CX3CR1 and Parkinson disease: In the acute PD model, knockout of CCR2 can inhibit the entry of early monocytes into the CNS, while knockout of C-X3-C motif chemokine receptor 1 (CX3CR1) in MG or overexpression of CCl2 in astrocytes in MG induce more monocytes to enter the CNS and aggravate the impairment of dopaminergic neurons.