TNF and infection: To compare the cytokine responses in mice infected with the H5N6 and H5N8 viruses, expression analysis of Th1-associated cytokines (IL-2, IL-12, and IFN-γ), Th2-associated cytokines (IL-4, IL-5, and IL-10), the pro-inflammatory cytokine TNF-α, and the chemokine GM-CSF were assessed post-infection in BALF.