[Platelet-mediated regulation of immunity]

Abstract

Platelets, essentially non-nucleated blood cells, are highly reactive components of the circulatory system. They have long been consigned solely to a role in thrombosis and hemostasis. Platelets release platelet-derived microvesicles (PMV), also known as platelet-derived microparticles (PMP). They are important but still under-appreciated mediators of intracellular cross-talk between platelets and other cells and modulate their function. They are formed after stimulation of platelets by an agonist, such as thrombin, collagen, and many others. Platelets can carry biological mediators; they can modulate immune responses and inflammatory events. Microparticles can be released from activated platelets and leukocytes in inflammatory events, but in atherosclerosis they can be released from apoptotic endothelial cells, lymphocytes, and monocytes. The markers of innate immunity expressed by platelets are Toll-like receptors (TLRs). The role of platelets in tumor progression and metastasis has been recognized, but the mechanism of their action remains still unclear.