Basophil Response Research Articles

Platelet Proteins Cause Allergic Transfusion Reactions through an Immunoglobulin-Dependent Mechanism

Background: A general understanding of allergic transfusion reaction (ATR) mechanisms remains elusive. Various hypotheses invoke proteins, small molecules, mitochondria, or microparticles that may be plasma or platelet derived and suggest antibody dependent or independent mechanisms. There has been no systematic comparison of these proposed mechanisms. The aim of this study is to characterize the mechanistic determinants of ATRs.Methods: Basophil enriched cell suspensions were collected from healthy donors (n=8). Basophil histamine release was measured in response to platelet-derived components: platelet component supernatant (plasma), platelet lysate, and manipulated platelet lysates were examined to characterize the unknown allergic stimuli. Lysate manipulations were: 1) dialysis against a 3,500 molecular weight cutoff membrane, 2) butanol/DIPE delipidation, 3) trypsinization with immobilized trypsin beads, 4) mild heat denaturation at 47˚C for 20 minutes, and 5) ultracentrifugation at 200,000 gfor 1hr. Immunoglobulin-dependent mechanisms were investigated through lactic acid immunoglobulin depletion from the basophil cell surface and signaling inhibition with ibrutinib. Histamine release from magnetic bead isolated platelet mitochondria was compared to platelet lysate with or without DNase treatment. Platelet lysate histamine content represented an average of <4% of total basophil histamine content. The residual histamine originating from platelet lysate was subtracted from post-reaction histamine concentrations. Atopic histories and grass, tree, and weed-specific IgE were measured in basophil donors.Results: Robust, dose-responsive histamine release to platelet lysate was observed in two of eight healthy donors. No histamine release was observed with plasma. Reactivity did not correlate with the clinical allergic phenotype, and reactive donors were nulliparous and had no prior transfusion. Trypsin treatment of platelet lysate reduced histamine release by 39% (p=0.008). Delipidation of platelet lysate decreased histamine release by 20% (p=0.051). Dialysis, ultracentrifugation, and mild heat denaturation of platelet lysate did not significantly affect histamine release, compared to unmanipulated platelet lysate. To investigate the immunoglobulin dependence of basophil activation, in separate experiments we 1) depleted immunoglobulins, including IgE, from the basophil cell surface, and 2) inhibited immunoglobulin-mediated intracellular signaling with ibrutinib. Histamine release in response to platelet lysate significantly decreased in both cases. Finally, isolated platelet mitochondria induced minimal basophil histamine release, and DNase treatment did not inhibit activation of basophils by platelet lysate.Conclusion: Type I immediate hypersensitivity to platelet, not plasma, proteins is a primary mechanism for ATRs. Small molecules, microparticles, and mitochondria are not significant contributors to ATRs in this human basophil model. Prior sensitization to human proteins is not required for basophil responses to platelet proteins. Donor variability and storage conditions that promote accumulation of soluble platelet-derived proteins may contribute to ATRs. DisclosuresNo relevant conflicts of interest to declare.

Distinct Contributory Factors Determine Basophil-Allergen Sensitivity in Grass Pollen Rhinitis and in Anaphylactic Wasp Venom Allergy

Background: We sought to determine whether basophil-allergen sensitivity could be transferred to donor basophils by passive IgE sensitisation in allergic rhinitis and anaphylactic Hymenoptera venom hypersensitivity. Methods: We studied 15 wasp venom-, 19 grass pollen- and 2 house dust mite-allergic patients, 2 healthy donors, and 8 wasp venom-allergic donors. In all subjects, we first evaluated the initial basophil response to wasp venom, grass pollen, or house dust mite allergen. Donor basophils were then stripped, sensitised with the different patients' serum IgE, and challenged with the corresponding allergen. The CD63 response of donor basophils was then compared with initial basophil responses. Results: In wasp venom-allergic subjects, the IgE transfer did not reflect the initial basophil-allergen sensitivity, because the venom IgE of subjects with high or low basophil sensitivity induced comparable responsiveness in healthy donor basophils. Furthermore, vice versa, when we sensitised the donor basophils of wasp venom-allergic individuals with different wasp venom or house dust mite IgE, we demonstrated that their response was predictable by their initial basophil allergen sensitivity. In the rhinitis allergy model, the IgE transfer correlated with the patients' initial basophil responsiveness because the grass pollen IgE of the subjects with high basophil allergen sensitivity induced significantly higher responsiveness of donor basophils than the IgE of subjects with initially low basophil allergen sensitivity. Conclusions: Our results suggest that basophil allergen sensitivity evaluated by flow-cytometric CD63 analysis depends on two distinct contribution factors. In anaphylactic Hymenoptera allergy, the major factor was intrinsic cellular sensitivity, whereas in pollen allergy, the major factor was allergen-specific IgE on the cell surface.

Basophil CD63 expression in chronic spontaneous urticaria: correlation with allergic sensitization, serum autoreactivity and basophil reactivity.

The underlying causes and factors contributing to the disease severity of chronic spontaneous urticaria (CSU) are unknown. Given the important role of basophils in the pathogenesis of urticaria and that CD63 serves as a useful marker for basophil activation and detecting, CD63 expression of basophils is a reliable tool for diagnosing allergy and hypersensitivity reactions to different allergens; the objective of this study was to investigate whether the level of basophil CD63 expression is correlated with allergen sensitization, serum autoreactivity and basophil reactivity in patients with CSU. Basophil-enriched leucocytes were separated from the blood of 64 patients with chronic urticaria (54 CSU patients and 10 symptomatic dermographism patients), 18 healthy control subjects and seven atopic donors without urticaria. Flow cytometry was then used to detect CD63 expression on the cell membrane of basophils from all samples. Analysis was also preformed on basophils incubated with sera from CSU patients with positive or negative autologous serum skin test (ASST). CD63 expression was significantly higher in the basophils from patients with CSU than in those from patients with symptomatic dermographism and the healthy control group. The levels of CD63 expression in CSU patients with ASST+ and/or allergen sensitization were higher than those with ASST- and/or no allergen sensitization patients. Incubation with ASST+ serum resulted in an increased expression of CD63 in the basophils of ASST+ CSU patients, whereas no such response was observed in healthy controls or ASST- CSU patients. The increased CD63 expression in basophils from CSU patients may correlate with allergen sensitization, autoreactivity of serum and basophil reactivity. Our results suggest that CD63 may contribute new insight into the pathogenesis of CSU.

Mass cytometry profiling the response of basophils and the complete peripheral blood compartment to peanut

Mass cytometry profiling the response of basophils and the complete peripheral blood compartment to peanut

The IgE and basophil responses to Ara h 2 and Ara h 6 are good predictors of peanut allergy in children

The IgE and basophil responses to Ara h 2 and Ara h 6 are good predictors of peanut allergy in children

Effect of rapid desensitization on platelet inhibition and basophil activation in patients with aspirin hypersensitivity and coronary disease

To determine antiplatelet efficacy after desensitization in patients with a history of aspirin hypersensitivity. We conducted a case-control study to evaluate the efficacy of aspirin 1 day (D1) and 6-8 weeks (W6-8) after desensitization. We also assessed ex vivo basophil reactivity to aspirin after desensitization. Cases were patients with coronary artery disease (CAD) and documented history of aspirin hypersensitivity who underwent rapid successful oral desensitization to aspirin. Controls were patients with stable CAD without hypersensitivity and receiving aspirin. Among 56 cases, 27 received aspirin for acute coronary syndromes and 29 were treated for stable CAD. Aspirin was effective (defined as light transmission aggregometry induced by arachidonic acid ≤20%) at D1 in 86% of cases (P = 0.045 vs. controls) and in 95% at W6-8, vs. 100% of controls (P = 0.39). Urinary excretion of thromboxane B2 diminished substantially in cases (P < 0.0001, D0 vs. W6-8) but remained higher than in controls (P = 0.03). Platelet reactivity (defined by platelet P-selectin expression, activated glycoprotein IIb/IIIa inhibitors, and platelet-monocyte aggregates) was similar in cases between D0 and D1 but decreased at W6-8. Basophil activation (quantified by upregulation of CD203c in response to aspirin) was higher in cases at W6-8 than in controls (P = 0.0002). Thus, following rapid desensitization, aspirin achieves rapid biological efficacy, which is slightly lower at D1, but becomes indistinguishable from chronically treated patients at W6-8. Persistent basophil activation several weeks after desensitization suggests infraclinical hypersensitivity and the need to continue aspirin to maintain desensitization.

Basophil Reactivity as Biomarker in Immediate Drug Hypersensitivity Reactions-Potential and Limitations.

Immediate drug hypersensitivity reactions (DHRs) resemble typical immunoglobulin E (IgE)-mediated symptoms. Clinical manifestations range from local skin reactions, gastrointestinal and/or respiratory symptoms to severe systemic involvement with potential fatal outcome. Depending on the substance group of the eliciting drug the correct diagnosis is a major challenge. Skin testing and in vitro diagnostics are often unreliable and not reproducible. The involvement of drug-specific IgE is questionable in many cases. The culprit substance (parent drug or metabolite) and potential cross-reacting compounds are difficult to identify, patient history and drug provocation testing often remain the only means for diagnosis. Hence, several groups proposed basophil activation test (BAT) for the diagnosis of immediate DHRs as basophils are well-known effector cells in allergic reactions. However, the usefulness of BAT in immediate DHRs is highly variable and dependent on the drug itself plus its capacity to spontaneously conjugate to serum proteins. Stimulation with pure solutions of the parent drug or metabolites thereof vs. drug-protein conjugates may influence sensitivity and specificity of the test. We thus, reviewed the available literature about the use of BAT for diagnosing immediate DHRs against drug classes such as antibiotics, radio contrast media, neuromuscular blocking agents, non-steroidal anti-inflammatory drugs, and biologicals. Influencing factors like the selection of stimulants or of the identification and activation markers, the stimulation protocol, gating strategies, and cut-off definition are addressed in this overview on BAT performance. The overall aim is to evaluate the suitability of BAT as biomarker for the diagnosis of immediate drug-induced hypersensitivity reactions.

Basophil activation testing in diagnosis and monitoring of allergic disease – an overview

The nature of basophil activation as an ex vivo challenge makes it a multifaceted and promising tool for the allergist. Through the development of flow cytometry, discovery of activation markers such as CD63 and markers identifying basophil granulocytes, the basophil activation test (BAT) has become a pervasive test. BAT measures basophil response to allergen crosslinking IgE on between 150 and 2,000 basophil granulocytes with remarkable analytical sensitivity in < 0.1 ml fresh blood. Dichotomous activation is assessed as the fraction of reacting basophils. In patients with food-, insect venom-, and drug allergy and patients with chronic urticaria BAT can be part of the diagnostic evaluation in addition to history, skin prick testing, and specific IgE determination. BAT may also be helpful in determining the clinically relevant allergen. Basophil sensitivity may be used to monitor patients on allergen immunotherapy, anti-IgE treatment, or in the natural resolution of allergy. The test may use fewer resources and be more reproducible than oral, sting, nasal or bronchial challenge testing. BAT may be useful before challenge testing as it is less stressful for the patient and avoids severe allergic reactions. It may be useful before challenge testing. An important next step is to standardize BAT and make it available in diagnostic laboratories. This article provides an overview of the practical and technical details as well as the utility of BAT in diagnosis and management of allergic diseases.

Basophil activation testing in diagnosis and monitoring of allergic disease – an overview

The nature of basophil activation as an ex vivo challenge makes it a multifaceted and promising tool for the allergist. Through the development of flow cytometry, discovery of activation markers such as CD63 and markers identifying basophil granulocytes, the basophil activation test (BAT) has become a pervasive test. BAT measures basophil response to allergen crosslinking IgE on between 150 and 2,000 basophil granulocytes with remarkable analytical sensitivity in < 0.1 ml fresh blood. Dichotomous activation is assessed as the fraction of reacting basophils. In patients with food-, insect venom-, and drug allergy and patients with chronic urticaria BAT can be part of the diagnostic evaluation in addition to history, skin prick testing, and specific IgE determination. BAT may also be helpful in determining the clinically relevant allergen. Basophil sensitivity may be used to monitor patients on allergen immunotherapy, anti-IgE treatment, or in the natural resolution of allergy. The test may use fewer resources and be more reproducible than oral, sting, nasal or bronchial challenge testing. BAT may be useful before challenge testing as it is less stressful for the patient and avoids severe allergic reactions. It may be useful before challenge testing. An important next step is to standardize BAT and make it available in diagnostic laboratories. This article provides an overview of the practical and technical details as well as the utility of BAT in diagnosis and management of allergic diseases.

Increasing time interval and decreasing allergen dose interval improves ex vivo desensitization of human blood basophils.

Desensitization is a method for inducing temporary tolerance to allergen. The mechanism underlying desensitization is yet to be established. Basophil granulocytes in whole blood from grass pollen allergic subjects were desensitized ex vivo by sequential addition of increasing allergen concentrations. At each step basophil activation (CD193 + CD63+ ) was monitored with and without (background activation) allergen challenge at optimal concentration. The sequential desensitization protocol was compared to two single-dose desensitization protocols with threshold and subthreshold allergen concentrations. Incubation intervals and allergen concentrations were varied in order to optimise the protocol. Sequential desensitization effectively reduced basophil response. The single-dose subthreshold protocol and single-dose threshold protocol did not reduce basophil activation with optimal allergen challenge from a mean 57.1 (95% CI: 32.7 - 81.5) to 50.4% (95% CI: 16.3 - 84.4; n = 5; P = 0.43) and 45.0% (95% CI: 23.1 - 66.9; P = 0.14) respectively, while the sequential desensitization protocol reduced activation to a mean 37.2% (95% CI: 16.3 - 58.1; P = 0.018). Reducing incubation time from 10 to 5 minutes increased mean background activation from 22.4 (95% CI: 11.7 - 33.1) to 30.0% (95% CI: 19.7 - 40.3; n = 5; P = 0.026). Increasing time intervals from 10 to 20 minutes reduced background activation from 30.9 (95% CI: 22.8 - 39.0) to 21.9% (95% CI: 16.0 - 27.7; n = 5; P = 0.020). Increasing allergen concentration intervals from 2-fold to 5- and 10-fold did not have significant effect on basophil activation. Sequential desensitization ex vivo effectively attenuates the basophil response to allergen. Increasing the time spent at each step improves desensitization. This protocol could be valuable for investigation the mechanism of desensitization. © 2016 International Clinical Cytometry Society.

Transcriptional regulation of basophil development and function in Th2 immunity

Abstract Basophils are the most rare granulocyte population, accounting for less than 1% of circulating leukocytes in mice and human. Recent studies have shown that basophils are associated with multiple immunological processes, such as allergic diseases, autoimmunity, and protective immunity against parasites. It has been show that the rapid secretion of Th2 cytokines by basophils in response to various stimuli plays key roles in immunity against parasitic infections. Basophils also release histamine and, therefore, are key contributors to allergy. In addition, basophil responses are associated with multiple human diseases such as asthma, atopic dermatitis and cancer. Given their important roles in inflammatory signaling and human diseases, remarkably little is known about the molecular regulation of basophil effector functions. Therefore, we have been exploring transcription factors that may play a direct role in controlling basophil development and effector functions. In this study, we have developed multiple in vitro and in vivo systems to study the influence of the loss of a potentially key transcription factor on the basophil response to allergen-induced Th2 immunity. We are in the process of performing gene expression arrays to understand the molecular mechanisms underlying the transcriptional regulation. Collectively, our studies provide new insight into the transcriptional network controlling basophil effector functions in Th2 immune response and lead to potential therapies that modulate basophil activities during the treatment of allergic diseases.

Transcriptional profiling of mast cell and basophil responses to differential stimuli identifies unique gene signatures.

Abstract Mast cells (MC) and basophils (BΦ) are key effector cells in allergy that are developmentally related. Functionally, they both release mediators like histamine and granule proteases. However, studies also suggest that MC and BΦ have non-redundant roles in allergic diseases. Their ability to respond to IL-33—an epithelium-derived cytokine that helps initiate allergic inflammation—is not well understood. To fully characterize the transcriptional responses and heterogeneity of MC and BΦ, we performed large-scale comparative microarrays of bone marrow-derived mast cells (BMMCs) and basophils (BMBs) either at rest, upon IgE activation, or upon IL-33 activation. Hierarchical clustering demonstrated that BMMCs had activation-specific transcriptional signatures. IgE-crosslinking upregulated 1803 unique genes including Ccl7, Fxyd6, and Cd33; while IL-33 stimulation induced 1918 genes including Il1b, Cd72, and Tnfaip2. Focused bioinformatics pathway analysis demonstrated IgE-activation aligned with pathways relating to complement activation and CD137 signaling, while IL-33 initiated responses in the NF-κB and IL-10 signaling pathways. Furthermore, BMBs activated via IgE-crosslinking induced type 2 immune response genes like Il2, Il4, Ccl17 and Il13 which were surprisingly absent in IL-33 stimulated BMBs. Further analysis revealed cell-specific transcriptional signatures with 4360 genes that were significant in BMBs but not in BMMCs after IgE activation, and 1645 after IL-33 stimulation. Here we show that MC and BΦ have cell-specific and activation-specific transcriptional responses, and our data suggest novel gene networks and pathways that may shape how the immune system responds to allergens and innate cytokines.

Inhibition of IgE-Mediated Allergic Reaction By Pharmacologically Targeting the Circadian Clock

Recently, we reported that the circadian clock temporally gates signaling via the high-affinity IgE receptor (FcepsilonRI) in mast cells, thereby generating a marked day–night variation in allergic reactions (JACI, 2014). We therefore hypothesized that pharmacologically resetting the molecular clock in mast cells to times when FcepsilonRI signaling is reduced (i.e., when core circadian protein PERIOD2 [PER2] is up-regulated) might inhibit IgE-mediated allergic reactions. In this study, we determined whether pharmacologically resetting the molecular clock in mast cells or basophils to times when FcepsilonRI signaling was reduced (i.e. when PER2 is up-regulated) resulted in suppression of IgE-mediated allergic reactions. We examined the effects of PF670462, a selective inhibitor of the key clock component casein kinase (CK)1delta/epsilon which up-regulated PER2 in mast cells, on IgE-mediated allergic reactions both in vitro and in vivo. PF670462 suppressed IgE-mediated allergic reactions in mouse bone marrow-derived mast cells or basophils, and the passive cutaneous anaphylactic (PCA) reaction in mice, in association with increased PER2 levels in mast cells or basophils. PF670462 ameliorated allergic symptoms in a mouse model of allergic rhinitis and down-regulated allergen-specific basophil reactivity in patients with allergic rhinitis. Pharmacologically resetting the molecular clock in mast cells or basophils to times when FcepsilonRI signaling is reduced can inhibit IgE-mediated allergic reactions. The results suggest a new strategy for controlling IgE-mediated allergic diseases.

Early Peanut OIT-Induced Suppression of Basophil Reactivity Is a Marker of Sustained Unresponsiveness

Early Peanut OIT-Induced Suppression of Basophil Reactivity Is a Marker of Sustained Unresponsiveness

Short-, Intermediate-, and Long-Term Changes in Basophil Reactivity Induced by Venom Immunotherapy.

PurposeThe basophil activation test (BAT) has been used to monitor venom immunotherapy (VIT) due to its high specificity. A previous study has reported a good correlation between a significant decrease in basophil activation during 5 years of VIT and clinical protection assessed by sting challenge. The following prospective study was performed to examine changes in basophil reactivity over a complete VIT period of 5 years.MethodsBAT in a dose-response curve was studied prospectively in 10 hymenoptera venom-allergic patients over 5 years of VIT. BAT was performed at the time of diagnosis, 1 month after finishing the VIT build-up phase, and 3, 6, 12, 24, and 60 months after beginning treatment. The repeated measures ANOVA was applied to evaluate basophil activation changes throughout VIT. A cross-sectional study was also performed in 6 patients who received treatment for more than 3 years, and in another 12 patients who followed immunotherapy for at least 5 years.ResultsAn early activation decrease was observed during the first 3 months of treatment, compared to pre-treatment values. This activation decrease was not maintained 6 to 18 months after treatment, but was observed again after 2 years of treatment, and maintained until the completion of the 5-year immunotherapy period. In cross-sectional analysis, the 6 patients who received treatment for 3 years, and 9 of the 12 patients who received treatment for 5 years, had negative BAT results. Three patients in this last group had positive BAT results and 2 patients had systemic reactions after field stings.ConclusionsBAT appears to be an optimal non-invasive test for close monitoring of VIT.

Clinical and laboratory 2-year outcome of oral immunotherapy in patients with cow's milk allergy.

Studies examining the long-term effect of oral immunotherapy in food-allergic patients are limited. We investigated cow's milk-allergic patients, >6 months after the completion of oral immunotherapy (n = 197). Questionnaires, skin prick tests, and basophil activation assays were performed. Of the 195 patients contacted, 180 (92.3%) were consuming milk protein regularly. Half experienced adverse reactions, mostly mild. Thirteen patients (6.7%) required injectable epinephrine. Higher reaction rate after immunotherapy was associated with more anaphylactic episodes before treatment and a lower starting dose (OR = 2.1, P = 0.035 and OR = 2.3, P = 0.035, respectively). Reaction rate in patients who were 6-15 months, 15-30 months, or >30 months post-treatment decreased from 0.28/month to 0.21/month to 0.15/month, respectively (P < 0.01). Milk-induced %CD63 and %CD203c expression was significantly lower in patients >24 months vs in patients <24 months post-treatment (P = 0.038 and P = 0.047, respectively). In conclusion, many patients experience mild adverse reactions after completing oral immunotherapy and some require injectable epinephrine. Progressive desensitization, both clinically and in basophil reactivity, occurs over time.

Pimecrolimus Is a Potent Inhibitor of Allergic Reactions to Hymenopteran Venom Extracts and Birch Pollen Allergen In Vitro.

Pimecrolimus (Elidel, SDZ ASM 981) is an anti-inflammatory and immunomodulatory 33-epichloro-derivative of macrolactam ascomycin, with low potential for affecting systemic immune responses compared with other calcineurin inhibitors, cyclosporin A and tacrolimus. Despite numerous studies focused on the mechanism of pimecrolimus action on mast cells, only the single report has addressed pimecrolimus effects on other typical FcεRI-expressing cells, the basophils. Patients allergic to birch pollen (n = 20), hymenopteran venoms (n = 23) and 10 non-allergic volunteers were examined. Primary human basophils pre-treated or not with 0.5–50 μMol pimecrolimus were exposed to various concentrations of recombinant Bet v 1a allergen, bee or wasp venom extracts and anti-IgE for 20 min, and then examined for the expression of CD45, CD193, CD203c, CD63 and CD164 using flow cytometry. The externalization of basophil activation markers (CD63 and CD164) was equally inhibited through pimecrolimus in cells activated by recombinant pollen allergen, hymenopteran venom extracts and anti-IgE. Although the individual response rate was subject to strong variation, importantly, pre-treatment with pimecrolimus lowered the number of activated basophils in response to any of the stimuli in the basophils from all patients. The inhibition was concentration-dependent; approximately half of the basophils were inhibited in the presence of 2.5 mMol pimecrolimus. Pimecrolimus is a valuable new tool for the inhibition of hyper-reactive basophils in patients with pollen allergy and a history of anaphylactic reactions to bee or wasp venoms. Further research should address short-term use of pimecrolimus in vivo in a wide spectrum of allergic diseases.

Inhibition of IgE-mediated allergic reactions by pharmacologically targeting the circadian clock

The circadian clock temporally gates signaling through the high-affinity IgE receptor (FcεRI) in mast cells, thereby generating a marked day/night variation in allergic reactions. Thus manipulation of the molecular clock in mast cells might have therapeutic potential for IgE-mediated allergic reactions. We determined whether pharmacologically resetting the molecular clock in mast cells or basophils to times when FcεRI signaling was reduced (ie, when core circadian protein period 2 [PER2] is upregulated) resulted in suppression of IgE-mediated allergic reactions. We examined the effects of PF670462, a selective inhibitor of the key clock component casein kinase 1δ/ε, or glucocorticoid, both of which upregulated PER2 in mast cells, on IgE-mediated allergic reactions both in vitro and in vivo. PF670462 or corticosterone (or dexamethasone) suppressed IgE-mediated allergic reactions in mouse bone marrow-derived mast cells or basophils and passive cutaneous anaphylactic reactions in mice in association with increased PER2 levels in mast cells or basophils. PF670462 or dexamethasone also ameliorated allergic symptoms in a mouse model of allergic rhinitis and downregulated allergen-specific basophil reactivity in patients with allergic rhinitis. Pharmacologically resetting the molecular clock in mast cells or basophils to times when FcεRI signaling is reduced can inhibit IgE-mediated allergic reactions. The results suggest a new strategy for controlling IgE-mediated allergic diseases. Additionally, this study suggests a novel mechanism underlying the antiallergic actions of glucocorticoids that relies on the circadian clock, which might provide a novel insight into the pharmacology of this drug in allergic patients.

Assessing the efficacy of oral immunotherapy for the desensitisation of peanut allergy in children (STOP II): a phase 2 randomised controlled trial: a critical appraisal.

Anagnostou etal. investigated the efficacy of oral immunotherapy (OIT) in treating peanut allergy. An unmasked randomized controlled crossover trial of 7-16year olds with double-blind placebo-controlled food challenge (DBPCFC)-proven peanut allergy. The first phase compared an active group undergoing 26weeks of OIT with daily ingestion of peanut protein vs. a control group avoiding peanuts. Both groups underwent DBPCFC to peanut at 26weeks. In the second phase the control group was then offered OIT for 26weeks. Participants undergoing OIT attended hospital every 2weeks to initiate and increase their daily peanut protein dose through nine stages (2, 5, 12·5, 25, 50, 100, 200, 400 and 800mg - about five peanuts), subsequently maintaining consumption at the highest tolerated dose. Primary outcome The primary outcome compared the proportions of active- and control-group participants able to ingest a cumulative dose of 1400mg of peanut protein (about 10 peanuts) during their DBPCFC at the end of the first phase without reacting. Secondary outcomes Further outcomes included the proportion of participants who tolerated the top maintenance dosage of 800mg protein up to 26weeks; the proportion of the control group who were desensitized or tolerated daily ingestion of 800mg protein in the second phase; threshold changes in no observed adverse effect level after OIT (NOAEL: defined as the highest dose of peanut protein tolerated in milligrams of protein during challenge or immunotherapy); change in quality of life; number and type of adverse events; and immunological parameters (basophil reactivity, peanut-specific IgE, total IgE and skin-prick test). Primary outcome Twenty-four of 39 (62%) of the active group were able to tolerate the 1400mg of peanut protein during their DBPCFC after 26weeks of OIT, compared with none of the 46 control participants (P<0·001). Secondary outcomes Twenty-five of 46 (54%) of the control group had a negative 1400-mg peanut protein challenge at the end of phase 2. Combining the two groups, 49 of85 children (58%) were desensitized. Thirty-three of 39 (85%) active participants in phase one and 42 of 46 (91%) control participants in phase two tolerated 800mg of OIT daily - a combined result of 75 of 85 (88%) trial participants. The median absolute change in NOAEL between baseline and 26weeks was 1345mg (P=0·002), or a 25·5-fold increase (P<0·001) for the active group. Both the active and control groups demonstrated a significant improvement (decrease) in Food Allergy Quality of Life scores after OIT in the under-13-year-old participants: -1·61 and -1·41, respectively (both P<0·001). Mild side-effects predominated, with 54 (57%) reporting abdominal pain and 31 (33%) reporting vomiting. However, 21 (22%) also reported wheezing and one (1%) laryngeal oedema. One participant received adrenaline by self-administration on two occasions for wheezing. Anagnostou etal. concluded that OIT successfully induced desensitization in challenge-proven peanut-allergic children and resulted in a clinically and socially meaningful increase in tolerated peanut protein. Quality of life improved after intervention and there was a good safety profile.

The clinical utility of basophil activation testing in diagnosis and monitoring of allergic disease.

The basophil activation test (BAT) has become a pervasive test for allergic response through the development of flow cytometry, discovery of activation markers such as CD63 and unique markers identifying basophil granulocytes. Basophil activation test measures basophil response to allergen cross-linking IgE on between 150 and 2000 basophil granulocytes in <0.1 ml fresh blood. Dichotomous activation is assessed as the fraction of reacting basophils. In addition to clinical history, skin prick test, and specific IgE determination, BAT can be a part of the diagnostic evaluation of patients with food-, insect venom-, and drug allergy and chronic urticaria. It may be helpful in determining the clinically relevant allergen. Basophil sensitivity may be used to monitor patients on allergen immunotherapy, anti-IgE treatment or in the natural resolution of allergy. Basophil activation test may use fewer resources and be more reproducible than challenge testing. As it is less stressful for the patient and avoids severe allergic reactions, BAT ought to precede challenge testing. An important next step is to standardize BAT and make it available in diagnostic laboratories. The nature of basophil activation as an ex vivo challenge makes it a multifaceted and promising tool for the allergist. In this EAACI task force position paper, we provide an overview of the practical and technical details as well as the clinical utility of BAT in diagnosis and management of allergic diseases.