CD4 and Parkinson disease: In vitro analyses showed about threefold increase in Th17 cells frequency, a phenotype favored by DRD3-signalling, in ex vivo activated CD4+ T cells obtained from PD patients, indicating that DRD3-signalling in lymphocytes plays a relevant role favoring the development of PD, and selective DRD3-antagonism in CD4+ T lymphocytes may exert a therapeutic effect in PD [124].