Sommer et al. had shown that Th17 cells obtained from PD patients induced neuronal death in the midbrain, indicating the neurotoxic effect of Th17 cells in PD [67], and this neurotoxicity of Th17 cells was driven by T cell-derived IL-17, upregulated IL-17R, downstream Nuclear factor-kappa-B (NFκB) activation, as well as lymphocyte function-associated antigen-1/intercellular adhesion molecule-1(LFA-1/ICAM-1) system [67, 119]. This evidence concerns the gene IL17A and Parkinson disease.