BM-Jak3 cells display accelerated induction of Gr-1 expression following stimulation with GM-CSF.

Myeloblast-enriched BM cells from wild-type (C57/BL6) mice were infected with the retroviral vectors pMSCV-neo (A-C) or pMSCV-Jak3/neo (D-F). Cells were seeded in methylcellulose and selected in the presence of G418. Several colonies from each infection were expanded, transferred to liquid culture, and induced for differentiation with GM-CSF. At the indicated time points, cells were harvested by centrifugation, washed in PBS with 1% FCS, and stained with PE-conjugated anti–Gr-1 antibody. Following staining, the cells were subjected to flow cytometric analysis to determine degree of Gr-1 expression. Gr-1 expression is absent in day 0 BM-Neo (A) and BM-Jak3 (D) cells. In contrast, increased Gr-1 expression is observed in day 4 BM-Jak3 cells (E) compared to BM-Neo cells (B). Similar expression levels are observed in day 8 BM-Neo (C) or BM-Jak3 (F) cells.