Figure 1. Cytokine levels in mice infected with pandemic and seasonal H1N1 influenza viruses.

Six to eight week old DBA/2 mice were infected intranasally with 10⁵ TCID₅₀ with a seasonal virus isolate (BN/59), Kentucky (KY/80, KY/136, KY/96, KY/99, KY/104, KY/108, KY/108, KY/110, KY/180, KY/190) or other H1N1 pandemic isolates (CA/07, NY/18) from 2009. Cytokine levels were measured at 3 and 6 DPI as described in the materials and methods and presented as mean +/− SEM (n = 6 per group, although fewer animals were available for lethal isolates).