Accumulation of neutrophils over 20 minutes. Shown is the number of rolling (A) and adhering (B) neutrophils on collagen (type I) immobilized platelets. Over the first 20 minutes, approximately 25% to 50% of the rolling cells adhered at 2 dyn/cm². Pretreatment of platelet monolayers with the anti–P-selectin antibody (G1; 2 μg/mL) prevented any neutrophil-platelet interactions. An isotype-matched control antibody did not affect neutrophil rolling or adhesion (data not shown).