The IL-13 Receptor-α1 Chain Is Essential for Induction of theAlternative Macrophage Activation Pathway by IL-13 but not IL-4

摘要

Macrophages co-express both the IL-2Rγ chain (γc) and IL-13Rα1. These receptor chains can heterodimerize with IL-4Rα to form type-I or type-II IL-4 receptor complexes, respectively. We used macrophages derived from Il2rg and Il13ra1 knockout mice to evaluate the requirements for these receptor chains for induction of the alternative macrophage activation (AMA) pathway by IL-4 and IL-13. Absence of γc significantly decreased activation of STAT6 by IL-4 but not IL-13. However, although activation of STAT6 by IL-4 was markedly reduced in γc KO macrophages, it was not abolished, indicating that IL-4 can still signal through type-II IL-4 receptors via the IL-13Rα1 chain. IL-13 failed to activate STAT6 in macrophages derived from Il13ra1 KO mice; however, these cells remained fully responsive to IL-4. The inability of IL-13 but not IL-4 to signal in Il13ra1^−/− macrophages correlated with the inability of IL-13 but not IL-4 to induce expression of genes such as Arg1, Retnla and Ccl11 that are characteristically expressed by alternatively activated macrophages. In addition, IL-13 but not IL-4 failed to induce membrane fusion and giant cell formation by Il13ra1 KO macrophages. These findings demonstrate that the IL-13Rα1 chain is essential forinduction of the AMA pathway by IL-13 but not IL-4.