In particular, the hippocampus and frontal cortex of the brains with AD exhibit significantly reduced levels of CX3C chemokine ligand 1 (CX3CL1) and CX3CR1 compared to controls, indicating that signaling through the CX3CL1/CX3CR1 pathway is compromised in AD [80]. Here, CX3CL1 is linked to Alzheimer disease.