In this study, <i>Il6</i> <sup><i>-/-</i></sup> (knockout), <i>Il6</i> <sup>+/-</sup>, and wild-type mice were utilized to investigate the impact of IL-6 on the pathology of MPTP- or α-Synuclein<sup>A53T</sup>-induced PD mice. This evidence concerns the gene IL6 and Parkinson disease.