The cluster of differentiation (CD) system is commonly used as cell markers in immunophenotyping. Different kinds of cells in the immune system can be identified through the surface CD molecules 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. Cluster of differentiation 14 (CD14) is a member of the CD system. It takes its name from its inclusion in the CD molecule surface marker proteins. CD14 exists in two forms: a form anchored into the membrane or a soluble form. CD14 was found expressed in macrophages, neutrophil granulocyte and dendritic cells. The major function is to serve as a co-receptor (along with TLR4 and MD-2) for the bacterial lipopolysaccharide (LPS) and other pathogen-associated molecular patterns.
Signaling lymphocyte activation molecule (SLAM), is a self-ligand glycoprotein which exists not only found on the surface of activated and memory T cells, but also on the surface of activated B cells, dendritic cells, and macrophages. SLAM consists of a extracellular domain (ECD) with two Ig-like domains,transmembrane segment, and cytoplasmic domain with three immunoreceptor tyrosine switch motifs (ITSM). SLAM is thought to play an important role in adhesion between T cells and APCs and has been shown to act as a coreceptor in TCR-dependent responses. SLAM, together with CD46, is one of the two receptors for measles virus. SLAM is a cell surface receptor that, like the B cell receptor, CD40, and CD95, can transmit positive or negative signals. SLAM can associate with the SH2-containing inositol phosphatase (SHIP), the SH2-containing protein tyrosine phosphatase (SHP-2), and the adaptor protein SH2 domain protein 1A. It’s upregulated on activated B cells and CD4+ and CD8+ T cells, but downregulated on Th2 polarized cells. Also, it can Inhibits antigen receptor-mediated production of IFN-gamma, but not IL-2, in CD4-/CD8- T-cells
CD155, commonly known as PVR (poliovirus receptor) and Necl-5 (nectin-like molecule-5), is a type I transmembrane single-span glycoprotein, and belongs to the nectins and nectin-like (Necl) subfamily. CD155 was originally identified based on its ability to mediate the cell attachment and entry of poliovirus (PV), an etiologic agent of the central nervous system disease poliomyelitis. The normal cellular function is in the establishment of intercellular adherens junctions between epithelial cells. CD155 may assist in an efficient humoral immune response generated within the intestinal immune system. It has been demonstrated that CD155 can be recognized and bond by DNAM-1 and CD96 which promote the adhension, migration and NK-cell killing, and thus efficiently prime cell-mediated tumor-specific immunity.
The cluster of differentiation (CD) system is commonly used as cell markers in immunophenotyping. Different kinds of cells in the immune system can be identified through the surface CD molecules 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. CD157, also known as ADP-ribosyl cyclase 2, is an ectoenzyme sharing several characteristics with ADP-ribosyl cyclase CD38. CD157 was originally identified as a bone marrow stromal cell molecule (BST-1) with a glycosylphosphatidylinositol (GPI) anchor to bind to the cell surface. CD157 is prevalently expressed by cells of the myeloid lineage. CD157 could act as a receptor with signal transduction capability. Further, it regulates calcium homeostasis and promotes polarization in neutrophils and mediates superoxide (O2−) production in the human U937 myeloid line.
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. CD157, also known as ADP-ribosyl cyclase 2, is an ectoenzyme sharing several characteristics with ADP-ribosyl cyclase CD38. CD157 was originally identified as a bone marrow stromal cell molecule (BST-1) with a glycosylphosphatidylinositol (GPI) anchor to bind to the cell surface. CD157 is prevalently expressed by cells of the myeloid lineage. CD157 could act as a receptor with signal transduction capability. Further, it regulates calcium homeostasis and promotes polarization in neutrophils and mediates superoxide (O2−) production in the human U937 myeloid line.
NKG2, also known as NKG2A(CD159A), is a member of the killer cell lectin-like receptor family. This family is a group of transmembrane proteins preferentially expressed in NK cells. Members of this fmaily are characterized by the type II membrane orientation and the presence of a C-type lectin domain. NKG2 contains 1 C-type lectin domain and forms a complex with another family member, KLRD1/CD94. It is expressed only in NK-cells, but not in T-cells or B-cells. It has been shown that NKG2 represents a family of related cDNA clones, designated NKG2A, NKG2B, NKG2C, and NKG2D, which encode type 2 integral membrane proteins (extracellular C-terminus) containing a C-type lectin domain. Natural killer (NK) cells are lymphocytes that can mediate lysis of certain tumor cells and virus-infected cells without previous activation. They can also regulate specific humoral and cell-mediated immunity. NKG2 functions as a receptor for the recognition of MHC class I HLA-E molecules by NK cells and some cytotoxic T-cells.
CD160 antigen is a cell membrane protein which contains one Ig-likeV-type (immunoglobulin-like) domain. CD160 is a GPI-anchored lymphocyte surface receptor in which expression is mostly restricted to the highly cytotoxic CD56(dim) CD16(+) peripheral blood NK subset. CD160 is a receptor showing broad specificity for both classical and non-classical MHC class I molecules. CD160 is expressed in spleen, peripheral blood, and smal lintestine. Expression of CD160 is restricted to functional NK and T cytotoxic lymphocytes. CD160 acts as a co-activator receptor for CD3-induced proliferation of CD4+ CD160+ T cells isolated from inflammatory skin lesions. Activated NK lymphocytes release a soluble form of CD160 that functionally impairs the MHC-I-specific cytotoxic CD8(+) T lymphocyte responsiveness.
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