Immune responses to trauma

Balance and disruption of homeostasis between innate and adoptive immune systems

Abstract

Trauma is one of the leading causes of death worldwide. Recent development of surgical and intensive care could resuscitate the patients. Following the acute phase treatment, infectious complications become the most challenging problem in severely injured patients. To prevent and/or treat the infectious complications, we need to know the mechanisms of immune system homeostasis in these patients. Following severe injury, the immune system usually tends toward a pro-inflammatory phenotype and then changes to an anti-inflammatory phenotype. Injured tissue can be endogenous danger signals, and invited pathogens are exogenous danger signals. A combination of the endogenous and the exogenous signals trigger our immune system following injuries. The primed innate immune system is prepared for a rapid and strong antimicrobial immune defense. Injury also augments regulatory T cell activity, which can control the excess inflammatory response for trauma. The inflammatory response and the counter-inflammatory response protect the host in harmony. Disruption of the homeostasis leads the injured host to the worst outcome. We reviewed the mechanisms of the harmony and disruption of immune system homeostasis following injuries.