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Cluster of Differentiation 244 (CD244/Natural Killer Cell Receptor 2B4) contains 2 Ig-like (immunoglobulin-like) domains. CD244 is a cell surface receptor expressed on natural killer (NK) cells (and some T cells) which mediate non-major histocompatibility complex (MHC) restricted killing. NK-cell and target cells interaction via the CD244 receptor is believed to modulate NK-cell cytolytic activity. CD244 molecules function in eosinophil adhesion and chemotaxis, and have a role in the pathophysiology of allergic rhinitis (AR).

A natural cytotoxicity receptor (NCR) NKp46 has been shown to represent a novel NK cell-specific molecule involved in human NK cell activation. The natural cytotoxicity receptors (NCRs) are a recently characterized family of Ig-like activation receptors that appear to be major triggering receptors in tumor cell recognition. The three known NCRs include NKp46 and NKp30, which are expressed on circulating NKcells, and NKp44, which is expressed only on activating NK cells. NKp46 has been implicated in NK cell-mediated lysis of several autologous tumor cells, pathogen-infected cell lines and mononuclear phagocytes infected with an intracellular bacterium. The Lysis of tumor cells by NK-cells involves recognition by NKp46 of heparan sulfate moieties of membrane heparan sulfate proteoglycans. Furthermore, NKp46 is a surface receptor involved in NK-cell cell death by apoptosis. NKp46 has two extracellular Ig-like domains followed by a ~40 residue stalk region, a type I transmembrane domain, and a short cytoplasmic tail. The extracellular Ig-like domain of NKp46 (22-255aa) is purified by FPLC gel-filtration chromatography, after refolding of the isolated inclusion bodies in a redox buffer. In addition, engagement of the antigen with the monoclonal antibody stimulates intracellular calcium levels and the synthesis of cytokines. CD59 is an NKp46 coreceptor (by physical association) together they activate cytotoxicity of human NK-cells, their engagement results in tyrosine phosphorylation of CD3-zeta chains associated with NKp46. Reduced cell surface expression of NKp46 and other NK-cell receptors is linked to the impaired NK-cell cytolytic function in viremic HIV-1 infection.

NCR2 (NKp44) belongs to the natural cytotoxicity receptor (NCR) family which is expressed on activated human NK cells. NKp44 exhibits a single extracellular Ig-like V domain and a transmembrane portion containing the charged residue (Lysine), possibly involved in the association with KARAP/DAP12 molecules. The gene coding for NKp44 maps on human chromosome 6p21.1.

NKp30 is a natural cytotoxicity receptor (NCR) that may assist NK cells in the lysis of tumor cells. NKp30 interacts with CD3-zeta (CD247), a T-cell receptor. A single nucleotide polymorphism in the 5'' untranslated region of the NKp30 gene has been linked to mild malaria susceptibility.

C-type Lectin Domain Family 1 Member B, also known as CLEC1B. NK-Natural killer cells express multiple calcium-dependent (C-type) lectin-like receptors, for instance CD94 (KLRD1; MIM 602894) and NKG2D (KLRC4; MIM 602893), which interact with major histocompatibility complex class I molecules and either inhibit or else activate cytotoxicity and cytokine secretion. CLEC1B is a C-type lectin-like receptor which is expressed in myeloid cells as well as in NK cells.

Cytotoxicity Triggering Receptor 3 also known as NCR3 is a natural cytotoxicity receptor (NCR) which assists NK cells in the lysis of tumor cells. Moreover, NCR3 interacts with CD3-zeta (CD247), a T-cell receptor. A single nucleotide polymorphism in the 5' untranslated region of NCR3 has been related with mild malaria suceptibility. Three transcript variants encoding various isoforms have been found for this gene.

CD33 is putative adhesion molecule of myelomonocytic-derived cells which mediates sialic-acid dependent binding to cells. CD33 prefers to bind to alpha-2,6-linked sialic acid. The sialic acid recognition site is masked by cis interactions with sialic acids on the same cell surface. In the immune response, CD33 perform as an inhibitory receptor upon ligand induced tyrosine phosphorylation by recruiting cytoplasmic phosphatases through their SH2 domains which block signal transduction through dephosphorylation of signaling molecules. In addition, CD33 induces apoptosis in acute myeloid leukemia.

CD207 (C-type lectin domain family 4 member K) is expressed in Langerhans cells which are immature dendritic cells of the epidermis and mucosa. Moreover, CD207 is expressed in several other dendritic cell types including dermal CD103+ DCs and splenic CD8+ DCs. Langerin is localized in the Birbeck granules, the organelles present in the cytoplasm of Langerhans cells and comprised of superimposed and zippered membranes. CD207 is a C-type lectin with mannose binding specificity, and it has been suggested that mannose binding by the CD207 protein leads to internalization of antigen into Birbeck granules thus providing access to a nonclassical antigen-processing pathway.

C-type lectin domain family 7 member A 1 or CLEC7A is a protein, that in the innate immune system, acts against fungal pathogens. CLEC7A can be found in the immune system response cells such as monocytes, macrophages & neutrophils, or in dendritic and T cells. The protein is enhanced by macrophages by using GM-CSF, IL-4, or IL-13, or diminishes by dexamethasone, IL-10 and LPS.

C-type Lectin Domain Family 4, Member M (CLEC4M) is a type II integral membrane proteinand A pathogen-recognition receptor which takes part in peripheral immune surveillance in liver. CLEC4M mediates the endocytosis of pathogens which than degraded in lysosomal compartments. CLEC4M is a receptor for ICAM3, binding to mannose-like carbohydrates and also recognizes various evolutionarily divergent pathogens with a large impact on public health, including tuberculosis mycobacteria, and viruses which among them are Ebola, hepatitis C,influenza A, HIV-1, West Nile virus and the SARS-CoV acute respiratory syndrome coronavirus.

Hepatitis A virus cellular receptor 1 (HAVCR1) is a membrane receptor for both human hepatitis A virus (HHAV) and TIMD4. HAVCR1 is a type I trans-membrane structural glycoprotein located in the renal proximal tubule epithelial cells. HAVCR1 protein may be involved in the control of asthma and allergic diseases. The reference genome represents an allele which retains a MTTVP amino acid segment that presents defense against atopy in HHAV seropositive individuals.

Sialic acid-binding Ig-like lectin 6 isoform 1 (SIGLEC6) is a member of immunoglobulin superfamily and SIGLEC (sialic acid binding Ig-like lectin) family. SIGLEC6 mediates sialic-acid dependent binding to cells and binds to alpha-2, 6-linked sialic acid. The SIGLEC6 protein localizes in numerous compartments such as membrane fraction, extracellular region and so on. The SIGLEC6 receptor binds sialyl-TN glycans and leptin. Placental expression SIGLEC6 is upregulated in preeclampsia.

Sialic Acid Binding Ig Like Lectin 5, also known as SIGLEC5 is a member of the immunoglobulin superfamily and SIGLEC family. SIGLEC5 contains of 2 Ig-like C2-type domains and 1 Ig-like V-type domain. In addition, SIGLEC5 is expressed by monocytic/myeloid lineage cells. SIGLEC5 is expressed at high levels in peripheral blood leukocytes, spleen, and at lower levels in lymph node, appendix, pancreas, lung, and thymus.

LAIR1 is a glycoprotein expressed on the surface of the majority of human peripheral blood mononuclear leukocytes including T cells, B cells, NK cells, macrophages and dendritic cells. LAIR-1 functions as an inhibitory receptor in NK cells, T cells and B cells. Inhibitory receptors control the immune response to prevent lysis of cells recognized as self. Lair1 consists of a leader sequence, extracellular domain, transmembrane domain, cytoplasmic region.LAIR1 is a member of both the immunoglobulin superfamily and the leukocyte-associated inhibitory receptor family. LAIR1 maps to a region of 19q13.4 labeled the leukocyte receptor cluster, which contains at least 29 genes encoding leukocyte-expressed receptors of the immunoglobulin superfamily.

Sialic acid-binding Ig-like lectin 7 isoform 1, also known as SIGLEC7, is a newly discovered family of sialic acid-binding lectins of the immunoglobulin (Ig) superfamily. The extracellular portion has two Ig-like domains, with the amino-terminal V-set Ig domain containing amino acid residues which known to be implicated in sialic acid recognition by other Siglecs. The combination of an extracellular sialic acid binding site and an intracellular ITIM motif proposes that SIGLEC7 is involved in trans-membrane regulatory signaling reactions. Furthermore, on the cell surface SIGLEC7 exists as a monomer and is expressed on natural killer cells.

C-type Lectin Domain Family 1 Member B, also known as CLEC1B. NK-Natural killer cells express multiple calcium-dependent (C-type) lectin-like receptors, for instance CD94 (KLRD1; MIM 602894) and NKG2D (KLRC4; MIM 602893), which interact with major histocompatibility complex class I molecules and either inhibit or else activate cytotoxicity and cytokine secretion. CLEC1B is a C-type lectin-like receptor which is expressed in myeloid cells as well as in NK cells.

The signal sequence receptor (SSR) is a glycosylated endoplasmic reticulum membrane receptor related with protein translocation across the ER membrane. The SSR consists of 2 subunits, a 34-kD glycoprotein (alpha-SSR or SSR1) and a 22-kD glycoprotein (beta-SSR or SSR2). The human beta-signal sequence receptor gene (SSR2) maps to chromosome bands 1q21-q23. Diseases correlated with SSR2 include calcaneonavicular coalition, and osteosarcoma, and among its related super-pathways are Viral mRNA Translation and Generic Transcription Pathway.

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.

Cytotoxicity Triggering Receptor 3 also known as NCR3 is a natural cytotoxicity receptor (NCR) which assists NK cells in the lysis of tumor cells. Moreover, NCR3 interacts with CD3-zeta (CD247), a T-cell receptor. A single nucleotide polymorphism in the 5' untranslated region of NCR3 has been related with mild malaria suceptibility. Three transcript variants encoding various isoforms have been found for this gene.

Killer-cell immunoglobulin-like receptors (KIRs), are a family of cell surface glycoproteins found on Natural Killer (NK) Cells, which are important cells of the immune system. They control the killing function of these cells by interacting with MHC class I molecules, which are expressed on all cell types. This interaction allows them to identify virally infected cells or tumor cells that have a distinctive low level of Class I MHC on their surface. The majority of KIRs are inhibitory, which means that their recognition of MHC suppresses the cytotoxic activity of their NK cell. Only a limited number of KIRs have the capacity to activate cells. The KIR genes are found in a cluster on chromosome 19q13.4 within the 1 Mb leukocyte receptor complex (LRC). KIR molecules are extremely polymorphic, meaning their gene sequences differ significantly between individuals, so that different individuals have different arrays/repertoires of KIR genes. The KIR proteins are categorized by the number of extracellular immunoglobulin domains (2D or 3D) and by whether they have a long (L) or short (S) cytoplasmic domain. KIR proteins with the long cytoplasmic domain transduce inhibitory signals upon ligand binding via an immune tyrosine-based inhibitory motif (ITIM). Whereas KIR proteins with the short cytoplasmic domain lack the ITIM motif and instead associate with the TYRO protein tyrosine kinase binding protein to transduce activating signals. KIR2DS4 is an activating Killer Cell Ig-like Receptor (KIR, previously called p50 KIR, p50.3, cl39, or KAR-K1), which may recognize class I MHC molecules. KIR2DS4 does not inhibit the activity of NK cells.

LAIR1 is a glycoprotein (~32kDa) expressed on the surface of the majority of human peripheral blood mononuclear leukocytes including T cells, B cells, NK cells, macrophages and dendritic cells. LAIR-1 functions as an inhibitory receptor in NK cells, T cells and B cells. Inhibitory receptors control the immune response to prevent lysis of cells recognized as self. Lair1 consists of a leader sequence, extracellular domain, transmembrane domain, cytoplasmic region.
LAIR1 is a member of both the immunoglobulin superfamily and the leukocyte-associated inhibitory receptor family. LAIR1 maps to a region of 19q13.4 labeled the leukocyte receptor cluster, which contains at least 29 genes encoding leukocyte-expressed receptors of the immunoglobulin superfamily.

C-type Lectin Domain Family 2, Member B (CLEC2B) belongs to the C-type lectin/C-type lectin-like domain (CTL/CTLD) superfamily. Members of the CTL/CTLD family share a common protein fold and have various functions, such as cell adhesion, cell-cell signaling, glycoprotein turnover, and roles in inflammation and immune response. The CLEC2B gene is closely connected to other CTL/CTLD superfamily members on chromosome 12p13 in the natural killer gene complex region. CLEC2B is expressed preferentially in lymphoid tissues, and in most hematopoietic cell types.

Hepatitis A Virus Cellular Receptor 2 (HAVCR2) is a member of the immunoglobulin superfamily. HACVR2 controls macrophage activation. HACVR2 inhibits T-helper type 1 lymphocyte (Th1)-mediated auto- and alloimmune responses and stimulates immunological tolerance.

Galectin 3, or LGALS3, is a protein which belongs to the animal lectins family, that binds betagalactoside residues selectively. LGALS3 is originated and leaves cells through ectocytosis. The protein is capable of inhibition apoptosis and the development of cancer. Galectin 3 is found in epithelial tissues in organisms, it can be located in dendritic cells, Kupffer cells, macrophages etc. LGALS3 levels elevated when inflammation is generating, cell proliferation, trans-activation by viral proteins and cell differentiation.