CCR2 and Parkinson disease: Unexpectedly, in the current study, CCR2 knockout did not result in significantly decreased IMs in RBP-JcKO PD mice and contributed less to the increased numbers of TH+ DA neurons in RBP-JcKO PD mice, suggesting that Notch signaling blockade in myeloid cells alleviated DA neurodegeneration independent of CCR2+ monocyte recruitment.