Stromal cell-specific loss of STAT5 induces prominent neutrophilia.

<p>(A) 5×10⁶ wild-type bone marrow cells were injected intravenously into lethally irradiated (1,000 rad) STAT5^−/− mice (WT→KO) and vice versa (KO→WT). 8 weeks later, serum G-CSF concentrations were measured by ELISA. Lethally irradiated wild-type mice reconstituted with wild-type bone marrow (WT→WT) and mutant mice reconstituted with mutant marrow (KO→KO) served as controls. (B) Liver sections were stained to detect G-CSF (brown). Original magnification, 250×. (C) Blood neutrophils were counted. (D) Freshly MACS-purified (T0) and 24-hr cultured (T24) blood neutrophils were assayed for apoptosis using dual color annexin-V-FITC/propidium iodide staining and flow cytometry analyses. (E–H) Mature marrow neutrophils, GMPs, CMPs, and HSCs were counted by flow cytometry. Absolute values were generated by multiplying gated percentages by total cell numbers. (I) Freshly FACS-purified marrow neutrophils, GMPs, CMPs, and HSCs were assayed for apoptosis using trypan blue exclusion.