Cytometric analysis of COS1 (B3GALNT1) cells transfected with M_GBGT1, H_ABO-A, and 3 representative derivative constructs. Cells were cotransfected with DNA from the selected expression construct and DNA from the vector expressing monomer red fluorescent protein (mRFP). Cells were then detached and stained with anti-FORS1 antibody and then with Alexa Fluor 488–linked secondary antibody. The 2 graphs in the top panel correspond to M_GBGT1 transfection. On the left, the selection of cell population by forward- (FSC) and side-scatter (SSC) amplitudes is depicted. Events are dot plotted in pseudocolor, with red representing higher frequency and dark blue the lowest. This selection was maintained for all the other samples. The right graph shows the fluorescence intensity from mRFP, used as transfection control, on the y-axis and the fluorescence corresponding to FORS1 on the x-axis. Both axes are on the logarithmic scale. The upper red rectangle represents the mRFP⁺ cell population, and the percentage is indicated at the upper left corner. The green rectangle corresponds to Alexa Fluor 488⁺ cell population, and the percentage is indicated at the lower right corner. The other panels show the results for other constructs, H_ABO-A, H_ABO-A (GlyGlyAla), H_ABO-A (deleted [del] exon 4), and H_ABO-A (GlyGlyAla and del exon 4), using the same gates.