A paired t test was used to evaluate the data. * indicates a P value of <0.04, # indicates a P value of 0.01, and ## indicates a P value of <0.001 relative to ECs cultured in medium alone. ** indicates a P value of <0.05 and *** indicates a P value of <0.001 compared to the respective culture at the start of culture of the infected monolayer.