Septic shock is still a major cause of death in ICU. Sepsis diagnosis is linked with many clinical, hemodynamic and biological criteria which have a low sensitivity and specificity if they are considered separately. The extensive experimental data which have been published contrast with the hematological data collected by the physician at patient's bedside especially regarding neutrophils and platelets levels. When there is no obvious clinical sign, a biological tool reflecting the patient's immune status could be useful to understand the physiopathology of Sepsis and to predict the progression of the disease in the patient. On the long-term it could also help to define management strategies.

Inclusion Criteria:

• patient older than 18 years old
• Patient with two criteria of systemic inflammatory response syndrome and a progressive infection which is clinically or microbiologically documented

Exclusion Criteria:

• Pregnancy,
• progressive solid cancer,
• HIV infection,
• history of blood or inflammatory disease,
• long-term immunosuppressive treatment

Patient with two criteria of systemic inflammatory response syndrome and a progressive infection which is clinically or microbiologically documented