Determination of cytokine levels in mice after fatal dose (5 × 105p.f.u.) of A/PR/8/34 (H1N1) virus infection. IL-6 (A), IL-10 (B), IFN-γ (C), IL-4 (D), and IL-17 (E). Mice without infection were used as the control group. The dotted lines represented the results of control group. Columns represented mean cytokine concentrations representative of 5~6 mice, and I bars indicated the standard deviations. *p < 0.05, compared with control group.