A colorimetric liquid culture assay of a growth factor for primitive murine macrophage progenitor cells

Synergistic factors from media conditioned (CM) by human placentas or the 5637 human bladder carcinoma cell line (SFH-HPCM and SFH-5637 respectively) have the ability to stimulate early progenitor cells in mouse bone marrow to form large colonies in agar cultures after 12-14 days, in the presence of CSF-1. Culture conditions have been examined and a quicker and more convenient liquid culture assay has been developed for this factor, using a tetrazolium salt to quantitate cell proliferation. The use of flat-bottomed vessels, high cell density, supra-optimal doses of CSF-1 or the addition of WEHI-3-CM to these cultures, all resulted in a decrease in the required incubation time. In combination, these modifications reduced the assay time to 4 days.