CHI3L1 and Alzheimer disease: While several studies have identified the presence of M2 markers, such as TGF-β and IL-10, in the brain of Alzheimer's disease (AD) animal models, as well as an increase in the expression of M2 genes AG1 (arginase 1) and CHI3L1/CHI3L2 (chitinase 3-like 1/2) in AD patients [15], inflammation in the human AD brain has also been associated with upregulation of IL-6, IL-1β, and TNF-α, all markers of the M1 state, in the vicinity of amyloid deposits [16, 17].