Then, utilizing CCR2−/− mice to block CCR2+ monocyte recruitment or a PLX5622-formulated diet to deplete microglia, we found that blockade of CCR2+ monocytes contributed negligibly to the attenuated DA neuron degeneration in RBP-JcKO PD mice, whereas microglia depletion enhanced the number of TH+ DA neurons and reduced the inflammatory response in RBP-JcKO PD mice. Here, CCR2 is linked to Parkinson disease.