The importance of EN ISO 15189 accreditation of allergen-specific IgE determination for reliable in vitro allergy diagnosis

BACKGROUND

Allergen-specific serum immunoglobulin E detection and quantification have become an important step in allergy diagnosis and follow-up. In line with the current trend of laboratory test accreditation to international standards, we set out to design and assess an accreditation procedure for allergen-specific serum IgE.

METHODS

Method validation according to the accreditation procedure under the EN ISO 15189 standard was carried out for allergen-specific immunoglobulin E determination using the fluoroimmunoenzymatic method ImmunoCAP(®) (ThermoFisher). Data were produced by 25 hospital laboratories in France. A total of 29 allergen specificities including mixes, extracts, and molecular allergens were assayed. Allergen-specific serum immunoglobulin E concentrations ranged from 0.1 to 100 kUA /l.

RESULTS

Repeatability, reproducibility, and accuracy results fulfilled method validation criteria for automated laboratory tests and proved similar irrespective of the allergen specificity, allergen-specific serum immunoglobulin E concentration, or individual laboratory.

CONCLUSION

Allergen-specific serum immunoglobulin E determination with the fluoroimmunoenzymatic method ImmunoCAP(®) is a highly repeatable, reproducible, and accurate method which may be considered as a single analyte assay in view of the EN ISO 15189 accreditation procedure.

Nonsteroidal anti-inflammatory drug hypersensitivity syndrome: a multicenter study. II. Basophil activation by nonsteroidal anti-inflammatory drugs and its impact on pathogenesis

BACKGROUND

Patients who are clinically hypersensitive to nonsteroidal anti-inflammatory drugs (NSAIDs) sometimes present basophil activation in vitro, and in 50% of cases a parallel response to release of sulfidoleukotrienes (cellular allergen stimulation test) is observed. These phenomena occur not only in clinically hypersensitive patients, but also in some healthy controls who tolerate NSAIDs.

MATERIAL AND METHODS

We studied 16 clinically hypersensitive patients, 22 controls tolerating NSAIDs, and 29 healthy blood donors (clinical NSAID status unknown) using 2 different basophil isolation techniques (buffy coat or plasma leukocytes).

RESULTS

In a population of 13 aspirin-tolerant healthy controls and 29 healthy blood donors, basophil activation with aspirin, diclofenac, and naproxen was analyzed at 4 different concentrations. The results in the 2 groups were quite similar in qualitative terms. Choosing a cutoff of 5% and a stimulation index >2, the proportion of positive results increased with the concentration. There were more positive results at all concentrations using the plasma leukocyte technique.

CONCLUSIONS

The most important finding of this study is that basophil activation by NSAIDs occurs not only in clinically hypersensitive patients but also, to a very variable extent and on an individual basis, in apparently normal healthy individuals who tolerate NSAIDs. The phenomenon is clearly dose-related, and hypersensitive patients seem to react to lower NSAID concentrations.

Nonsteroidal anti-inflammatory drug hypersensitivity syndrome. A multicenter study. I. Clinical findings and in vitro diagnosis

BACKGROUND

We present the results obtained from the largest series of in vitro diagnostic tests ever reported in patients with clinically validated hypersensitivity to acetylsalicylic acid (ASA)/nonsteroidal anti-inflammatory drugs (NSAID) compared with various categories of controls tolerating ASA/NSAIDs. This multicenter study, which was performed within the framework of the European Network for Drug Allergy (ENDA) group, showed that the basophil activation test (BAT), particularly when used with the 3 NSAIDs aspirin (ASA), diclofenac (DIC), and naproxen (NAP), allows us to confirm the diagnosis of NSAID hypersensitivity syndrome. The results of the cellular allergen stimulation test (CAST) frequently correlate with those of the BAT, although not always. An unexpected finding was that basophil activation by NSAIDs is not an all-or-nothing phenomenon restricted to clinically hypersensitive patients, but that it also occurs in a dose-related manner in some NSAID-tolerant control individuals.Therefore, NSAID hypersensitivity appears as a shift in the normal pharmacological response to NSAIDs. These findings allow us to formulate a new rational hypothesis about the mechanism of NSAID hypersensitivity syndrome, a mechanism that most authors continue to describe as "unknown."

METHODS

We enrolled 152 patients with a history of hypersensitivity to NSAIDs and 136 control participants in 11 different centers between spring 2003 and spring 2006. Flowcytometric BAT was performed.

RESULTS

The most noteworthy results of our study were that 57% of 140 patients presented very clear-cut positive BAT results to multiple NSAIDs, and 16% were entirely negative. In about 27% of cases, positive results were obtained with 1 or 2 concentrations of a single NSAID. There is clearly a correlation between the results of BAT and CAST.

CONCLUSIONS

BAT seems particularly indicated in patients with a clinical history of NSAID intolerance, and in whom a provocation test is not advisable for ethical, clinical, or other reasons. Clear-cut positive results can be considered as confirming a history of NSAID hypersensitivity, although negative results may not exclude it.

Diagnosis of immediate-type beta-lactam allergy in vitro by flow-cytometric basophil activation test and sulfidoleukotriene production: a multicenter study

INTRODUCTION

This multicenter study aimed to evaluate the diagnostic value of 2 cellular tests based on basophil reactivity--the basophil activation test (BAT, Flow-CAST) and the sulfidoleukotriene release assay (CAST-ELISA)--in immediate-type beta-lactam allergy, particularly in patients with a clinical history of allergy and a negative skin test result.

MATERIAL AND METHODS

In a multicenter study encompassing 10 European centers, 181 patients with a history of immediate-type beta-lactam allergy, and 81 controls, we evaluated the diagnostic efficiency of specific IgE determinations and of 2 cellular tests based on basophil reactivity, the BAT and the sulfidoleukotriene release assay.

RESULTS

With Flow-CAST, sensitivity varied for individual beta-lactam allergens from 16% for penicilloyl-polylysine to 33% for amoxicillin, reaching 50% when all 5 allergens were considered. In beta-lactam-allergic patients with negative skin test results (22.8%), Flow-CAST showed positive results for at least 1 of the 5 allergens in 37%. Specificity varied from 89% to 97%, depending on the allergens used. In CAST-ELISA, the overall sensitivity in skin test-positive patients was 41.7%; in patients with negative skin test results it was 27.9%. Both tests were not absolutely correlated, so that when all the results were considered together, sensitivity increased to 64.3% and specificity varied for both tests combined from 73% to 92%. In contrast, specific IgE determinations in the same population yielded a lower sensitivity (28.3%).

CONCLUSIONS

A diagnostic algorithm including skin tests and specific IgE, followed by cellular tests in negative patients and controlled challenge enabled us to confirm beta-lactam allergy in 92% of cases. This procedure would also allow us to avoid two-thirds of the required controlled challenges.

Use of both CD63 up regulation and IgE down regulation for the flow cytometric analysis of allergen induced basophil activation. Definition of an activation index

OBJECTIVE AND DESIGN

The aim of this study was to compare the use of a late (CD63) and an early (IgE) marker of basophil activation in the flow cytometric diagnosis of beta-lactam induced allergic hypersensitivity reactions.

SUBJECTS

Twelve patients who had had a clear cut betalactam induced immediate reaction and 16 controls were selected, as well as 11 patients who had had an immediate reaction to bee or wasp stings.

METHODS

Leukocyte suspensions were incubated with allergen dilutions as well as 2 positive controls (anti-IgE and NFormyl- Methionyl-Leucyl-Phenylalanine (fMLP)). Basophils were labelled with an anti-IgE FITC (fluorescein isothiocyanate) and an anti-CD63 PE (phycoerythrin). Results were expressed as percentage CD63 expression and index calculated according to a specific algorithm including the two activation markers.

RESULTS

Significant CD63 expression (>5 %) was observed in 3/12 cases for the beta-lactam sensitized population, in 0/16 cases for the controls and in 11/11 cases for the venom sensitized population. A significant index (determined by a ROC analysis) was observed in 11/12 beta-lactam sensitized patients and in 0/16 controls.

CONCLUSION

These results show that IgE (an early activation marker) is more sensitive than CD63 (a later activation marker) in the diagnosis of beta-lactam allergy.

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.

Improvement of flow cytometric analysis of basophil activation inhibition by high histamine dilutions. A novel basophil specific marker: CD 203c

BACKGROUND

Histamine is known to elicit a negative feedback effect on anti-IgE and allergen-induced basophil activation. A series of experiments performed between 1981 and 1995 using a manual method showed biological activity of highly diluted histamine. Most of the experiments used histamine in the range 10(-30) (15C)-10(-36) M (18C). These results were confirmed by automated flow cytometry, but this method is based on the selection of basophils by anti-IgE and analysis of basophil activation by anti-CD 63, showing significant but relatively low inhibition (approximately 14%), insufficient to convince the scientific community of the reality of the phenomenon.

OBJECTIVE

We investigated if the use of CD 203c, a basophil specific, earlier marker than CD 63 of the activation cascade, increased the sensitivity of the method, testing two target histamine dilutions, 10(-4) (2C) and 10(-32) M (16C).

METHODS

Basophils, obtained from buffy coats, were pre-incubated with the histamine dilutions and activated by two agonists: anti-IgE and fMLP (formyl-methionyl-leucyl-phenylalanine peptide). Basophil activation was stopped with EDTA. The cells were labelled with anti-IgE, anti-CD 13 and anti-CD 14 for basophil selection, and anti-CD 63 and anti-CD 203c for basophil activation. Results were expressed in up-regulation percentage for CD 63 or mean intensity of fluorescence (MFI) for CD 203c.

RESULTS

Histamine 10(-4) M (2C) and histamine 10(-32) M (16C) were capable of inhibiting both IgE-dependent (anti-IgE) and IgE-independent (fMLP) basophil activation. The percentage inhibition depended on the activation marker used. The highest inhibition for histamine dilution 16C was observed with CD 203c (38%, P<0.001), approximately half the inhibition observed with histamine 2C (73%).

CONCLUSION

These new flow cytometric protocols confirmed that high dilutions of histamine may inhibit basophil activation and that the inhibitory effect is not restricted to IgE-dependent activation. The use of CD 203c instead of CD 63 increased the magnitude of the response.

Allergy to nickel in dental alloys

A case of oral allergy to dental alloys is presented, highlighting the interest of dosage of salivary nickel and of flow cytometry showing a selective CD4+ activation. The discrepancy between the rarity of oral allergy to dental alloys and the frequency of nickel sensitization and nickel-induced contact dermatitis leads to discuss the mechanisms of oral tolerance.

Histamine dilutions modulate basophil activation

BACKGROUND

In order to demonstrate that high dilutions of histamine are able to inhibit basophil activation in a reproducible fashion, several techniques were used in different research laboratories.

OBJECTIVE

The aim of the study was to investigate the action of histamine dilutions on basophil activation.

METHODS

Basophil activation was assessed by alcian blue staining, measurement of histamine release and CD63 expression. Study 1 used a blinded multi-centre approach in 4 centres. Study 2, related to the confirmation of the multi-centre study by flow cytometry, was performed independently in 3 laboratories. Study 3 examined the histamine release (one laboratory) and the activity of H(2) receptor antagonists and structural analogues (two laboratories).

RESULTS

High dilutions of histamine (10(-30)-10(-38) M) influence the activation of human basophils measured by alcian blue staining. The degree of inhibition depends on the initial level of anti-IgE induced stimulation, with the greatest inhibitory effects seen at lower levels of stimulation. This multicentre study was confirmed in the three laboratories by using flow cytometry and in one laboratory by histamine release. Inhibition of CD63 expression by histamine high dilutions was reversed by cimetidine (effect observed in two laboratories) and not by ranitidine (one laboratory). Histidine tested in parallel with histamine showed no activity on this model.

CONCLUSIONS

In 3 different types of experiment, it has been shown that high dilutions of histamine may indeed exert an effect on basophil activity. This activity observed by staining basophils with alcian blue was confirmed by flow cytometry. Inhibition by histamine was reversed by anti-H2 and was not observed with histidine these results being in favour of the specificity of this effect We are however unable to explain our findings and are reporting them to encourage others to investigate this phenomenon.

[Specific antibodies to iodinated contrast media. Research techniques, specificity]

Immuno-allergology of iodine contrast products is much discussed, the main questions posed by these molecules particularly concern the existence of specific IgE and their frequency, the specificity of the antibodies, involvement of the iodine atoms and their routes of sensitisation. Our preliminary study on 6 cases of urticaria (5) and erythema (1) after use of ioxaglate and with positive search for ioxaglate-specific IgE (2.3 to 6.7) after coupling to Sepharose (Baldo and Fisher technique). The results of this technique are expressed with reference to a pool of serum of subjects who had no contact with these contrast products. The threshold of positivity was 2, the mean of the results from 10 subjects who were exposed lay between 1.37 +/- 0.42. Inhibition of specific IgE by ioxaglate was positive in 6 cases. In 2/3 cases inhibition by potassium iodide was also observed. Several published studies in favour of the existence of specific IgE of close specificity, the inhibitions of specific IgE presented were mostly only observed for the contrast product used. An hypothesis would be that the ionic molecules have a greater capacity to induce the synthesis of specific IgE than non-ionic molecules because of their affinity for carrier proteins. The inhibitions seen with mineral iodine in this short study do not permit total elimination of the participation of the iodine atom at the antigenic site.

[Acetylsalicylic acid: hypersensitivity, intolerance, or allergy?]

After a century of therapeutic use of acetyl salicylic acid (ASA), the different mechanisms involved leading to the therapeutic activity and to the various clinical reactions (even life threatening) observed in patients sensitive to ASA or in general to the non steroidal anti-inflammatory drugs (NSAID's) are still to be discovered or confirmed. During the last century a lot of scientific results have been published in favour of a wide panel of mechanism including an humoral (IgE and/or IgG) or a cellular (lymphocytes) immune reaction, inhibition of the cyclooxygenases, a cellular activation (mast cells, basophils, eosinophils and platelets), a competition at the serum albumin level and an activation of the complement cascade. In general the same actors than in the anaphylactic reaction are found (mediators, cellular activation and amplification systems). It is clear today that these reactions for which an accurate diagnosis is mandatory cannot be explained by a single mechanism, which is the case of a lot of other allergens.

Diagnosis of venom allergy by flow cytometry. Correlation with clinical history, skin tests, specific IgE, histamine and leukotriene C4 release

BACKGROUND

Potent allergens such as hymenoptera venoms are capable of inducing severe and life threatening clinical reactions. Percentage of false negative results obtained by the usual diagnostical methods is comprised between 10 and 25%.

OBJECTIVE

Evaluation of the sensitivity and the specificity of cellular tests and particularly evaluation of a new flow cytometric method.

METHODS

Forty-five allergic patients having experienced a local, a systemic reaction or an anaphylactic shock and 10 controls having undergone hymenoptera stings without clinical reactions were selected on the basis of the clinical history, skin tests and specific IgE. Three cellular tests were performed on the same cell suspensions and in the presence of 2 ng/mL of rIL3: histamine release (RIA), leukotriene C4 release (ELISA) and basophil activation test (flow cytometry after double anti-IgE FITC, anti-CD63 PE labelling).

RESULTS

As compared to the clinical history, sensitivities of skin tests, specific IgE, flow cytometry, histamine release and leukotriene release were, respectively; 85%, 88%, 100%, 89% and 100%. Flow cytometric analysis of basophil activation showed a significant decrease of the mean fluorescence density and number of IgE positive cells and a significant increase of the number of CD63 positive cells. The 10 controls tested by flow cytometry were negative.

CONCLUSION

As compared to the clinical history and to the other parameters tested here, flow cytometry showed a high sensitivity and a high specificity. The excellent correlation observed between this method and the other cellular tests such as histamine and leukotriene release are in favour of the specificity of flow cytomery and in favour of the use of this method for venom allergy diagnosis.

[Importance of blood tests for the diagnosis of drug allergies]

This work is devoted to the study of 22 dossiers of persons who have presented with clinical signs following taking a drug. The study was confined to patients in whom the symptoms had as origin a hypersensitivity (true or non-specific by histamine release). This study has allowed analysis of the value of several serological tests (measurement of leukotrienes, activation of basophils and T specific lymphocytes) in diagnosis and so to define the path to take that is best adapted to each case. The conclusion presents an agreement between the suspected diagnosis, after allergy enquiry and prick-tests, and the results of serological tests.

Anaphylactoid and anaphylactic reactions to iodinated contrast material

Some adverse reactions to iodinated contrast material (ICM) are considered allergy-like, with cutaneous, cardiovascular, respiratory, and digestive symptoms. Allergy-like reactions are usually unpredictable. Reactions are more frequent with ionic than with nonionic material, but the frequency of deaths is almost identical. In a recent study, 20 severe unexpected reactions to ICM, including 10 life-threatening reactions and one death, were investigated by measuring mediators in blood, within the first minutes or hours of reaction. The responsible ICMs were mostly ionic materials. Histamine and tryptase release correlated with the severity of the reaction. Specific IgE against the responsible ICM was significantly higher in reactors than in controls. A few patients had positive skin tests to the administered ICM, suggesting type-I allergic reaction. Only 2.4% and 3.1% of the cases yielded a positive IgE-RIA, in a second retrospective study which included 165 patients recruited during a 4-year period. In conclusion, IgE-mediated anaphylaxis is rare, but it may be one of the possible mechanisms of severe adverse reactions to ICM.

[Evaluation of allergic-type reactions to antibiotics and rapid immunotherapy]

Adverse effects of medications, most notably antimicrobials, are becoming increasingly common and raise difficult challenges in the area of clinical pattern definition (wide variety of symptoms, polypharmacy in many cases), diagnosis, and methodology (need for a rapid diagnosis, frequent obscurity of causative mechanisms, and less than ideal reliability of laboratory techniques). Sixty patients were treated by rush immunotherapy to one or more antimicrobials. The pretreatment evaluation included oriented history taking, skin tests, blood cell counts, IgE assays, and cell activation tests (basophils and lymphocytes). The results of this study confirm the usefulness of skin tests (intradermal, prick, or patch tests), which provided etiological orientation in 54 of the 60 cases. They also provide additional evidence of the lack of reliability of currently available in vitro tests (only 29 of the 60 tests were positive).

[Biological assays in allergology: constraints, concepts, criteria, and methods of evaluation]

The in vitro diagnosis of allergies is submitted to several constraints some shared by all the in vitro methods and some which are specific of immuno-allergology. The in vitro diagnosis of allergies involves various parameters among which the allergen by itself is far the most complex. On the basis of a studied population having an optimal size, the most powerful statistical parameters are the positive predictive value, the negative predictive value and the efficiency. The bio-clinical correlations lead to the involvement of another parameter which is the prevalence of the clinical reaction which may be corrected by a clear clinical history. Finally, the absence of absolute gold standard in allergology lead to the conclusion that allergy diagnosis is still based on the synthesis of various clinical and biological arguments.

Human basophil activation measured by CD63 expression and LTC4 release in IgE-mediated food allergy

BACKGROUND

IgE-dependent basophil activation induced by an allergen elicit the release of LTC4 and the expression of the CD63 membrane marker.

OBJECTIVE

The aim of this study was to check if flow cytometric analysis of basophil activation could be applied to food allergy diagnosis and if this method paralleled LTC4 release.

METHODS

Patients were selected by the clinical history, skin tests, and provocation tests. Basophil activation induced by food extracts was studied in 24 control subjects and in 27 patients having a food allergy by LTC4 release test (LRT) and by flow cytometric anti-IgE+, CD63 + cell counting (BAT = basophil activation test). In case of negative anti-IgE response a passive blood donor basophil passive sensitization step was added to LRT and BAT. Leucocyte histamine release test was performed in 11 patients.

RESULTS

Basophil activation test was positive in 18/31 cases and LRT in 22/34 cases for food-allergic patients and, respectively, in 1/33 and 1/35 cases for the controls. A correlation was observed between specific IgE, BAT, and LRT. Basophil activation test and LRT performed after passive sensitization had an excellent sensitivity only for specific IgE levels ranging between 3.5 and 35 KU/L.

CONCLUSION

The present study shows that allergen-induced LTC4 release and anti-IgE, antiCD63 bicolor flow cytometric analysis of basophil activation may be used for food allergy diagnosis. Both tests have a good sensitivity and specificity. Basophil activation test and LRT are more efficient than histamine release test in case of high spontaneous histamine release, frequently observed in case of food allergy.

Analysis of anti-IgE and allergen induced human basophil activation by flow cytometry. Comparison with histamine release

OBJECTIVE AND DESIGN

On the basis of flow cytometric methods previously described for the analysis of human basophil activation, we present here a bi-color anti-IgE FITC, anti CD63 PE method and the correlation with histamine release.

MATERIALS AND SUBJECTS

Subjects allergic to grass pollen were selected by their clinical history, skin tests and specific IgE.

METHODS

Basophils gated in the lymphocyte region of the side scatter (SSC)/forward scatter (FSC) pattern were selected by their high IgE epitope density. Percentage of cells expressing CD63 marker, upregulated on activated basophil membrane, was calculated by the cytometer. Histamine released into the supernatants was measured by RIA.

RESULTS

In these conditions, flow cytometric analysis of blood leukocytes showed that the selected cells had the phenotype CD14-, CD19-, CD45+, IgE++ and CD63- or + which is related to human basophil phenotype, the isotype controls being negative. The use of an anti-CD41 FITC antibody also showed the presence of aggregated platelets on the basophil membrane, CD63 antigen being, however, expressed by basophils themselves and not by platelets. Moreover, no statistical difference was observed between histamine release and flow cytometry after passive sensitization of blood donor leukocytes.

CONCLUSION

Flow cytometry, as a popular method often used in the immunology and haematology departments of clinical laboratories may represent a new alternative for allergy diagnosis and basophil pharmacology.

[Comparison of the levels of histamine, tryptase, and interleukin-6 for the investigation of anaphylactoid drug reactions]

The biological exploration of the anaphylactoid reaction is based on tryptase and plasma histamine determinations. As this reaction may be considered as a particular case of the acute inflammatory reaction, we have compared, on 25 subjects having presented a drug induces anaphylactoid reaction grade 1 to 3 the plasma level of tryptase, histamine and interleukin 6 (IL6) at 30 and 90 min. On a population of patients having presented an increase of plasma histamine and/or tryptase (n = 14), we have shown that the concentrations of tryptase, histamine and IL6 respectively plateaued (63.9 +/- 70 micrograms/l et 74 +/- 102 micrograms/l), decreased (82.5 +/- 102 mmole/l et 20.5 +/- 27 mmole/l), or greatly increased (19.5 +/- 25.3 ng/l et 320 +/- 745 ng/l) at 30 and 90 min. Correlation between IL6 and the two parameters was only significant for tryptase at 30 and 90 min. Due to the longer lasting kinetic of IL6 (48 h) as compared to histamine and tryptase, IL6 could have a place in the immediate exploration of the anaphylactoid reactions, these results having to be completed by studies on a longer delay and on groups of well defined clinical reactions.

[Allergic immunobiology and anesthesiology]

A protocol has been produced for the study of anaphylactic accidents that occur post-operatively that allows definition of the anaphylactic origin, and so reactions that are mediated by IgE in post-operative accidents. This protocol occurs in two stages, the first is done in the minutes and hours that follow the anaphylactic accident, and the second a month or 6 weeks afterwards. At first, we evaluate the sequential study of the liberation of the mediators of anaphylaxis, plasma histamine, serum tryptase, urinary methylhistamine and, more recently, leucotriene E4. The second study is devoted to reactions that are mediated by IgE, essentially, specific serum IgE, tests of activation of basophils by flow cytometry, measurement of leucotriene C4 and skin tests. A study on 16 subjects has evaluated and validated the protocol and shown a significant level of correspondence of results between the sequential measurement of mediators on one hand and on the other the search for IgE-mediated reactions every time that there was an anaphylactic reaction.

[Application of flow cytometry to the analysis of activation of human basophils. Immunologic validation of the method]

Among the different methods used for the analysis of human basophil activation as histamine and leukotriene release, flow cytometry presents several methodological advantages. Moreover, preliminary results obtained for a wide allergen panel have demonstrated its high sensitivity and specificity. We present here the results of the methods used to validate the flow cytometric analysis of human basophil activation by double anti-IgE FITC/anti-CD63 PE labelling of human leucocytes. The use of multiple labelling by monoclonals having different specificities have shown that the selected cells express the phenotype CD14-, CD19-, CD41- or +/-, CD45+, CD63- or +. This phenotype is related to human basophils. We have also demonstrated that the expression of CD63 is related to basophil activation and not to aggregated platelets which are also able to express this marker.

[Testing basophil activation by flow cytometry in the diagnosis of allergy to hymenopteran venom]

Diagnosis of allergy to hymenoptera venom must be precise and depends on indisputable bio-clinical criteria, because of specific immunotherapy for indications such as systemic and/or anaphylactic reactions. Until nowadays, diagnosis was by specific IgE, histamine release and skin tests, most often done for the venoms of wasp, honey bee and hornet at the same time since, in 7-8 cases in 10 the patients had not identified the responsible insect. Basophil activation test (TAB) by Flux cytometry and measurement of leukotriene C4 (LTC4) are new techniques of great reliability. The work shows the correlations between the different immunobiological parameters by reference to TAB by CAF and measurement of LTC4. When the overall results for mixed venoms or those for single venoms are considered, the correlations between TAB, LTC4 and the other parameters are highly significant. It can now be considered objectively that TAB by CTF and measurement of LCT4 are the two highest-performing techniques for diagnosis of hymenoptera venom allergy and so validates them.

Recognition of an extensive range of IgE-reactive proteins in cod extract

Allergy to fish is one of the most common food allergies. Gad c 1 is the only fish allergen which has been purified and characterized. Other allergens have been detected by Western blot in cod extracts. We have now improved the Western-blot procedure in order to characterize fish IgE-reactive proteins from extracts prepared under different conditions: pre-rigor mortis and post-rigor mortis, EDTA addition or not, and DEAE ion-exchange chromatography. Several IgE-reactive protein bands have been identified over a wide molecular-weight range. In particular, the 104- and 130-kDa IgE-reactive protein bands were detected. These new bands may correspond to aggregates, as EDTA increased the relative amount of the 60-, 67-, 104-, and 130-kDa IgE-reactive protein bands in Western blot. All these bands were also detected by antiparvalbumin monoclonal antibody, specific to the first calcium-binding site. The longer period of storage increased the relative amounts of the 41-, 80-, 104-, and 130-kDa IgE-reactive protein bands. The 18-kDa band was detected only in fish stored for several days. In conclusion, we have described IgE-reactive protein bands over a wide molecular-weight range (12-130 kDa) in Western blot of cod extract, and shown that EDTA and storage conditions may influence the relative distribution of IgE-reactive protein bands.

[Diagnostic contribution of abnormal delayed-type hypersensitivity to Candida albicans. Characterization test by activation of cells sensitized to successive dilutions of Candida]

By measuring the activation of different cell models (lymphocytes and lymphocytic subsets) in the presence of Candida albicans with flow cytometry reading, it is possible to show that successive dilutions of Candida albicans can lead to lymphocyte activation in abnormally-sensitized subjects. In a first trial, 10 subjects were tested in duplicate. The decrease of activity of the dilutions does not appear to be regular in relation to the progression of the dilutions. The activity of the dilutions wanes relatively rapidly with the first dilutions, then recurs later very distinctly, at the 6th dilution, then ebbs, then reappears in similar manner at the 9th, the 14th, and finally, the 19th dilution. Cell reactivity appears to differ depending on the subject. It can be represented through the calculated slope of the regression line, for each series of data. It therefore appears feasible to determine a threshold of reactivity and a scale of sensitivity, to make it possible to specify the degree of abnormal reactivity existing at a given time for a given subject. The constancy of the activity of the different dilutions tested, on 10 cultures of a single cell suspension, is especially well demonstrated in the second trial, showing unusually small standard deviations. Thus, the question arises as to the exact nature of the observed phenomenon and of its analysis from a physical-chemical point of view, with regard to the pharmacological effect of successive dilutions of Candida albicans.

[Immuno-biological diagnosis of food allergy]

Food allergy is becoming more frequent, with 6% of asthmatics reporting an isolated food allergy, and 5 to 6% of atopic dermatitis patients also have either a single or multiple true food allergy. There is value in immuno-biological diagnosis by: Measurement of total serum IgE. Measurement of mono-allergen-specific IgE, following a measurement by a multi-allergen of the Trophatope type. A study of elimination of foods for 2 or 3 months followed by their re-introduction. Oral provocation tests in a hospital environment under clinical control and subsequent measurement of the mediators:-Plasma histamine, tryptase, and urinary methylhistamine to give proof of responsibility of the food allergen. Nowadays, it is perfectly possible to include in diagnosis the new technologies of the test of activation of basophils/or lymphocytes by means of flow cytometry.