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CD52 is a small GPI (glycosylphosphatidylinositol) anchored glycoprotein which is tied to the cell surface with a GPI linkage. CD52 induces immune suppression by complement-meditated cell lysis. Moreover, CD52 is expressed on lymphocytes, eosinophils, monocytes-derived dendritic cells, monocytes, as well as neutrophils, however not on the stem cells from which these lymphocytes were derived. Furthermore, CD52 is a significant goal for therapeutic interventions intended for leukocyte depletion in post-transplant immunosuppression & hematological malignancies.

CD81 antigen isoform 1, also known as CD81, is part of the tetraspanin family. CD81 interacts directly with immunoglobulin superfamily member 8 (IGSF8, CD316) and CD36. In B cells, CD81 is part of a complex with CD21, CD19 and Leu13. Furthermore, this complex decreases the threshold for B cell activation through B cell receptors by linking Ag specific recognition and CD21 mediator recognition. While on T cells CD81 connects with CD4 and CD8 and provides a costimulatory signal with CD3.

CD21 is expressed strongly on mature B cells, follicular dentritic cells and weakly on immature thymocytes and T lymphocytes. In B-cell ontogeny, CD21 appears after the pre-B-stage, is maintained during peripheral B-cell development and is lost upon terminal differentiation into plasma cells. CD21 expression is also gradually lost after stimulation of B cells in vitro. CD21 functions as receptor for C3d, C3dg and iC3b Complement components, for EBV and for IFNalpha. CD21 binds to CD23 and associates with CD19, CD81 and Leu13 to form a large signal-transduction complex involved in B cell activation.

CD37 belongs to the transmembrane 4 superfamily, otherwise known as the tetraspanin family. Most of its members are cell-surface proteins which are distinguished by the presence of 4 hydrophobic domains. These proteins mediate signal transduction events which have a role in the regulation of cell development, activation, growth and motility. CD37 protein is a cell surface glycoprotein which is known to form complexes with integrins and other transmembrane 4 superfamily proteins. CD37 may also havea role in T-cell-B-cell interactions.

CD1D, also known as antigen-presenting glycoprotein CD1d, is a transmembrane glycoprotein which belongs to the CD1 family of glycolipid antigen-presenting MHC-like molecules. CD1d-presented lipid antigens activate a special class of T cells, familiar as natural killer T (NKT) cells, during the interaction with the T-cell receptor present on NKT membranes. Once activated, NKT cells rapidly produce Th1 &Th2 cytokines, usually represented by interleukin 4 production.

CD4, a single chain transmembrane glycoprotein, is found on a T cell subset (helper/inducer) representing 45% of peripheral blood lymphocytes. It is also present on 80% of thymocytes and at a lower level on monocytes. It is involved in recognition of antigen presented along with MHC class II by APCs. It serves as receptor for HIV. Antibody to CD4 recognizes T-helper cells required for recognition of class II antigens. It reacts with ~60% of peripheral blood E rosette-positive (E+) cells while showing negligible reactivity with E- cells, monocytes, granulocytes, EBV-transformed B cell lines, and mouse splenocytes.

Basal Cell Adhesion Molecule (BCAM) which is a product of alternate splicing of the Lutheran blood group molecule is a part of the immunoglobulin superfamily. BCAM contains five extracellular immunoglobulin domains, a single transmembrane domain, and a short C-terminal cytoplasmic tail. BCAM protein is upregulated following malignant transformation of some cell types in vivo and in vitro. Furthermore, BCAM interacts with integrin in sickle red cells, and participates in vasoocclusive episodes.

CD44 is a cell-surface glycoprotein that plays a role in cell-cell interactions, cell adhesion and migration. CD44 is a receptor for hyaluronic acid and also interacts with other ligands, such as osteopontin, collagens, and matrix metalloproteinases. CD44 participates in a wide variety of cellular functions such as lymphocyte activation, recirculation and homing, hematopoiesis, and tumor metastasis.

Cytotoxic and Regulatory T Cell Molecule, also known as CRTAM belongs to the immunoglobulin superfamily which complies with the structural characteristics of the JAM family and is phylogenetically more closely related to nectin-like proteins. CRTAM is implicated in epithelial cell adhesion. Furthermore, CRTAM interacts with CADM1 as well as promotes natural killer (NK) cell cytotoxicity.

CD160 antigen (CD160) is a human natural killer (NK)-cell-activating receptor which is also expressed on T-cell subsets. CD160 is a tumor-specific antigen known to mediate cellular activation signals in CLL, and is a novel target for therapeutic manipulation and monitoring of minimal residual disease. CD160 was identified as a T cell coinhibitory molecule which interacts with the herpesvirus entry mediator (HVEM) on antigen-presenting cells to deliver a potent inhibitory signal to CD4(+) T cells. CD160 expression is strongly associated with peripheral blood NK cells and CD8 T lymphocytes with cytolytic effector activity. CD160 is expressed on all intestinal intraepithelial lymphocytes. CD160 has a broad specificity for binding to both classical and nonclassical MHC class I molecules.

CD72 antigen is a member of the type II integral membrane glycoproteins which includes other related cell surface moleculaes such as the asialoglycoprotein receptors, CD23 and the Kupffer cell recpeotr. The exposure of B cells to CD72 antibodies activates a variety of signalling pathways and can induce MHC class II expression and B cell proliferation. CD72 antigen is expressed on all cells of B cell lineage with the exception of plasma cells and weakly on human tissue macrophages.

CD2 which is also known as E-rosette receptor, T11 and lymphocytefunction antigen-2 (LFA-2) is expressed on T cells, thymocytes, and subset of natural killer cells. Human CD2 functions as the receptor for sheep erythrocytes, human CD58 (LFA-3), and CD15s (Sialyl Lewis X). p56lck, p59fyn, CD3eta and CD3epsilon are tyrosine-phosphorylated after CD2 stimulation. CD2 plays a role in T cell activation, T- or NK-cell-mediated cytolysis, apoptosis in activated peripheral T cells, and regulation of T cell anergy.

CD9 which is found on the surface of exosomes is a cell surface glycoprotein which interacts with integrins and various transmembrane superfamily proteins. CD9 is involved in platelet activation and aggregation and also regulates paranodal junction formation. CD9 takes part in cell adhesion and migration and also promotes muscle cell fusion. CD9 is necessary for the egg-sperm fusion during mammalian fertilization.

CD163 is an acute phase-regulated receptor which participates in the removal and endocytosis of hemoglobin/haptoglobin complexes by macrophages and thus keeps tissues from free hemoglobin-mediated oxidative damage. Furthermore, CD163 partakes in the uptake and recycling of iron, through endocytosis of hemoglobin/haptoglobin and ensuing breakdown of heme. In addition, CD163 binds hemoglobin/haptoglobin complexes in a calcium-dependent and pH-dependent way. CD163 demonstrates greater affinity for complexes of hemoglobin and multimeric haptoglobin of HP-1F phenotype than for complexes of hemoglobin and dimeric haptoglobin of HP-1S phenotype. Moreover, CD163 stimulates a cascade of intracellular signals which involves tyrosine kinase-dependent calcium recruitment, inositol triphosphate formation and secretion of IL-6 & CSF-1.

CD300A belongs to the CD300 family and contains 1 Ig-like V-type (immunoglobulin-like) domain. The protein is expressed not only by natural killer (NK) cells but also by T-cell subsets, B-cells, dendritic cells, mast cells, granulocytes and monocytes. CD300A is inhibitory receptor which may contribute to the down-regulation of cytolytic activity in natural killer (NK) cells, and to the down-regulation of mast cell degranulation.

CD164 Sialomucin-Like 2, also known as CD164L2 is amember of the CD164 family.

CD9 which is found on the surface of exosomes is a cell surface glycoprotein which is interacts with integrins and various transmembrane superfamily proteins. CD9 is involved in platelet activation and aggregation and also regulates paranodal junction formation. CD9 takes part in cell adhesion and migration and also promotes muscle cell fusion. CD9 is necessary for the egg-sperm fusion during mammalian fertilization.

CD3-epsilonpolypeptide (CD3E) along with CD3-gamma, -delta and -zeta, and the T-cell receptor alpha/beta and gamma/delta heterodimers, creates the T-cell receptor-CD3 complex. This complex has an imperative role in coupling antigen recognition to a number of intracellular signal-transduction pathways. The genes encoding the epsilon, gamma delta polypeptides are found in the same cluster on chromosome 11. The epsilon polypeptide plays a vital role in T-cell development. CD3E gene defects cause immunodeficiency. CD3E is also linked to a susceptibility to type I diabetes in women.

MS4A1 is an activated-glycosylated phosphoprotein expressed on the surface of all B-cells. The expression begins at the pro-B phase and until maturity the concentration increases in order to allow optimal B-cell immune response, specifically against T-independent antigens. MS4A1 takes part in the microenvironmental interactions of B cells and also in the regulation of B-cell activation and proliferation. MS4A1 also plays a role as a calcium channel in the cell membrane.

CD19, also known as B-Lymphocyte Surface Antigen B4, belongs to the Ig superfamily which is expressed on the surface of all B-lymphoid cells with the exception of terminally differentiated plasma cells. CD19 is involved as a signal-transducing receptor in the control of differentiation as well as proliferation. CD19 is as an adaptor protein which drafts cytoplasmic signaling proteins to the membrane and operates within the CD19/CD21 complex to decrease the threshold for B cell receptor signaling pathways. CD19 is present on all B cells, and therefore is a biomarker for lymphoma diagnosis, B lymphocyte development and can be used as a target for leukemia immunotherapies.

CD1a is a transmembrane glycoproteins, which is structurally related to the major histocompatibility complex (MHC) proteins and form heterodimers with beta-2-microglobulin. CD1a mediates the presentation of primarily lipid and glycolipid antigens of self or microbial origin to T cells. The human genome contains five CD1 family genes organized in a cluster on chromosome 1. The CD1 family members are thought to differ in their cellular localization and specificity for particular lipid ligands. The protein encoded by this gene localizes to the plasma membrane and to recycling vesicles of the early endocytic system. Alternatively spliced transcript variants have been observed, but their biological validity has not been determined.

CD4, a single chain transmembrane glycoprotein, is found on a T cell subset (helper/inducer) representing 45% of peripheral blood lymphocytes. It is also present on 80% of thymocytes and at a lower level on monocytes. It is involved in recognition of antigen presented along with MHC class II by APCs. It serves as receptor for HIV. Antibody to CD4 recognizes T-helper cells required for recognition of class II antigens. It reacts with ~60% of peripheral blood E rosette-positive (E+) cells while showing negligible reactivity with E- cells, monocytes, granulocytes, EBV-transformed B cell lines, and mouse splenocytes.

CD43 is a key sialoglycoprotein located in the surface of T lymphocytes, monocytes, granulocytes, thymocytes and some B lymphocytes. CD43 is a part of a physiologic ligand-receptor complex which participates in T-cell activation. Throughout T-cell activation, CD43 is actively taken out from the T-cell-APC (antigen-presenting cell) contact site, signifying CD43 has a negative regulatory role in adaptive immune response.

CD79A is a signal-transducing part of the B-cell receptor which plays various roles in B cell development and function. CD79A is also needed for BCR surface expression and for efficient differentiation of pro-B and pre-B-cells. CD79A plays an important role in the tumor promoting effects of myeloid cells, and is a novel target for cancer therapy.