Suppressed migration of α₄-R/A^GFFKR T lymphocytes on VCAM-1 and MAdCAM-1 substrates. Lateral migration of T lymphocytes on VCAM-1 and MAdCAM-1 in response to chemokine CXCL12 was studied using live-cell imaging. (A) Representative confocal and DIC images of migrating cells stained for actin (Alexa 488) and α₄ integrin (Cy3) are shown. (B) Morphologic analysis showing the strong presence of α₄ integrin–rich trailing edge “tethers” (arrows) in α₄-R/A^GFFKR cells, but not WT cells, migrating on VCAM-1 and MAdCAM-1 (not shown). (C) The number of tethers per cell. Data are expressed as the mean plus or minus SEM of at least 20 cells from randomly selected fields. *P < .01 versus WT.