Blood Cells - Tissue Functioning and Remodeling in the Circulatory and Ventilatory Systems - page 151

cytoplasmic tails, such as killer cell immunoglobulin-like receptor, 2 domains,
long cytoplasmic tail (KIR2DL1-KIR2DL5) and those with 3 domains (KIR3DL1-
KIR3DL3), inhibit cellular activation, as they recruit PTPn6 phosphatase. Recep-
tors of the KIR and LIR families with short cytoplasmic tails, such as killer
cell immunoglobulin-like receptor, 2 domains, short-cytoplasmic tail (KIR2DS1-
KIR2DS5) and 3 domains (KIR3DS1), transmit activation signals via adaptor
protein tyrosine kinase-binding protein TyroBP 146 Despite their similarities, KIR
and LIR receptors have distinct functional characteristics. Only LILRb1 and
LILRb2 receptors bind to various MHC class-1 ligands.
NK-Cell Stimulatory Receptors
NK cells have numerous stimulatory receptors that cooperate to activate T and
B cells. Killer stimulatory receptors encompass killer cell lectin-like receptors
KLRa8, 147 KLRb1, 148 KLRb1c, 149 KLRf1, 150 and KLRk1; 151 CD2, low-
affinity IgG Fc receptor-3 (CD16), DNAX accessory molecule DNAM1 [or
CD226]; 152 natural cytotoxicity-triggering receptors, such as NCR1, 153 NRC2, 154
NCR3, 155 and NKG2d-DAP10 receptor complex. 156 Receptors used by NK
cells in tumor surveillance include KLRf1, KLRk1, NCR1 to NCR3, DNAM1,
146 A.k.a. DNAX-activation protein DAP12, killer-activating receptor-associated protein
[KARAP], and polycystic lipomembranous osteodysplasia with sclerosing leukoencephalopathy
protein [PLOSL]).
147 A.k.a. lymphocyte antigen Ly49h.
148 A.k.a. NK-cell receptor protein-1 [NKRP1]).
149 A.k.a. natural killer cell-surface protein NK1.1 or NKRP1c and CD161.
150 A.k.a. NKP80.
151 A.k.a. natural killer group-2, member-D [NKG2d] and CD314. Receptor KLRk1 recognizes
several self ligands that are often expressed on cancer cells and causes a protective immune
response. This lectin-like type-2 transmembrane homodimer is expressed by almost all NK and
activated CD8 + T cells, as well as subsets of γδ T and NKT cells, and, in some conditions, CD4 +
T cells. Ligands of the KLRk1 receptor are related to self-proteins that are similar to MHC class-1
molecules, such as MHC class-1 (I) polypeptide-related sequence A (MICa) and B (MICb) as well
as retinoic acid early transcript RAET1 in humans. Normal cells do not express these ligands
at substantial levels. Ligands of the KLRk1 receptor are upregulated in cancerous or stressed
cells [ 279 ].
152 Receptor DNAM1 is constitutively expressed by most NK cells, T lymphocytes, macrophages
and dendritic cells [ 279 ]. Its ligands include nectin-2 (a.k.a. CD112 and poliovirus receptor-related
PVRL2) and nectin-like protein NecL5 (a.k.a. CD155 and poliovirus receptor PVR).
153 A.k.a. natural killer cell P46-related protein NKP46 and CD335.
154 A.k.a. natural killer cell P44-related protein NKP44 and CD336.
155 A.k.a. natural killer cell P30-related protein NKP30 and CD337.
156 Natural cytotoxicity receptors comprise not only NCR1 to NCR3, but also KLRf1 (or NKP80).
In humans, NRC1, NCR3, and KLRf1 are expressed by all NK cells, whereas NRC2 is only
produced by activated NK cells [ 279 ].