d.a.MKK6 expression in neutrophils induces a phenotypic shift to monocytes. (A) MKK6 expression, assessed by western blotting, of neutrophils (G) and monocytes (Mo) either generated in vitro from CD34⁺ cells or isolated from PB. Proteins from equal numbers of cells were separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), blotted, and probed with anti-MKK6 antibody. (B) Schematic representation of culture conditions; d.a.MKK6-transduced day 11 neutrophils were analyzed for CD15 vs MPO; 48 hours later NGFR⁺ cells (d.a.MKK6 expressing) were analyzed for neutrophil (LF) vs monocytic (CD14) marker. Bars represent mean percentages (± standard deviation [SD]) of 3 independent experiments (*P < .05, **P < .01). (C) Expression of neutrophil (C/EBPα, Gfi-1) and monocyte (c-Jun, MafB)-associated transcription factors in FACS-sorted d.a.MKK6-induced or empty-vector control cells in vitro–generated neutrophils was assessed after 24 hours by real-time RT-PCR (means ± SD of 3 independent experiments).