Induction Of IgE Synthesis Research Articles

IgD-activated mast cells induce IgE synthesis in B cells in nasal polyps

Although upregulated expression of local IgD has been reported in patients with chronic rhinosinusitis (CRS), its function is unclear. We sought to explore the expression and function of soluble IgD in patients with CRS, particularly CRS with nasal polyps. IgD levels in sinonasal mucosa were analyzed by using RT-PCR and ELISA. Numbers and phenotypes of IgD+ cells were studied by means of immunohistochemistry, immunofluorescence, and flow cytometry. HMC-1cells, a human mast cell line, and mast cells purified from eosinophilic polyps were cultured alone or with naive B cells purified from peripheral blood. The antigen specificity of nasal IgD was investigated by using ELISA. The mRNA expression of immunoglobulin heavy constant delta gene, numbers of IgD+ cells, and protein levels of secretory IgD in sinonasal mucosa were increased in patients with CRS with or without nasal polyps compared with control subjects. Numbers of IgD+ plasmablasts were increased in both eosinophilic and noneosinophilic polyps, whereas numbers of IgD+ mast cells were only increased in eosinophilic polyps. Cross-linking IgD induced serum preincubated HMC-1cells and polyp mast cells to produce B-cell activating factor, IL-21, IL-4, and IL-13 and to promote IgM, IgG, IgA, and IgE production from B cells. In eosinophilic polyps expression of those B cell-stimulating factors in mast cells and close contact between mast cells and B cells were found. Moreover, positive correlations of total IgD levels with total IgE levels and eosinophilia and upregulation of specific IgD against house dust mites were discovered in eosinophilic polyps. IgD-activated mast cells can facilitate IgE production and eosinophilic inflammation in patients with CRS with nasal polyps.

The β2-adrenoreceptor gene promoter polymorphisms may modulate β2-agonist- and glucocorticoid-induced IgE synthesis

Backgroundβ2-adrenoreceptor (β2-AR) agonists and glucocorticoids (GCS) were shown to induce IgE synthesis in human PBMCs. Serum total IgE levels are associated with single nucleotide polymorphisms (SNPs) of the β2-AR gene. We aimed to assess the association of the effect of fenoterol (β2-AR agonist) on IL-4-driven and budesonide-induced IgE synthesis with genetic variants of β2-AR. MethodsThe study included 25 individuals: 13 with allergic asthma and/or allergic rhinitis and 12 healthy volunteers. PBMCs were cultured with IL-4, fenoterol and/or budesonide, and IgE concentrations in supernatants were assessed. Five SNPs in positions: −47, −20, 46, 79 and 252 of β2-AR were determined by direct DNA sequencing. ResultsIn −47 T/T and −20 T/T patients, incubation with fenoterol resulted in decreased IgE production, whereas in −47 C/T and −47 C/C as well as in −20 C/T and −20 C/C individuals, it was enhanced. In contrast to fenoterol, budesonide-induced IgE synthesis was significantly increased in −47 T/T and −20 T/T patients as compared to −47 C/T, −47 C/C, −20 C/T and −47 C/C individuals. Polymorphisms in positions 46, 79 and 252 were not associated with fenoterol- or budesonide-modulated IgE synthesis. No differences in the distribution of IgE synthesis was seen between atopic and non-atopic individuals carrying the same alleles. ConclusionsThe differential effect of β2-agonists and GCS on IgE synthesis may be associated with genetic variants of promoter region of the β2-AR gene.

Differential T-cell responses and allergen uptake after exposure of dendritic cells to the birch pollen allergens Bet v 1.0101, Bet v 1.0401 and Bet v 1.1001

The major birch pollen allergen Bet v 1 is present in pollen as a mixture of at least 14 isoforms that share high sequence and structural identities. These isoforms possess either a high or a low IgE-binding capacity which defines them as allergenic or hypoallergenic. Recently, we could demonstrate that only the allergenic isoform Bet v 1.0101 was able to induce an IgE response in birch pollen allergic individuals. The hypoallergenic isoforms Bet v 1.0401 and Bet v 1.1001 were unable to induce IgE synthesis. T-helper cell responses against allergens are characterised by increased levels of Th2 cytokines. Therefore, we examined extent and polarisation of the Th cell response and the kinetics of the allergen uptake after exposure of dendritic cells (DCs) to these isoforms. Monocyte-derived DCs (MDDCs) from birch pollen allergic and non-atopic individuals stimulated with Bet v 1.0101, Bet v 1.0401 or Bet v 1.1001 in combination with the maturation factors TNF-α and IL-1β resulted in a mature DC phenotype as measured by costimulatory molecule up-regulation. Only Bet v 1.0101-stimulated MDDCs from allergic subjects enhanced proliferation of autologous Th cells and the expression of the Th2 cytokines IL-5 and IL-13. Immature MDDCs of allergic individuals internalised equivalent amounts of the allergenic Bet v 1.0101 and the hypoallergenic Bet v 1.0401. In contrast, the uptake of the hypoallergenic Bet v 1.0401 by immature MDDCs of non-atopic individuals was significantly higher. These results provide evidence that DCs discriminate between allergens and highly related hypoallergens. This process may have an impact on the early phase of sensitisation.

Concentration of IgE in children during ragweed pollination season

Genetic and environmental factors are responsible for running allergic diseases. The aim of this study was to compare the values of total- (t-IgE) and allergen-specific IgE (s-IgE) to Ambrosia artemisiifolia L. (Amb a) in children with sensitization to Amb a during ragweed pollination season, who experienced seasonal symptoms of allergic rhinitis (rhinorrhea, post-nasal drip, nasal congestion, itching, sneezing) and asthma (coughing, especially at night, wheezing, shortness of breath, chest tightness). Ragweed pollen grains were collected in Virovitica (rural area) and Zagreb (urban area)—cities with the same geographical width and elevation—during ragweed pollination seasons (July–October in 2006 and 2007), and their count was estimated. Concentration of t-IgE and s-IgE in pollination season was determined in serum of children with symptoms of allergic diseases. The total count of ragweed pollen grains (PG) differed significantly between Virovitica and Zagreb in both years, 2006. and 2007. In Virovitica it was significantly greater than in Zagreb. There was no statistically significant seasonal difference in both, t-IgE and s-IgE, respectively. No correlation was found between pollen grain count and the concentration of IgE’s. To clarify the induction of IgE synthesis in children with sensitization to Amb a, further studies are needed.

Functional heterogeneity of human T cell clones from atopic and non-atopic donors.

Several distinct T helper (TH) subsets have been identified, based on the cytokines secreted. Recently, it has been demonstrated that these subsets can regulate the isotype of humoral responses. To investigate the possible differences in TH subsets between atopic donors which have elevated serum IgE and donors with normal serum IgE, we examined series of human TH cell clones. A total of 31 and 22 CD4+ T cell clones from the atopic and non-atopic donors, respectively, were characterized for the ability to help for IgE synthesis in vitro. T cell clones generated with allergen AgE from the atopic donor were autoreactive and all induced IgE synthesis. Tetanus toxoid-specific (TT) and phytohaemagglutinin clones were generated from both donors. There was significant heterogeneity between the T cells isolated with different stimuli from the same atopic donor. Also, there was a significant difference in the number of T cells generated from the atopic versus the non-atopic donor which helped for IgE, although there was no significant difference between the total number of T cells able to help for immunoglobulin synthesis of other isotypes. Most importantly, there was a higher frequency of clones able to support IgE synthesis between TT-specific T cell clones generated from the atopic versus the non-atopic donor. These results suggest that there are changes in subsets of TH cells specific for microbial antigens as well as allergens in atopics, which may have important implications for the aetiology of atopic disease.

Dual action of IL-4 on mite antigen-induced IgE synthesis in lymphocytes from individuals with bronchial asthma.

Polyclonal IgE synthesis was efficiently induced by Dermatophagoides farinae (Df) antigen in freshly derived peripheral blood lymphocytes from mite-sensitive individuals with bronchial asthma. The in vitro IgE production was significantly correlated with total serum IgE values. The induced IgE synthesis was inhibited in a dose-dependent manner by antibodies to IL-4, indicating a role for endogenous IL-4. Although IL-4 alone increased IgE production, high concentrations (1-100 U/ml) of the cytokine inhibited Df antigen-stimulated production of IgE. However, low concentrations (0.001-0.01 U/ml) of IL-4 significantly enhanced Df antigen-induced IgE production, as did high doses of IL-4 when endogenous IL-4 was neutralized by antibodies to IL-4. Two other cytokines, IL-10 and interferon-gamma (IFN-gamma), showed contrasting actions, as judged from experiments with, exogenous cytokine and anti-cytokine antibodies: IL-10 enhanced and IFN-gamma inhibited Df antigen-induced IgE synthesis. Thus, mite-stimulated IgE production in lymphocytes from individuals with bronchial asthma appears to be regulated by at least three cytokines: IL-4, IL-10, and IFN-gamma.

Recombinant interferon-gamma inhibits the expression of IL-4 receptors on human lymphocytes

Interferon gamma (IFN-gamma) has been shown to inhibit many of the activities of IL-4, including the induction of IgE synthesis and the proliferation of T cell clones. Here we demonstrate that IFN-gamma is able to inhibit the expression of IL-4 receptors on peripheral blood lymphocytes from both normal healthy donors and from patients with chronic lymphocytic leukaemia. Inhibition was shown to be dose-dependent and did not affect the binding affinity of the receptor as shown by Scatchard analysis. IFN-gamma was unable to displace labelled IL-4 from its membrane receptor, which demonstrates that IFN-gamma and IL-4 do not compete for the same membrane binding protein. The ability of IFN-gamma to down-regulate IL-4 receptors may be important in controlling certain immune responses.

The capacity of interleukin-4 to inducein vitroIgE synthesis by B cells of patients with common variable immunodeficiency

Interleukin-4 (IL-4) has been shown to induce IgE synthesis by peripheral blood mononuclear cells (PBMC) of normal donors in vitro. However, induction of PBMC of patients with common variable immunodeficiency (CVI) with IL-4 resulted in IgE production in only two out of eight cases tested. PBMC of the first patient that produced IgE in response to IL-4 also secreted normal levels of IL-4 upon activation. PBMC of the second patient secreted very low levels of IL-4 in vitro which may account for the very low serum IgE levels in this patient. Of the other six patients who had very low serum IgE levels and whose PBMC failed to produce IgE in response to IL-4 in vitro, five did not secrete IL-4 upon in vitro activation. The capacity of the T cells to produce IL-4 was intact in the sixth patient. Collectively our data indicate that PBMC of the majority of patients with CVI are defective since they failed to respond appropriately to IL-4 and they failed to produce IL-4, contributing to the view that CVI is a heterogeneous disorder in which a variety of T and B cell defects occur.

Diesel exhaust particles enhance T‐cell activation in severe asthmatics

Prevalence of asthma is increasing in westernized countries. Epidemiological studies showed the impact of traffic pollution on the triggering of asthma symptoms and exacerbations, and this effect is mainly attributed to the polycyclic aromatic hydrocarbon core of diesel exhaust particles (DEP). However, although DEP induce IgE synthesis, little is known of their role on T-cell activation, the main cells orchestrating asthma inflammation. We assessed the effect of DEP on T-cell activation in severe uncontrolled asthmatics during (n = 13) and outside (n = 19) exacerbations. Results were compared with data obtained in healthy controls (n = 14). Peripheral blood mononuclear cells were cultured in the presence of low-dose DEP. T-cell activation markers, CD69 and CD25, interleukin-4 (IL-4) and interferon (IFN)-gamma production and T-cell proliferation were assessed by flow cytometry. DEP exposure increased the proportion of CD3+CD69+ T cells in all subjects. The proportion of CD25+ T cells increased under DEP stimulation in the exacerbation group only. IFN-gamma- and IL-4-producing T cells increased in both asthmatic groups, especially during exacerbations, but not in controls. This effect was more pronounced for IL-4. In response to DEP stimulation, T-cell proliferation increased in higher proportion in asthmatics compared with controls. These results show that DEP activate T cells in asthmatics only, with a higher effect during exacerbations. This is in keeping with epidemiological data which demonstrated that DEP trigger respiratory symptoms in asthmatics but not in controls. The higher effect of DEP in exacerbated asthmatics suggests that uncontrolled asthma is a risk factor for aggravation under exposure to traffic pollutants.

3. Cytokines and chemokines

Cytokines and chemokines are secreted proteins with growth, differentiation, and activation functions that regulate the nature of immune responses. Cytokines are involved in nearly every facet of immunity and inflammation, from induction of the innate immune response to the generation of cytotoxic T cells and the development of antibodies by the humoral immune system. The combination of cytokines that are produced in response to an immune insult determines which arm of the immune system will be activated. For this update, recent advances in our understanding of cytokines will be discussed, which includes the IL-10, IL-17, and IL-27 families.

IL-4 modulates the histamine content of mast cells in a mast cell/fibroblast co-culture through a Stat6 signaling pathway in fibroblasts

IL-4 plays a crucial role in the pathogenesis of allergic diseases, such as the induction of IgE synthesis and the development of mast cells. To further understand the effect of IL-4 on mast cells in skin, we utilized a mast cell/fibroblast co-culture system as an in vitro model of dermal mast cells. IL-4 induced mast cell growth in the culture with fibroblasts. Immunoblot analysis revealed that IL-4 activated Stat6 in both mast cells and fibroblasts. The over-expression of dominant-negative Stat6 in fibroblasts in the presence of IL-4 decreased the histamine content per mast cell, but not the number of mast cells. In contrast, the over-expression of constitutively-active Stat6 in fibroblasts increased the histamine content per mast cell, indicating that the activation of Stat6 in fibroblasts supports the maturation of mast cells co-cultured with fibroblasts.

Japanese cedar pollen-specific interleukin-4 production develops immediately after the first exposure to pollens in infants with atopic dermatitis.

Japanese cedar pollens (JCPs) spread over most areas of Japan from February to April and cause pollenosis. While IgE synthesis against JCPs starts after age 1, it remains to be clarified when JCP-specific T helper cells acquire the ability to produce IL-4, a cytokine that induces IgE synthesis. This study aimed to clarify when the sensitization of T cells to JCPs develops. Peripheral blood mononuclear cells from 153 children with atopic dermatitis (AD) aged 0-15 years were stimulated with a standardized JCP allergen. As parameters of T cell responsiveness, lymphocyte proliferation and the production of IL-4 and IFN-gamma were measured. T cell responses against JCPs were negative before March in infants with AD who had never been exposed to JCPs or who were exposed for less than a month (nine, seven and nine subjects for lymphocyte proliferation, cytokine production and IgE synthesis, respectively). Lymphocyte proliferation distinctly increased in 67.6% (23/34) of infants with AD examined between March and June. JCP-specific IL-4 production was observed in 56.0% (14/25) of infants with AD examined between March and June. Correspondingly, a slight increase in the level of serum JCP-specific IgE antibody was seen in 17.2% (five of 29) of infants with AD examined between April and June. These results demonstrate that the sensitization of T cells to JCPs is effectively completed within a few months after the first exposure to JCPs.

Adenosine-activated mast cells induce IgE synthesis by B lymphocytes: an A2B-mediated process involving Th2 cytokines IL-4 and IL-13 with implications for asthma.

Adenosine provokes bronchoconstriction in asthmatics through acute activation of mast cells, but its potential role in chronic inflammation has not been adequately characterized. We hypothesized that adenosine up-regulates Th2 cytokines in mast cells, thus promoting IgE synthesis by B lymphocytes. We tested this hypothesis in human mast cells (HMC-1) expressing A(2A), A(2B), and A(3) adenosine receptors. The adenosine analog 5'-N-ethylcarboxamidoadenosine (NECA) (10 microM) increased mRNA expression of IL-1beta, IL-3, IL-4, IL-8, and IL-13, but not IL-2 and IFN-gamma. Up-regulation of IL-4 and IL-13 was verified using RT-PCR and ELISA; 10 microM NECA increased IL-13 concentrations in HMC-1 conditioned medium 28-fold, from 7.6 +/- 0.3 to 215 +/- 4 pg/ml, and increased IL-4 concentrations 6-fold, from 19.2 +/- 0.1 to 117 +/- 2 pg/ml. This effect was mediated by A(2B) receptors because neither the selective A(2A) agonist 2-p-(2-carboxyethyl)phenethylamino-NECA nor the selective A(3) agonist N(6)-(3-iodobenzyl)-N-methyl-5'-carbamoyladenosine reproduced it, and the selective A(2B) antagonist 3-isobutyl-8-pyrrolidinoxanthine prevented it. Constitutive expression of CD40 ligand on HMC-1 surface was not altered by NECA. Human B lymphocytes cocultured for 12 days with NECA-stimulated HMC-1 produced 870 +/- 33 pg IgE per 10(6) B cells, whereas lymphocytes cocultured with nonstimulated HMC-1, or cultured alone in the absence or in the presence of NECA, produced no IgE. Thus, we demonstrated induction of IgE synthesis by the interaction between adenosine-stimulated mast cells and B lymphocytes, and suggest that this mechanism is involved in the amplification of the allergic inflammatory responses associated with asthma.

Increased biological activity of IL-13.Q130, a naturally occurring variant of human IL-13, in primary human cells

Rationale The fourth exon of human IL-13 harbors a single nucleotide polymorphism, IL-13/+2044G→A, which results in the non-conservative replacement of arginine (R)130 with glutamine (Q). IL-13/+2044G→A is associated with increased IgE levels and/or asthma prevalence in several populations. Therefore we asked whether IL-13.R130 (wild-type) and IL-13.Q130 have different biological activities on primary human cells. We focused on STAT6-dependent events (IgE synthesis, CD23 induction) highly relevant to allergic inflammation. Methods Recombinant IL-13.R130 and IL-13.Q130 were produced in a eukaryotic expression system. For STAT6 activation, peripheral blood mononuclear cells (PBMC) were stimulated with IL-13.R130 or IL-13.Q130 for 1 hour and tested for intracellular STAT6 phosphorylation by immunofluorescence with an anti-phospho-STAT6 antibody. Membrane CD23 expression on PBMC incubated with IL-13 variants for 48 hours was assessed by immunofluorescence. For IgE induction, PBMC were incubated with IL-13 variants and hydrocortisone for 12 days. IgE synthesis was measured by ELISA. Differences in activity were derived from differences in the IL-13.R130 and IL-13.Q130 dose-response curves. Results IL-13.Q130 was more active than IL-13.R130 in each functional assay. IL-13.Q130 was 3.5-fold more active than wild-type IL-13 in inducing STAT6 phosphorylation, 3-fold more active in upregulating CD23 expression in monocytes, and 6-fold more active in inducing IgE synthesis by human B cells treated with hydrocortisone. Conclusions The naturally occurring IL-13.Q130 variant expressed in carriers of IL-13/+2044G→A is more active than wild-type IL-13.R130 in triggering STAT6-dependent events and IgE synthesis in primary cells. These results are consistent with the association between IL-13/+2044G→A and increased IgE levels and/or asthma prevalence in populations throughout the world.

Polymorphisms in the interleukin-4 and interleukin-4 receptor alpha chain genes confer susceptibility to asthma and atopy in a Caucasian population.

IL-4 by binding to its receptor (IL-4R) is essential for the development of airway inflammation present in asthma, through the induction of IgE synthesis in B cells and differentiation of T cells to a Th2 phenotype. To investigate the role of four common polymorphisms in the IL-4 (IL4-34CT and IL4-589CT) and IL-4Ralpha chain (IL4RAI50V and IL4RAQ576R) genes in conferring susceptibility to the development of atopy and/or asthma. Two polymorphisms in the IL-4 gene promoter, IL4-34CT and IL4-589CT, and two polymorphisms in the IL-4Ralpha chain gene, IL4RAI50V and IL4RAQ576R, have been genotyped using PCR-based methods in 341 asthmatic families and in 184 non-asthmatic adults recruited from the south of England. Case-control analysis did not reveal differences in the distribution of the four polymorphisms between asthmatics and controls. However, the transmission disequilibrium test showed that the IL4-589 T allele was preferentially transmitted to asthmatic children (P=0.036) and that the IL4RAQ576 was preferentially transmitted to children with atopic asthma (P=0.018). Haplotype analysis showed a strong association between the IL4-34T/-589T haplotype and asthma per se (P=0.041), and a strong association between the IL4RA I50/Q576 haplotype and atopic asthma (P=0.006). Our data suggest that polymorphisms in the IL-4 and IL-4Ralpha chain genes might play a role both conferring susceptibility to and modulating severity of atopy and asthma.

Modulation of allergic response in nasal mucosa by antisense oligodeoxynucleotides for IL-4

Background: The cytokine IL-4 is highly involved in TH2 inflammation, such as that seen in allergic rhinitis. IL-4 can induce IgE synthesis and eotaxin. Recent studies have shown that stimulation of allergic nasal tissue with ragweed allergen can induce local IL-4 mRNA production. Objective: We set out to determine whether IL-4 antisense phosphorothioate-modified oligodeoxynucleotides (PS-ODNs) could inhibit IL-4 production and downstream events of IL-4. Methods: Nasal mucosa biopsy specimens were obtained from patients with seasonal ragweed allergic rhinitis out of season, incubated ex vivo with or without PS-ODNs, and challenged with ragweed. FITC-labeled oligonucleotides were used to determine tissue uptake. By using immunocytochemistry, IL-4–, IL-13–, eotaxin 1–, and IFN-γ–producing cells were enumerated, and by using in situ hybridization, ϵ germline transcript RNA– and IL-4 mRNA–positive cells were examined. Results: The antisense PS-ODN was taken up by the tissue, and preincubation of the tissue with the IL-4 antisense PS-ODN caused a decrease in allergen-induced IL-4 mRNA and a decrease in the amount of IL-4 immunoreactivity (n = 7, P < .001). PS-ODNs had inhibitory effects on allergen-induced ϵ germline transcript RNA expression (n = 7, P < .001) and mucosa eotaxin 1 immunoreactivity (n = 7, P < .05). In contrast, the PS-ODNs increased the amount of IFN-γ immunoreactivity (n = 7, P < .05), suggesting a nonspecific mechanism for reduced synthesis of IgE and eotaxin. Conclusions: Our results show that the IL-4 antisense PS-ODN effectively inhibits IL-4, IgE synthesis, and eotaxin, principal mediators of allergic inflammation, suggesting that PS-ODNs might offer a possible topical treatment for allergic rhinitis. (J Allergy Clin Immunol 2003;111:580-6.)

Cultured basophils but not cultured mast cells induce human IgE synthesis in B cells after immunologic stimulation.

By generating human mast cells and basophils from umbilical cord blood mononuclear cells cultured in the presence of appropriate cytokines, we investigated whether these two cultured cells could provide the cytokine and cell contact signals that are required to induce IgE synthesis in B cells. To activate cultured mast cells and basophils, cross-linking of cell surface high-affinity IgE receptor (Fc epsilonRI) was performed with specific antigen after sensitization with murine IgE. Upon Fc epsilonRI stimulation, basophils, but not mast cells, secreted significant amounts of immunoreactive IL-4 and IL-13 and expressed detectable CD40 ligand (CD40L) and a very low level of Fas ligand (FasL). These observations at the protein level were consistent with the data obtained at the gene transcriptional level, except for the faint expression of only IL-13 mRNA in mast cells. When added to normal human B cells, activated basophils induced IgE and IgG4 synthesis as well as soluble CD23 release. In contrast, neither IgE nor IgG4 synthesis could be induced by the interaction of B cells with activated mast cells, even in the presence of recombinant IL-4. The induction of IgE synthesis by activated basophils was completely abrogated by two neutralizing MoAbs against IL-4 and IL-13 and by a soluble form of CD40. This abrogation was accompanied by abolished mature C epsilon transcription in both cases. Addition of anti-FasL MoAb, however, did not significantly affect IgE induction mediated by activated basophils. These results demonstrate that unlike cultured mast cells, cultured basophils produce biologically active IL-4 and IL-13 and express functional CD40L after Fc epsilonRI stimulation, thereby contributing to IgE production by B cells, and suggest that relatively weak expression of FasL by cultured basophils is not involved in IgE regulation.

A Factor of Inducing IgE from a Filarial Parasite Is an Agonist of Human CD40

Immune responses to parasitic helminth are usually characterized by quite mysterious phenomena: dominance of Th2-like immunity and antigen-nonspecific IgE secretion. We previously purified a factor from Dirofilaria immitis that induces antigen-nonspecific IgE in rats and named it DiAg. In the presence of IL-4, DiAg induces mouse B cells to secrete IgE, which is antigen-nonspecific polyclonal antibody. We investigated the biochemical characteristics of DiAg as a factor of inducing IgE in this study. Recombinant DiAg (rDiAg) with interleukin (IL)-4 induced IgE synthesis in highly purified human normal B cells in vitro cell culture systems. The addition of recombinant human soluble CD40 IgG fusion protein (rsCD40-Ig) inhibited induction of IgE synthesis by rDiAg with IL-4. Monocyte cells were stimulated with rDiAg and recombinant human soluble CD40L (rsCD40L); IL-12 and TNF-alpha were induced. The addition of rsCD40-Ig to THP-1 cells activated with rDiAg and rsCD40L inhibited the production of IL-12. rDiAg bound to the monocyte cell membrane fraction and recombinant human soluble CD40; this binding of rDiAg was competitively inhibited by addition of rsCD40L. Moreover, in CD40-deficient mice, IgE production and MLN-B cell proliferation by rDiAg were completely absent. Based on these results, we concluded that DiAg is an agonist of CD40.

Mercuric Chloride Enhances Immunoglobulin E-Dependent Mediator Release from Human Basophils

Mercuric chloride (HgCl2) is an industrial agent known to cause autoimmune disorders and induce IgE synthesis, which plays a crucial role in the manifestation of allergic diseases. In rodents, the immunomodulatory effects of HgCl2 have been shown to involve the enhancement of mast cell-derived IL-4 secretion, which facilitates both Th2-lymphocyte development and IgE production. In humans, rapid allergen-dependent release of IL-4 and the related cytokine IL-13 from histamine-containing cells occurs primarily in basophils, along with other proinflammatory mediators such as histamine and LTC4. In this study, we therefore investigated the effects of HgCl2 on the release of the above basophil mediators, either due to the compound alone or in conjunction with IgE-dependent stimulation. HgCl2 (10−9 to 10−6 M) did not induce mediator secretion alone but significantly enhanced the release of histamine, LTC4, IL-4, and IL-13 caused by anti-IgE. Higher concentrations of HgCl2 (10−5 to 10−3 M) strikingly reduced cell viability; however, toxicity varied depending on cell density and incubation time. Removal of HgCl2 following a short incubation with basophils did not reverse the potentiating effects on basophil mediator secretion to anti-IgE and the concentration of free mercury in the supernatants significantly diminished by up to 20% after incubation with the cells, indicating irreversible Hg binding to cells. By upregulating IgE-dependent human basophil mediator release, our results clearly indicate that HgCl2 potentially exacerbates allergic disorders and promotes a Th2-cytokine profile.

Revisiting the roles of mast cells in allergic rhinitis and its relation to local IgE synthesis.

Mast cells are important effector cells in the immediate-phase allergic reaction. However, in recent years much evidence has accumulated on the versatile role of mast cells in allergic inflammation. The present article is an overview of the roles of mast cells in allergic inflammation, especially in light of the local production of IgE and the IgE-IgE receptor network. Although both nasal mast cells (NMC) and T cells in allergic rhinitics are important sources of Th2-type cytokines like IL-4 and IL-13, and can induce IgE synthesis, we report here that antigen-activated NMC can secrete greater levels of IL-4/IL-13 and induce increased levels of IgE synthesis than antigen-activated nasal T cells. Furthermore, IgE production can occur locally in the nasal mucosa (target organ) and IgE itself can enhance the Fc epsilon RI expression and subsequent mediator release from NMC, thus contributing to the perpetuation of on-going allergic inflammation. Again, mast cells can contribute to the late-phase allergic reaction not only via the upregulation of adhesion molecules like VCAM-1, but also through the interactions of NMC with the extracellular matrix proteins, and interaction of NMC with nasal epithelial cells (NEC). Thus, it is increasingly evident that mast cells are not only important for the genesis of the allergic reaction, but also contribute to the late-phase allergic reaction and on-going allergic inflammation.