Fig. 1.

Effects of PR8 infection on body weight and survival rates (A) and the levels of pro-inflammatory cytokines and ectopic trypsin in the lungs (B). Anesthetized C5B7BL/6 J mice were infected intranasally with 5, 25, and 40 pfu of influenza virus PR8 or instilled saline as a control. Mice were sacrificed at days 0, 3, 4, 6, and 8 after infection. The levels of trypsin, IL-1β, IL-6, and TNF-α in the lungs were analyzed by ELISA. Data are the mean ± SD for 10 mice per group. *, P < 0.05 vs. the uninfected group (saline) by Student’s t-test