Some previous studies reported that CX3CL1 levels were decreased in brains and cerebrospinal fluid (CSF) of AD patients and in brains of AD model mice [126,127,128,129], while other studies reported that CX3CL1 was increased more in CSF or plasma of MCI and AD patients than in healthy people [130,131]. This evidence concerns the gene CX3CL1 and Alzheimer disease.