Synthesis of two distinct interferons by human fibroblasts.

Human interferon species Le and F can be distinguished on the basis of their distinct antigenic, biological, and physicochemical characteristics. Until now, Le interferon was thought to be produced only in cells of lymphoid origin. This study demonstrates that cultures of human fibroblast cell strains GM-258 and FS-4 produce both F and Le interferons. Le interferon constituted up to about 20% of the total interferon activity produced in fibroblast cultures after stimulation with Newcastle disease virus or vesicular stomatitis virus. In contrast, only F interferon was detected in preparations obtained after induction with polyinosinate-polycytidylate. These results indicate that the Le interferon gene is inducible in cells of nonlymphoid origin and that the expression of this gene depends on the nature of the inducing agent.