a, Representative image of CD31 staining in whole-mount meninges (scale bar, 2,000 µm). b, Representative images of T cells (CD3e, arrowheads) in the dura/arachnoid, pia, dural sinuses, and choroid plexus (scale bars, 70 µm). c, Quantification of T-cell density in different meningeal compartments (mean ± s.e.m.; n = 6 animals each group from 2 independent experiments; ***P <0.001; Kruskal–Wallis test with Dunn’s post hoc test). d, Quantification of MHCII-expressing cells in different meningeal compartments (mean ± s.e.m.; n = 6 animals each group from 2 independent experiments; ***P <0.001; Kruskal–Wallis test with Dunn’s post hoc test). e, Adult mice were injected i.v. with 100 µl of DyLight 488 lectin 5 min before euthanasia to enable labelling of the cardiovascular system. Meninges were harvested and stained with anti-CD3e. Representative orthogonal images of T-cell localization in the lumen (white arrowhead) and outside of the sinus (yellow arrowhead; n = 2 mice; scale bar, 70 µm). f, Adult mice were injected i.v. with 10 µg of FITC-conjugated anti-CD45 antibody or FITC-conjugated isotype antibody. Meninges were harvested one hour after the injection and labelled with anti-CD3e. Representative images of CD3e immunolabelling around dural sinuses are shown. CD45-positive cells do not co-localize with CD3e+ cells (a), suggesting an abluminal localization of the latter (n = 2 mice each group; scale bars, 20 µm). g, Representative 3D reconstruction of the lymphatic vessels localization around the superior sagittal sinus. Adult mice were injected i.v. with 100 µl of DyLight 488 lectin 5 min before euthanasia in order to stain the cardiovascular system. Meninges were harvested and labelled with anti-Lyve-1. The lack of lectin staining in the Lyve-1-positive meningeal lymphatic vessels suggests that they are independent of the cardiovascular system (n = 3 mice; scale bars, left, 50 µm and right, 120 µm). The mounting of the whole meninges results in the flattening of the sinus, thus it does not appear tubular.