Effects of CNS Injury-Induced Immunosuppression on Pulmonary Immunity

Patients suffering from stroke, traumatic brain injury, or other forms of central nervous system (CNS) injury have an increased risk of nosocomial infections due to CNS injury-induced immunosuppression (CIDS). Immediately after CNS-injury, the response in the brain is pro-inflammatory; however, subsequently, local and systemic immunity is suppressed due to the compensatory release of immunomodulatory neurotransmitters. CIDS makes patients susceptible to contracting infections, among which pneumonia is very common and often lethal. Ventilator-acquired pneumonia has a mortality of 20–50% and poses a significant risk to vulnerable patients such as stroke survivors. The mechanisms involved in CIDS are not well understood. In this review, we consolidate the evidence for cellular processes underlying the pathogenesis of CIDS, the emerging treatments, and speculate further on the immune elements at play.