Exposure to DE during an influenza infection increases the message of Interleukin 4 (IL-4) and decreases the expression of IFN-γ and IL-12p40 cytokines. IL-4, IFN-γ and IL-12p40 gene expression was analyzed in lung RNA on day 1, 4, 8, and 14 p.i. IL-4 protein production was measured in BAL by ELISA at day 1, 4, 8, and 14 p.i. A) Levels of IL-4 mRNA were quantified in lung homogenates by real-time RT-PCR and normalized to levels of β-actin in mice exposed to air or DE during an influenza infection. B) Levels of IL-4 protein were measured in BAL. C) IFN-γ mRNA; D) IL-12p40 subunit mRNA. *significantly different from air or air/flu exposed mice (p < 0.05; n = 11 for influenza infected).