Properties of interferon induced by purified protein derivative of tuberculin in mice sensitized with BCG or cell-wall skeleton of BCG.

Mice sensitized with either BCG or cell-wall skeleton of BCG (BCG-CWS) produced interferon in blood after stimulation with specific antigen, purified protein derivative of tuberculin (PPD). Both BCG-infected normal (C57BL/6) and thymic nude (BALB/c, nu/nu) mice showed enhanced activity to produce interferon by stimulation with E. coli endotoxin. However, detectable interferon was not produced in athymic nude mice sensitized with BCG or BCG-CWS by stimulation with PPD. Immune-induced interferon (I-IF) produced by BCG-CWS and PPD in mice was different in biological and physicochemical properties from virus-induced interferon. I-IF showed about 100 times more potent L-cell growth inhibitory activity than virus-induced L-cell interferon (L-IF). Both I-IF and L-IF showed macrophage-activating activity, which renders resting macrphages cytotoxic to L1210 leukemia cells. Antiviral and macrophage-activating activity of interferon preparation was not separated physicochemically in this study.