Regulation of Interleukin-2 Receptor γ Chain mRNA Expression in Human Monocytic Cell Line THP-I

The interleukin-2 receptor (IL-2R) γ chain (γc chain) is shared by IL-4R, IL-7R, IL-9R, and IL-15R and plays an important role in regulation of the immune system. However, its regulation in monocytic cell lines has not been well clarified. We examined the expression and regulation of the IL-2Rα, IL-2Rβ, γc chain, IL-4R and IL-7R mRNA in a human monoblastic leukemia cell line, THP-1. Unstimulated THP-1 cells constitutively expressed a low level of γc chain and IL-4R mRNA, Phorbol myristate acetate (PMA) induced macrophage-like differentiation and up-regulated the γc chain mRNA expression in THP-1 cells. This effect of PMA was suppressed by the protein kinase inhibitors H-7 and staurosporine. PMA did not affect the expression of the other IL-R mRNAs examined. 1 α, 25(OH)₂D₃ and interferon-γ also induced differentiation of THP-1 cells, but these reagents did not affect the expression of the IL-R mRNAs in THP-1 cells. These findings suggest that the expression of the γc chain mRNA is regulated by the PMA-dependent pathway and is not associated with that of the other IL-R mRNAs.