Flow cytometric analysis of transgene expression in cell subpopulations. (A) The percentage of transgene-expressing cells in different peripheral blood leukocyte subpopulations and bone marrow CD34⁺ cells are shown for dogs G272 and G306. In all dogs, EGFP-expressing cells were found in all lineages examined. (B) Gating on red blood cells (RBCs) and platelets (PLTs) was based on scatter characteristics (SSC-H is side scatter height and FSC-H is forward scatter height). (C) EGFP-expressing (FL-1H) red blood cells (top) and platelets (bottom) are plotted with side scatter for a control animal and for animal G306. Because of the overlapping positive and negative populations due to low fluorescence intensity, especially in red blood cells, the percentages of marked cells (1.2% in red blood cells, 8.1% in platelets) likely underestimates the actual percentage of transduced cells.