[Interactions between the platelets and the vessel wall. Part 2: physiopathology (author's transl)].

The role of the blood platelets in the aetiogenesis of arterial lesions has been underlined in recent years by studies of platelet elastase and above all the mitogenic factor of smooth muscle cells. A truly thrombogenic theory of atherosclerosis can now be envisaged. In the context of arterial thromboses, it is interaction between the damaged vessel wall, the lesion most often being atherosclerosis, and blood platelets which gives rise to the thrombus. In certain conditions such as diabetes abnormalities in the interaction between platelets and vessel walls may favour the development of vascular lesions and thromboses. With regard to venous thrombosis, the participation of the vessel and/or platelets is less clear. However, recently described platelet procoagulant activities could activate coagulation mechanisms. Knowledge of diseases of primary haemostasis has benefited from studies of platelet-vessel interaction. Whilst the spontaneous haemorrhagic syndrome of major thrombocytopaenia remains mysterious, platelet membrane molecular abnormalities in thrombopathies such as Bernard Soulier syndrome or thrombasthenia offer an explanation for their mechanisms. By their interaction with the vessel, platelets finally participate in mechanisms of inflammation, immunological conflicts, disseminated intravascular coagulation and metastatic dissemination.