Open-label, non-randomized, prospective, single center, observational, translational study

The aim of this trial is to study immunosuppression biomarkers in patients hospitalized in intensive care unit in comparison to non-septic patients.

Prevalence of immunosuppression acquired in intensive care unit will be studied and patients most likely to develop nosocomial infection will be early identified

Inclusion Criteria:

• Patient older than 18 years old
• Patient hospitalized in intensive care unit for any reason
• Patient with infection started less than 5 days before admission
• Patient with mechanical ventilation or not
• Patient with arterial catheter for an invasive monitoring of blood pressure
• Patient informed about the study protocol and approved to participate.
• Patients hospitalized for a severe bacterial infection (severe sepsis or septic shock)
• Patient hospitalized for a non-infectious disease

Exclusion Criteria:

• Pregnancy
• Advanced immunosuppression defined by proved humoral or cellular impairment by continuous administration of steroids at any dose since more than one month before hospitalization, transplantation, radiotherapy or chemotherapy in the preceding year
• Initiation of an immunosuppressive therapy as chemotherapy, cyclophosphamide or high dose corticotherapy (>0.5mg/kg/day)

Patient hospitalized in intensive care unit with or without sepsis