IFNG and Parkinson disease: Several studies have reported a range of differential frequencies and characteristics of CD8+ T subsets in PD patients vs controls such as decreased replicative senescence (a marker of normal aging) in total CD8+ T cells [119], a decrease in naive CD8+ T cells [93], an increase in IFN-γ-producing CD8+ T cells [93], an increase in terminally-differentiated effector memory (TEMRA) CD8+ T cells and CD8+ NK T cells (Fig. 1) and a decrease in CD8+FOXP3+ T cells [118], as well as a decrease in IL-10-producing CD8+ Tregs [98].