ADHESION OF LEUKOCYTES TO GROWING ARTERIAL THROMBI

Since the role of leukocytes found present in thrombi and haemostatic plugs is not clearly understood, we have investigated the interaction between leukocytes and growing thrombi in a human ex vivo model of art erial thrombogenesis. At a wall shear rate characteristic of moderatel y stenosed arteries (2600 s(-1)), granulocytes selectively accumulated at the luminal surface of platelet thrombi. The leukocyte adhesion se emed independent of fibrin formation and was clearly correlated to thr ombus growth and platelet activation. In contrast, flow cytometry reve aled that the expression of adhesion molecules (CD11a, CD11b, CD11c, C D3, CD14, CD62L, HLA-DR and binding of fibrinogen) on the surface of c irculating leukocytes passing the thrombi was, on short term condition s (15 min), independent of thrombus growth. The adhered granulocytes p robably play a pivotal role in limiting the size of the evolving throm bi, as suggested by our electron micrographs of the arterial thrombi s howing lysed and phagocytosed platelets. Thus, granulocytes might play an active role in the acute/semiacute phase of local thromboregulatio n.