Table 1.

Canonical human NK cell checkpoints.

Receptor	CD	Effect	Other cell types	Ligand	Tolerancea	Induced/Constitutive
KIR-L	CD158	Inh	T, Tγδ, Tm	HLA- I	Yes	C
CD94/NKG2A	CD159a	Inh	T CD8+, Tγδ	HLA-E	Yes	C
ILT2	CD85j	Inh	T, B, Tm	HLA-A, B, C, HLA- G UL18	?	C
KLRG-1	-	Inh	ILC2, T	Cadherins	Yesb	C
LAIR-1	CD305	Inh	T, B, myeloid	Collagen	Yesb	C
NKRP1A	CD161	Inh	T, NKT, ILC	LLT1	?	C
Fc?RIII	CD16	Act	T, myeloid	IgG-Fc	Yes	C
KIR-S	CD158	Act	T, Tγδ, Tm	HLA-I	Yes	C
NKp30	CD337	Act	ILC2, T, Tγδ c	B7H6, BAG6/BAT3	Yes	C
NKp44	CD336	Act	ILC3, myeloid	MLL5 Nidogen-1 HLA-DP	?	I
NKp46	CD335	Act	-	Properdin, HA, HN	Yes	C
NKp65	-	Act	-	KACL	?	C
NKp80	-	Act	T CD8+, Tγδ	AICL	?	C
NKG2D	CD314	Act	T CD8+, Tγδ	MICA/B, ULBPs	Yes	C
CD94/NKG2C CD94/NKG2E	CD159c CD159e	Act	T CD8+, Tγδ	HLA-E	Yes	C
2B4	CD244	Act/Inhc	T, Tγδ, granulocyte	CD48	Yes	C
DNAM-1	CD226	Act	T, B, granulocyte	CD112 (Nectin-2), CD155 (PVR)	No	C
41BB	CD137	Act	T, myeloid, endothelial, tumor	CD137L	No	I
ICOS	CD278	Act	T	ICOS-L B7RP-1	No	I
OX40	CD134	Act	T, NKT granulocyte	OX40-L (CD252)	No	I

HA, Hemagglutinin; HN, Hemaglutinin-Neuraminidase; LFA, Lymphocyte function-associated antigen 1; MICA/B, Major histocompatibility complex (MHC) class I chain-related protein A/B; MLL5, Mixed lineage leukemia 5; Tm, Memory T cell; PVR, Poliovirus receptor; ULBP, UL16-binding protein; C, constitutive; I, induced.

^aRegulation of human NK cell education and/or tolerance.

^bRole in NK cell tolerance is controversial.

^c2B4 is an activating receptor in human mature NK cells but an inhibitory receptor in mouse NK cells, human NK cell precursors during NK cell differentiation and in X-linked lymphoproliferative disease (XLP) patients.

? No reported function on NK cell tolerance.