To further evaluate the sensitization of monocytes in PD patients, monocytes were stimulated by LPS; following 24 h stimulation, the mRNA levels of IL1b, IL6 and TNF and the protein levels of pro-inflammatory cytokines, especially IL-1β, IL-6, TNF-α and IL-2 became significantly higher in monocytes of PD patients than healthy controls (Fig. 1B, C), indicating the hyperactivation of monocytes in PD patients. Here, IL2 is linked to Parkinson disease.