IL-10 was up-regulated in PRRSV-infected macrophages. PAMs and BMDMs were infected with PRRSV or UV-inactivated virus at an MOI of 1. Cells stimulated with LPS (1 μg ml-1) were used as positive control. (a), (c), (e) Cells were harvested at the indicated time points and real-time PCR was performed to evaluate IL-10 mRNA levels. (b), (d), (f) Measurement of secreted IL-10 protein levels in the supernatant of PRRSV-infected PAMs and BMDMs at indicated time points by ELISA. The results represent means ± SD of three independent experiments. *Significant difference (P < 0.05) from media control using Student’s t-test.