CCL2 and influenza: The analyses revealed that relative to H7N9 infection, H9N2 infection was characterized by an earlier induction of immune response in the lung, as evidenced by prompt induction of interferon-induced genes and proinflammatory cytokines with key roles in the host’s response to influenza infection, including IL-10, IL-12β, MCP1, IL-1β, IL-6, and TNF-α, which occurred as early as 0.25 dpi (Figures 2A, B).