Engulfment of apoptotic or necrotic ECs by HMEC-1 cells and HUVECs. (A) Exposure of HMEC-1 cells to necrotic HMEC-1 cells for 3 hours resulted in engulfment of labeled cell fragments. (B) After 6 hours of coincubation phagocytosed particles appear in the lysosomes around the nucleus (arrows). (C) CM-Dil labeled HMEC-1 cells were incubated with CMFDA-labeled apoptotic HMEC-1 cells. After 1 hour apoptotic cells were engulfed by HUVECs (white arrowheads). The yellow arrow indicates an apoptotic cell that binds to the surface of a HUVEC. (D) CM-Dil stained HUVECs were exposed for 2.5 hours to apoptotic HMEC-1 cells. The micrograph shows a confocal image of a cell engulfing an apoptotic (green) cell. A cross-section of the whole cell is shown in the micrograph at the bottom. Bars represent 50 μm (A-C) or 20 μm (D).