CD18 ITGβ2 (integrin β2, complement component 3 receptor 3 and 4), β2 integrin chain, CD11a β subunit, CD11b β subunit, CD11c β subunit
Molecule TypeAntigen ExpressionMolecular Weight
Min / Max
Non-lineage Restricted Molecule
Type 1 glycoprotein
Leukocyte
95 / 95
120 / 120

Expression
CD18 is expressed on all leukocytes.  It is the β2 integrin chain of the CD11a, CD11b, CD11c heterodimers. 

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

CD18 is a single-pass type-1 747 aa glycoprotein.  It contains a 678 aa extracellular domain which contains an I-domain, 6 potential N-linked glycosylation sites and a heavily internally cross-linked with 28 potential disulphide links, a 23 aa transmembrane domain and a 46 aa cytoplasmic domain.  The N-terminus of CD18 is blocked.

MOLECULAR MASS
Cell Type Unreduced Reduced
Leukocytes >120 kDa 95 kDa

POST-TRANSCRIPTIONAL MODIFICATION: No information.

POST-TRANSLATIONAL MODIFICATION: No information.

Ligands
LIGANDS AND MOLECULES ASSOCIATED WITH CD18

CD18 is associated with and see CD11a, CD11b and CD11c. 



Function
It is the β2 integrin chain of the CD11a, CD11b, CD11c heterodimers.   CD18 is expressed on an a chain and a b chain.  CD18 combines with the a L chains CD11a to form the integrin LFA-1 and with the CD11b a chain to form the integrin Mac-1.  The integrins are known to participate in cell adhesion and cell-surface mediating signaling in leukocytes, the hematopoietic system.  CD18 is involved in cell-cell and cell-matrix interactions being a member of a family of cell surface proteins.  CD18 may be important in the regulation of ligand binding activities of various CD11/CD18 complexes.  It interacts noncavalently with CD11a, b, c and d to form the adhesion molecule complexes LFA-1, Mac-1, p150, p95 and 2Db2 respectively.  CD18 has been shown to interact with several cytoskeletal proteins including a-actinin and filamin ABP-280, and the cytoplasmic regulatory molecule cytoadhesin-1.  There are also a number of antibodies that promote the CD11/CD18 antigens to a high affinity binding to ligands.  Leukocyte adhesion deficiency (LAD) results from defects in the CD18 gene, leading to diminished expression of all CD18-containing integrins.  The deficiency is very heterogeneous with varying degrees of clinical severity.  The gene defect has been observed in humans, cattle, and dogs. 

BIOCHEMICAL ACTIVITY: No information.

DISEASE RELEVANCE AND FUNCTION OF CD18 IN INTACT ANIMAL

LAD-1 is caused by a lesion in the CD18 gene coding for the common b2 subunit causing patients to suffer from recurrent infections.  General importance in inflammatory responses has been tested in CD18 "knockout" mice.

Comments
MOLECULAR EXPRESSION -
PROTEINS AND DNA ELEMENTS WHICH REGULATE TRANSCRIPTION OF CD18: No information.

SUBSTRATES: No information.

ENZYMES WHICH MODIFY CD18: No information.


Database accession numbers
AnimalPIRSWISSPROTEMGBL/GENBANK
 
HumanEntrezgene3689P05107
MouseS04847P11835X14951
Antibodies
6.7   View Reactivity
7 e4   View Reactivity
BAQ30A   View Reactivity
BAT75A   View Reactivity
CA1.4E9   View Reactivity
CLB-LFA-1/1   View Reactivity
CO.1C6E3   View Reactivity
H20A   View Reactivity
HUH82A   View Reactivity
L13/64   View Reactivity
MHM23   View Reactivity
YFC118.3   View Reactivity

Revised June 25, 2008


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