CXCL8 and infection: At 2-day post-infection, gene expression for IL-1β was significantly elevated in PC group compared to NC and EXP groups (P < 0.05), but no significant difference was found between NC and EXP groups (P > 0.05); with regard to IFN-γ, IL-8, and TNF-α production, no significant difference was observed among EXP, PC, and NC groups (P > 0.05).