DC–T-cell encounters measured in real time. (A) Representative sequence of a time-lapse video recording of a T cell (red) binding to a DC (green), obtained by confocal microscopy with excitation of Dil (red) at 568 nm and CMFDA (green) at 488 nm; m indicates minute. (B,C) Time dependence of the separation of centers of cells in individually monitored DC–T-cell pairs; the sequence in panel A is represented by the pertinent segment of the black line in panel C. (B) DC–T-cell encounters that resulted in separation of cells. (C) DC–T-cell encounters that ended in the formation of a stable DC–T-cell complex.