TREM2 and colitis: In human, the TREM2 pathway is expressed in various tissue macrophages, such as the microglia of the central nervous system, and increasing evidence suggests that TREM2 is involved in neuroinflammatory responses and neurodegenerative diseases like Alzheimer and Parkinson (71, 72) and contributes to mucosal inflammation in the digestive tract during the development of colitis in mice (73).