Video.

Three time-lapse videos of cell-cell interactions by timepoint: A) week 0; B) week 6; C) week 26. CD8+ T cells interact with target cells. The green-stained target cells are visualized as white. Effector cells are not highlighted. Arrowheads indicate effector - target cell interactions in sipuleucel-T–treated subjects demonstrating antigen specificity and antitumor activity. The arrow tips indicate the contact point of the target and effector cells of interest. Cell interaction and killing at room temperature were captured using a Leica CRT6500 confocal microscope with LASAF software (Leica Microsystems, Buffalo Grove, IL). The final products were 41-second videos where the sipuleucel-T–stimulated CD8+ T cells were tracked from the time they come in close contact with the green-stained target cells. For purposes of presentation, the videos have been shortened to fit in the file size limitations. Time-lapse recording was performed using the confocal microscope set up as follows: the “XYT” scanning of acquisition mode was activated; 10X objective was set with digital zoom factor at 6; the XY field was set at the largest size format (2048 x 2048 pixels) with a recording speed at 400 Hz; and the time field was set for a duration of 8 hours. After acquisition, images were analyzed, processed, and recorded as time-lapse video sequences using Adobe Premier Pro CC 2018 at a speed of 30 frames per second.