The FKN/CX3CR1 axis influences the pathophysiology of a variety of PD animal models [123], which are mostly based on the neurodegeneration of substantia nigra (SN) [123] and are related to an early decreased [124] and a late increased expression of CX3CR1 [80] as well as a late increase in FKN [80]. This evidence concerns the gene CX3CL1 and Parkinson disease.