Platelet-associated Inflammation in Severe Sepsis

Sepsis represents a serious public health issue characterized by a complex inflammatory response. In addition to their hemostatic role, platelets display inflammatory functions by secreting a variety of immunomodulatory factors and interacting with circulating immune cells. The investigators postulate that, in severe sepsis, platelets become activated and release amounts of different soluble inflammatory molecules that contribute to sepsis-associated inflammation. First, the investigators propose to assess whether severe sepsis impairs the ability of platelets to release soluble CD40L (sCD40L), an powerful platelet-derived immunomodulatory molecule, in ICU patients with S. aureus documented infection, ICU patients with documented infection involving other bacterial species, compared to ICU patients with inflammation of noninfectious origin and healthy blood donors. Then, the investigators wish to assess whether the bacterial species affects the release of platelet sCD40L and by an extensive screening of platelet soluble factors, the investigators propose to set up profiles of inflammatory molecules associated with the type of infection. Finally, the investigators will analyze platelets' activation state and their association with circulating immune, according to the type of infection. Therefore, this project is expected to assess to which extent the platelet inflammatory function is super-activated in severe sepsis and to identify new platelet-related biomarkers of sepsis.