Biomedical subjects

C Ra

Publications and source records attributed to C Ra.

At least 109 records · Page 6Linked to original sources

PubMed1995

Interleukin-13 expression in the nasal mucosa of perennial allergic rhinitis.

Allergic rhinitis is an IgE mediated atopic disease characterized by elevated levels of allergen specific IgE antibodies that play a central role in mediating allergic reactions. Interleukin 13 (IL-13) is a novel T-cell-derived cytokine that shares several functional properties with IL-4 and has been demonstrated to be capable of inducing IgE synthesis. The present study was designed to investigate the expression of IL-13 gene in the epithelial compartment of the nasal mucosa of patients with perennial allergic rhinitis (PAR) to house dust mite, comparing it with that in the nasal epithelial compartment of chronic infectious rhinitis (CIR) patients and normal volunteers (NV). We also investigated the IL-13 gene expression in the peripheral blood of PAR patients. Nasal scrapings were collected from the inferior turbinate of patients undergoing conchotomy surgery and from outpatients, and the mRNA expression of IL-13 was analyzed by the RT-PCR method. Peripheral blood mononuclear cells were isolated by density-gradient centrifugation and the expression of IL-13 gene was examined by the RT-PCR method. IL-13 expression at protein level and its cell source were analyzed by immunohistochemistry of inferior turbinate biopsies. The levels of total serum IgE and allergen-specific IgE antibodies in the serum were estimated by the PRIST and CAP RAST method, respectively. IL-13 gene expression was detected in the epithelial compartment of the nasal mucosa of 18/19 PAR patients but was undetected in normal volunteers and CIR patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1994

Cloning of the cDNA for the deleted syk kinase homologous to ZAP-70 from human basophilic leukemia cell line (KU812).

Syk kinase is one of the protein tyrosine kinases and forms a family with ZAP-70. We isolated two different sized cDNA clones of syk (Syk11 and Syk41) from a cDNA library of human KU812 (human basophilic leukemia cell line). The obtained two clones carried different messages, that Syk41 had a 69 bp-long insertion between the SH2 domain and the kinase domain compared with Syk11. Alignment of the two human syk predicted polypeptides with those of the porcine syk and ZAP-70 revealed that human syk was 5 amino acid longer than the porcine syk at the N-termini and that the insertion of the 23 amino acid found in Syk41 was present in the porcine syk and absent in ZAP-70. Reverse transcribed polymerase chain reaction targeting this region showed that both forms of the polyA RNA were expressed in Jurkat cells, human peripheral leukocytes and also KU812 cells and that the inserted form was dominant.

Amino Acid Sequence↗

PubMed1994

High-level expression of the truncated alpha chain of human high-affinity receptor for IgE as a soluble form by baculovirus-infected insect cells. Biochemical characterization of the recombinant product.

The binding subunit of human high-affinity receptor for IgE (Fc epsilon RI alpha) was efficiently expressed as a truncated form in insect cells. The soluble (s)Fc epsilon RI alpha purified from culture medium by affinity chromatography with an anti-(alpha chain) mAb was nearly homogeneous and had an IgE-binding activity. The amino acid composition and the revealed N-terminal amino acid sequence of sFc epsilon RI alpha suggested that it was properly processed in insect cells. The apparent molecular mass (35 kDa) of purified sFc epsilon RI alpha was smaller than that of sFc epsilon RI alpha produced by CHO transfectants. The reduction of the apparent molecular mass after N-glycanase treatment showed the recombinant product was N-glycosylated. Peptide mapping of native and deglycosylated sFc epsilon RI alpha indicated that three Asn residues (Asn21, Asn42 and Asn166) should be almost fully glycosylated, and that two Asn residues (Asn74 and Asn135) were partially glycosylated.

Amino Acid Sequence↗

PubMed1994

Fibronectin receptor integrins are involved in mast cell activation.

Mast cells express fibronectin-receptor integrins on the cell surface, which are involved in cellular activation. In this study rat and mouse mast cells adhered to fibronectin through very late antigen 4, 5 (beta 1 integrin) and vitronectin receptor (beta 3 integrin), and engagement of these receptors promoted cellular degranulation induced by cross-linking of the high-affinity IgE receptor. Blocking of these adhesion molecules by monoclonal antibodies remarkably reduced passive cutaneous anaphylaxis reaction in vivo. On fibronectin, cytokine release from mast cells on IgE receptor aggregation was also enhanced, but not the expression of cytokine genes, with the exception of interleukin-3. Interleukin-3 gene expression was constitutively observed in mouse-cultured mast cells and significantly increased on fibronectin with a prolonged survival of the cells, suggesting that the autocrine or paracrine system of interleukin-3 secretion contributes to the prolonged survival of mast cells on fibronectin. Our findings presented here clearly indicate that the engagement of fibronectin-receptor integrins on mast cells increases the sensitivity of the cells for cellular activation. Taking into consideration the fact that mast cells in the microenvironment are actually surrounded by other cells and extracellular matrix proteins, we identified significant roles of adhesion molecules on mast cells in the allergic state, and we hope to develop new strategies to manipulate these molecules for medical intervention in allergy.

Animals↗

PubMed1994

Association between atopy and variants of the beta subunit of the high-affinity immunoglobulin E receptor.

The beta-subunit of the high-affinity IgE receptor (Fc epsilon RI-beta) on chromosome 11 is maternally linked to atopy, the state of enhanced IgE responsiveness underlying allergic asthma and rhinitis. We have identified a common variant of Fc epsilon RI-beta, lle181Leu within the 4th transmembrane domain. Leu181 shows significant association with positive IgE responses in a random patient sample. Amongst 60 unrelated nuclear families with allergic asthmatic probands, Leu181 is identified in 10 (17%), is maternally inherited in each, and shows a strong association with atopy. Our data indicate that Fc epsilon RI-beta, subject to maternal modification, may be the atopy-causing locus on chromosome 11q.

Amino Acid Sequence↗

PubMed1994

Recombinant soluble form of the human high-affinity immunoglobulin E (IgE) receptor inhibits IgE production through its specific binding to IgE-bearing B cells.

A recombinant soluble form of the alpha subunit of the human high-affinity receptor for IgE (rsFc epsilon RI alpha), one of the potent IgE-binding molecules, was tested for its ability to regulate IL-4-induced IgE synthesis by human lymphocytes. Addition of rsFc epsilon RI alpha to cultures induced a dose-dependent inhibition of the T cell-dependent and independent synthesis of IgE. The suppression of IgE synthesis was observed at the protein and the mRNA levels, and it was IgE class specific. By flow cytometry, specific binding of rsFc epsilon RI alpha was detected on surface IgE-bearing B cells as well as on U266 cells, and it was completely blocked by preincubation with IgE. rsFc epsilon RI alpha bound to the cell surface IgE could be effectively dissociated not only by a large excess of IgE, but also by an anti-rsFc epsilon RI alpha mAb that competes with IgE for the binding to rsFc epsilon RI alpha. This mAb abolished the rsFc epsilon RI alpha-mediated suppression of IgE synthesis. These data suggest that rsFc epsilon RI alpha may have a function in selectively suppressing IgE synthesis through its interaction with the membrane-bound form of IgE.

Adult↗

PubMed1993

Localisation of atopy and beta subunit of high-affinity IgE receptor (Fc epsilon RI) on chromosome 11q.

Atopy, a common familial syndrome underlying allergic asthma and rhinitis, is characterised by sustained immunoglobulin E (IgE) responses to common allergens. We have previously shown genetic linkage of atopy to the chromosome 11q13 marker D11S97 (pms51) through maternally derived alleles, but no likely candidate genes were known to lie near this marker. We have analysed maternally derived alleles from 155 sibling-pairs affected by atopy to seek evidence of linkage between the gene predisposing to atopy and other markers on chromosome 11q13. We found that the beta subunit of the high-affinity receptor for IgE (Fc epsilon RI-beta) also lies on chromosome 11q13, and that it is in close genetic linkage with the gene for atopy. The known roles of Fc epsilon RI in antigen-induced mast-cell degranulation and in the release of cytokines that enhance IgE production make the gene for its beta subunit a candidate for the chromosome 11 atopy locus.

Chromosome Mapping↗

PubMed1993

Soluble human high-affinity receptor for IgE abrogates the IgE-mediated allergic reaction.

The high-affinity receptor for IgE (Fc epsilon RI) has a tetrameric structure structure composed of one alpha, one beta, and two disulfide-linked gamma subunits, of which the alpha subunit binds IgE with high affinity. A recombinant soluble form of the ectodomain of the human Fc epsilon RI alpha subunit (rsFc epsilon RI alpha) was recently generated by gene engineering and was verified to bind IgE with an affinity as high as that of native Fc epsilon RI on the cell surface. rsFc epsilon RI alpha was prepared on a large scale in order to analyze its biological function. rsFc epsilon RI alpha completely inhibited IgE binding to the cell surface, resulting in abrogation of the chemical mediator release from RBL-2H3 cells. Furthermore it completely abolished the passive cutaneous anaphylaxis (PCA) response by trapping IgE specifically when it was administered into rats prior to IgE sensitization. Even after IgE sensitization, treatment of rsFc epsilon RI alpha substantially reduced the PCA response. It was finally shown that rsFc epsilon RI alpha inhibited IgE binding to human peripheral blood basophils and the histamine release from them. In this paper we address the ability of rsFc epsilon RI alpha to specifically prevent the IgE-mediated allergic reaction.

Animals↗

PubMed1993

TCR isoform containing the Fc receptor gamma chain exhibits structural and functional differences from isoform containing CD3 zeta.

The structure and function of the TCR-CD3 complex containing a homodimer of the gamma chain of the high affinity receptor for IgE (FcR gamma) (FcR gamma+ TCR) was investigated by transfecting the FcR gamma gene into a CD3 zeta-, CD3 eta-, FcR gamma- T cell line. Introduction of FcR gamma, as well as CD3 zeta, induced a high expression of the TCR-CD3 complex on the cell surface. Transfected FcR gamma formed a homodimer and associated firmly with the TCR alpha beta dimer but only weakly with the CD3 gamma delta epsilon. Stimulation of both FcR gamma and CD3 zeta transfectants by antibodies against TCR or CD3 induced accumulation of inositol phosphates, the Ca2+ response, IL-2 production, and growth inhibition. On the other hand, antigen stimulation of transfectants expressing FcR gamma as well as CD3 zeta induced IL-2 production, but only the latter exhibited the antigen-induced growth inhibition. In vitro kinase assay suggested that the CD3 zeta dimer but not the FcR gamma dimer associates with the Fyn kinase. These results indicate that the FcR gamma homodimer is able to form a functional TCR complex but that the mode of assembly and the signaling function of FcR gamma+ TCR, including its association with tyrosine kinase(s), may differ from the TCR-CD3 complex containing CD3 zeta homodimers (zeta+ TCR). This provides an example which illustrates that different TCR isoforms mediate distinct signals and functions.

Animals↗

PubMed1991

The high-affinity receptor for immunoglobulin E: a target for therapy of allergic diseases.

The high-affinity receptor for IgE (Fc epsilon RI) on mast cells and basophils is a tetrameric complex, alpha beta gamma 2. Here we summarize the latest developments on the structure and function of this receptor. By genetic transfer, we have engineered a cell line secreting substantial amounts of a peptide containing exclusively the extracellular domain of the alpha-subunit. This domain by itself is sufficient to mediate high-affinity binding of IgE. Glycosylation and the presence of the other subunits are not necessary for the binding function. The gamma-subunit of Fc epsilon RI is part of other receptors such as Fc gamma RIII and the T cell receptor, and therefore is likely to play an important although still undefined functional role. A detailed knowledge of how the receptor interacts with IgE and induces cellular degranulation may lead to the design of new therapeutic approaches to allergic diseases. The potential strategies are discussed.

Animals↗

PubMed1989

A macrophage Fc gamma receptor and the mast cell receptor for IgE share an identical subunit.

Fc receptors for immunoglobulins are found on many immune cells and trigger essential functions of the immune defence system. With the exception of the high-affinity receptor for immunoglobulin E (Fc epsilon RI), these receptors were thought to consist of single polypeptides. Fc epsilon RI is a tetrameric complex of one alpha-subunit, one beta-subunit and two gamma-subunits. Here we report the cloning of a polypeptide identical to the gamma-chains of Fc epsilon RI, from mouse macrophages that do not express this receptor. Biosynthetic labelling and gene transfer together show that these gamma-chains associate with one of the macrophage receptors (Fc gamma RIIa). The human homologue, Fc gamma RIII (CD16), from natural killer cells is also expected to associate with gamma-chains. It is possible that these gamma-chains and the homologous zeta-chains of the T-cell antigen receptor belong to a new family of related proteins which share a common role in the signal transducing pathway.

Animals↗

PubMed1989

Complete structure of the mouse mast cell receptor for IgE (Fc epsilon RI) and surface expression of chimeric receptors (rat-mouse-human) on transfected cells.

The high affinity receptor for IgE (Fc epsilon RI) found on mast cells and basophils is a tetrameric complex of a single alpha subunit, a single beta subunit, and two identical gamma subunits. The genes for the three subunits of mouse Fc epsilon RI have now been cloned from the mast cell line, PT18. When compared at the DNA level, the rat and mouse subunits are similarly conserved. However, at the protein level the homology between mouse and rat alpha is surprisingly low (71% identities) especially in the cytoplasmic regions (57% identities) which are of different length (25 and 20 residues, respectively). By contrast the beta and gamma are homogeneously conserved between mouse and rat (83 and 93% identities, respectively). The consensus amino acid sequence of the alpha subunit derived from three species (rat, mouse, and human) shows that the cytoplasmic tail diverges to the same extent as the leader peptide. Conversely, the transmembrane domain of the alpha is highly conserved and contains 10 consecutive residues that are identical. Comparisons between mouse Fc epsilon RI and other mouse proteins reveal regions of high homology between the alpha subunit and Fc gamma RIIa and between the gamma subunit and the zeta chain of the T cell receptor. Cells transfected with the alpha gene express the alpha subunit on their surface very inefficiently. Efficient expression is only achieved after co-transfection of the three rodent genes or of the human alpha gene together with the rodent gamma without apparent need for beta. The subunits are completely interchangeable upon transfection so that various chimeric mouse-rat-human receptors can be expressed.

Amino Acid Sequence↗

PubMed1989

Complete structure and expression in transfected cells of high affinity IgE receptor.

The high-affinity receptor for immunoglobulin E, Fc epsilon RI, is found exclusively on mast cells and basophils. When multivalent allergens bind to the receptor-bound IgE, the consequent aggregation of the receptors leads to the release of mediators responsible for allergic symptoms. In rodents Fc epsilon RI is a tetrameric complex of non-covalently attached subunits: one IgE-binding alpha subunit, one beta subunit and a dimer of disulphide-linked gamma subunits. Complementary DNA encoding the alpha and the beta subunits has recently been isolated, but expression of IgE-binding by transfected cells has not yet been achieved. Here we report the cloning of cDNA for the gamma subunit, and propose a model for the alpha beta gamma 2 tetramer which accounts for many of the structural features of the receptor. The rodent receptor on the surface of COS 7 cells was expressed only when the cDNAs for all three subunits were cotransfected. Successful expression of human IgE receptors should now be possible, eventually to permit the detailed analysis of the human IgE-receptor interaction and assist the search for therapeutically effective inhibitors.

Amino Acid Sequence↗

PubMed1989

Internalization of IgE receptors on rat basophilic leukemic cells by phorbol ester. Comparison with endocytosis induced by receptor aggregation.

Phorbol myristate acetate (PMA) can induce a rapid and significant decrease in the expression of IgE receptors on RBL-2H3 cells. Fluorescence microscopy confirmed that the down-regulation is due to internalization of receptors. The endocytotic response to PMA shares several characteristics with endocytosis induced by immunochemical aggregation of surface-bound monomeric IgE: the rates of internalization both have a t1/2 of about 5 min, a maximum of 35% of the surface-bound IgE can be endocytosed by the action of PMA (50% by receptor aggregation), endocytosis is sustained for at least up to 60 min, neither stimulus requires extracellular Ca2+ and endocytosis induced by either stimulus is an active process, i.e., is dependent on temperature and cellular energy. Biochemical studies revealed some differences between the endocytotic responses to the two stimuli. After prolonged treatment of cells with dexamethasone, only endocytosis induced by PMA is inhibited. Cells depleted of protein kinase C by prolonged exposure to PMA can sustain a significant endocytotic response to aggregation of IgE receptors, but become completely desensitized to PMA. These data suggest that different biochemical pathways mediate the signals from the two stimuli and that protein kinase C is directly involved in endocytosis induced by PMA but does not have a major role in endocytosis induced by receptor aggregation.

Animals↗

PubMed1989

Differentiation in dose-response curves of airway responsiveness to inhaled methacholine between asthmatics and nonasthmatics.

We compared the discriminative capacity of the parameters obtained from dose-response curves of airway resistance (Raw) to inhaled methacholine (i.e., threshold dose, slope, and maximal increase in Raw) to differentiate asthmatics from nonasthmatics. Of the three parameters, maximal increase in Raw most accurately differentiated asthmatics from nonasthmatics (% correctness was 86% in asthmatics). Furthermore, an index consisting of both threshold dose and slope more clearly differentiated asthmatics from nonasthmatics (% correctness was 94% in asthmatics) than either threshold dose or slope alone (% correctness was 68% and 54% in asthmatics, respectively). We conclude, that of the three parameters, the maximal increase in Raw or an index consisting of both threshold dose and slope is the most discriminative index in asthmatics.

Adolescent↗

PubMed1989

The receptor with high affinity for IgE.

The cDNAs for each of the three types of polypeptide that form the high affinity IgE receptor have been cloned and sequenced. Analysis of the predicted amino acid sequence and other data suggests that the four-chained structure (alpha beta gamma 2) contains seven transmembrane segments. The alpha chain resembles the immunoglobulin-binding chain found in other Fc receptors, but the beta and gamma chain sequences do not resemble other known proteins. (The one exception: the transmembrane segment of the gamma chains, which is homologous to the corresponding segment of the zeta chain of the CD3 complex found on T lymphocytes). Efficient expression of IgE binding by the rat receptor in COS cells was observed only when the coding sequences for each of the three chains were co-transfected. So far, only the cDNA for the human alpha chain has been successfully cloned. We attempted to express this chain by co-transfecting its cDNA with those for the rat beta and gamma chains. Surprisingly, co-transfection with the cDNA for the gamma chain was sufficient, although when the beta and gamma chains were both co-transfected, expression of alpha beta gamma oligomers was evident. Approaches being used to define by genetic manipulation the functional role of various parts of the receptor are discussed.

Animals↗

PubMed1989

Emerging picture of the receptor with high affinity for IgE.

The cDNAs for two of the subunits of the receptor with high affinity for IgE have been isolated and sequenced. That for the IgE-binding alpha subunit predicts a polypeptide with a single transmembrane segment. The predicted extracellular amino terminal portion, comprised of 180 residues, is homologous to the corresponding region of Fc gamma receptors and contains two truncated immunoglobulin-like domains. The cDNA for beta predicts a peptide with four transmembrane segments, but its sequence is unrelated to known proteins. Experiments to isolate the cDNA for the gamma subunit have begun; when completed, cotransfection of the three genes will be attempted to get expression, a process that has not so far been successful for the individual subunits. Such expression will permit further analysis of the receptor's function and ultimately may provide information on how best to intervene clinically in the activation of mast cells and basophils.

Animals↗

PubMed1988

Isolation and characterization of cDNAs coding for the beta subunit of the high-affinity receptor for immunoglobulin E.

Among receptors that bind the Fc region of immunoglobulins ("Fc receptors"), only the one with high affinity for immunoglobulin E (IgE) is known to consist of more than a single polypeptide. In addition to the IgE-binding alpha chain, the receptor contains a single beta chain and two, disulfide-linked, gamma chains. From a cDNA library of a rat mucosal mast cell tumor, from which we recently cloned cDNAs coding for the alpha chain, we have now isolated cDNAs coding for the beta subunit. In vitro transcription-translation of the cDNA directed the synthesis of a polypeptide reactive with two distinctive anti-beta monoclonal antibodies and whose molecular weight was identical to that of authentic beta chains. Polyclonal antibodies to beta peptides expressed in Escherichia coli reacted with intact receptors and isolated beta chains. The gene encodes a protein of 243 residues with no leader sequence. A hydropathicity plot suggests that the polypeptide crosses the plasma membrane four times. The epitope recognized by one of the monoclonal antibodies was localized to the NH2 terminus; that by the other was localized to the COOH terminus. Since those antibodies react with membranes and not with intact cells, we suggest that both ends of the beta subunit are cytoplasmic. RNA transfer blots at high stringency failed to reveal mRNA for beta chains in a variety of cells (in particular, monocytes) that do not contain the high-affinity receptor for IgE.

Amino Acid Sequence↗