In addition, if LRRK2 indeed potentiates α-syn toxicity in PD patients, it may not be solely linked to cell-autonomous mechanisms in DA neurons, but may also result from complex interactions between DA neurons and other LRRK2-expressing cells that surround DA neurons, especially microglial cells, astrocytes, and cells of the immune system, which likely play a role [38,39,40]. Here, LRRK2 is linked to Parkinson disease.