Figure 4. Phagocytosis of ARPE-19 as a function of incubation time ARPE-19 were cultured for two weeks to confluence on a human Bruch’s membrane explant harvested from a 14-year-old human donor. Average fluorescein isothiocyanate-labeled rod-outer- segments (FITC-ROS) intensity per cell increased linearly with incubation time. Each data point is the average of three experiments with duplicate wells. Background autofluorescence was subtracted. Error bar represents standard deviation.