CD200 OX-2 , MRC
Molecule TypeAntigen ExpressionMolecular Weight
Min / Max
Non-lineage Restricted Molecule
Type 1 glycoprotein
B Cell
Thymocyte
Dendritic Cell
Endothelium
Trophoblast
Neuron
Muscle, Smooth
T Cell
Hematopoietic Cell
Nerve
Keratinocyte
33 / 33

Expression
CD200  is expressed on thymocytes, vascular endothelium, trophoblasts, neurons, smooth muscle and  some dendritic cells.  CD200 is also expressed on activated T and B cells.  It is not expressed on NK cells, monocytes, neutrophils, eosinophils, erythrocytes and platelets.  It is expressed on primitive hematopoietic precursors, on keratinocyte subsets and central and peripheral nerve tissue.           

Structure
MOLECULAR FAMILY NAME: Belongs to the immunoglobulin superfamily.

CD200 is a single-pass type-1 248 aa glycoprotein.  It contains an extracellular domain which contains 1 Ig-like C2-type domain and 1 Ig-like V-type domain and 6 potential N-glycosylation sites, a hydrophobic transmembrane domain and a 19 aa cytoplasmic domain with no known signaling motifs.  The transmembrane sequence is highly conserved between mouse and human, suggesting a functional role for the membrane-spanning sequence.  202 aa are likely to be outside the cell.  The carbohydrate composition of the rat thymus and brain OX2 has been determined.  CD200 was orginally known as a MRC OX-2 antigen, now is MOX2, an antigen identified by the monoclonal antibody MRC OX-2.                      
MOLECULAR MASS
Cell Type Unreduced Reduced
Rat thymocytes 47 kDa
Rat brain 41 kDa
Human activated peeripheral blood mononuclear cells 40 kDa-45 kDa 45 kDa-50 kDa

POST-TRANSCRIPTIONAL MODIFICATION

Alternative splicing yields 2 different isoforms.

POST-TRANSLATIONAL MODIFICATION: No information.



Ligands
LIGANDS AND MOLECULES ASSOCIATED WITH CD200

The recombinant soluble OX2 antigen binds to an unidentified ligand on rodent peritoneal macrophages. 

Function
Binding of CD200 to OX2R on cells of macrophage/monocyte lineage results in the recruitment of SH2-containing inositol phosphatase (SHIP) to OX2R and leads to the downregulation of cellular activity.  Studies of related genes in mouse and rat suggest that the gene encoding CD200 may regulate myeloid activity and deliver controlling inhibitory signals for the macrophage activity in diverse tissues.  It may also provide clues as to the function of other lymphoid/brain proteins such as Thy-1.  It may also costimulate T cell proliferation.

BIOCHEMICAL ACTIVITY

Ig and CD200 share many biochemical similarities with Thy-1.

DISEASE RELEVANCE AND FUNCTION OF CD200 IN INTACT ANIMAL

There is evidence for an immunoregulatory role of CD200 with its counter ligand (OX2L) in the regulation of transplant rejection, fetal loss, autoimmunity and tumor growth.  CD200 knockout mice have a defect in the organization of the mesenteric lymph nodes, increased numbers of macrophages in the spleen and enhanced endogenous macrophage activation.  CD200 null mice display a rapid onset of experimental allergic encephalomyelities (EAE) and have a greater susceptibility to collagen-induced arthritis and autoimmune diseases  compared with wild-type mice.  In a model of nerve damage, microglia from CD200 knockout mice were found to be unusually highly activated.  Several diverse viruses including poxviridae and β- and γ-herpesviridae encode CD200 homologues, some of which have been shown to bind OX2R.  This potentially provides viruses with a means of downregulating myeloid cell activity.


Comments
MOLECULAR INTERACTIONS -
PROTEINS AND DNA ELEMENTS WHICH REGULATE TRANSCRIPTION OF CD200: No information.

SUBSTRATES: No information.

ENZYMES WHICH MODIFY CD200: No information.


Database accession numbers
AnimalPIRSWISSPROTEMGBL/GENBANK
 
HumanEntrezgene 4345P41217
RatA02114P04218X01785
Antibodies
MRC-OX-104   View Reactivity

Revised June 25, 2008


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