IL-4 and growth factors amplify STAT6 activation.

<p><b>A, B</b>) STAT6 activation measured in a luciferase reporter assay in BHK cells stimulated for 24 h with growth factors and a sub-maximal concentration of IL-4. <b>A</b>) IL-4 (3 IU/mL) and/or FGF-2 (20 ng/mL) and <b>B</b>) IL-4 (6 IU/mL) and/or IGF-1 (100 ng/mL). Shown is the mean and SEM of STAT6 activity determined by luminometry from a single experiment that was representative of 3 independent experiments. <b>C, D</b>) Immunoblots of cell lysates (not immunoprecipitation as shown in <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1004165#ppat-1004165-g008" target="_blank">Fig. 8B</a>) showing phospho-STAT6 in BMDMs stimulated for 20 min with <i>L. donovani</i> promastigotes and <b>C</b>) IL-4 (8 IU/mL) and/or FGF-2 (20 ng/mL) or <b>D</b>) IL-4 (20 IU/mL) and/or IGF-1 (100 ng/mL). Bars represent the mean and SEM of fold change with reference to the uninfected, unstimulated (Uns) controls calculated by densitometry analysis of immunoblot bands from 3 independent experiments. Also shown is a representative individual immunoblot. <b>E</b>) IL-4-mediated activation of STAT6 in infected BHK fibroblasts is reduced by inhibition of FGFR and IGF-1R but not ERK. The cells were exposed to the control (DMSO) or FGFR inhibitor (FGFRi; PD166866; 10 µM), IGFR inhibitor (IGFRi; PPP; 5 µM), or ERK inhibitor (ERKi; PD98059; 5 µM) for 1 hr and then stimulated for another 24 hrs with IL-4 (25 IU/mL) in the presence or absence of inhibitor. Shown is the mean and SEM of STAT6 activity determined by luminometry from a single experiment that was representative of 2 independent experiments.