In the cerebrospinal fluid of AD patients, glial fibrillary acidic protein (GFAP)-positive astrocytes are found to be related to elevated Aβ levels, whereas YKL-40, also known as chitinase-3-like protein 1 (CHI3L1)-positive astrocytes, are found in association with elevated Tau levels. This evidence concerns the gene CHI3L1 and Alzheimer disease.