Cell-bound IgE Research Articles

IgE Depletion with Ligelizumab Does Not Significantly Improve Clinical Symptoms in Patients with Moderate-to-Severe Atopic Dermatitis

The value, if any, of anti-IgE approaches in the treatment of atopic dermatitis (AD) has not been fully clarified. Studies using the anti-IgE omalizumab have yielded conflicting results. Antibodies with an IgE-suppressive capacity stronger than omalizumab might be more efficacious. We assessed safety and efficacy of the high-affinity anti-IgE antibody ligelizumab (280mg s.c., every other week) in 22 adult patients with moderate-to-severe atopic dermatitis in a placebo and active (cyclosporine A) controlled, randomized, multicenter, double-blind clinical trial for twelve weeks. We found that ligelizumab treatment resulted in either complete (patients with baseline IgE<1500IU/ml) or partial (baseline IgE>1500IU/ml) suppression of serum and cell-bound IgE as well as of allergic skin prick tests. On the other hand, ligelizumab- as opposed to cyclosporine A -was not significantly superior to placebo in inducing Eczema Area and Severity Index 50 response or significantly reducing pruritus and sleep disturbance. Interestingly though, patients with high baseline IgE exhibited a slightly, but not significantly better treatment response than those with low baseline IgE. Our study shows that an immunologically efficacious anti-IgE approach is not clearly superior to placebo in treating AD. Larger studies are needed to determine whether certain patient subgroups may benefit from this strategy. The study was registered in 2011 at clinicaltrialsregister.eu, EudraCT Number 2011-002112-84.

Skin Testing Is Useful in Assessing Aeroallergen Sensitization in IgE Deficient Patients with Environmental Allergy-Like Symptoms.

The value of aeroallergen skin testing is not known in IgE deficient individuals (IgE<2.5 kU/L). To investigate the utility of skin prick (SPT), intradermal skin testing (IDST) and measuring serum specific IgE (ssIgE) in IgE deficient patients presenting with environmental allergy-like symptoms. Individuals with IgE deficiency who had both SPT and IDST performed between 2010 to 2020 were matched (age and gender) to three different groups of non-IgE deficient patients with IgE≥2.5 kU/L (normal IgE [2.5 ≤ IgE<100], high IgE [100≤IgE<1000] and very high IgE levels [≥1000 kU/L]) who also had skin testing performed for evaluation of environmental allergy-like symptoms. Among 34 IgE deficient patients who completed SPT and IDST, 52.9% (18/34) had at least one positive skin test (4 ± 3 positive tests/patient), compared with 91.2% in those with normal, 94.1% with high or 97.1% with very high IgE levels (p < 0.01). In contrast, only one of the IgE deficient patients had detectable ssIgE, while ssIgE levels were significantly higher in all other IgE subgroups. Allergic immunotherapy was prescribed for 22.2% of the IgE-deficient patients with positive skin tests, similar to those with normal (2/31, 6.5%, p = 0.21), high IgE (9/32, 28.1%, p = 0.25) and very high IgE levels (8/33, 23.5%, p = 0.07), with similar efficacy in their symptoms control. Individuals with IgE deficiency may present with environmental allergy-like symptoms. A combination of SPT and IDST is useful for diagnosing aeroallergen sensitizations in these patients, indicating the presence of skin mast cell-bound IgE in some of these individuals, despite very low serum IgE levels. Further studies are needed to assess the exact significance of positive skin tests and the benefits of immunotherapy in this group.

Omalizumab response correlates with reduced IFN-γ-, IL-10- and IL-31-secreting cells in chronic spontaneous urticaria.

The anti-IgE antibody omalizumab has been approved for the treatment of chronic spontaneous urticaria (CSU) in patients insufficiently responding to antihistamines. However, its mode of action in CSU is not clearly understood. The aim of this study was to get a better insight in the immune mechanisms involved in clinical improvement of CSU patients treated with omalizumab. Chronic spontaneous urticaria patients (n=15) were followed for 5months after initiation of omalizumab treatment. Clinical symptoms were assessed by UCT and CU-Q2 oL. Cell-bound IgE was quantified on both FcεRI- and FcεRII-expressing cell populations in peripheral blood. In addition, IgE and IgG as well as their receptors were measured on basophils, and basophil activation was assessed with different concentrations of anti-FcεRI and fMLP. Furthermore, the frequencies of different T-cell subsets secreting IL-5, IL-10, IL-31 or IFN-γ were analysed by ELISpot assay. Seven patients showed a full, five a partial and three no clinical response to omalizumab. Cell-bound IgE was reduced on FcεRI-bearing cells, but not on FcεRII-expressing cells. Likewise, the expression of FcεRI declined. Basophil activation increased upon FcεRI-stimulation while their sensitivity was not affected. Both basophil and T-cell frequencies remained unchanged. However, when comparing the individual response to omalizumab treatment with distinct T-cell subsets, a significant correlation was found between improved UCT and decreased frequencies of IL-10-, IL-31- and IFN-γ-secreting T cells. We here show that besides addressing IgE-dependent immune mechanisms, omalizumab treatment of CSU patients has effects on distinct T-cell subsets, which correlate with clinical improvement.

Cell-bound IgE and plasma IgE as a combined clinical diagnostic indicator for allergic patients

Allergic responses are mainly caused by IgE, which is often located on the cell surface. The current diagnostic method detects both allergen-specific IgE and total IgE levels, but a number of allergic patients have a normal serum IgE level, which is a poor clinical correlate for allergy. Here, we developed a simple method to detect the level of cell-bound IgE by dissociating it from blood cells with lactic acid. Dissociated cell-bound IgE and plasma IgE levels were detected using the same ELISA kit at the same time. We established two clinical cohorts: an allergic patient group and a healthy participant group. In general, cell-bound IgE correlated well with plasma IgE; however, some patients exhibited high cell-bound IgE levels but low plasma IgE levels. We recommended 350 ng/mL peripheral blood total IgE (cell-bound IgE + plasma IgE) as the cut-off value for allergy diagnosis. Using this indicator, 90.32% of our allergic patients were correctly diagnosed. The peripheral blood total IgE level is a promising clinical diagnostic indicator in allergic patients and will provide more guidance for allergy diagnosis and therapeutic evaluation.

Laser-facilitated epicutaneous immunotherapy with depigmented house dust mite extract alleviates allergic responses in a mouse model of allergic lung inflammation.

Skin-based immunotherapy of type 1 allergies has recently been re-investigated as an alternative for subcutaneous injections. In the current study, we employed a mouse model of house dust mite (HDM)-induced lung inflammation to explore the potential of laser-facilitated epicutaneous allergen-specific treatment. Mice were sensitized against native Dermatophagoides pteronyssinus extract and repeatedly treated by application of depigmented Dpteronyssinus extract via laser-generated skin micropores or by subcutaneous injection with or without alum. Following aerosol challenges, lung function was determined by whole-body plethysmography and bronchoalveolar lavage fluid was analyzed for cellular composition and cytokine levels. HDM-specific IgG subclass antibodies were determined by ELISA. Serum as well as cell-bound IgE was measured by ELISA, rat basophil leukemia cell assay, and ex vivo using a basophil activation test, respectively. Cultured lymphocytes were analyzed for cytokine secretion profiles and cellular polarization by flow cytometry. Immunization of mice by subcutaneous injection or epicutaneous laser microporation induced comparable IgG antibody levels, but the latter preferentially induced regulatory T cells and in general downregulated T cell cytokine production. This effect was found to be a result of the laser treatment itself, independent from extract application. Epicutaneous treatment of sensitized animals led to induction of blocking IgG, and improvement of lung function, superior compared to the effects of subcutaneous therapy. During the whole therapy schedule, no local or systemic side effects occurred. Allergen-specific immunotherapy with depigmented HDM extract via laser-generated skin micropores offers a safe and effective treatment option for HDM-induced allergy and lung inflammation.

Therapeutic potential of peptides from Ole e 1 in olive-pollen allergy

Olive-pollen allergy is one of the leading causes of respiratory allergy in Mediterranean countries and some areas of North America. Currently, allergen-specific immunotherapy is the only etiophatogenic treatment. However, this approach is not fully optimal, safe, or effective. Thus, efforts continue in the search for novel immunotherapy strategies, being one of the most promising the use of peptides derived from major allergens. This work tries to determine the therapeutic potential and safety of 5 dodecapeptides derived from the main allergen of olive-pollen allergy, Ole e 1. The immunomodulatory capacity of these peptides was studied using peripheral blood mononuclear cells (PBMCs) obtained from 19 olive-pollen-allergic patients and 10 healthy controls. We determined the capacity of these peptides to inhibit the proliferative response toward olive-pollen allergenic extract and to induce the regulatory cytokines, IL-10 and IL-35. To test the safety and absence of allergenicity of the peptides, the basophil activation was analyzed by flow-cytometry, using peripheral blood. The results showed that two of five peptides inhibited near to 30% the proliferative response against the total olive-pollen allergenic extract in olive-pollen-allergic patients. Inhibition increased to nearly 35% when the 5 peptides were used in combination. In both cases, a statistically significant induction of IL-10 and IL-35 secretion was observed in the supernatants of allergic patients PBMCs cultures. None of the 5 peptides induced basophil activation and cross-link inflammatory cell-bound IgE. In conclusion, these results open up new possibilities in the treatment of olive-pollen allergy, which could solve some of the problems facing current therapy approaches.

Fusion proteins consisting of Bet v 1 and Phl p 5 form IgE-reactive aggregates with reduced allergenic activity

The cross-linking of effector cell-bound IgE antibodies by allergens induces the release of inflammatory mediators which are responsible for the symptoms of allergy. We demonstrate that a recombinant hybrid molecule consisting of the major birch (Bet v 1) and grass (Phl p 5) pollen allergen exhibited reduced allergenic activity as compared to equimolar mixes of the isolated allergens in basophil activation experiments. The reduced allergenic activity of the hybrid was not due to reduced IgE reactivity as demonstrated by IgE binding experiments using sera from allergic patients. Physicochemical characterization of the hybrid by size exclusion chromatography, dynamic light scattering, negative-stain electron microscopy and circular dichroism showed that the hybrid occurred as folded aggregate whereas the isolated allergens were folded monomeric proteins. IgG antibodies raised in rabbits against epitopes of Bet v 1 and Phl p 5 showed reduced reactivity with the hybrid compared to the monomeric allergens. Our results thus demonstrate that aggregation can induce changes in the conformation of allergens and lead to the reduction of allergenic activity. This is a new mechanism for reducing the allergenic activity of allergens which may be important for modifying allergens to exhibit reduced side effects when used for allergen-specific immunotherapy.

Recruiting CD33 on mast cells to inhibit IgE-mediated mast cell-dependent anaphylaxis.

IgE-mediated activation of mast cells is a hallmark of an anaphylactic reaction to allergen. In this issue of the JCI, Duan et al. describe an approach for suppressing IgE-dependent mast cell activation, thereby suppressing anaphylaxis. Specifically, the authors show that delivery of liposomes containing both the specific antigen recognized by the mast cell-bound IgE and a high-affinity glycan ligand of the inhibitory receptor CD33 (CD33L) to targeted mast cells inhibits antigen-induced, FcεRI-dependent spleen tyrosine kinase (Syk) phosphorylation and downstream protein tyrosine kinase (PTK) phosphorylation, Ca++ flux, and β-hexosaminidase release (i.e., degranulation). However, this strategy only worked if both the antigen (reactive with the mast cell-bound IgE) and CD33L were on the same liposome. This approach promises to rapidly reduce IgE-dependent mast cell activation in response to challenge with offending allergens.

Characterization of inflammatory infiltrate of ulcerative dermatitis in C57BL/6NCrl-Tg(HMGA1P6)1Pg mice.

Ulcerative dermatitis (UD) is an idiopathic, spontaneous and progressive disease typically affecting C57BL/6 aged mice with an unknown aetiopathogenesis. For this study, we evaluated 25 cases of UD in C57BL/6NCrl-Tg(HMGA1P6)1Pg mice. Formalin-fixed, paraffin-embedded skin samples were submitted to morphological investigations. Immunohistochemical analysis was performed to characterize and quantify inflammatory cells using CD3, CD45/B220, CD4, CD8 and IL-17 antibodies. Mast cell-bound IgE was investigated by immunofluorescence, whereas serum and cryopreserved skin samples were collected for molecular analysis. Student's t-test (two-tailed) was performed to assess significant differences between the two groups. Affected skin showed extensive areas of ulceration and diffuse, severe and mixed inflammatory infiltrates. No relevant changes were observed in control mice. Immunohistochemical analysis showed a predominant CD3 + CD4 + leukocyte population with fewer CD45/B220 and IL-17 immunolabelled cells and mast cell-bound IgE. Increases in TNFα, IL-1β and Il-6 mRNA expression were observed in the skin of affected animals compared to controls. Serum TNFα and IL-6 did not vary between affected and control mice. Inflammatory infiltrates and cytokine expression were consistent with both Th2/IgE and Th17 differentiation, a typical pattern of a type I hypersensitivity reaction. Overall, our data suggest an allergic-based aetiopathogenesis of UD in C57BL/6NCrl-Tg(HMGA1P6)1Pg mice.

IL-3 but not monomeric IgE regulates Fc\u03b5RI levels and cell survival in primary human basophils

Binding of allergen-specific IgE to its primary receptor FcεRI on basophils and mast cells represents a central event in the development of allergic diseases. The high-affinity interaction between IgE and FcεRI results in permanent sensitization of these allergic effector cells and critically regulates their release of pro-inflammatory mediators upon IgE cross-linking by allergens. In addition, binding of monomeric IgE has been reported to actively regulate FcεRI surface levels and promote survival of mast cells in the absence of allergen through the induction of autocrine cytokine secretion including interleukin-3 (IL-3). As basophils and mast cells share many biological commonalities we sought to assess the role of monomeric IgE binding and IL-3 signaling in FcεRI regulation and cell survival of primary human basophils. FcεRI cell surface levels and survival of isolated blood basophils were assessed upon addition of monomeric IgE or physiologic removal of endogenous cell-bound IgE with a disruptive IgE inhibitor by flow cytometry. We further determined basophil cell numbers in both low and high serum IgE blood donors and mice that are either sufficient or deficient for FcεRI. Ultimately, we investigated the effect of IL-3 on basophil surface FcεRI levels by protein and gene expression analysis. Surface levels of FcεRI were passively stabilized but not actively upregulated in the presence of monomeric IgE. In contrast to previous observations with mast cells, monomeric IgE binding did not enhance basophil survival. Interestingly, we found that IL-3 transcriptionally regulates surface levels of FcεRI in human primary basophils. Our data suggest that IL-3 but not monomeric IgE regulates FcεRI expression and cell survival in primary human basophils. Thus, blocking of IL-3 signaling in allergic effector cells might represent an interesting approach to diminish surface FcεRI levels and to prevent prolonged cell survival in allergic inflammation.

A 13-year real-life study on efficacy, safety and biological effects of Vespula venom immunotherapy

BackgroundHymenoptera venom immunotherapy (VIT) is a clinically effective treatment. However, little is known about its long-term clinical efficacy and biological effects. Several mechanisms have been proposed to account for VIT efficacy, including reduction of specific IgE and induction of allergen-specific IgG4, but the overall picture remains elusive. We investigated Vespula VIT clinical efficacy up to 8 years after discontinuation and the kinetics of Vespula-specific IgE and IgG4. Out of 686 consecutive patients we retrospectively selected and analysed a series of 23 patients with Vespula allergy that underwent a 5-year IT course, followed by a prolonged follow-up.MethodsClinical efficacy of VIT was assessed as number and severity of reactions to Vespula re-stinging events. The presence of Vespula-specific IgE and IgG4 was also monitored over time.ResultsDuring the VIT treatment, patients were protected, reporting no reactions or mild reactions in occasion of re-stinging events. This protection was entirely maintained during the follow-up, up to 8 years. Skin reactivity (reflecting mast cell-bound Vespula-specific IgE) and circulating Vespula-specific IgE levels declined substantially during VIT. Notably, this reduction was maintained over time during the follow-up. Moreover, all the patients were analysed for IgG4. A robust induction of Vespula-specific IgG4 was observed during the VIT course, with a substantial decline during the follow-up.ConclusionsWe conclude that Vespula VIT is a clinically effective treatment, which induces long-term protection after discontinuation. The reduction of specific IgE, assessed by skin tests and RAST, closely matches the VIT- induced protection, while the IgG4 induction seems not to be associated with VIT clinical efficacy in the long term.

Flexible IgE epitope-containing domains of Phl p 5 cause high allergenic activity

This is the first study determining the three-dimensional structure of Phl p 5a which reveals a novel mechanism for high allergenic activity based on flexibly connected IgE-reactive domains which cross-link effector cell-bound IgE more efficiently than isolated rigid globular proteins. These findings may also form a basis for specific immunotherapy strategies.

Lifelong memory responses perpetuate humoral TH2 immunity and anaphylaxis in food allergy

A number of food allergies (eg, fish, shellfish, and nuts) are lifelong, without any disease-transforming therapies, and unclear in their underlying immunology. Clinical manifestations of food allergy are largely mediated by IgE. Although persistent IgE titers have been attributed conventionally to long-lived IgE+ plasma cells (PCs), this has not been directly and comprehensively tested. We sought to evaluate mechanisms underlying persistent IgE and allergic responses to food allergens. We used a model of peanut allergy and anaphylaxis, various knockout mice, adoptive transfer experiments, and invitro assays to identify mechanisms underlying persistent IgE humoral immunity over almost the entire lifespan of the mouse (18-20months). Contrary to conventional paradigms, our data show that clinically relevant lifelong IgE titers are not sustained by long-lived IgE+ PCs. Instead, lifelong reactivity is conferred by allergen-specific long-lived memory B cells that replenish the IgE+ PC compartment. B-cell reactivation requires allergen re-exposure and IL-4 production by CD4 T cells. We define the half-lives of antigen-specific germinal centers (23.3days), IgE+ and IgG1+ PCs (60 and 234.4 days, respectively), and clinically relevant cell-bound IgE (67.3days). These findings can explain lifelong food allergies observed in human subjects as the consequence of allergen exposures that recurrently activate memory B cells and identify these as a therapeutic target with disease-transforming potential.

Signal Transduction from the High Affinity IgE Receptor

Mast cells and basophils synthesize and store histamine, proteoglycans, and proteases in their granules and have surface receptors (FceRI) that bind IgE with high affinity. The interaction of multivalent antigen with this cell-bound IgE results in aggregation of FceRI and activation of the cells to release an array of inflammatory mediators. These mediators include the granular contents, arachidonic acid from phospholipids produced by the action of phospholipase enzymes, and cytokines such as tumor necrosis factor (TNF-α). Unlike the rapid release within minutes of preformed mediators, release of most cytokines is a slow process that requires several hours. This chapter reviews the current understanding of these intracellular pathways; most of this information is based on studies with the rat basophilic leukemia RBL-2H3 cultured mast cell line.

Structural basis of omalizumab therapy and omalizumab-mediated IgE exchange.

Omalizumab is a widely used therapeutic anti-IgE antibody. Here we report the crystal structure of the omalizumab–Fab in complex with an IgE-Fc fragment. This structure reveals the mechanism of omalizumab-mediated inhibition of IgE interactions with both high- and low-affinity IgE receptors, and explains why omalizumab selectively binds free IgE. The structure of the complex also provides mechanistic insight into a class of disruptive IgE inhibitors that accelerate the dissociation of the high-affinity IgE receptor from IgE. We use this structural data to generate a mutant IgE-Fc fragment that is resistant to omalizumab binding. Treatment with this omalizumab-resistant IgE-Fc fragment, in combination with omalizumab, promotes the exchange of cell-bound full-length IgE with omalizumab-resistant IgE-Fc fragments on human basophils. This combination treatment also blocks basophil activation more efficiently than either agent alone, providing a novel approach to probe regulatory mechanisms underlying IgE hypersensitivity with implications for therapeutic interventions.

Identification of IgE

Progress in protein chemistry in the 1950s revealed that the biologic activities of proteins, such as hemoglobin and enzymes, are based on partial structures in the protein molecules. This principle suggested to us the possibility that the human antibodies responsible for induction of reaginic hypersensitivity reactions might have unique structures that are lacking in the antibody molecules involved in immunity and that the differences in the structures of human antibody molecules can be recognized by the immune systems of experimental animals. Our studies were based on the hypothesis that reaginic antibody activity is associated with a unique immunoglobulin isotype, which is now called IgE. As expected, identification of IgE facilitated the analysis of immunologic mechanisms of reaginic hypersensitivity. Subsequent studies revealed that IgE specifically bound to basophilic granulocytes and mast cells through the Fc portion of the molecules and that cross-linking of the cell-bound IgE antibody molecules by allergen induced the release of bioactive mediators, such as histamine and leukotrienes, which initiate allergic reactions.

Omalizumab: a review of its use in patients with chronic spontaneous urticaria.

Omalizumab (Xolair(®)) is a humanized, recombinant, IgG, anti-IgE monoclonal antibody that binds to the Fc region of free IgE and prevents it from binding to its high-affinity receptor (FcεR1) on mast cells and basophils. This reduction in free IgE leads to a reduction in mast cell/basophil degranulation and the release of histamine, and to the down-regulation of FcεR1 receptors on these cells. Omalizumab does not bind to cell-bound IgE or to IgG. In well-controlled clinical trials in patients with chronic spontaneous urticaria and persistent symptoms despite background treatment with antihistamines, add-on therapy with subcutaneous omalizumab 300mg every 4weeks for 12 or 24weeks significantly reduced the severity of itching, and the number and size of hives, and increased patients' health-related quality of life and the proportion of days free from angioedema compared with placebo. Subcutaneous omalizumab was generally well tolerated; the incidence and severity of adverse events in omalizumab recipients were similar to those in placebo recipients, and most adverse events were of mild or moderate severity. The only adverse events occurring more frequently with omalizumab than with placebo during treatment in a safety study were headache and upper respiratory tract infection. Thus, omalizumab is an effective and well-tolerated add-on therapy in patients with chronic spontaneous urticaria who are symptomatic despite background therapy with H1 antihistamines.

Anaphylactic transfusion reaction in homozygous haptoglobin deficiency detected by CD203c expression on basophils

To the Editor: It has been reported that the incidence of anhaptoglobinemia who are homozygous for Hpdel is very rare in Africans or European-Africans. However, it is relatively high incidence in East Asian; 1/4,000 in Japan, 1/1,500 in Korea, and 1/1,000 in China 1. Some patients with anhaptoglobinemia develop anaphylactic or allergic transfusion reactions related to antihaptoglobin (Hp) antibodies 2. However, if anti-Hp IgE antibody is negative, it is difficult to elucidate an anaphylactic reaction. Flow cytometric basophil activating test (BAT) based on upregulation of the cell degradation/activation marker CD203c has been developed for monitoring the clinical course of patients with allergic diseases 3, 4. Here, we describe that BAT was a useful tool for diagnosing anaphylactic transfusion reaction associated with anti-Hp antibody. This case was an 8-year-old Japanese boy with acute lymphoblastic leukemia receiving intensive chemotherapy required transfusion. He was transfused with 14 units of leukocyte-reduced red cell concentrates (RCCs) and 150 units of leukocyte-reduced platelet concentrates for chemotherapy-induced anemia and thrombocytopenia without any transfusion-related reactions. However, immediately after starting the next infusion of RCCs, he developed dyspnea, urticaria, and hypotension. Screening tests for nonhemolytic transfusion reactions (NHTRs) were performed at the Japanese Red Cross. Serum analysis by nephelometry revealed Hp deficiency and their PCR method 1 showed complete absence of the Hp gene. He was diagnosed as having anhaptoglobinemia due to homozygous allelic Hpdel. Although anti-Hp IgG antibody was detected by ELISA and Western blotting, IgE antibody against Hp was not detected by ELISA or the IgE crosslinking-induced luciferase expression (EXiLE) test 5. To address the mechanism of this anaphylactic reaction, we performed BAT. As a control, a healthy adult and five age-matched children with severe egg allergy who had histories of food-induced anaphylaxis were examined. A commercial kit (Allergenicity Kit; Beckman Coulter, Fullerton, CA) was used for quantifying basophil CD203c expression 4. Upregulation of CD203c on basophils was determined using a threshold that was defined by the fluorescence of unstimulated cells and expressed as CD203c high % 6. CD203c high % was 23% for the patient and 4.38 ± 0.53% for the control, respectively (Table I). Haptoglobin induced enhancement of CD203c expression in the patient, but not in the control. Since basophils express high-affinity IgE receptors, it is reasonable to assume that the haptoblobin-induced basophil activation observed in the patient was mediated by haptoglobin-specific IgE bound to basophils. We did not detect antihaptoglobin IgE by the ELISA or EXiLE methods, but it is possible that the serum IgE concentration was too low to be detected, whereas the amount of cell-bound IgE was sufficient to induce anaphylaxis. Another possibility is that haptoglobin-specific IgG induced basophil activation. An IgG-mediated systemic anaphylactic reaction involving FcγRs, basophils, and platelet-activating factor was reported in a murine system 7, although it remains unclear whether such an IgG-mediated pathway also exists in humans. Our findings indicate that BAT may be useful for assessing the cause of NHTRs, especially anaphylactic reactions via high-affinity IgE receptors on basophils, leading to development of type I hypersensitivity response when no IgE can be detected in serum. The authors thank Yumi Tanaka, MSc (Blood Transfusion Service, Mie University Hospital) for kindly blood supplies. This work was supported by a Research Grant for Allergic Disease and Immunology (H20-015) from the Japanese Ministry of Health, Labor, and Welfare. Shotaro IwamotoMD, PHD, Takahiro YonekawaMD, Eiichi AzumaMD, PHD Pediatrics Unit, Mie University School of Medicine, Mie, Japan Takao FujisawaMD, PHD, Mizuho NagaoMD, PHD Clinical Research Unit, Mie National Hospital, Mie, Japan Eiko ShimadaMSC Central Blood Institute Unit, Blood Service Headquarters Japanese Red Cross Society, Tokyo, Japan Ryosuke NakamuraPHD, Reiko TeshimaPHD, Novel Foods and Immunochemistry Unit, National Institute of Health Sciences, Mie, Japan Kohshi OhishiMD, PHD Blood Transfusion Service Unit, Mie University Hospital, Mie, Japan Hidemi ToyodaMD, PHD, Yoshihiro KomadaMD, PHD Pediatrics Unit, Mie University School of Medicine, Mie, Japan

Enhanced cell‐binding by allergen multimers: how complex is it?

Allergic diseases are the most common chronic disease of the western world, costing $7.8 billion per year in lost productivity and medical care in Australia alone.1 IgE is central to the immunopathogenesis of allergic diseases and important advances are now being made on multiple fronts of IgE research. In particular, two groups independently invested in the generation of IgE reporter mice to address the vexing question of the route of development of the elusive IgE+ B cell.2, 3 Two new anti-IgE mAb targeting membrane IgE and cell-bound IgE have the potential to deplete the cellular source of IgE.4, 5 These could be candidates for alternative anti-IgE treatment options with advantages over current anti-IgE therapy (OmalizumAb), which depletes free serum IgE. Researchers are still intrigued by the modes of interaction of IgE with allergen, and with both its receptors; the high affinity FceR1 on mast cells and basophils, and the low affinity, C-type lectin, IgE receptor, CD23,6 on B cells and monocytes (Figure 1a and b). A new approach to the study of the complexity of these interactions was recently reported by Reginald et al.7 on page 167 of this issue.

Hypersensitivity reactions to the Sabin vaccine in children with cow's milk allergy

The Sabin vaccine is used world-wide, and most children with food allergies receive it without incident. However, in the 2009 vaccination campaign conducted in Argentina, four children experienced immediate-type hypersensitivity reactions following vaccination. We aimed to review the medical history of the affected children, study their allergic condition after the episodes and analyse the presence of allergenic vaccine components. Patients were selected based on their immediate allergic reactions following vaccination. They were assessed for allergies to cow's milk and hen's egg. The presence of cow's milk proteins in the vaccine was tested by various immunoassays involving cow's milk- or α-lactalbumin-specific polyclonal rabbit antiserum and patient sera. All of the patients had a history of milk allergy, and no history or current evidence of egg hypersensitivity was found. Levels of cow's milk- and Sabin vaccine-specific IgE were increased, and the result of a skin prick test with cow's milk proteins or the Sabin vaccine was positive in each patient. In addition, an ELISA using specific rabbit antiserum detected α-lactalbumin in the Sabin vaccine. When α-lactalbumin was employed as a soluble inhibitor in a competitive ELISA, binding to vaccine-coated plates by cow's milk- or α-lactalbumin-specific rabbit antiserum or by patient serum containing IgE was inhibited. We have demonstrated that these patients were allergic to cow's milk, and had circulating and mast cell-bound IgE antibodies specific to cow's milk proteins. We found that the Sabin vaccine contained α-lactalbumin, which may have been responsible for the reactions elicited following vaccination with the Sabin and dual viral vaccines in combination.