To further understand the involvement of the immune system in PD, T cell infiltration in the substantia nigra pars compacta of human post-mortem brain tissue was evaluated on patients featuring Lewy Bodies disease (only α-synuclein clumps deposition, which is considered to be the pre-symptomatic stages of PD), in patients with established PD and age-matched healthy controls (Galiano-Landeira et al. 2020). This evidence concerns the gene SNCA and Parkinson disease.