Low levels of interferon in the culture medium of mouse K/Balb cells: Detection by the induction of 2–5A-synthetase in L-929 cells

Abstract

Summary K/Balb cells (mouse cells transformed by the Kirsten sarcoma virus) contain high levels of pppA(2′p5′A)n synthetase (2–5A-synthetase) probably due to the constitutive production of trace amounts of interferon. Here we confirm this by assaying the capacity of the culture medium of K/Balb cells to induce 2–5A-synthetase in another type of mouse cells, L-929, which contain low levels of 2–5A-synthetase without treatment with interferon. The results indicate the presence of interferon activity corresponding to 10 to 20 effective antiviral units per ml of culture medium of K/Balb cells. Induction of 2–5A-synthetase in L-929 cells, therefore, provides a useful system for assay of trace amounts of mouse interferon.