RAPL is required for stable adhesion. (A) The adhesion of wild-type and RAPL-deficient T lymphocytes with LS12 cells expressing mouse ICAM-1 under shear flow. Adhesive interactions were measured as in Figure 1. Data represent the mean ± SD of 3 independent experiments. *P < .001, compared with wild-type lymphocytes. (B) Intravital microscopic analysis of wild-type and RAPL-deficient lymphocytes in HEVs. The percentages of transient arrest and stable arrest of adoptively transferred lymphocytes from control and RAPL^−/− mice passing through HEVs in the MLN are shown (left). The y-axis indicates the ratios of the cells, which stopped more than 0.5 seconds, but detached within 10 seconds (transient arrest) or adhered more than 10 seconds (stable arrest) against total cells interacting with the vessel wall. Data represent the mean ± SD of 4 independent experiments. Representative cell interactions with MLN HEVs are shown (right). Image acquisition information is available in the supplemental Methods.