Interleukin-6 in the injured patient marker of injury or mediator of inflammation?

Objective The effects of interleukin (IL)-6 in the injured patient are examined in an attempt to clarify the potential pathophysiologic role of IL-6 in the response to injury. Summary Background Data Interleukin-6 is an integral cytokine mediator of the acute phase response to injury and infection. However, prolonged and excessive elevations of circulating IL-6 levels in patients after trauma, burns, and elective surgery have been associated with complications and mortality. The mechanistic role of IL-6 in mediating these effects is unclear. Methods A review of current literature is performed to summarize the origins, mechanisms of action, and biologic effects of IL-6 and to characterize the IL-6 response to injury. Results Interleukin-6 is a multifunctional cytokine expressed by a variety of cells after a multitude of stimuli, under complex regulatory control mechanisms. The IL-6 response to injury is uniquely consistent and related to the magnitude of the insult. Moreover, the early postinjury IL-6 response correlates with complications as well as mortality. Conclusions Interleukin-6 appears to play an active role in the postinjury immune response, making it an attractive therapeutic target in attempts to control hyperinflammatory provoked organ injury.