Neonatal versus weanling expression of activating and inhibitory markers on microglia. Cells shown in Figure 7 were additionally analyzed for expression of activation markers CD11a (A) and CD86 (B) as well as inhibitory markers CD200R (C) and CD172a (D). Mean Fluorescent Intensity (MFI) of microglia (CD45lo, CD11blo dark blue gate in Figure 7) and both monocyte populations are shown. Monocyte 1 population contained cells that were CD11bint, F4/80hi, Ly6C + (green gate in Figure 7) while monocyte 2 population contained cells that were CD11bhi, F4/80lo, Ly6C + (fuchsia gate in Figure 7). Resident macrophages (light blue gate in Figure 7) were not analyzed since there were not sufficient cells in the neonatal cell population for comparison. No difference was observed between the PBS and LPS treated groups for any marker (data not shown). Data are the mean ± SEM for 3 mice per group. Data were similar from two experiments, although different antibody concentrations were used in the second experiment (not shown). Statistical analysis was completed by two-way analysis of variance with Tukey’s multiple comparisons test. Significant age-specific differences are as indicated: *P < 0.05, **P < 0.01, ***P < 0.001.