Figure 2: Neutrophils actively infiltrate the meningeal parenchyma after SAH.

A) Flow cytometry of digested meninges showed greater numbers of neutrophils than inflammatory monocytes (CD45⁺/CD11b⁺/Ly6C^hi). There was a trend toward increased neutrophils, but not monocytes, after SAH (left panel). Whole mounted meninges showed that cells that store MPO do not co-localize with Iba1⁺ cells (monocytes/macrophages) suggesting only neutrophils store MPO in the meninges in this model (right panel). B) In whole mounted meninges, neutrophils (anti-7/4) were observed both in the meningeal parenchyma and venous sinuses of sham and SAH groups of the WT and MPOKO mice. The number of neutrophils within the meninges and in the sinuses increased significantly 3 days after SAH in WT but not MPOKO mice. C) Intravenous injection of fluorescein tagged CD45 (CD45-FITC) showed that the increased infiltration is attributed to the active recruitment of neutrophils from the periphery. Arrows represent NT 7/4 labelled cells that are co-labeled with CD45 (scale bar = 50 μm).