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J P Kinet

Publications and source records attributed to J P Kinet.

At least 37 records · Page 2Linked to original sources
PubMed1999

The high-affinity IgE receptor (Fc epsilon RI): from physiology to pathology.

The high affinity receptor for immunoglobulin E (designated Fc epsilon RI) is the member of the antigen (Ag) receptor superfamily responsible for linking pathogen-or allergen-specific IgEs with cellular immunologic effector functions. This review provides background information on Fc epsilon RI function combined with more detailed summaries of recent progress in understanding specific aspects of Fc epsilon RI biology and biochemistry. Topics covered include the coordination and function of the large multiprotein signaling complexes that are assembled when Fc epsilon RI and other Ag receptors are engaged, new information on human receptor structures and tissue distribution, and the role of the FcR beta chain in signaling and its potential contribution to atopic phenotypes.

Animals↗
PubMed1998

Crystal structure of the human high-affinity IgE receptor.

Allergic responses result from the activation of mast cells by the human high-affinity IgE receptor. IgE-mediated allergic reactions may develop to a variety of environmental compounds, but the initiation of a response requires the binding of IgE to its high-affinity receptor. We have solved the X-ray crystal structure of the antibody-binding domains of the human IgE receptor at 2.4 A resolution. The structure reveals a highly bent arrangement of immunoglobulin domains that form an extended convex surface of interaction with IgE. A prominent loop that confers specificity for IgE molecules extends from the receptor surface near an unusual arrangement of four exposed tryptophans. The crystal structure of the IgE receptor provides a foundation for the development of new therapeutic approaches to allergy treatment.

Amino Acid Sequence↗
PubMed1998

Phosphatidylinositol-3,4,5-trisphosphate (PtdIns-3,4,5-P3)/Tec kinase-dependent calcium signaling pathway: a target for SHIP-mediated inhibitory signals.

Tec family non-receptor tyrosine kinases have been implicated in signal transduction events initiated by cell surface receptors from a broad range of cell types, including an essential role in B-cell development. A unique feature of several Tec members among known tyrosine kinases is the presence of an N-terminal pleckstrin homology (PH) domain. We directly demonstrate that phosphatidylinositol-3,4,5-trisphosphate (PtdIns-3,4,5-P3) interacting with the PH domain acts as an upstream activation signal for Tec kinases, resulting in Tec kinase-dependent phospholipase Cgamma (PLCgamma) tyrosine phosphorylation and inositol trisphosphate production. In addition, we show that this pathway is blocked when an SH2-containing inositol phosphatase (SHIP)-dependent inhibitory receptor is engaged. Together, our results suggest a general mechanism whereby PtdIns-3,4,5-P3 regulates receptor-dependent calcium signals through the function of Tec kinases.

Agammaglobulinaemia Tyrosine Kinase↗
PubMed1998

Btk/Tec kinases regulate sustained increases in intracellular Ca2+ following B-cell receptor activation.

Bruton's tyrosine kinase (Btk) is essential for B-lineage development and represents an emerging family of non-receptor tyrosine kinases implicated in signal transduction events initiated by a range of cell surface receptors. Increased dosage of Btk in normal B cells resulted in a striking enhancement of extracellular calcium influx following B-cell antigen receptor (BCR) cross-linking. Ectopic expression of Btk, or related Btk/Tec family kinases, restored deficient extracellular Ca2+ influx in a series of novel Btk-deficient human B-cell lines. Btk and phospholipase Cgamma (PLCgamma) co-expression resulted in tyrosine phosphorylation of PLCgamma and required the same Btk domains as those for Btk-dependent calcium influx. Receptor-dependent Btk activation led to enhanced peak inositol trisphosphate (IP3) generation and depletion of thapsigargin (Tg)-sensitive intracellular calcium stores. These results suggest that Btk maintains increased intracellular calcium levels by controlling a Tg-sensitive, IP3-gated calcium store(s) that regulates store-operated calcium entry. Overexpression of dominant-negative Syk dramatically reduced the initial phase calcium response, demonstrating that Btk/Tec and Syk family kinases may exert distinct effects on calcium signaling. Finally, co-cross-linking of the BCR and the inhibitory receptor, FcgammaRIIb1, completely abrogated Btk-dependent IP3 production and calcium store depletion. Together, these data demonstrate that Btk functions at a critical crossroads in the events controlling calcium signaling by regulating peak IP3 levels and calcium store depletion.

Agammaglobulinaemia Tyrosine Kinase↗
PubMed1998

Allergy-associated FcRbeta is a molecular amplifier of IgE- and IgG-mediated in vivo responses.

A role for the Fc receptor beta chain (FcRbeta) in the pathogenesis of allergy has been suggested by genetic studies. FcRbeta is a subunit common to the high-affinity IgE (FcepsilonRI) and low-affinity IgG (FcgammaRIII) receptors, both of which contribute to the initiation of allergic reactions. Current in vitro data suggest that FcRbeta can function as either a positive or negative regulator, leaving a mechanistic explanation for its association with the development of atopy unclear. To address this controversy, we have generated novel mouse models relevant to human Fc receptor function. Analysis of FcepsilonRI- and FcgammaRIII-dependent responses in these mice provides unequivocal genetic evidence that FcRbeta functions as an amplifier of early and late mast cell responses and, remarkably, in vivo anaphylactic responses.

Anaphylaxis↗
PubMed1997

Negative regulation of Fc epsilon RI-mediated degranulation by CD81.

Signaling through the high affinity receptor for immunoglobulin E (Fc epsilon RI) results in the coordinate activation of tyrosine kinases before calcium mobilization. Receptors capable of interfering with the signaling of antigen receptors, such as Fc epsilon RI, recruit tyrosine and inositol phosphatases that results in diminished calcium mobilization. Here, we show that antibodies recognizing CD81 inhibit Fc epsilon RI-mediated mast cell degranulation but, surprisingly, without affecting aggregation-dependent tyrosine phosphorylation, calcium mobilization, or leukotriene synthesis. Furthermore, CD81 antibodies also inhibit mast cell degranulation in vivo as measured by reduced passive cutaneous anaphylaxis responses. These results reveal an unsuspected calcium-independent pathway of antigen receptor regulation, which is accessible to engagement by membrane proteins and on which novel therapeutic approaches to allergic diseases could be based.

Animals↗
PubMed1997

Fc epsilonRI-deficient mice infected with Schistosoma mansoni mount normal Th2-type responses while displaying enhanced liver pathology.

The IgE/Fc epsilonRI interaction is postulated to play an important role in resistance to helminths both at the level of anti-parasitic effector cell function and in the initiation of Th2 responses through IL-4 produced by Fc epsilonRI+ non-B, non-T (NBNT) cells. To formally evaluate the role of IgE/Fc epsilonRI signaling in the host response to helminths we studied Schistosoma mansoni infection in Fc epsilonRI knockout (KO) mice. Infected wild-type (wt) and KO animals showed comparable adult worm and tissue egg burdens, arguing against a role for Fc epsilonRI interactions in host resistance. Significantly, NBNT cells from infected KO, in contrast to wt animals, did not secrete IL-4 when stimulated with anti-IgE Ab or soluble parasite Ag. Nevertheless, serum IgE levels and Th2 cytokine production profiles were comparable in both strains of mice, demonstrating that the Ag-dependent stimulation of IL-4 secretion by NBNT cells is not essential for helminth-induced Th2 differentiation. However, when stimulated with low Ag doses, splenocytes from infected Fc epsilonRI-deficient mice produced less IL-4 in vitro than similar cultures from infected wt animals, an effect attributable to their defective NBNT cell function. Moreover, infected KO mice showed enhanced egg granuloma formation and hepatic fibrosis, revealing that the IgE/Fc epsilonRI interaction, while not essential for Th2 response development or resistance to primary infection, plays a significant role in down-regulating host pathology.

Animals↗
PubMed1997

Negative signaling pathways of the killer cell inhibitory receptor and Fc gamma RIIb1 require distinct phosphatases.

Inhibition of natural killer (NK) cells by the killer cell inhibitory receptor (KIR) involves recruitment of the tyrosine phosphatase SHP-1 by KIR and is prevented by expression of a dominant negative SHP-1 mutant. Another inhibitory receptor, the low affinity Fc receptor for immunoglobulin G (IgG) (Fc gamma RIIb1), has been shown to bind SHP-1 when cocross-linked with the antigen receptor on B cells (BCR). However, coligation of Fc gamma RIIb1 with BCR and with Fc epsilon RI on mast cells leads to recruitment of the inositol 5' phosphatase SHIP and to inhibition of mast cells from SHP-1-deficient mice. In this study, we evaluated the ability of these two inhibitory receptors to block target cell lysis by NK cells, and the contribution of SHP-1 and SHIP to inhibition. Recombinant vaccinia viruses encoding chimeric receptors and dominant negative mutants of SHP-1 and SHIP were used for expression in mouse and human NK cells. When the KIR cytoplasmic tail was replaced by that of Fc gamma RIIb1, recognition of HLA class I on target cells by the extracellular domain resulted in inhibition. A dominant negative mutant of SHP-1 reverted the inhibition mediated by the KIR cytoplasmic tail but not that mediated by Fc gamma RIIb1. In contrast, a dominant negative mutant of SHIP reverted only the inhibition mediated by the Fc gamma RIIb1 tail, providing functional evidence that SHIP plays a role in the Fc gamma RIIb1-mediated negative signal. These data demonstrate that inhibition of NK cells by KIR involves primarily the tyrosine phosphatase SHP-1, whereas inhibition mediated by Fc gamma RIIb1 requires the inositol phosphatase SHIP.

Animals↗
PubMed1997

Fc epsilonRI gamma can support T cell development and function in mice lacking endogenous TCR zeta-chain.

Fc epsilonRI gamma (Fc gamma) is a member of the zeta family of signal transducing molecules that function as components of both the TCR and Fc receptors (FcR). While the majority of thymocytes and T cells express TCRs containing zeta-chain homodimers, certain unique populations of T cells express TCRs that contain both zeta and Fc gamma. To examine the ability of Fc gamma to substitute for zeta-chain in T cell development and function, we introduced a transgene encoding Fc gamma into mice made genetically deficient for zeta-chain (zeta(e)-/-). Analysis of thymocyte development in zeta(e)-/-;Fc gamma Tg mice demonstrated that Fc gamma was able to support the maturation of both gammadelta TCR+ and alphabeta TCR+ T cells. However, positive selection of alphabeta TCR+ thymocytes was less efficient in zeta(e)-/-;Fc gamma Tg mice than in zeta(e)-/- mice reconstituted with zeta-chain. This difference may be due to the fact that Fc gamma contains a single immunoreceptor tyrosine-based activation motif (ITAM) whereas zeta-chain contains three ITAMs. Interestingly, the peripheral T cells that develop in zeta(e)-/- mice reconstituted with Fc gamma are functional and respond to TCR-specific stimuli. These data suggest that Fc gamma and zeta are interchangeable in their ability to mediate T cell development and function, however zeta-chain is more efficient at promoting positive selection and T cell maturation. The difference in efficiency between zeta and Fc gamma may be responsible in part for the unusual developmental and functional properties of T cells that constitutively express Fc gamma as a signaling component of their TCRs.

Animals↗
PubMed1997

IgE regulates mouse basophil Fc epsilon RI expression in vivo.

The binding of IgE to high-affinity IgE receptors (Fc epsilon RI) on the surface of mast cells and basophils primes these cells to secrete a panel of proinflammatory mediators upon subsequent exposure to specific Ag. We now find that the level of Fc epsilon RI expression on bone marrow basophils in mice infected with the nematode Strongyloides venezuelensis exhibits a strong positive correlation with the serum concentration of IgE, as was previously reported for human blood basophils. Moreover, the administration of IgE in vivo can significantly upregulate Fc epsilon RI expression on mouse basophils, and genetically IgE-deficient (IgE -/-) mice exhibit a dramatic (approximately 81%) reduction of basophil Fc epsilon RI expression compared with the corresponding normal (IgE +/+) mice. The finding that IgE can be a major regulator of mouse basophil Fc epsilon RI expression in vivo identifies a potentially important mechanism for enhancing the expression of effector cell function in IgE-dependent allergic reactions or immunologic responses to parasites.

Animals↗
PubMed1997

syk kinase activation by a src kinase-initiated activation loop phosphorylation chain reaction.

Activation of the syk tyrosine kinase occurs almost immediately following engagement of many types of antigen receptors, including Fc receptors, but the mechanism through which syk is activated is currently unclear. Here we demonstrate that Fc receptor-induced syk activation occurs as the result of phosphorylation of the syk activation loop by both src family kinases and other molecules of activated syk, suggesting that syk activation occurs as the result of a src kinase-initiated activation loop phosphorylation chain reaction. This type of activation mechanism predicts that syk activation would exhibit exponential kinetics, providing a potential explanation for its rapid and robust activation by even weak antigen receptor stimuli. We propose that a similar mechanism may be responsible for generating rapid activation of other cytoplasmic tyrosine kinases, such as those of the Bruton tyrosine kinase/tec family, as well.

3T3 Cells↗
PubMed1997

Systemic anaphylaxis in the mouse can be mediated largely through IgG1 and Fc gammaRIII. Assessment of the cardiopulmonary changes, mast cell degranulation, and death associated with active or IgE- or IgG1-dependent passive anaphylaxis.

We attempted to elicit active anaphylaxis to ovalbumin, or passive IgE- or IgG1-dependent anaphylaxis, in mice lacking either the Fc epsilonRI alpha chain or the FcR gamma chain common to Fc epsilonRI and Fc gammaRI/III, or in mice lacking mast cells (KitW/ KitW-v mice), and compared the responses to those in the corresponding wild-type mice. We found that the FcR gamma chain is required for the death, as well as for most of the pathophysiological changes, associated with active anaphylaxis or IgE- or IgG1-dependent passive anaphylaxis. Moreover, some of the physiological changes associated with either active, or IgG1-dependent passive, anaphylactic responses were significantly greater in Fc epsilonRI alpha chain -/- mice than in the corresponding normal mice. Finally, while both KitW/KitW-v and congenic +/+ mice exhibited fatal active anaphylaxis, mast cell-deficient mice exhibited weaker physiological responses than the corresponding wild-type mice in both active and IgG1-dependent passive systemic anaphylaxis. Our findings strongly suggest that while IgE antibodies and Fc epsilonRI may influence the intensity and/or kinetics of some of the pathophysiological changes associated with active anaphylaxis in the mouse, the mortality associated with this response can be mediated largely by IgG1 antibodies and Fc gammaRIII.

Anaphylaxis↗
PubMed1997

Absence of Fc epsilonRI alpha chain results in upregulation of Fc gammaRIII-dependent mast cell degranulation and anaphylaxis. Evidence of competition between Fc epsilonRI and Fc gammaRIII for limiting amounts of FcR beta and gamma chains.

In mouse mast cells, both Fc epsilonRI and Fc gammaRIII are alpha beta gamma2 tetrameric complexes in which different alpha chains confer IgE or IgG ligand recognition while the signaling FcR beta and gamma chains are identical. We used primarily noninvasive techniques (changes in body temperature, dye extravasation) to assess systemic anaphylactic responses in nonanesthetized wild-type, Fc epsilonRI alpha chain -/- and FcR gamma chain -/- mice. We confirm that systemic anaphylaxis in mice can be mediated largely through IgG1 and Fc gammaRIII and we provide direct evidence that these responses reflect activation of Fc gammaRIII rather than Fc gammaRI. Furthermore, we show that Fc gammaRIII-dependent responses are more intense in normal than in congenic mast cell-deficient KitW/KitW-v mice, indicating that Fc gammaRIII responses have mast cell-dependent and -independent components. Finally, we demonstrate that the upregulation of cell surface expression of Fc gammaRIII seen in Fc epsilonRI alpha chain -/- mice corresponds to an increased association of Fc gammaRIII alpha chains with FcR beta and gamma chains and is associated with enhanced Fc gammaRIII-dependent mast cell degranulation and systemic anaphylactic responses. Therefore, the phenotype of the Fc epsilonRI alpha chain -/- mice suggests that expression of Fc epsilonRI and Fc gammaRIII is limited by availability of the FcR beta and gamma chains and that, in normal mice, changes in the expression of one receptor (Fc epsilonRI) may influence the expression of functional responses dependent on the other (Fc gammaRIII).

Anaphylaxis↗
PubMed1997

IgE enhances mouse mast cell Fc(epsilon)RI expression in vitro and in vivo: evidence for a novel amplification mechanism in IgE-dependent reactions.

The binding of immunoglobulin E (IgE) to high affinity IgE receptors (Fc(epsilon)RI) expressed on the surface of mast cells primes these cells to secrete, upon subsequent exposure to specific antigen, a panel of proinflammatory mediators, which includes cytokines that can also have immunoregulatory activities. This IgE- and antigen-specific mast cell activation and mediator production is thought to be critical to the pathogenesis of allergic disorders, such as anaphylaxis and asthma, and also contributes to host defense against parasites. We now report that exposure to IgE results in a striking (up to 32-fold) upregulation of surface expression of Fc(epsilon)RI on mouse mast cells in vitro or in vivo. Moreover, baseline levels of Fc(epsilon)RI expression on peritoneal mast cells from genetically IgE-deficient (IgE -/-) mice are dramatically reduced (by approximately 83%) compared with those on cells from the corresponding normal mice. In vitro studies indicate that the IgE-dependent upregulation of mouse mast cell Fc(epsilon)RI expression has two components: an early cycloheximide-insensitive phase, followed by a later and more sustained component that is highly sensitive to inhibition by cycloheximide. In turn, IgE-dependent upregulation of Fc(epsilon)RI expression significantly enhances the ability of mouse mast cells to release serotonin, interleukin-6 (IL-6), and IL-4 in response to challenge with IgE and specific antigen. The demonstration that IgE-dependent enhancement of mast cell Fc(epsilon)RI expression permits mast cells to respond to antigen challenge with increased production of proinflammatory and immunoregulatory mediators provides new insights into both the pathogenesis of allergic diseases and the regulation of protective host responses to parasites.

Animals↗
PubMed1997

Expression and functions of the high-affinity IgE receptor on human platelets and megakaryocyte precursors.

Platelets can be activated by IgE and are therefore involved in IgE-mediated effector mechanisms against parasites and in allergic disorders. Here we show that, besides the low-affinity IgE receptor (Fc epsilon RII/CD23), platelets express the high-affinity receptor for IgE (Fc epsilon RI). Flow cytometry analysis revealed the existence of surface Fc epsilon RI on platelets with a large heterogeneity among individual donors, and a low proportion of platelets co-expressing Fc epsilon RI and FC epsilon RII/CD23. Northern hybridization and reverse transcription polymerase chain reaction confirmed the presence of mRNA encoding the alpha, beta and gamma chains of Fc epsilon RI in platelets and in their megakaryocytic precursors. Cross-linking of Fc epsilon RI with monoclonal antibody (mAb) to alpha chain using either the whole molecule or F(ab')2 triggered platelet cytotoxicity for Schistosoma mansoni larvae. Anti-Fc epsilon RII/CD23 mAb significantly inhibited IgE- or Fc epsilon RI-mediated cytotoxicity, indicating down-regulatory effects of Fc epsilon RII/CD23 on Fc epsilon RI-dependent functions. These results demonstrate functional properties for Fc epsilon RI on platelets and indicate unsuspected interactions between the low- and the high-affinity IgE receptors.

Adult↗
PubMed1997

The high-affinity receptor for IgE is the predominant IgE-binding structure in lesional skin of atopic dermatitis patients.

While the skin of most patients with atopic dermatitis (AD) is known to contain IgE-bearing cells, the contribution of the various IgE-binding structures to this phenomenon is not fully understood. To address this issue, we eluted cell-bound IgE from cryostat sections of lesional AD skin by acid treatment and performed reconstitution experiments with IgE in the absence or presence of reagents directed against the currently known IgE-binding structures. We found that incubation of acid-treated sections, with either chimeric or serum IgE, resulted in the appearance of sizable numbers of anti-IgE-reactive cells. This cellular IgE loading could be entirely prevented by preincubation of the sections with the anti-Fc epsilonRI alpha MoAb 15-1 but not with either antibodies against Fc epsilonRII/CD23 and Fc gammaRII/CD32 or with alpha-lactose. To exclude the possibility that acid treatment of tissue sections may have adversely influenced the IgE-binding capacity of IgE receptors other than Fc epsilonRI, we performed an identical series of experiments on AD skin samples that, as an exception, were essentially devoid of anti-IgE-reactive cells. Again, no IgE loading was detected when these sections were preincubated with anti-Fc epsilonRI alpha MoAbs. In contrast, preincubation of the sections with alpha-lactose and/or MoAbs against Fc epsilonRII/CD23 or Fc gammaRII/CD32 did not affect IgE loading. Together with the observations that anti-Fc epsilonRI alpha-reactive and IgE-binding cells are largely overlapping populations and include cells of the Langerhans cell/dendritic cell lineage, mast cells, and a few dermal dendrocytes and eosinophils, our results demonstrate that Fc epsilonRI is the predominant and, perhaps, the only biologically relevant IgE-binding structure on histogenetically and functionally diverse cell populations of AD skin.

Adult↗