title: Limiting-dilution analysis of the effects of colony-stimulating factors, phytohemagglutinin, and hydrocortisone on hematopoietic progenitor cell growth.
abstract: The effects of colony-stimulating factors (CSFs), phytohemagglutinin (PHA), and hydrocortisone on the growth of human bone marrow hematopoietic progenitor cells (granulocyte-macrophage; GM) were analyzed in a limiting-dilution assay (LDA). Both low-density bone marrow cells separated by discontinuous Percoll gradients and a T cell-depleted and progenitor-enriched cell fraction obtained by the combination of counterflow elutriation centrifugation and Percoll gradients were examined in LDA. GCT (monocytoid cell line-conditioned medium containing GM-CSF), human placenta-conditioned medium, bladder carcinoma cell line 5637-conditioned medium (containing GM- and G-CSF), and recombinant CSF (G-CSF) directly induced proliferation of progenitors with single-hit kinetics. In some instances, however, PHA-stimulated lymphocyte-conditioned medium (containing G- and GM-CSF) showed deviation from single-hit kinetics, which demonstrated the presence of factor(s) suppressive to progenitor growth. In a T cell-depleted, progenitor-enriched fraction, PHA alone was found to suppress progenitor growth at a level as low as 100 ng/mL. The addition of hydrocortisone (10(-6) mol/L) increased the progenitor frequency but suppressed progenitor growth at 10(-4) mol/L. LDA appears to be a valuable method for exploring mechanisms of factors regulating hematopoietic cell growth.
mesh_terms: D001854:Bone Marrow Cells; D002455:Cell Division / Q000187:drug effects; D002469:Cell Separation / Q000379:methods; D003115:Colony-Stimulating Factors / Q000494:pharmacology*; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000187:drug effects; D006801:Humans; D006854:Hydrocortisone / Q000494:pharmacology*; D007700:Kinetics; D010835:Phytohemagglutinins / Q000494:pharmacology*; D012016:Reference Values
chemical_list: D003115:Colony-Stimulating Factors; D010835:Phytohemagglutinins; D006854:Hydrocortisone