Fig. 3.
IL-4 activates a number of signaling pathways, including signal transduction and activators of transcription (STAT) 6 and IRS (insulin receptor substrate) 1 through IL-4 receptor (IL-4R). IL-4R is composed of α chain (IL-4Rα) and γ (γc) α chain; however, other forms do exist because of formation of heterogeneous structures with a component of α γ chain, which is shared with the IL-2r IL-13 receptor (IL-13α1) Signal transduction through IL-4R is thought to involve activation of IRS1/2 and STAT6, which leads to cell proliferation and activation of gene transcription. A number of polymorphisms have been identified within the IL-4Rα gene and several of these result in amino acid coding changes. Several of these polymorphisms have been shown to have effects on IL4 signal transduction. However, the precise effects of each polymorphism and combinations of these polymorphisms are still unclear.