The Role of Post-traumatic Inhibition of the Innate and Adaptive Immune System in the Development of Infectious Complications in Severely Injured Patients

Patients admitted to the Intensive Care Unit after severe injury are prone to suffer from infectious complications and even sepsis. Despite tremendous efforts the etiology of this increased susceptibility to infectious pathogens is incompletely understood. Clinical signs and symptoms as well as current diagnostic clinical tests (WBC, CRP, cytokines, interleukines) lack sensitivity or specificity for adequate prediction of the development of infectious complications or sepsis. Neutrophil granulocytes, cells of the innate immune system, play an important role in the defence against invading bacterial pathogens and are crucial in preventing fulminant infections. For successful eradication of a bacterium neutrophils need to exert specific functions: chemotaxis, migration, phagocytosis, degranulation and production of radical oxygen species. Much research has focused on the effect of trauma on neutrophil's individual capacities to kill bacteria with conflicting interpretations as a result. For adequate determination of the neutrophil's capacity to eradicate bacteria from tissue of trauma patients we developed novel in-vitro assays in which neutrophils are tested for all of these functions combined. This assay allows us to identify dysfunctional neutrophils adequately. The main focus of this study is the determination of the functionality of aberrant neutrophils circulating in the peripheral blood of severly injured following trauma.