IL17A and Parkinson disease: In the present review we systematically retrieved and critically evaluated available evidence regarding the contribution of Th17 cells and IL-17 to neuroinflammation and neurodegeneration in PD, to provide a state-of-the-art compendium which will help identifying the future directions that research in this field may take to assess the possible benefits of targeting Th17/IL-17 to develop novel therapeuticts for PD patients.