Effect of Ras on monocyte development. (A) Dual parameter dot plots showing expression of M-CSFR and the myeloid antigen, CD64, on day 3 cells; data are gated on GFP⁺ cells. Figures indicate the percentage of M-CSFR⁺ cells ± SD; quadrants delineate background staining using isotype-matched controls. (B) Changes in the frequency of GFP⁺, M-CSFR⁺ cells with subsequent culture. (C) Total GFP⁺, M-CSFR⁺ cells. (D-F) Differentiation antigen expression on GFP⁺, M-CSFR⁺ cells. (G) Morphology of GFP⁺, M-CSFR⁺ cells sorted on day 9 (arrows indicate mature macrophages); Wright-Giemsa stain (Leica DM4000B microscope, 40×/0.75 HCL PL objective lens, Leica DC500 digital camera, and Leica IM50 version 4.0 software (Leica, Cambridge, United Kingdom). original magnification ×400). Error bars represent extent of positive or negative SD, shown separately for clarity (n = 6). *P ≤ .05; **P ≤ .01.