Cytoplasmic localization of cS5^F in bone marrow cells. (A) Immunocytochemical detection of phosphorylated Stat5 in cS5^F-expressing BM cells and control GFPv BM cells stimulated or not with IL-3. In each case, cells were spun on cytospin slides and analyzed by indirect immunocytochemistry using an anti–P-Y-Stat5 antibody (AX1). (B) The localization of cS5^F was also determined by Western blot analysis using cytoplasmic and nuclear extracts of unstimulated or IL-3–stimulated cS5^F BM cells from 3 different mice that received a transplant.