CCL2 and susceptibility to pneumonia measurement: Interestingly, we found some cytokines (GM-CSF, TGF-α, IL-6, IL-1β, IL-15, et al) or chemokines (MCP-1, MIP-1a, et al.)showed two waves of production enhancement.(Fig 7)The first wave of these cytokines and chemokines was activated early on 3 dpi and sharply decreased on 5–7 dpi, when the severe pneumonia was observed in lung tissues.