CX3CL1 and Parkinson disease: Although, the absence of CX3CR1, per se, does not result in microglia activation or neurodegeneration, the impairment of the CX3CL1/CX3CR1 signaling by deletion of the Cx3cr1 gene results in increased neurotoxicity in mouse models of LPS-induced systemic inflammation, Parkinson’s disease (PD), AD, and ALS (Cardona et al., 2006; Lee et al., 2010; Cho et al., 2011).