TNF and infection: IL-6 was first induced at 8 h post-infection (h.p.i.), IP-10 and RANTES were induced after 24 h.p.i. However, H9N2 did not significantly increase IL-1β (Fig. 1D), MCP-1 (Fig. 1E) and TNF-α (Fig. 1F) in HPMECs.