CD4 and Parkinson disease: In line with the results from our time-course RNA expression data, the determination of peripheral CD4+ T cell subtype composition verified an increased prevalence of Th17 cells (IL-17+) within PD samples (HC: Median 3.4%, range: 2.5–3.9%; PD: Median 6.5%, range: 4.8–9.8%; p = 0.0168) (Fig. 8E).