High-affinity Immunoglobulin Research Articles

FcεRI expression on monocytes in atopic disease: cause or effect?

Clinical & Experimental AllergyVolume 26, Issue 6 p. 616-617 Free Access FcεRI expression on monocytes in atopic disease: cause or effect? M. Larché, M. Larché Department of Allergy and Clinical Immunology National Heart and Eung Institute Dovehouse Street Eondon SW3 6EY UKSearch for more papers by this author M. Larché, M. Larché Department of Allergy and Clinical Immunology National Heart and Eung Institute Dovehouse Street Eondon SW3 6EY UKSearch for more papers by this author First published: June 1996 https://doi.org/10.1111/j.1365-2222.1996.tb00585.xCitations: 1AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. References 1 Lanzavecchia A. Antigen-specific interaction between T and B cells. Nature 1985; 314: 537– 9. 2 Corrigan CJ, Kay AB. The lymphocyte in asthma. In: Asthma and Rhinitis; W.W. Busse ST. Holgate, eds. Black-well Scientific Publications, Inc., Boston , 1995; Chapter 34: 450– 64. 3 Kehry MR, Yamashita LC. Low affinity IgE receptor (CD23)function on mouse B cells: Role in IgE-dependent antigen focusing. Proc. Natl Acad Sci USA 1989; 86: 7556– 60. 4 Pirron U, Schlunck T, Prinz JC, Rieber EP. IgE-dependent antigen focusing by human B lymphocytes is mediated by the low affinity receptor for IgE. Eur J Immunol 1990; 20: 1547– 51. 5 Mudde GC, Van Reijsen FC, Boland GJ et al. Allergen presentation by epidermal Langerhans' cells from patients with atopic dermatitis is mediated by IgE. Immunology 1990; 69: 335– 41. 6 Mudde GC, Bheeekha R, Bruijnzeel-Koomen CAFM. Consequences of IgE/CD23–mediated antigen presentation in allergy. Immunol Today 1995; 16: 380– 3. 7 Ravetch JV, Kinet, J-P. Fc receptors. Annu Rev Immunol 1991; 9: 457– 92. 8 Wang B, Rieger A, Kilgus O et al. Epidermal Langerhans' cells from normal human skin bind monomerie IgE via FcεRI. J Exp Med 1992; 175: 1353– 65. 9 Bieber T, de la Salle H, Wollenberg A et al. Human epidermal Langerhans' cells express the high affinity receptor for immunoglobulin E (FcεRI). J Exp Med 1992; 175: 1285– 90. 10 Soussi Gounni A, Lamkhioued B, Oehiai K et al. High-affinity IgE receptor on eosinophils is involved in defence against parasites. Nature 1994; 367: 183– 6. 11 Maurer D, Fiebiger E, Reininger B et al. Expression of high affinity immunoglobulin E receptors (FcεRI) on monoeytes from atopic individuals. J Exp Med 1994; 179: 745– 50. 12 Jurgens M, Wollenburg A, Hanau D, de la Salle H, Beiber T. Activation of human epidermal Langerhans' cells by engagement of the high affinity receptor for IgE, FcεRI. J Immunol 1995; 155: 5184– 9. 13 Takenada M, Tanaka Y, Yoshida H, Ra C. High affinity IgE receptor–mediated prostaglandin E2 production by monocytes in atopic dermatitis. Int Arch Allergy Immunol 1995; 108: 247– 53. 14 Maurer D, Ebner C, Reininger B et al. The high affinity IgE receptor (FcεRI) mediates IgE–dependent allergen presentation. J Immunol 1995; 154: 6285– 90. 15 Gauehat, J-F., Henehoz S, Mazzei G et al. Induction of human IgE synthesis in B cells by mast cells and basophils. Nature 1993; 365: 340– 3. 16 Wilkinson J, Holgate ST. Candidate gene loci in asthmatic and allergic inflammation. Thorax 1996; 51: 3– 8. 17 ReischI IG, Corvaia N, Effenberger F, Wolff-Winiski B, Kromer E, Mudde GC. Function and regulation of FcεRI expression on monocytes from non–atopic donors. Clin Exp Allergy 1996; 26: 630– 41. Citing Literature Volume26, Issue6June 1996Pages 616-617 ReferencesRelatedInformation

Dendritic cells in normal and asthmatic airways: expression of the α subunit of the high affinity immunoglobulin E receptor (FcεRI‐α)

SummaryBackground Immunoglobulin E (IgE) plays an important role in asthma, with total serum IgE levels closely related to both clinical expression of the disease and airway hyperresponsiveness. IgE binds to a high affinity cell‐surface receptor (FcεRI) which is present on mast cells and which has also recently been demonstrated on cutaneous dendritic cells. If pulmonary dendritic cells were also able to express this receptor, this would have important implications with regard to their potential role in asthma.Objectives The aims of the study were to investigate the expression of the α subunit of the high affinity IgE receptor (FcεRI‐α) in normal and asthmatic airways, and to analyse its cellular provenance with particular emphasis on the dendritic cell.Methods Bronchial biopsy specimens were obtained using fibreoptic bronchoscopy from 10 atopic asthmatics and nine non‐atopic non‐asthmatic control subjects. Specimens were processed into glycolmethacrylate resin and analysed by immunohistochemistry using specific monoclonal antibodies against FcεRI‐α. and against tryptase and CDla. markers for mast cells and dendritic cells, respectively.Results The numbers of dendritic cells were significantly higher in the airways of asthmatics compared with those of control subjects (P<0.02). Analysis of sequential sections revealed that the α subunit of FcεRI was localized to both mast eells and dendritic cells. The proportion of dendritic cells expressing FcεRI‐α was significantly inereased in the asthmatic group (P < 0.003).Conclusion These results support the hypothesis that dendritic cells play an important role in allergic asthma although the functional significance of FcεRI‐α expression needs further investigation.

Protein tyrosine kinases in activation signal of human basophils through the immunoglobulin E receptor type I

Human basophils activated through high-affinity immunoglobulin E (IgE) receptors (Fc epsilon RI) are involved in the late phase of the allergic reaction. To investigate the possible involvement of protein-tyrosine kinases in this activation we used human acute basophilic leukemia (ABL) cells in culture as well as a pure population of normal basophils in vitro-derived from human bone marrow precursor cells (HBMB). ABL cells were 50-80% basophils at various stages of maturation as assessed by staining, morphology, ultrastructure, and flow cytometry analysis, and only basophils in ABL cells expressed Fc epsilon RI. Aggregation of Fc epsilon RI by IgE and anti-IgE, IgE and antigen, or anti-Fc epsilon RI monoclonal antibodies on ABL cells or on HBMB, led to increased tyrosine phosphorylation of 120-, 100-, 80-, 72-, 50- to 65-, and 38-kDa substrates. Tyrosine phosphorylations in ABL cells were in basophils because 1) they were detected after a 5-s stimulation, 2) they were observed under conditions where mediator release is minimal, i.e., in the absence of extracellular calcium, 3) hapten addition during antigen stimulation resulted in almost total disappearance of tyrosine phosphorylations within 30 s. There was correlation between histamine release and tyrosine phosphorylation in anti-IgE dose-responses and in dose-responses of the tyrosine kinase inhibitor genistein. The tyrosine kinase p72syk was detected in the cells. Stimulation of ABL cells for 1 min resulted in extracellular calcium-independent tyrosine phosphorylation and activation of p72syk. Therefore, tyrosine kinases are involved in the early steps of human Fc epsilon RI signaling in basophils. Tyrosine kinases and their substrates could represent new potential therapeutic targets to prevent the development of the allergic reaction.

Identification of a Committed Precursor for the Mast Cell Lineage

Mast cells originate from hematopoietic stem cells, but the mast cell-committed precursor has not been identified. In the study presented here, a cell population in murine fetal blood that fulfills the criteria of progenitor mastocytes was identified. It is defined by the phenotype Thy-1loc-Kithi, contains cytoplasmic granules, and expresses RNAs encoding mast cell-associated proteases but lacks expression of the high-affinity immunoglobulin E receptor. Thy-1loc-Kithi cells generated functionally competent mast cells at high frequencies in vitro but lacked developmental potential for other hematopoietic lineages. When transferred intraperitoneally, this population reconstituted the peritoneal mast cell compartment of genetically mast cell-deficient W/Wv mice to wild-type levels.

Transgenic mice expressing the human high-affinity immunoglobulin (Ig) E receptor alpha chain respond to human IgE in mast cell degranulation and in allergic reactions.

The high-affinity receptor for immunoglobulin (Ig) E (Fc epsilon RI) on mast cells and basophils plays a key role in IgE-mediated allergies. Fc epsilon RI is composed of one alpha, one beta, and two gamma chains, which are all required for cell surface expression of Fc epsilon RI, but only the alpha chain is involved in the binding to IgE. Fc epsilon RI-IgE interaction is highly species specific, and rodent Fc epsilon RI does not bind human IgE. To obtain a "humanized" animal model that responds to human IgE in allergic reactions, transgenic mice expressing the human Fc epsilon RI alpha chain were generated. The human Fc epsilon RI alpha chain gene with a 1.3-kb promoter region as a transgene was found to be sufficient for mast cell-specific transcription. Cell surface expression of the human Fc epsilon RI alpha chain was indicated by the specific binding of human IgE to mast cells from transgenic mice in flow cytometric analyses. Expression of the transgenic Fc epsilon RI on bone marrow-derived mast cells was 4.7 x 10(4)/cell, and the human IgE-binding affinity was Kd = 6.4 nM in receptor-binding studies using 125I-IgE. The transgenic human Fc epsilon RI alpha chain was complexed with the mouse beta and gamma chains in immunoprecipitation studies. Cross-linking of the transgenic Fc epsilon RI with human IgE and antigens led to mast cell activation as indicated by enhanced tyrosine phosphorylation of the Fc epsilon RI beta and gamma chains and other cellular proteins. Mast cell degranulation in transgenic mice could be triggered by human IgE and antigens, as demonstrated by beta-hexosaminidase release in vitro and passive cutaneous anaphylaxis in vivo. The results demonstrate that the human Fc epsilon RI alpha chain alone not only confers the specificity in human IgE binding, but also can reconstitute a functional receptor by coupling with the mouse beta and gamma chains to trigger mast cell activation and degranulation in a whole animal system. These transgenic mice "humanized" in IgE-mediated allergies may be valuable for development of therapeutic agents that target the binding of IgE to its receptor.

Mast cells lacking the high affinity immunoglobulin E receptor are deficient in Fc epsilon RI gamma messenger RNA.

A population of cells that express mast cell markers, including the membrane protein p161, but that lack expression of the high affinity IgE receptor, Fc epsilon RI, can be routinely grown from bone marrow. Ionomycin, but not IgE immune complexes, causes these cells to release serotonin and to express IL-3 and IL-13 mRNA, consistent with their being FC epsilon RI-deficient mast cells. These p161+/Fc epsilon RI- mast cells expressed normal amounts of Fc epsilon RI alpha and beta chain mRNA, but extremely low levels of Fc epsilon RI gamma chain mRNA. In addition, this novel mast cell population expressed CD3 zeta chain mRNA, which p161+/Fc epsilon RI+ mast cells did not. CD3 zeta stable transfectants of Abelson-murine leukemia virus-transformed p161+/Fc epsilon RI+ mast cells continued to express Fc epsilon RI. This strongly suggests that the failure of p161+/Fc epsilon RI- mast cells to express IgE receptors was not caused by the presence of CD3 zeta chain. Transfection of human Fc epsilon RI gamma cDNA into p161+/Fc epsilon RI- mast cells rescued IgE binding. These stable transfectants released serotonin in response to cross-linkage of Fc epsilon RI, demonstrating that the molecular defect of p161+/Fc epsilon RI- mast cells is indeed the loss of Fc epsilon RI gamma expression.

Activation of the high-affinity immunoglobulin E receptor Fc epsilon RI in RBL-2H3 cells is inhibited by Syk SH2 domains.

Antigen-mediated aggregation of the high-affinity receptor for immunoglobulin E, Fc epsilon RI, results in the activation of multiple signaling pathways, leading to the release of mediators of the allergic response. One of the earliest responses to receptor stimulation is the tyrosine phosphorylation of the beta and gamma subunits of Fc epsilon RI and the association of the tyrosine kinase Syk with the phosphorylated receptor. This association is mediated by the SH2 domains of Syk and is believed to be critical for activating signaling pathways resulting in mediator release. To examine the importance of the interaction of Syk with Fc epsilon RI in signaling events following receptor activation, we introduced a protein containing the SH2 domains of Syk into streptolysin O-permeabilized RBL-2H3 cells. The Syk SH2 domains completely inhibited degranulation and leukotriene production following receptor aggregation, and they blocked the increase in protein tyrosine phosphorylation observed after receptor activation. Inhibition was specific for Fc epsilon RI-mediated signaling, since degranulation of cells activated by alternative stimuli was not blocked by the Syk SH2 domains. A protein containing a point mutation in the carboxy-terminal SH2 domain which abolishes phosphotyrosine binding was not inhibitory. In addition, inhibition of degranulation was reversed by pretreatment of the SH2 domains with a tyrosine phosphorylated peptide corresponding to the tyrosine-based activation motif found in the gamma subunit of Fc epsilon RI, the nonphosphorylated peptide had no effect. The association of Syk with the tyrosine-phosphorylated gamma subunit of the activated receptor was blocked by the Syk SH2 domains, and deregulation in cells activated by clustering of Syk directly without Fc epsilon RI aggregation was not affected by the Syk SH2 domains. These results demonstrate that the association of Syk with the activated Fc epsilon RI is critical for both early and late events following receptor activation and confirm the key role Syk plays in signaling through the high-affinity IgE receptor.

Glycosylation of Human Truncated Fc∊RI α Chain Is Necessary for Efficient Folding in the Endoplasmic Reticulum

The high affinity immunoglobulin E (IgE) receptor is an alpha beta gamma 2 tetrameric complex. The truncated extracellular segment (alpha t) of the heavily glycosylated alpha chain is sufficient for high affinity binding of IgE. Here we have expressed various alpha t mutants in eukaryotic and prokaryotic cells to analyze the role of glycosylation in the folding, stability, and secretion of alpha t. All seven N-linked glycosylation sites in alpha t are glycosylated and their mutations have an additive effect on the folding and secretion of alpha t. Mutation of the seven N-glycosylation sites (delta 1-7 alpha t) induces misfolding and retention of alpha t in the endoplasmic reticulum. Similarly, tunicamycin treatment reduces substantially the folding efficiency of wild-type alpha t. In contrast, no difference in folding efficiency is detected between wild-type alpha t and delta 1-7 alpha t expressed in Escherichia coli. In addition, maturation of N-linked oligosaccharides and addition of O-linked carbohydrates are not required for either the transport or the IgE-binding function of alpha t. Furthermore, complete enzymatic deglycosylation does not affect the stability and the IgE-binding capacity of alpha t. Therefore, glycosylation is not intrinsically necessary for proper folding of alpha t but is required for folding in the endoplasmic reticulum. Our data are compatible with the concept that specific interactions between N-linked oligosaccharides and the folding machinery of the endoplasmic reticulum are necessary for efficient folding of alpha t in eukaryotic cells.

Human CC10 gene expression in airway epithelium and subchromosomal locus suggest linkage to airway disease.

The CC10 gene encodes the Clara cell 10-kDa protein, which is expressed in airway epithelial cells. Quantification of CC10 gene expression in freshly isolated human proximal airway epithelial cells demonstrated very high mRNA levels, approximately fivefold greater than gamma-actin mRNA, and in situ hybridization localized CC10 mRNA to nonciliated airway epithelial cells. Sequence analysis demonstrated that the human CC10 gene is comprised of three short exons separated by a long first and short second intron, and with a 5' flanking region typical of a regulated gene. Three Alu repeats were observed in intron 1 and one in intron 2. Two polymorphic regions within the introns were identified. First, a microsatellite was localized 5' to the third Alu repeat in intron 1 with a variable number of 4- and 5-base pair (bp) repeats and a heterozygosity of 0.71. Second, in 3% of the 168 chromosomes examined, there was the insertion of a human-specific Alu repeat in intron 2, 45 bp 3' to the exon 2-intron junction. In three Centre d'Etude du Polymorphisme Humain families, meiotic breakpoint analysis using these two polymorphic loci localized the CC10 gene to 11 p12-q13 between markers D11S16 and D11S97, a region recently linked to atopy and to the beta-subunit of the high-affinity immunoglobulin E receptor. The observations in the present study of high-level expression of the CC10 gene in the epithelium of conducting airways and a subchromosomal localization of the gene to a region potentially linked to inflammatory airway disease, together with the reported anti-inflammatory and immune-modulating properties of the protein, suggest the CC10 gene product may be important in modulating inflammation within the airways. If so, the highly heterozygous microsatellite described in the present study should facilitate analysis of a possible linkage of the CC10 gene with an inherited susceptibility to asthma.

Different roles for the Fc epsilon RI gamma chain as a function of the receptor context.

The high affinity immunoglobulin E receptor (Fc epsilon RI) and the B and T cell antigen receptors (TCR) are multimeric complexes containing subunits with cytoplasmic antigen recognition activation motifs (ARAMs). The presence of multiple motifs may be a way to amplify a single signal or provide independent activation modules. Here we have compared the signaling capacity of the same Fc epsilon RI gamma motif in the context of two different receptors, Fc epsilon RI and TCR/CD3, simultaneously reconstituted on the surface of the same zeta-deficient T cell line. Both reconstituted receptors mediate early (phosphorylation) and late (interleukin [IL]-2 release) signals. Mutation of the two tyrosine residues of ARAM gamma alters early signaling by both receptors, but the set of substrates phosphorylated via ARAM gamma is different for each receptor and is thus dependent on the receptor context. Furthermore, the mutations prevent Fc epsilon RI- but not TCR/CD3-mediated IL-2 release. These data demonstrate that ARAM gamma is necessary for allowing both receptors to phosphorylate the complete set of substrates, and that the CD3 complex, unlike the Fc epsilon RI beta chain, contains activation modules capable of compensating for the absence of a functional ARAM gamma in generating late signals such as IL-2 release.

Modulation of tumour necrosis factor-alpha mRNA levels by interferons in different populations of mast cells.

Tumour necrosis factor alpha (TNF-α) is a multipotent cytokine1 which can be produced by mast cells2 (MC). Given the regulatory roles of interferons (IFN) and the ability of IFN to potentiate TNF-α activity of macrophages3 we previously studied the effects of IFN on MC TNF-α activity.4 In contrast with effects on macrophages, IFN-α/β and IFN-γ inhibited TNF-α activity of mast cells. Thus, we analyzed the effects of IFN-α/β and IFN-γ on MC mRNA expression for TNF-α, high affinity immunoglobulin E receptor-alpha chain (FcERI-α chain), 2’5’ oligo adenylate synthetase (2’5’OAS) and β-actin.

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.

Physical and functional association of the high affinity immunoglobulin G receptor (Fc gamma RI) with the kinases Hck and Lyn.

The high affinity immunoglobulin G (IgG) receptor Fc gamma RI (CD64) is expressed constitutively on monocytes and macrophages, and is inducible on neutrophils. Fc gamma RI has recently been shown to be associated with the signal transducing gamma subunit of the high-affinity IgE receptor (Fc epsilon RI gamma). Induction of cytoplasmic protein tyrosine phosphorylation by Fc gamma RI cross-linking is known to be important in mediating Fc gamma RI-coupled effector functions. Recently, syk has been implicated in this role. We now report that the src-type kinases hck and lyn are physically and functionally associated with Fc gamma RI. Hck and lyn coimmunoprecipitated with Fc gamma RI from detergent lysates of normal human monocytes and of the monocytic line THP-1. Hck and lyn showed rapidly increased phosphorylation and increased exogenous substrate kinase activity after cross-linking of Fc gamma RI. These results demonstrate both physical and functional association of the Fc gamma RI/Fc epsilon RI gamma receptor complex with hck and lyn, and suggest a potential signal transducing role for these kinases in monocyte/macrophage activation.

Leukocyte common antigen (CD45) is required for immunoglobulin E-mediated degranulation of mast cells.

We demonstrate using primary mast cell cultures derived from wild-type and CD45-deficient mice that mast cell triggering through the high-affinity immunoglobulin E (IgE) receptor requires the cell surface tyrosine phosphatase CD45. Unlike wild-type cells, cross-linking of surface-bound IgE in mast cells deficient in CD45 does not induce degranulation. Degranulation in these mutant cells does occur after treatment with the calcium ionophore A23187 indicating that the degranulation machinery is intact in these cells. We also demonstrate that the tyrosine phosphatase inhibitors orthoVanadate and perVanadate inhibit degranulation in wild-type mast cells, as does cross-linking of CD45 by anti-CD45 antibodies. Finally, we show that CD45-deficient mice are resistant to IgE-dependent systemic anaphylaxis. These results show that, like the T cell receptor and the antigen receptor on B cells, there is an absolute requirement for CD45 in signaling via the high affinity IgE receptor, expanding the number of receptors for which CD45 is an essential component.

CD3+CD16+NK1.1+B220+ large granular lymphocytes arise from both alpha-beta TCR+CD4-CD8- and gamma-delta TCR+CD4-CD8- cells.

Cultivation of CD4-CD8- double negative (DN) mouse thymocytes and splenocytes with recombinant interleukin 2 (IL2) in the absence of other stimulation results in the generation of DN-CD3/TCR+CD16+NK1.1+B220+ large granular lymphocytes (LGL). Purified DN alpha-beta TCR+ thymocytes and splenocytes are CD16+IL2R alpha-IL2R beta+NK1.1+B220-CD5high. These cells are unique in that they express both CD16 and T cell receptor (TCR) which are usually mutually exclusive. In addition, they express the natural killer (NK) marker, NK1.1. Cultivation of these cells with IL2 for several days results in the generation of DN alpha-beta TCR+CD16+NK1.1+B220+CD5- LGL, suggesting that DN alpha-beta TCR+ cells in thymus and spleen are the precursors of the DN LGL reported previously. DN gamma-delta TCR+CD16-NK1.1-B220-CD5high thymocytes and splenocytes also give rise to DN gamma-delta TCR+CD16+NK1.1+B220+CD5- LGL which, as shown previously with DN alpha-beta TCR+ LGL cells, are cytotoxic against NK-sensitive YAC-1 cells. Cytotoxic activity is also induced through either CD16 or the gamma-delta TCR. DN alpha-beta TCR+ and DN gamma-delta TCR+ LGL cells are thus similar in phenotype to TCR- NK cells. DN alpha-beta TCR+ thymocytes express low levels of the gamma subunit of the high affinity immunoglobulin E receptor (Fc epsilon RI gamma) molecule, an essential component of CD16 expression. Fc epsilon RI gamma expression is greatly enhanced after cultivation with IL2, resulting in a higher surface expression of CD16. In contrast to DN alpha-beta TCR+ thymocytes, DN gamma-delta TCR+ thymocytes do not express detectable CD16 or Fc epsilon RI gamma mRNA but expression of both is induced by cultivation with IL2, leading to the expression of CD16 on the surface. Whereas CD16 molecules on both DN alpha-beta TCR+ and DN gamma-delta TCR+ LGL are associated with only Fc epsilon RI gamma homodimers, the TCR on these cells are associated with an Fc epsilon RI gamma homodimer and/or CD3 zeta-Fc epsilon RI gamma heterodimers. These results demonstrate that the Fc epsilon RI gamma subunit is a component of the TCR in a fraction of T lineage cells.

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.

Differential control of the tyrosine kinases Lyn and Syk by the two signaling chains of the high affinity immunoglobulin E receptor.

Nonreceptor tyrosine kinases such as the newly described 70-kDa (ZAP-70/Syk) and Src-related tyrosine kinases are coupled to a variety of receptors, including the antigen receptors on B- and T-cells and the Fc receptors for IgE (Fc epsilon RI) and IgG (Fc gamma RI, Fc gamma RIII/CD16). Various subunits of these receptors contain homologous activation motifs which appear capable of autonomously triggering cell activation. Two forms of this motif are present in the Fc epsilon RI multimeric complex: one in the beta chain and one in the gamma chain. Here we show that each of the two tyrosine kinases known to be involved in Fc epsilon RI signaling is controlled by a distinct motif-containing chain. Lyn associates with the nonactivated beta chain, whereas gamma promotes the activation of Syk. We also show that neither the beta nor the gamma motif alone can account for the full signaling capacity of the entire receptor. We propose that, upon triggering of the tetrameric receptor, Lyn already bound to beta becomes activated and phosphorylates beta and gamma; the phosphorylation of gamma induces the association of Syk with gamma and also the activation of Syk, resulting in the phosphorylation and activation of phospholipase C gamma 1. Cooperative recruitment of specific kinases by the various signaling chains found in this family of antigen receptors could represent a way to achieve the full signaling capacity of the multimeric complexes.

Expression of functional high affinity immunoglobulin E receptors (Fc epsilon RI) on monocytes of atopic individuals.

Suggestive evidence indicates that immunoglobulin E (IgE)-dependent activation of mononuclear phagocytes plays an important pathogenic role in allergic tissue inflammation. Prevailing opinion holds that low affinity IgE receptors are the relevant IgE-binding structures on monocytes/macrophages and that functional events occurring after cross-linking of membrane-bound IgE on these cells are mediated by these receptors. Here we demonstrate that peripheral blood monocytes can bind monomeric IgE via the high affinity IgE receptor (Fc epsilon RI) and that Fc epsilon RI expression on these cells is upregulated in atopic persons. Further, we demonstrate that, upon monocyte adherence to substrate, bridging of monocyte Fc epsilon RI is followed by cell activation. We propose that direct interaction of multivalent allergen with Fc epsilon RI(+)-bound IgE on mononuclear phagocytes results in cell signaling via Fc epsilon RI and that the biological consequences of this event may critically influence the outcome of allergic reactions.

A 2.8 Mb YAC contig in 11q12-q13 localizes candidate genes for atopy: Fc epsilon RI beta and CD20.

An important locus for Atopy (familial asthma, hay fever and eczema) has been localized to the 11q12-q13 region with the minimum recombination fraction around the CD20 gene. We have constructed a 2.8 megabase (Mb) Yeast Artificial Chromosome (YAC) contig of the candidate region using 15 STSs. A total of seven genes have been mapped within this interval in the order cen-OSBP-TCN1-GIF-Fc epsilon RI beta-CD20-CD5-PGA-q(ter) and can be covered by a minimum of eight YAC clones. Contig integrity was assayed with fluorescence in-situ hybridization (FISH) and the mapping of YAC ends on somatic cell and radiation hybrid panels. A long range restriction map of the contig has been constructed to establish the order of and distance between loci. Two promising candidates for the atopy locus, the beta subunit of the high affinity immunoglobulin E receptor (Fc epsilon RI beta) and CD20, a molecule involved in B cell differentiation, have been placed within the contig.

Abolition of anaphylaxis by targeted disruption of the high affinity immunoglobulin E receptor α chain gene

Mast cells and basophils, which are activated by immunoglobulin E (IgE) and allergen, play a prominent role in anaphylaxis. However, they express at least three types of IgE receptor, including the high affinity IgE receptor (FcεRI). The relative contribution of these IgE receptors, and possibly other receptors such as Fcε RII CD23 and Mac-2, to the genesis of in vivo anaphylaxis is still unclear. To address this question, we have generated FcεRI-deficient mice. These mice appear normal and express a normal number of mast cells, but they are resistant to cutaneous and systemic anaphylaxis. These data demonstrate that FcεRI is necessary for the initiation of IgE-dependent anaphylactic reactions. Therefore, interfering with its function should be an effective means of treating allergy, regardless of the allergen specificity.