CD8A and Parkinson disease: CD4+ T-cell subsets, T-helper 17 (Th17), and regulatory T cells (Treg) play a vital role by limiting α-synuclein-mediated microglial activation and reducing the activity of CD8+ cytotoxic T-cell and natural killer (NK) cells during the neuroinflammation processes in PD (Chen et al., 2018).