MAPT and Alzheimer disease: TREM2 can participate in neuroinflammation and play a role in AD by mediating the activation and phagocytosis of microglia.[35] Trem-2 is expressed in microglia in the brain, and its extracellular domain is cleaved by proteases and secreted out of the cells, allowing it to be detected in the cerebrospinal fluid.[36] At present, it is found that the expression level of STREM-2 in the cerebrospinal fluid of AD patients is significantly higher than that of healthy people, and the change trend is consistent with that of tau, and there is an obvious positive correlation.[37]