CD85k ILT3 (immunoglobulin-like transcript-3), LIR5 (leukocyte immunoglobulin-like receptor-5),  LILRB4 (leukocyte immunoglobulin-like receptor, subfamily B with TM and ITIM domains, member 4), HM18
Molecule TypeAntigen ExpressionMolecular Weight
Min / Max
Lineage Restricted Molecule
Type 1 glycoprotein
Myeloid Cell
Monocyte
Macrophage
Dendritic Cell
Endothelial Cell
60 / 60

Expression
CD85k is expressed on myeloid cells, monocytes, endothelial cells, macrophages and dendritic cells.  CD85k is expressed on Lin-HLA-DR+CD11c- and Lin-HLA-DR+CD11c+ fresh blood cells but there is only a small subpopulation that lacks CD85k expression.  Monocyte derived dendritic cells, MoDC, express CD85k molecules which appear to be upregulated following activation with activating agents. 

Structure
MOLECULAR FAMILY NAME: Belongs to the immunoglobulin supergene family.

CD85k is a single-pass type-1 glycoprotein.  It contains a signal peptide, a 608 aa extracellular domain which contains 2 Ig-like C2-type domains, a 21 aa transmembrane and long 168 aa cytoplasmic tail containing 3 ITIM sequences.  The ILT/LIR family is within the Ig gene superfamily.

MOLECULAR MASS

POST-TRANSCRIPTIONAL MODIFICATION

Alterantive splicing yields 2 different isoforms.

POST-TRANSLATIONAL MODIFICATION: No information.


Ligands
LIGANDS AND MOLECULES ASSOCIATED WITH CD85k: No information

Function
CD85k is a putative inhibitory receptor with an unknown ligand.  CD85k induces an inhibitory signal.  Cytoplasmic ITIMs recruit and activate protein tyrosine phosphatases SHP-1 and/or SHP-2 which act as inhibitory effector molecules.  On ligation, the molecules are internalized.  CD85k is involved in the suppression of NK-mediated cytotoxicity and is an inhibitory receptor for MHC class I molecules.  Antigen presentation cells expressing CD85k and CD85d appear to be crucial to the generation of CD8+ suppressor T cells and CD4+ regulatory T cells.  CD85k appears to be a useful marker for the purification of plasmacytoid monocytes.

BIOCHEMICAL ACTIVITY: No information.

DISEASE RELEVANCE AND FUNCTION OF CD85k IN INTACT ANIMAL: No information.


Comments
Previously, the ILT family was clustered together as CD85.  Recently subclassifications have been given to individual members listed as CD85a - CD85m.  Ig-like transcripts (ITLs) and leukocyte Ig-like transcripts (LIRs) are structurally and functionally related transmembrane glycoproteins.  The receptors are divided into 2 groups of inhibitory and activating receptors according to the nature of their transmembrane and cytoplasmic regions.  Receptors with a long cytoplasmic tail, CD85a (ILT5/LIR3), CD85c (LIR8), CD85d (ILT4/LIR2), CD85j (ILT2/LIR1) and CD85k (ILT3/LIR5), contain one or more intracytoplasmic ITIMs which recruit and activate protein tyrosine phosphates SHP-1 and/or SHP-2.  Receptors with a short tail, CD85b (ILT8), CD85f (ILT11), CD85g (ILT7), CD85h (ILT1/LIR7) and CD85i (LIR6a) lack ITIMs and contain a positively charged aa residue, arginine or lysine, in their transmembrane domain which is necessary for association with ITIM-containing polypeptides like FcRg chain.  CD85l (ILT9) and CD85m (ILT10) bind the FcRg chain.  Phosphorylated ITAMs recruit the protein tyrosine kinases Syk and ZAP70.  One exception to these transmembrane receptors is CD85e (ILT6/LIR4) which has no transmembrane or cytoplasmic domains and is probably soluble.                     

MOLECULAR INTERACTIONS -
PROTEINS AND DNA ELEMENTS WHICH REGULATE TRANSCRIPTION OF CD85k: No information.

SUBSTRATES: No information.

ENZYMES WHICH MODIFY CD85k: No information.


Database accession numbers
AnimalPIRSWISSPROTEMGBL/GENBANK
 
HumanEntrezgene11006Q8NHJ6
Antibodies

Revised June 25, 2008


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