Laboratory-based allergy diagnosis: should we go with the flow?

Comparison of Skin Prick Tests (SPT), Intradermal Tests (IDT) and In Vitro Tests in the Characterization of Insect Bite Hypersensitivity (IBH) in a Population of Lusitano Horses: Contribution for Future Implementation of SPT in IBH Diagnosis

Thirty controls (C) and 30 IBH-affected (T) Lusitano horses were evaluated. T horses were included based on anamnesis and physical examination, supported by questionnaires. All horses were submitted to skin tests, Intrademal (IDT) and Skin Prick Tests (SPT), on the neck with 14 specific allergens, 13 recombinant proteins (r-proteins) from Culicoides nubeculosus (Cul n) and Culicoides obsoletus (Cul o) salivary glands and Culicoides nubeculosus Whole Body Extract (Cul n WBE). Addicionally, a cluster of six T and six C horses were also tested with Cul n 3 and Cul n 4 produced in insect cells and barley, as well as E. coli produced Cul o 3 and Cul o WBE. Allergen concentrations were 10 µg/mL for IDT and 100 µg/mL for SPT, and wheal diameters assessed at 20 min, 6 and 48 h. IDTs were considered positive when wheal diameter was ≥50% of the histamine wheal and SPT's ≥ 0.9 cm. In vitro tests, allergen-specific serum IgE and sulfidoleukotriene (sLT) release assay were also carried out. Results showed that Cul n WBE, Cul n 7, 8, 9, Cul o1P and Cul o 2P were the best performing allergens for SPTs (p ≤ 0.0001) for the 1st allergen panel and Cul o WBE, Cul n 3 Bar and Cul n 4 Bac (p ≤ 0.05) for the 2nd, presenting a higher discriminatory diagnostic potential than IDTs, at a concentration of 100 µg/mL, with readings assessed at 20 min. Regarding in vitro tests overall, the sLT release assay performed best.

Basophil models of homeopathy: a sceptical view

This paper examines the activation and inhibition of activation of human basophils. After a brief description of human basophils, different methods to determine basophil activation are discussed with a special emphasis on the use of flow cytometric methods, as these circumvent the potential problems of assays based on the loss of colour by activated basophils. The activation of human basophils by ultra-high dilutions of anti-IgE is discussed. The majority of the paper describes the inhibition of basophil activation by ultra-high dilutions of histamine. The results from published papers are described and discussed. After over 20 years research trying to find out if high dilutions of histamine have a negative feedback effect on the activation of basophils by anti-IgE, what do we know? The methods are poorly standardized between laboratories - although the same is true for conventional studies. Certainly there appears to be some evidence for an effect - albeit small in some cases - with the high dilutions in several different laboratories using the flow cytometric methodologies. After standardization of a number of parameters, it is recommended that a multi-centre trial be performed to hopefully put an end to this "never-ending story".

Inhibition of basophil activation by histamine: a sensitive and reproducible model for the study of the biological activity of high dilutions

BACKGROUND

At the beginning of this series of experiments we were looking for a model based on the use of purified commercially available compounds based on a fully described and accepted pharmacological model to study of the biological effect of high dilutions. Negative feedback induced by histamine, a major pro-inflammatory mediator, on basophils and mast cells activation via an H2 receptor me these criteria. The simplest way of measuring basophil activation in the early 1980's was the human basophil activation test (HBDT).

OBJECTIVES

Our major goal was first to study the biological effect of centesimal histamine dilutions beyond the Avogadro limit, on the staining properties of human basophils activated by an allergen extract initially house dust mite, then an anti-IgE and N-formyl-Met-Leu-Phe (fMLP). Technical development over the 25 years of our work led us to replace the manual basophil counting by flow cytometry. The main advantages were automation and observer independence. Using this latter protocol our aim was to confirm the existence of this phenomenon and to check its specificity by testing, under the same conditions, inactive analogues of histamine and histamine antagonists. More recently, we developed an animal model (mouse basophils) to study the effect of histamine on histamine release.

METHODS AND RESULTS

For the HBDT model basophils were obtained by sedimentation of human blood taken on EDTA and stained with Alcian blue. Results were expressed in percentage activation. Histamine dilutions tested were freshly prepared in the lab by successive centesimal dilutions and vortexing. Water controls were prepared in the same way. For the flow cytometric protocol basophils were first labeled by an anti-IgE FITC (basophil marker) and an anti-CD63 (basophil activation marker). Results were expressed in percentage of CD63 positive basophils. Another flow cytometric protocol has been developed more recently, based on basophil labeling by anti-IgE FITC (fluorescein isothiocyanate) and anti-CD203 PE (another human basophil activation marker). Results were expressed in mean fluorescence intensity of the CD203c positive population (MFI-CD203c) and an activation index calculated by an algorithm. For the mouse basophil model, histamine was measured spectrofluorimetrically. The main results obtained over 28 years of work was the demonstration of a reproducible inhibition of human basophil activation by high dilutions of histamine, the effect peaks in the range of 15-17CH. The effect was not significant when histamine was replaced by histidine (a histamine precursor) or cimetidine (histamine H2 receptor antagonist) was added to the incubation medium. These results were confirmed by flow cytometry. Using the latter technique, we also showed that 4-Methyl histamine (H2 agonist) induced a similar effect, in contrast to 1-Methyl histamine, an inactive histamine metabolite. Using the mouse model, we showed that histamine high dilutions, in the same range of dilutions, inhibited histamine release.

CONCLUSIONS

Successively, using different models to study of human and murine basophil activation, we demonstrated that high dilutions of histamine, in the range of 15-17CH induce a reproducible biological effect. This phenomenon has been confirmed by a multi-center study using the HBDT model and by at least three independent laboratories by flow cytometry. The specificity of the observed effect was confirmed, versus the water controls at the same dilution level by the absence of biological activity of inactive compounds such as histidine and 1-Methyl histamine and by the reversibility of this effect in the presence of a histamine receptor H2 antagonist.

Serum-induced basophil CD63 expression by means of a tricolour flow cytometric method for the in vitro diagnosis of chronic urticaria

BACKGROUND

Functional autoantibodies against the alpha-chain of the high-affinity IgE receptor (FcepsilonRIalpha) identify a subset of patients with chronic urticaria (CU) due to autoreactivity, as assessed by an in vivo positive response to autologous serum skin test (ASST). We performed a study to standardize the serum-induced basophil activation assay by flow cytometry (FCM) using a new tricolour method, assessing the diagnostic performance of this test in discriminating between ASST+ and ASST- CU patients.

METHODS

Sera of 64 CU patients (22 ASST+ CU and 42 ASST- CU) and 10 healthy subjects were tested for their ability to induce basophil CD63 expression when incubated with whole blood of both atopic (DA) and non-atopic donors (DNA). Using a triple-labelled strategy with anti-CD123, anti-HLA-DR and anti-CD63 antibodies, CD63+ basophils were identified on a selected population of CD123+ HLA-DR- cells. In 3 ASST+ CU patients who underwent cyclosporine therapy, the assay was performed before and after treatment.

RESULTS

The ASST+ CU sera resulted in a significant higher induction of basophil CD63 expression compared with ASST- CU and healthy donors sera; when whole blood from DA was used, sensitivity and specificity of the assay were 95.5% and 90.5% respectively. ASST+ CU serum activity was significantly decreased during cyclosporine A treatment, in parallel with clinical remission.

CONCLUSIONS

Chronic urticaria serum-induced CD63 expression assay performed on DA whole blood by means of our tricolour FCM method could be the most useful tool for identification of a subset of patients with autoimmune CU and may become a promising tool also for monitoring treatment efficacy.

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.

Immediate-type allergy to drugs and related compounds: evaluation and management

Adverse drug reactions (ADR) constitute a major health issue in outpatient and inpatient clinical settings. An allergic drug reaction is an immunologically mediated adverse drug reaction that exhibits specificity and recurrence on re-exposure to the offending and/or cross-reactive compound(s). Diagnosis of drug allergy is difficult, as a broad spectrum of different drugs can elicit various immune-mediated diseases with distinct (sometimes unclear) pathomechanism, the exact structure (epitope) that causes the reaction is frequently unknown, the presence of an in vitro or in vivo test results might not be predictive of a clinical situation, and the gold standard or reference test for diagnosis, the drug challenge, is a complicated and sometimes dangerous endeavour. Nevertheless, during the past few years serious attempts have been made to standardise and validate in vitro and in vivo techniques for the diagnosis of drug allergy. New techniques, e.g. flow-assisted analysis of in vitro basophil activation, are replacing older ones like histamine release for immediate-type hypersensitivity reactions. However, additional comprehensive studies are required to further validate the technique and allow its entrance in mainstream diagnostic use, particularly for non-IgE-mediated hypersensitivity. This review attempts to summarize the major causes of immediate hypersensitivity reactions to drugs and related compounds. Special attention is paid to the diagnostic and therapeutic management of this common iatrogenic complication.

Priorities and methods for developing the evidence profile of homeopathy Recommendations of the ECH General Assembly and XVIII Symposium of GIRI

To achieve scientific acceptance, homeopathy must investigate several questions: 1. The activity of very highly diluted preparations. The consensus of the meeting was that there is clear evidence of this. 2. The content of very highly diluted homeopathic preparations. More research is needed but evidence exists that a specific signal is present in homeopathic preparations. 3. A theoretical framework in which the effects of homeopathic diluted preparations can be explained. The 'Body Information Theory' is such a theory. 4. The clinical effectiveness of homeopathy. Because they avoid the placebo effect, animal studies are a priority. For human trials using Quality of Life questionnaires, studies on the activity, content and theoretical basis of homeopathic preparations were reviewed approximately 70% of cases; more in children showed improvement. Homeopathy reduced costs and allowed a better improvement in work-days lost compared with conventional practice. Randomised controlled trials (RCTs) implicitly test the placebo hypothesis; RCTs have been performed and meta-analyses conclude that there is clear evidence of efficacy which cannot be attributed to placebo effect. Priorities depend on the audience. More research is needed especially regarding the content of homeopathic preparations and the transmission of information. Theoretical issues are also important to avoid incorrect design of research protocols. More effort should be dedicated to veterinary research. Clinical effects analysis in humans remains important. Many other questions should be prioritised, such as the potential of homeopathy to avoid invasive procedures in children and the long-term effects of homeopathy in preventing chronic complications.

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.

In vitro testing to diagnose venom allergy and monitor immunotherapy: a placebo-controlled, crossover trial

BACKGROUND

In people with a history of sting allergy, only prior reaction severity and older age are known to predict subsequent reaction risk. Furthermore, no diagnostic test other than a deliberate sting challenge has been found to identify people in whom venom immunotherapy (VIT) has been unsuccessful.

OBJECTIVE

We aimed to assess the utility of a number of in vitro tests to diagnose venom allergy and to monitor immunotherapy.

METHODS

During a double-blind randomized placebo-controlled crossover trial of Myrmecia pilosula ant VIT the following venom-specific tests were performed at enrolment, and at completion of treatment prior to a diagnostic sting challenge; leucocyte stimulation index (SI), IL-4 production, IgE RAST, histamine release test (HRT), leukotriene release test (LRT) and basophil activation test (BAT). Intradermal venom skin testing (VST) was also performed at trial entry.

RESULTS

Only VST and HRT identified those at risk of sting anaphylaxis in the placebo group. Although IgE RAST, leucocyte SI and IL-4 production, LRT and BAT all correlated well with intradermal VSTs, they did not predict sting challenge outcome. After successful VIT, venom-induced leucocyte IL-4 production tended to fall, whereas IgE RAST increased and a natural decline in HRT reactivity was reversed. A confounding seasonal affect on laboratory results was suspected.

CONCLUSION

The HRT warrants further assessment for diagnosis of venom allergy. Uninformative performance of the commercially available LRT and BAT tests may be due to pre-incubation with IL-3. None of the tests evaluated appear to be reliable markers of successful VIT.

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.

CD63 expression on basophils as a tool for the diagnosis of pollen-associated food allergy: sensitivity and specificity

BACKGROUND

Basophil activation is associated with the expression of CD63. Because allergens can induce basophil activation by cross-linking specific IgE, increased CD63 expression has been proposed as a novel in vitro test for immediate type allergy.

OBJECTIVE

We compared the CD63-based basophil activation test (BAT) in the diagnosis of allergy to carrot, celery and hazelnut with skin prick tests (SPT) and measurement of allergen-specific IgE.

METHODS

Twenty-nine patients with a history of an oral allergy syndrome induced by carrot, celery or hazelnut (n = 20 for each allergen) and 20 controls were studied. SPT were performed with standardized and native carrot, celery and hazelnut extracts. Allergen-specific IgE was determined by the CAP FEIA method and basophil activation was determined by flow cytometry upon double staining with anti-IgE/anti-CD63 mAb.

RESULTS

SPT with native carrot, celery and hazelnut showed sensitivities of 100%, 100% and 90%, and specificities of 80%, 80% and 90%. SPT with commercial extracts of the same allergens gave sensitivities of 85%, 80% and 85%, and specificities of 80%, 80% and 90%. Sensitivity of allergen-specific IgE and the BAT for carrot, celery and hazelnut was 80% vs. 85%, 70% vs. 85%, and 80% vs. 90%, with corresponding specificities of 80% vs. 85%, 80% vs. 80%, and 95% vs. 90%. The cut-off for a positive BAT was 10% CD63+ basophils. Moreover, there was a positive correlation between IgE reactivity and the number of CD63+ basophils for all food allergens (carrot: r = 0.69, celery: r = 0.67, hazelnut: r = 0.66).

CONCLUSIONS

Quantification of basophil activation by CD63 expression is a valuable new in vitro method for diagnosis of immediate type food sensitization. Although double-blind placebo-controlled food challenges remain the gold standard, the CD63-based BAT may supplement routine diagnostic tests such as SPT or allergen-specific IgE in the future.

Validation of a two-color flow cytometric assay detecting in vitro basophil activation for the diagnosis of IgE-mediated natural rubber latex allergy

BACKGROUND

IgE-dependent triggering of basophils not only elicits the release of different mediators but also the up-regulation of certain markers, e.g. CD63, which can be detected by flow cytometry. We intended to investigate if flow cytometric analysis of basophil activation could be a valuable tool in the diagnosis of latex allergy, and to evaluate if the basophil activation test (BAT) could be helpful in determining the clinical significance of a positive latex IgE in individuals with negative history and negative latex skin test. Additionally we aimed to determine the role of cross-reactive carbohydrate determinants (CCDs) in causing positive latex IgE without apparent clinical significance.

METHODS

Twelve healthy controls without a history of latex hypersensitivity with a negative latex IgE and skin test (group 1), 24 individuals without a history of latex hypersensitivity with a negative latex IgE and skin test but with other inhalant allergies (group 2), and 29 latex allergic patients with a compelling history of latex allergy with a positive latex IgE and prick test (group 3) were enrolled. The diagnostic performances of the BAT were further evaluated in 13 individuals with a history of latex allergy but with negative specific IgE and/or skin test (group 4). Twenty-four individuals with positive latex IgE without apparent clinical relevance, i.e. without history of latex hypersensitivity and negative latex skin tests, were also analyzed (group 5). The putative role of CCDs causing positive latex IgE results without apparent clinical significance was evaluated by quantification of IgE for bromelain.

RESULTS

According, to the receiver operating characteristics(ROC)-generated threshold value of 17% between latex allergic patients and the pooled group of nonlatex allergic individuals, the sensitivity and specificity of the basophil activation test was 93.1% and 91.7%, respectively. In healthy controls, allergic patients without latex hypersensitivity and latex allergic patients the number of positive BATs was 0/12, 3/24 and 27/29, respectively. In the individuals with an evocative history of latex allergy but with negative latex IgE and/or skin test the BAT was positive in all 13 cases. Twenty of 24 individuals without apparent latex allergy but with positive latex IgE had a negative BAT. IgE for bromelain was positive in 1/19 sera from group 2, 1/24 sera from group 3, none of the 8 sera from group 4, but in 16/18 sera from group 5, respectively.

CONCLUSION

Flow cytometric analysis of activated basophils seems a highly sensitive and specific tool for diagnosing latex allergy. In addition, the technique might help to determine the clinical relevance of positive IgE quantification in the absence of overt latex allergy. CCDs of natural rubber latex allergens were confirmed to mimic latex sensitization.