IgE Responses In Mice Research Articles

The role of the stress‐activated transcription factor Nrf2 in OVA‐induced food allergy

Immune-mediated adverse reactions to food allergens are rising at a striking rate, but the underlying cause is unknown. The purpose of the present studies was to determine the effect of the food preservative tert-butylhydroquinone (tBHQ) on anaphylaxis in a mouse model of food allergy. Our preliminary studies demonstrate that skin-sensitization with OVA induced a markedly higher OVA-specific IgE response in mice on a tBHQ diet. Likewise, in response to OVA challenge by the oral route, a greater decrease in body temperature during anaphylaxis was observed in the tBHQ-treated group. Previously published in vitro studies suggest that tBHQ promotes Th2 polarization, a key step in the development of allergy, through activation of the stress-activated transcription factor, Nrf2. Therefore, we proposed the hypothesis that tBHQ exacerbates allergic response in ovalbumin (OVA) sensitized mice through activation of Nrf2. We implemented adoptive transfers of CD4 T cells from wild-type or Nrf2-null mice into immunodeficient SCID mice (all mice also received wild-type B cells). The study revealed marked genotype differences. Notably, dietary tBHQ had little effect on food allergy in recipients of Nrf2-deficient CD4 T cells. These mice showed markedly attenuated sensitization as compared to mice who received wild-type CD4 T cells. Strikingly, mice receiving Nrf2-deficient T cells did not become anaphylactic following OVA challenge. In contrast, tBHQ caused an increase in OVA-IgE plasma levels and a greater drop in body temperature in mice receiving wild-type CD4 T cells, suggesting these effects are Nrf2 dependent. In addition, recipients of Nrf2-deficient CD4 T cells showed a greatly attenuated percentage of Th2 cells and mucosal mast cell degranulation response, following OVA challenge. Taken together, these data suggest a critical role for Nrf2 during food allergen-induced sensitization and anaphylaxis and demonstrate that tBHQ exacerbates food allergy in a CD4 T cell- Nrf2 dependent manner in mice.

The B-cell antigen receptor of IgE-switched plasma cells regulates memory IgE responses

Allergic inflammation is driven by IgE-producing plasma cells (PCs), which are required for IgE-mediated activation of mast cells and basophils. Repeated antigen encounter elicits a memory IgE response with elevated serum IgE titers and accumulation of IgE-producing PCs. However, the cellular compartment and molecular signals that underlie the immunologic memory of IgE responses remain unclear. With this study we aimed at clarifying whether inactivation of the cytoplasmic immunoglobulin tail tyrosine (ITT) motif in transmembrane IgE (mIgE) impairs the memory IgE response in mice. We generated mice with an inactivated mIgE-ITT motif and analyzed serum IgE levels as well as the generation of IgE-producing germinal center B cells and PCs subsequent to primary and secondary infection with helminths. Invitro cultures were used to study the mIgE-ITT-controlled expression of mIgE on the surface of PCs. Systemic mast cell activation was determined by serum Mcpt1 ELISA in response to ovalbumin challenge. mIgE-ITT-mutant mice showed an impaired memory IgE response subsequent to helminth infection. Furthermore, sensitization and challenge of mIgE-ITT-mutant mice with ovalbumin resulted in diminished serum IgE titers and reduced mast cell activation. The mIgE-ITT motif was required for optimal cell surface expression of mIgE B-cell antigen receptors but not for intracellular IgE expression in PCs. These results indicate that the mIgE B-cell antigen receptor plays a critical role in establishing or maintaining the population of IgE-producing PCs during memory IgE responses.

Profiles of IgM, IgG and IgE immune responses of mice against p14, p31 and p71 proteins following immunization with crude cystic fluid of Cysticercus bovis

Background: The presence of IgM, IgG and IgE antibodies has been widely used as important markers for the differentiation of acute and chronic infection in many infectious diseases, but limited studies reported on Cysticercus bovis infection are available. This study aimed to determine the IgM, IgG and IgE responses of mice against crude cystic fluid, p14, p31 and p71 antigens as the possible diagnosis of acute and chronic cysticercosis in hosts.Methods: Six mice were immunized four times at 10 days interval with Cysticercus bovis. Individual p14, p31 and p71 proteins were separated by using sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and elution of proteins from gel with elution buffer. The crude cystic fluid, p14, p31 and p71 were used as antigens for enzyme-linked immunosorbent assay (ELISA) to measure the IgM, IgG and IgE antibody titers in mice sera before and after the first, the second, the third and the fourth immunizations.Results: No IgM, IgG and IgE against crude cystic fluid, p14, p31, and p71 was detected in sera samples collected before the first immunization. Moderate to high titers of IgM antibodies against crude cystic fluid, p14, p31 and p71 were identified following the first, the second, the third and the fourth immunizations. IgG titers against crude cystic fluid, p14, p31 and p71 was still at a low level following the first immunization and started to increase following the second, the third and the fourth immunization. Generally, low titers of IgE antibodies against crude cystic fluid, p14, p31 and p71 were detected after each immunization. IgE responses only increased slightly against crude cystic fluid and p71 antigens after the third and the fourth immunizations. The IgM, IgG and IgE responses of mice against crude cystic fluid and p71 antigens were higher than those against p31 and p14 antigens.Conclusions: The presence of IgM without IgG and IgE can indicate acute infection, whereas the presence of IgM and IgG with slight increase IgE might indicate a chronic infection of Cysticercus bovis.

Gut oxidative responses by chronic exposure to pollutants enhance IgE production via PGE2-dependent mechanism

Abstract Environmental pollutants are believed to contribute to the increased incidence of allergic diseases. However, mechanisms linking exposure to pollutants with allergy are poorly understood and researches about heavy metals are mostly focused on its toxicity. Groups of mice were chronically exposed to subtoxic doses of cadmium in the drinking water. We then analyzed the impact of this exposure on gut immune homeostasis, microbiota, allergic sensitization to ingested allergen and subsequent allergic responses after allergen challenge. Chronic ingestion of subtoxic doses of cadmium increased IgE responses of mice to ingested allergen and the severity of allergy symptoms upon subsequent allergen challenge. We also found that exposure to subtoxic doses of cadmium induces dysbiosis of the gut microbiota and luminal accumulation of oxidized vitamin D3 metabolites. More importantly, we found that this microenvironment selectively enhances the activation of BAFF and the production of IgE via PGE2-dependent mechanism by intestinal epithelial cells. These findings reveal a new mechanism for the induction of IgE responses via alteration of vitamin D3 metabolism by environmental pollutants which stimulate an oxidative and inflammatory environment in the gut.

Endogenous Calcitriol Synthesis Controls the Humoral IgE Response in Mice

The vitamin D receptor participates in the control of IgE class-switch recombination in B cells. The physiologic vitamin D receptor agonist, 1,25(OH)2D3 (calcitriol), is synthesized by the essential enzyme 25-hydroxyvitamin D3-1α-hydroxylase (CYP27B1), which can be expressed by activated immune cells. The role of endogenous calcitriol synthesis for the regulation of IgE has not been proven. In this study, we investigated IgE-responses in Cyp27b1-knockout (KO) mice following sensitization to OVA or intestinal infection with Heligmosomoides polygyrus Specific Igs and plasmablasts were determined by ELISA and ELISpot, Cyp27b1 expression was measured by quantitative PCR. The data show elevated specific IgE and IgG1 concentrations in the blood of OVA-sensitized Cyp27b1-KO mice compared with wild-type littermates (+898 and +219%). Accordingly, more OVA-specific IgG1-secreting cells are present in spleen and fewer in the bone marrow of Cyp27b1-KO mice. Ag-specific mechanisms are suggested as the leucopoiesis is in general unchanged and activated murine B and T lymphocytes express Cyp27b1 Accordingly, elevated specific IgE concentrations in the blood of sensitized T cell-specific Cyp27b1-KO mice support a lymphocyte-driven mechanism. In an independent IgE-inducing model, i.e., intestinal infection with H. polygyrus, we validated the increase of total and specific IgE concentrations of Cyp27b1-KO compared with wild-type mice, but not those of IgG1 or IgA. We conclude that endogenous calcitriol has an impact on the regulation of IgE in vivo. Our data provide genetic evidence supporting previous preclinical and clinical findings and suggest that vitamin D deficiency not only promotes bone diseases but also type I sensitization.

Laser-facilitated epicutaneous immunotherapy to IgE-mediated allergy

Allergen specific immunotherapy has been shown to be the only effective treatment for long-lasting clinical benefit to IgE-mediated allergic diseases, but a fewer than 5% of patients choose the treatment because of inconvenience and a high risk of anaphylaxis. Recently, epicutaneous allergen-specific immunotherapy (EPIT) has proven effective, yet with limitations owing to strong skin reactions. We demonstrate here safer and faster EPIT, named μEPIT, by delivering powdered allergen and adjuvants into many micropores in the epidermis. We fabricated a microarray patch fractionally coated with a powder mixture of ovalbumin (OVA) model allergen, CpG, and 1,25-dihydroxyvitamin D3 (VD3). Topical application of the patch onto laser-microperforated skin resulted in a high level of epidermal delivery while greatly minimizing allergen leakage into circulation system as compared to current subcutaneous immunotherapy (SCIT). Moreover, only three times of μEPIT over two weeks could sufficiently inhibit allergen-specific IgE responses in mice suffering OVA-induced airway hyperresponsivness (AHR), which was unattainable by eight times of SCIT over three weeks. Mechanistically, μEPIT preferably enhanced IgG2a production suggesting TH1-biased immune responses and induced a high level of T-regulatory (Treg) cells against repeated allergen sensitization. The immune tolerance was confirmed by marked reduction in airway wall thickness as well as eosinophil and neutrophil infiltration into the respiratory airway. The μEPIT represents a novel and painless technology to treat IgE-mediated allergic diseases with little local skin reaction and a minimal risk of anaphylaxis.

Protease-Activated Receptor-2 Activation Contributes to House Dust Mite-Induced IgE Responses in Mice

Aeroallergens such as house dust mite (HDM), cockroach, and grass or tree pollen are innocuous substances that can induce allergic sensitization upon inhalation. The serine proteases present in these allergens are thought to activate the protease-activated receptor (PAR)-2, on the airway epithelium, thereby potentially inducing allergic sensitization at the expense of inhalation tolerance. We hypothesized that the proteolytic activity of allergens may play an important factor in the allergenicity to house dust mite and is essential to overcome airway tolerance. Here, we aimed to investigate the role of PAR-2 activation in allergic sensitization and HDM-induced allergic airway inflammation. In our study, Par-2 deficient mice were treated with two different HDM extracts containing high and low serine protease activities twice a week for a period of 5 weeks. We determined airway inflammation through quantification of percentages of mononuclear cells, eosinophils and neutrophils in the bronchial alveolar lavage fluid and measured total IgE and HDM-specific IgE and IgG1 levels in serum. Furthermore, Th2 and pro-inflammatory cytokines including IL-5, IL-13, Eotaxin-1, IL-17, KC, Chemokine (C-C motif) ligand 17 (CCL17) and thymic stromal lymphopoietin (TSLP), were measured in lung tissue homogenates. We observed that independent of the serine protease content, HDM was able to induce elevated levels of eosinophils and neutrophils in the airways of both wild-type (WT) and Par-2 deficient mice. Furthermore, we show that induction of pro-inflammatory cytokines by HDM exposure is independent of Par-2 activation. In contrast, serine protease activity of HDM does contribute to enhanced levels of total IgE, but not HDM-specific IgE. We conclude that, while Par-2 activation contributes to the development of IgE responses, it is largely dispensable for the HDM-induced induction of pro-inflammatory cytokines and airway inflammation in an experimental mouse model of HDM-driven allergic airway disease.

IgE peptide-specific CTL inhibit IgE production: A transient IgE suppression model in wild-type and HLA-A2.1 transgenic mice

Effect of IgE peptide-specific CTL on IgE antibody production was studied in mouse models. CTL elicited in B6.A2Kb tg mice against a human IgE peptide nonamer, pWV, lysed human IgE-secreting U266 myeloma cells and inhibit IgE production by these cells. U266 transfected with mouse A2Kb transgene (U266-A2Kb) were optimally lysed by these CTL, because the α3 domain of A2Kb interacts well with the CD8 co-receptors. The CTL generated were more effective in inhibiting IgE production by U266-A2Kb cells than lysing these cells. IgE production by and progression of U266 myeloma were suppressed in B6.A2Kb tg mice rendered tolerant to these cells and vaccinated with pWV along with CpG. We also studied the CTL response elicited in wild-type mice by a mouse nonameric IgE peptide, PI-1, along with CpG. This treatment caused a transient suppression of the IgE response in mice previously sensitized to an antigen. In mice treated with this regimen repeatedly, the IgE response was fully recovered 20 days after each treatment. Notably, while IgE peptide/CpG-treated mice remained unresponsive to antigen challenge in vivo, antigen-specific IgE production can be elicited by antigen in cultured splenocytes from these mice. Moreover, IgE peptide/CpG also inhibited an on-going IgE response, including IgE production by bone marrow cells. Taken together, these observations indicate that a CTL-based IgE peptide vaccine targeting IgE-secreting B/plasma cells may be safely employed as a therapeutic approach for suppressing IgE production.

Effects of Dietary Lactosucrose (4G-β-D-galactosylsucrose) on the IgE Response in Mice

In this study, we examined the effects of dietary lactosucrose (LS, a non-digestible oligosaccharide) on the IgE response in mice immunized with ovalbumin (OVA)/alum. In addition to IgG1 and IgG2a responses, the anti-OVA IgE response in mice fed LS diets was dose-dependently suppressed, as compared with the control mice, while the serum total IgG levels were comparable. Moreover, dietary LS feeding inhibited antigen-specific IgE and IgG1 productions even after a second immunization. Regarding with cytokine production, when stimulated in vitro with OVA, splenocytes obtained from LS-fed mice produced a similar level of IFN-gamma, and lower levels of IL-4 and IL-5, as compared with the control mice. But IL-10 production by OVA-stimulated splenocytes was augmented in LS-fed mice, suggesting that IL-10 producing cells are responsible for the immunoregulatory effect of LS. Our findings indicate the further possibility that dietary LS supplementation can be used to prevent IgE-mediated allergic diseases.

Dietary Pulverized Konjac Glucomannan Prevents the Development of Allergic Rhinitis-Like Symptoms and IgE Response in Mice

Konjac is a traditional Japanese food with a peculiar texture, and it has been suggested that its main ingredient, konjac glucomannan (KGM), ameliorates metabolic disorders such as diabetes and hypercholesteremia. We have found that feeding with pulverized KGM (PKGM) prevents skin inflammation in a murine model of atopic dermatitis. Here, we show that dietary PKGM suppresses allergic rhinitis-like symptoms in mice upon immunization and nasal sensitization with ovalbumin (OVA). The PKGM-fed mice showed a much lower frequency of sneezing than in control animals. We also found that PKGM supplementation exclusively suppressed OVA-specific IgE response without affecting IgG1/IgG2a responses as well as systemic Th1/Th2 cytokine production. These results suggest that PKGM can be a beneficial foodstuff in preventing nasal allergy such as seasonal pollinosis.

Intranasal sensitization with Blomia tropicalis antigens induces allergic responses in mice characterized by elevated antigen-specific and non-specific serum IgE and peripheral blood eosinophil counts.

In order to evaluate the potential allergenicity of Blomia tropicalis (Bt) antigen, IgE production of both specific and non-specific for Bt antigen was monitored in BALB/c mice after exposure to the antigen by nasal route. It was evidenced that B. tropicalis contains a functional allergen in its components. The allergenic components, however, when administered intranasally without any adjuvant, did not function to induce IgE response within a short period. On the other hand, intranasal inoculation of Bt antigens augmented serum IgE responses in mice pretreated by a subcutaneous priming injection of the same antigens. Inoculation of Bt antigen without subcutaneous priming injections induced IgE antibody production only when the antigen was continuously administered for a long period of over 24 weeks. Even when the priming injection was absent, the Bt antigen inoculated with cholera toxin (CT) as a mucosal adjuvant also significantly augmented the Bt antigen-specific IgE responses depending on the dose of CT co-administered. The present study also demonstrated that Bt antigen/CT-inoculated mice showed increased non-specific serum IgE level and peripheral blood eosinophil rates without noticeable elevations of the total leukocyte counts. The immunoblot analysis demonstrated 5 main antigenic components reactive to IgE antibodies induced. These components at about 44-64 kDa position were considered to be an important candidate antigen for diagnosis of the mite-related allergy.

Persistent secretion of IL-18 in the skin contributes to IgE response in mice.

After exposure of the skin to microbes, the host develops skin-specific inflammation and an acquired immune response, in which keratinocytes (KC) and Langerhans cells play critical roles respectively. We established two animal models. (i) We examined the importance of KC-derived IL-18 for the systemic IgE response by using a skin transplantation model. As previously reported, transgenic mice (KCASP1Tg), that over-express caspase-1 in their KC, display high serum levels of IgE, and spontaneously develop chronic dermatitis by production of IL-18 and IL-1beta. We examined the capacity of transplantation of cutaneous lesions from KCASP1Tg to induce IgE production in wild-type or mutant mice with a syngeneic background. Transplantation of active cutaneous lesions, that expressed high levels of IL-18 and IL-1beta, induced long-lasting IgE production in wild-type mice without elevation of circulating IL-18 and IL-1beta. Furthermore, IL-18R-, CD4- or stat6-deficient mice transplanted with the lesions did not produce IgE, indicating that this IgE response is initiated by IL-18, and dependent on host-derived CD4(+) T cells and stat6. (ii) We investigated IL-18 secretion from KC upon stimulation with microbe products. Freshly isolated KC from wild-type mice secreted IL-18 in response to Protein A purified from Cowan 1 strain of Staphylococcus aureus (SpA), which often exacerbates human skin diseases, including atopic dermatitis. Cutaneous application of SpA increased serum levels of IL-18 and IgE. These results indicate that local accumulation of IL-18 triggers systemic IgE responses without exposure to antigen.

IgE responses in mice fed moderate protein deficient and high protein diets.

While severe protein energy malnutrition (PEM) has been known to depress several immune functions, allergies are suppressed by decreasing IgE and impairing vascular permeability and mast cell functions. To address the effect of moderate protein malnutrition without growth arrest and protein hypernutrition on type I allergy, we examined the effect of various levels of protein nutrition on allergy at humoral immunity and the regulation of Th cell function levels. Mice fed 100 g/kg (moderate protein malnutrition; MPM), 200 g/kg (normal protein nutrition; PN) and 400 g/kg (protein hypernutrition; PH) protein diets were intraperitoneally sensitized to ovalbumin (OVA) in aluminum hydroxide. Higher elevations of OVA-specific IgE and total IgE in the serum were observed in the PH group as compared to the PN group. However, OVA-specific IgE in the MPM group was not significantly different from that in the PN group, although the former appeared higher than the latter. While CD3, CD4, CD8 and B220 expressions in the splenic lymphocytes were decreased in the MPM group, B220 expressions were increased in the PH group. Splenic lymphocyte proliferative responses to OVA were augmented in the PH group and depressed in the MPM group. IFN-gamma production from splenic lymphocytes was significantly decreased; however, IL-4 production was not affected significantly in the MPM group, and increased in the PH group. These findings suggest that immune functions to specific antigens in the MPM state are depressed at the cytokine level but not in terms of IgE responses. They also suggest that immune functions become Th2-predominant in the PH state, resulting in an increased risk of type I allergy.

A 24-kDa collagenase from Gymnorhynchus gigas elicits rat ileum hyperreactivity and is a target of humoral responses in mice previously given a single oral dose of parasite extract.

Fish declared fit to be eaten may contain plerocercoids (larvae) of the fish cestode Gymnorhynchus gigas. We showed previously that crude G. gigas larval extract given in a once-only oral dose to either mice or rats induces parasite-specific immediate-type responses and that this extract evokes increased contractile activity in normal rat ileums. We show here that a 24-kDa collagenase (24-kCol), purified from the crude extract is (1) a target of both local (intestinal) and systemic IgE responses in mice sensitized by oral G. gigas and (2) elicits considerable changes in rat ileum contractility. Exposure of rat ileum segments once to 7 microg 24-kCol significantly increased tone and amplitude, but not frequency, of contractions compared with control recordings. In all, these studies have indicated 24-kCol, an abundantly produced protein of G. gigas larvae, to be a participant in potentially serious/adverse intestinal responses in both mice and rats. Such responses are very likely to occur in "sensitized" humans also.

Genetic Immunisation with Bovine β-Lactoglobulin cDNA Induces a Preventive and Persistent Inhibition of Specific Anti-BLG IgE Response in Mice

Background: Various studies have shown that DNA immunisation with gene allergen induces a non-allergic response. Methods: We applied this new type of vaccination to bovine β-lactoglobulin (BLG), a major cow’s milk allergen, using a plasmid that allows the production of a partially secreted protein. Specific antibodies and cytokines were quantified in different immunisation protocols. Results: The primary response in mice immunised with BLG-encoding plasmid (pBLG) is of the Th1 type. Restricted recognition of a native form of BLG in pBLG mice contrasted with a broader range of recognition in BLG-in-alum-immunised mice, notwithstanding the fact that alum favours the presentation of a native form of the antigen. We also demonstrated an inhibitory effect of pDNA immunisation on the Th2 response induced by a subsequent immunisation using BLG adsorbed on alum. However, this preventive effect is highly dependent on the time of pre-administration of the pBLG, with an optimal effect when pDNA immunisation occurred at least 21 days before protein administration. This preventive effect resulted concomitantly in the inhibition of BLG-specific IgE, in the induction of specific IgG2a, and in the decrease of the specific IgG1/IgG2 ratio. It is accompanied by an increase in IFNγ and IL-10 secretion. Moreover, the preventive effect was shown to be persistent even after a booster immunisation with alum-adsorbed BLG. The Th1 orientation of the response is very likely due to the presentation of the protein in the Th1 environment due to plasmid immunostimulatory sequences, as intramuscular injection of BLG itself leads to a weak Th2 response and had no preventive effect on a subsequent sensitisation. Conclusion: This study further demonstrates the potential use of DNA immunisation for prevention of IgE response, but the window of action seems to be very restricted if we are to inhibit an established Th2 response efficiently.

Use of secondarily revised VH genes in IgE antibodies produced in mice infected with the nematode Nippostrongylus brasiliensis

Although a high level of IgE is produced after primary infection with Nippostrongylus brasiliensis (Nb), most of the IgE antibodies (Abs) are not specific to the worm. Analyses with Western blotting and enzyme-linked immunosorbent assay (ELISA) revealed that the IgE Abs from Nb-infected BALB/c mice did not show reactivity with Nb-derived excretory–secretory proteins (NES) and antigens present in the cell-free extracts of the worm. Monoclonal IgE Abs obtained from the Nb-infected mice were not reactive with these Nb antigen either. To characterize Nb-induced IgE response, we used (QM x C57BL/6)F1 (QBF1) mice that bear the knock-in 17.2.25 VHDJH segment (VHT) encoding a VH region specific to 4-hydroxy-3-nitrophenylacetyl hapten, and express VHT-encoded antigen receptors on 80–85% of their B cells. Consistent with the frequency of VHT-positive B cells, more than 80% of IgE Abs induced in QBF1 B cells that were cultured with LPS plus IL-4 were found to bear VHT-encoded H chains. In contrast, when QBF1 mice were infected with Nb, less than 10% of Nb-induced IgE Abs were found to use VHT. The QBF1-derived IgE did not react with Nb antigens either. Taken together, data suggest that Nb-induced IgE response in mice is not merely the result of polyclonal activation of B cells, but may involve a mechanism that revises Ig genes secondarily.

CpG oligodeoxynucleotide vaccination suppresses IgE induction but may fail to down-regulate ongoing IgE responses in mice.

Antigen-specific IgE plays an important role in the pathogenesis of allergic disorders. Immunostimulatory CpG motifs (CpG) in bacterial DNA or synthesized oligodeoxynucleotides (ODN) are gaining recognition as potential immunomodulators for switching on protectiveT(h)1-mediated immunity and preventing or potentially inhibiting T(h)2-dependent allergic responses. To date, allergic models used in CpG ODN studies have been established by immunization of mice with allergen in the presence of adjuvant. This, in addition to failure to assess specific IgE production in most of the studies, has limited understanding of the role of CpG ODN vaccination in allergic responses. Here, we examine the effects of synthesized CpG ODN on both developing and ongoing IgE responses in mice sensitized using a recombinant mosquito salivary antigen (rAed a 2) without adjuvant. Pretreatment of mice with CpG ODN mixed with rAed a 2 successfully inhibited subsequent induction of serum rAed a 2-specific IgE (but not IgG1) and antigen-induced IL-4 and IL-5 production in spleen cells. This was associated with an increase of serum IgG2a and IL-12, and increased IFN-gamma and IL-12 production by spleen cells. In this model, however, co-administration of CpG ODN with rAed a 2 to presensitized mice failed to down-regulate ongoing IgE responses despite significant up-regulation of serum IL-12 and specific IgG2a. Strikingly, a transient skin delayed-type hypersensitivity reaction occurred in CpG ODN-treated mice. These observations provide a new insight into the potential therapeutic application of CpG ODN to allergic disorders.

Dietary Nucleotides Can Up-Regulate Antigen-Specific Th1 Immune Responses and Suppress Antigen-Specific IgE Responses in Mice

Background: It has been reported that dietary nucleotides enhance T helper cell activities. In this study, we have determined the effects of dietary nucleotides on antigen-specific Th1 and Th2 responses and IgE responses. Methods: Ovalbumin (OVA)-specific T cell receptor (TCR) transgenic (OVA-TCR Tg) mice, 3 weeks old, were fed a nucleotide-free diet (NT(–) diet) or the NT(–) diet supplemented with dietary nucleotides (NT(+) diet) for 4 weeks. Cytokine production by spleen cells and macrophages obtained from these mice was measured in vitro. BALB/c mice, 3 weeks old, immunized intraperitoneally with OVA adsorbed onto alum, were fed the NT(–) diet or the NT(+) diet for 4 weeks. Serum levels of antigen-specific antibodies in the BALB/c mice were determined by ELISA. Results: The level of production of antigen-specific interferon-γ by spleen cells was significantly higher in the OVA-TCR Tg mice fed the NT(+) diet than in the control mice. The levels of secretion of bioactive IL-12 by spleen cells and peritoneal macrophages were also significantly increased in the NT(+) diet group. The serum OVA-specific IgE level was significantly decreased in BALB/c mice fed the NT(+) diet compared with those fed the NT(–) diet. Conclusion: These results show that dietary nucleotides up-regulate the antigen-specific Th1 immune response through the enhancement of IL-12 production and suppress the antigen-specific IgE response.

Relationships between natural T cells, atopy, IgE levels, and IL-4 production.

Th2 cells govern allergic disorders. Mechanisms leading to the Th2 commitment are dominated by the requirement of IL-4. A potential source of this triggering IL-4 could be the CD4 + subset of a small population of T cells, natural T (NT) cells. Indeed, this subset is involved in IgE responses in mice and produces promptly high amounts of IL-4 in both mice and man. NT cells were identified in peripheral blood by flow cytometry with antibodies against Valpha24 and Vbeta11, recognizing the T-cell receptor specific for NT cells. Simultaneous staining with anti-CD3, anti-CD4, or anti-CD8 antibodies was performed. The frequency of NT cells in man was studied according to the presence of atopy defined by the positivity of skin tests, according to total IgE levels in serum, and according to IL-4 concentration of whole-blood culture supernatants determined by a flow cytometer microsphere-based assay. Seventy subjects were included, of whom 30 were atopic. The number of CD4+ NT cells was higher in atopics than in nonatopics (P=0.009). This number was correlated to the total IgE levels (r = 0.34, P = 0.03). In addition, the number of CD4 + NT cells, but also of CD8 + NT cells, was correlated to the levels of IL-4 (r=0.71, P=0.01, and r=0.6, P=0.03, respectively). These results show that the number of NT cells, particularly the CD4+ subset, is related to atopy, IL-4 production, and IgE levels. Therefore, this population of T cells is likely to play a role in the Th2 commitment initiating atopic diseases.

Selective augmenting effects of nitric oxide on antigen-specific IgE response in mice

Here, we report the enhancing effects of nitric oxide (NO) on an IgE antibody response in mice. Anti-trinitrophenyl (TNP) IgE production induced in vitro in TNP keyhole limpet hemocyanin (KLH)-primed spleen cells was inhibited by approximately 70% when an NO synthase (NOS) inhibitor, l-NG-monomethyl-l-arginine, was added at 10−7–10−6 M to the lymphocyte culture. On the other hand, addition of NO-generating agents to the culture resulted in a marked enhancement of the IgE production. In contrast, anti-TNP IgM and IgG1 responses were affected only marginally when the IgE production was either suppressed or augmented by these agents. NO did not directly augment IgE class switching in normal B cells stimulated with lipopolysaccharide and interleukin (IL)-4. NO-mediated augmentation of the IgE response is considered to be of a physiological significance because administration of aminoguanidine (AG), an inhibitor of inducible NOS, to immunized mice resulted in a preferential suppression of anti-TNP IgE production in vivo. This may be explained by the observation that AG-administration increased interferon-γ expression without changing that of IL-4 in the immunized mice. Taken together, these observations suggest a pathophysiological role of NO in the development of IgE-mediated allergic diseases.