ABSTRACT

INTRODUCTION Specific adhesion processes direct and modulate all the dynamic interactions among vascular cells. Nowhere else in the adult organism do the cells have the capacity to change their interactions so rapidly and completely as in the blood vessels, and nowhere else are defective interactions so immediately life-threatening. For example, during normal hemostasis, free-flowing platelets have to adhere rapidly at the site o f damage and then to each other to form an effective platelet plug; otherwise, blood loss cannot be contained and hemorrhage and death follow. Just as dangerous as lack o f platelet adhesion is excessive platelet aggregation. This results in thrombosis, which may lead to stroke or heart attack. Similarly, deficiency in leukocyte adhesion leads to life-threatening infections, while excessive leukocyte adhesion-for example, during reperfusion after a period o f ischemia-may cause tissue destruction.