Brain, behavior, and immunity
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Brain Behav. Immun. · Jul 2019
ReviewInfections after a traumatic brain injury: The complex interplay between the immune and neurological systems.
Traumatic brain injury (TBI) is a serious global health issue, being the leading cause of death and disability for individuals under the age of 45, and one of the largest causes of global neurological disability. In addition to the brain injury itself, it is increasingly appreciated that a TBI may also alter the systemic immune response in a way that renders TBI patients more vulnerable to infections in the acute post-injury period. Such infections pose an additional challenge to the patient, increasing rates of mortality and morbidity, and worsening neurological outcomes. ⋯ This review first describes the clinical scenario, posing the question of whether TBI patients are more susceptible to infections such as pneumonia, and if so, why? We then consider how cross-talk between the injured brain and the systemic immune system occurs, and further, how the additional immune challenge of an acquired infection can contribute to ongoing neuroinflammation and neurodegeneration after a TBI. Experimental models combining TBI with infection are discussed, as well as current treatment options available for this double-barreled insult. The aims of this review are to summarize current understanding of the bidirectional relationship between the CNS and the immune system when faced with a mechanical trauma combined with a concomitant infection, and to highlight key outstanding questions that remain in the field.