IL6 and Parkinson disease: Elevated serum IL-6 and CD40L have been reported in many neurological diseases, including multiple sclerosis, Alzheimer’s disease, Parkinson’s disease, and neuromyelitis optica spectrum disorder (Desideri et al., 2008; Giunta et al., 2010; Rothaug et al., 2016; Du et al., 2020; Fujihara et al., 2020).