EBV-cell lines genetically modified to express IL-7Rα do not respond to IL-7 signaling when γc is limiting. (A) Lentiviral vector construct encoding the IL-7Rα cDNA used to transduce EBV cell lines. RSV, Rous sarcoma virus hybrid promoter; SD/SA, splice-donor and spice-acceptor sites; ψ, packaging and dimerization signal; GA, fragment of the HIV-1 gag gene; RRE, Rev responsive element; PPT, central polypurine tract; CMV, human cytomegalovirus immediate-early promoter; WPRE, woodchuck hepatitis virus posttranscriptional regulatory element. (B) Unmodified (left) and IL-7Rα–modified (right) EBV-transformed B-cell lines were immunolabeled with antibody to IL-7Rα and analyzed by FACS. Percentages shown represent the proportion of cells expressing detectable levels of CD127. (C) EBV-γc^wt-IL-7Rα, EBV-γc^low-IL-7Rα and ED-γc-7R cells were labeled with antibody to pSTAT5 before and after IL-7 (1 nM) stimulation (columns 1 and 2, respectively). Counterstaining of IL-7–treated cells with DAPI (column 3). Scale bar represents 50 μm.