Wild-type and MBL KO mice, 6-10 weeks of age, were infected intranasally with 30 lL of 10 3 TCID 50 pdmH1N1 virus or 10 5 TCID 50 H9N2/G1 virus. The viral dosage chosen for the experiment was previously demonstrated to be sublethal (data not shown). Mice were inoculated with 30 lL of PBS as the mock treatment. No mice died throughout the 14-day experiment. The body weight of mice, which was a physiological value indicating infection progress and the health of the animals, was recorded daily. Mice receiving mock treatment did not lose body weight, demonstrating the absence of potential harmful effects due to anesthetics and intranasal inoculation (Figure 2A ).