Fig. 3.

Inflammatory monocyte infiltration during acute infection requires CCR2. Brain-infiltrating leukocytes were collected from C57Bl/6 mice (WT; a, c) and CCR2^−/− mice (b, d) at 18 hpi. Flow plots in (a–d) show cells in a CD45⁺ parent gate. The number of inflammatory monocytes (IM; CD45^hiCD11b⁺Gr1⁺⁺1A8⁻), neutrophils (N; CD45^hiCD11b⁺⁺Gr1⁺1A8⁺), and microglia (M; CD45^midCD11b^midGr1⁻1A8⁻) was measured by flow cytometry. The percent of inflammatory monocytes, neutrophils, and microglia in the CD45⁺ population is shown as mean ± 95%CI calculated from nine mice per genotype in three separate experiments (3 × 3) (e). Data were analyzed by Dunnett’s method. No difference in microglia was observed, but neutrophils were significantly increased in CCR2^−/− mice (P = 0.0012 vs WT). Notably, the absence of CCR2 robustly inhibited inflammatory monocyte infiltration (P = 0.0004 vs WT). **P < 0.001