Printed in Great Britain The Effect of Interferon, Interferon Inducers or Interferon Induced Virus Resistance on Subsequent Interferon Production

The pre-treatment of mouse L cells with interferon or polyinosinic-polycytidylic acid potentiated the interferon response of these cells to subsequent stimulation with suboptimal doses of polyinosinic-polycytidylic acid. This potentiation was manifested as an earlier production of interferon, a faster attainment of maximum interferon production, and a greater yield of interferon. Pre-treatment of cells with either low (5 units/ml.) or high (Iooo units/ml.) doses of interferon ever caused a reduced interferon response to stimulation by polyinosinic-polycytidylic acid. Primary rabbit kidney cells which were pre-treated with interferon (5oo units/ml.) responded to stimulation with polyinosinic-polycytidylic acid in the same manner as did mouse L cells. In contrast, under certain conditions mouse L cells pre-treated with interferon became resistant to stimulation with Newcastle disease virus. The extent of the reduced response depended on the pre-treatment dose of interferon and the stimulating dose of Newcastle disease virus. It was concluded that the presence of interferon and its virus resistant state were not directly correlated with hyporesponsiveness to repeated induction of interferon, at least by rI. rC