[Cytostatic activity of soluble factors secreted by inactivated peritoneal macrophages of Syrian hamsters, relative to normal, transformed and tumor cells].

Two strains of RSV-SR in vitro transformed hamster embryo cells appeared to be significantly less susceptible to cytostatic factor (CSF) produced by non-activated macrophages (Mph) of Syrian hamsters as compared with normal hamster embryo cells (HE), or HE cells spontaneously transformed in vitro (STHE). Three out of four highly malignant variants of STHE cells selected in vivo were significantly less susceptible to CSF of Mph as compared with parental STHE cells. The possible role of CSF of non-activated Mph in the regulation of proliferation of normal, transformed and tumour cells is discussed.