CX3CL1 and Alzheimer disease: Interestingly, some biomarkers have altered relationships when it comes to their levels vs. controls depending on the disease, perhaps reflecting disease-specific neurodegenerative mechanisms; for example CX3CL1 is increased in the CSF and blood of people with both MS (Kastenbauer et al., 2003) and AD (Bivona et al., 2022) vs. controls, but decreased in PD (Hatcher-Martin et al., 2020), whereas it seems unaffected in non-AD dementia (Bivona et al., 2022), although in all the above mentioned conditions neurodegeneration is apparent.