Higher ROS levels required by macrophages for killing intracellular leptospires.

<p><b>(A)</b> Total ROS levels in <i>L</i>. <i>interrogans</i>-infected macrophages and neutrophils, determined by confocal microscopy for the indicated infection times. The green fluorescence indicates the intracellular total ROS levels. <b>(B)</b> Statistical summary of green fluorescence intensity reflecting the total ROS levels in <i>L</i>. <i>interrogans</i>-infected macrophages and neutrophils. Statistical data from experiments such as shown in A. Bars show the means ± SD of three independent experiments. Two hundred cells in each experiment were analyzed to quantify the values of fluorescence intensity. The means of fluorescence intensities from the cells without infection were set as 1.0. *: <i>p</i><0.05 <i>vs</i> the total ROS level in the macrophages and neutrophils without infection. ^#: <i>p</i><0.05 <i>vs</i> the total ROS levels in the <i>L</i>. <i>interrogans</i>-infected neutrophils. <b>(C)</b> Lower dead leptospiral percentages in NAC-pretreated <i>L</i>. <i>interrogans</i>-infected Hu-macrophages rather than Hu-neutrophils, determined by spectrofluorimetry for the indicated infection times. Bars show the means ± SD of three independent experiments. 10⁷ leptospires in each experiment were used to determine the dead leptospiral percentages. *: <i>p</i><0.05 <i>vs</i> the dead leptospiral percentages from the NAC-untreated <i>L</i>. <i>interrogans</i>-infected Hu-macrophages. <b>(D)</b> Lower dead leptospiral percentages in NAC-pretreated <i>L</i>. <i>interrogans</i>-infected Ms-macrophages rather than Ms-neutrophils, determined by spectrofluorimetry for the indicated infection times. The legend is the same as in C except that this experiment was for detection of Ms-macrophages and Ms-neutrophils.