DRD3 and Parkinson disease: Nevertheless, another plausible explanation for this fact can be that simply, CD4+ T-cells specific for relevant antigens associated to PD [i.e., nitrated α-synuclein; (1, 35)] would acquire inflammatory phenotypes with high DRD3-expression (20) and they would be just infiltrating the site of inflammation (into the SNpc) but not recirculating in the periphery.