Changes in survival rate and apoptotic rate of swine alveolar macrophages (AMs). Changes in (A) survival rate and (B) apoptotic rate in PCV2- and/or PRRSV-inoculated swine alveolar macrophages (AMs) were determined by trypan blue dye exclusion assay and TUNEL assay, respectively. Data are expressed as the level different from that of the mock-inoculated AMs (Mock) and shown as mean ± SD of three independent experiments. PCV2: AMs inoculated with PCV2 alone; PRRSV: AMs inoculated with PRRSV alone; PCV2/PRRSV: AMs inoculated with PCV2 first then inoculated with PRRSV 18 h later; PRRSV/PCV2: AMs inoculated with PRRSV first then inoculated with PCV2 18 h later; PCV2-PRRSV: AMs co-inoculated with PCV2 and PRRSV simultaneously. ** (P < 0.01), *** (P < 0.001)The difference between the two treatment groups at the same h post inoculation (HPI) with the first virus is statistically significant. aValues are significantly different from the Mock at the same h post inoculation (HPI) with the first virus.