Defective KC-induced leukocyte firm adhesion and diapedesis in β-arr 2^−/− mice. (A-C) Rolling (A), firm adhesion (B), and emigration (C) of WT and β-arr 2^−/− leukocytes examined by intravital microscopy of cremaster muscles superfused with 6.25 nM KC. The sequential steps of leukocyte extravasation were analyzed in cremasteric venules at a defined shear rate (WT venule shear rate = 1095.5 ± 118.9 s⁻¹, β-arr 2^−/− venule shear rate = 1101.8 ± 26.4 s⁻¹, supplemental Table 1). (D-E) WT and β-arr 2^−/− leukocytes were examined for the ability to firmly adhere to either low (D) shear rate venules (WT venule shear rate = 756.2 ± 186.6 s⁻¹, β-arr 2^−/− venule shear rate = 716.1 ± 63 s⁻¹) or high (E) shear rate venules (WT venule shear rate = 1506.6 ± 138.6 s⁻¹, β-arr 2^−/− venule shear rate = 1516.1 ± 7.1 s⁻¹) by intravital microscopy of cremaster muscles superfused with 6.25 nM KC. Data are expressed as mean ± SEM of either 5 (A-C) or 3 (D-E) mice per group (*P < .05, **P < .01, ***P < .001 for β-arr 2^−/− vs WT leukocyte responses at the same experimental time point).