Induction Of IgE Responses Research Articles

Assessment of the Route of Exposure to Ovalbumin and Cow's Milk Proteins on the Induction of IgE Responses in BALB/c Mice.

Simple SummaryThe mouse model is very valuable to scientists, mainly because many reagents are commercially available for conducting research in this animal model. In the search for a standardized mouse model of food allergy, the route of administration of the proteins of interest is a determinant to successfully sensitizing the mice. Our aim was to evaluate the IgE allergen-specific response to food proteins after their administration by the intragastric or intraperitoneal routes in BALB/c mice. The results show that the intraperitoneal administration of the allergens ovalbumin or cow’s milk protein triggered more robust and consistent immunoglobulin E responses than the intragastric administration of the proteins, whether Sucralfate is used or not (an antacid that can promote sensitization in mice and an allergic response similar to the one triggered in human beings). It is concluded that the intraperitoneal administration of food proteins is better than the intragastric one to sensitize BALB/c mice, even after gastric-acid suppression. We have generated scientific evidence to pave the way in the search for a reproducible mouse model of immunoglobulin E-mediated food allergy to evaluate the safety of crops derived from modern biotechnology, such as genetic engineering, or the safety and effectiveness of new food allergy therapies.BALB/c mice can be orally sensitized to food proteins under acid suppressive medication, mimicking human exposure and triggering a human-like allergic immune response. However, the reproducibility of such an oral food allergy model remains questionable. Our aim was to evaluate the IgE responses triggered against ovalbumin (OVA) and cow’s milk proteins (CMP) after intragastric (IG), either under gastric-acid suppression or not, or intraperitoneal (IP) sensitization in BALB/c mice. OVA (0.2 mg) and different concentrations of CMP were administered with/without the antacid sucralfate by the IG route. For IP sensitization, OVA or CMP (0.5 mg) were administered. ELISA was used to evaluate IgE responses. The IP sensitization protocols triggered more robust and consistent anti-OVA or anti-CMP IgE responses than the intragastric ones (with/without sucralfate) (p < 0.05). 2.7% (1/36), and 5.5% (3/54) of the mice that underwent the sucralfate-assisted IG protocol triggered IgE responses against OVA or CMP, respectively. All the mice were administered OVA or CMP via IP triggered detectable IgE responses. The IP sensitization model is more reliable than the IG one for evaluating the intrinsic sensitizing and/or allergenic potential of food proteins, even if IG immunizations are carried out under gastric-acid suppression.

Cutaneous Exposure to Clinically Relevant Lone Star Ticks Promotes IgE Production and Hypersensitivity through CD4+ T Cell- and MyD88-Dependent Pathways in Mice.

Tick-borne allergies are a growing public health concern and have been associated with the induction of IgE-mediated food allergy to red meat. However, despite the increasing prevalence of tick bite-induced allergies, the mechanisms by which cutaneous exposure to ticks leads to sensitization and the production of IgE Abs are poorly understood. To address this question, an in vivo approach was used to characterize the IgE response to lone star tick proteins administered through the skin of mice. The results demonstrated that tick sensitization and challenge induced a robust production of IgE Abs and supported a role for IgE-mediated hypersensitivity reactions in sensitized animals following oral administration of meat. The induction of IgE responses was dependent on cognate CD4+ T cell help during both the sensitization phase and challenge phase with cutaneous tick exposure. In addition, IgE production was dependent on B cell-intrinsic MyD88 expression, suggesting an important role for TLR signaling in B cells to induce IgE responses to tick proteins. This model of tick-induced IgE responses could be used to study the factors within tick bites that cause allergies and to investigate how sensitization to food Ags occurs through the skin that leads to IgE production.

C5a Replaces IL-4 in Anti-CD40 + IL-4 Mediated Induction of IgE Responses By PBMC of Adult Allergic Asthmatic Humans

C5a Replaces IL-4 in Anti-CD40 + IL-4 Mediated Induction of IgE Responses By PBMC of Adult Allergic Asthmatic Humans

Genetic or pharmaceutical blockade of p110δ phosphoinositide 3-kinase enhances IgE production

Recent studies indicate that pharmaceutical blockade of phosphoinositide 3-kinase (PI3K) signaling enzymes might be effective in reducing allergic airway inflammation. Signals generated by the p110delta PI3K isoform play critical roles in signaling through antigen and cytokine receptors and were shown to be required for induction of type 2, but not type 1, cytokine responses. We sought to determine the effect of genetic or pharmaceutical inactivation of p110delta PI3K on induction of IgE responses. We determined the effect of p110delta inactivation on induction of systemic IgE responses and on the ability of purified B lymphocytes to undergo IgE isotype switch in vitro. IgG and IgE germline transcription, postswitch transcription, protein expression, and secretion were measured, as well as cell division and expression of activation-induced cytidine deaminase, an enzyme required for isotype switch. Paradoxically, inactivation of p110delta PI3K led to markedly increased IgE responses, despite reduced production of other antibody isotypes. This result was seen by using genetic inactivation of p110delta inhibition with IC87114 compound or blockade with the broad-spectrum PI3K inhibitors PIK-90 and PI-103. Significant increases in IgG1/IgE double-positive cells were observed, indicating that inactivation of PI3K leads to uncontrolled sequential switching from IgG1 to IgE. Disruption of p110delta signaling results in increased germline transcription at the epsilon locus and increased activation-induced cytidine deaminase expression, suggesting deregulation at the level of the isotype switch process. Blockade of PI3K signaling leads to markedly enhanced B-cell switch to IgE and increased IgE levels in vivo, despite reduced type 2 cytokine production.

Can persistent IgE responses be suppressed?

Since the discovery ofIgE in the late 1960s (Ishizaka, Ishizaka & Hornbrook, 1966; Johansson & Bennich, 1967) several animal models have been developed to study the regulation of IgE. IgE responses in atopic people are typically long lived and can be maintained when they are no longer exposed to allergen as in hay fever patients outside the pollen season. Such responses have proved difficult to produce in most species, with the exception of mice, and after an initial burst of IgE when first immunized, the response generated is rapidly suppressed. The artificial induction of IgE responses in rodents has required the use of adjuvants such as aluminium hydroxide and Bordatella pertussis or concomitant nematode infection (Jarrett & Stewart, 1972). T cells play a central role in regulating IgE responses (Okumura & Tada, 197 la; Katona, Urban & Finkelman, 1988), and as well as providing help for IgE B cells, they are capable of suppressing both primary and secondary IgE responses (Okumura & Tada, 1971b; Holt, Batty & Turner, 1981a). Thus two opposing functions for T cells in IgE regulation can be seen. These effects are mediated at least in part by T cell-derived cytokines. High levels of interleukin-4 (IL-4) were found to potentiate IgE synthesis from lipopolysaccharide (LPS) stimulated murine B cells in vitro (Coffman & Carty, 1986) and this effect could be antagonized with interferon-gamma (IFN-y) (Snapper & Paul, 1987). Anti-IL-4 antibody (Finkelman et al., 1986, 1988a) or IFN-y (Finkelman et al., 1988b) both suppress antigen and Nippostrongylus braziliensis-induced IgE responses in vivo. With N. braziliensis infestation, IgE levels spontaneously decline following worm expulsion but similar effects were also seen with anti-IL-4 and IFN-y in Heligmosomoides polygyrusinfested mice, where the worm is not expelled and IgE levels do not fall (Finkelman et al., 1990). The secondary IgE response produced with antigen and Al(OH)3 was largely but not completely inhibited with anti-IL-4 (Finkelman et al., 1990); these investigators conclude that the role of IL-4 in the maintenance of an IgE response is to recruit

Prediction of the allergenicity of a molecule

Resume This presentation addresses the question as to whether it is possible to predict whether proteins will become allergens. The molecular properties of inhaled allergens and food allergens are now well known and detailed analysis of their structures have not revealed common structural features or specific motifs that are associated with induction of IgE responses. Rather, allergen dose, route of exposure and aerodynamic properties appear to be key properties that promote IgE responses in genetically predisposed individuals. These include repeated exposure to low doses of allergen (1–10 μg/year) without adjuvant on airborne particles of 10–40 μ diameter. Food allergens tend to be heat stable and pH resistant proteins that account for a high percentage of the total protein in foods such a milk, egg, peanut, fish and soybeans. Predictions of allergenicity have particular relevance to the food biotechnology industry, where proteins that would not normally be part of the food supply are being introduced in genetically modified foods. Decision tree based approaches have been developed to assess whether genetically modified foods have the potential to become allergenic. Using structural information and exposure assessments, it is possible to make rational predictions about the potential allergenicity of protein molecules.

Induction of IgE Responses Using a Recombinant Mosquito Salivary Allergen rAed a 2 without Adjuvant in Mice

Background: Reactions to mosquito bites are a global problem. Several salivary proteins from Aedes (Ae.) aegypti, the most common mosquito species, have been cloned and expressed. Plasmid DNA vaccination has been shown to be effective in the downregulation of IgE responses. To investigate the in vivo antigenicity of these recombinant proteins and to study the mechanisms underlying plasmid DNA vaccination, a mouse model sensitized with a recombinant antigen has been developed. Methods: BALB/c and C57BL/6 mice were injected intradermally with a 37–kD recombinant Ae. aegypti salivary allergen (rAed a 2) in the absence of adjuvant twice weekly for 8 weeks and then challenged twice with rAed a 2 at weeks 10 and 12. Serum rAed a 2–specific IgE, IgG1 and IgG2a were measured by ELISA. Intradermal tests were performed every 4 weeks. The binding capacity of rAed a 2–specific IgE to the native Aed a 2 was examined by immunoblotting. Results: In both strains, sensitization with rAed a 2 induced a significant increase in IgE and IgG1, but not IgG2a. In all sensitized mice, a positive immediate skin reaction was apparent, while delayed–type hypersensitivity reactions were not observed. BALB/c mice produced significantly higher levels of IgE and IgG1 and larger wheals than C57BL/6 mice. The IgE antibodies elicited by rAed a 2 bound to not only rAed a 2 but also its natural form in mosquito saliva. Conclusion: (1) Repeated injections of rAed a 2 without adjuvant induce predominant Th2–type responses in mice. (2) BALB/c mice are better responders for IgE production than C57BL/6 mice. (3) rAed a 2 has identical allergenicity to its natural form.

Cytokines Involved in the Pathophysiology of IgE Response

Recent data in both mouse and human systems have clearly indicated that IL-4 plays an essential role in the induction of IgE response, whereas IFN-γ exerts an opposite effect on this phenomenon. However, IL-4 alone is unable to induce IgE synthesis. A prior membrane contact signal delivered by activated T cells is required by B cells to synthesize IgE in response to IL-4. A cognate interaction between B and T cells producing IL-4 (but not IFN-γ) is optimal for induction of IgE synthesis. However, when such IL-4 producing T cells are activated, they may provide B cells with a membrane signal, through a non-cognate interaction, which also results in induction of IgE synthesis. Other cytokines, such as IL-2 and IL-6, play an auxiliary role in IL-4 dependent IgE production. Analyses at the clonal level of the profile of cytokine production by helper T cells have shown that imbalances between IL-4 and IFN-γ producing T cells can be detected in patients with hyperproduction of IgE. In children with hyper-IgE syndrome a strong reduction of circulating T cells able to produce IFN-γ (and TNF-α) was found, whereas both, reduction of IFN-γ-producing and increase of IL-4 producing T cells were found in patients with parasitic infestation. In allergic inflammatory infiltrates, such as those found in vernal conjuctivitis, helper T cells able to produce IL-4 and to induce IgE synthesis accounted for the large majority of infiltrating T cells. It is reasonable to suggest that systemic or microenvironmental alterations of the balance between IL-4- and IFN-γ-producing T cells may be involved, at least in part, in the pathophysiology of the increased igE response occurring in a number of human diseases.