Table 1. Key Table.

Phagocytic Receptors Identified as AD Risk Genes, and Mutations Associated with AD That Impact on Phagocytosis^a

Receptor	Species	Model/studies	Mutation	Alterations in phagocytosis	Refs
TREM2	Human	Postmortem AD brains	R47H mutation	Reduced recruitment and phagocytosis of Aβ plaques	[52]
TREM2	Human	NHD patient-derived microglia	T66M and W50C mutation	Reduced phagocytosis of apoptotic cells	[53]
TREM2	Mouse	5×FAD and APP/PS1	R47H mutation	Reduced recruitment and phagocytosis of Aβ plaques	[50,51]
TREM2	Mouse	5×FAD and APP/PS1	TREM2 knockout	Reduced recruitment and phagocytosis of Aβ plaques	[46]
CR1	Human	Patient CSF	C3b/C4 increased repeatsb	Decreased Aβ clearance in CSF	[57]
CD33	Human	Patient-derived monocytes	Full-length with risk allele (C)c	Decreased uptake of dextran and Aβ	[62]
CD33	Human	Post-mortem AD brains	Full-length with protective allele (T)b	Decreased insoluble Aβ in the brain – indicator of enhanced Aβ uptake and clearance	[64]
CD33	Human	Human monocytic cell lines	CD33 knockout	Increased phagocytosis of dextran, polystyrene beads, myelin, and Aβ	[65]
CD33	Mouse	APP/PS1	CD33 knockout	Decreased insoluble Aβ and reduced Aβ plaque burden – indicator of enhanced Aβ uptake and clearance	[64]

^aAbbreviations: CSF, cerebrospinal fluid; NHD, Nasu–Hakola disease.

^bVariant associated with decreased expression.

^cVariant associated with increased expression.