Figure 2.

(A) Fluorescence micrographs of THP-1 cells at 7 days post-infection with the Mtb wild-type and NDMs. Macrophage monolayers were stained with both Annexin V-FITC and propidium iodide to visualize the early and late stage of apoptosis and/or necrosis of THP-1 cells, respectively. The early apoptotic THP-1 cells with intact membranes are seen in green; Late apoptotic cells that have already lost their membrane integrity are seen in orange (or orange to red) with green membrane fragments; Totally destroyed necrotic cells are seen in red. (B) The percentage of necrosis quantified in 2 hundred cells that was infected with either the Mtb wild-type or NDM transposon mutants. Results represent means ± standard error of the mean of 3 independent experiments. **, p < 0.01 and *, p < 0.05, the significance of differences between Mtb NDMs and the wild-type.