Activated platelets adherent to an intact endothelial cell monolayer bind flowing neutrophils and enable them to transfer to the endothelial surface

We have investigated the role that platelets may play in promoting adhesion of neutrophils to morphologically intact endothelium. Immortalized human microvascular endothelial cells (HMEC-1) were grown to confluence in a glass capillary (microslide) and incorporated in a flow-based assay that allowed video-microscopic quantitation of adhesive interactions of perfused, isolated neutrophils (wall shear rate 140 s–1). Platelets (with or without stimulation with thrombin) were first sedimented onto the HMEC-1 cells and formed discrete attachments covering