Fig. 4

IRF7 deficiency leads to inflammatory response and infiltration of immune cells into the brain. WT and Irf7^−/− mice were infected intraperitoneally with 10⁴ FFU LGTV (n = 6) and immune cells were isolated from brains for flow cytometric characterization on day 7 post-infection. Upon infection with LGTV, brain immune cells were manually gated based on their size and granularity in the forward scatter and side scatter light (FSC/SSC) and then separated from dead cells and doublets (not shown). Subsequently, infiltrating immune cells were distinguished from brain-resident microglial cells based on their high expression levels of CD45 and CD11b, respectively (red gate; A, B). Compared to WT littermates, infected Irf7^−/−mice displayed high numbers of infiltrating immune cells in the brain parenchyma 7 dpi (C). Furthermore, the surface expression levels of CD45 (D), CD11c (E), and CD11b (F) by microglial cells were assessed. Representative histograms with dashed vertical lines show the frequency (with standard error of the mean) of microglial cells from WT (black tint) and Irf7^−/− mice (red tint) expressing the respective surface marker in comparison to the corresponding FMO control (grey tint) on day 0 and 7 post-infection. Scatter plots display the median fluorescence intensity (MFI) of microglia and highlight an increased activation state of these cells in Irf7.^−/− mice upon infection with LGTV. Data are represented as mean and asterisks indicate statistical significance calculated by 2-way ANOVA with Tukey’s post hoc test, **p< 0.01, ***p < 0.001