Identification Through Chemical Cross-linking of Distinct Granulocyte-macrophage Colony-stimulating Factor and Interleukin-3 Receptors on Myeloid Leukemic Cells, KG-1

Granulocyte/macrophage colony-stimulating factor (GM-CSF) and interleukin-3 (IL-3) each bind specifically to a small number of high-affinity receptors present on the surface of the cells of the acute myelogenous leukemia line, KG-1. Through chemical cross-linking of IL-3 and GM-CSF to KG-1 cells, we identified distinct binding proteins for each of these cytokines with approximate molecular masses of 69 and 93 Kd, respectively. Although these two binding proteins are distinct, GM-CSF and IL-3 compete with each other for binding to KG-1 cells. Other cell lines, which express receptors for either factor but not for both do not display this cross-competition for binding with IL-3 and GM-CSF. These findings imply that distinct IL-3 and GM-CSF binding proteins are expressed on the cell surface and that an association exists between these proteins on KG-1 cells.