ARG1 and Alzheimer disease: In mouse models of AD, a neurodegenerative disease characterized by deposition of amyloid beta peptide (Aβ), an early toxic event in AD pathogenesis, ARG1+ microglia mediate Aβ plaque clearance, while ARG1 overexpression in the CNS reduces inflammation and hippocampal atrophy and ameliorates disease [129, 130].