CD200 (OX-2) is a cell surface glycoprotein that imparts immune privileges by suppressing alloimmune and autoimmune responses through its receptor , CD200R , expressed primarily on myeloid cells. Signals delivered through the CD200:CD200R axis have been shown to play an important role in the regulation of anti-tumor immunity , and overexpression of CD200 has been reported in a number of malignancies , including CLL , as well as on cancer stem cells. The role of CD200-CD200R signaling in immune regulation of the central nervous system has become a popular field of research in recent years. Many studies have shown that there is a close correlation between CD200-CD200R , microglia activation , and Parkinson's disease (PD). The ability of CD200 to suppress myeloid cell activation is critical for maintaining normal tissue homeostasis but may also enhance the survival of migratory neoplastic cells. CD200 and CD200R associate via their respective N-terminal Ig-like domains. CD200 has been characterized as an important immunoregulatory molecule , increased expression of which can lead to decreased transplant rejection , autoimmunity , and allergic disease. Elevated CD200 expression has been reported to be associated with poor prognosis in some Human malignancies. Besides , CD200 also plays an important role in prevention of graft rejection , autoimmune diseases and spontaneous abortion.
The cluster of differentiation (CD) system is commonly used as cell markers in immunophynotyping. Different kinds of cells in the immune system can be identified through the surface CD molecules which associating with the immune function of the cell. There are more than 320 CD unique clusters and subclusters have been identified. Some of the CD molecules serve as receptors or ligands important to the cell through initiating a signal cascade which then alter the behavior of the cell. Some CD proteins do not take part in cell signal process but have other functions such as cell adhesion. Cell surface glycoprotein CD200 receptor 1 (CD200R1) is an isoform of CD200 receptors which is expressed on cells of the myeloid lineage. CD200R1 is a receptor for the OX-2 membrane glycoprotein. The receptor-substrate interaction may serve as a myeloid downregulatory signal.
Cell surface glycoprotein CD200 receptor 4, also known as Cell surface glycoprotein OX2 receptor 4, CD200 cell surface glycoprotein receptor-like 4, CD200RLa, and CD200R4, is a single-pass type I membrane protein which belongs to theCD200R family. CD200 (OX2) is a cell surface glycoprotein that interacts with a structurally related receptor (CD200R) expressed mainly on myeloid cells and is involved in regulation of macrophage and mast cell function. In mouse there are up to five genes related to CD200R with conflicting data as to whether they bind CD200. CD200R4 contains oneIg-like C2-type (immunoglobulin-like) domain and one Ig-like V-type (immunoglobulin-like) domain. CD200R4 is highly expressed in monocytes, NK cells and a subset of NKT cells. It is weakly expressed in granulocytes and B cells (at protein level). CD200R4 is also expressed in brain, lung, testis, thymus, intestine and uterus. and in bone marrow derived-macrophage and dendritic cells and mast cells. CD200R4 is involved in the recruitment or surface expression of the TYROBP receptor.
The cluster of differentiation (CD) system is commonly used as cell markers in immunophynotyping. Different kinds of cells in the immune system can be identified through the surface CD molecules which associating with the immune function of the cell. There are more than 320 CD unique clusters and subclusters have been identified. Some of the CD molecules serve as receptors or ligands important to the cell through initiating a signal cascade which then alter the behavior of the cell. Some CD proteins do not take part in cell signal process but have other functions such as cell adhesion. CD209b, also known as SIGNR1, is a C-type lectin receptor. CD209b is present on most regions of mouse brain and found on microglia and dendritic cells but not on neurons or astrocytes. CD209b is implicated in the recently described SIGNR1 complement activation pathway, which operates against capsular polysaccharides in splenic marginal macrophages. CD209b in rat is homologue to SIGNR1 in mouse, both of which are found to mediate the uptake of dextran or CPS14 within the splenic marginal zone.
CD20 is a 297 amino acid (aa) non-glycosylated type III membrane protein that is the founding member of the MS4A tetraspanin protein family. It is expressed on pre-B, naïve and mature B lymphocytes and B-cell lymphomas. CD20 is associated with lipid rafts upon crosslinking, and appears to play a role in regulation of ion influx. The one extracellular segment of 48 aa shows 65% aa sequence identity between human and mouse CD20.
Mouse DNAX accessory molecule-1(DNAM-1) is a type I transmembrane glycoprotein that belongs to the immunoglobulin superfamily. As an activating receptor, it interacts with the ligands CD155 and CD112, and activates natural killer (NK) cells via its immu-noreceptor tyrosine-based activatory motif (ITAM). Mature mouse DNAM-1 has extracellular domain (ECD) that contains two Ig-like C2-set domains, and possesses a cytoplasmic region that contains motifs for binding PDZ domains. DNAM-1 is expressed on several lymphoid and myeloid cell types and interacts with CD155/PVR and Nectin-2/CD112. Ligation of DNAM-1 promotes the activation of NK cells, CD8+ T cells, and mast cells, induces dendritic cell maturation, initiates megakaryocyte and activated platelet adhesion to vascular endothelial cells, and stimulates monocyte extravasation. Conversely, it inhibits the formation of osteoclasts. Platelet-endothelium interactions that are mediated by DNAM-1 enable the metastasis of tumor cells to the lung.
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