By day 2 after infection, significant elevations in the levels of interleukin-1β (IL-1β), TNF-α, IL-6, IFN-γ, IFNα, IFNβ, CXCL1, CCL2, and CCL5 were detected in the airways of influenza virus–infected mice (Fig. 4A). Here, CCL2 is linked to infection.