Abstract
Earlier studies demonstrated the induction of beta 2-interferon (IFN-beta 2) in human diploid fibroblasts (FS-4 strain) exposed to tumor necrosis factor (TNF). These studies suggested that IFN-beta 2 mediates an antiviral effect in TNF-treated cells and exerts a feedback inhibition of the mitogenic effect of TNF. Here we demonstrate that the expression of the antiviral action of TNF can be enhanced by prior exposure of FS-4 cells to trace amounts of IFN-beta 1. IFN-beta 1, at a higher concentration, can directly increase the expression of IFN-beta 2. Exposure of cells to TNF enhanced IFN-beta 2 (but not IFN-beta 1) mRNA expression in response to poly(I).poly(C), an IFN inducer which is also known to stimulate FS-4 cell growth. Platelet-derived growth factor and interleukin-1 also led to the increased expression of IFN-beta 2. However, platelet-derived growth factor and interleukin-1 could override the antiviral effect of TNF and also that of exogenously added IFN-beta 1. Our data suggest that a complex network of interactions that involves the endogenous production of IFN-beta 2 is triggered by several growth-modulatory cytokines. Cellular homeostasis is likely to represent a balance between the induction of IFN-beta 2 by these cytokines and their ability to override the inhibitory actions of IFN-beta 2.
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