Nonviable myeloid cells lose GFP staining.

(A) Unstained peripheral blood leukocytes from 2 animals with TEL/PDGFβR-induced MPD were analyzed for EGFP expression, using high-volume flow cytometry. (B) Spleen cells from GM-CSF^−/− and IL-3^−/− double-deficient mice transplanted with tyrosine kinase fusion oncogenes (as in Figure 3) were analyzed for Gr-1 and EGFP positivity. Gr-1⁺ cells were gated into EGFP⁻ (R1) and EGFP⁺ (R2) populations and were assessed for PI staining. Nonviable cells uptake PI and stain positively. EGFP⁻ cells (R1 gate, left panels) are comprised of both PI-positive and -negative populations. EFGP⁺ cells (R2 gate, right panels) are comprised predominantly of a single population of PI-negative cells.