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. 2013 Dec 12;9(12):e1003821. doi: 10.1371/journal.ppat.1003821

Figure 4. Cell-to-cell spread of L. monocytogenes (LM) into mouse syncytiotrophoblast (SYN) is enhanced by syncytial actin network disruption.

Figure 4

Untreated and Cyto-D treated SYN was incubated with LM-infected murine macrophages and foci of bacterial spread were quantified. Bacterial foci were included in the analysis when multiple bacteria were observed unbounded by the outline of a macrophage membrane; many such foci were surrounded by actin clouds. A. Panel i: Representative immunofluorescence image of untreated differentiated TSCs shows bacterial infection of mononuclear trophoblasts (MNT) versus SYN. SYN is outlined and marked by blue star. Panel ii: One hour of Cyto-D treatment increases the number of bacterial foci in SYN. Arrowheads indicate adherence of infected macrophages to trophoblasts; arrows indicate spread events. Actin is shown in red, nuclei in blue, LM in green. Bars = 50 um. B. Quantification of bacterial foci per unit area in untreated versus Cyto-D treated SYN at 5 hours p.i. with macrophages. Each data point represents the average of bacterial foci in ten random fields (20×) with at least 50% syncytium. Treatment with Cyto-D significantly increases infection of SYN via cell-to-cell spread (p = 0.03 by Student's T-test); treatment does not significantly change infection of MNT (p = 0.33). Bars represent median.