MX1 and infection: In the peripheral blood lymphocytes of ARV-infected SPF chickens, type I IFN (IFN-α, IFN-β), type II IFN (IFN-γ), and ISGs (Mx, IFITM1, and OAS) were all upregulated in the early stage of infection, with their expression peaking at 3 days after infection (Xie et al., 2019).