Oral Allergen Research Articles

EAAS4-3 Diagnosis of food allergies based on oral food challenges and allergen components(EAAS4 Food allergy and related diseases,Symposium 2,East Asia Allergy Symposium 2014)

EAAS4-3 Diagnosis of food allergies based on oral food challenges and allergen components(EAAS4 Food allergy and related diseases,Symposium 2,East Asia Allergy Symposium 2014)

Automated Detection of Perturbed Cardiac Physiology During Oral Food Allergen Challenge in Children

This paper investigates the fully automated computer-based detection of allergic reaction in oral food challenges using pediatric ECG signals. Nonallergic background is modeled using a mixture of Gaussians during oral food challenges, and the model likelihoods are used to determine whether a subject is allergic to a food type. The system performance is assessed on the dataset of 24 children (15 allergic and 9 nonallergic) totaling 34 h of data. The proposed detector correctly classified all nonallergic subjects (100% specificity) and 12 allergic subjects (80% sensitivity) and is capable of detecting allergy on average 17 min earlier than trained clinicians during oral food challenges, the gold standard of allergy diagnosis. Inclusion of the developed allergy classification platform during oral food challenges recorded would result in a 30% reduction of doses administered to allergic subjects. The results of study introduce the possibility to halt challenges earlier which can safely advance the state of clinical art of allergy diagnosis by reducing the overall exposure to the allergens.

Galactose 6-O-Sulfotransferases Are Not Required for the Generation of Siglec-F Ligands in Leukocytes or Lung Tissue

Eosinophil accumulation is a characteristic feature of the immune response to parasitic worms and allergens. The cell surface carbohydrate-binding receptor Siglec-F is highly expressed on eosinophils and negatively regulates their accumulation during inflammation. Although endogenous ligands for Siglec-F have yet to be biochemically defined, binding studies using glycan arrays have implicated galactose 6-O-sulfate (Gal6S) as a partial recognition determinant for this receptor. Only two sulfotransferases are known to generate Gal6S, namely keratan sulfate galactose 6-O-sulfotransferase (KSGal6ST) and chondroitin 6-O-sulfotransferase 1 (C6ST-1). Here we use mice deficient in both KSGal6ST and C6ST-1 to determine whether these sulfotransferases are required for the generation of endogenous Siglec-F ligands. First, we characterize ligand expression on leukocyte populations and find that ligands are predominantly expressed on cell types also expressing Siglec-F, namely eosinophils, neutrophils, and alveolar macrophages. We also detect Siglec-F ligand activity in bronchoalveolar lavage fluid fractions containing polymeric secreted mucins, including MUC5B. Consistent with these observations, ligands in the lung increase dramatically during infection with the parasitic nematode, Nippostrongylus brasiliensis, which is known to induce eosinophil accumulation and mucus production. Surprisingly, Gal6S is undetectable in sialylated glycans from eosinophils and BAL fluid analyzed by mass spectrometry. Furthermore, none of the ligands we describe are diminished in mice lacking KSGal6ST and C6ST-1, indicating that neither of the known galactose 6-O-sulfotransferases is required for ligand synthesis. These results establish that ligands for Siglec-F are present on several cell types that are relevant during allergic lung inflammation and argue against the widely held view that Gal6S is critical for glycan recognition by this receptor.

IKKβ in intestinal epithelial cells regulates allergen-specific IgA and allergic inflammation at distant mucosal sites.

Regulation of allergy responses by intestinal epithelial cells remain poorly understood. Using a model of oral allergen sensitization in the presence of cholera toxin as adjuvant and mice with cell-specific deletion of IKKβ in intestinal epithelial cells IECs (IKKβΔIEC), we addressed the contribution of IECs to allergic sensitization to ingested antigens and allergic manifestations at distant mucosal site of the airways. Cholera toxin induced higher proinflammatory responses and altered the profile of the gut microbiota in IKKβΔIEC mice. Antigen-specific IgE responses were unaltered in IKKβΔIEC mice, but their IgA Abs, Th1 and Th17 responses were enhanced. Upon nasal antigen challenge, these mice developed lower levels of allergic lung inflammation, which correlated with higher levels of IgA Abs in the airways. The IKKβΔIEC mice also recruited a higher number of gut-sensitized T cells in the airways after nasal antigen challenge and developed airway hyper-responsiveness, which were suppressed by treatment with anti-IL-17A. Fecal microbiota transplant during allergic sensitization reduced Th17 responses in IKKβΔIEC mice, but did not affect IgA Ab responses. In summary, we show that IKKβ in IECs shapes the gut microbiota and immune responses to ingested antigens and influences allergic responses in the airways via regulation of IgA Ab responses.

Specific oral immunotherapy versus allergen avoidance for food allergy in children: systematic review and meta-analysis (update)

I 2 = 87.4%, 95% confidence interval (CI), 73-94.1%). The relative risk (RR) of allergy was lower after SOTI (RR = 0.36; 95% CI, 0.18-0.75). The meta-regression showed no relation between SOTI efficacy (log(RR)) and the duration of the protocol or the age of patients. Compared with control, the RR of adverse events during SOTI ranges from to 0.18 to 2.33 and no significant correlation with RR of allergy is detected. Conclusion

Somnolence upon Allergen Provocation in a Child with Hen's Egg Allergy

Recent epidemiological data reveal that food allergies highly affect the pediatric population and are an increasing cause for hospitalization. Typical food allergic symptoms range from mild, local symptoms, such as itching, swelling, nausea, vomiting and diarrhea, to systemic anaphylactic symptoms, like airway swelling, hypotension and arrhythmias (Boden SR et al., Immunol Rev 2011; 242: 247–257, Kirchlechner V et al., Klin Padiatr 2007; 219: 201–205). Although the appearance of these symptoms may facilitate the diagnosis of food allergy, diagnostics of food adverse reactions in the pediatric population is particularly difficult, as the patient or patient’s parents can often not communicate allergic symptoms appropriately. Therefore, objective screening tests including measurements of total and allergen specific IgE, skin prick testing (SPT) and the golden standard of food allergy diagnosis, the double blind placebo controlled food challenge (DBPCFC), are conducted especially in the young age groups. DBPCFC is not only of importance for diagnostic purpose, but is substantial for determination of threshold levels, which enable physicians to adequately advise patients or parents. Oral allergen provocations are carried out under hospital settings, due to possible adverse reactions, such as anaphylaxis, following international guidelines of NIAID (National Institute of Allergy and infectious Disease) (Boyce JA et al., J Allergy Clin Immunol 2010; 126: S1–58) and EAACI (European Academy of Allergy and Clinical Immunology). Increasing doses of the challenging food are given at 30 min intervals until the top dose has been reached, or the patient reports an objective symptom, which ensures the correct diagnosis of food allergy and which is the basis for dietary recommendations or therapeutic measures.

Proposed new mechanism for food and exercise induced anaphylaxis based on case studies

We present two cases of food and exercise-induced anaphylaxis (FEIA) in patients with a diagnosis of oral allergy syndrome (OAS) to the implicated foods. Patient A had FEIA attributed to fresh coriander and tomato and Patient B to fresh celery. These food allergens have been implicated in OAS and have structural antigenic similarity to that of birch and/or grass. Both patients’ allergies were confirmed by fresh skin prick tests. In both cases, strenuous exercise was antecedent to the systemic anaphylaxis reaction and subsequent ingestion without exercise produced only local symptoms of perioral pruritus. We review the current proposed mechanisms for food and exercise induced anaphylaxis to oral allergens and propose a novel and more biologically plausible mechanism. We hypothesize that the inhibitory effects of exercise on gastric acid secretion decreases the digestion of oral allergens and preserves structural integrity, thereby allowing continued systemic absorption of the allergen whether it be profilins, lipid transfer proteins, or other antigenic determinants.

Epicutaneous sensitization results in IgE-dependent intestinal mast cell expansion and food-induced anaphylaxis

Sensitization to food antigen can occur through cutaneous exposure. We sought to test the hypothesis that epicutaneous sensitization with food antigen predisposes to IgE-mediated anaphylaxis on oral allergen challenge. BALB/c mice were epicutaneously sensitized by repeated application of ovalbumin (OVA) to tape-stripped skin over 7 weeks or orally immunized with OVA and cholera toxin (CT) weekly for 8 weeks and then orally challenged with OVA. Body temperature was monitored, and serum mouse mast cell protease 1 levels were determined after challenge. Tissue mast cell (MC) counts were examined by using chloroacetate esterase staining. Levels of serum OVA-specific IgE and IgG(1) antibodies and cytokines in supernatants of OVA-stimulated splenocytes were measured by means of ELISA. Serum IL-4 levels were measured by using an in vivo cytokine capture assay. Epicutaneously sensitized mice exhibited expansion of connective tissue MCs in the jejunum, increased serum IL-4 levels, and systemic anaphylaxis after oral challenge, as evidenced by decreased body temperature and increased serum mouse mast cell protease 1 levels. Intestinal MC expansion and anaphylaxis were IgE dependent because they did not occur in epicutaneously sensitized IgE(-/-) mice. Mice orally immunized with OVA plus CT did not have increased serum IL-4 levels, expanded intestinal MCs, or anaphylaxis after oral challenge, despite OVA-specific IgE levels and splenocyte cytokine production in response to OVA stimulation, which were comparable with those of epicutaneously sensitized mice. Epicutaneously sensitized mice, but not mice orally immunized with antigen plus CT, have expansion of intestinal MCs and IgE-mediated anaphylaxis after single oral antigen challenge. IgE is necessary but not sufficient for food anaphylaxis, and MC expansion in the gut can play an important role in the development of anaphylaxis.

T Lymphocyte-mediated suppression of murine granulopoiesis by oral allergen pretreatment of sensitized/challenged mice

T Lymphocyte-mediated suppression of murine granulopoiesis by oral allergen pretreatment of sensitized/challenged mice

Mucosal Immunity and Sublingual Immunotherapy in Respiratory Disorders

The prevalence of allergic diseases, specially respiratory allergic diseases such as allergic rhinitis and asthma, has been increasing worldwide for the last 2 decades [1, 2]. Although avoidance of the responsible allergen, anti-inflammatory, and symptomatic treatment modalities has shown great efficacy in the treatment of allergic respiratory disorders, cessation of pharmacotherapy usually results in recurrence of signs and symptoms, with a demand to restart the treatment. Currently, allergen-specific immunotherapy (SIT) is the only available curative choice with the capacity of altering the natural course of allergy [3, 4]. Although SIT by the subcutaneous route has been extensively used and has shown marked efficacy since its discovery, it was associated with uncommon, but severe or even fatal, systemic reactions [5]. Consequently, alternative, noninjectve allergen delivery routes have been proposed, and allergen delivery through mucosal surfaces was suggested as a possible mechanism for the induction of mucosal tolerance to allergens [5, 6]. Local mucosal routes such as oral, nasal, bronchial, and sublingual were investigated since then, and controlled trials failed to demonstrate satisfactory clinical efficacy and/or safety of oral, nasal, and bronchial allergen application; therefore those routes have been abandoned [7–11]. Meanwhile, the efficacy and safety of SIT via the sublingual route was well documented by a number of controlled trials both in children and adults with asthma and/or rhinitis [12, 13]. Since then, sublingual immunotherapy (SLIT) in the liquid drop formulation has been tested in a large number of double-blinded, placebo-controlled studies, and those studies were included in Cochrane meta-analyses [14–16] demonstrating efficacy both in children and adults with allergic rhinitis or asthma sensitized to house dust mite or various pollens. Thereafter, orodispersible grass-pollen tablets were developed and recent well-designed, well-powered, double-blinded, placebo-controlled studies demonstrated efficacy and safety of tablet formulation [17–20]. Some of those studies improved our understanding of the underlying immunological mechanisms in addition to the proven safety and efficacy. Recent studies demonstrated that SLIT exerts its immune-suppressive effect through the induction of Treg cytokines such as IL-10 and TGF-beta [21, 22]. This effect starts on the uptake of allergen by oral mucosal Langerhans cells through high-affinity IgE receptors [6]. More recent studies demonstrated increase in expression of Foxp3+ cells in the sublingual mucosa, which was accompanied by the systemic immunologic response during SLIT [23]. Hereby in this issue, data on clinical implications, efficacy, compliance, monitorization of delivery, and immunological mechanisms of allergen SIT delivered by the mucosal-mainly sublingual route will be presented. Nerin N. Bahceciler

Suppression of the basophil response to allergen during treatment with omalizumab is dependent on 2 competing factors

A recent study of subjects with peanut allergy treated with omalizumab generated some results that were concordant with a study of subjects with cat allergy treated with omalizumab. However, there were differences that provided additional insight into the nature of the cellular responses in allergic subjects. We sought to determine the cause for failure to suppress the allergen-induced basophil response during treatment with omalizumab. Patients with peanut allergy were treated with omalizumab. Clinical, serologic, and cellular indices relevant to the response of the subjects and their peripheral blood basophil values (specific/total IgE ratio, cell-surface FcεRI expression, and histamine release responses to anti-IgE antibody or peanut allergen) were obtained at 3 times. After treatment, approximately 60% of the subjects' basophil responses to peanut allergen did not significantly decrease. In 40% of cases, the in vitro basophil response to peanut allergen increased 2- to 7-fold. The increases were associated with 2 primary factors: a high (>10%) specific/total IgE ratio and an increase in the intrinsic response of the basophil to IgE-mediated stimulation. The extent to which the basophil response to peanut allergen increased was inversely correlated with improvement in the patient's ability to tolerate ingestion of peanut. The basophil response during treatment with omalizumab is a consequence of 2 competing factors: suppression of allergen-specific IgE on the cell surface versus increased intrinsic sensitivity to IgE-mediated stimulation. In subjects with peanut allergy, the basophil response appears to mitigate against the ability of omalizumab to improve the patient's tolerance of oral allergen.

Oral immunotherapy induces local protective mechanisms in the gastrointestinal mucosa

Oral immunotherapy (OIT) is a promising treatment for food allergy. Studies are needed to elucidate mechanisms of clinical protection and to identify safer and potentially more efficacious methods for desensitizing patients to food allergens. We established a mouse model of OIT to determine how the dose or form of antigen may affect desensitization and to identify mechanisms of desensitization. Increasing doses of egg white or ovomucoid as OIT were administered orally to sensitized mice. The impact of OIT on anaphylaxis elicited by oral allergen challenge was determined. Allergen-specific antibody and cytokine responses and mast cell and basophil activation in response to OIT were measured. Gene expression in the small intestine was studied by microarray and real-time PCR. OIT resulted in desensitization but not tolerance of mice to the allergen. OIT did not result in desensitization of systemic effector cells, and protection was localized to the gastrointestinal tract. OIT was associated with significant changes in gene expression in the jejunum, including genes expressed by intestinal epithelial cells. Extensively heated ovomucoid that does not trigger anaphylaxis when given orally to sensitized mice was as efficacious as native ovomucoid in desensitizing mice. OIT results in clinical protection against food-induced anaphylaxis through a novel mechanism that is localized to the intestinal mucosa and is associated with significant changes in small intestinal gene expression. Extensively heating egg allergen decreases allergenicity and increases safety while still retaining the ability to induce effective desensitization.

A shorter and more specific oral sensitization-based experimental model of food allergy in mice

Cow's milk protein allergy (CMPA) is one of the most prevalent human food-borne allergies, particularly in children. Experimental animal models have become critical tools with which to perform research on new therapeutic approaches and on the molecular mechanisms involved. However, oral food allergen sensitization in mice requires several weeks and is usually associated with unspecific immune responses. To overcome these inconveniences, we have developed a new food allergy model that takes only two weeks while retaining the main characters of allergic response to food antigens.The new model is characterized by oral sensitization of weaned Balb/c mice with 5 doses of purified cow's milk protein (CMP) plus cholera toxin (CT) for only two weeks and posterior challenge with an intraperitoneal administration of the allergen at the end of the sensitization period. In parallel, we studied a conventional protocol that lasts for seven weeks, and also the non-specific effects exerted by CT in both protocols.The shorter protocol achieves a similar clinical score as the original food allergy model without macroscopically affecting gut morphology or physiology. Moreover, the shorter protocol caused an increased IL-4 production and a more selective antigen-specific IgG1 response. Finally, the extended CT administration during the sensitization period of the conventional protocol is responsible for the exacerbated immune response observed in that model.Therefore, the new model presented here allows a reduction not only in experimental time but also in the number of animals required per experiment while maintaining the features of conventional allergy models. We propose that the new protocol reported will contribute to advancing allergy research.

Quand prescrire et comment interpréter le dosage des allergènes moléculaires en allergie alimentaire ?

Natural molecular allergens (present in extracts and purified from allergenic source materials) or recombinant allergens (produced by genetic engineering) are used more and more frequently in the diagnosis of food allergy. If diagnosis is still mainly clinically-based, additional tests are often necessary: prick tests with an extract or with raw food, and assays for IgE antibodies specific for the allergen source and for molecular allergens. The latter are not available for all foods and for many allergenic components of the same foods. They are a valuable aid for the differentiation of food allergy from a simple sensitization, for evaluation of the severity and the risk of persistence of the allergy, and for deciding whether or not to do an oral allergen challenge test. They are especially useful for cow's milk, peanut, hen's egg, wheat, shellfish and fish allergies.

409 Oral Allergy Syndrome and United Airways Disease

BackgroundThe airways and the upper digestive tract have a common embrional origin, and in sensitized subjects they can respond to allergens with an immediate reaction (asthma, rhinitis or oral allergy syndrome). We investigated the possible functional connection between respiratory tract and upper digestive tract by means of specific oral allergen challenges.MethodsPatients sensitized to birch and apple were subdivided in GROUP A (N = 12; asthma and rhinitis due to birch and OAS due to apple) GROUP B (N = 10; OAS due to apple without asthma/rhinitis); GROUP C (N = 8; asthma and rhinitis due to birch without OAS). Healthy subjects represented the control group D (N = 6). Oral provocation test with apple was performed out of the pollen season. Visual analog scale for eye, nose and mouth symptoms, spirometry, nasal eosinophil count and exhaled nitric oxide were assessed before and 6 hours after challenge.ResultsThere was no change in nasal and ocular symptoms before versus after challenge in all groups. On the contrary, in groups A and B the oral scores significantly increased after challenge (P < .001), whereas no change was seen in groups C and D. Exhaled nitric oxide and nasal eosinophils showed no change before versus after challenge in all groups. Nitric oxide was higher before and after challenge in groups A and C versus groups B and D. No change was een as well in forced vital capacity and forced expiratory volume in one second.ConclusionsIn the case of birch-apple syndrome, eating apple does not functionally or clinically affect the respiratory tract.

Allergen-induced IgE-dependent gut inflammation in a human PBMC–engrafted murine model of allergy

Humanized murine models comprise a new tool to analyze novel therapeutic strategies for allergic diseases of the intestine. In this study we developed a human PBMC-engrafted murine model of allergen-driven gut inflammation and analyzed the underlying immunologic mechanisms. Nonobese diabetic (NOD)-scid-γc(-/-) mice were injected intraperitoneally with human PBMCs from allergic donors together with the respective allergen or not. Three weeks later, mice were challenged with the allergen orally or rectally, and gut inflammation was monitored with a high-resolution video miniendoscopic system, as well as histologically. Using the aeroallergens birch or grass pollen as model allergens and, for some donors, also hazelnut allergen, we show that allergen-specific human IgE in murine sera and allergen-specific proliferation and cytokine production of human CD4(+) T cells recovered from spleens after 3 weeks could only be measured in mice treated with PBMCs plus allergen. Importantly, these mice had the highest endoscopic scores evaluating translucent structure, granularity, fibrin, vascularity, and stool after oral or rectal allergen challenge and a strong histologic inflammation of the colon. Analyzing the underlying mechanisms, we demonstrate that allergen-associated colitis was dependent on IgE, human IgE receptor-expressing effector cells, and the mediators histamine and platelet-activating factor. These results demonstrate that allergic gut inflammation can be induced in human PBMC-engrafted mice, allowing the investigation of pathophysiologic mechanisms of allergic diseases of the intestine and evaluation of therapeutic interventions.

A new insight into FEIA

Two cases of patients with food and exercise-induced anaphylaxis (FEIA) with confirmed allergies to oral allergy syndrome are herein presented. Patient A had food anaphylaxis to fresh coriander and tomato and Patient B to fresh celery. These food allergens have structural antigenic similarity to that of birch and/or grass. Both patients’ allergies were confirmed by fresh prick-to-prick tests. In both cases, strenuous exercise before the reaction was the only cofactor and the patients had absolutely no symptoms with the offending foods outside of exercise. The exercise had likely lowered the threshold for their reactions. The current literature propose that in FEIA, there is increased GI permeability, leading to enhanced allergen absorption [1]. However, van Nieuvenhoven et al found that intestinal permeability actually decreases with exercise [2]. In fact, Bi and Triadafilopoulos noted in their review that strenuous exercise delays gastric emptying of liquids and solids and inhibits gastric acid production [3]. These studies have led us to propose of a novel paradigm for the mechanism of FEIA. The general inhibitory effects of exercise on the GI tract decrease the digestion of oral allergens, thus leaving the allergens more structurally intact and thereby allowing continued systemic absorption of the allergen. This mechanism is supported by Untersmayr and Jensen-Jarolim’s findings on the increased risk of labile food allergy induction with the use of antacid medications [4]. We propose the decrease in gastric acid in exercise as a more biologically plausible hypothesis of the mechanism of FEIA to oral allergens foods.

The functional connection between oral allergy syndrome and united airways disease assessed by oral challenge

BackgroundThe airways and the upper digestive tract have a common embryonic origin. In sensitized subjects they can respond to allergens with an immediate reaction (asthma, rhinitis, or oral allergy syndrome [OAS]). ObjectiveTo investigate the possible functional connection between respiratory and upper digestive tract by means of specific oral allergen challenges. MethodsPatients sensitized to birch and apple were subdivided into group A (n = 12; asthma + rhinitis caused by birch and OAS caused by apple); group B (n = 10; OAS caused by apple without asthma/rhinitis); group C (n = 8; asthma and rhinitis caused by birch without OAS). Healthy subjects represented the control group D (n = 6). Oral provocation test with apple was performed out of the pollen season. Visual analog scale for eye, nose, and mouth symptoms, spirometry, nasal eosinophil count, and exhaled nitric oxide were assessed before and 6 hours after challenge. ResultsNo change occurred in nasal and ocular symptoms before versus after challenge in all groups. On the contrary, in groups A and B the oral scores significantly increased after challenge (P < .001), whereas no change was seen in groups C and D. Exhaled nitric oxide and nasal eosinophils showed no change before versus after challenge in all groups. Nitric oxide was higher before and after challenge in groups A and C vs groups B and D. No change was seen in either forced vital capacity or forced expiratory volume in 1 second. ConclusionIn the case of birch-apple syndrome, eating apple does not functionally or clinically affect the respiratory tract.

Anti‐acid medication as a risk factor for food allergy

An important feature for oral allergens is their digestion-resistance during gastrointestinal transit. For some oral allergens, digestion stability is an innate feature, whereas digestion-labile antigens may only persist in times of impairment of the digestive system. In this review, we collect evidence from mouse and human studies that besides the inherent molecular characteristics of a food protein, the stomach function is decisive for the allergenic potential. Gastric acid levels determine the activation of gastric pepsin and also the release of pancreatic enzymes. When anti-ulcer drugs inhibit or neutralize gastric acid, they allow persistence of intact food allergens and protein-bound oral drugs with enhanced capacity to sensitize and elicit allergic reactions via the oral route. Mouse studies further suggest that maternal food allergy arising from co-application of a food protein with anti-acid drugs results in a Th2-biased immune response in the offspring. Especially, anti-ulcer drugs containing aluminum compounds act as Th2 adjuvants. Proton pump inhibitors act on proton secretion but also on expression of the morphogen Sonic hedgehog, which has been related to the development of atrophic gastritis. On the other hand, atrophic gastritis and resulting hypoacidity have previously been correlated with enhanced sensitization risk to food allergens in elderly patients. In summary, impairment of gastric function is a documented risk factor for sensitization against oral proteins and drugs.

Long-Term Characteristics of Hazelnut Allergy in an Adjuvant-Free Mouse Model

Background: Clinically it is recognized that tree nut allergies such as hazelnut allergy are not usually outgrown. Specific mechanisms underlying the persistence of such food allergies are incompletely understood. Here we studied the natural history and the long-term immune and clinical characteristics of hazelnut allergy in an adjuvant-free mouse model. Methods: BALB/c mice were sensitized to hazelnut protein using a transdermal sensitization protocol that does not use adjuvant. After establishing sensitization, exposure to hazelnut was withdrawn for 3, 5 or 8 months. The fate of circulating IgE antibodies was monitored. Subsequently, mice were given booster exposures and examined for memory IgE antibody and spleen cell IL-4 responses. Clinical characteristics and hypothermia responses upon oral allergen challenge were studied. Results: Upon allergen withdrawal, circulating hazelnut-specific IgE antibody levels began to drop. Nevertheless, IgE responses once established remained at significantly high levels for up to 8 months (the last time point studied) despite withdrawal of allergen exposure. Memory IgE responses to booster exposures were robust after 3, 5 or 8 months of allergen withdrawal. Furthermore, significant clinical reactivity to oral hazelnut challenge, and hypothermia responses were demonstrable at each of these time points. Long-lasting spleen cell memory IL-4 responses to hazelnut were detectable in these mice explaining the mechanism of sustenance of IgE responses and clinical sensitization. Conclusions: Hazelnut allergy once established persists for long periods, despite withdrawal of allergen exposure, due to long-lasting, memory IgE and IL-4 responses.