A nonredundant role for ICAM-1 for intraluminal T-cell crawling, but not transendothelial migration or perivascular trapping. (A) Representative micrographs of directly egressing (left panels) or crawling (right panels) T cells transmigrating through HEVs. Time in minutes and seconds; scale bar = 10 μm. (B left panel) Total path length of crawling T cells in WT or ICAM-1^−/− PLNs. (Right panel) Perivascular dwelling of transmigrated T cells in WT or ICAM-1^−/− PLNs. (C top panels) Mean track velocity (right) and meandering index (MI; left) of crawling intraluminal T cells, as well as perivascular and parenchymal T cells in WT PLNs. The low velocity and MI are indicative of the perivascular slowing down of transmigrated T cells. (Bottom panels) Mean track velocity (right) and MI (left) of intraluminal perivascular and parenchymal T cells in ICAM-1^−/− PLNs. (D) Immunofluorescent image of transmigrated T cells (red, arrows) around a MECA-79⁺ HEV (pink) 15 minutes after transfer. Transferred cells are in close proximity to the laminin⁺ basement membrane (blue). Scale bar = 10 μm. (E) Total path length (top panel) and MI (bottom panel) of naive T cells migrating on 2D surfaces coated with CCL21 + ICAM-1/Fc or ICAM-2/Fc. Tracks were recorded for 20 minutes. One experiment of 3 is shown. n.s. indicates not significant. *P < .05; **P < .001; ***P < .0001.