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Richard S Blumberg - One of the best experts on this subject based on the ideXlab platform.
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the Neonatal Fc Receptor Fcrn a misnomer
Frontiers in Immunology, 2019Co-Authors: Michal Pyzik, Jan Terje Andersen, Inger Sandlie, Richard S Blumberg, Kine Marita Knudsen Sand, Jonathan J HubbardAbstract:Antibodies are essential components of an adaptive immune response. Immunoglobulin G (IgG) is the most common type of antibody found in circulation and extracellular fluids. Although IgG alone can directly protect the body from infection through the activities of its antigen binding region, the majority of IgG immune functions are mediated via proteins and Receptors expressed by specialized cell subsets that bind to the fragment crystallizable (Fc) region of IgG. Fc gamma (γ) Receptors (FcγR) belong to a broad family of proteins that presently include classical membrane-bound surface Receptors as well as atypical intracellular Receptors and cytoplasmic glycoproteins. Among the atypical FcγRs, the Neonatal Fc Receptor (FcRn) has increasingly gained notoriety given its intimate influence on IgG biology and its ability to also bind to albumin. FcRn functions as a recycling or transcytosis Receptor that is responsible for maintaining IgG and albumin in the circulation, and bidirectionally transporting these two ligands across polarized cellular barriers. More recently, it has been appreciated that FcRn acts as an immune Receptor by interacting with and facilitating antigen presentation of peptides derived from IgG immune complexes (IC). Here we review FcRn biology and focus on newer advances including how emerging FcRn-targeted therapies may affect the immune responses to IgG and IgG IC.
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transepithelial transport of Fc targeted nanoparticles by the Neonatal Fc Receptor for oral delivery
Science Translational Medicine, 2013Co-Authors: Eric M Pridgen, Richard S Blumberg, Timothy Kuo, Frank Alexis, Etgar Levynissenbaum, Rohit Karnik, Robert LangerAbstract:Nanoparticles are poised to have a tremendous impact on the treatment of many diseases, but their broad application is limited because currently they can only be administered by parenteral methods. Oral administration of nanoparticles is preferred but remains a challenge because transport across the intestinal epithelium is limited. We show that nanoparticles targeted to the Neonatal Fc Receptor (FcRn), which mediates the transport of immunoglobulin G antibodies across epithelial barriers, are efficiently transported across the intestinal epithelium using both in vitro and in vivo models. In mice, orally administered FcRn-targeted nanoparticles crossed the intestinal epithelium and reached systemic circulation with a mean absorption efficiency of 13.7%*hour compared with only 1.2%*hour for nontargeted nanoparticles. In addition, targeted nanoparticles containing insulin as a model nanoparticle-based therapy for diabetes were orally administered at a clinically relevant insulin dose of 1.1 U/kg and elicited a prolonged hypoglycemic response in wild-type mice. This effect was abolished in FcRn knockout mice, indicating that the enhanced nanoparticle transport was specifically due to FcRn. FcRn-targeted nanoparticles may have a major impact on the treatment of many diseases by enabling drugs currently limited by low bioavailability to be efficiently delivered though oral administration.
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the immunologic functions of the Neonatal Fc Receptor for igg
Journal of Clinical Immunology, 2013Co-Authors: Timo Rath, Timothy T Kuo, Derry C Roopenian, Kristi Baker, Masaru Yoshida, Shuowang Qiao, Wayne I Lencer, Kanna Kobayashi, Edda Fiebiger, Richard S BlumbergAbstract:Careful regulation of the body’s immunoglobulin G (IgG) and albumin concentrations is necessitated by the importance of their respective functions. As such, the Neonatal Fc Receptor (FcRn), as a single Receptor, is capable of regulating both of these molecules and has become an important focus of investigation. In addition to these essential protection functions, FcRn possesses a number of other functions that are equally as critical and are increasingly coming to attention. During the very first stages of life, FcRn mediates the passive transfer of IgG from mother to offspring both before and after birth. In the adult, FcRn regulates the persistence of both IgG and albumin in the serum as well as the movement of IgG, and any bound cargo, between different compartments of the body via transcytosis across polarized cells. FcRn is also expressed by hematopoietic cells; consistent with this, FcRn regulates MHC class II presentation and MHC class I cross-presentation by dendritic cells. As such, FcRn plays an important role in immune surveillance throughout adult life. The increasing appreciation for FcRn in both homeostatic and pathological conditions is generating an intense interest in the potential for therapeutic modulation of FcRn binding to IgG and albumin.
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Neonatal Fc Receptor from immunity to therapeutics
Journal of Clinical Immunology, 2010Co-Authors: Timothy T Kuo, Victoria G. Aveson, Kristi Baker, Masaru Yoshida, Shuowang Qiao, Wayne I Lencer, Richard S BlumbergAbstract:The Neonatal Fc Receptor (FcRn), also known as the Brambell Receptor and encoded by Fcgrt, is a MHC class I like molecule that functions to protect IgG and albumin from catabolism, mediates transport of IgG across epithelial cells, and is involved in antigen presentation by professional antigen presenting cells. Its function is evident in early life in the transport of IgG from mother to fetus and neonate for passive immunity and later in the development of adaptive immunity and other functions throughout life. The unique ability of this Receptor to prolong the half-life of IgG and albumin has guided engineering of novel therapeutics. Here, we aim to summarize the basic understanding of FcRn biology, its functions in various organs, and the therapeutic design of antibody- and albumin-based therapeutics in light of their interactions with FcRn.
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immune and non immune functions of the not so Neonatal Fc Receptor Fcrn
Seminars in Immunopathology, 2009Co-Authors: Kristi Baker, Masaru Yoshida, Shuowang Qiao, Wayne I Lencer, Kanna Kobayashi, Timothy Kuo, Richard S BlumbergAbstract:Careful regulation of the body’s immunoglobulin-G (IgG) and albumin concentrations is necessitated by the importance of their respective functions. As such, the Neonatal Fc Receptor (FcRn) which, as a single Receptor, is capable of regulating both of these molecules, has become an important focus of investigation. In addition to these essential protection functions, FcRn possesses a host of other functions that are equally as critical. During the very first stages of life, FcRn mediates the passive transfer of IgG from mother to offspring both before and after birth. In the adult, FcRn regulates the persistence of both IgG and albumin in the serum as well as the movement of IgG, and any bound cargo, between different compartments of the body. This shuttling allows for the movement not only of monomeric ligand but also of antigen/antibody complexes from one cell type to another in such a way as to facilitate the efficient initiation of immune responses towards opsonized pathogens. As such, FcRn continues to play the role of an immunological sensor throughout adult life, particularly in regions such as the gut which are exposed to a large number of infectious antigens. Increasing appreciation for the contributions of FcRn to both homeostatic and pathological states is generating an intense interest in the potential for therapeutic modulation of FcRn binding. A greater understanding of FcRn’s pleiotropic roles is thus imperative for a variety of therapeutic purposes.
Wayne I Lencer - One of the best experts on this subject based on the ideXlab platform.
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the immunologic functions of the Neonatal Fc Receptor for igg
Journal of Clinical Immunology, 2013Co-Authors: Timo Rath, Timothy T Kuo, Derry C Roopenian, Kristi Baker, Masaru Yoshida, Shuowang Qiao, Wayne I Lencer, Kanna Kobayashi, Edda Fiebiger, Richard S BlumbergAbstract:Careful regulation of the body’s immunoglobulin G (IgG) and albumin concentrations is necessitated by the importance of their respective functions. As such, the Neonatal Fc Receptor (FcRn), as a single Receptor, is capable of regulating both of these molecules and has become an important focus of investigation. In addition to these essential protection functions, FcRn possesses a number of other functions that are equally as critical and are increasingly coming to attention. During the very first stages of life, FcRn mediates the passive transfer of IgG from mother to offspring both before and after birth. In the adult, FcRn regulates the persistence of both IgG and albumin in the serum as well as the movement of IgG, and any bound cargo, between different compartments of the body via transcytosis across polarized cells. FcRn is also expressed by hematopoietic cells; consistent with this, FcRn regulates MHC class II presentation and MHC class I cross-presentation by dendritic cells. As such, FcRn plays an important role in immune surveillance throughout adult life. The increasing appreciation for FcRn in both homeostatic and pathological conditions is generating an intense interest in the potential for therapeutic modulation of FcRn binding to IgG and albumin.
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Neonatal Fc Receptor from immunity to therapeutics
Journal of Clinical Immunology, 2010Co-Authors: Timothy T Kuo, Victoria G. Aveson, Kristi Baker, Masaru Yoshida, Shuowang Qiao, Wayne I Lencer, Richard S BlumbergAbstract:The Neonatal Fc Receptor (FcRn), also known as the Brambell Receptor and encoded by Fcgrt, is a MHC class I like molecule that functions to protect IgG and albumin from catabolism, mediates transport of IgG across epithelial cells, and is involved in antigen presentation by professional antigen presenting cells. Its function is evident in early life in the transport of IgG from mother to fetus and neonate for passive immunity and later in the development of adaptive immunity and other functions throughout life. The unique ability of this Receptor to prolong the half-life of IgG and albumin has guided engineering of novel therapeutics. Here, we aim to summarize the basic understanding of FcRn biology, its functions in various organs, and the therapeutic design of antibody- and albumin-based therapeutics in light of their interactions with FcRn.
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immune and non immune functions of the not so Neonatal Fc Receptor Fcrn
Seminars in Immunopathology, 2009Co-Authors: Kristi Baker, Masaru Yoshida, Shuowang Qiao, Wayne I Lencer, Kanna Kobayashi, Timothy Kuo, Richard S BlumbergAbstract:Careful regulation of the body’s immunoglobulin-G (IgG) and albumin concentrations is necessitated by the importance of their respective functions. As such, the Neonatal Fc Receptor (FcRn) which, as a single Receptor, is capable of regulating both of these molecules, has become an important focus of investigation. In addition to these essential protection functions, FcRn possesses a host of other functions that are equally as critical. During the very first stages of life, FcRn mediates the passive transfer of IgG from mother to offspring both before and after birth. In the adult, FcRn regulates the persistence of both IgG and albumin in the serum as well as the movement of IgG, and any bound cargo, between different compartments of the body. This shuttling allows for the movement not only of monomeric ligand but also of antigen/antibody complexes from one cell type to another in such a way as to facilitate the efficient initiation of immune responses towards opsonized pathogens. As such, FcRn continues to play the role of an immunological sensor throughout adult life, particularly in regions such as the gut which are exposed to a large number of infectious antigens. Increasing appreciation for the contributions of FcRn to both homeostatic and pathological states is generating an intense interest in the potential for therapeutic modulation of FcRn binding. A greater understanding of FcRn’s pleiotropic roles is thus imperative for a variety of therapeutic purposes.
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how the controller is controlled Neonatal Fc Receptor expression and immunoglobulin g homeostasis
Immunology, 2007Co-Authors: Shuowang Qiao, Wayne I Lencer, Richard S BlumbergAbstract:With the discovery of immunoglobulins, immunoglobulin G (IgG) was recognized to possess two unique properties: selective pre- or postnatal transepithelial transport across the placenta in humans or the intestinal epithelium in rodents, respectively, and a prolonged half-life relative to other serum proteins, suggesting protection from catabolism in adults. These observations were noted by Francis Brambell, who further predicted the presence of a saturable Receptor responsible for both biological functions. 1 Two decades after these predictions, biochemical and ultimately molecular biological evidence was obtained, in the late 1980s, for the presence of a Receptor that was physiologically active in Neonatal rodent epithelium. 2,3 However, not until recently with the generation of X-ray crystallographic structures, subsequent structure–function analyses and the creation of a knock-out animal, has it become clear that the so-called Neonatal Fc Receptor for IgG (FcRn) is responsible for both of the aforementioned functional attributes of IgG physiology: its transport across the Neonatal epithelium of rodents and the avoidance of catabolism. 4–8 FcRn consists of a glycosylated heavy chain that is closely related to major histocompatibility complex (MHC) class I molecules in non-covalent association with b2microglobulin (b2m). 9 FcRn binds IgG in a strictly pH
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How the controller is controlled – Neonatal Fc Receptor expression and immunoglobulin G homeostasis
Immunology, 2006Co-Authors: Shuowang Qiao, Wayne I Lencer, Richard S BlumbergAbstract:With the discovery of immunoglobulins, immunoglobulin G (IgG) was recognized to possess two unique properties: selective pre- or postnatal transepithelial transport across the placenta in humans or the intestinal epithelium in rodents, respectively, and a prolonged half-life relative to other serum proteins, suggesting protection from catabolism in adults. These observations were noted by Francis Brambell, who further predicted the presence of a saturable Receptor responsible for both biological functions. 1 Two decades after these predictions, biochemical and ultimately molecular biological evidence was obtained, in the late 1980s, for the presence of a Receptor that was physiologically active in Neonatal rodent epithelium. 2,3 However, not until recently with the generation of X-ray crystallographic structures, subsequent structure–function analyses and the creation of a knock-out animal, has it become clear that the so-called Neonatal Fc Receptor for IgG (FcRn) is responsible for both of the aforementioned functional attributes of IgG physiology: its transport across the Neonatal epithelium of rodents and the avoidance of catabolism. 4–8 FcRn consists of a glycosylated heavy chain that is closely related to major histocompatibility complex (MHC) class I molecules in non-covalent association with b2microglobulin (b2m). 9 FcRn binds IgG in a strictly pH
Pamela J. Bjorkman - One of the best experts on this subject based on the ideXlab platform.
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Ligand Valency Affects Transcytosis, Recycling and Intracellular Trafficking Mediated by the Neonatal Fc Receptor
Traffic, 2006Co-Authors: Devin Tesar, Noreen E. Tiangco, Pamela J. BjorkmanAbstract:The Neonatal Fc Receptor (FcRn) transports IgG across epithelial cell barriers to provide maternal antibodies to offspring and serves as a protection Receptor by rescuing endocytosed IgG and albumin from lysosomal degradation. Here we describe the generation of polarized Madin–Darby canine kidney (MDCK) cells expressing rat FcRn (rFcRn) to investigate the potential requirement for ligand bivalency in FcRn-mediated transport. The rFcRn-MDCK cells bind, internalize and bidirectionally transcytose the bivalent ligands IgG and Fc across polarized cell monolayers. However, they cannot be used to study FcRn-mediated transport of the monovalent ligand albumin, as we observe no specific binding, internalization or transcytosis of rat albumin. To address whether ligand bivalency is required for transport, the ability of rFcRn to transcytose and recycle wild-type Fc homodimers (wtFc; two FcRn-binding sites) and a heterodimeric Fc (hdFc; one FcRn-binding site) was compared. We show that ligand bivalency is not required for transcytosis or recycling, but that wtFc is transported more efficiently than hdFc, particularly at lower concentrations. We also demonstrate that hdFc and wtFc have different intracellular fates, with more hdFc than wtFc being trafficked to lysosomes and degraded, suggesting a role for avidity effects in FcRn-mediated IgG transport.
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COMPUTATIONAL DETERMINATION OF THE STRUCTURE OF RAT Fc BOUND TO THE Neonatal Fc Receptor
Journal of molecular biology, 1998Co-Authors: Zhiping Weng, Pamela J. Bjorkman, Daniel E. Vaughn, Kamalakar Gulukota, Charles DelisiAbstract:The available crystal structure for the complex between the Fc fragment of immunoglobulin G (IgG) and the Neonatal Fc Receptor (FcRn) was determined at low resolution and has no electron density for a large portion of the C_H2 domain of the Fc. Here, we use a well validated computational docking algorithm in conjunction with known crystallographic data to predict the orientation of C_H2 when bound to FcRn, and validate the predicted structure with data from site-specific mutagenesis experiments. The predicted Fc structure indicates that the C_H2 domain moves upon binding FcRn, such that the end-to-end distance of the bound Fc fragment is greater than it is in the crystal structure of isolated Fc. The calculated orientation of the bound C_H2 domain is displaced by an average of 6 A from the C_H2 orientation in the structure of Fc alone, and shows improved charge complementarity with FcRn. The predicted effects of 11 specific mutations in Fc and FcRn are calculated and the results are compared with experimental measurements. The predicted structure is consistent with all reported mutagenesis data, some of which are explicable only on the basis of our model. The current study predicts that FcRn-bound Fc is asymmetric due to reorientation of the C_H2 domain upon FcRn binding, a rearrangement that would be likely to interfere with optimal binding of FcRn at the second binding site of the Fc homodimer.
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Identification of critical IgG binding epitopes on the Neonatal Fc Receptor
Journal of molecular biology, 1997Co-Authors: Daniel E. Vaughn, Christina M Milburn, David M Penny, W.lance Martin, Jennifer L. Johnson, Pamela J. BjorkmanAbstract:The Neonatal Fc Receptor (FcRn) binds maternal immunoglobulin G (IgG) during the acquisition of passive immunity by the fetus or newborn. FcRn also binds IgG and returns it to the bloodstream, thus protecting IgG from a default degradative pathway. Biosensor assays have been used to characterize the interaction of a soluble form of rat FcRn with IgG, and demonstrate that FcRn dimerization and immobilization are necessary to reproduce in vivo binding characteristics. Here, we report the identification of several FcRn amino acid substitutions that disrupt its affinity for IgG and examine the effect of alteration of residues at the FcRn dimer interface. The role of these amino acids is discussed in the context of the previously reported structures of rat FcRn and a complex of FcRn with the Fc portion of IgG.
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High-Affinity Binding of the Neonatal Fc Receptor to Its IgG Ligand Requires Receptor Immobilization†
Biochemistry, 1997Co-Authors: Daniel E. Vaughn, Pamela J. BjorkmanAbstract:The Neonatal Fc Receptor (FcRn) binds maternal immunoglobulin G (IgG) during the acquisition of passive immunity by the fetus or newborn. In adult mammals, FcRn also binds IgG and returns it to the bloodstream, thus protecting IgG from a default degradative pathway. Biosensor assays have been used to characterize the interaction of a soluble form of FcRn with IgG. We use the statistical method of cross-validation to show that there are two classes of noninteracting binding sites, and these are sufficient to account for previously observed nonlinear Scatchard plots of FcRn/IgG binding data. We demonstrate that immobilization of FcRn on the biosensor surface reproduces the high-affinity IgG binding observed for membrane-bound FcRn, whereas immobilization of IgG results in lower affinity binding similar to that of the FcRn/IgG interaction in solution. The dependence of FcRn/IgG binding affinity on the coupled molecule provides further evidence in support of the previously hypothesized model that an FcRn dimer forms the high-affinity IgG binding site.
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crystal structure at 2 2 a resolution of the mhc related Neonatal Fc Receptor
Nature, 1994Co-Authors: Wilhelm P Burmeister, Louis N Gastinel, Neil E Simister, M Blum, Pamela J. BjorkmanAbstract:The three-dimensional structure of the rat Neonatal Fc Receptor (FcRn) is similar to the structure of molecules of the major histocompatibility complex (MHC). The counterpart of the MHC peptide-binding site is closed in FcRn, making the FcRn groove incapable of binding peptides. A dimer of FcRn heterodimers seen in the crystals may represent a Receptor dimer that forms when the Fc portion of a single immunoglobulin binds. An alternative use of the MHC fold for immune recognition is indicated by the FcRn and FcRn/Fc co-crystal structures.
Darrell Sleep - One of the best experts on this subject based on the ideXlab platform.
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Structure-based mutagenesis reveals the albumin-binding site of the Neonatal Fc Receptor.
Nature Communications, 2012Co-Authors: Jan Terje Andersen, Jason Cameron, Muluneh Bekele Daba, Leslie Evans, Stephan O. Brennan, Kristin Støen Gunnarsen, Bjørn Dalhus, Magnar Bjoras, Andrew Plumridge, Darrell SleepAbstract:Albumin transport proteins circulate in the blood and are protected from degradation by interaction with the Neonatal Fc Receptor. Andersen et al. investigate the albumin binding site of the Neonatal Fc Receptor and find pH sensitive ionic networks at the binding interface.
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Structure-based mutagenesis reveals the albumin-binding site of the Neonatal Fc Receptor
Nature Communications, 2012Co-Authors: Jan Terje Andersen, Jason Cameron, Muluneh Bekele Daba, Leslie Evans, Stephan O. Brennan, Kristin Støen Gunnarsen, Bjørn Dalhus, Magnar Bjoras, Andrew Plumridge, Darrell SleepAbstract:Albumin transport proteins circulate in the blood and are protected from degradation by interaction with the Neonatal Fc Receptor. Andersen et al . investigate the albumin binding site of the Neonatal Fc Receptor and find pH sensitive ionic networks at the binding interface. Albumin is the most abundant protein in blood where it has a pivotal role as a transporter of fatty acids and drugs. Like IgG, albumin has long serum half-life, protected from degradation by pH-dependent recycling mediated by interaction with the Neonatal Fc Receptor, FcRn. Although the FcRn interaction with IgG is well characterized at the atomic level, its interaction with albumin is not. Here we present structure-based modelling of the FcRn–albumin complex, supported by binding analysis of site-specific mutants, providing mechanistic evidence for the presence of pH-sensitive ionic networks at the interaction interface. These networks involve conserved histidines in both FcRn and albumin domain III. Histidines also contribute to intramolecular interactions that stabilize the otherwise flexible loops at both the interacting surfaces. Molecular details of the FcRn–albumin complex may guide the development of novel albumin variants with altered serum half-life as carriers of drugs.
Thomas Wileman - One of the best experts on this subject based on the ideXlab platform.
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characterization of the porcine Neonatal Fc Receptor potential use for trans epithelial protein delivery
Immunology, 2005Co-Authors: Catrina Stirling, Wayne I Lencer, Richard S Blumberg, Steven M Claypool, Bryan Charleston, Haru Takamatsu, Thomas WilemanAbstract:Summary The Neonatal Fc Receptor transports maternal immunoglobulin across the gut wall and has the potential to deliver genetically engineered proteins bearing immunoglobulin Fc domains across the gut to the mucosal immune system. Here we have characterized the porcine Neonatal Fc Receptor and tested its utility as a model system to study this kind of protein delivery. The complete DNA sequence obtained from an EST revealed 70–80% homology to mouse and human Receptors, respectively, and tyrptophan and di-leucine endocytosis motifs were identified in the cytoplasmic tail. Reverse transcription–polymerase chain reaction analysis showed expression of the Receptor mRNA in gut, liver, kidney and spleen tissue, aortic endothelial cells and monocytes. Pig kidney cell lines showed saturable pH-dependent binding and uptake of porcine immunoglobulin G (IgG) and also bovine, mouse and human IgG. Polyclonal antibodies raised against the Receptor immunoprecipitated a protein of 40 000 MW when the cDNA was expressed in cells and the Receptor required assembly with porcine β2-microglobulin for transport from the endoplasmic reticulum to recycling and early endosomes. Immunohistochemical analysis showed the Receptor expressed in epithelial cells of the gut of young and adult animals. The ability of the Receptor to deliver immunoglobulin across the gut was demonstrated by feeding piglets bovine colostrum as a source of bovine IgG. Bovine IgG was delivered into the pig circulation. Pigs express the Neonatal Fc Receptor and the Receptor has the potential to deliver protein antigens to the pig immune system.
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Characterization of the porcine Neonatal Fc Receptor—potential use for trans-epithelial protein delivery
Immunology, 2005Co-Authors: Catrina Stirling, Wayne I Lencer, Richard S Blumberg, Steven M Claypool, Bryan Charleston, Haru Takamatsu, Thomas WilemanAbstract:Summary The Neonatal Fc Receptor transports maternal immunoglobulin across the gut wall and has the potential to deliver genetically engineered proteins bearing immunoglobulin Fc domains across the gut to the mucosal immune system. Here we have characterized the porcine Neonatal Fc Receptor and tested its utility as a model system to study this kind of protein delivery. The complete DNA sequence obtained from an EST revealed 70–80% homology to mouse and human Receptors, respectively, and tyrptophan and di-leucine endocytosis motifs were identified in the cytoplasmic tail. Reverse transcription–polymerase chain reaction analysis showed expression of the Receptor mRNA in gut, liver, kidney and spleen tissue, aortic endothelial cells and monocytes. Pig kidney cell lines showed saturable pH-dependent binding and uptake of porcine immunoglobulin G (IgG) and also bovine, mouse and human IgG. Polyclonal antibodies raised against the Receptor immunoprecipitated a protein of 40 000 MW when the cDNA was expressed in cells and the Receptor required assembly with porcine β2-microglobulin for transport from the endoplasmic reticulum to recycling and early endosomes. Immunohistochemical analysis showed the Receptor expressed in epithelial cells of the gut of young and adult animals. The ability of the Receptor to deliver immunoglobulin across the gut was demonstrated by feeding piglets bovine colostrum as a source of bovine IgG. Bovine IgG was delivered into the pig circulation. Pigs express the Neonatal Fc Receptor and the Receptor has the potential to deliver protein antigens to the pig immune system.
