Microglial activation begins early and persists throughout the course of PD.209 In 1988, reactive microglia were first observed in the substantia nigra (SN) of postmortem brain tissue from PD patients.210 Other microglial activation markers, such as pro-inflammatory enzymes like iNOS and COX211,212 and phagocytosis-associated marker CD68,213 were also upregulated in PD patients. Here, CD68 is linked to Parkinson disease.