CTLA4 and coinfection: To summarize, PCV2 and PRRSV co-infection produced significant alterations in the mRNA expression of immune molecules (IFN-α, IFN-γ, TNF-α, IL-1β, IL-10, TGF-β, PD-1, LAG3, CTLA4 and TIM3) in PAMs, which may trigger immunosuppression and, thus hinder viral clearance, lead to persistent infection and increase disease severity.