CHI3L1 and Alzheimer disease: Another possibility could be that the altered neuroinflammatory response [21, 24, 193] and proinflammatory mediator levels (such as chitinase-3-like protein 1, and several cytokines, such as TNF-alpha, interleukin-1 receptor antagonist, and complement component C1q and 3) in the CSF of patients with AD [195–196] may be caused by abnormal microglial function [197].