Flow cytometry detection of mCD24 expression by peripheral blood CD3⁺ naı̈ve and memory T lymphocytes at about 3 to 4 weeks after transplantation with autologous CD34⁺ PBSC transduced with MFGS-mCD24. For all of the dot-plot analyses shown in this figure, an initial collection gate was established to analyze only CD3⁺ T lymphocytes. For subsequent analyses, naı̈ve T lymphocytes are defined as those simultaneously expressing CD62L (L-selectin Leu8) and CD45RA surface antigens. In all of the dot plots divided into 4 quadrants by lines defining positive from negative labeling by the indicated antibody, the numbers in those quadrants refer to the percent of the cells analyzed in that plot that fall within the indicated quadrant. In the top boxed panel a naı̈ve T-lymphocyte subset is defined in the lefthand dot plot by the R1 gate. When naı̈ve T cells in this R1 gate are further analyzed for expression of the transduced mCD24 gene product (MUCD24 on the vertical axis) in the righthand dot plot of the top boxed panel, almost all such cells are shown to be mCD24⁺. The FSC on the horizontal axis of this dot plot refers to forward scatter, a rough measure of cell size, and this parameter is used here merely to allow the presentation of the data in a dot-plot format. The converse analysis is shown in 3 dot plots contained within the bottom boxed panel of this figure. The lefthand dot plot in the bottom panel defines analysis gates containing mCD24⁺ T lymphocytes (R4) or mCD24⁻ T lymphocytes (R3). As indicated by the arrows pointing from R4 or R3, cells contained within either of these gates were further analyzed to delineate naı̈ve T cells from memory T-cell subsets.