IL6 and Parkinson disease: Indeed, even at early stages of PD, the SNc showed much higher levels of IL-6R expression than that of control SNc (1.09% ± 0.14 % of IL-6R+ staining area per image/total image area in PD versus 0.04% ± 0.02 % in controls; Figure 5, D and E; P < 0.001), supporting the concept that reactive astrocytes producing elevated IL-6 levels and neuronal susceptibility to IL-6 play roles during PD pathogenesis.