Stimulation of interferon yields from cultured human cells by calcium salts

Induction of plasminogen activator in a human diploid fibroblast cell line (MRC-5) by conditions which cause induction of interferon: the role of calcium ions

The human diploid fibroblast cell line, MRC-5, derived from embryo lung tissue produced only small quantities of plasminogen activator (PA) when harvested using a standard nutrient medium (Eagle's Minimal Essential Medium, MEM). Use of a schedule designed to induce high concentrations of fibroblast interferon in these cells also resulted in production of considerably enhanced levels of PA. The kinetics of PA production differed from those of interferon production; specifically, PA was produced for at least 6 days following induction despite the toxicity of the inducers whereas interferon synthesis continued for only 1 day. Further investigation of the induction conditions for PA revealed that double-stranded RNA which was absolutely required for interferon production was not required for induction of PA. Indeed, the stimulus for enhancement of PA production appeared to be solely an elevated concentration of calcium ions in the extracellular medium. The possible physiological relevance of this induction of PA by elevated concentrations of calcium ions is discussed.

Production and purification of human MG63 cell interferon

MG63 cells induced by Sendai virus were a convenient source of human interferon, which was of the beta type in antigenicity. When analyzed by SDS-polyacrylamide gel electrophoresis (SDS-PAGE), the interferon migrated as a single component with a molecular weight of 22,000 daltons. It was purified to apparent homogeneity by chromatography on Blue Sepharose, followed by SDS-PAGE, and estimated to have a specific activity of 4 x 10(8) international units/mg of protein.

Effect of CaCl2 on production of interferon and synthesis of its mRNA in human MG-63 cells

The effect of excess CaCl2 addition on the production of interferon and synthesis of its mRNA in a human cell line was investigated. Human MG-63 cells which were treated with 7 mM CaCl2 after poly(rI).poly(rC) induction produced 3 to 10 times as much interferon as control cells. Increased interferon mRNA activity was obtained from CaCl2 treated cells, suggesting that there was an increased interferon mRNA production in these cells.