Granulocyte- Macrophage Colony-Stimulating Factor Reverses Immunosuppression Acutely Following a Traumatic Brain Injury and Hemorrhage Polytrauma in a Juvenile Male Rat Model

Traumatic brain injury (TBI) is a common cause of morbidity and mortality in children. We have previously shown that TBI with a concurrent extracranial injury reliably leads to post-injury suppression of the innate and adaptive immune systems. In patients with post-injury immune suppression, if immune function could be preserved, this might represent a therapeutic opportunity. As such, we examined, in an animal injury model, whether systemic administration of granulocyte macrophage colony-stimulating factor (GM-CSF) could reverse post-injury immune suppression and whether treatment was associated with neuroinflammation or functional deficit. Prepubescent male rats were injured using a controlled cortical impact model and then subjected to removal of 25% blood volume (TBI/H). Sham animals underwent surgery without injury induction, and the treatment groups were sham and injured animals treated with either saline vehicle or 50 μg/kg GM-CSF. GM-CSF was administered following injury and then daily until sacrifice at post-injury day (PID) 7. Immune function was measured by assessing tumor necrosis factor-α (TNF-α) levels in whole blood and spleen following