The Recruitment of Leukocytes and their Interaction with the Vessel Wall: The Role of Interleukin-1 and Tumor Necrosis Factor

The vascular endothelium has long been considered to have very little or no active function in inflammatory reactions and hemostasis. However, it has been recently discovered that endothelial cells can dramatically change their functional competence in response to the mononuclear phagocyte products interleukin-1 (IL-1) and tumor necrosis factor (TNF). IL-1 induces synthesis of prostacyclin, platelet activating factor, thromboplastin and plasminogen activator inhibitor. Both IL-1 and TNF cause leukocyte adhesion to the endothelium. On the other hand endothelial cells can themselves initiate the immune response through synthesis and release of IL-1. TNF, released in tissues may act as a chemoattractant and further promote interaction of leukocytes with the vascular lining. IL-1 and TNF can therefore act as a communications signal between circulating cells and the vessel wall and play an important role in the inflammatory and coagulation disorders.