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FABP7 is a brain fatty acid binding protein. Fatty acid binding proteins (FABPs) are a family of small, highly conserved, cytoplasmic proteins that bind long-chain fatty acids and other hydrophobic ligands. FABPs are are inovlved in fatty acid uptake, transport, and metabolism. FABP7 is expressed in radial glia by the activation of Notch receptors and binds DHA with the highest affinity among all of FABPs. FABP7 plays an important role in transport of hydrophobic ligand with potential morphogenic activity during cns development. FABP7 is required for the establishment of the radial glial fiber system in developing brain, a system that is necessary for the migration of immature neurons to establish cortical layers (by similarity).

Fatty acid binding protein 9 (FABP9) belongs to the fatty acid-binding proteins (FABPs) which are a family of small, extremely conserved, cytoplasmic proteins to bind long-chain fatty acids and other hydrophobic ligands. FABP9 is found in midpachytene spermatocytes and round spermatids, and comprises part of the perinuclear theca. FABP9 probably links intracellular membranes and signals abnormal sperm formation during spermatogenesis.

Fatty acid binding protein 9 (FABP9) belongs to the fatty acid-binding proteins (FABPs) which are a family of small, extremely conserved, cytoplasmic proteins to bind long-chain fatty acids and other hydrophobic ligands. FABP9 is found in midpachytene spermatocytes and round spermatids, and comprises part of the perinuclear theca. FABP9 probably links intracellular membranes and signals abnormal sperm formation during spermatogenesis.

FADD is an adaptor protein that cooperates with a variety of cell surface receptors and mediates cell apoptotic signals. Using its C-terminal death domain, FADD is recruited by TNFRSF6/Fas-receptor, tumor necrosis factor receptor, TNFRSF25, and TNFSF10/TRAIL-receptor, and consequently it take parts in the death signaling initiated by these receptors. FADD interaction with the receptors reviels the N-terminal effector domain of, which allows it to recruit caspase-8, and thus initiate the cysteine protease cascade. Knockout studies in mice furthermore propose the significance of FADD in premature T cell development. FADD plays a role in survival/proliferation and cell cycle development. FADD also takes part in cellular sublocalization, protein phosphorylation, and inhibitory molecules.

FADD is an adaptor protein that cooperates with a variety of cell surface receptors and mediates cell apoptotic signals. Using its C-terminal death domain, FADD is recruited by TNFRSF6/Fas-receptor, tumor necrosis factor receptor, TNFRSF25, and TNFSF10/TRAIL-receptor, and consequently it take parts in the death signaling initiated by these receptors. FADD interaction with the receptors reviels the N-terminal effector domain of, which allows it to recruit caspase-8, and thus initiate the cysteine protease cascade. Knockout studies in mice furthermore propose the significance of FADD in premature T cell development. FADD plays a role in survival/proliferation and cell cycle development. FADD also takes part in cellular sublocalization, protein phosphorylation, and inhibitory molecules.

Fumarylacetoacetate hydrolase domain-containing protein 1 (FAHD1) is a member of the FAH family. FAHD1 is considered to have hydrolase activity and it uses Magnesium and Calcium as cofactors. It seems quite likely that the metal binding sites are involved in an enzymatic activity connected to the catabolism of aromatic amino acids.

Fas apoptotic inhibitory molecule, also known as FAIM function as an inducible effector molecule which mediates Fas resistance produced by surface Ig engagement in B cells. In addition FAIM protects against death receptor-triggered apoptosis and regulates B-cell signaling and differentiation. Among the diseases associated with FAIM are hemorrhagic thrombocythemia, and food allergy.

Family with Sequence Similarity 107, Member B (FAM107B) which is a part of the FAM107 family, is expressed in most tissues in the human body. FAM107B exists in all stages of human development.

Family With Sequence Similarity 19 Member-A5 (FAM19A5) belongs to the TAFA family which is comprised of 5 highly homologous genes encoding small secreted proteins. These proteins have conserved cysteine residues at fixed positions, and are remotely related to MIP-1alpha, which is a member of the CC-chemokine family. The TAFA proteins are primarily expressed in specific regions of the brain, and are assumed to serve as brain-specific chemokines or neurokines which act as regulators of immune and nervous cells.

Family with Sequence Similarity 3, Member A (FAM3A) is a member of the FAM3 family along with FAM3B (Pander) protein which induces apoptosis of pancreatic alpha and beta cells. FAM3A is a cytokine-like protein, which is expressed in almost all tissues such as the testis, pancreas, adrenal, placenta, brain, fetal brain, liver, kidney, skeletal muscle and the heart. FAM3A gene expression may be regulated by peroxisome proliferator-activated receptor gamma, and the FAM3A protein might be involved in the regulation of glucose and lipid metabolism. Although the function of the FAM3A protein has been unclear until now, it may act as a defensin against invading fungal microorganisms.

FAM3B Protein induces apoptosis of alpha and beta cells in a quantity and time dependent way.

FAM3C is a member of the FAM3 family and holds a GG domain. Pancreatic cancer-derived cells demonstrate a difference in expression of this protein. FAM3C is a downstream target gene for the Nkx5-1 transcription factor, and there for takes part in cell differentiation and proliferation through inner ear embryogenesis. In addition, FAM3C has a role in retinal laminar formation and promotes epithelial to mesenchymal transition.

Family with Sequence Similarity 3, Member D (FAM3D) is a member of the FAM3 family. The FAM3D gene is linked to narcolepsy and diabetes mellitus in pancreatic adenocarcinoma, however FAM3D function of remains vague. FAM3D is amply expressed in the placenta and weakly expressed in the small intestine.

Family with Sequence Similarity 49, Member B (FAM49B) is a member of the FAM49 family. In the latest genome-wide transcriptional analysis, a gene signature was identified for multiple sclerosis (MS), which reverted back to normal during pregnancy. The reversion was mostly evident for seven genes: SOCS2, TNFAIP3, NR4A2, CXCR4, POLR2J, FAM49B, and STAG3L1, most of which are negative regulators of inflammation.

FAM50A is a member of the FAM50 family. FAM50A is highly conserved in length and sequence among numerous species. FAM50A is a basic protein comprised of a nuclear localization signal, and can function as a DNA-binding protein or a transcriptional factor. FAM50A expressed in all tissues mainly abundant in fetal brain, liver and kidney. High levels of FAM50A were observed in the adult's skeletal muscle, spleen, thymus, prostate and the small intestine.

FAM84A is a member of the FAM84 family of proteins and is primarily expressed in testis. FAM84A is restricted to a subcellular membrane region in which there is no interaction between adjoining cells and takes part in cell morphology. Additionally, FAM84A expression increases cell motility which can result in invasion and metastasis of cancer cells. FAM84A is up-regulated in pancreatic cancer, colorectal cancer lung cancer, bladder cancer tissues and cholangiocarcinoma.

Family with Sequence Similarity 84, Member B (FAM84B) coprecipitated with a downstream effector of RAS, CRAF. Binding of FAM83B with CRAF interrupted CRAF/14-3-3 interactions and increased CRAF membrane localization, causing elevated MAPK and mammalian target of rapamycin (mTOR) signaling. FAM84B is an oncogene and possibly represents a new target for therapeutic intervention.

FANK1 was localized in the nuclei of identical cells in the seminiferous epithelium. Depending on its nuclear localization, a gene ontology analysis proposes that FANK1 has a DNA binding activity therefor operates as a transcription factor. The extremely controlled expression of FANK1, suggests that it takes part in regulating gene expression in the transition from the meiotic phase to the haploid phase throughout spermatogenesis.

DPP4 also called adenosine deaminase complexing protein-2, and T-cell activation antigen CD26 is a serine exopeptidase and complex enzyme that is expressed on the surface of most cell types. DPPIV is an intrinsic membrane glycoprotein and a serine exopeptidase that cleaves X-proline dipeptides from the N-terminus of polypeptides. DPP4 plays a role in t-cell activation. DPP4 is associated with intracellular signal transduction, apoptosis and involved in tumor biology. There are at least 63 substrates which can bind specifically to DPP4 enzyme including growth factors, chemokines, neuro peptides. Furthermore, DPP4 plays a major role in glucose metabolism by cleaving incretins such as glucose-dependent insulinotropic polypeptide (GIP) and GLP-1.

Phenylalanyl-tRNA synthetase 2 mitochondrial (FARS2) is a member of the class II aminoacyl- tRNA synthetase family. FARS2 is a mitochondrial matrix protein. FARS2 when acting as a monomer, catalyzes the ATP-dependent conversion of L-phenylalanine and tRNA (Phe) to L-phenlalanyltRNA (Phe), an event which is vital for proper translation and protein expression.

FARSB, also known as Phenylalanyl-TRNA Synthetase Beta is a member of the phenylalanyl-tRNA synthetase beta subunit family. FARSB is composed tetramer of two alpha and two beta subunits. In the presence of ATP, this tetramer is accountable for attaching L-phenylalanine to the terminal adenosine of the appropriate tRNA.

The Fas receptor (CD95) mediates apoptotic signaling by Fas-ligand expressed on the surface of other cells. The Fas-FasL interaction plays an important role in the immune system and lack of this system leads to autoimmunity, indicating that Fas-mediated apoptosis removes self-reactive lymphocytes. Fas signaling is also involved in immune surveillance to remove transformed cells and virus infected cells. Binding of FAS to oligimerized FasL on another cell activates apoptotic signaling through a cytoplasmic domain termed the death domain that interacts with signaling adaptors including FAF, FADD and DAX to activate the caspase proteolytic cascade. Caspase-8 and caspase-10 are first activated, to then cleave and activate downstream caspases, and a variety of cellular substrates that lead to cell death. Caspases cleave nuclear lamins, causing the nucleus to break down and lose its normal structure and another caspase substrate is DFF, inducing cleavage and degradation of the genome. Other caspase substrates are involved in cytoskeletal structure, cell cycle regulation and signaling pathways. Activation of JNK kinase, activation of Jun, and production of ceramide may also play roles in Fas-mediated apoptosis. Activation of fas-mediated apoptosis is opposed by I-FLICE and FAP. Viruses and tumors may escape immune surveillance in part through suppression of fas-mediated apoptosis using similar mechanisms.

The Fas receptor (CD95) mediates apoptotic signaling by Fas-ligand expressed on the surface of other cells. The Fas-FasL interaction plays an important role in the immune system and lack of this system leads to autoimmunity, indicating that Fas-mediated apoptosis removes self-reactive lymphocytes. Fas signaling is also involved in immune surveillance to remove transformed cells and virus infected cells. Binding of FAS to oligimerized FasL on another cell activates apoptotic signaling through a cytoplasmic domain termed the death domain that interacts with signaling adaptors including FAF, FADD and DAX to activate the caspase proteolytic cascade. Caspase-8 and caspase-10 are first activated, to then cleave and activate downstream caspases, and a variety of cellular substrates that lead to cell death. Caspases cleave nuclear lamins, causing the nucleus to break down and lose its normal structure and another caspase substrate is DFF, inducing cleavage and degradation of the genome. Other caspase substrates are involved in cytoskeletal structure, cell cycle regulation and signaling pathways. Activation of JNK kinase, activation of Jun, and production of ceramide may also play roles in Fas-mediated apoptosis. Activation of fas-mediated apoptosis is opposed by I-FLICE and FAP. Viruses and tumors may escape immune surveillance in part through suppression of fas-mediated apoptosis using similar mechanisms.

The Fas receptor (CD95) mediates apoptotic signaling by Fas-ligand expressed on the surface of other cells. The Fas-FasL interaction plays an important role in the immune system and lack of this system leads to autoimmunity, indicating that Fas-mediated apoptosis removes self-reactive lymphocytes. Fas signaling is also involved in immune surveillance to remove transformed cells and virus infected cells. Binding of FAS to oligimerized FasL on another cell activates apoptotic signaling through a cytoplasmic domain termed the death domain that interacts with signaling adaptors including FAF, FADD and DAX to activate the caspase proteolytic cascade. Caspase-8 and caspase-10 are first activated, to then cleave and activate downstream caspases, and a variety of cellular substrates that lead to cell death. Caspases cleave nuclear lamins, causing the nucleus to break down and lose its normal structure and another caspase substrate is DFF, inducing cleavage and degradation of the genome. Other caspase substrates are involved in cytoskeletal structure, cell cycle regulation and signaling pathways. Activation of JNK kinase, activation of Jun, and production of ceramide may also play roles in Fas-mediated apoptosis. Activation of fas-mediated apoptosis is opposed by I-FLICE and FAP. Viruses and tumors may escape immune surveillance in part through suppression of fas-mediated apoptosis using similar mechanisms.

Fas and Fas Ligand (FasL) are members of the TNF superfamily and are type I and type II transmembrane proteins, respectively. Binding of FasL to Fas initiates apoptosis in Fas-bearing cells. The apoptosis mechanism involves the recruitment of pro-caspase 8 through an adaptor molecule named FADD followed by processing of the pro-enzyme to active forms. These active caspases subsequently cleave a variety of cellular substrates leading to the eventual cell death. sFasR is able to inhibit FasL-induced apoptosis by acting as a decoy receptor whicht serves as a sink for FasL. The full length Fas Receptor is a 319 a.a type I transmembrane protein, which contains a 157 a.a extracellular domain, a 17 a.a transmembrane domain, and 145 a.a cytoplasmic domain. The mature human Fas ECD shares 55%, 58%, a.a sequence identity with the mouse, rat, Fas, respectively.

FAS / CD95 is a 36kDa transmembrane type I receptor, which belongs to the NF/NGF receptor super-family. It is a potent inducer of apoptosis in cells of the immune system upon interaction with its natural ligand, CD95L. Although the CD95/CD95L system could play a role in tumor regression, tumor cells seem to down-regulate CD95 expression as a mechanism of resistance to CD95L-induced killing by T lymphocytes and NK cells. The Fas antigen is expressed on the surface of various cell types, including activated T and B lymphocytes and T lymphoblastoid cell line. CD95 is also expressed in a broad panel of non-transformed cells outside the immune system.

FAS or tumor necrosis factor receptor superfamily member 6 or TNFRSF6, is part of the death receptor family, which is part of the TNF receptor protein family. TNFRSF6 has a crucial part in regulating viral infections. FAS protein can be found in almost all cell types, when its cognate ligand (FasL) can be found in activated T cells, NK cells & dendritic cells. The regulating protein of FasL & TRAIL on HCMV-infected dendritic enhances direct destruction of activated T lymphocytes. furthermore, subvertneutrophil function in HCMV retinitis can occur when FasL is activated in HCMV infected retinal pigment epithelial cells.

The type II transmembrane protein FASLG is a member of the tumor necrosis factor (TNF) superfamily. A fas ligand/receptor interaction has a significant part in the regulation of the immune system and the advancement of cancer. FASLG is expressed on the activated T cell surface as a nondisulfidelinked homotrimer. FASLG binding to Fas/CD95/TNFRSF6 on a nearby cell prompts apoptosis in the Fas expressing cell. FASLG is released from the cell surface by metalloproteinases as a soluble molecule that stays trimeric and is able to bind with Fas, but its capability to activate apoptosis is radically reduced. In addition, FASLG binds to DcR3 - a soluble trap receptor with no signal transduction capabilities. Flawed Fas-mediated apoptosis causes oncogenesis in addition to drug resistance in existing tumors. Constitutive expression of FASLG in a variety of tumors enables their immune evasion. Both mouse and human FASLG are active on mouse and human cells.

The type II transmembrane protein FASLG is a member of the tumor necrosis factor (TNF) superfamily. A fas ligand/receptor interaction has a significant part in the regulation of the immune system and the advancement of cancer. FASLG is expressed on the activated T cell surface as a nondisulfidelinked homotrimer. FASLG binding to Fas/CD95/TNFRSF6 on a nearby cell prompts apoptosis in the Fas expressing cell. FASLG is released from the cell surface by metalloproteinases as a soluble molecule that stays trimeric and is able to bind with Fas, but its capability to activate apoptosis is radically reduced. In addition, FASLG binds to DcR3 - a soluble trap receptor with no signal transduction capabilities. Flawed Fas-mediated apoptosis causes oncogenesis in addition to drug resistance in existing tumors. Constitutive expression of FASLG in a variety of tumors enables their immune evasion. Both mouse and human FASLG are active on mouse and human cells.

FBL is a significant small nucleolar protein in eukaryotes, which has an essential role in pre-rRNA processing during ribosomal biogenesis. Fibrillarin is a component of several ribonucleoproteins including a nucleolar small nuclear ribonucleoprotein (SnRNP) and one of the two classes of small nucleolar ribonucleoproteins (snoRNPs). Fibrillarin contains an N-terminal repetitive domain which is rich in glycine and arginine residues, like fibrillarins in other species. Fibrillarin’s central region is similar to an RNA-binding domain and contains an RNP consensus sequence. FBL is linked to the U3, U8, and U13 small nuclear RNAs and is positioned in the dense fibrillar component (DFC) of the nucleolus. Antisera from roughly 8% of humans with the autoimmune disease scleroderma recognize fibrillarin.

Filamin binding LIM protein 1 (FBLIM1) plays a role as an anchoring site for cell-ECM adhesion proteins and filamin-containing actin filaments. FBLIM1 is involved in cell shape spreading and motility. FBLIM1 participates in the regulation of filamin-mediated cross-linking and stabilization of actin filaments. FBLIM1 promotes stimulation of integrins and regulates integrin-mediated cell-cell adhesion.

FBP1 is a gluconeogenesis regulatory protein which catalyzes the hydrolysis of fructose 1,6-bisphosphate to fructose 6-phosphate and inorganic phosphate. FBP1 deficiency is associated with hypoglycemia and metabolic acidosis. FBP1 regulates mouse endogenous glucose production. FBP1 coupled with phosphofructokinase (PFK) takes part in the metabolism of pancreatic islet cells.

FBP1 or Fructose-1, 6-bisphosphatase 1 is an enzyme, catalyzing the formation of fructose 6-phosphate & inorganic phosphate from fructose 1, 6-bisphosphate. FBP1 is part of the gluconeogenesis regulatory enzymes. Mutations in the enzyme gene can result in metabolic acidosis & hypoglycemia.

Fructose-1,6-bisphosphatase isozyme 2 (FBP2) is a part of the FBPase class 1 family. FBP2 is a gluconeogenesis regulatory enzyme Which catalyzes the hydrolysis of fructose 1,6-bisphosphate to fructose 6-phosphate and inorganic phosphate.

Fructose-1,6-bisphosphatase isozyme 2 (FBP2) is a part of the FBPase class 1 family. FBP2 is a gluconeogenesis regulatory enzyme Which catalyzes the hydrolysis of fructose 1,6-bisphosphate to fructose 6-phosphate and inorganic phosphate.

F-Box Protein 2 (FBXO2) is a part of the F-box protein family. The F-box proteins are one of the 4 subunits of the ubiquitin protein ligase complex called SCFs (SKP1-cullin-F-box), which takes part in phosphorylation-dependent ubiquitination. The F-box proteins are divided into 3 classes. FBXO2 belongs to the Fbxs class which contains either different protein-protein interaction modules or no recognizable motifs. FBXO2 is extremely similar to the rat neural F Box 42 kDa protein which is enriched in the nervous system and plays a role in maintaining neurons in a postmitotic state.

F-Box Protein 6, also known as FBXO6, is a part of the F-box protein family which is characterized by a roughly forty amino acid motif, the F-box. The F-box proteins are one of the 4 subunits of the ubiquitin protein ligase complex called SCFs (SKP1-cullin-F-box) that operates in phosphorylation-dependent ubiquitination. The F-box proteins are divided into three categories: Fbws containing WD-40 domains, Fbls containing leucine-rich repeats, and Fbxs containing different protein-protein interaction modules or no recognizable motifs. FBXO6 is a part of the Fbxs category, and its C-terminal area is very similar to that of rat NFB42 (neural F Box 42 kDa) which is involved in the control of the cell cycle.

Fc Fragment Of IgA Receptor, also known as FCAR, is part of the multichain immune recognition receptor family which is the most abundant immunoglobulin in mucosal areas however it is only the second most common antibody isotype in serum. FCAR participates in both pro-and anti-inflammatory responses depending on the state of IgA bound. FCAR is also a vital Fc receptor for neutrophil killing of tumor cells. Once FCAR expressing neutrophils interact with IgA-opsonized tumor cells, the neutrophils not only show antibody-dependent cell-mediated cytotoxicity, but also release the cytokines TNF-α and IL-1β which cause increased neutrophil migration to the site.

Fc fragment of IgE, high affinity I, receptor for; alpha polypeptide (FCER1A) binds to the Fc region of immunoglobulins epsilon. FCER1A is a high affinity receptor. In addition FCER1A is responsible for starting the allergic response. Binding of allergen to receptor-bound IgE leads to cell activation and the release of mediators such as histamine which is responsible for the manifestations of allergy. This receptor is contains of an alpha subunit, a beta subunit, and two gamma subunits. FCER1A stands for the alpha subunit. Among the diseases associated with FCER1A are mast-cell leukemia, and allergic asthma.

Fc fragment of IgE, high affinity I, receptor for; alpha polypeptide (FCER1A) binds to the Fc region of immunoglobulins epsilon. FCER1A is a high affinity receptor. In addition FCER1A is responsible for starting the allergic response. Binding of allergen to receptor-bound IgE leads to cell activation and the release of mediators such as histamine which is responsible for the manifestations of allergy. This receptor is contains of an alpha subunit, a beta subunit, and two gamma subunits. FCER1A stands for the alpha subunit. Among the diseases associated with FCER1A are mast-cell leukemia, and allergic asthma.

FCGR1A is a member of to the immunoglobulin superfamily. FCGR1A protein acts as a high affinity receptor for the Fc region of immunoglobulins gamma and has a vital part in both innate and adaptive immune response.

CD32a, also known as FCGR2A, belongs to a family of immunoglobulin Fc receptor genes located on the surface of various immune response cells. FCGR2A which is a cell surface receptor found on phagocytic cells like macrophages and neutrophils, takes part in the process of phagocytosis and clearing of immune complexes. FCGR2A initiates cellular responses against pathogens and soluble antigens by binding to IgG. FCGR2A, which is a low affinity receptor, binds to the Fc region of immunoglobulins gamma.

FCGR2B is a low affinity receptor for the Fc region of immunoglobulin gamma complexes. FCGR2B participates in the phagocytosis of immune complexes and in the regulation of antibody production by B-cells. FCGR2B Expressed in monocyte, neutrophils, macrophages, basophils, eosinophils, Langerhans cells, B-cells, platelets cells and placenta (endothelial cells). Variants in FCGR2B may increase susceptibilty to systemic lupus erythematosus (SLE).

Low affinity immunoglobulin gamma Fc region receptor III-A (FCGR3A) is a receptor for the Fc portion of immunoglobulin G, and is involved in the elimination of antigen-antibody complexes from the circulation, as well as other antibody-dependent responses. FCGR3A needs to associate with the gamma subunit of Fc epsilon. The FCGR3A receptor is expressed on natural killer (NK) cells as an integral membrane glycoprotein anchored through a transmembrane peptide, while FCGR3B is expressed on polymorphonuclear neutrophils (PMN) where the receptor is anchored through a phosphatidylinositol (PI) linkage. In addition, FCGR3A is expressed on macrophages, subpopulation of T-cells, immature thymocytes and placental trophoblasts. FCGR3A mediates antibody-dependent cellular cytotoxicity (ADCC) and other antibody-dependent responses, such as phagocytosis. FCGR3A gene mutations are linked with susceptibility to recurrent viral infections, susceptibility to systemic lupus erythematosus, and alloimmune neonatal neutropenia.

Low affinity immunoglobulin gamma Fc region receptor III-A (FCGR3A) is a receptor for the Fc portion of immunoglobulin G, and is involved in the elimination of antigen-antibody complexes from the circulation, as well as other antibody-dependent responses. FCGR3A needs to associate with the gamma subunit of Fc epsilon. The FCGR3A receptor is expressed on natural killer (NK) cells as an integral membrane glycoprotein anchored through a transmembrane peptide, while FCGR3B is expressed on polymorphonuclear neutrophils (PMN) where the receptor is anchored through a phosphatidylinositol (PI) linkage. In addition, FCGR3A is expressed on macrophages, subpopulation of T-cells, immature thymocytes and placental trophoblasts. FCGR3A mediates antibody-dependent cellular cytotoxicity (ADCC) and other antibody-dependent responses, such as phagocytosis. FCGR3A gene mutations are linked with susceptibility to recurrent viral infections, susceptibility to systemic lupus erythematosus, and alloimmune neonatal neutropenia.

Low affinity immunoglobulin gamma Fc region receptor III-A (FCGR3A) is a receptor for the Fc portion of immunoglobulin G, and is involved in the elimination of antigen-antibody complexes from the circulation, as well as other antibody-dependent responses. FCGR3A needs to associate with the gamma subunit of Fc epsilon. The FCGR3A receptor is expressed on natural killer (NK) cells as an integral membrane glycoprotein anchored through a transmembrane peptide, while FCGR3B is expressed on polymorphonuclear neutrophils (PMN) where the receptor is anchored through a phosphatidylinositol (PI) linkage. In addition, FCGR3A is expressed on macrophages, subpopulation of T-cells, immature thymocytes and placental trophoblasts. FCGR3A mediates antibody-dependent cellular cytotoxicity (ADCC) and other antibody-dependent responses, such as phagocytosis. FCGR3A gene mutations are linked with susceptibility to recurrent viral infections, susceptibility to systemic lupus erythematosus, and alloimmune neonatal neutropenia.

FCGR3B, also known as CD16b belongs to the Ig super family. FCGR3B encodes a glycosylphosphatidylinositol (GPI)-anchored protein which is expressed constitutively by neutrophils. FCGR3B binds to complex or aggregated IgG and monomeric IgG. Different from III-A, FCGR3B cannot arbitrate antibody-dependent cytotoxicity and phagocytosis. FCGR3B operate to capture immune complexes in peripheral blood circulation that does not activate neutrophils.