Human myeloid cells possessing high-affinity receptors for granulocyte-macrophage colony stimulating factor

Granulocyte-macrophage colony stimulating factor (GM-CSF) is a glycoprotein which controls growth and differentiation of hemopoietic cells to form mature granulocytes and macrophages. The presence of specific high-affinity receptors for this factor on myeloid cell lines was investigated using radiolabelled recombinant human GM-CSF. Eight cell lines representing different stages of myeloid differentiation were examined. Equilibrium binding at 37 degrees C using different concentrations of 125I-GM-CSF and Scatchard Plot analysis was used to determine the equilibrium dissociation constant and the average number of receptors per cell. Low receptor numbers were found with an average of 74 on HL-60 cells and decreasing numbers on U-937, KG-1, X-376 and THP-1. Receptors were not detectable on RC-2A, CTV-2 and HEL cells. Other cell lines were also investigated including a Burkitt type ALL cell line, X-308 and a Hodgkin's tumor cell line, L 428 KSA. No receptors were detectable on these lines. Normal blood mononuclear cells were examined and indicated that more mature cells have a higher receptor density. Receptors were detectable on normal bone marrow cells but the nature and receptor density of the binding cells remains to be elucidated.