MACROMOLECULES STIMULATING HUMAN GRANULOCYTIC COLONY-FORMING CELLS, PRECURSORS OF THESE CELLS, AND PRIMITIVE ERYTHROID PROGENITORS - SOME APPARENT NONIDENTITIES

Abstract

The relationship between molecules having granulocyte colony stimulating activity (G-CSA), erythroid burst-promoting activity (E-BPA), and activity promoting increase in the number of granulocytic progenitors in liquid culture (.DELTA.GPA) was explored in conditioned medium from human leukocytes (HLCM) and human placenta (HPCM). As tested on human hemopoietic progenitors in culture, G-CSA eluted from Sephadex G100 as a single peak with apparent MW of 25,000, separating partially from E-BPA and .DELTA.GPA, which both had an apparent MW of 45,000. All 3 activities eluted together from hydroxyapatite at low molarity phosphate. Their charge properties were also similar and all 3 electrofocused in flat gel beds in the pH range near 5.4. On both hydroxyapatite and isoelectric focusing, .DELTA.GPA sometimes separated partially from the other 2 activities but not consistently. The gel filtration result shows that in conditioned medium of human origin, molecules having G-CSA are not the same as those having .DELTA.GPA, suggesting a dual factor requirement in the granulocytic lineage reminiscent of that in the erythroid pathway. .DELTA.GPA apparently differs from E-BPA. Single micromanipulated cells proved capable of forming erythroid or granulocytic colonies in the presence of either crude or partially purified activity. Human colony-forming cells apparently are direct priamry targets of growth factors in HLCM and HPCM.