TREM2 and early-onset autosomal dominant Alzheimer disease: TREM2 activation inhibits microglia-mediated neuroinflammation and apoptotic neuron phagocytosis29,30 and has been reported to be expressed in neurological diseases, such as traumatic brain injury, cerebral ischaemia, amyotrophic lateral sclerosis, Alzheimer's disease (AD) and PD31,32.