(D) Optical section, where SCs infected by S. learn more pneumoniae for 3 h were immunolabeled for cMR (red). Bacteria were stained with DAPI (blue). Orthogonal z-sections in the horizontal and vertical planes reveal

S. pneumoniae adhered (arrow) or internalized (arrowheads) by SCs (D). The nuclei were counterstained with DAPI. These results are representative of five separate experiments. Scale bar = 18 μm in (A); 18 μm in (B – C); 12 μm in (D). To monitor the course of infection, the number of SCs containing adhered and/or internalized S. pneumoniae was quantified at different times up to 24 h. Immediately selleck kinase inhibitor after the interaction step, as well as 3 h later, the percentage of association was 56.5%, and decreased to 47.2% and 40.8% after 12 and 24 h, respectively (Figure 2). Figure 2 Kinetics of association (adhesion or internalization) of Streptococcus pneumoniae with Schwann cells (SCs). The percentage of SCs containing adhered or internalized S. pneumoniae was quantified at different times up to 24 h. The graph shows a progressive decrease in the number of S. pneumoniae associated with the SCs. These data are representative of three separate experiments, each of which was conducted in triplicate. ***P selleckchem <0.0001. For statistical analysis, we used Two-way ANOVA and Tukey’s Multiple Comparison Test. We evaluated the endocytosis of S. pneumoniae by SCs, maintained either in

medium alone or in medium containing an excess of mannan, according to a protocol previously described by us for the endocytosis of S. pneumoniae by OECs [3]. Observations were made after interaction of

S. pneumoniae with SCs for 3, 12, and 24 h in both conditions. Inositol monophosphatase 1 Variable numbers of internalized bacteria as detected by labeling with anti-pneumococcal antiserum and counterstained with DAPI were seen throughout the cytoplasm of SCs maintained in medium alone (Figure 3, detailed in Figure 4A-E). On the other hand, the interaction assays performed in the presence of mannan impaired the bacterial binding to the cellular surfaces, thus drastically reducing the number of infected cells after 3 h of association (Figure 3). However, the number of infected cells was not significantly affected from 3 to 24 h of infection in the mannan-treated cultures (Figure 3). Figure 3 Competition assays showing the participation of mannose receptor (MR) during the association of Streptococcus pneumoniae with Schwann cells (SCs). The assays were performed by adding increasing doses of mannan (10 to 1000 μg/ml) in the interaction medium, and the results were highly statistically significant (***P <0.0001) at a dose equal to or higher than 100 μg/ml. The graph shows an inhibition of the percentage of SCs with associated bacteria immediately after 3 h of association (black bar versus white bar). However, this percentage was not significantly affected after this time up to 24 h of infection in mannan-treated cultures (black bar versus dark-gray bar).