Peripheral lipopolysaccharide induces increases in inflammatory monocytes in mouse brain. Adult (8 weeks old) C57BL/6 female mice were injected intraperitoneally with saline or 2 mg/kg lipopolysaccharide (LPS), and CD11b, CD45, Ly6C, Ly6G expressions were determined by flow cytometry from brain cell suspensions isolated 24 hours later. (A) Upper and middle panels show representative bivariate dot plots of Percoll isolated brain cells illustrating a gating strategy to exclude dead cells, debris and aggregated cells, and to determine profiles based on CD11b+/CD45low+ for microglia, CD11b+/CD45high+ for central nervous system (CNS)-associated phagocytes and CD11b−/CD45high+ cells. Lower panels show histograms of average percentage of microglia (left), CNS-associated phagocytes (right) in live single immune cells from brains of saline- (white bars) and LPS-injected mice (black bars). (B) Upper panel shows side scatter (SSC) plot. This shows that, among CNS-associated phagocytes, macrophages/monocytes and neutrophils can be distinguished according to their granulosity. Middle panels show representative bivariate dot plots of phagocytes stained for Ly6G and Ly6C illustrating a gating strategy to identify Ly6Cintermediate+/Ly6Ghigh+ neutrophils, Ly6C−/Ly6G− resident macrophages and Ly6Chigh+/Ly6G− inflammatory monocytes. Lower panels show histograms of average percentage of inflammatory monocytes (left), resident macrophages (middle) and neutrophils (right) in CNS-associated phagocytes population from brains of saline (white bars) and LPS mice (black bars). Bars represent the mean ± SEM. *P < 0.05 versus saline control; ns, non significant; n = 4. FSC, front scatter.