In vitro diagnosis of cypress pollen allergy by using cytofluorimetric analysis of basophils (Basotest)

Prueba de activación de basófilos: aspectos técnicos, metodológicos y su utilidad clínica

Introducción. La prueba de activación de basófilos (PAB) se considera una técnica confiable y segura para el diagnóstico de problemas alérgicos.Objetivo. Profundizar en el estado del arte de la PAB y su utilidad clínica.Materiales y métodos. Se realizó una revisión narrativa de la literatura mediante la búsqueda electrónica en las bases de datos y metabuscadores Ovid Medline, Google Scholar y PubMed, sin limitar la búsqueda por fecha, idioma o tipo de artículo. Se buscaron artículos sobre los detalles técnicos de la PAB y su utilidad clínica en el manejo de las enfermedades alérgicas.Resultados. De los marcadores de activación, CD63 ha sido el más estudiado y es el que mejor representa un evento de degranulación anafiláctica, mientras que CD203c es representativo de varias formas de degranulación. La superioridad de uno sobre otro como prueba diagnóstica depende del problema alérgico estudiado. En cuanto a los métodos de detección de basófilos, su selección con un único marcador, CCR3, se propone como una opción con buena relación de costo-efectividad.Conclusiones. La PAB es una herramienta prometedora para evaluar en clínica las reacciones alérgicas de forma segura. Es necesario una mayor estandarización de protocolos para obtener resultados más reproducibles.

Tools to investigate and avoid drug-hypersensitivity in drug development

INTRODUCTION

Drug hypersensitivity reactions (DHRs) are common adverse effects of pharmaceuticals that clinically resemble allergies, and which are becoming an important burden to healthcare systems. Alongside accurate diagnostic techniques, tools which can predict potential drug-inducing hypersensitivity reactions in the pre-clinical phase are critical. Despite the important adverse reactions linked to immune-mediated hypersensitivity, at present, there are no validated or required in vivo or in vitro methods to screen the sensitizing potential of drugs and their metabolites in the pre-clinical phase. Areas covered: Enhanced prediction in preclinical safety evaluation is extremely important. The purpose of this review is to assess the state of the art of tools available to assess the allergenic potential of drugs and to highlight our current understanding of the molecular mechanisms underlying inappropriate immune activation. Expert opinion: The knowledge that allergenic drugs share common mechanisms of immune cell activation with chemical allergens, and of the definition of the mechanistic pathway to adverse outcomes, can enhance targeting toxicity testing in drug development and hazard assessment of hypersensitivity. Additional efforts and extensive resources are necessary to improve preclinical testing methodologies, including optimization, better design and interpretation of data.

Basophil activation test for inhalant allergens in pediatric patients with allergic rhinitis

OBJECTIVE

Flow cytometric quantification of in vitro basophil activation can be quite performant and reliable tool to measure IgE-dependent allergen-specific responses in allergic patients. Current study aimed to evaluate the clinical relevance of basophil activation test (BAT) for the diagnosis of pediatric grass pollen and house dust mite (HDM) allergies.

METHODS

Forty-seven patients suffering from allergic rhinitis with HDM and grass pollen co-sensitization with clinical history of allergic rhinitis and/or asthma and 15 non-allergic healthy subjects were enrolled. BAT was determined by flow cytometry upon double staining with anti-IgE/anti-CD63 mAb.

RESULTS

Regarding HDM with cut-off point greater than 12.5% for CD63⁺ basophils sensitivity and specificity of the BAT were 90% and 73%, with positive predictive value (PPV) and negative predictive value (NPV) as 0.70 and 0.91, respectively. The analysis of concordance of being either allergic or healthy in comparison to BAT results for HDM revealed a substantial concordance (κ index = 0.61, p < 0.001). Grass pollen with cut-off point greater than 11%, BAT attained a sensitivity, specificity, PPV, and NPV of 96%, 93%, 0.98, and 0.88, respectively. The analysis of concordance of being either allergic or healthy in comparison to BAT results for grass pollen revealed an almost perfect concordance (κ index = 0.87, p < 0.001).

CONCLUSION

Our findings concluded that BAT is reliable technique in the diagnosis of sensitization to grass pollen and HDM. The sensitivity of BAT in pollen allergic children was found to be remarkably higher in our cohort compared to other studies.

In vitro Models to Evaluate Drug-Induced Hypersensitivity: Potential Test Based on Activation of Dendritic Cells

Hypersensitivity drug reactions (HDRs) are the adverse effect of pharmaceuticals that clinically resemble allergy. HDRs account for approximately 1/6 of drug-induced adverse effects, and include immune-mediated ("allergic") and non-immune-mediated ("pseudo allergic") reactions. In recent years, the severe and unpredicted drug adverse events clearly indicate that the immune system can be a critical target of drugs. Enhanced prediction in preclinical safety evaluation is, therefore, crucial. Nowadays, there are no validated in vitro or in vivo methods to screen the sensitizing potential of drugs in the pre-clinical phase. The problem of non-predictability of immunologically-based hypersensitivity reactions is related to the lack of appropriate experimental models rather than to the lack of -understanding of the adverse phenomenon. We recently established experimental conditions and markers to correctly identify drug associated with in vivo hypersensitivity reactions using THP-1 cells and IL-8 production, CD86 and CD54 expression. The proposed in vitro method benefits from a rationalistic approach with the idea that allergenic drugs share with chemical allergens common mechanisms of cell activation. This assay can be easily incorporated into drug development for hazard identification of drugs, which may have the potential to cause in vivo hypersensitivity reactions. The purpose of this review is to assess the state of the art of in vitro models to assess the allergenic potential of drugs based on the activation of dendritic cells.

Are allergic multimorbidities and IgE polysensitization associated with the persistence or re-occurrence of foetal type 2 signalling? The MeDALL hypothesis

Allergic diseases [asthma, rhinitis and atopic dermatitis (AD)] are complex. They are associated with allergen-specific IgE and nonallergic mechanisms that may coexist in the same patient. In addition, these diseases tend to cluster and patients present concomitant or consecutive diseases (multimorbidity). IgE sensitization should be considered as a quantitative trait. Important clinical and immunological differences exist between mono- and polysensitized subjects. Multimorbidities of allergic diseases share common causal mechanisms that are only partly IgE-mediated. Persistence of allergic diseases over time is associated with multimorbidity and/or IgE polysensitization. The importance of the family history of allergy may decrease with age. This review puts forward the hypothesis that allergic multimorbidities and IgE polysensitization are associated and related to the persistence or re-occurrence of foetal type 2 signalling. Asthma, rhinitis and AD are manifestations of a common systemic immune imbalance (mesodermal origin) with specific patterns of remodelling (ectodermal or endodermal origin). This study proposes a new classification of IgE-mediated allergic diseases that allows the definition of novel phenotypes to (i) better understand genetic and epigenetic mechanisms, (ii) better stratify allergic preschool children for prognosis and (iii) propose novel strategies of treatment and prevention.

Japanese cedar pollen-based subcutaneous immunotherapy decreases tomato fruit-specific basophil activation

BACKGROUND

Some patients with Japanese cedar pollen (JCP)-induced allergic rhinitis develop pollen-food allergy syndrome (PFAS) as a reaction to tomato fruit. Pollen allergen-specific subcutaneous immunotherapy (SCIT) is reportedly beneficial for some associated food allergies; however, the reported changes in food allergen-specific immunoglobulin (Ig)E and IgG4 levels are inconsistent. Here, we investigated immunologic reactivity to tomato fruit after JCP-based SCIT.

METHODS

Twenty-three children (aged 6-17 years) with JCP-induced allergic rhinitis and sensitized to tomato (serum tomato fruit-specific IgE level >0.34 UA/ml) received JCP-based SCIT. Basophil activation by tomato and JCP extracts and serum-specific IgE and IgG4 levels against these allergens were determined before and after 4 or 5 months of maintenance SCIT. Basophil activation was assessed by monitoring CD203c upregulation on flow cytometry.

RESULTS

JCP-based SCIT significantly reduced the basophil activation caused by tomato fruit (p = 0.03) and JCP (p < 0.001) extracts. JCP-specific IgG4 levels markedly increased after SCIT (p < 0.001), whereas tomato fruit-specific IgG4 levels did not. After SCIT, no significant changes were observed in specific IgE levels for tomato fruit (p = 0.11) or JCP (p = 0.19).

CONCLUSIONS

Tomato fruit-specific basophil activation decreases after JCP-based SCIT, suggesting that it is efficacious in relieving and preventing the symptoms of PFAS in patients with JCP-induced allergic rhinitis.

Determination of sIgE to rPhl p 1 is sufficient to diagnose grass pollen allergy

BACKGROUND

New diagnostic tools such as the basophil activation test (BAT) and component-resolved diagnosis (CRD) are promising for Hymenoptera venom or food allergy. A clear benefit for inhalant allergens has not yet been shown. Our aim was to compare new and established tests for grass pollen allergy.

METHODS

Forty-nine patients with grass pollen allergy and 47 controls were prospectively enrolled in the study. A symptom score was calculated for each patient. Conjunctival provocation tests (CPT), skin prick tests (SPT), BAT, and sIgE determination including CRD were performed. Sensitivity and specificity were compared and results were correlated with the symptom score.

RESULTS

Single determination of sIgE to rPhl p 1 showed the best balance between sensitivity (98%) and specificity (92%). Use of additional components, such as rPhl p 2 and 5, did not increase sensitivity. Generally, sensitivity of tests was high: SPT 100%, ISAC-112 100%, sIgE to timothy grass 98%, BAT 98%, ISAC-103 84%, and CPT 83%. Specificity ranged from 79% (SPT) to 96% (CPT). All test results and calculated values (e.g. ratio sIgE/tIgE) did not correlate with symptom severity. Asymptomatic sensitization to timothy grass in controls was rare in the CAP (11%) and predominantly due to Phl p 1 sensitization.

CONCLUSION

rPhl p 1 was sufficient to diagnose grass pollen allergy, and sIgE patterns were the same in symptomatically and asymptomatically sensitized subjects. The testing of multiple components was of minor importance, and no test correlated with symptom severity.

Detection of Allergen-Specific IgE Antibody Responses

Allergen-specific IgE production is the central event in the pathogenesis of atopic disorders and increases in specific IgE serum antibodies are an indicator of immediate hypersensitivity responses in humans and in animal models of allergy. Consequently, accurate and user-friendly methods are needed to measure serum levels of allergen-specific IgE. This review examines historical and recent developments in in vivo and in vitro methods for the detection of allergen-specific IgE in humans and in animal models. Routinely, in vitro methods such as enzyme-linked immunosorbant assays or radioallergosorbant tests and in vivo methods such as the skin prick test (SPT) for humans and the passive cutaneous anaphylaxis assay (PCA) used in animals are utilized to detect allergen-specific IgE. While in vivo assays are usually more accurate than in vitro assays since they provide a functional readout of IgE activity, they are relatively costly and require considerable expertise. On the other hand in vitro assays are limited by the fact that the amount of allergen-specific serum IgG exceeds IgE antibody by several orders of magnitude, resulting in competition for allergen binding. Consequently, methods that use allergen as a direct capture step are limited by the availability of free allergen binding sites for IgE. In order to circumvent this problem, in vitro methods usually require prior depletion of IgG or use high amounts of allergen in order to facilitate availability of free binding sites for IgE detection. Clearly, these approaches are limited for small sample volumes and allergens that are in short supply. New methods such as protein microarray could potentially overcome this problem by providing high allergen concentrations in a relatively small reaction volume. Currently, in vitro methods are rarely used in isolation for prognosis but are used primarily to complement the information obtained from in vivo assays. With the emergence of new technologies it is conceivable that in vitro assays may in the future replace in vivo assays, however until then in vivo assays remain the gold standard of allergen-specific IgE detection.

Reliability of basophil activation test using CD203c expression in diagnosis of pollen allergy

BACKGROUND

CD203c is a basophil surface marker and its expression is rapidly up-regulated after cross-linking of high-affinity immunoglobulin E (IgE) receptor (FcepsilonR1) by an allergen. CD203c basophil activation tests have been studied for the in vitro diagnosis of several allergic conditions. However, there is limited data about its diagnostic usefulness. The optimum allergen concentrations for stimulation and allergen specific cutoff values remain unknown for a number of allergens. This study was designed to investigate the efficacy of basophil activation test via CD203c in the diagnosis of pollen allergy.

METHODS

The CD203c basophil activation was determined in 31 allergic rhinitis patients with pollen allergy and 9 healthy nonatopic controls during the off-season. CD203c expression was evaluated using three-color staining protocol by flow cytometry.

RESULTS

After an in vitro stimulation with grass pollen extract, the CD203c assay clearly discriminated pollen-allergic patients from controls (p < 0.001). A dose-dependent increase in the percentages of CD203c-activated basophils was shown in rhinitis patients with pollen allergy (p < 0.001). The sensitivity and specificity was 100% and optimal cutoff values were 14.05 and 10.05% with 45.1 and 4.5 μg/mL Phl p 5 stimulation, respectively. Although the specificity was also 100%, the sensitivity was 93 and 87% and the cutoff values were 5.40 and 5.35% with 4.5 × 10(-4) and 4.5 × 10(-5) micrograms/mL Phl p 5 stimulation, respectively.

CONCLUSION

The CD203c basophil activation test seems to be a reliable tool in the diagnosis of grass pollen allergy. It could be used when conventional diagnostic tests fail or can not be performed.

Using time-resolved fluorescence to measure serum venom-specific IgE and IgG

We adapted DELFIA™ (dissociation-enhanced lanthanide fluoroimmunoassay), a time resolved fluorescence method, to quantitate whole venom specific and allergenic peptide-specific IgE (sIgE), sIgG₁ and sIgG₄ in serum from people clinically allergic to Australian native ant venoms, of which the predominant cause of allergy is jack jumper ant venom (JJAV). Intra-assay CV was 6.3% and inter-assay CV was 13.7% for JJAV sIgE. DELFIA and Phadia CAP JJAV sIgE results correlated well and had similar sensitivity and specificity for the detection of JJAV sIgE against intradermal skin testing as the gold standard. DELFIA was easily adapted for detecting sIgE to a panel of other native ant venoms.

Validation of basophil CD164 upregulation for pollen allergy diagnosis

The aim of the study was to evaluate the sensitivity and specificity of allergen-induced basophil CD164 upregulation in patients with seasonal allergic rhinitis caused by allergy to grass pollens. This study was performed in 24 patients with allergy to grass pollens, and in 25 healthy controls. The protocol for allergen-induced basophil CD164 upregulation consisted of whole blood samples processing and staining with anti-CCR3/anti-CD164 antibodies added to a buffer at the beginning of stimulation. We observed dose-dependent allergen-induced basophil CD164 upregulation with 100% of specificity in both used allergen concentrations (12 and 1.2 ng/ml). Higher allergen concentration resulted in 100% and lower concentration in only 70.83% sensitivity. We have observed in the patients statistically significant correlations between anti-IgE stimulation and both allergen concentrations (for 12 ng/ml, r = 0.71, p < 0.0001; and for 1.2 ng/ml, r = 0.64, p < 0.001). We conclude that assessment of allergen-induced basophil CD164 upregulation is a very useful method for in vitro determination of allergy to grass pollens. This method seems to be a very promising tool in laboratory testing of allergies to other allergens.

Assessment of allergen sensitization in a general population-based survey (European Community Respiratory Health Survey I)

PURPOSE

Exposed to a common environment, the IgE-mediated immune response differs, for instance, among sensitized subjects, some of them reacting toward one allergen (monosensitized) whereas others are sensitized to a wide array of allergens (polysensitized). However, a better phenotypic characterization is needed for epidemiologic studies. Using the data collected during the ECRHS I (European Community Respiratory Health Survey), several assessments of skin prick tests and serum-specific IgE to identify mono- and polysensitized patients were compared.

METHODS

Subjects took part in the ECRHS-I. The CAP-System was used for serum allergen-specific IgE, and allergen-coated Phazet was used for prick tests. Four allergens (Dermatophagoides pteronyssinus, cat, timothy grass, and Cladosporium) were measured using IgE and nine (the same ones plus olive pollen, birch, Alternaria, Parietaria, and ragweed) were skin tested. One to two local allergens were also tested, depending on countries.

RESULTS

Prevalence of sensitization in 11,355 subjects (34.0 [27.9-40.1] years, 49.9% men) ranged from 32.3% (four specific IgE, 19.3% mono- and 13.0% polysensitized) to 41.8% (four specific IgE combined to nine prick tests, 19.6% mono- and 22.2% polysensitized). Concordance between four specific IgE and four prick tests was weak (weighted κ 0.65 [0.64-0.66]). Concordance between seven and nine prick tests was high (weighted κ 0.99 [0.98-1.00]). Local allergens induced small changes in the prevalence of sensitization, and reclassified some subjects from mono- to polysensitized.

CONCLUSIONS

Skin tests or serum-specific IgE may be chosen to identify allergenic sensitivity, mono- and polysensitized subjects without being strictly interchangeable.

The basophil activation test in the diagnosis of allergy: technical issues and critical factors

BACKGROUND

The basophil activation test (BAT) is a widely validated and reliable tool especially for the diagnosis of hymenoptera venom allergy. Nevertheless, several pitfalls have to be considered and outcomes may differ because of diverse in-house protocols and commercially available kits. We aimed to identify the factors that may influence results of the CD63-based BAT.

METHODS

Basophil responses to monoclonal anti-IgE (clone E124.2.8) and bee and wasp venom were determined by BAT based on CD63. The effect of stimulating factors such as, IL-3, cytochalasin B and prewarming of the samples was investigated. Furthermore, we compared two different flow cytometer systems and evaluated the influence of storage time, different staining protocols and anti-allergic drugs on the test results.

RESULTS

Interleukin-3 enhanced the reactivity of basophils at 300 pM, but not at 75 and 150 pM. Prewarming of samples and reagents did not affect basophil reactivity. CD63 expression assayed after storage time of up to 48 h showed that basophil reactivity already started to decline after 4 h. Basophils stained with HLA-DR-PC5 and CD123-PE antibodies gated as HLA-DR(neg)/CD123(pos) cells showed the highest reactivity. No effect on test outcomes was observed at therapeutic doses of dimetindene and desloratadine. Finally, slight differences in the percentage of activated basophils, depending on the cytometer system used, were found.

CONCLUSION

Basophil activation test should be performed as early as possible after taking the blood sample, preferably within 4 h. In contrast to the skin test, BAT can be performed in patients undergoing treatment with antihistamines. For reasons of multiple influencing factors, BAT should be performed only at validated laboratories.

Allergen-induced basophil CD203c expression as a biomarker for rush immunotherapy in patients with Japanese cedar pollinosis

BACKGROUND

Rush immunotherapy (RIT) can confer rapid clinical benefit on patients with allergic rhinitis or asthma. However, biomarkers representing mechanisms for the efficacy of RIT are still to be established. CD203c is a basophil activation marker known to be upregulated by cross-linking of the FcepsilonRIalpha receptor and may serve as a useful marker.

OBJECTIVE

We sought to investigate the changes in allergen-induced CD203c expression in patients with Japanese cedar pollen (JCP) pollinosis who received RIT.

METHODS

Nine patients treated with RIT were enrolled in the study. Whole blood was incubated with various concentrations of JCP extract. CD203c expression on basophils was quantitated by means of flow cytometry. JCP-specific IgG4 levels in sera were measured with ELISA. Basophil histamine release, CAP-RAST to JCP (JCP-IgE) and total IgE were also examined. The biomarkers listed above were evaluated before and sequentially after RIT. Symptom and quality of life scores were obtained during pre- and posttreatment pollen seasons.

RESULTS

All patients showed significant improvement in symptom and quality of life scores after RIT. Serum JCP-specific IgG4 titers were significantly elevated at 1 month and remained at high levels 12 months after the treatment. Stimulation with JCP extract induced enhancement of basophil CD203c expression in a concentration-dependent manner except for 2 subjects in whom no increase in CD203c by an anti-IgE antibody was observed (nonresponders). Significant reductions in the responses were observed in 4 subjects after RIT (reduction in CD203c expression, RCE) whereas no changes were seen in 3 subjects (non-RCE). RCE subjects were older than non-RCE counterparts, with mean ages of 20 and 12 years, respectively. No significant changes in JCP-specific IgE and total IgE levels were seen before and after RIT.

CONCLUSION

Allergen-induced CD203c expression in basophils may represent, at least in part, the cellular mechanism for the therapeutic responses to RIT for JCP pollinosis. However, further larger-scale studies to confirm the utility of the test are necessary.

Recombinant Allergens Promote Expression of Aminopeptidase-N (CD13) on Basophils in Allergic Patients

IgE-dependent activation of basophils is associated with upregulation of several surface molecules. We recently identified the surface enzyme aminopeptidase N (CD13) as a novel activation antigen on human basophils. In the present study, we asked whether CD13 can be employed as a novel marker of allergen-induced activation of basophils in allergic individuals. Patients allergic to major allergens from grass pollen (Phl p 1, Phl p 5), birch pollen (Bet v 1), or house dust mites (Der p 2), were examined. Blood basophils were exposed to various concentrations of recombinant allergens for 15 minutes, and examined for expression of CD13 by multicolor flow cytometry. The allergen-induced upregulation of CD13 was compared with allergen-dependent increases in expression of CD63 and CD203c. Exposure to recombinant allergens resulted in an increase in expression of CD13 on basophils in all sensitized individuals, whereas no increase in CD13 was seen in healthy controls. The effects of the recombinant allergens on CD13-expression were dose- and time-dependent, were not observed in the absence of extracellular calcium, and were counteracted by preincubation of basophils with the PI3-kinase-targeting drugs staurosporin and LY294002. There was a good correlation between allergen-induced upregulation of CD13, CD63, and CD203c on basophils. In aggregate, our data show that recombinant allergens promote expression of CD13 on basophils in sensitized individuals. The functional significance and diagnostic implications of this observation remain to be determined.

Interleukin-3 promotes the expression of E-NPP3/CD203C on human blood basophils in healthy subjects and in patients with birch pollen allergy

We recently identified the ectoenzyme CD203c as a novel basophil activation antigen that is upregulated in response to FcepsilonRI cross-linkage. We investigated the effects of various interleukins (ILs) on expression of CD203c on blood basophils using an antibody against CD203c and flow cytometry. Of all cytokines tested, only IL-3 was found to upregulate expression of CD203c on basophils above baseline levels. The effects of IL-3 were dose- and time-dependent (EC(50): 0.1-1 ng/ml) without differences observed between healthy and allergic donors. Whereas anti-IgE induced maximum upregulation of CD203c within 15 minutes, the IL-3-induced upregulation showed a maximum after 180 minutes. IgE-receptor cross-linking resulted in enhanced expression of both CD63 and CD203c, whereas IL-3 enhanced the levels of CD203c without promoting expression of CD63. The IL-3-induced upregulation of CD203c was also observed in highly enriched basophils and was counteracted by a blocking antibody against the alpha chain of the IL-3 receptor (CD123). The IL-3-induced upregulation of CD203c was also found to depend on the presence of calcium. To analyze signaling pathways involved in IL-3-induced upregulation of CD203c, pharmacologic inhibitors were applied. The PI3-kinase inhibitors, wortmannin and LY294002 counteracted the IL-3-induced expression of CD203c, whereas MEK- and PKC inhibitors showed no effects. In conclusion, IL-3 upregulates expression of CD203c on basophils through a specific receptor and via a PI3-kinase-dependent signaling-pathway. Compared to FcepsilonRI-mediated cell activation, IL-3-induced upregulation of CD203c is a late(r) event and is not accompanied by upregulation of CD63.

Diclofenac induces basophil degranulation without increasing CD63 expression in sensitive patients

Diclofenac (Dc) induces an IgE-independent basophil (Ba) degranulation in susceptible individuals. CD63 Ba expression is utilized as an in vitro test for diagnosis of drug hypersensitivity. We tested the ability of Dc to induce CD63 Ba expression by flow cytometry (BAT) and Ba degranulation using light microscopy (HBDT) in patients sensitive to Dc. We studied 14 patients with diclofenac hypersensitivity, also two patients sensitive to Dermatophagoides pteronyssinus (Dp), and 12 normal controls. HBDT was performed by mononuclear cells toluidine blue staining. BAT determined CD63 expression in antiCD63/anti-IgE/anti-CD45-labelled whole blood. In each case, the percentage of activated Ba post-stimulation with 1 and 10 microg/ml Dc was determined. Positive controls included N-formyl-methionyl-leucyl-phenylalanine (fMLP) peptide-induced activation. IgE-mediated Ba activation was induced with a Dp allergenic extract. With Dc 1 microg/ml, mean HBDT in Dc-susceptible individuals was 33.62 +/- 18.35% and 8.49 +/- 4.79% in controls (P = 0.0001). Mean BAT was 2.04 +/- 1.68% and 1.93 +/- 1.40% in controls (P = 0.8). Ba preincubation with Dc did not affect fMLP-induced CD63 expression, neither in Dc-sensitive individuals (P = 0.8) (n = 4) nor in subjects without Dc hypersensitivity (P = 0.25) (n = 4). Ba from the two patients sensitive both to Dc and Dp responded to Dp but not to Dc by BAT: Dc, 1.99 +/- 0.78%; Dp: 60.87 +/- 9.28%; but showed degranulation by HBDT: Dc, 30.53 +/- 1.02%, Dp: 48.78 +/- 22.17%. Dc induces Ba degranulation in sensitive patients in a way that does not induce CD63 expression and is different from IgE-mediated and fMLP-mediated degranulation. Our results suggest that CD63 expression is not a reliable diagnostic method for diclofenac allergy.

Expression of activation markers on basophils in a controlled model of anaphylaxis

BACKGROUND

Anaphylaxis has variable clinical presentations and lacks reliable biomarkers. Expression of activation markers on basophils has been useful in assessing sensitization in IgE-mediated diseases but has not been examined in vivo in anaphylaxis.

OBJECTIVE

The study's goals were to assess the baseline expression of activation markers on basophils in individuals with a sting reaction history, the degree of change in expression of these markers after intentional sting challenge, and the relationship between in vitro and in vivo activation marker expression.

METHODS

Patients allergic to insect venom were enrolled and grouped by clinical category defined by a history of a systemic or large local reaction and use of venom immunotherapy. Blood was collected before and after sting challenge. Enriched basophils were analyzed for activation marker expression. In select subjects, basophils were examined after in vitro stimulation with insect venom for activation marker expression and histamine release.

RESULTS

Of 35 sting-challenge participants, 21 provided adequate samples for analysis. Pre-sting basophil CD63 expression was significantly higher in systemic reactors on immunotherapy. Following sting challenge, the rise in basophil CD69 expression and CD203c was significantly higher in systemic reactors on immunotherapy. Levels of activation markers on basophils were greater after in vitro venom stimulation than after in vivo challenge.

CONCLUSION

Broader shifts in expression of basophil activation markers after in vivo challenge occurred among subjects with a history of in vivo systemic anaphylaxis despite venom immunotherapy.

CLINICAL IMPLICATIONS

Basophil activation markers may be potential biomarkers for anaphylaxis.

Flow-assisted allergy diagnosis: current applications and future perspectives

Physicians predominantly rely upon quantification of serum-specific immunoglobulin E (IgE) and/or skin test to confirm clinically suspected IgE-mediated allergy. However, for various reasons, identification of the offending allergen(s) and potentially cross-reactive structures is not always straightforward. Flow-assisted allergy diagnosis relies upon quantification of alterations in the expression of particular basophilic activation markers. Actually, upon challenge with a specific allergen, basophils not only secrete quantifiable bioactive mediators but also upregulate the expression of different markers which can be detected efficiently by flow cytometry using specific monoclonal antibodies. Currently, the technique has been applied in the investigation of IgE-mediated allergy caused by classical inhalant allergens, food, Hevea latex, hymenoptera venoms and drugs. It is also appreciated; the technique proves valuable in the diagnosis of non-IgE-mediated (anaphylactoid) reactions such drug hypersensitivity and the detection of autoantibodies in certain forms of chronic urticaria. This review will not address immunologic features, characteristics and general pitfalls of flow-assisted analysis of in vitro-activated basophils as summarized elsewhere. After a recapitulation of the principles and some specific technical issues of flow-assisted analysis of in vitro-activated basophils, we principally focus on the current clinical and research applications of the basophil activation tests. Personal experience of both research groups is provided, where appropriate. Finally, a viewpoint on how the field might evolve in the following years is provided.

Comparision of two-flow cytometry methods for basophil degranulation in patients sensitized to grass pollen

BACKGROUND

Two-flow cytometry methods for quantification of degranulated basophil after allergen-specific activation were discussed. The methods are discerned by used membrane receptors--FcepsilonRI or IL-3Ralpha Our goal was to evaluate the diagnostic potential of the methods and to correlate them to allergen-specific IgE detection and skin prick test (SPT).

METHODS

Patient's and control's groups were studied with Bulgarian grass pollen allergen B1 simultaneously by flow cytometry kits: Basotest and BD FastImmune test. Allergy diagnosis was based on clinical history and SPT. The determination of specific IgE was performed by ELISA--RIDASCREEN.

RESULTS

There were no significant differences between the patient's results from Basotest and FastImmune (P>0.05). A significant correlation between values, analyzed by Basotest and by FastImmune was found (r=0.88). The sensitivity and specificity of the Basotest, FastImmune, specific IgE and SPT were 85%, 72%, 92% and 92% sensitivity and 100%, 92%, 100% and 85% specificity respectively. The efficiency was between 82% and 97%. There were a significant correlation between the specific IgE and flow cytometry tests: tau=0.92 (Basotest) and tau=0.71 (FastImmune) and a moderate significant correlation between the SPT and the in vitro tests: tau=0.26 (Basotest) and tau=0.31 (FastImmune).

CONCLUSION

The successful use of the Bulgarian grass pollen allergen B1 and both flow cytometry tests was presented. These methods could be as specific tools for IgE-mediated diagnosis especially FastImmune in the case of low IgE receptor expression.

Factors responsible for differences between asymptomatic subjects and patients presenting an IgE sensitization to allergens. A GA2LEN project

The synthesis of allergen-specific IgE is required for the development of allergic diseases including allergic rhinitis and allergic asthma (patients), but many individuals with allergen-specific IgE do not develop symptoms (asymptomatic subjects). Differences may exist between asymptomatic subjects and patients. Whether the presence of allergen-specific IgE translates into clinical allergy most likely depends on a complex interplay of multiple factors. These include a family history of atopy, the levels of total serum IgE and, allergen-specific IgE or IgG, epitope-specificity of IgE and their degree of polyclonality (mono- vs polysensitized), as yet unidentified serum factors, the balance of T regulatory cells (Treg) and Th1/Th2 cells, the polymorphisms of the high affinity receptor for IgE (FcepsilonRI) and other factors regulating the activation of FcepsilonRI-bearing cells. Asymptomatic subjects may be more often monosensitized than patients who may be more often polysensitized. There are many unanswered important questions that need to be addressed in order to better understand how IgE sensitization translates into clinical allergy. The assessment of differences between the asymptomatic and symptomatic groups of subjects represent one of the scientific programs of Global Allergy and Asthma European Network funded by the European Union and the hypotheses underlying these differences are presented in this paper.

Significant correlation between the CD63 assay and the histamine release assay in chronic urticaria

BACKGROUND

Antibodies directed to the alpha subunit of the high affinity IgE receptor and the IgE molecule are proposed to be of pathogenetic relevance in a group of patients with chronic urticaria (CU). The diagnosis of autoimmune chronic urticaria (ACU) is difficult; the autologous serum skin test (ASST) seems to be a useful screening test, but reliable, additional confirmatory methods are needed.

OBJECTIVES

To assess the diagnostic value of a modified serum-induced basophil activation test, the CD63 expression assay, in the diagnosis of ACU by comparing the results of the CD63 assay with the results of the histamine release (HR) test, the ASST and serum levels of soluble CD40 ligand (sCD40L).

METHODS

Using basophils from an atopic (DA) and a nonatopic (DNA) donor the activity of sera of 72 patients with CU were measured in HR assay by enzyme-linked immunosorbent assay and in CD63 expression assay by flow cytometry. An ASST was carried out in all patients; in 30 of the 72 patients sCD40L was detected and correlations were derived between the different assays. Sera of 20 normal controls and 26 patients with systemic autoimmune diseases were also tested in the HR assay and in the CD63 expression assay.

RESULTS

Histamine-releasing activity was detected in the sera of 51% (DA) and 32% (DNA) of CU patients and 57% (DA) and 28% (DNA) of sera upregulated CD63 expression on the surface of basophils from the different donors. There was a significant correlation between the HR and the CD63 assays carried out on both donors, but the ASST showed a strong correlation with the HR assay only for basophils from the DA. The serum level of sCD40L was significantly higher in patients with CU compared with controls, but the difference between the autoimmune and the nonautoimmune groups was not significant.

CONCLUSIONS

The CD63 expression assay seems to be a reliable functional test in the diagnosis of ACU, particularly if highly sensitive donor basophils are used, but the determination of the sCD40L serum level was not sufficient to differentiate between the autoimmune and the nonautoimmune patient groups.

Surface plasmon resonance immunosensor for histamine based on an indirect competitive immunoreaction

The use of a surface plasmon resonance immunosensor for the analysis of histamine (beta-imidazole ethylamine) is described. The method is based on an indirect competitive reaction of an anti-histamine antibody in a sample solution with histamine immobilized on a sensor chip and with histamine in the sample solution. A sensor chip immobilized with histamine was prepared using a self-assembly monolayer of 11-mercaptoundecanoic acid (11-MUA) as an anchor membrane, followed by an amino-coupling reaction with histamine after activation of the 11-MUA layer on the sensor chip by treatment with 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide and N-hydroxysuccinimide. The sensor chip can be reused, after regeneration with a 10mM HCl solution, which dissociates the anti-histamine antibody complex from histamine on the sensor chip. The affinity constants for the immunocomplex of the anti-histamine antibody with histamine in the solution and for that of the anti-histamine antibody with histamine immobilized on the sensor chip were calculated to be 1.5 x 10(7) and 7.2 x 10(5) M(-1), respectively, by assuming a Langmuir-type adsorption of the anti-histamine antibody to histamine immobilized on the sensor chip. The detection limit of the method was determined to be 3ppb.

Diagnosis of neuromuscular blocking agent hypersensitivity reactions using cytofluorimetric analysis of basophils

BACKGROUND

Immunoglobulin E (IgE)-mediated hypersensitivity reactions to neuromuscular blocking agents (NMBA) are common and life threatening. Basophil activation based upon the expression of CD63 in the presence of specific allergens was found to be of importance for the diagnosis of IgE-mediated hypersensibility.

METHODS

The Basotest was evaluated for the diagnosis of NMBA in 47 patients with proven NMBA anaphylaxis, 40 atopic subjects nonallergic to NMBA and five healthy volunteers. Diagnosis of NMBA was made according to international standards on clinical history, skin tests and provocation tests when needed.

RESULTS

In the NMBA allergic patients, sensitivity of Basotest was 36.1%, but it increased to 85.7% for reactions which occurred within the last 3 years. The specificity was 93.3%.

CONCLUSION

Basotest may be useful for the diagnosis of NMBA allergy in patients with a suspicion of recent IgE-mediated hypersensitivity reaction to NMBA.

Detection of Anisakis simplex-induced basophil activation by flow cytometry

BACKGROUND

Laboratory diagnosis of anisakidosis is based on specific serum IgE detection. Recently, detection of allergen-induced basophil activation by flow cytometry has been proposed as a valuable tool for allergy diagnosis.

OBJECTIVE

To evaluate if detection of Anisakis-induced basophil activation by flow cytometry is a useful tool in the diagnosis of Anisakis allergy.

METHODS

Patients with Anisakis allergy (A.s.+, n = 37), patients reporting chronic urticaria or abdominal pain unrelated to fish ingestion (A.s.-, n = 51), and healthy controls (n = 12) were studied. Specific IgE to Anisakis simplex (A. simplex) was quantified with CAP-FEIA method, and basophil activation test was performed with three different concentrations of an Anisakis crude extract. Basophil gating was performed with CD123 and HLA-DR, and cellular activation was measured with CD63.

RESULTS

A.s.+ patients showed significantly higher age and total IgE levels than did the A.s.- patients. Specific IgE to A. simplex correlated with the activated basophil percentages obtained with 15 microg/mL (r = 0.80; P < 0.001), 1.5 microg/mL (r = 0.84; P < 0.001), and 0.15 microg/mL (r = 0.82; P < 0.001) of A. simplex crude extract. Nine individuals (3 in the A.s.+ group and 6 in the A.s.- group) were nonresponders to basophil stimulation with anti-IgE. Five A.s.- patients showed positive IgE values to A. simplex while the basophil activation test was negative. According to the receiver operating characteristics curves performed between A.s.+ vs. A.s.- and A.s.+ vs. healthy controls, the cutoff for a positive basophil activation test was >or=21% (specificity = 96%, sensitivity = 100%), and 16% (sensitivity and specificity of 100%) respectively. When nonresponders were included in the A.s.+ vs. A.s.- analysis, sensitivity decreased to 95%. Multivariate logistic analysis showed that the specific basophil activation was a factor independently associated with clinical symptoms of A. simplex allergy.

CONCLUSIONS

Detection of A. simplex-induced basophil activation by flow cytometry is a useful laboratory technique for the diagnosis of anisakidosis, supplementing specific IgE determinations.

Polysorbate 80 in medical products and nonimmunologic anaphylactoid reactions

BACKGROUND

Polyoxyethylene-sorbitan-20-monooleate (also known as polysorbate 80 and Tween 80) is a solubilizing agent ubiquitously used in nutritives, creams, ointments, lotions, and multiple medical preparations (e.g., vitamin oils, vaccines, and anticancer agents) and as an additive in tablets. Whereas its relevance as a contact allergen has declined during the past decades, it is of current relevance as a "hidden" inductor of anaphylactoid reactions.

OBJECTIVE

To identify polysorbate 80 (generally believed to be an inert vehicle) as an inductor of a severe anaphylactoid reaction.

METHODS

Skin prick testing, enzyme-linked immunosorbent assay, IgE immunoblotting, and flow cytometric detection of basophil activation were performed in controls and in a patient with a medical history of anaphylactic shock due to intravenous administration of a multivitamin product during pregnancy.

RESULTS

Polysorbate 80 was identified as the causative agent for the anaphylactoid reaction of nonimmunologic origin in the patient. Polysorbate specific IgE antibodies were not identified in enzyme-linked immunosorbent assay and immunoblot examinations, confirming the nonimmunologic nature of the anaphylactoid reaction.

CONCLUSIONS

Polysorbate 80 is a ubiquitously used solubilizing agent that can cause severe nonimmunologic anaphylactoid reactions.

The basophil activation test by flow cytometry: recent developments in clinical studies, standardization and emerging perspectives

The diagnosis of immediate allergy is mainly based upon an evocative clinical history, positive skin tests (gold standard) and, if available, detection of specific IgE. In some complicated cases, functional in vitro tests are necessary. The general concept of those tests is to mimic in vitro the contact between allergens and circulating basophils. The first approach to basophil functional responses was the histamine release test but this has remained controversial due to insufficient sensitivity and specificity. During recent years an increasing number of studies have demonstrated that flow cytometry is a reliable tool for monitoring basophil activation upon allergen challenge by detecting surface expression of degranulation/activation markers (CD63 or CD203c). This article reviews the recent improvements to the basophil activation test made possible by flow cytometry, focusing on the use of anti-CRTH2/DP2 antibodies for basophil recognition. On the basis of a new triple staining protocol, the basophil activation test has become a standardized tool for in vitro diagnosis of immediate allergy. It is also suitable for pharmacological studies on non-purified human basophils. Multicenter studies are now required for its clinical assessment in large patient populations and to define the cut-off values for clinical decision-making.

Identification of CD13, CD107a, and CD164 as novel basophil-activation markers and dissection of two response patterns in time kinetics of IgE-dependent upregulation

Using two-colour flow cytometry >200 antibodies submitted to the 8th International Workshop of Human Leukocyte Differentiation Antigens (HLDA8) have been analyzed for their reactivity with resting and activated CD203c+ basophils. Four antibodies either non-reactive or weakly reactive with resting basophils exhibited an increased reactivity with basophils activated by anti-IgE-mediated cross-linking of the high affinity IgE receptor (FceRI). These include antibodies against CD164 (WS-80160, clone N6B6 and WS-80162, clone 67D2), as well as two reagents with previously unknown specificities that were identified as CD13 (WS-80274, clone A8) and CD107a (WS-80280, clone E63-880). The activation patterns followed either the "CD203c-like" or "CD63-like" activation profile. The CD203c profile is characterized by a rapid and significant upregulation (of CD13, CD164, and CD203c), reaching maximum levels after 5-15 min of stimulation. The Phosphoinositide-3-kinase (PI3K)-specific inhibitor Wortmannin inhibited the upregulation of these markers whereas 12-O-tetradecanoyl-phorbol-13-acetate (TPA) induced a rapid and FceRI-independent upregulation within 1-2 min. In the CD63 profile, maximum upregulation (of CD63 and CD107a) was detected only after 20-40 min, and upregulation by TPA reached maximum levels after 60 min. In summary, our data identify CD13, CD107a, and CD164 as novel basophil-activation antigens. Based on time kinetics of upregulation, we hypothesize that molecules of the "CD203c group" and the "CD63 group" are linked to two different mechanisms of basophil activation.

Allergy to cypress pollen

Although Cupressus sempervirens has been spread over southern Europe since antiquity, cypress pollen allergy has not been reported until 1945. In France, the very first case reports were published in 1962. Since then, the prevalence of cypress pollinosis seems to demonstrate an upward trend, concomitantly with the increased use of cypress trees as ornamental plants, as wind breaks and as hedges. Hyposensitization, using improved pollen extracts, is increasingly prescribed. Besides, prevention measures begin to be implemented. Such measures include avoidance of planting new cypress trees, especially near human populations' centres, trimming of cypress hedges before the pollination season and agronomical research for hypoallergenic trees. Altogether, such new developments in cypress allergy deserve an update review.

Flow cytometric analysis of in vitro activated basophils, specific IgE and skin tests in the diagnosis of pollen-associated food allergy

BACKGROUND

Specific immunoglobulin E (IgE) and commercially available skin prick tests have been demonstrated to be unreliable methods to diagnose pollen-associated food allergy. To evaluate the predictive value of the basophil activation test (BAT) in pollen-associated food allergy, the apple-mediated oral allergy syndrome (OAS) in patients with birch pollinosis was chosen as a representative model.

METHODS

Patients with birch pollen allergy and a history of apple-mediated OAS (OAS(+), n = 29), patients with birch allergic without OAS (OAS(-), n = 22), and healthy controls (HC, n = 10) without birch pollen allergy and OAS were included. Apple IgE was quantified by the CAP FEIA method. Skin prick tests were performed with a Jonagold apple extract. Flow cytometric analysis of basophils activated with the same Jonagold extract was based on double staining with anti-IgE/anti-CD63 monoclonal antibodies.

RESULTS

Comparison between OAS(+) subjects and HC showed sensitivities and specificities of 96% and 100% for apple IgE and 88% and 100% for the apple skin prick test, respectively. For the BAT, sensitivity and specificity were 100%. In contrast, when nonresponders on the BAT were considered, sensitivity decreased to 90%. In a separate analysis between OAS(+) and OAS(-) subjects, specificities decreased to 30% for apple IgE and to 80% for the apple skin test, respectively. The BAT reached a sensitivity of 88% and a specificity of 75%.

CONCLUSION

Flow cytometry-assisted quantification of in vitro basophil activation seems to be a reliable instrument in the diagnosis of this model of pollen-associated food allergy. In addition, this study reemphasizes that the specificity of diagnostic allergy tests decreases considerably when, apart from HC, control individuals with cross-reactive antibodies are included.

Confirmation of the diagnosis of natural rubber latex allergy by the Basotest method

BACKGROUND

The flow cytometry CD63-based basophil activation test (Basotest has already been validated for the diagnosis of immediate-type allergy such as venom, house dust mite or cypress pollen allergies. The aim of this study was to evaluate the performance (specificity and sensitivity) of Basotest in the diagnosis of natural rubber latex allergy.

METHODS

We included 46 latex allergic patients (clinical symptoms of latex allergy, positive latex skin prick tests and/or latex specific IgE) and 33 control subjects and performed Basotest on all subjects.

RESULTS

The sensitivity and specificity of Basotest were 84.8 and 87.9%, respectively, when we considered the theoretic cut-off at 15% of CD63-positive cells. Using ROC curves, the optimal cut-off was evaluated at 22%, for which sensitivity and specificity were 79.3 and 96.7%, respectively.

CONCLUSION

The Basotest is a reliable test in addition to clinical history and tests already validated (such as skin prick tests and specific IgE) to confirm the diagnosis of natural rubber latex allergy.

Hypoallergenic variants of the major latex allergen Hev b 6.01 retaining human T lymphocyte reactivity

Hev b 6.01 is a major allergen of natural rubber latex with sensitization of 70-86% of latex glove-allergic subjects. Recently, we mapped the immunodominant T cell sites of Hev b 6.01 to the highly IgE-reactive hevein (Hev b 6.02) domain. Hev b 6.01 contains 14 cysteine residues with multiple disulphide bridges stabilizing tertiary conformation. With the goal of a standardized specific immunotherapy we developed hypoallergenic Hev b 6.01 mutants by site-directed mutagenesis of selected cysteine residues (3, 12, 17, and 41) within the Hev b 6.02 domain. Peptides corresponding to the Hev b 6.02 domain of two of the mutants were also synthesized. These mutants and peptide variants showed markedly decreased or ablated latex-allergic patient serum IgE binding by immunoblotting and ELISA. Basophil activation testing confirmed markedly decreased activation with successive cysteine substitutions of the mutants and complete abrogation with the Hev b 6.02 (Cys 3, 12, 17, 41 Ala) peptide. Retention of T cell reactivity is crucial for effective specific immunotherapy and all mutants and peptide variants maintained their latex-specific T cell reactivity. The ablated allergenicity but retained T cell reactivity of the Hev b 6.02 (Cys 3, 12, 17, 41 Ala) peptide suggests this peptide is a suitable candidate for inclusion in a latex immunotherapy preparation.

Assays for measuring in vitro basophil activation induced by recombinant allergens

The diagnosis of type I allergy is essentially based on clinical data, skin tests, and measurements of allergen-specific IgE. However, the determination of specific IgE per se does not permit a definitive conclusion concerning the response of effector cells to the respective allergen(s) and consecutive clinical symptoms in all patients. In an attempt to overcome this problem, a number of basophil-activation assays have been developed during the last few years. Today, allergen-induced activation of blood basophils can be employed as a specific and reliable measure of IgE-dependent responses in sensitized individuals. Using recombinant allergens and basophil-specific markers, these novel assays appear to serve as simple and useful tests in component-resolved diagnosis of type I allergies. In the current article, the biochemical, functional, and technical background of these basophil tests is discussed.

The basophil activation test in wasp venom allergy: sensitivity, specificity and monitoring specific immunotherapy

BACKGROUND

As in vitro diagnosis of wasp venom sensitization by specific serum IgE has a sensitivity of only 60-80%, additional in vitro tests are desirable. Basophil activation is associated with the expression of CD63 and its measurement has been proposed as a novel in vitro test for immediate-type allergy. Furthermore, to date, no in vitro test exists to monitor successful specific immunotherapy (SIT) with wasp venom. Therefore, the potentially harmful sting challenge is still recommended.

OBJECTIVE

We compared the CD63-based basophil activation test (BAT) in the diagnosis of wasp venom allergy with skin tests and measurement of specific IgE. Furthermore, we investigated whether BAT can predict the outcome of the sting challenge in patients on SIT.

METHODS

Fifty patients with a systemic reaction caused by a wasp sting and 20 controls were studied. Intracutaneous tests were performed with wasp and bee venom in the suspected allergics. Specific IgE was determined by the CAP-FEIA method and basophil activation by flow cytometry upon double staining with anti-IgE/anti-CD63 mAb. Twenty-five patients were sting challenged 6 months after starting SIT and the BAT was repeated before challenge.

RESULTS

Sensitivity of the intracutaneous tests, specific IgE and BAT was 100, 76, and 92%, respectively. Specificity of specific IgE and the BAT was 85 and 80%, respectively. The cut-off for a positive BAT was 15% CD63+ basophils. There was a positive correlation between IgE reactivity to wasp venom and the number of CD63+ basophils (r = 0.65). Although no patient had a systemic reaction upon sting challenge, in most subjects basophil activation did not decrease when compared with the BAT before SIT.

CONCLUSIONS

Quantitation of basophil activation by CD63 expression is a valuable new in vitro method for diagnosis of allergy to hymenopteran venoms. The CD63-based BAT is a helpful tool for the complementation of routine diagnostic tests such as specific IgE as it increases sensitivity of in vitro detection of sensitization. However, this in vitro method does not offer an alternative to the sting challenge in monitoring successful SIT.

Sinus CT scans and mediator release in nasal secretions after nasal challenge with cypress pollens

BACKGROUND

Involvement of paranasal sinuses has been suggested in allergic rhinitis but not clearly demonstrated.

AIMS

To investigate the relationship between intermittent allergic rhinitis and computerized tomography (CT).

METHODS

Twenty patients with intermittent rhinitis and sensitized to cypress pollens underwent unilateral nasal provocation tests (NPTs) using increasing concentrations of cypress pollens out of the pollen season. Sinus CT-scans were carried out just before a NPT and 24 h later. Nasal lavage was carried out just before a NPT, 30 min after a positive challenge and again 24 h later. Leucotriene C4/D4, intracellular adhesion molecule-1 and eosinophil cationic protein were measured in nasal secretions.

RESULTS

Thirteen patients (65%) showed an alteration in their CT-scans after allergen challenge. Ten of them showed sinus changes controlateral to their allergenic provocation. Radiological changes mainly affected the osteomeatal complex and the ethmoid sinuses. Pre-existing abnormalities (13 of 20 cases) mainly concerned the maxillary sinuses. There was no correlation between CT-scan abnormalities and levels of mediators released in nasal secretions.

CONCLUSIONS

We have shown that nasal allergen challenge can produce radiological changes in the paranasal sinuses. This mainly concerned the ethmoid sinuses.

In vitro allergy diagnosis: should we follow the flow?

During the last 5 years, an increasing number of studies have demonstrated that flow cytometric quantification of in vitro basophil activation can be a quite performant and reliable tool to measure IgE-dependent allergen-specific responses in allergic patients. So far, most assays have used CD63 as a basophil activation marker and native allergen extracts for stimulation. However, other basophil markers and recombinant allergens have recently been introduced. The technique has been applied for the diagnosis of allergy to pollen, house dust mite, food, natural rubber latex, hymenoptera venom and drugs. In addition, the technique has proven to be useful in non-IgE-mediated reactions such as hypersensitivity to drugs as well as detection of auto-antibodies in chronic urticaria. This review will focus on some specific issues: (1) principles of flow cytometric analysis of in vitro-activated basophils, (2) general technical aspects of the technique (including passive sensitization), (3) clinical applications and (4) recommendations for further development and evaluation of the technique.

The basophil-specific ectoenzyme E-NPP3 (CD203c) as a marker for cell activation and allergy diagnosis

Basophils are effector cells of allergic reactions. These cells produce and store a number of vasoactive and immunomodulatory mediators. During an allergic reaction, basophils can release their mediator substances into the extracellular space and thus contribute to the clinical picture and symptoms in allergy. The phenotypic hallmark of basophils is expression of high-affinity IgE receptors (Fc epsilon RI) on their cell surface together with expression of the activation-linked molecule CD203c. This ectoenzyme is located both on the plasma membrane and in the cytoplasmic compartment of basophils. Cross-linking of the Fc epsilon RI by an allergen or anti-IgE antibody results in a rapid upregulation of intracellular CD203c molecules to the cell surface and is accompanied by mediator release. CD203c is therefore a promising target molecule for a flow cytometry-based test to analyze sensitized individuals and patients with type I allergy. In the present article, we review the current knowledge of CD203c with special regard to its tissue distribution and regulation in basophil activation. In addition, we discuss the application of CD203c in allergy diagnosis.

Allergic reactions occurring during anaesthesia: diagnostic approach

Anaphylactic and anaphylactoid reactions to anaesthetic and associated agents used during the perioperative period have been increasingly reported during the last 3 decades. The frequency of life-threatening hypersensitivity reactions occurring during anaesthesia has been estimated to vary between 1/1.000 and 1/25.0000 procedures, with muscle relaxants being involved in almost three quarters of the cases. The mortality from these reactions is in the range of 3-6%. Nowadays, natural rubber latex also accounts for a significant number of perioperative anaphylaxis, particularly in children. Clinical manifestations do not allow to differentiate between IgE-mediated anaphylaxis and anaphylactoid reactions resulting from non-specific mediator release. Successful management of these patients requires multidisciplinary approach and includes prompt recognition and stabilisation of the acute event by the attending anaesthetist, determination of the responsible agent(s) with avoidance of subsequent administration of incriminated compound(s). The latter is based upon correct identification of the responsible drug and potentially cross-reactive compounds by the allergist and requires a detailed review of the anaesthetic report as well as appropriate in vitro and in vivo allergy tests. At present, the overall performance of skin tests makes them the "gold standard" for diagnosis of muscle relaxant-induced perioperative hypersensitivity reactions. In addition, given their good negative predictive value, skin tests have been proven to be a useful tool to tailor the appropriate therapeutic alternative. For other compounds diagnosis is more difficult but newer techniques such as analysis of in vitro activated basophils can be helpful.

Measurement of basophil-activating capacity of grass pollen allergens, allergoids and hypoallergenic recombinant derivatives by flow cytometry using anti-CD203c

BACKGROUND

The assessment of the basophil-activating potential is an important aspect in the development of improved preparations for specific immunotherapy. The aim of the study was to evaluate the suitability of CD203c expression as a measure of basophil activation to compare allergoids with original allergen extracts, and recombinant hypoallergenic allergen derivatives with recombinant wild-type and natural allergens.

METHODS

Heparinized whole blood samples from grass pollen allergic subjects were stimulated with grass pollen allergens and allergen derivatives followed by labelling of the basophils with PE-conjugated anti-CD203c. After lysis of the erythrocytes and fixation, the basophils were detected by flow cytometry. In some experiments, histamine release was determined simultaneously.

RESULTS

Grass pollen allergoids revealed a 10-10 000-fold reduction of basophil-activating capacity measured by CD203c expression. The deletion mutant DM4 of rPhl p 5b showed stronger hypoallergenic characteristics in a range of 50-10 000-fold reduction, whereas a combination mutant of rPhl p 5b and Phl p 6 revealed less hypoallergenic features. Histamine release experiments led to a similar outcome as CD203c measurement.

CONCLUSIONS

The measurement of CD203c expression on basophils by flow cytometry provides a rapid and sensitive method for the estimation of the allergic or hypoallergenic features of allergen preparations. The results demonstrated the hypoallergenicity of grass pollen allergoids and of the rPhl p 5b variant DM4, which may be a candidate in future preparations for specific immunotherapy.

Allergen-induced mediator release tests

The diagnosis of allergic reactions in clinical practice is based on both clinical history and the determination of specific immunoglobulin E (IgE), either in the serum or on skin mast cells. However, for various reasons, identification of the causative factors is not possible in all the cases. Moreover, not all allergies are IgE-dependent. In an attempt to find sensitive, specific and cost-effective methods to investigate hypersensitivity reactions, in vitro tests were developed at a very early stage. Allergen-induced mediator release assays analyze the mediator released from effector cells, mainly peripheral blood cells, when stimulated in vitro with serial dilutions of the putative allergens. Described initially as research tools, they could well become diagnostic tests. However, relatively few high quality reports have been published so far. In this review, we will detail allergen-dependent histamine, tryptase, arachidonic acid metabolite, e.g. cysteinyl leukotrienes and 15-hydroxyeicosatetraenoic mediator release tests.