CD8A and Parkinson disease: When studying the effect of CD8+ and CD4+ T cell involvement in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse models of PD, a notable decrease in dopaminergic cell death was observed in Cd4−/− mice compared to WT littermates and Cd8a−/− mice [310].