Effects of hematopoietic growth factors on in vitro colony formation by human megakaryocyte progenitor cells.

In order to study the effects of recombinant and purified hematopoietic growth factors on megakaryocyte (MK) progenitor cells (CFU-MK), enriched populations of human CFU-MK were isolated utilizing fluorescence activated cell sorting after labelling of cells with monoclonal antibodies exhibiting specificity to the My10 (HPCA-1) antigen and the major histocompatibility (MHC) class II (HLA-DR) locus. The CFU-MK cloning efficiency (CE) was 1.1 +/- 0.5% for cells expressing both high densities of My10 and low densities of HLA-DR (My10 DR+). This procedure resulted in an 18 fold increase in CE over NALT- cells. The effects of natural or recombinant human hematopoietic growth factors including erythropoietin (Epo), thrombocytopoiesis stimulating factor (TSF), interleukin 1 alpha (IL-1 alpha), granulocyte colony stimulating factor (G-CSF), granulocyte-macrophage colony stimulating factor (GM-CSF), macrophage colony stimulating factor (CSF-1), and interleukin 3 (IL-3) on MK colony formation by My10 DR+ cells were determined utilizing a defined medium assay system. Neither Epo, TSF, CSF-1, IL-1 alpha nor G-CSF alone augmented MK colony formation above baseline (2.5 +/- 0.8 per 5 x 10(3) My10 DR+ cells plated). By contrast, the addition of GM-CSF and IL-3 each increased CFU-MK colony formation with maximal stimulation occurring following the addition of 200 units/ml of IL-3 and 100 units/ml of GM-CSF. At maximal concentration, IL-3 had a greater ability to promote megakaryocyte colony formation than GM-CSF.