86] Measurement of antagonistic effects of growth factors and interferons

Abstract

This chapter describes techniques for the measurement of interactions between interferons (IFNs) and growth factors (GFs) in vitro, in tissue culture of either human diploid fibroblasts or blasts of the cortisone resistant mouse thymocytes, and also in vivo, in mice infected with Moloney sarcoma virus. The proliferation of cells and tissues probably cannot occur without the participation of GFs or substances that either mimic or substitute for GFs. GFs have been defined as endogenous substances produced by various tissues that have multiplication stimulating activity and/or other trophic effects but are not nutrients, antibodies, enzymes, or attachment factors. The majority of GFs are polypeptides of various molecular weight and structure that have a hormone-like mode of action. These include the interleukins that stimulate the proliferation of cells of the immune system. IFNs, as well as GFs, fulfill the main biological and biochemical criteria of hormones. However, the response of various cells and tissues to IFNs is inhibition of the proliferation and other complex reactions not necessarily connected with the cell cycle but clearly antagonistic to GFs. Thus, it has been suggested that IFNs and GFs can be grouped together as nonclassical hormones with opposite actions. Human embryonic diploid fibroblasts (HEF) strains are used between fifth and twentieth passage levels in culture. The cells are found to be sensitive to both human IFN and several GFs.