Whether this increased percentage of IL-17-producing cells may actually result in increased Th17/IL-17 activity remains however to be established, in view of the limited and conflicting evidence about IL-17 amounts actually secreted by PD patients lymphocytes, which is unchanged according to Kustrimovic et al. (30) and increased based on Sommer et al. (31), both unfortunately performing experiments in cell preparations from very few subjects. Here, IL17A is linked to Parkinson disease.