Interleukin-3 receptor (IL-3R) is a heterodimeric membrane receptor. The α subunit is essential for ligand binding and confers ligand specificity to the receptor. The common beta chain (ßc) subunit, which is shared by the granulocyte macrophage-colony stimulating factor (GM-CSF), IL-3 and IL-5 receptors, is required for high-affinity ligand binding and signal transduction, mediating growth and survival of hematopoietic progenitor cells and the production and activation of mature hematopoietic cells. In order to investigate the role of IL-3 receptor system (IL-3Rα, GM-CSFRα and hßc) in myeloid differentiation, the expression level of IL-3 receptor system gene in all-trans retinoic acid (ATRA)-induced NB4 cell differentiation was detected by quantitative real time RT-PCR. At the same time, DNA sequence change was analyzed by cDNA sequencing. The results showed that the expression level of IL-3Rα mRNA was obviously down-regulated in NB4 cells treated with ATRA for 24 hours, but during differentiation of ATRA induced NB4 cells, the expression level of IL-3Rα mRNA was gradually restored, while the expression levels of GM-CSFRα mRNA and hßc mRNA were gradually up-regulated. The sequence of IL-3Rα and GM-CSFRα gene did not change before and after NB4 cells differentiation, but the sequence of hßc gene changed when NB4 cells were treated with ATRA, the expression of hßc mRNA sequence before NB4 cell differentiation taken truncated mutation as dominant, as regards expression of hßc mRNA sequence after NB4 cell differentiation, the truncated mutation of hßc mRNA had restored to wild type. It is concluded that the IL-3 receptor abnormality exists in NB4 cells, over expression of IL-3Rα and truncated mutation of hßc may be involved in proliferation and differentiation block in NB4 cells.