When primary rabbit kidney cell cultures are treated with either polyadenylic acid-polyuridylic acid or polyadenylic acid-polyribothymidylic acid (poly(rT)) and then judiciously exposed to actinomycin D and cycloheximide, high titers of interferon are found in the extracellular medium ("superinduction") (Vilcek, J. (1970) Ann. N. Y. Acad. Sci. 173, 390-403; Tan, Y. H., Armstrong, J. A., Ke, Y. ...