Summary
Since the role of leukocytes found present in thrombi and haemo-static plugs is not
clearly understood, we have investigated the interaction between leukocytes and growing
thrombi in a human ex vivo model of arterial thrombogenesis. At a wall shear rate
characteristic of moderately stenosed arteries (2600 s–1), granulocytes selectively accumulated at the luminal surface of platelet thrombi.
The leukocyte adhesion seemed independent of fibrin formation and was clearly correlated
to thrombus growth and platelet activation. In contrast, flow cytometry revealed that
the expression of adhesion molecules (CD11a, CD11b, CD11c, CD3, CD14, CD62L, HLA-DR
and binding of fibrinogen) on the surface of circulating leukocytes passing the thrombi
was, on short term conditions (15 min), independent of thrombus growth. The adhered
granulocytes probably play a pivotal role in limiting the size of the evolving thrombi,
as suggested by our electron micrographs of the arterial thrombi showing lysed and
phagocytosed platelets. Thus, granulocytes might play an active role in the acute/semiacute
phase of local thromboregulation.
