The effects of injury on the adaptive immune response

For more than thirty years it has been apparent that serious injury in humans and experimental animals is associated with a decrease in immune functions dependent upon T cells, the principal cells involved in initiating adaptive immune responses. This review focuses on more recent evidence that T helper cell function is altered after serious injury with loss of T helper 1 function and cytokine production and with preservation of T helper 2 function and an increased production of T helper 2 cytokines. Emphasis is placed on the importance of interactions between the innate and adaptive immune systems in the perturbed immune responses seen following injury. Immunomodulatory strategies are mentioned that have had success in animal models in ameliorating the diminished resistance to infection commonly seen after major traumatic or thermal injury. Finally, it is emphasized that immunomodulatory treatments that are successful in preventing infection may be contraindicated once infection is manifest.