We present evidence showing that TNF is capable of inducing an antiviral state in WISH cells thereby protecting them from the cytopathic effect of vesicular stomatitis virus. Establishment of the antiviral state requires pretreatment with TNF. Such pretreatment not only protects the cells in a dose-dependent manner, but it markedly reduces virus yield as well. Kinetic studies have shown that a pretreatment period as short as 4 h at 37 degrees C is effective in conferring protection. The antiviral activity of TNF could be attributed to the induction of IFN-beta. In fact, polyclonal antibodies to IFN-beta completely neutralized the antiviral state elicited by TNF. 2-5A synthetase activity was significantly enhanced when the cells were treated with doses of TNF that afforded antiviral protection. Finally, addition of specific antibodies to IFN-beta 2 (IL-6) during TNF pretreatment failed to abolish the antiviral state, thus suggesting that IFN-beta 2 is not involved in the TNF-induced antiviral state. Also, a homogeneous IFN-beta 2 preparation failed to exert antiviral activity in our cell system.