Dynamics of T-cell locomotion toward, within, and through endothelial junctions. (A) Four categories of T-cell locomotion patterns are characterized from initial transient arrest sites (letter A) over the apical endothelial surface and junctions (thin black lines). (i) Representative T cell locomotes toward the first junction (green line denotes T-cell trajectories, as analyzed by digital imaging; see “Materials and methods”) and within that junction (blue line) before TEM (red line). (ii, iv) Representative T cells locomote toward the first junction (green line), cross them (blue line), and continue to locomote beyond the first (ii) and the second (iv) junctions (green lines). (iii) Representative T cell locomotes through the first junction (green, blue, green) and is retained within the second junction (blue). (B) T cells analyzed in Figure 2A-B for experiments using 10 ng/mL apical CXCL12, basal CCL5 (as indicated), or both, were tracked and categorized as in panel A. Times and distances from the site of initial transient arrest to the first junction (green lines) were calculated and are displayed. Error bars represent SEM. (C) All T cells analyzed in panel B were tracked and monitored by time and distance from the site of initial transient arrest until the end of the experimental period and were categorized as patterns i, ii, iii, or iv, as described in panel A. Shaded bars correspond to the different locomotion patterns shown in panel A, and checkered bars denote the percentage of TEM within the first and second junctions (i and iii, respectively). Note that T cells in group 2 did not locomote beyond the second junction. Average retention times within the first junction are indicated above the bars for i. Data are presented as percentages of the indicated locomotion pattern from analysis of 30 locomotive cells. *P < .05.