Changes in cytokine levels in each experimentally infected group. (A) The concentration of TNF-α was significantly higher in the HP-PRRSV/PCV2 group than in the other groups. The concentrations of IFN-γ (B) and GM-CSF (C) were lower in the coinfection groups, especially the HP-PRRSV/PCV2 group, than in the single-infection groups. (D) The concentration of IL-10 was higher in the coinfection groups, especially the HP-PRRSV/PCV2 group. Error bars show the standard deviations. * indicates significantly higher or lower values. * p < 0.05, ** p < 0.01; and n.s., not significant.