One possibility could be due to the leakage of RANTES from the inflammatory reaction region in the CNS, since the sustained neuroinflammation-induced vicious cycle may facilitate the neuronal damage as in PD progression, in which a host of proinflammatory factors such as IL-6, TNF-α, and chemokines was overexpressed in the specific site in the brain and these factors could leak through blood-brain barriers, thus causing an elevated RANTES level in the peripheral blood. The gene discussed is CCL5; the disease is Parkinson disease.