We examined the expression of mRNAs for inflammatory cytokines and Fas in cultured human fetal membrane cells responding to influenza virus (IV) infection using the reverse transcriptase-polymerase chain reaction (RT-PCR). Primary cultured chorion and amnion cells prepared from human fetal membranes were infected with IV. Chorion cells expressed significant amounts of interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α, interferon (IFN)-β, IFN-γ and granulocyte macrophage colony-stimulating factor (GM-CSF) mRNAs and small amounts of Fas mRNA in response to IV infection. Amnion cells expressed TNF-α and IFN-β mRNAs in response to IV infection, while expression of the other mRNAs was not altered. We also examined whether or not TNF-α, IFN-β, IFN-γ and Fas participated in IV infection-induced apoptotic DNA fragmentation in chorion cells. Neutralizing antibodies against them did not inhibit DNA fragmentation. These results suggested that chorion cells expressed significant amounts of mRNAs for inflammatory cytokines in response to IV infection, and that, in contrast, mRNA expression was quiescent in amnion cells. Moreover, TNF-α, IFN-β, IFN-γ and Fas do not appear to be directly involved in the apoptosis induction of IV-infected chorion cells. The results indicated that chorion cells may play a role in defense against IV through an antiviral immune response and apoptosis to eliminate own cells and viral pathogens in infected organs, whereas amnion cells do not play such a role.