CD11c ITGAX (integrin αX),  CR4, leukocyte suface antigen p150,95
Molecule TypeAntigen ExpressionMolecular Weight
Min / Max
Non-lineage Restricted Molecule
Type 1 glycoprotein
Myeloid Cell
Macrophage
NK Cell
T Cell
Lymphoid Cell
Leukemia cell
Monocyte
Granulocyte
B Cell
145 / 145
150 / 150

Expression
CD11c expression is high on monocytes, macrophages and NK cells, moderate on granulocytes, and least on subsets of T and B cells.  The level of expression on granulocytes can vary from low to high.  CD11c is weakly expressed by CD3+ T lymphocytes and CD20+ B lymphocytes.  Expression is low in sheep and rabbits, and moderate in cattle.  The level of expression increases on B cells in B lymphoctotic cattle infected with bovine leukemia virus.  It is also expressed on lymphoid cell lines including hairy cell leukemias.  CD11c is used to detect myeloid cells in tissue studies.


Structure
MOLECULAR FAMILY NAME:  Belongs to the integrin a chain family.

CD11c is a single-pass type-1 a chain 1144 aa glycoprotein.  It contains an 1081 aa extracellular region which contains an I-domain near the N-terminus, 7 tandem repeats that are modeled to resemble a b propeller fold.with 3 putative cation-binding motifs and 10 potential N-glycosylation sites, a 26 aa transmembrane domain and a 29 aa cytoplasmic region.  The I-domain has not yet been crystallized and expressed in an isolated form but has been described to have ligand binding activity.  It is expressed as a non-covalently linked heterodimer with CD18.

MOLECULAR MASS
Cell Type Unreduced Reduced
Leukocytes 145 kDa 150 kDa

POST-TRANSCRIPTIONAL MODIFICATION: No information.

POST-TRANSLATIONAL MODIFICATION

There are 10 potential N-glycosylation sites.

Ligands
CD11c/CD18 binds multiple ligands including the complement fragment iC3b, CD54 (ICAM-1), fibrinogen and bacterial lipopolysaccharide. It has also been reported that CD11c/CD18 binds denatured proteins.

LIGANDS AND MOLECULES ASSOCIATED WITH CD11c
Molecule Comment
iC3b Ligand
Fibrinogen Ligand
(ICAM-1)
(CD23)
LPS/LPB (Cis interactions?)
uPAR(?) (Cis interactions?)

CD11c/CD18 binds similar ligands as CD11b/CD18 although not as well characterized.



Function
CD11/CD18 forms the integrin CD18 (p150,95) which is a type-4 complement receptor receptor CR4.  CD11c functions in the adherence of neutrophils and monocytes to stimulated endothelium and is important in the phagocytosis of complement iC3b coated particles.  CD11c/CD18 has been described to play important roles in cytotoxic T cell killing, and on neutrophil and monocyte adhesion to endothelium, although its ligands in these 2 cases have not been identified.  CD11c has similar functions to CD11b/CD18 with which it cooperates.  The major CD11/CD18 receptor is on tissue macrophages.  An antibody against rabbit CD11c/CD18 has been reported to induce T cell aggregation.  CD11c/CD18 is not expressed on leukocytes of patients with leukocyte adhesion deficiency (LAD).  CD11c mediates cell-to-cell interactions in inflammation.

BIOCHEMICAL ACTIVITY: No information.

DISEASE RELEVANCE AND FUNCTION OF CD11c IN INTACT ANIMAL

Leukocyte adhesion deficiency-type-1 (LAD-1) patients are CD11c-deficient.

Comments
MOLECULAR INTERACTIONS -
PROTEINS AND DNA ELEMENTS WHICH REGULATE TRANSCRIPTION OF CD11c
Molecule Comment
Sp1 and Sp1-like factors
AP-1 family
C/EBP
Oct-2
PU.1

SUBSTRATES: No information.

ENZYMES WHICH MODIFY CD11c: No information.

ADDITIONAL INSIGHTS

CD11c/CD18 mediates leukocyte spreading onto protein-coated surfaces, a function suggestive of a role in cell survival, as has been already proposed for CD11b.

Database accession numbers
AnimalPIRSWISSPROTEMGBL/GENBANK
 
HumanEntrezgene 3687P20702
Antibodies
3/22   View Reactivity
BAQ153A   View Reactivity
BU15   View Reactivity
CA11.6A1   View Reactivity
LT93A   View Reactivity
RT3A   View Reactivity
S-HCL-3   View Reactivity

Revised June 25, 2008


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