The tPA organelle lacks endogenous VWF, P-selectin, and CD63. (A-C) Representative examples of individual HUVECs labeled with a specific antibody to tPA (green and top panels of grayscale inserts) and VWF (A), P-selectin (B), or CD63 (C) (red and bottom panel of grayscale inserts). (D-F) EGFP fluorescence (green and top panels of grayscale inserts) in cells expressing tPA-EGFP (24 hours after Nucleofection) and counter-labeled with specific antibodies to VWF (D), P-selectin (E), or CD63 (F) (red and bottom panel of grayscale inserts).