The antiviral immunity of human placenta and amniotic membrane in an organ culture (OC) system was studied. Freshly isolated explants of most of the placentas at term and the amniotic membranes were found to be relatively resistant to herpes simplex virus type 1 (HSV-1), encephalomyocarditis virus (EMCV), and vesicular stomatitis virus (VSV) infections. After in vitro aging, however, the OC acquired the sensitivity to the viruses. In about 66%-90% of placentas, resistance of freshly isolated explants to the infection was observed. This indicates that the placentas displayed a constitutive immunity against the viruses. To study the role of endogenous cytokines in antiviral immunity, we added specific antibodies neutralizing IFN and TNF activities to VSV-infected OC and checked their influence on viral replication. Increases of 10-fold to 100-fold of VSV replication in the OC treated with anti-TNF-alpha, anti-IFN-alpha, anti-IFN-gamma or anti-IFN-beta sera were observed. The results indicate the importance of the endogenous cytokines in placental and amniotic membrane immunity. However, we did not observe a simple correlation between the spontaneous IFN and TNF production and the level of resistance against viruses. In view of the results, the participation of TNF and IFN in the constitutively expressed immunity of human placenta is of a more complex nature.

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