PubMed Health⌕ Search

Biomedical subjects

G Delespesse

Publications and source records attributed to G Delespesse.

At least 55 records · Page 3Linked to original sources
PubMed1989

IgE synthesis by chronic lymphocytic leukemia cells.

The present results indicate that B cells isolated from chronic lymphocytic leukemia (B-CLL) from 11 of 14 patients are capable of specifically producing IgE upon costimulation with IL-4 and hydrocortisone (HC). IgE is detected by intracytoplasmic fluorescence staining and by RIA. Clinical, hematological, and immunological parameters (including Rai stage, WBC, Lc, sIg kappa/lambda, CD5, and CD23 expression) cannot distinguish the IgE responder from the nonresponder patients. IL-4 alone is a potent inducer of human IgE synthesis by normal PBMC and we show here that its effect is strikingly enhanced by HC. The IgE produced by B-CLLs are monoclonal since they display the same L chain type as the freshly isolated CD5+ B-CLLs. We, therefore, conclude that the combination of IL-4 and HC can abrogate the maturation arrest of CD5+ B-CLLs by inducing their differentiation into IgE-producing cells. The present data provide a unique model to study the isotype switching to IgE and the regulation of human IgE synthesis by monoclonal human B cells.

Antigens, Differentiation↗
PubMed1989

Influence of recombinant IL-4, IFN-alpha, and IFN-gamma on the production of human IgE-binding factor (soluble CD23).

This study documents the influence of rIL-4, IFN-gamma, and IFN-alpha on the production of IgE-BF and the expression of lymphocyte receptor for IgE or CD23 Ag (Fc epsilon R II) by human mononuclear cells. IL-4 increases the secretion of IgE-binding factor (BF) by highly purified B lymphocytes, adherent cells, and U937 monoblastic cells. The effect of IL-4 on purified B cells is augmented by costimulating the cells with F(ab')2 anti-IgM. IFN-gamma, IL-2, IL-1-alpha, or IL-1 beta and the low m.w. B cell growth factor have no effect on IgE-BF production by purified B cells even when they are used in combination with anti-IgM. Stimulation of purified T cells with IL-4 or IL-4 plus PMA leads to the production of very small amounts of IgE-BF that might well be derived from the contaminating non-T cells. IFN-gamma increases IgE-BF synthesis by unfractionated PBMC, T cell-depleted PBMC, adherent cells, and U937 cells suggesting that it induces monocytes to release IgE-BF, IFN-gamma suppresses the IL-4-induced Fc epsilon R II expression and IgE-BF production by highly purified B cells but not by PBMC or their T cell-depleted fractions. IFN-alpha inhibits IgE-BF production by IFN-gamma-stimulated PBMC and by IL-4-stimulated cells suggesting that it exerts its effect on B cells and on monocytes. Moreover IFN-alpha suppresses the IL-4-induced expression of Fc epsilon R II on B cells. Both IFN-alpha and IFN-gamma suppress the synthesis of IgE by PBMC in response to IL-4. Taken collectively the results indicate that: 1) IL-4 induces IgE-BF production by both B cells and monocytes, 2) IFN-gamma stimulates IgE-BF synthesis by monocytes but suppresses its production by IL-4-stimulated B cells, and finally 3) IFN-alpha inhibits IgE-BF synthesis in response to either IFN-gamma or IL-4.

Antigens, Differentiation, B-Lymphocyte↗
PubMed1989

Mechanisms of formation of IgE-binding factors (soluble CD23)--I. Fc epsilon R II bearing B cells generate IgE-binding factors of different molecular weights.

IgE-binding factors (soluble CD23) are generally considered to have an Mr of 25,000-27,000. The present study first indicates that IgE-BFs with an Mr of 33,000 or 37,000 may also be produced by Fc epsilon R II bearing B cells, depending upon the culture conditions and the nature of the Fc epsilon R II bearing cells. Extending our previous observations that the Mr 25,000-27,000 IgE-BFs are derived from the cleavage of soluble Mr 37,000 precursors, we show here that this cleavage is specifically inhibited by iodoacetamide but not by several other protease inhibitors. The proteolytic enzyme involved in the cleavage of Mr 33,000-37,000 precursors into Mr 25,000-27,000 IgE-BFs is cell-associated and is specifically expressed on Fc epsilon R II bearing cells. As expected, these Mr 33,000 and 37,000 fragments of Fc epsilon R II are capable of binding to IgE. The site at which these molecules are cleaved from Fc epsilon R II was located by determining their amino-terminal sequence. The Mr 37,000 IgE-BFs start at position 81 (glutamine) and the Mr 33,000 IgE-BFs start at position 102 (leucine) of the Fc epsilon R II sequence. Taken collectively, the present study not only contributes to our understanding of the mechanisms of formation of IgE-BFs, but also provides a means to prepare different molecular forms of IgE-BFs which may display different biological activity.

Amino Acid Sequence↗
PubMed1989

Human IgE-binding factors.

The production of IgE antibodies is known to be regulated by isotype-specific mechanisms that are not antigen specific. During the last decade several studies have indicated that soluble factors with affinity for IgE (IgE-binding factors, IgE-BFs) may exert such a role by interacting with IgE-bearing B lymphocytes. In the human, some of these IgE-BFs appear to be identical to soluble CD23, a B-cell surface marker thought to be involved in the control of B-cell proliferation or differentiation. In this article, Guy Delespesse and colleagues summarize several new findings regarding the cellular origin, structure and function of IgE-BFs/sCD23.

Antigens, Differentiation, B-Lymphocyte↗
PubMed1989

Human Fc epsilon R II and IgE-binding factors.

The low-affinity receptor for IgE (Fc epsilon R II) is mainly expressed on B lymphocytes, although it may also be found on some monocytes, eosinophils, and platelets. The presence of Fc epsilon R II on T cells is still controversial, but our results demonstrate that it is expressed on some HTLV-I-transformed T lymphocytes, and they strongly suggest that it may be found on a small proportion of normal T cells. Fc epsilon R II is a 45-KD glycoprotein containing one N-linked carbohydrate of complex type, O-linked carbohydrates, and sialic acid residues. Fc II is cleaved into soluble fragments with molecular weights of 37, 33, 25, and 12 KD, the first three retain the ability of binding to IgE, i.e., they are IgE-binding factors (IgE-BFs). The enzymes involved in their proteolytic cleavage are cell bound. The cDNA coding for Fc epsilon R II was cloned and functionally expressed. The predicted sequence has no homology with that of murine IgE-BFs which are of T cell origin. However, there is a striking homology with several animal lectins, and since the IgE-binding site is located in the homology region, it is possible that it binds to IgE via the carbohydrates expressed on the Fc region of this immunoglobulin. The expression of Fc epsilon R II on B cells and the release of IgE-BFs are upregulated by interleukin 4 and suppressed by gamma and alpha interferons.(ABSTRACT TRUNCATED AT 250 WORDS)

Antigens, Differentiation, B-Lymphocyte↗
PubMed1989

Low-affinity receptor for IgE (FcERII, CD23) and its soluble fragments.

The low-affinity receptor for IgE (FcERII or CD23) is a membrane 45-kD glycoprotein which is cleaved by an autoproteolytic mechanism into soluble 37-, 33- and 25-kD fragments that are capable of binding to IgE (IgE-binding factors, IgE-BFs). FcERIIa (which is expressed only on fresh B cells) differs from FcERIIb (which is expressed on IL4-stimulated B cells, monocytes, eosinophils and T cells) by a few intracytoplasmic amino acids. The only function of FcERII which is clearly demonstrated is the IgE-dependent cytotoxicity of FcERIIb on monocytes and eosinophils. We here review our recent observations indicating that 37-kD IgE-BFs regulate the synthesis of human IgE. Recombinant 37-kD IgE-BFs increase the IL4-induced synthesis of IgE by peripheral blood lymphocytes, as well as the IL4-independent, ongoing synthesis of IgE by either in vivo activated B cells from allergic patients or by in vitro IL4-preactivated B cells.

Antigens, CD↗
PubMed1988

Possible role of human lymphocyte receptor for IgE (CD23) or its soluble fragments in the in vitro synthesis of human IgE.

The present study demonstrates that human rIL-4 is capable of inducing the secretion of IgE by PBMC. At a concentration of 200 U/ml, an IgE response was observed in 11/26 cultures of PBMC from normal donors and in 12/15 cultures from allergic individuals. The same rIL-4-stimulated cells released significant amounts of IgE-binding factors (IgE-BF) in their culture supernatant. These IgE-BF were shown for the first time to bind simultaneously to some mAb against Fc epsilon R II (mAbER) and to soluble IgE. The lack of correlation between the rIL-4-induced secretion of IgE-BF and IgE indicates that the production of IgE-BF or the expression of Fc epsilon R II is not the only factor involved in the induction of IgE synthesis by rIL-4. However, the observation that mAbER suppressed the rIL-4-induced IgE synthesis strongly suggests that either Fc epsilon R II or IgE-BF are necessary for an IgE response. Finally, the spontaneous in vitro synthesis of IgE by enriched B cell preparations isolated from atopic donors was suppressed in an isotype-specific manner by the same mAbER or by their F(ab')2 fragments. These observations suggest that the ongoing IgE synthesis by in vivo pre-activated B cells is also regulated by IgE-BF or Fc epsilon R II. It is concluded that Fc epsilon R II or IgE-BF play an essential role both in the induction of IgE synthesis by normal B cells and in the ongoing IgE synthesis by in vivo activated B cells from allergic donors.

Antibodies, Monoclonal↗
PubMed1988

IgE receptor on human lymphocytes. IV. Further analysis of its structure and of the role of N-linked carbohydrates.

Previous studies have shown that the low affinity receptor for IgE (Fc epsilon R II) on human B lymphocytes was comprised of three components with apparent Mr of 45, 65 to 95, and 37 kDa. The present results indicate that the 37-kDa component is a soluble degradation fragment of the 45-kDa component and they also suggest that the 65- to 95-kDa component is probably made of aggregates of the above components that are formed after solubilization of the cells. The 45-kDa component appears to be a glycoprotein containing several sialic acid residues, O-linked carbohydrates and one N-linked carbohydrate chain that is of the complex type. Partial digestion of the purified 65- to 95-, 45-, and 37-kDa molecules with alpha-chymotrypsin or protease V8 generates several fragments with identical mobility on SDS-PAGE. The 37 kDa is not N-glycosylated but like the IgE-binding factors present in the culture supernatant of Fc epsilon R-bearing cells, it contains sialic acid and O-linked carbohydrates. On incubation with protease inhibitors, the Mr of IgE-binding factors (BF) is shifted from 25-27 to 37 kDa, indicating that IgE-BF are derived from the proteolytic cleavage of the 37-kDa molecule, previously identified as a membrane component of Fc epsilon R. On incubation with N-glycosylation inhibitors, the production of IgE-BF is significantly increased indicating that N-glycosylation inhibits the degradation of Fc epsilon R into IgE-BF. Inasmuch as the effect of glycosylation inhibitors is not prevented by monensin, it is concluded that all the IgE-BF are derived from surface Fc epsilon R and not from their intracellular precursors.

Antigens, Differentiation, B-Lymphocyte↗
PubMed1988

Comparison of mononuclear cell and B-lymphoblastoid histamine-releasing factor and their distinction from an IgE-binding factor.

We have characterized the histamine-releasing factors (HRF) from a B-lymphoblastoid cell line (RPMI 8866), compared it to mononuclear cell-derived HRF, and distinguished these from the IgE-binding factor produced by RPMI 8866. The B-cell-derived HRF fractionates at molecular weights of 90,000, 70,000, and 12-15,000 while mononuclear cell HRF has a major component at 24-26,000. The isoelectric points for B-cell HRF are 6.2-6.3 and 6.6-6.8 in contrast to 6.9 and 7.3 for mononuclear cell-derived HRF. The kinetics of histamine release by either HRF was the same, with half-maximal release in 5-10 min, unlike the rapid release caused by anti-IgE. Since HRF has been reported to be an IgE-binding factor, we screened column fractions for the IgE-binding factor secreted by RPMI 8866; this is known to be a shed low affinity IgE receptor. The chromatographic pattern and isoelectric point of this IgE-binding factor does not correspond to HRF; the purified IgE-binding factor had no significant histamine releasing activity on human basophils, and neither source of HRF was reactive in a radioimmunoassay to the IgE-binding factor. Our data suggest that HRF is quite heterogeneous and varies in physiochemical properties depending upon the cell source. The molecular relatedness (or nonrelatedness) of those HRFs is unclear; however, our data indicate that although HRF or fractions therefrom may bind to IgE as has been reported, it is unrelated to the low affinity IgE receptor.

B-Lymphocytes↗
PubMed1988

Elevation of IgE-binding factors in serum of patients with B cell-derived chronic lymphocytic leukemia.

One hundred nineteen sera from patients with various lymphoproliferative diseases and normal sera were tested by a solid-phase radioimmunoassay (RIA) for their content in IgE-binding factor (IgE-BF), a soluble glycoprotein binding to IgE and derived from low-affinity IgE receptors (Fc epsilon R). Fc epsilon R, recently identified as CD23, are known to be expressed on the surface of B cells at the intermediate stage of differentiation. The results indicate that in all cases of chronic lymphocytic leukemia (CLL) tested (n = 40), IgE-BF levels (45 to 8,656 U/mL) were 3-fold to 500-fold higher than in 24 controls (15.5 +/- 2 U/mL). With a few exceptions, serum IgE-BF levels could differentiate patients with CLL from those with other leukemias or lymphomas. In vitro studies indicated that B lymphocytes isolated from CLL patients produced 8 to 50 times more IgE-BF than did normal B cells (P less than 0.001). IgE-BF level was correlated with the Rai stage of the disease (P = 0.002) and the lymphocyte count (P = 0.041). IgE-BF was purified to homogeneity from one CLL serum sample by a combination of affinity chromatography and reverse-phase high-performance liquid chromatography (HPLC). this IgE-BF proved identical to IgE-BF isolated from the culture supernatant of RPMI 8866 cells, a B lymphoblastoid cell line bearing Fc epsilon R and secreting IgE-BF. Indeed, the two molecules had the same mol wt (25 to 27 kd), the same isoelectric point, and the same tryptic map. We suggest that determination of serum IgE-BF might prove useful for clinical monitoring of CLL.

B-Lymphocytes↗
PubMed1987

T-cell-derived IgE-binding factors. I. Cloned and transformed T cells producing IgE-binding factors.

In order to derive T cell clones that can produce factors that specifically regulate the IgE response, Fc epsilon receptor (Fc epsilon R)-positive T cells were isolated from two patients with hyper-IgE states (either the tropical pulmonary eosinophilia syndrome or the hyper-IgE syndrome) and transformed using the human T cell leukemia/lymphoma virus. After infection, these T4-positive, Fc epsilon R-positive T cells manifested a fourfold increase in the surface interleukin 2 receptor, a 10-fold increase in Fc epsilon R, and acquired viral markers not present in the uninfected cells. Cloning soon after transformation allowed for the isolation of 17 distinct T cell clones producing IgE-binding factors. The levels of these binding factors released in supernatant fluid from these clones ranged from 10 to 98 U (negative less than 1 U) using a radioimmunoassay. Furthermore, the presence and kinetics of production of these binding factors also could be demonstrated by metabolic labeling studies. These cells should prove potent immunologic tools for dissecting the various regulatory mechanisms involved in IgE production both in the normal state and in pathologic conditions.

Antigens, Viral↗
PubMed1987

T-cell-derived IgE-binding factors. II. Purification and characterization of IgE-binding factors produced by human T cell leukemia/lymphoma virus-1-transformed T lymphocytes.

We previously described human T cell leukemia/lymphoma virus-1-transformed T cell clones expressing surface molecules binding to monoclonal antibodies against lymphocyte Fc epsilon receptor (Fc epsilon R) and releasing soluble factors binding to both IgE and to monoclonal antibody to lymphocyte Fc epsilon R. In this study, one such clone (HE1-11) was tested for the presence of mRNA hybridizing with a cDNA probe coding for Fc epsilon R on B cells. Northern blot analysis revealed the presence of the same 1.7 kb Fc epsilon R mRNA in HE1-11 and in RPMI 8866 cells as well as in the macrophage cell line U937, expressing Fc epsilon R. The IgE binding factors (BF) released by HE1-11 cells appeared to be identical to those released by RPMI 8866 cells as shown by 1) one- and two-dimensional sodium dodecyl sulfate/polyacrylamide gel electrophoresis analysis and 2) tryptic peptides analysis. IgE-BF are microheterogeneous containing molecules with molecular mass of 25 to 27 kDa and with isoelectric point ranging from 4.5 to 5. Some preparations further contained 16-kDa fragments of IgE-BF. These findings suggest that the gene coding for both Fc epsilon R and IgE-BF may also be expressed on some human T cells.

Antibodies, Monoclonal↗
PubMed1987

Relationship between human IgE-binding factors (IgE-BF) and lymphocyte receptors for IgE.

This study indicates that human IgE-binding factors (IgE-BF) found in the cellfree culture supernatant (CSN) of Fc epsilon R-bearing B cells are breakdown products of the surface Fc epsilon R. This conclusion is suggested by the following observations. 1) Fc epsilon R and IgE-BF share several antigenic determinants as shown by immunoprecipitation with several Mab to Fc epsilon R (MabER) and SDS-PAGE analysis of the precipitates. 2) Upon incubation at 37 degrees C, normal tonsillar lymphocytes lose their Fc epsilon R and this is associated in a time-related manner with the release in the CSN of molecules reacting with two MabER. 3) Surface radioiodinated tonsillar lymphocytes or RPMI 8866 cells release labeled IgE-binding molecules displaying the same antigenic composition and the same migration on SDS-PAGE as purified IgE-BF. 4) Peptide mapping of highly purified IgE-BF and Fc epsilon R reveals the presence of several identical fragments after digestion with either alpha-chymotrypsin, trypsin, or papain. Moreover, papain digestion of the 25-27 kD IgE-BF and of the affinity-purified Fc epsilon R, generated a 15 kD fragment reacting with two MabER and that is known to bind IgE. Although these data strongly suggest that IgE-BF may be directly derived from cell surface IgE receptors, they do not exclude the possibility that some IgE-BF may also be secreted without being first anchored in the cell membrane.

Antibodies, Monoclonal↗
PubMed1987

Cloning and expression of the cDNA coding for a human lymphocyte IgE receptor.

Low-affinity receptors (Fc epsilon R) and secreted factors (IgE-BF) which bind to immunoglobulins of the IgE isotype play a key role in the regulation of human IgE synthesis. We report here the cloning of a cDNA coding for the Fc epsilon R of the human B-lymphoblast cell line RPMI 8866. The nucleotide sequence of this cDNA predicts a polypeptide with 321 amino acids and a mol. wt of 36,281 daltons. A functional Fc epsilon R capable of binding IgE was expressed in Chinese hamster ovary cells after stable transformation with the cDNA which had been cloned into a mammalian expression vector. Amino acid sequence analysis of IgE-BF purified from RPMI 8866 cells revealed an amino-terminal sequence of 19 residues which coincides with the predicted amino acid sequence of the Fc epsilon R, starting at residues 148 and 150. A computer search with the translated amino acid sequence of the Fc epsilon R revealed a domain of 120 amino acids having striking homology to the human asialoglycoprotein receptors.

Amino Acid Sequence↗
PubMed1987

Enhancement of IgE synthesis and histamine release by T cell factors derived from atopic patients with bronchial asthma.

Culture supernatants of unstimulated T cells (TCS) derived from normal donors or from atopic patients with bronchial asthma were tested for their ability to regulate the spontaneous IgE synthesis by B cells of normal and atopic subjects. The same TCS were also tested for their influence on the histamine release from leukocytes of house dust mites-sensitive patients. Addition of TCS to B cell cultures from allergic donors induced a dose-dependent increase of the spontaneous IgE production without affecting the synthesis of IgG, IgM, and IgA. The potentiating activity of TCS was observed only in B cell cultures spontaneously producing IgE; TCS were still active on irradiated B cells. The maximal IgE-enhancing activity was observed when TCS were added at the onset of B cell cultures. The supernatants of T cells lysed at day 0 did not contain IgE-potentiating factors. The antigen-induced but not the spontaneous histamine release from leukocytes of house dust mite-sensitive patients was enhanced by pretreatment with TCS from allergic donors. The enhancing activities of TCS on IgE synthesis and on histamine release could be removed by absorption with IgE-Sepharose and subsequently recovered by elution with glycine buffer. The results indicate that T cells of patients with asthma spontaneously release IgE-binding factors capable of increasing both the spontaneous IgE synthesis by B cells and the antigen-induced histamine release.

Asthma↗
PubMed1986

Production and characterization of rabbit anti-idiotypic antibodies specific to mouse monoclonal anti-human IgE and reacting with IgE-binding factors and lymphocyte receptors for IgE.

A mouse monoclonal antibody specific to human IgE (mAb 75) was employed to immunize a rabbit to obtain anti-idiotypes (aId) bearing the internal image of human IgE determinants and reacting with IgE-binding factors (IgE-BF) and/or lymphocyte receptors for IgE (Fc epsilon R). mAb 75 was selected on the basis of inhibition assays where the binding of mAb 75 to radiolabeled IgE was blocked by IgE-BF. The latter were produced by a lymphoblastoid cell line (RPMI 8866) expressing Fc epsilon R. Sequential samples of rabbit serum, collected during the immunization period, were extensively absorbed on mouse and human Ig-Sepharose 4B. The IgG fractions of the rabbit serum displayed the following activities: (a) they reacted with 125I-labeled mAb 75 but not with other labeled mouse Ig including mAb-aIgE, (b) this binding was inhibited in a dose-dependent fashion by human IgE but not by other human Ig classes nor by heat-inactivated IgE, (c) they reacted with a polyclonal rabbit anti-human IgE and (d) they blocked the binding of 125I-labeled IgE to mAb 75. It was concluded that the rabbit IgG contained aId (RaId) bearing the internal image of heat labile determinants of human IgE. The rosetting of IgE-coated bovine erythrocytes with Fc epsilon R-bearing cells was inhibited by preincubating the receptor-bearing cells with IgG RaId or its F(ab')2 but not with normal rabbit IgG. The ability of RaId to react with IgE-BF as well as with Fc epsilon R was also shown in inhibition experiments where IgE-BF and solubilized Fc epsilon R blocked the binding of mAb 75 to RaId. Finally, Western blot analysis of human colostrum, known to contain IgE-BF, indicated that radioiodinated RaId and IgE identified the same 12-16-kDa molecules corresponding to IgE-BF. It is concluded that RaId expresses the internal image of a heat-labile determinant of IgE which is involved in the binding of IgE to IgE-BF and Fc epsilon R. An alternative interpretation is that RaId reacts with an idiotypic determinant of mAb 75 which is shared by IgE-BF and Fc epsilon R.

Animals↗