Platelet-derived growth factor (PDGF) inhibits priming in synchronous mouse or human fibroblasts producing interferon

Monolayer cultures of Lpa and FS-4, mouse and human fibroblasts that are good producers of interferon were synchronized by contact inhibition and by incubation in 5% platelet poor plasma serum (PPPS) medium. When the quiescent cultures were stimulated for growth by PDGF, pre-treatment with homologous interferon before induction with virus or poly (rI) . poly (rC) did not increase interferon yields. Under similar experimental conditions priming (increased interferon synthesis) was demonstrated in the asynchronous or quiescent Lpa or FS-4 cells pre-treated with homologous interferon. The unprimed cells, whether stimulated for growth with PDGF or not, produced normal amounts of interferon after appropriate induction. We suggest that growth factor (PDGF), a hormone with opposing action to interferon, can inhibit priming but it has little, if any, effect on the basic process of induction of interferon synthesis.