In PD patients, CD4+ T cells expressed lower levels of TBX21 and STAT4, which together with STAT1 drive Th1 differentiation [39], as well as of RORC and STAT3, which regulate the differentiation towards the Th17 lineage [40], and higher levels of STAT6 and GATA3, which are master regulators of Th2 development [41, 42]. This evidence concerns the gene STAT3 and Parkinson disease.