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J F Gauchat

Publications and source records attributed to J F Gauchat.

At least 37 records · Page 2Linked to original sources
PubMed1997

CD86 (B7-2) on human B cells. A functional role in proliferation and selective differentiation into IgE- and IgG4-producing cells.

Immunoglobulin (Ig) E production by B cells requires two primary signals provided by T cells, interleukin (IL)-4 or IL-13 and CD40 ligand (CD40L). In addition, costimulatory signals, such as CD23-CD21 interaction, contribute further ensuring a selective control over this production. Recently, CD28, expressed on T cells, has been reported to be involved in this process. The CD28 ligands, CD80 (B7-1) and CD86 (B7-2), are expressed on human tonsillar B cells, and their expression is up-regulated by IL-4, IL-13, and/or an anti-CD40 monoclonal antibody (mAb). We have investigated whether signaling via the B7 molecules affects IgE synthesis. Human B cells were stimulated by IL-4 plus anti-CD40 mAb in the presence of different anti-B7 mAbs. Cross-linking of CD86 with IT2.2 potentiated IgE and IgG4 production and epsilon transcripts expression. The production of the other isotypes was not modulated. Conversely, the anti-CD80 and the other anti-CD86 mAbs tested had no effect. The increase of IgE and IgG4 production induced by IT2.2 was accompanied by an increase in proliferation, in cell surface density of CD23, and in CD23 binding to CD21-expressing B cells. In contrast, the expression of other B cell surface molecules such as CD11a, CD30, and CD58 remained unaffected. Since IT2.2 favors CD23-CD21 pairing, we tested whether blocking this interaction affected IT2.2-increased IgE production. The neutralizing anti-CD23 mAb, Mab 25, caused a dose-dependent inhibition of the effect of IT2.2 on IgE synthesis. Finally, IT2.2 potentiation on B cell proliferation and IgE production required the two primary signals, IL-4 and anti-CD40 mAb, since IT2.2 alone or in combination with only one of these stimuli did not show any effect on B cells. This study is the first demonstration of a signaling role for CD86. Together with IL-4 or IL-13 and CD40L, CD86 favors CD23-CD21 pairing and consequently functions as a selective and potent costimulus for human IgE and IgG4 synthesis.

Antibodies, Monoclonal↗
PubMed1997

Abnormal CD40-mediated activation pathway in B lymphocytes from patients with hyper-IgM syndrome and normal CD40 ligand expression.

The CD40-mediated activation pathway of B cells from 10 patients with hyper-IgM syndrome and normal expression of CD40 ligand was studied. In all 10 cases, B cells were found to be defective for IgG, IgA, and IgE production after stimulation by anti-CD40 mAbs and cytokines. In the patients tested, neither B cell proliferation (n = 6) nor CD23 molecule expression (n = 5) were observed in cultures stimulated with anti-CD40 mAb. These results point to an intrinsic B cell deficiency and a defect in the CD40-triggered B cell activation pathway; this conclusion was supported by a lack of detectable germinal centers in the spleen of two patients. CD40-triggered activation events, i.e., phosphatidylinositol 3 (PI3) kinase activation and induction of transcription factors NF-kappaB and AP-1, were next analyzed in B cell lines derived from five patients. Three distinct patterns were observed: an absence of detectable abnormalities (n = 1), defective PI3 kinase activation with normal induction of NF-kappaB and AP-1 (n = 3), and defects in both PI3 kinase activation and induction of NF-kappaB and AP-1 (n = 1). In three B cell lines, each exhibiting one of the CD40-mediated activation patterns, sequences of CD40 and CD40 binding protein coding regions were normal. The coding region of TNF receptor-associated factor 2 (TRAF2), which is known to interact with CD40 for NF-kappaB induction, was also found to be normal in B cell lines deficient in NF-kappaB induction. Altogether, these results suggest that CD40 ligand-positive hyper-IgM syndrome could be genetically heterogeneous, although phenotypic variability is not excluded, and that an early defect in the CD40-triggered activation cascade can account for defective Ig class switching in some patients with CD40 ligand-positive hyper-IgM syndrome.

Adolescent↗
PubMed1997

A novel 4-kb interleukin-13 receptor alpha mRNA expressed in human B, T, and endothelial cells encoding an alternate type-II interleukin-4/interleukin-13 receptor.

A 4 kb human interleukin-13 receptor (IL-13R) chain cDNA was cloned from a B cell cDNA library using expressed sequence tags homologous to mouse IL-13R as probes. The deduced protein sequence shows a significant level of sequence identity with the IL-5R and the human IL-13R identified recently by expression cloning. The cytoplasmic region is very highly conserved between human and mouse homologs and contains a consensus binding motif for a signal transducer and activator of transcription. The cDNA encodes a protein binding IL-13 when expressed alone which participates in a receptor complex for both IL-4 and IL-13 when expressed in conjunction with the IL-4R alpha chain. Transcripts for this IL-13R chain could be detected in most tissues and organs studied and in T, B, endothelial cells, basophilic, immature mast cell, and monocytic cell lines. The pattern of expression is different from the other recently cloned IL-13R molecule, and correlates with sites where IL-4 and IL-13 signaling is known to occur. This novel receptor is therefore likely to be implicated in reactions involved in IgE responses, T helper 2 differentiation, adhesion of leukocytes to endothelium, and therefore in pathological phenomena such as allergy, atopy, and asthma.

Amino Acid Sequence↗
PubMed1997

Structure and functions of CD23.

This review summarizes recent data on CD23, a low affinity receptor for IgE (Fc epsilon RII). CD23 is the only FcR which does not belong to the immunoglobulin gene superfamily. The CD23 molecule was discovered independently as an IgE receptor on human lymphoblastoid B cells [1], as a cell surface marker expressed on Epstein-Barr-Virus-transformed B cells (EBVCS) [2] and as a B-cell activation antigen (Blast 2) [3]. CD23 was shown to be a low affinity receptor for IgE [4,5]. Similar to most FcR, soluble forms of CD23 (sCD23) are released into extracellular fluids. The soluble fragments formed by proteolytic cleavage of surface CD23 are not only capable of binding IgE (IgE binding factors) but also exhibit multiple functions that are not IgE related. These observations together with the finding that CD23 displays significant homology with Ca(2+)-dependent (C-type) animal lectins, suggested the existence of natural ligands other than IgE. The recent finding that CD23 interacts with CD21, CD11b and CD11c indicates that CD23 should be viewed not only as a low affinity IgE receptor but also as an adhesion molecule involved in cell-cell interaction. After a brief overview of the molecular structure, there follows a discussion of the biological activities ascribed to human CD23.

Animals↗
PubMed1996

Soluble Fcgamma receptor type III (FcgammaRIII, CD16) triggers cell activation through interaction with complement receptors.

The type III-B Fcgamma receptor (FcgammaRIII-B) is a glycosyl-phosphatidylinositol-linked receptor found on human neutrophils. A soluble form of FcgammaRIII-B (sCD16) corresponding to the extracellular region of the receptor circulates in plasma. In the present work, we have identified membrane receptors for sCD16. Soluble CD16 bound to CR3 (CDllb/CD18)- and CR4 (CDllc/CD18)- positive leukocytes and cell lines, the labeling was inhibited by anti-CD11b, CD11c or CD18 mAbs, and the up-regulation of CR3 and CR4 led to an increased fixation of sCD16. Transfected eukaryotic cells expressing recombinant CD11b/CD18 or CD11c/CD18 heterodimers but not those expressing CD11a/CD18 bound sCD16. Moreover, the lectin-like binding site of CR3 is probably involved in the interaction with sCD16, as suggested by inhibition studies using mAbs against CR3 or sugars such as N-acetyl D-glucosamine, alpha- or beta-methyl D-glucoside, alpha- or beta-methyl D-mannoside, or zymosan. Thus, the complement receptors CR3 and CR4 are membrane receptors for sCD16. Through this interaction, sCD16 induces a CR3-dependent production of IL-6 and IL-8 by monocytes. These results suggest that sCD16 plays a regulatory role in inflammatory processes and provide a molecular basis for the interaction between FcgammaRIII-B and CR3 described on the cell membrane.

Antibodies, Monoclonal↗
PubMed1996

Human native soluble CD40L is a biologically active trimer, processed inside microsomes.

CD40 ligand (CD40L) is a glycoprotein expressed on the surface of activated helper T cells, basophils, mast cells, and eosinophils. Binding of CD40L to its receptor CD40 on the B cell surface induces B cell proliferation, adhesion, and immunoglobulin class switching. We have identified soluble cleavage products of human CD40L in the supernatant of a stimulated human T cell clone. Subcellular fractionation experiments have shown that the transmembrane CD40L is processed inside the microsomes and that its cleavage is stimulation-dependent. The native human soluble CD40L is trimeric and, when used in conjunction with interleukin-4, induces B cell proliferation.

B-Lymphocytes↗
PubMed1996

Cleavage of membrane-bound CD40 ligand is not required for inducing B cell proliferation and differentiation.

The physical interaction between the B cell surface molecule CD40 and its ligand, CD40L, is known to be crucial in the development and maintenance of humoral immunity. Recently it has been shown that the CD40L is processed and that its soluble cleavage products are released into the extracellular environment. To study the functions of soluble and membrane-bound human CD40L on human B cells, we generated an uncleavable CD40L cDNA deletion mutant. The activities of transfectants expressing either mutated or wild-type CD40L were then compared on human B cells. Both the soluble and the uncleavable membrane-bound CD40L were able to induce, in conjunction with interleukin-4, B cell proliferation and IgE synthesis. Therefore, membrane-bound and soluble CD40L exhibit the same pattern of activities on B cells and membrane CD40L cleavage is not a prerequisite for its function.

Amino Acid Sequence↗
PubMed1996

Pairs of surface molecules involved in human IgE regulation: CD23-CD21 and CD40-CD40L.

At least two cell-derived signals have been shown to be necessary for the induction of immunoglobulin isotype switching in B-cells. The first signal is given by either of the soluble lymphokines, interleukin (IL)-4 or IL-13, which induce germline epsilon transcript expression, but this alone is insufficient to trigger secretion of immunoglobulin E (IgE). The second signal is provided by a physical interaction between B-cells and activated T-cells, basophils and mast cells, and it has been shown that the CD40/CD40 ligand (CD40L) pairing is crucial for mediating IgE synthesis. In hyper-immunoglobulin M1 (HIGM1) syndrome, which is characterized by greatly decreased levels of immunoglobulin G, A and E (IgG, IgA and IgE), there are mutations in the CD40L resulting in a completely non-functional extracellular domain. The CD40L is, therefore, playing a central role in immunoglobulin isotype switching. Amongst the numerous pairs of surface adhesion molecules, the CD23-CD21 pair seems to play a key role in the generation of IgE. The CD23 molecule is positively and negatively regulated by factors which increase or decrease IgE production, respectively. Antibodies to CD23 have been shown to inhibit IL-4-induced human IgE production in vitro and to inhibit antigen-specific IgE responses in a rat model, in an isotype selective manner. CD23 interacts with CD21 on B-cells, preferentially driving IgE production. CD23 recognizes two main epitopes on the CD21 molecule. One region consists of short consensus repeat (SCR) sequences 1-2 and the other of SCR 5-8. In the latter region, Asn 370 and 295 are critical in the interaction with the lectin CD23. Therefore, a restricted number of cytokines and surface molecules seems to selectively regulate human immunoglobulin E synthesis.

Animals↗
PubMed1995

Thiols decrease human interleukin (IL) 4 production and IL-4-induced immunoglobulin synthesis.

N-Acetyl-L-cysteine (NAC) is an antioxidant precursor of intracellular glutathione (GSH), usually given in human as a mucolytic agent. In vitro, NAC and GSH have been shown to act on T cells by increasing interleukin (IL) 2 production, synthesis and turnover of IL-2 receptors, proliferation, cytotoxic properties, and resistance to apoptosis. We report here that NAC and GSH decrease in a dose-dependent manner human IL-4 production by stimulated peripheral blood T cells and by T helper (Th) 0- and Th2-like T cell clones. This effect was associated with a decrease in IL-4 messenger RNA transcription. In contrast, NAC and GSH had no effect on interferon gamma and increased IL-2 production and T cell proliferation. A functional consequence was the capacity of NAC and GSH to selectively decrease in a dose-dependent manner IL-4-induced immunoglobulin (Ig) E and IgG4 production by human peripheral blood mononuclear cells. Interestingly, NAC and GSH also acted directly on purified tonsillar B cells by decreasing the mature epsilon messenger RNA, hence decreasing IgE production. In contrast, IgA and IgM production were not affected. At the same time, B cell proliferation was increased in a dose-dependent manner. Not all antioxidants tested but only SH-bearing molecules mimicked these properties. Finally, when given orally to mice, NAC decreased both IgE and IgG1 antibody responses to ovalbumin. These results demonstrate that NAC, GSH, and other thiols may control the production of both the Th2-derived cytokine IL-4 and IL-4-induced Ig in vitro and in vivo.

Acetylcysteine↗
PubMed1995

Recombinant soluble trimeric CD40 ligand is biologically active.

CD40 ligand (CD40L) is expressed on the surface of activated CD4+ T cells, basophils, and mast cells. Binding of C40L to its receptor, CD40, on the surface of B cells stimulates B cell proliferation, adhesion and differentiation. A preparation of soluble, recombinant CD40L (Tyr-45 to Leu-261), containing the full-length 29-kDa protein and two smaller fragments of 18 and 14 kDa, has been shown to induce differentiation of B cells derived either from normal donors or from patients with X-linked hyper-IgM syndrome (Durandy, A., Schiff, C., Bonnefoy, J.-Y., Forveille, M., Rousset, F., Mazzei, G., Milili, M., and Fischer, A. (1993) Eur. J. Immunol. 23, 2294-2299). We have now purified each of these fragments to homogeneity and show that only the 18-kDa fragment (identified as Glu-108 to Leu-261) is biologically active. When expressed in recombinant form, the 18-kDa protein exhibited full activity in B cell proliferation and differentiation assays, was able to rescue of B cells from apoptosis, and bound soluble CD40. Sucrose gradient sedimentation shows that the 18-kDa protein sediments as an apparent homotrimer, a result consistent with the proposed trimeric structure of CD40L. This demonstrates that a soluble CD40L can stimulate CD40 in a manner indistinguishable from the membrane-bound form of the protein.

Amino Acid Sequence↗
PubMed1995

Undetectable CD40 ligand expression on T cells and low B cell responses to CD40 binding agonists in human newborns.

IgG, IgA, and IgE production by newborn B cells is limited both in vivo and in vitro in various activation conditions, whereas IgM production is readily detectable. It has been suggested that the Ig heavy chain switch inability could be the consequence of T and B cell immaturity. As the interaction between CD40 (expressed on B cells) and its ligand CD40-L (expressed on activated T cells) triggers a key signal required for isotype switching, we studied the expression and function of these two components in normal fetuses, newborns, and infants, compared with adults. CD40-L expression was not inducible in 28 of 30 specimens of newborn cord-blood T cells following incubation with PMA and ionomycin, whereas activation markers such as CD69 were inducible. CD40-L expression was triggered by activation of T cells from infants > 3 wk of age. Surprisingly, T cells from 19- to 28-wk-old fetuses also expressed CD40-L following activation. CD40-L expression on newborn T lymphocytes was induced on T cell lines generated in the presence of PHA and maintained with IL-2 following further stimulation with PMA and ionomycin. CD40-L mRNA transcripts and intracytoplasmic protein expression following activation of newborn T cells were strongly decreased, leading to undetectable protein membrane detection. These results point to a possible transcriptional down-regulation of CD40-L expression by neonatal T lymphocytes. In addition, fetal and cord-blood B cells were poorly able to switch to IgG or IgA by stimulation with CD40 agonists (Ab or soluble CD40-L) in the presence of IL-4 or IL-10 as also detected with surface IgD+ adult B cells. Both phenomena could contribute to the neonatal Ig switch inability, although distinct underlying regulatory mechanisms are probably involved, as suggested by different in vivo time courses.

Adult↗
PubMed1995

CD40 ligand is functionally expressed on human eosinophils.

CD40 ligand (CD40L), a surface molecule which can be expressed by T cells, mast cells and basophils, has been shown to be involved in the control of B cell proliferation, immunoglobulin class switching as well as in the activation of monocytes and T cells. We demonstrate that CD40L can also be expressed constitutively by eosinophils from an hypereosinophilic patient or, upon activation, by the eosinophilic cell line EOL-3 and normal blood eosinophils. Eosinophils were able to induce, in conjunction with IL-4, CD40L-dependent B cell proliferation in vitro. These results suggest that CD40L could play a role in the inflammatory processes during which eosinophil infiltration and activation are observed.

B-Lymphocytes↗
PubMed1995

Interleukin-12 increases interleukin-4 production by established human Th0 and Th2-like T cell clones.

Interleukin (IL)-12 is a potent inducer of cell-mediated immunity: it favors the generation of interferon (IFN)-gamma-producing T cells, increases IFN-gamma production by T cells and natural killer cells and prevents the generation of a Th2 response in murine in vivo models. Nevertheless, the effects of IL-12 on an established Th2 response remain poorly documented. In the present paper, we analyzed the effect of IL-12 on the profile of lymphokines produced by established IL-4-producing Th0 and Th2-like human T cell clones (TCC) and by polyclonal T cells. We found that IL-12 (i) enhances, as previously reported, IFN-gamma production by Th0 TCC and, to a smaller extent, by Th2-like TCC, (ii) increases the proliferation of Th0 and Th2-like TCC and (iii) unexpectedly, synergizes with T cell receptor-associated or nonspecific stimuli in increasing IL-4 production by these TCC. Thus, IL-12 potentiates the production of IFN-gamma and also of IL-4 by established IL-4 producing TCC. Although IL-12 has been widely reported to induce a Th1 response and to prevent the development of a Th2 response in vivo, IL-12 may on the contrary potentiate an established Th2 response in humans.

CD4-Positive T-Lymphocytes↗
PubMed1995

CD23 and B-cell activation.

The past year has seen the publication of significant new findings on the regulation of CD23 expression, the precise interaction of CD23 with CD21 and its functional consequences. Moreover, new advances have been made in unravelling the biochemical network of events downstream from the triggering of CD23 in human B cells. Analyses of the properties of CD23-deficient mice have demonstrated a link between IgE regulation and CD23 in vivo.

Animals↗
PubMed1995

CD23 regulates monocyte activation through a novel interaction with the adhesion molecules CD11b-CD18 and CD11c-CD18.

CD23 is expressed on a variety of haemopoietic cells and displays pleiotropic activities in vitro. We report that in addition to CD21 and IgE, CD23 interacts specifically with the CD11b and CD11c, the alpha chains of the beta 2 integrin adhesion molecule complexes CD11b-CD18 and CD11c-CD18, on monocytes. Full-length recombinant CD23 incorporated into fluorescent liposomes was shown to bind to COS cells transfected with cDNA encoding either CD11b-CD18 or CD11c-CD18 but not with CD11a-CD18. The interaction was specifically inhibited by anti-CD11b or anti-CD11c, respectively, and by anti-CD23 MAbs. The functional significance of this ligand pairing was demonstrated by triggering CD11b and CD11c on monocytes with either recombinant CD23 or anti-CD11b and anti-CD11c MAbs to cause a marked increase in nitrite-oxidative products and pro-inflammatory cytokines (IL-1 beta, IL-6, and TNF alpha). These CD23-mediated activities were decreased by Fab fragments of MAbs to CD11b, CD11c, and CD23. These results demonstrate that CD11b and CD11c are receptors for CD23 and that this novel ligand pairing regulates important activities of monocytes.

CD11 Antigens↗
PubMed1994

T cell clones from an X-linked hyper-immunoglobulin (IgM) patient induce IgE synthesis in vitro despite expression of nonfunctional CD40 ligand.

The induction of immunoglobulin E (IgE) switching in B cells requires at least two signals. The first is given by either of the soluble lymphokines interleukin 4 (IL-4) or IL-13, whereas the second is contact dependent. It has been widely reported that a second signal can be provided by the CD40 ligand (CD40L) expressed on the surface of T cells, mast cells, and basophils. A defect in the CD40L has been shown recently to be responsible for the lack of IgE, IgA, and IgG, characteristic of the childhood X-linked immunodeficiency, hyper IgM syndrome (HIGM1). IgE can however be detected in the serum of some HIGM1 patients. In this study, we isolated T cell clones and lines using phytohemagglutinin (PHA) and allergen, respectively, from the peripheral blood of one such patient who expressed a truncated form of CD40L, and investigated their ability to induce IgE switching in highly purified, normal tonsillar B cells in vitro. Unexpectedly, 4 of 12 PHA clones tested induced contact-dependent IgE synthesis in the presence of exogenous IL-4. These clones were also shown to strongly upregulated IL-4-induced germline epsilon RNA and formed dense aggregates with B cells. Of the four helper clones, three were CD8+, of which two were characteristic of the T helper cell 2 (Th2) subtype. Two allergen-specific HIGM1 T cell lines, both of the Th0 subtype, could also drive IgE synthesis when prestimulated using specific allergen. All clones and lines were negative for surface expression of CD40L, and the mutated form of CD40L was confirmed for a representative clone by RNase protection assay and sequencing. The IgE helper activity could not be attributed to membrane tumor necrosis factor alpha (TNF-alpha) although it was strongly expressed on activated clones, and the addition of neutralizing anti-TNF-alpha antibody did not abrogate IgE synthesis. These results therefore suggest the involvement of T cell surface molecules other than CD40L in the induction of IgE synthesis, and that these molecules may also be implicated in other aspects of T-B cell interactions.

Base Sequence↗