LRRK2 and Parkinson disease: In addition, infiltration and accumulation of peripheral immune cells have been also found in affected brain regions of PD patients [9] The role of mitochondrial impairment and neuroinflammation in PD and reactive oxygen species (ROS) production is further supported by the finding that the PD-associated proteins parkin, PINK1, DJ-1, α-syn, and LRRK2 are involved in mitochondrial functioning and/or contribute to or modulate microglia activation [6].