I'm attempting to examine IL-6 and IFN-alpha1 signaling to Stat3 in my cell system. I have both ligands and an anti-phospho-Stat3 (Y705) antibody (Cell Signaling, cat.#9131). Can anyone recommend a cell line that would function as a positive control for Stat3 phosphorylation upon activation with these ligands, detectable via immunofluorescence? Per the Cell Signaling website, IFN-alpha1 treatment of HeLa cells induces a strong nuclear signal with this antibody, after overnight serum starvation (0% serum) and treatment with 100 ng/ml IFN-alpha1 for five minutes. This gives me a starting point, but does anyone recommend other conditions? I appreciate any guidance you can provide. Thanks!