Following of Myeloid-derived Suppressor Cells (MDSC) in Severe Sepsis: What Relationship With Systemic Inflammatory Syndrome?

Inclusion Criteria: * Patient ≥18 years old * Patient with two criteria of systemic inflammatory response syndrome and one of the four following criteria within 24 hours of hospitalization in ICU: * Lactate \>4 mmol/L * PaO2 / FiO2 \<200 in the presence of lung disease as infectious source * Vasopressor: adrenaline or noradrenaline ≥0.25 µg/kg/min for at least 6 hours to maintain a systolic blood pressure ≥90 mmHg or mean arterial pressure ≥65 mmHg * Thrombocytopenia linked to sepsis with platelet count \<100,000 / ml or a decrease ≤50% within 48 hours Exclusion Criteria: * Pregnancy * progressive solid cancer * HIV infection * History of blood or inflammatory disease * long-term immunosuppressive treatment * Prior episode of Sepsis in the previous month * Chronic Dialysis Patient * Patient under guardianship * Patient not affiliated with a social security system