ARG1 and Parkinson disease: Ruganzu et al. (2021) showed that overexpressed TREM2 rescued cognitive deficits, decreased Aβ plaques deposition, reduced synaptic and neuronal loss, ameliorated neuroinflammation, promoted M2 polarization as well as reduced M1 inflammatory responses through JAK/STAT/SOCS signaling pathway. TREM2 p.R47H mutation is also a risk factor for PD (Rayaprolu et al., 2013), and TREM2 level was upregulated in the midbrain of PD mice (Zhang Y. et al., 2018). TREM2 improves the phagocytosis ability of microglia, increases M2 marker Arg-1 and suppresses neuroinflammation in PD (Zhang Y. et al., 2018).