Fractionated populations of normal human marrow cells respond to both human colony-stimulating factors with granulocyte-macrophage activity.

Populations of normal human colony-forming cells (blast cells) and cluster-forming cells (promyelocytes-myelocytes) were obtained from bone marrow by using the monoclonal antibody WEM G11 and the fluorescence-activated cell sorter (FACS). Both populations were shown to be responsive to both human colony-stimulating factors (CSFs) with granulocyte-macrophage activity (CSF alpha and CSF beta), with the cluster-forming cell population being more responsive to CSF beta than the colony-forming cell population. The clonal proliferation of promyelocytes-myelocytes was transient, and the clones generated were of subcolony size (less than 40 cells) regardless of the CSF used. Clone transfer experiments demonstrated that progeny of promyelocytes-myelocytes initiated using one stimulus (CSF alpha or CSF beta) were also responsive to the other stimulus.