CD16b FCγRIIIB(Fc fragment of IgG, low affinity IIIb receptor), FCRIIIB
Molecule TypeAntigen ExpressionMolecular Weight
Min / Max
Non-lineage Restricted Molecule
GPI anchor
NK Cell
Macrophage
Mast Cell
Neutrophil
Granulocyte
Eosinophil
Thymocyte
50 / 50
60 / 60

Expression
CD16b is expressed on the transmembrane form in humans on NK cells, macrophages and mast cells, while the GPI-anchored form is expressed on neutrophils and can be induced in eosinophils by IFN-γ.  In the mouse no GPI-anchored form of CD16b has been identified and the transmembrane form is expressed on macrophages, NK cells, neutrophils, myeloid precursors and the majority of early CD4-CD8-TCR- fetal thymocytes.

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

CD16b is GPI-anchored glycoprotein.  It contains an extracellular domain which contains 2 Ig-like-C2-type domains but lacks a transmembrane domain and cytoplasmic domain. 

MOLECULAR MASS
Cell Type Unreduced Reduced
50 kDa-60 kDa

POST-TRANSCRIPTIONAL MODIFICATION: No information.

POST-TRANSLATIONAL MODIFICATION: No information.



Ligands
LIGANDS AND MOLECULES ASSOCIATED WITH CD16b

The transmembrane form is non-covalently associated with the FceRI g chain or the TCR z chain. CD16b on mast cells is also associated with the b chain of the FceRI.

 

Function
CD16b is a low affinity receptor and binds the constant region of IgG1 and IgG3.   In contrast to CD16a, the GPI-anchored form on neutrophils binds to ligands but is unable to induce any intrinsic signaling or functional effect but is capable of inducing antibody-dependent cellular cytotoxicity (ADCC) or erythrocytes and phagocytosis by neutrophils.  Targeted disruption of the mouse FceRI common to CD16b and FceRI results in immunocompromised mice.

BIOCHEMICAL ACTIVITY: No information.

DISEASE RELEVANCE AND FUNCTION OF CD16b IN INTACT ANIMAL

CD16b is expressed on human peripheral blood eosinophils which increases in allergic conditions.  CD16b is a marker in leukemia and HIV.  It is used to purify bone marrow and germinal subsets.  CD16b alleles can be used as risk markers for systemic lupus erythematosus (SLE).  This disease is characterized by the presence of circulating immune complexes and a susceptibility to bacterial infections.



Comments

MOLECULAR INTERACTIONS-
PROTEINS AND DNA ELEMENTS WHICH REGULATE TRANSCRIPTION OF CD16b: No information.

SUBSTRATES: No information.

ENZYMES WHICH MODIFY CD16b: No information.


Database accession numbers
AnimalPIRSWISSPROTEMGBL/GENBANK
 
HumanEntrezgene 2215O75015
Antibodies

Revised June 25, 2008


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