Figure 5: Fluorescence-activated cell sorting (FACS) analysis of CCR5 expression at the surface of the parental PM1 cells [P(PM1)] and cells that expressed EGS TK1 (TK1), C2 (C2), and C1 (C1). Quantitation was carried out by labeling the cells with a PE-conjugated anti-CCR5 antibody. The results are expressed in percent of fluorescence compared with the parental PM1 cells, which serve as the control. The values are the means from triplicate experiments. The standard deviation is indicated by the error bars.