TNF and viral infectious disease: We reported that influenza virus replicates in both cultured chorion and amnion cells, while in only chorion cells the virus infection induces apoptosis and the expression of a set of pro-inflammatory cytokine genes, such as interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α, interferon (IFN)-β and IFN-γ (Uchide et al. 2002a, 2002b).