ReviewM1 and M2 immune activation in Parkinson's Disease: Foe and ally?

•Inflammation may represent an exciting novel therapeutic mechanism in PD.•M1 macrophage/microglia activation may drive overt cell loss in PD.•M2 macrophage/microglia activation may block M1 activation states and promote healing and repair.

Parkinson's Disease (PD) is a chronic and progressive neurodegenerative disorder of unknown etiology. Autopsy findings, genetics, retrospective studies, and molecular imaging all suggest a role for inflammation in the neurodegenerative process. However, relatively little is understood about the causes and implications of neuroinflammation in PD. Understanding how inflammation arises in PD, in particular the activation state of cells of the innate immune system, may provide an exciting opportunity for novel neuroprotective therapeutics. We analyze the evidence of immune system involvement in PD susceptibility, specifically in the context of M1 and M2 activation states. Tracking and modulating these activation states may provide new insights into both PD etiology and therapeutic strategies.