CCR2+ inflammatory monocytes produce high amounts of CCR2 ligand. Total leukocytes were harvested from naïve or virus-infected mice at day 7 post-infection. (A) Gr1 + CD11b + and Gr1-CD11b- cells were sorted form total leukocytes using a cell sorter. (B) RNAs were extracted from total leukocytes, Gr1 + CD11b + sorted cells and Gr1-CD11b- sorted cells from the virus-infected mice indicated. Experiment (n = 3-6 mice per group) was performed at least twice and one representative is shown. (C) Isolated leukocytes were stained with anti-Gr1, -CD11b and -Ly6G Abs. Gr1 + CD11b + Ly6G + and Gr1 + CD11b + Ly6G- cells were sorted. (D) RNA was extracted from total leukocytes, Gr1 + CD11b + Ly6G + sorted cells and Gr1 + CD11b + Ly6G- sorted cells from PR8-infected mice and expression of CCL2, CCL7 and CCL12 was measured by RT-QPCR. The mRNA relative folds were determined by normalizing the level of each group to the corresponding GAPDH level and then to total leukocytes from naïve mice (mean ± SEM; ns: no significant difference; *P < 0.05; **P < 0.01; ***P < 0.001). Experiment (n = 4-5 mice per group) was performed twice and one representative is shown.