Blood transfusion is an indispensable therapy for which there is currently no substitute. Transfusion of blood products is in the great majority of cases very well tolerated but it can be at the origin of serious adverse reactions (SARs), notably of inflammatory reactions. This depends on the factors related to the products themselves and/or to the recipients, their genetic predisposition and clinical condition. Platelet concentrates (PCs) are the main source of inflammatory and/or allergic manifestations. This is due, in part, to the ability of platelets to secrete a multitude of molecules with inflammatory activity. In addition, the collection, processing and storage conditions induce stress on cells, which can activate platelets and thus induce the production of inflammatory products in PCs. The purpose of this work is to identify the molecules involved in inflammatory manifestations. sCD40L was identified as being involved in SARs after PCs transfusion, but not systematically. Also, the inflammatory component of these reactions is multifactorial. In addition, we evaluated the inflammatory potential of PCs on the vascular endothelium. Differences in endothelial cell activation, in an in vitro model, were observed when they were in the presence of PC supernatants involved in SARs. This thesis work continues the effort undertaken by our research team to predict the occurrence of SARs and to clarify the mechanisms that influence transfusional platelet physiopathology; a corollary of this work is to optimize the production and conditioning process of PCs transfused in order to reduce these inflammatory reactions.