As shown in Figures 4 and 5 , upon pdmH1N1 and H9N2/G1 virus infection, inflammatory response assayed by cytokines and chemokines production was triggered in both MBL WT and MBL KO mice. Except for IL-2, of which the level remained constantly low during the course of experiment, the kinetics of individual proteins were similar in that they were readily detectable on day 3, reached the highest level on day 7, and declined on day 14. Strikingly, MBL KO mice had reduced inflammatory responses during infection. Among the 14 cytokines examined, the majority of them showed significantly lower amounts in MBL KO mice lung homogenates than in MBL WT mice, including IL-1a, IL-1b, IL-6, IL-10, TNF-a, IFN-c ( Figures 4A and 5A) , KC, MIP-1a, MIP-1b, MCP-1, MCP-3 and RANTES (Figures 4B and 5B) . These results suggested that MBL upregulates the inflammatory response to influenza virus infection, resulting in elevated production of proinflammatory cytokines and chemokines in the MBL WT mice as compared with the MBL KO mice.