Small cells, big effects: the role of platelets in transplant vasculopathy.

Platelets are the cellular mediator of thrombosis, but also represent an important part of the immune system. Platelets store numerous pre-formed inflammatory molecules in their granules and produce immune mediators de novo upon stimulation. Activated platelets express adhesion molecules that can interact with endothelial cells and leukocytes both at the site of inflammatory insult and in the circulation. Platelets therefore drive and potentiate vascular inflammation by direct and indirect interactions with both endothelial cells and leukocytes. Platelet activation has been associated with the pathogenesis of inflammatory diseases such as atherosclerosis, arthritis, and cerebral malaria, in addition to transplant vasculopathy. In this review we will discuss immune roles for platelets in the context of transplant vascular inflammation.