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D Vercelli

Publications and source records attributed to D Vercelli.

At least 37 records · Page 2Linked to original sources
PubMed1990

Induction of germ-line and mature C epsilon transcripts in human B cells stimulated with rIL-4 and EBV.

EBV and rIL-4 induce T cell-independent IgE production by normal human B cells. We demonstrate here that EBV and IL-4 induced the synthesis of IgE by surface IgE-negative B cell precursors isolated by cell sorting. This result suggests that the induction of IgE by EBV and IL-4 results not merely from the expansion of a precommitted surface IgE-positive B cell population but more likely from IL-4-directed switching to IgE. At the molecular level, IL-4 and EBV induced the appearance of 2.0- and of 1.8-kilobase (kb) RNA bands, both of which hybridized with an 0.88-kb HinfI fragment spanning part of the C epsilon 1 exon and the entire C epsilon 2 exon. The 1.8-kb band but not the 2.0-kb band also hybridized with a cloned genomic 0.7-kb SmaI fragment located approximately 2 kb upstream of C epsilon. Thus, EBV and IL-4 induced germline (1.8-kb) as well as mature (2.0-kb) C epsilon transcripts. IL-4 by itself induced germ-line C epsilon transcripts but not mature C epsilon transcripts in purified normal B cells. IL-4 failed to induce IgE synthesis in established EBV B cell lines and failed to induce 2.0-kb mature C epsilon transcripts but induced 1.8-kb germ-line C epsilon transcripts. These data show that IL-4 is sufficient for the induction of C epsilon germ-line transcription. In contrast, the transcription of mature epsilon mRNA requires an additional activating signal, provided by infection with EBV. Established EBV transformation results in a dissociation between germ-line C epsilon transcription and the ability to undergo IgE switching in response to IL-4.

Antigens, Viral↗
PubMed1990

Engagement of the monocyte surface antigen CD14 induces lymphocyte function-associated antigen-1/intercellular adhesion molecule-1-dependent homotypic adhesion.

Murine anti-CD14 mAb which recognize different CD14 epitopes induced marked homotypic adhesion of normal human monocytes. Induction of aggregation by anti-CD14 mAb required Mg2+, occurred at an optimal temperature of 37 degrees C, but not at 4 degrees C, and exhibited a kinetics which differed from adhesion triggered by IFN-gamma and anti-CD43 mAb. Monocyte adhesion induced by anti-CD14 mAb required neither Fcy gamma R engagement nor cross-linking of CD14, because adhesion was induced by F(ab)'2 fragments, as well as by monovalent F(ab) fragments of anti-CD14 mAb. mAb to CD11a, CD18, and intercellular adhesion molecule-1 (ICAM-1), but not antibodies to CD11b and CD11c, inhibited monocyte adhesion induced by CD14 engagement. These results indicate that CD14-dependent adhesion is mediated by lymphocyte function-associated Ag-1/ICAM-1 interactions. This was confirmed by the absence of aggregation in anti-CD14-stimulated cells from a patient with leukocyte adhesion deficiency. Monocyte adhesion upon CD14 engagement was blocked by an inhibitor of protein kinases, sphingosine. This suggests that protein kinases play a role in the intracellular signaling pathway(s) which couple CD14 to lymphocyte function-associated Ag-1/ICAM-1.

Antibodies, Monoclonal↗
PubMed1990

Signal transduction via leukocyte antigen CD43 (sialophorin). Feedback regulation by protein kinase C.

CD43 is a constitutively phosphorylated 115-kDa sialoglycoprotein expressed on a variety of blood cells including lymphocytes and monocytes. L10, a mAb directed against CD43, triggers T cell activation and enhances hydrogen peroxide production in monocytes. Activation of mononuclear cells by L10 initiates phosphoinositides hydrolysis, C2+ mobilization, and protein kinase C (PKC) activation. In turn, activated PKC hyperphosphorylates CD43, suggesting a potential role for PKC in the regulation of signaling via CD43. To address this issue, we have analyzed the effect of PKC activation by the tumor promoter PMA on L10-triggered rise in intracellular free Ca2+ concentrations ([Ca2+]i). Treatment of mononuclear cells with PMA profoundly inhibited the increase in [Ca2+]i induced by L10. The inhibition of CD43-mediated signaling by PMA was due, in part, to uncoupling of CD43 from the signal-transducing G protein. This was evidenced by the comparatively modest inhibition by PMA of the increase in [Ca2+]i induced by the direct G protein activator AlF4-. PMA treatment did not affect the surface expression of CD43. However, it induced the hyperphosphorylation of CD43, the extent of which correlated with the inhibition of CD43-mediated increase in [Ca2+]i. Staurosporine, a potent inhibitor of PKC, abrogated the hyperphosphorylation of CD43 and normalized CD43-mediated signaling in PMA-treated cells. Significantly, in the absence of PMA, staurosporine enhanced the rise in [Ca2+]i triggered by L10, suggesting that engagement of CD43 by activating ligands results in feedback inhibition by PKC. It is concluded that activation of PKC inhibits signaling via CD43 by mechanisms involving phosphorylation and uncoupling of CD43 from the signal-transducing apparatus and by distal, post-receptor events.

Alkaloids↗
PubMed1990

IL-4 inhibits the synthesis of IFN-gamma and induces the synthesis of IgE in human mixed lymphocyte cultures.

The T cell-derived lymphokine IL-4 is essential for the induction of IgE synthesis by human lymphocytes. The IgE-inducing effect of IL-4 is antagonized by IFN-gamma. The secretion of IFN-gamma is vigorously triggered in MLC. Thus, IL-4-stimulated MLC represent a suitable model to characterize the functional antagonism between IL-4 and IFN-gamma. In this report, we show that rIL-4 consistently induced IgE synthesis when added to human primary MLC. IL-4-dependent IgE production required cognate T/B cell recognition, because it was inhibited by antibodies to CD3 and MHC class II (HlA-DR) Ag. A neutralizing anti-IFN-gamma mAb dramatically enhanced IL-4-dependent IgE synthesis by MLC, indicating that endogenous IFN-gamma is a major inhibitor of IgE production. More importantly, addition of rIL-4 markedly inhibited the release of IFN-gamma in supernatants of MLC and Con A-activated PBMC. The decrease in IFN-gamma protein was accompanied by a decreased expression of IFN-gamma mRNA transcripts. The downregulation of IFN-gamma by IL-4 is likely to play an important role in the IL-4-dependent induction of IgE synthesis.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1990

Interleukin 4 down-regulates the expression of CD14 in normal human monocytes.

Recombinant interleukin 4 (IL4) down-regulates the expression of CD14 on normal human monocytes, as assessed by flow cytometry, binding assays with radiolabeled anti-CD14 monoclonal antibody (mAb), and immunoprecipitation of 125I-labeled monocytes with anti-CD14 mAb. In parallel, CD23 expression on monocytes was strongly increased by IL4 stimulation, as assessed by both flow cytometry and immunoprecipitation. Down-regulation of surface CD14 was first detectable after 24-36 h of incubation with rIL4, and was almost complete after 4 days of culture. None of the other recombinant lymphokines tested (IL1, IL2, IL3, IL5, IL6, interferon-gamma, tumor necrosis factor alpha and beta, granulocyte-macrophage colony-stimulating factor) decreased CD14 expression. Metabolic labeling studies with [35S]methionine showed that both the membrane-associated and the soluble form of CD14 are decreased by IL4 stimulation. Northern blot analysis showed that incubation of monocytes with IL4 induced a marked decrease in CD14 mRNA. Nuclear run-off assays revealed that the IL4-dependent down-regulation of CD14 resulted from decreased transcription. Thus, IL4 exerts specific and opposite effects on the expression of monocytic antigens.

Antigens, CD↗
PubMed1990

Regulation of immunoglobulin (Ig)E synthesis in the hyper-IgE syndrome.

The hyper-IgE (HIE) syndrome is characterized by high IgE serum levels, chronic dermatitis, and recurrent infections. The mechanisms responsible for hyperproduction of IgE in HIE patients are presently unknown. We investigated whether spontaneous in vitro IgE synthesis by PBMC from seven HIE patients was sensitive to signals (cell adhesion, T/B cell cognate interaction and lymphokines: IL-4, IL-6, and IFN-gamma) known to regulate IgE induction in normals. Our results show that, unlike IL-4 dependent IgE synthesis induced in normals, spontaneous IgE production by PBMC from HIE patients was not blocked by monoclonal antibodies to CD2, CD4, CD3, and MHC class II antigens. Furthermore, antibodies to IL-4 and IL-6 did not significantly suppress IgE production. IFN-gamma had no significant effects on spontaneous in vitro IgE synthesis. To test whether an imbalance in lymphokine production might underlie hyperproduction of IgE in HIE patients, mitogen-induced secretion of IL-4 and IFN-gamma by PBMC was assessed. No significant difference was detected between HIE patients and normal controls. Thus, ongoing IgE synthesis in the HIE syndrome is largely independent of cell-cell interactions and endogenous lymphokines, and is due to a terminally differentiated B cell population, no longer sensitive to regulatory signals.

Adult↗
PubMed1989

Mechanism of mononuclear cell activation by an anti-CD43 (sialophorin) agonistic antibody.

CD43 (sialophorin, gpL115) is a sialoglycoprotein expressed on a wide variety of blood cells including lymphocytes, monocytes, neutrophils, and platelets. L10, an anti-CD43 mAb, has been shown to induce monocyte-dependent activation and proliferation of human T lymphocytes. We have studied the signaling mechanism involved in this activation process. Treatment of PBMC and purified populations of T cells and monocytes with L10 induced the hydrolysis of phosphoinositides with the resultant generation of the phosphoinositide-derived second messengers diacylglycerol and inositol phosphates. This was associated with the translocation of protein kinase C from cytosol to membrane fractions and an increase in free intracellular Ca2+ in treated cells. In human leukemic T cell lines, the magnitude of signaling via CD43 did not correlate with the density of the TCR/CD3 surface expression nor with the intensity of signaling via the TCR/CD3. Moreover, a mutant derived from the leukemic T cell line HPB-ALL that was severely defective in TCR/CD3 surface expression and signaling nevertheless had normal CD43 surface expression and signaling compared with the parent cell line. It is concluded that CD43 is functionally coupled to the phospholipase C/phosphoinositides signaling pathway. In human T cells, signaling via CD43 proceeds independently of TCR/CD3. The widespread expression of CD43 suggests a potentially important role for this molecule in orchestrating the activation of multiple cell types.

Adult↗
PubMed1989

The B-cell binding site on human immunoglobulin E.

Immunoglobulin E comprises the main immunoglobulin class associated with allergy. Its multifarious activities are mediated by two types of Fc receptors found on different cell populations, Fc epsilon R1 on mast cells and basophils, and Fc epsilon R2 on inflammatory cells (monocytes, eosinophils and platelets) and B lymphocytes. Recombinant epsilon-chain fragments synthesized in Escherichia coli have provided the means of mapping the receptor-binding sites on human IgE, and blocking IgE-receptor interactions. We have previously shown that the Fc epsilon R1 binding site is contained within a sequence (Gln 301-Arg 376) spanning the C epsilon 2 and C epsilon 3 domains. Here we show that Fc epsilon R2 can recognize a motif in the C epsilon 3 domain that is formed on dimerization of one or both of the flanking (C epsilon 2 and C epsilon 4) domains. Glycosylation of IgE is not required for the activity of either receptor.

Antibodies, Monoclonal↗
PubMed1989

Induction of human IgE synthesis requires interleukin 4 and T/B cell interactions involving the T cell receptor/CD3 complex and MHC class II antigens.

The induction of IgE synthesis by IL-4 requires T cells and monocytes, as well as T cell- and monocyte-derived cytokines. Optimal cytokine combinations, however, fail to induce highly purified B cells to secrete IgE, indicating that additional signals are required. We show herein that the induction of human IgE synthesis by rIL-4 requires cognate interaction between the T cell receptor/CD3 complex on T cells and MHC class II antigens on B cells: mAbs directed against these molecules completely blocked IL-4-dependent IgE induction. mAbs against cell adhesion molecules (CD2, CD4, LFA-1) also inhibited IgE synthesis induced by IL-4, confirming that cell-cell contact is necessary for IgE induction. The requirement for cognate T/B cell interaction was further shown by comparing the IgE-inducing ability of two human IL-4-producing alloreactive T cell clones: F6, which recognizes MHC class II antigens on both B cells and monocytes, and A1, which recognizes an HLA-DP-associated epitope expressed on monocytes, but not on B cells. When incubated with B cells and monocytes from a normal donor bearing the appropriate alloantigen, clone F6, but not clone A1, induced vigorous IgE synthesis, although both clones proliferated and secreted IL-4. Taken together, our results suggest that at least two, possibly synergizing, signals are required for the T cell-dependent induction of IgE synthesis by B cells: one signal is delivered by cognate T/B cell interaction, the other by T cell-derived IL-4.

Antibodies, Monoclonal↗
PubMed1989

Endogenous interleukin 6 plays an obligatory role in interleukin 4-dependent human IgE synthesis.

The lymphokine interleukin (IL) 4 plays a crucial role in the regulation of IgE synthesis. In the present study, the cellular and cytokine requirements for the IL4-dependent induction of IgE synthesis in humans were analyzed. Recombinant IL4 could induce IgE synthesis by peripheral blood mononuclear cells and autologous T/B cell mixtures, but not by highly purified B cells. IgE induction by IL4 was strongly decreased in monocyte-depleted peripheral blood mononuclear cells. These results show that the induction of IgE synthesis by recombinant IL4 is T cell dependent and optimal in the presence of monocytes. IL5 and IL6, but not IL2, IL1 and tumor necrosis factor-alpha, strongly up-regulated the IL4-dependent synthesis of IgE, with modest effects on cell proliferation. An anti-IL6 polyclonal antibody strongly inhibited IL4-driven IgE production. Endogenous IL6 plays, therefore, an obligatory role in the IL4-dependent induction of IgE. However, a combination of IL4, IL5 and IL6 (with or without IL1) at optimal concentrations could not induce IgE synthesis by purified normal B cells, indicating that cytokine-mediated signals, although essential, are not sufficient for the IL4-dependent induction of IgE synthesis.

B-Lymphocytes↗
PubMed1989

Wheat bran in the selective therapy of absorptive hypercalciuria: a study performed on 18 lithiasic patients.

The binding properties of raw vegetable fiber towards bivalent cations suggested the prescription of brain as a dietary supplement to limit intestinal calcium absorption in hypercalciuric patients. A group of 18 patients with a specific diagnosis of absorptive hypercalciuria received a dietary supplement of 14 gm. wheat bran at the 2 principal meals for 90 days. A complete assessment of mineral metabolism was performed after 45 and 90 days. Mean basal calciuria was 357 mg. per 24 hours and a significant decrease was noted after 45 days (245 mg. per 24 hours) and 90 days (240 mg. per 24 hours), with a p value of less than 0.01. Urinary oxalate did not vary significantly (0.34 to 0.38 to 0.31 mMol. per 24 hours) and neither did phosphate levels (1,020 to 900 to 893 mg. per 24 hours). A slight and pathologically insignificant decrease was noted in serum iron and urinary magnesium; this fact could be considered a side effect owing to the nonselective binding properties of fiber. Therefore, the positive results achieved confirm the effective action of wheat bran in the treatment of correctly diagnosed absorptive hypercalciuria.

Absorption↗
PubMed1989

Blocking of passive sensitization of human mast cells and basophil granulocytes with IgE antibodies by a recombinant human epsilon-chain fragment of 76 amino acids.

The recombinant peptide corresponding to residues 301-376 at the junction of constant regions 2 and 3 of the human IgE epsilon chain blocked the in vivo passive sensitization of human skin mast cells and in vitro sensitization of human basophil granulocytes with human IgE antibodies. An injection of the recombinant peptide or E myeloma protein into normal skin sites 1 hr before sensitization with an allergic serum blocked passive sensitization. In this system, approximately 10-fold higher molar concentration of the recombinant peptide than E myeloma protein was required for 50% inhibition of Prausnitz-Küstner reactions. When the mononuclear cells of two normal individuals were preincubated with the recombinant peptide or E myeloma protein for 15 min before passive sensitization with the same allergic serum and the cells were challenged with an optimal concentration of an antigen, approximately 11- to 13-fold higher concentration of the recombinant peptide than E myeloma protein was required for 50% inhibition of antigen-induced histamine release. Further studies with several recombinant peptides indicated that amino acid resides 363-376 in the Fc epsilon-chain fragment are not essential for binding of the peptide to Fc epsilon-chain receptor I.

Base Sequence↗
PubMed1989

Interleukin 4 dependent induction of IgE synthesis and CD23 expression by the supernatants of a human helper T cell clone.

The supernatants of the human alloreactive helper T cell clone A1, which secretes interleukins (IL) 4 and 5, could induce IgE synthesis by normal peripheral blood mononuclear cell and expression of Fc epsilon R2/CD23 on normal human monocytes. Both effects were IL-4 dependent, since they could be induced by recombinant IL-4 alone and were inhibited by an anti-IL-4 antibody. The activation of such clones may contribute to the high IgE production and the high percentage of circulating CD23+ monocytes observed in allergic disorders.

Antigens, Differentiation, B-Lymphocyte↗
PubMed1989

Low dosage treatment with propiono-hydroxamic acid in paraplegic patients.

Severe urinary tract infections due to urease-producing bacteria are frequently associated with neurourologic pathologies and complicated by infected nephrolithiasis. Hydroxamic acids, acting as urease inhibitors, can effectively reduce lithiasic risk, normalizing the urinary environment, as well as enhancing the action of antibiotic treatments. A low dosage propiono-hydroxamic acid (PHA) treatment, 60 mg twice a day for 7 days and then 60 mg/day, was used in 15 patients affected with neurourologic pathologies for 3 months. Nine patients were stone-free and 6 stone-bearers. Urinary pH and ammonium decreased in both groups. Halving the PHA dose did not cause any variation in urinary pH or ammonium trends. In the stone-bearing group an increase in these parameters was correlated with urinary infection recurrences. Complete sterilization was achieved in 11 of 14 patients who completed the trial. In the stone-free group no patient had an infectious recurrence after the first month. Two patients in the stone-bearing group had repeated recurrences. One patient dropped out after 45 days due to a decrease in platelets. The efficacy of such low dose treatment makes even long-term or repeated therapies possible, as is often needed by neurourologic patients.

Adult↗
PubMed1989

The IgE system.

The data presented herein indicate that IgE synthesis results from a complex interaction between T cells, B cells, and monocytes, under the control of T cell-derived and monocyte-derived lymphokines (IL-4, IL-5, and IL-6). In addition to their direct effects on IgE synthesis, these lymphokines have other functions, many of which are related to IgE. IL-4 is not only a crucial signal for the induction of IgE synthesis, but also a growth factor for murine mast cells together with IL-3, a product of the same T cell clones. Furthermore, IL-4 is a potent inducer of Fc epsilon R2b expression on both B cells and monocytes. On the other hand, IL-4-secreting T cells also produce IL-5, which promotes B cell maturation and induces differentiation of eosinophil precursors. Eosinophils, in turn, express CD23 when activated; thus, the activation of the IgE system leads to increased IgE synthesis and to enhanced expression of Fc epsilon R1 (on mast cells) and Fc epsilon R2 (on B cells, monocytes, and eosinophils). This in turn results in increased receptor-ligand interactions, with release of different chemical mediators involved in the pathogenesis of allergy. Such considerations suggest that the regulation of IgE synthesis should be viewed in the wider context of the IgE system, a multi-component network in which different cell types are functionally integrated mainly through lymphokine-mediated signals.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Human recombinant interleukin 4 induces Fc epsilon R2/CD23 on normal human monocytes.

rIL-4 (B cell stimulatory factor 1) induces the expression of Fc epsilon R2/CD23 on normal human monocytes (Mo). Fc epsilon R2/CD23 induction was detectable both by flow cytometry using anti-CD23 mAbs as well as soluble IgE, and by the immunoprecipitation with CD23-specific mAb or IgE of a 45-kD band from 125I-lactoperoxidase-labeled Mo. Fc epsilon R2/CD23 was fully expressed after a 24-h incubation with rIL-4, and was still detectable after 72 h from the addition of IL-4. This effect was specific, because none of the other rILs tested (IL-1, IL-2, IL-3, IL-5, B cell stimulatory factor 2, granulocyte-macrophage colony stimulating factor, and IFN-gamma) could induce FC epsilon R2/CD23, either alone or in various combinations. No synergism was observed between IL-4 and other ILs. IFN-gamma was not able to inhibit the IL-4-induced expression of Fc epsilon R2/CD23 on Mo, neither when added to the culture together with IL-4, nor when added 36 h earlier.

Gene Expression Regulation↗
PubMed1988

The mast cell binding site on human immunoglobulin E.

Antibodies of the immunoglobulin E isotype sensitize mast cells and basophils for antigen-induced mediator release by binding through the Fc portion to a high-affinity receptor (Fc epsilon R1, Ka = 10(9)M-1) on the cell surface causing the clinical manifestations of type I hypersensitivity. As the amino acid sequence of the human epsilon chain is now known, attempts have been made to map the Fc epsilon R1 binding site on IgE to a fragment smaller than Fc epsilon using proteolytic cleavage products, none of which proved to be active. Cleavage between the C epsilon 2 and C epsilon 3 domains released two inactive fragments, suggesting that the junction between these segments could be important in receptor binding. This region is protected against protease digestion in the rat IgE complex with the receptor of rat basophilic leukaemia cells. Here we report the mapping of the mast cell receptor binding site on human IgE to a sequence of 76 amino acids at the C epsilon 2/C epsilon 3 junction. Recombinant peptides containing this sequence inhibit passive sensitization of skin mast cells in vivo and sensitize mast cells to degranulation by anti-IgE in vitro almost as efficiently as a myeloma IgE. Fragments containing the separate domains are inactive. Additional sequences are required for rapid assembly of fragments into disulphide-linked dimers, suggesting that a single chain can form the active site. In a three-dimensional model of the human Fc epsilon, the two identical segments are far apart. Each folds to generate a cleft between the C epsilon 2 and C epsilon 3 domains on the surface of the Fc epsilon. The docking of IgE on to mast cells could take place within this cleft.

Amino Acid Sequence↗