Expression of CCR2 ligands in BALF, MLN, lung and serum of infected mice. C57BL/6 mice were infected with 200 PFU of 141, SOIV or PR8 viruses. BALF was harvested from naïve or virus-infected mice at days 3 and 7 post-infection (n = 3-4 mice per group). (A) Pooled BALFs were subjected to cytokine or ckemokine expression analysis using cytokine protein arrays. (B) Mice were infected with PR8 viruses. At day 7 postinfection, RNAs were harvested from isolated MLN and lung leukocytes. Relative expression of CCL2, CCL7 and CCL12 in total leukocytes from MLN and lung 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 MLN (mean ± SEM). Experiment (n = 3 mice per group) was performed twice and one representative is shown. (C) Sera were collected from naïve and virus-infected mice at days 3 and 7 post-infection. Concentrations of CCL2, CCL7 and CCL12 in the sera were measured by ELISA (n = 6-11 mice per group, mean ± SEM; ns: no significant difference; *P < 0.05; **P < 0.01; ***P < 0.001).