Leukocyte transmigration is dependent on HS sequestration of chemokines on apical venular endothelium. (A) Number of adherent or (B) emigrated neutrophils, in the MIP-2-superfused cremaster muscle of WT (n = 7), hpa-tg mice (n = 7), or in WT pretreated with heparin (0.5 mg; n = 5). (C) In vivo intravascular binding of MIP-2 (expressed as FITC-MIP-2 intensity/ μm² vessel) 30 minutes after intra-arterial injection of MIP-2 conjugated to FITC in WT and hpa-tg cremasteric venules. *P < .05 compared with time 0 before addition of chemokine. †P < .05 vs WT at the same time period.