CD4 and Parkinson disease: The adaptive immune system has also been implicated in PD pathophysiology, as CD4/CD8 T-cellsinfiltrate the SN of PD patients (McGeer et al., 1987, 1988; Farkas et al., 2000;Brochard et al., 2009) and may contribute to vascular changesduring the disease (Faucheux et al., 1999; Farkas et al.,2000).