Patients

Severely injured patients ≥ 18 years of age with an expected ICU stay of ≥ 48 h were included between November 2018 and July 2019. Patients were excluded if they recently (< 3 months before hospital admission) used immunosuppressive medication, had an immunosuppressive disorder, or were admitted to ICU because of isolated neurologic injury. Blood was drawn in sodium heparine tubes as soon as possible after trauma (< 12 h), after 3 days, 6 days, 10 days, and 15 days. Control blood samples were provided by anonymous, sex- and age-matched, healthy volunteers. Data concerning patient characteristics, trauma mechanism, injuries, resuscitation, and treatment were obtained from the electronic medical record system. The injury severity score (ISS) [33] based on the abbreviated injury scale 2008 (AIS08) [34] was obtained from the National Trauma Registration database that collects data of all trauma patients admitted to the emergency department [35, 36].