CD4 and Parkinson disease: Moreover, CD4+ and CD8+ T cells are found in close proximity to dopaminergic neurons in both PD brains (Brochard et al. 2009) and in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated mice (Kurkowska-Jastrzebska et al. 1999; Benner et al. 2008).