title: Unicellular or multicellular origin of human granulocyte-macrophage colonies in vitro.
abstract: The assumption that human granulocyte-macrophage colonies have a unicellular origin and thus are true clones has been directly tested. Cells from seven females heterozygous for the common glucose-6-phosphate dehydrogenase (G-6-PD) gene (GdB) and the variant GdA were cultured in semisolid medium for granulocyte-macrophage colony growth and the enzyme type of individual colonies was determined. When the colony density was less than 20/dish, more than 95% of colonies had either type A or type B G-6-PD, but not both. At colony densities greater than 30/dish, between 15% and 75% of colonies had both enzyme types and therefore arose from more than one cell. These results are consistent with a unicellular origin for the colonies only when they are cultured at low densities. With increasing colony density, there was a greater frequency of colonies with both type A and type B activity, suggesting that accurate enumeration of committed stem cells can only be performed at low colony concentrations.
mesh_terms: D001797:Blood Protein Electrophoresis; D002450:Cell Communication; D002454:Cell Differentiation; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D005956:Glucose-6-Phosphate Isomerase / Q000097:blood; D005954:Glucosephosphate Dehydrogenase / Q000097:blood; D006098:Granulocytes / Q000166:cytology*; D006801:Humans; D008264:Macrophages / Q000166:cytology*; D008297:Male
chemical_list: D005954:Glucosephosphate Dehydrogenase; D005956:Glucose-6-Phosphate Isomerase