[Platelets cytokines and their effects on platelet transfusion]

Platelets have long been confined to haemostasis only. However, novel functions for platelets have been identified recently. Those non-nucleated cells indeed participate to inflammation and also they produce and release numerous factors with known immunomodulatory functions. Among those factors are cytokines and chemokines and the like, such as soluble CD40-Ligand (CD154), which are key molecules in that they bridge innate and adaptative immunity; sCD40L is active on T cells, B cells, monocytes and macrophages, dendritic cells and endothelial cells lining the blood vessels. This means that when a platelet concentrate is transfused to a recipient, a huge amount of cytokines and chemokines is also infused. In this state of the art review, we will present arguments on the role of platelet secretory products in modulating cellular parameters of immunity, and--very likely--in altering functions of those immune cells upon encounters while infusing platelets in blood recipients. We aimed at summarizing data that have been made available on the issue of cytokines/chemokines released by stored platelets prior to delivery. We will focus on the suspected role of the CD40/CD40L tandem in postplatelet transfusion reactions or incidents. We will present recent data on the role of pathogen inactivators on the docking and/or release of cytokines/chemokines by platelets.