Cortactin is required for leukocyte rolling, adhesion, and transmigration in vivo. (A–D) The velocity of rolling cells (A), the rolling flux fraction (B), the number of firmly adherent cells (C), and the number of transmigrated cells (D) were investigated by intravital video microscopy and reflected light oblique transillumination microscopy of cremaster muscle venules of Cttn^del/del (KO) and Cttn^WT/WT (WT) mice. Inflammation was induced by intrascrotal injection of 500 ng TNF 3 h before analysis. The results are displayed as mean ± SD of at least 20 vessels from four different animals in each group. ***, P < 0.0005. (E–H) Chimeric mice generated by transplanting bone marrow from WT animals or from cortactin-deficient mice (KO) into lethally irradiated WT mice were analyzed by intravital microscopy of cremaster as for A–D. The velocity of rolling cells (E), the rolling flux fraction (F), the number of firmly adherent cells (G), and the number of transmigrated cells (H) were determined and showed no significant differences between the two types of chimeras. Results were obtained from three mice per group. (I) Leukocyte rolling velocity in venules of TNF-stimulated cremaster was determined as in A and E from Cttn^del/del (KO) and Cttn^WT/WT (WT) mice that had been injected with a combination of anti–LFA-1 and anti–Mac-1 blocking antibodies (30 µg of each per mouse) just before cremaster muscle exteriorization. No-antibody controls are shown in A. Results were determined from four mice per group.