Figure 3. Beneficial and detrimental roles for macrophages and neutrophils in CNS injury.

Macrophages and neutrophils have been described to promote both beneficial and detrimental outcomes following CNS injury. Whether these cells orchestrate CNS repair or exacerbate tissue damage following CNS trauma depends on the specific factors that are generated. Beneficial roles for macrophages (top left) in the CNS include their ability to clear cell debris and produce growth factors and other protective molecules including BDNF, GDNF and IL-10. Detrimental roles for macrophages (top right) include production of glutamate and through contact-mediated axon dieback. Both macrophages and neutrophils beneficially produce the atypical growth factor oncomodulin and clear pathogens in non-sterile injuries (left), and detrimentally produce the free radical nitric oxide (right). Neutrophils additionally secrete the enzyme elastase, which was shown to be detrimental following injury (right).