A growth factor produced by WEHI-3 cells for murine high proliferate potential GM-progenitor colony forming cells

Media conditioned by a myelomonocytic leukemic cell line (WEHI-3) have been found to produce a haemopoietic growth factor (referred to as "synergistic activity" (SA)), which in combination with pregnant mouse uterus extract (PMUE) acts on a primitive granulocyte - macrophage progenitor cell to promote the growth of large colonies in agar. The highest levels of SA have been obtained by conditioning serum free medium with WEHI-3 cells which had been grown in BALB/c mice. This activity was unaffected by storage at 4 °C and -20 °C for 6 months, and was stable between pH 2.0 and 10.6 and stable to heat up to 50 °C but not above. The SA was however, unstable to trypsin digestion, 8 M urea at pH 8.0 with and without Mercaptoethanol (ME, 4mM), and to ME alone at pH 8.0. The SA has an apparent molecular weight between 9,000 and 25,000, it has an isoelectric point in the range of pH 4.0 to 6.5 and does not bind to Con-A.