Fig. 5. (A) Schematic representation of the live cell internalization experiment. In dendritic cells stained with anti-DC-SIGN F(ab) (red) and bathed in FITC-BSA as an endocytosis marker (green), a confocal slice containing the medial lamellar membrane was observed. Endocytosis results in a colocalized (yellow) signal. (B) DIC image of the cell under observation. (C) A single frame showing the leading edge of a dendritic cell (yellow line) and a region of interest containing a DC-SIGN cluster that exhibits internalization. (D) A montage of selected frames limited to the region of interest defined in (C) showing the internalization of a DC-SIGN cluster. The arrow shows a surface DC-SIGN cluster before internalization is evident. The arrowhead in a subsequent frame shows the appearance of internalization activity conincident with the surface DC-SIGN cluster.