Heterogeneity in human interleukin-3 receptors. A subclass that binds human granulocyte/macrophage colony stimulating factor.
125I-Labeled recombinant human interleukin-3 (IL-3) was used to study the characteristics and distribution of receptors for IL-3 on human cells. Receptors were found on primary monocytes, on some strains of KG-1 cells, and on pre-B cell lines. Binding was rapid at 37 degrees C, while requiring several hours to reach equilibrium at 4 degrees C. Equilibrium binding studies indicated that IL-3 bound to a single class of high affinity receptor (less than 500 receptors/cell) with a Ka of approximately 1 x 10(10) M-1. Inhibition studies revealed that human granulocyte/macrophage colony stimulating factor partially inhibited the binding of 125I-IL-3 to human monocytes but not JM-1 cells. Additional analysis showed that on KG-1 cells, both IL-3 and GM-CSF partially competed specific binding of heterologous radiolabeled ligand, with approximately equivalent capacities. This competition occurred at both 37 and 4 degrees C. These results suggest heterogeneity in the binding sites for IL-3 and GM-CSF in which a subset of receptors binds only IL-3, a subset only GM-CSF, and another subset can bind both, all with high affinity. Additional heterogeneity was suggested by equilibrium binding of 125I-IL-3 to KG-1 cells which revealed a biphasic Scatchard plot containing a low affinity component not observed on monocytes and JM-1 cells.
Park
L S
LS
Immunex Corporation, Seattle, Washington 98101.
Friend
D
D
Price
V
V
Anderson
D
D
Singer
J
J
Prickett
K S
KS
Urdal
D L
DL
D001667:Binding, Competitive; D002460:Cell Line; D003115:Colony-Stimulating Factors / Q000378:metabolism*; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D006133:Growth Substances / Q000378:metabolism*; D006801:Humans; D007377:Interleukin-3 / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D008024:Ligands; D011971:Receptors, Immunologic / Q000378:metabolism*; D016185:Receptors, Interleukin-3; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism
D003115:Colony-Stimulating Factors; D006133:Growth Substances; D007377:Interleukin-3; D008024:Ligands; D011971:Receptors, Immunologic; D016185:Receptors, Interleukin-3; D011994:Recombinant Proteins; D016178:Granulocyte-Macrophage Colony-Stimulating Factor