Furthermore, higher levels of inflammatory cytokines are also found in the blood (the major pathway for immune cell circulation throughout the body) of PD patients, including IL-1β [110,111,112,113,114], IL-6 [110,112,115], TNF-α [112,116,117,118], and IFN-γ [117,118,119]. Here, IL1B is linked to Parkinson disease.