TREM2 and primary central nervous system vasculitis: In addition, higher sTREM2 levels were observed in PACNS patients with poor outcomes, which is considered to be because of the weakening of the microglia functions of tissue repair, phagocytosis of dying cells, and control local inflammation, after shedding of TREM2, leading to damaging the functional impairment of the repaired nerves repair (25).