In Vivo Adaptation and Persistence of Neisseria meningitidis within the Nasopharyngeal Mucosa
Figure 4
Role of polymorphonuclear cells in mucosal protection against N. meningitidis colonization.
(A) CEACAM1-humanized and wild-tpye mice were either left untreated or were PMN-depleted by anti-Gr-1 antibody clone RB6-8C5 and then left either uninfected, or were i.n. infected with 108 CFU MC58 as indicated. Immunohistological staining of nasal tissues for Gr-1 was performed on tissue samples obtained at day 1 to visualize PMN infiltrates. Overview of nasal cavity structures in low-magnification (5×) image on the top indicate regions of interest for higher-resolution (40×) images below. Gr-1 is stained brown and indicated by arrows, nuclei appear in blue. Images are representative for n = 3 animals of each genotype. (B) Same samples as in (A) were used for immunofluorescence staining. Human CEACAM appears in red, Nme in green and nuclei in blue. Note, that different regions of interest were chosen as compared to (A), but the images are in the same sequence as indicated for the groups above. (C) Cohorts of PMN depleted mice were i.n. infected with 108 CFU of Nme MC58 and viable Nme recovered at indicated time points. Pairwise comparisons of PMN-depleted transgenic versus wild-type mouse cohorts were performed for each time point and analyzed using Mann-Whitney test; ** denotes P<0.01. Horizontal bars indicate median. Note that in the right panel plotting the percentage of colonized mice in each group, cohorts of PMN-sufficient mice from Fig. 1D were included for comparison. (D) Cohorts of untreated or PMN depleted mice were either left uninfected or were i.n. infected with 108 CFU of Nme MC58 and nasal tissues harvested at 16 h post infection to quantify chemokines KC, MIP-1α, MIP-1 and cytokines TNF-α and IL-1β by ELISA, or myeloperoxidase activity. Group sizes are indicated in graphs. *, **, or *** denote P<0.05, P<0.01, or P<0.001, respectively, in one-way ANOVA applying Tukey's post-hoc comparison of all groups using GraphPad Prism 5.0 software. ns, not significant.