[Leukocytes and vascular lesions]

The participation of leukocytes in the development of vascular disorders has been observed under various circumstances. Leukocyte activation occurs in extracorporeal blood circulation which lead to a pulmonary vascular sequestration and respiratory distress syndrome. Leukocytes could act on vascular components through at least two different pathways by releasing free oxygen radicals and proteases or by producing mediators such as interleukin 1, Tumor necrosis alpha, leukotrienes. Monocytes macrophages are present in the vascular wall at a very early stage of atherosclerosis. A majority of foam cells have been identified as macrophages loaded with lipids. Lymphocytes and monocytes are present in the atherosclerotic plaque. Leukocytes are also observed in the inflammatory lesion of vasculitis and experimentally activated lymphocytes can induce vasculitis. The molecular bases of leukocyte-endothelium interactions have been determined, and imply specialized molecules. Leukocyte Adhesion Molecule (LeucAM) appear to play a crucial role in leukocyte adhesion. On the endothelial cell side, endothelial cell adhesion molecule, intercellular adhesion molecule are receptors for leukocytes adhesion. They have been recently fully characterized. The better knowledge of leukocyte-vascular wall interactions offers new possible target for therapeutic agents.