An autocrine activity capable of substituting for serum in cell cultures.

Abstract

Provided that high cell densities (above 10(6)/ml) are maintained, a factor-dependent murine hemopoietic progenitor cell line (FDC-P1) will proliferate in serum-free medium. The conditioned medium (CM) from high-density FDC-P1 cells permits the serum-free survival of FDC-P1 cells even at low density, indicating the existence of a diffusible autocrine factor. The requirement of FDC-P1 for a colony-stimulating factor (either IL-3 or GM-CSF) is not abrogated by culturing the cells at high cell density or in the conditioned medium. Furthermore, the CM from FDC-P1 enhances the mitogenic stimulation of normal human skin fibroblasts (HSF) by epidermal growth factor (EGF): i.e., the lag period befor..