CD33 and Alzheimer disease: Research indicates a link between CD33 overexpression in microglia and reduced beta-amyloid (Aβ) clearance, with APPSwe/PS1rE9 mouse studies showing that CD33 knockout decreases Aβ42 levels and plaque burden.2 This suggests that CD33 overexpression hinders microglial Aβ clearance in Alzheimer’s disease.