The Role of Cxcr4Hi neutrOPhils in InflueNza

Inclusion Criteria: * Patient aged 18 yo or above. * Acute respiratory distress syndrome as defined by the Berlin classification. * Invasive mechanical ventilation for less than 24 hours. * Cause of ARDS: * Influenza infection proven by polymerase chain reaction OR * Bacterial infection (tracheal aspirate with more than 105 CFU/mL and BAL with more than 104 CFU/mL. * Pancreatitis according to the 2013 Working Group IAP/APA Acute Pancreatitis Guidelines. * Peritonitis according to the 2018 SFAR guidelines. * Health insurance. * Written informed consent from legal relative or representative. Exclusion Criteria: * Neutropenia (\< 500/mm3) * Neutrophils qualitative defect. * Patient included in an interventional research assessing an immunomodulatory or antiviral drug. * Acquired ImmunoDeficiency Syndrome. * Contraindication to BAL: * Severe bronshospasm. * Out-of-control shock. * Intracranial high pressure. * Refractory hypoxemia (PaO2/FiO2 \< 60 mmHg). * Legal restriction: prisoners, pregnancy, legal protection.