Stimulation by human placental conditioned medium of hemopoietic colony formation by human marrow cells

Medium conditioned by human placental tissue was found to stimulate granulocytic and monocytic colony formation by human marrow cells in semisolid agar cultures. The colony-stimulating activity of unfractionated conditioned medium was equivalent to the activity of standard peripheral blood underlayers. Placentas were a reliable source of active material, and one placenta provided enough material to stimulate 5,000-10,000 cultures of normal or leukemic cells. The colony-stimulating factor in human placental conditioned medium (CSFHPCM) was concentrated and purified 1800-fold using ammonium sulfate precipitation, calcium phosphate gel absorption, DEAE-cellulose batch absorption, gel filtration on Sephadex G-150, and polyarcylamide gel gel electrophoresis. The active factor behaved on gel filtration as a macromolecule with an apparent molecular weight of 30,000 daltons. The active factor in placental conditioned medium was not dependent on the presence of adherent marrow cells with endogenous colony-stimulating activity.