IL17A and Parkinson disease: Regarding the contribution of Th17 cells and IL-17A in Alzheimer’s disease (AD), Parkinson’s disease (PD), and amyotrophic lateral sclerosis (ALS), we systematically retrieved and critically evaluated available literatures, aiming to provide a compendium to clarify the possible benefits of targeting Th17/IL-17 to develop novel treatments for these patients (Fig. 1).