TNF and infection: When compared with H7N9-CK or H7N9-HU, H5N1 induced significantly higher levels of IL-8 at 12 h post-infection; IL-8, IL-6, IL-10 and MCP-1 at 24 h post-infection; and IL-8, IL-6, IL-10, MCP-1 and TNF-α at 48 h post-infection (Fig. 1).