Park L S, Friend D, Price V, Anderson D, Singer J, Prickett K S, Urdal D L
Immunex Corporation, Seattle, Washington 98101.
J Biol Chem. 1989 Apr 5;264(10):5420-7.
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.
用¹²⁵I标记的重组人白细胞介素-3（IL-3）来研究人细胞上IL-3受体的特性和分布。在原代单核细胞、某些KG-1细胞株以及前B细胞系上发现了受体。在37℃时结合迅速，而在4℃时需要数小时才能达到平衡。平衡结合研究表明，IL-3与一类高亲和力受体（每个细胞少于500个受体）结合，其解离常数（Ka）约为1×10¹⁰ M⁻¹。抑制研究显示，人粒细胞/巨噬细胞集落刺激因子部分抑制¹²⁵I-IL-3与人单核细胞的结合，但不抑制与JM-1细胞的结合。进一步分析表明，在KG-1细胞上，IL-3和GM-CSF都能部分竞争异源放射性标记配体的特异性结合，且能力大致相当。这种竞争在37℃和4℃时均会发生。这些结果提示IL-3和GM-CSF的结合位点存在异质性，其中一部分受体仅结合IL-3，一部分仅结合GM-CSF，另一部分则能以高亲和力同时结合两者。¹²⁵I-IL-3与KG-1细胞的平衡结合显示出双相Scatchard图，其中包含在单核细胞和JM-1细胞上未观察到的低亲和力成分，这进一步提示了异质性。
