Molecular allergology in practice: an unusual case of LTP allergy

The authors describe an unusual case of LTP allergy. A 35 years old patient presented repeated episodes of angiooedema after food intake and complained 10 years ago of contact urticaria and rhinoconjunctivitis when exposed to cannabis leaves and to marijuana smoke. The suspected responsible foods, such as wheat flour in bread, are known to contain LTR Oral syndrome occurred after ingestion of walnuts. Cutaneous tests confirmed immediate responses to several flours and nuts and also to cannabis leaf and flower. A few months later he had similar accidents following peach ingestion and drinking of beer and several wines which all induced positive skin tests. Serological investigations using ImmunoCAP and ISAC microarray confirmed IgE positivity for n Pru p3, r Cor a 8 and n Art v3. It was assumed that sensitization to LTP, the major allergen of cannabis, was responsible of the primary sensitization and induced further LTP food allergies.

Mite allergens: an overview

Mite allergens from the Pyroglyphidae family are the most frequent and potent sources of perennial asthma and rhinitis. Since 1988 molecular knowledge has considerably increased and structures and functions have been determined for most of them. Of the 22 denominated allergens, Der p 1 and Der p 2 are major allergens recognized by more than 80% of lgE from Dpt allergic patients in Europe. Der p 4, Der p 5 and Der p 7 appeared to be intermediate allergens. The binding of IgE to groups 3, 6, 8, 9, 10 and 20 is constantly low. Most of the allergens can be identified by amino-acid sequences and the tertiary structure of the major allergens has been solved. Most Dpt mite allergens are proteolytic enzymes: Der p 1 for instance is a cysteine protease. Der p 2 has structural homology with MD-2, a co-receptor of the Toll-like receptor (TLR4) whose ligand is LPS. Knowledge of the mite allergens structure has allowed a better interpretation of cross reactions between allergens from the same family or from more distant families. From a practical point of view molecular epidemiology has allowed a better choice of allergen molecules useful for diagnosis. Finally, new concepts of immunotherapy based on genetically engineered hypoallergenic variants of major allergens, used alone or in combination, can be considered.

Tropomyosin or not tropomyosin, what is the relevant allergen in house dust mite and snail cross allergies?

Since tropomyosin is cross reactive in many arthropods, it was assumed that this highly conserved protein could be responsible for cross reactions in house dust mite (HDM) allergic patients who experienced adverse reactions after crustacean and mollusc ingestion. Here we report two clinical cases where the role of tropomyosin is a matter of debate. In the first case, the clinical history, as well as the results of in vivo and in vitro investigations, are in favour of a shrimp allergy without any snail allergy in a patient sensitized to HDM. In the second, the clinical history and the cutaneous tests are in favour of an allergy to snails without any allergy to shrimps in a patient suffering from HDM allergies. The clinical presentation is different in shrimp and snail allergies. In shrimp allergy, symptoms are mainly urticaria or angio-oedema. In snail allergies, adverse reactions are especially severe asthma. Shrimp tropomyosin is a dominant allergen in crustaceans whereas has a much less prominent role in HDM sensitization. Cross reactivities between HDM and snails have been confirmed by inhibition experiments. However, tropomyosin appears to be a minor allergen or even is not involved in snail allergy. It is necessary to clarify the allergens shared between HDMI and snails. The effects of HDM immunotherapy in snail allergy are questioned. Knowledge of taxonomy can contribute to more precise evaluation of cross reactivities between crustaceans and molluscs.

Rare indoor allergens

Rare allergens in indoor environment are insufficiently recognized. The sources are diverse: they include animal, namely acaride, insect and mammalian allergens or vegetable allergens. The prevalence of sensitization to rare allergens depends on geographical and climatological characteristics, on people's habits and overall on dwelling specificities. Sensitizations to new rare allergens should be confirmed by documented clinical history, by immunological tests, and by the beneficial effects of avoidance. A review of rare and/or new allergens likely to be present in indoor environment is presented.

[Mites and their allergens: identification and extermination methods]

Mite allergens are the main allergens in indoor environment. Using different means of assessing exposure to house dust mites (Acarex-test, major allergen (Der p 1 + Der f 1, Der p 2 + Der f 2), content measured by ELISA) has allowed better identification of mite reservoirs and allergens in patients' homes. House dust mite control measures are based on the knowledge of factors contributing to mite development, especially indoor relative humidity. Mite allergen avoidance strategies include 3 different methods: avoidance of mite producing allergens, elimination of mite reservoirs, especially textile reservoirs, dwellings designed so as to inhibit mite proliferation. Only controlled trials can estimate patients' compliance with proposed avoidance measures. Avoidance protocols should be adjusted to each individual by medical indoor environment counselors in order to optimize mite allergen reduction.

Urticaria and rhinitis to shrubs of Ficus benjamina and breadfruit in a banana-allergic road worker: evidence for a cross-sensitization between Moracea, banana and latex

BACKGROUND

We report the case of a road worker with a food allergy to banana, who developed urticaria and rhinitis when cutting shrubs of Ficus benjamina and breadfruit. He did not develop an allergy to latex of Hevea brasiliensis.

RESULTS

Sensitization to latex of F. benjamina, H. brasiliensis, breadfruit and banana was demonstrated using skin tests and specific IgE measurements. RAST inhibitions procedures showed that specific IgE to breadfruit latex cross-reacted more strongly with latex of H. brasiliensis and banana than with latex of F. benjamina with the same extract.

CONCLUSION

Given the wide distribution of Moracea trees in tropical regions, sensitization to latex of H. brasiliensis and banana could be a consequence of sensitization to Moracea members; F. benjamina does not seem to be the only Moracea responsible for cross-allergy with latex and fruit. Consequently, it seems interesting to test other members of the Moracea family in patients sensitized to latex of H. brasiliensis and banana. Sensitization to breadfruit could be a risk factor for sensitization to latex of H. brasiliensis.

[Physiopathology of hay fever]

Pollinosis is a model physio-pathology for IgE-dependent diseases. Rhinitis and conjunctivitis are the parent symptoms, with asthma a non-exceptional complication. The mechanisms are linked to an immuno-allergic inflammation; the observed differences are due to specific anatomo-physiologies of the sensitive cells. The pollen allergens are collected by the CPA and expressed after cleavage into peptides, at the surface of the CPA in association with class II HLA molecules. T-lymphocytes recognise the complex HLA-peptide molecules. Type Th2 lymphocytes produce the cytokines that the necessary for the synthesis of IgE (IL4, IL13...). At the stage of silent clinical sensitivity the precocious and delayed effector stages of immediate hypersensitivity follow. The precocious stage corresponds with degranulation of cells that express Fc epsilon R1, for release of vaso-active and lipid mediators that produce the immediate symptoms of pollinosis. The delayed phase corresponds with a flood of eosinophils, which release their toxic proteins proteins and also take part in oedema and nasal obstruction. Mucosal innervation, neurotransmitters and neuromediators also intervene in the modulation of symptoms.

[Respiratory allergies and household allergenic environment]

Based on immunoassay techniques used to identify and quantify major indoor allergens, epidemiological studies have demonstrated that level of exposure depends on the geographical situation (climate, urbanization) and that there is a relationship between exposure and sensitization of predisposed patients. Most of the major mite allergens are proteases. For mammals and cockroaches, the major allergens belong to the retinal protein binding group. Determination of the airborne characteristics of the major indoor allergens is helpful in better understanding the pathophysiology of asthma. In the future, more precise diagnosis and more efficient immunotherapy will be possible through the development of recombinant allergens. The efficacy of allergen avoidance in allergic asthma has been demonstrated in several studies. Thus the respective role of different household allergens should lead to improved diagnosis and treatment of allergic diseases.

[Exploration of respiratory allergies and prevention]

Respiratory allergies are found in more than 50% of the asthmatics. Allergen sources and their secondary reservoirs are better known. The different methods of exploration of allergic asthma consist of clinical history, skin tests, and in vitro tests particularly measurement of specific serum IgE. Specific challenge tests are realized with nebulized allergenic extracts as well as in the realistic manner with substances in occupational environment. It is equally important to evaluate the allergenic environment, especially by simple but informative techniques such as the Acarex test for mites. The eviction methods are the same for primary prevention (to prevent sensitization) as well as for the secondary prevention (to reduce the disease exacerbation in the patients already sensitized). The eviction methods mainly concern the allergens of mites, domestic animals, cockroaches and the molds.

Genetics and specific immune response in allergy to birch pollen and food: evidence of a strong, positive association between atopy and the HLA class II allele HLA-DR7

BACKGROUND

In some geographic areas birch pollen represents the most prominent cause for airborne allergic diseases. Up to 70% of patients allergic to birch pollen are hypersensitive to fruits, especially apples. Associations have been found, in some instances, with a sensitivity to aeroallergens and HLA class II genes.

OBJECTIVES

We investigated whether susceptibility or resistance to birch pollen allergy with and without food allergy was associated with HLA class II genes.

METHODS

Blood samples were obtained from 2 groups of unrelated European-born white adults: 42 atopic patients (31 of them with asthma) and 42 healthy control subjects with no personal or familial history of asthma or atopy. Their antibody responses to birch pollen, apples, grass, and weed pollens were evaluated by skin tests, RASTs, and immunoprints. Genomic DNA was extracted from PBLs. The exons of DQA1, DQB1, DRB1, and DPB1 genes were selectively amplified by using the PCR method. Genotyping was carried out by digestion of the amplified DNA products with allele-specific endonucleases (PCR-RFLP), which recognize allelic variations in the polymorphic exon.

RESULTS

We found no significant differences in the frequency of DPB1 alleles between patients and control subjects. HLA class II DR4 and/or DR7 alleles were present in 42.6% of the patients and in only 2.4% of the healthy subjects. These results confirm a previous study of a group of polysensitized atopic patients, which showed that DR4 and DR7 alleles were rare in healthy control subjects and frequently observed in atopic subjects with or without concomitant asthma.

CONCLUSION

We conclude that the allele HLA-DR7 is significantly involved in the presentation of apple and pollen allergens. However, we suggest that this susceptibility is more related to atopy than to specific responses to allergens.

[Occupational asthma caused by a coloring reagent]

A case of occupational asthma associated with rhinitis and conjunctivitis occurred in a patient working in a textile factory and exposed to different coloring reagents is reported. Symptoms appeared in phases correlated with changes in the use of the coloring reagents. Prick tests were carried out with the different coloring reagents and were positive for the yellow color. The test was followed by a clear increase in bronchial hyperreactivity to methacholine. Some individual preventive measures, such as wearing a face mask, led to reduction then disappearence of the symptoms.

[Occupational asthma]

Occupational asthma is specifically induced by repeated exposure to substances in the work place. Diagnosis requires using the results of numerous tests, and a challenge test is the most appropriate to establish the diagnosis of occupational asthma due to chemical agents. Agents responsible for occupational asthma may be of animal or vegetable origin, or may be chemical agents. The pathophysiological mechanisms of occupational asthma are not well known. It is probable that immunologic mechanisms play an important role, in particular in occupational asthma due to glycoproteins. An important feature of occupational asthma is the relationship to chemical substances, for which the mechanisms are often still hypothetical. From the legal viewpoint, a recent law holds the promise of better compensation for those who are afflicted.

[Pollen environment and its evaluation]

We review the methods available for determining airborne pollen. In addition to the classical gravimetric and volumetric methods, new immunochemical techniques are also used for detecting allergenic pollen and measuring of the size of allergen-carrying particles. Pollen counts are available in France for 39 urban sites. In the last decade changes in the pollen environment have basically concerned higher counts from resinous trees in southern France and birch tree counts in northern France as well as a lesser role for ash trees. Among the recent acquisitions, it has been demonstrated that allergens are present in twigs and leaves, or even the bark of certain trees. Interactions with atmospheric pollution is better understood and could be a contributing factor to the increasing number of people allergic to pollen. Pollen allergens can be carried on particles of various sizes and immunochemical studies have demonstrated that gramineous pollen allergens can be carried on starch particles less than 3 mu in diameter. These recent studies would explain the apparent disagreement between pollen counts and the number of clinical manifestations.

[Asthma, rhinitis and urticaria following occupational exposure to cyanoacrylate glues]

Cyanoacrylate glues are more and widely used in the industry because of easy handling and great sticking power. These very volatile and chemically reactive glues may not only cause contact eczema, but also rhinitis and asthma. Nineteen cases of asthma have been reported to date. We report two new cases of occupational asthma as well as one case of urticaria, a clinical symptom not yet described, to our knowledge. In the three cases, diagnosis was made based on a compatible medical history and positive realistic exposure tests. The mechanism is still unknown, due to the physical properties of cyanoacrylate glues; in fact, it is not possible to perform prick tests or specific IgE measurements. Besides the usual preventive measures, maintaining a relative humidity greater than 55% seems to induce polymerization of free monomers of alkyl cyanoacrylate, thereby reducing their volatility. Rhinitis and asthma due to cyanoacrylate glue may receive compensation as occupational diseases in France.

[Occupational asthma in an agricultural setting]

The prevalence of asthma in a farming environment is significant (from 3-7.7% according to various studies). The clinical picture has not been specified. The responsible agents are multiple and polysensitization frequent. Numerous substances of vegetable origin may be a cause, pollens, moulds, cereals, oil and protein producing plants, fibrous textiles, diverse plants and wood, etc. Amongst substances of animal origin the most frequent allergens incriminated are: allergens from mammals (horses, cattle, pigs), allergens from chickens and birds, arthropod allergens, insect allergens. Amongst chemical products those which are at risk to the respiratory system include insecticides, herbicides, fungicides, antibiotics and antiparasites. The diagnosis of the occupational character of asthma is sometimes difficult because of other causes of lung diseases in farm workers. The aetiological diagnosis is achieved by the clinical history, cutaneous tests, a level of specific serum IgE, and bronchial provocation tests which contrary to asthma in the industrial environment are not fundamental to the diagnosis except where chemical products are suspected. The mechanisms are sometimes intricate (IgE dependant mechanisms, non-specific liberation of histamine, activation of complement, intervention of endotoxins and pharmacological mechanisms...). Prevention may be carried out on behalf of the victim (for example wearing filtration masks in dusty work) and also carry out various methods to reduce the level of exposure to the allergen.

Skin testing with recombinant allergens rBet v 1 and birch profilin, rBet v 2: diagnostic value for birch pollen and associated allergies

OBJECTIVE

This study assesses the value of two recombinant birch allergens for diagnosis of patients sensitized to birch pollen with or without associated food allergy.

METHODS

Fifty-one patients with positive skin test responses to Betulaceae and seven nonallergic control subjects were investigated; specific IgE antibodies were evaluated by specific immunoassay and blot immunodetection.

RESULTS

Among 51 patients, 47 reacted to rBet v 1 and 10 to rBet v 2. Seven patients reacted to both recombinant allergens. In skin prick tests we found a correlation between the wheal produced by the commercial birch extract and the wheal produced by rBet v 1. Among 47 patients with positive test responses to rBet v 1, 83% had IgE binding to the Bet v 1 protein as determined by immunoblotting. Among 10 patients sensitized to rBet v 2, six had IgE binding to Bet v 2. Eleven patients with negative results, as determined by immunoblotting, had low levels of birch IgE in the sera (less than 10 kU/L) and low concentrations of IgE to rBet v 1 or rBet v 2 in ELISA. The nonallergic control subjects (n = 7) did not react to rBet v 1 or rBet v 2 in skin prick tests, nor did they have detectable amounts of specific IgE to rBet v 1 or rBet v 2. Histamine release tests confirmed sensitization to Bet v 1 in two patients with discordant results; for Bet v 2, one patient had positive results only at a high concentration, and one had results that remained negative. Thirty-four patients had birch pollinosis, and all reacted to rBet v 1. Patients who were monosensitized to birch never reacted to rBet v 2. Sensitization to rBet v 2 was only found in patients who reacted to other pollens (mainly grass). Twenty-nine patients demonstrated allergy to apples, cherries, or hazelnuts; and all reacted to rBet v 1. Among 11 patients with allergy to Umbelliferae, only three reacted to rBet v 2.

CONCLUSIONS

Use of the two recombinant allergens (rBet v 1 and rBet v 2) always permits the diagnosis of birch sensitization. Sensitization to rBet v 1 is specific for birch and Rosaceae allergies, whereas sensitization to birch profilin, Bet v 2, is encountered in multisensitized subjects and is not always related to Umbelliferae allergy.

[New aero-allergens]

As the number of proteins recognized as causing allergic respiratory diseases increases, new aero allergens have appeared in the animal and vegetable realms, both in home and professional environments. Lepidoglyphus destructor and Blomia tropicalis, two mites found in storage areas, are particularly important in agricultural areas and in homes. Over the last ten years, the frequency of reactions to cockroaches has also increased in several countries. The allergenicity of non-biting insects is a frequent cause of allergy in certain countries including Japan. Chironomides cause respiratory diseases in professional and outdoor environments. The important role of Alternaria, a mold, in producing severe asthma has also been demonstrated. The pathophysiology of pollen-induced asthma has been shown to result from pollen allergens carried by particles less than 5 microns in diameter. Cyprus and ash tree pollen also cause an increasing number of pollinoses and flowers can cause rhinitis and asthma. Respiratory allergy to Ficus benjamina inaugurated a new type of allergies caused airborne allergens from non-pollinating plants. Allergy to latex raises a particular problem for health care workers. The immunochemical structures of the major and minor airborne allergens are now better known and the homologous structures of different allergens largely explains certain cross-reactions. In the future, recombinant allergens will probably be used to better understand the role of allergens in inducing and maintaining the allergic reaction and should help in our approach to diagnosis and therapy.

First report of anaphylactic reaction after fig (Ficus carica) ingestion

We report an anaphylactic reaction which occurred very shortly after ingestion of a fresh fig. The IgE-dependent mechanism was demonstrated on the basis of positivity of the prick test performed with fresh fig (Ficus carica) extract. In addition, we were able to detect specific IgE to the same extract in the serum. The patient did not demonstrate sensitization to other common allergens involved in respiratory and food allergies. However, detection of specific IgE to F. benjamina indicated a sensitization to weeping fig. The CAP F. benjamina was partially inhibited by preincubation of the serum with fig extract, suggesting that these two species of Ficus share some common allergens. In this context, the assumption can be made that weeping fig was responsible for the initial sensitization in this patient.

[Importance of measuring exposure to the principal indoor allergens in allergic asthma]

Domestic allergens, such as mite and cat allergens, are a leading cause of allergic asthma. Allergen exposure is a risk factor for sensitization. Allergens also play a major role in the development of inflammation and non specific bronchial hyperreactivity as well as in the apparition and modulation of symptomatic asthma. The development of new means of detecting allergens (i.e. immunochemical assays including monoclonal antibodies, quantitative and semiquantitative guanine measurements for mite allergens) has made possible to identify allergens sources and reservoirs. The form in which domestic allergens become airborne is important. The group I and II allergens from mites, the major cockroach allergens are carried on large particles (mean size > 10 microns diameter); in contrast, the major cat allergens are airborne on small particles (40% < 5 microns). Guanine, a metabolic excretion product of mites, is used as a marker for mite feces and is correlated with the presence of major allergens from mites. A colorimetric method (Acarex-TestR) provides a simple and inexpensive method of assaying indoor mite allergen exposure for both doctor and patient alike. By using Acarex-TestR it is possible to evaluate the mite allergen exposure for a population in a particular country. The detection of allergens sources and reservoirs, the quantification of domestic allergens has enabled the evaluation of the effect of a reduction in allergen exposure to be better assessed. Recognition of the risks, environmental control and reduction in allergen loads, should be among the objectives of asthma management.

From allergen sources to reduction of allergen exposure

Allergen exposure plays a major role in the development of sensitization, inflammation and symptomatic asthma. The development of new means of detecting allergens has enabled the evaluation of the effect of a reduction in allergen exposure to be better assessed. In order to prevent allergen exposure it is necessary to determine the allergen sources and reservoirs to which avoidance measures should be directed. The allergen sources and reservoirs of mite, cat, dog, cockroach, rodent, mould and pollen allergens are briefly reviewed. The relationships between allergen exposure, sensitization, nonspecific bronchial hyperreactivity and asthma symptoms are discussed. Recognition of the risks, environmental control, and reduction in allergen loads should be among the objectives of asthma management.

Mite allergen content in mattress dust of Dermatophagoides-allergic asthmatics/rhinitics and matched controls

It has been suggested that the mites Dermatophagoides pteronyssinus and D. farinae are important indoor environmental factors facilitating both the sensitization of atopic subjects and asthmatic attacks of house dust-sensitive patients. Contradictory results have been reported about the current exposure to mites or their allergens among patients and control groups of atopic or non-atopic subjects. In order to determine whether there is a difference in mite exposure levels between D. pteronyssinus-sensitized asthmatics and/or rhinitis and control subjects we considered a case-control study of 70 patients with asthma and/or rhinitis and positive skin test reactions to D. pteronyssinus and twice as many control subjects who were matched as to age and sex. The first control subject for each patient was an immediate neighbour of the patient and the second was patient arbitrarily chosen among hospitalized patients. Mite allergen exposure was measured in mattress dust collected under standardized conditions, by measuring Der p I+Der fI content and by performing a semiquantitative guanine determination (Acarex-test). The content of Der p I and Der fI was very high both in the homes of patients and those of healthy individuals: 69% of the total samples contained more than 10 micrograms Der pI+Der fI/g of dust. There was no significant difference between cases and controls with respect to Der p I, Der fI, Der p I+Der fI content and Acare class distributions. The calculated odds-ratios associated with the Acarex test and the mite allergens did not differ significantly from the level 1.0.(ABSTRACT TRUNCATED AT 250 WORDS)

A double-blind, placebo controlled trial of solidified benzyl benzoate applied in dwellings of asthmatic patients sensitive to mites: clinical efficacy and effect on mite allergens

BACKGROUND

The aim of this double-blind, randomized study was to investigate the effectiveness of an acaricidal cleaning product in modifying both clinical symptoms and mite allergen levels over a period of at least 1 year.

METHODS

Twenty-six asthmatic patients with proven Dermatophagoides pteronyssinus (Dp) asthma were selected; three were withdrawn from the trial. The patients' homes were divided into two groups; 11 homes were treated with solidified benzyl benzoate and tenside agents (A), and 12 were treated with a placebo (P). Two applications were performed at the beginning of the trial and at least 6 months later. Patients were examined 1 month before the trial, at the beginning of the trial, and every 3 months over a period of 1 year. Indoor mite exposure was evaluated by three methods: semiquantitative guanine determinations, quantitative guanine determinations, and the measurement of Der p I + Der f 1 (antigen P, of Dp + antigen F1 of D. farinae) levels.

RESULTS

The symptom scores established at the beginning of the trial and 12 months later showed a statistically significant improvement only in the A group (p < 0.01). The visual analog scale also showed a statistically significant difference both in the A (p < 0.05) and P groups (p < 0.01). No statistical differences were found between medication scores in the A or P groups. A statistically significant increase was also observed for forced expiratory volume in 1 second and maximal expiratory flow rate 25/75 in the two groups (p < 0.05 for P group; p < 0.01 for A group). The mean decreases in Der p I + Der f 1 in patient mattresses between the beginning of the trial and after 12 months were 20% for the acaricide group and 17% for the placebo group, respectively (NS). For house dust samples with origins other than the patients' mattresses we found significant decreases in Der p I+Der f 1 in the A group (p < 0.01 for carpets and p < 0.05 for upholstery elements).

Protective effect of nedocromil sodium on the dual asthmatic response to bronchial antigen challenge

The effects of nedocromil sodium and placebo on the asthmatic response to antigen bronchial provocation were studied in a double-blind, randomized, crossover trial. Twelve subjects sensitized to Dermatophagoides pteronyssinus were challenged with successive doubling doses of this allergen (1.25-80 x 10(-3) mg) on two separate occasions, at least 15 days apart. A single dose of either nedocromil sodium 4 mg, or, a matching placebo was given 30 min before challenge. Forced expiratory volume in 1 s (FEV1) was measured 5, 10 and 15 min after challenge. Early asthmatic response was analyzed using three indices: dose producing a 20% decrease in FEV1 (PD20), the slope of and area under the dose-response curve. Nedocromil sodium was significantly superior to placebo with respect to all three indices, providing significant inhibition of the early asthmatic responses. Seven of the 12 patients showed a late asthmatic response. There was no significant difference between the effects of nedocromil sodium and placebo treatments on the decline in peak expiratory flow rate (PEFR) during the late asthmatic response but it should be noted that when patients had been treated with nedocromil sodium they were receiving two to eight times the dose of allergen given after placebo treatment.

[Occupational asthma: an experimental asthma. Apropos of isocyanate-induced asthma]

Isocyanate-induced occupational asthma is a model of experimental asthma related to the environment. Many of its features are identical with those of allergic asthma by sensitization to air-borne allergens. Exposure to isocyanate before the first symptoms of asthma varies from a few weeks to several years. The prevalence of isocyanate-induced asthma has been estimated at 5 to 25%. Atopy is found in less than 30% of the cases. A significant increase of HRBNS can be demonstrated in most patients, but it may be absent. It may also fluctuate with the working periods or after a bronchial provocation test with isocyanate. Elimination of this compound reduces the HRBNS level in only one quarter of the cases. Delayed or biphasic reactions are frequent: 30 to 60% depending of the authors. An early diagnosis followed by total elimination may result in complete cure, but more than 50% of the patients remain symptomatic and with HRBNS. An IgE-dependent mechanism can be demonstrated in about 20% of the cases. The course of isocyanate-induced asthma is interesting in that the same phenomena are probably observed in chronic asthma resulting from repeated exposures to environmental allergens.

[Occupational asthma]

The diagnosis of occupational asthma requires the integration of a multiplicity of data; the history, cutaneous skin tests, biological tests, respiratory function tests and non-specific tests of bronchial hyperreactivity and specific bronchial provocation test. The history search for the presence of an atopic state, the occurrence of similar disorders in members of the same firm and also the timing of symptoms in relation to the occupational activities. Cutaneous tests are particularly helpful in IgE-mediated asthma in relation to the inhalation of animal or vegetable materials of glycoprotein origin. For haptens, the need for their prior coupling to a protein carrier causes problems which have not been entirely resolved. Laboratory tests run into the same snags. Respiratory function and non-specific bronchial provocation tests, confirm the diagnosis of asthma and enable the medium and long term prognostic to be assessed. Specific bronchial provocation tests are the most appropriate tests to establish an aetiological diagnosis in occupational asthma. Different technical methods are possible: quantitative administration of allergen aerosols, realistic tests, and tests using exposure chambers to achieve true test doses. The products responsible for occupational asthma are multiple. The different substances are characterised in a simplified manner: first animal matter (mammalian and arthropod allergens), secondly substances of vegetable origin (roots, leaves, flowers, grain and flour, wood and its derivates) and finally chemical products. The chemical products are primarily from the pharmaceutical and metal industries and above all from the plastics industry.

[Diagnostic methods in allergic asthma]

Analysis of the allergic component in asthma results in a critical comparison of the data provided by the interview, skin tests, possibly completed by carefully selected immunological tests and/or bronchial or nasal stimulation tests. For some allergens, it is also possible to study the allergenic environment of these patients. The skin tests allow an easy analysis of the skin mastocytes carrying specific IgE and degranulating after the allergenic extract has been introduced. Among the in vitro tests, phadiatop represents a screening test of respiratory allergies which is more reliable than total IgE assays. Specific serum IgE assays should be reserved for difficult or conflicting cases. Bronchial allergen stimulation tests confirm the etiopathogenic role of an allergen. A few examples of diagnostic strategies are presented.

Cross-reactions between respiratory and food allergens

Cross-reactions between inhaled and food allergens are usually attributed to pollen hypersensitivity associated with fruit and vegetable allergy. However, other allergens are involved in these types of cross-reactions. In a few cases, there is a complete similarity between the inhaled and food allergens (garlic, crustacea proteins). More frequently, partial similarity has been demonstrated: whole inhaled allergens are included in ingested substances. Moreover, immunological techniques can demonstrate common antigenic epitopes in organic substances without any apparent relationship. This has been demonstrated by RAST-inhibition and/or immunoblot techniques, using sera from patients cross-sensitized to (1) pollens and fruits or vegetables or (2) avian sera and eggs. Respiratory sensitization always seems to precede food allergy symptoms.

Platelet function: aggregation by PAF or sequestration in lung is not modified during immediate or late allergen-induced bronchospasm in man

Among the mediators involved in the pathophysiologic mechanisms that underly the reactions of the acute and delayed phases of bronchospasm induced by allergens in man, platelet-activating factor (PAF) could play an important role, in particular by its effects on platelets. In animals, inhalation or injection of PAF causes a platelet-dependent bronchoconstriction that is blocked by prior administration of an antiplatelet antiserum and accompanied by platelet accumulation in the pulmonary vessels. In man, inhalation of PAF causes a bronchospasm and induces a bronchial hyperreactivity. Abnormalities of platelet aggregation and the secretion into plasma of platelet factor 4 and beta-thromboglobulin have been described in patients with asthma during induced bronchospasm. Platelet functions have been studied in 15 patients with asthma before and after allergen bronchial provocation tests. There was no difference between platelet counts, plasma concentrations of platelet factor 4 and beta-thromboglobulin, and platelet aggregation induced by several agonists (adrenaline, arachidonic acid, or PAF) before and immediately after the allergen bronchial provocation test. There was no platelet pulmonary sequestration as studied with 111Indium-labeled platelets during 24 hours after the antigen challenge, and the life span of circulating platelets was normal. Our results do not support an important direct role for PAF in the pathophysiology of asthma. It is still possible that the current methodology is too insensitive to detect amounts of PAF in the circulation or that PAF is acting locally.

[Drug prevention and physical protection in occupational asthma]

Many means of protection can be used in work-related asthma. Drug protection may be by symptomatic treatment with classical anti-allergic drugs such as Cromoglycate and Ketotifen. Therapy with corticosteroids has a preventative action on the delayed allergic reaction. Drug protection is however only palliative and incomplete. Individual physical protection needs masks that may be filtering, or anti-dust, or anti-gas, or helmets or masks that have air addition, or even autonomous respirators. The main efforts in prevention should be made against the responsible agents, with their identification and reduction of the level of exposure. This reduction of exposure may be done by re-structuring the work place, by sufficient ventilation and extraction or by addition of moisteners. Modification of the manufacturing process may also be affective, by alterations to make the manipulations in a chamber or closed circuit, to the apparatus, automation and computer control or changes or replacement of the agents responsible for the work-related asthma.

Guanine and mite allergenicity in house dust

Guanine is the major nitrogenous waste product in arachnids. It may serve as an indicator for allergenic mite faecal pellets. The present study assesses the correlation between the mit allergenicity of different house dust (HD) samples and their guanine content. Guanine content in HD samples was evaluated either by the Acarex-Test or determined quantitatively, especially for in-vitro methods. Using intradermal tests in selectively sensitized Dermatophagoides pteronyssinus (Dpt) patients, we evaluated the mite allergenicity of eight extracts obtained from HD samples with varying guanine contents. The weal area appeared to be proportional to the HD samples' guanine content. A three-fold increase in skin reactivity was observed when the guanine content varied from 0.06% to more than 1%. Patients allergic to HD but not to Dpt had no significant reactions with HD extract prepared from a guanine-rich HD sample. For eighteen different HD samples coupled to paper discs, the percentage Dpt RAST binding values obtained with a Dpt-selectively sensitized patient serum pool was correlated with the guanine concentrations of HD samples (P less than 0.01). The potencies of different HD extracts obtained from HD samples that varied in guanine content were also clearly distinguished on histamine-release titration curves. House dust obtained from homes at high altitude or from hospitals was generally guanine free. The HD sample guanine contents in homes where twelve Dpt-sensitized patients experienced symptoms were significantly higher than in homes where these patients were symptom free. The guanine colour test, a quick and easy technique, represents an important new development in indoor environmental investigations. It makes it possible to demonstrate mite faecal exposure and can be used to monitor the effectiveness of mite allergen avoidance measures.

Celery allergy: clinical and biological study of 20 cases

In 20 patients, the ingestion of celery was responsible for mucocutaneous symptoms (generalized urticaria and angioedema) (18/20) and respiratory disorders (7/20). Four cases of systemic anaphylaxis were observed. The main associated allergic disorder was pollinosis (16/20). Food allergy to other vegetable products, mainly other Umbelliferae and apples, coexisted with celery allergy in 12 cases. It was found that celery allergy is mediated by IgE antibodies: it is easily diagnosed by skin tests (fresh extracts of celery may be used) and by adequate RAST (17 positive results). Cosensitization with mugwort pollen (14 cases) and birch pollen (9 cases) was found. Celery allergens responsible for clinical sensitization originate chiefly in the tuber and are at least partly thermally labile. The frequent association with pollen sensitization suggests the existence of common antigenic epitopes in celery extracts and mugwort and birch pollens. The immunologic investigations carried out so far (RAST inhibition and immunoprint) seem to support this hypothesis.

Positive skin tests to aero-allergens and month of birth

The month of birth distribution for 1301 French patients born between 1953 and 1975 with at least one positive skin test was compared to that of the whole population. A chi-square test was performed, and the expected birth month distribution of the groups calculated from the INSEE* data for 1953-1975. All patients underwent skin testing with house dust, Dermatophagoides pternyssinus (Dpt), cat and dog allergens, grass, tree and weed pollens, and moulds. The only study criterion was a positive skin test unrelated to any specific disorder. A significant difference in month of birth distribution was observed 1) for patients with positive skin test to grass pollen, with a high rate of births from January to May, and 2) for patients with mould sensitization, with a low rate of births in April, May and December. Tree and weed pollens, house dust and Dpt showed no significant relation with month of birth. For cat and dog allergens, the observed and expected distributions of birth month were similar. For the whole sensitized population the birth rate tended to be low in December except for the cat and dog sensitized. Our study confirms the well-known seasonal peak of births in the first 5 months of the year for grass pollen sensitized patients. No consistent monthly or seasonal tendency could be statistically demonstrated for other allergens except moulds.

Celery sensitivity: clinical and immunological correlations with pollen allergy

The authors studied twenty patients with celery allergy and concomitant hypersensitivity to certain pollens (mugwort, birch). The specific symptoms induced by eating celery were attacks of urticaria and angio oedema (seventeen out of twenty) respiratory complaints (eight out of twenty), systemic anaphylaxis with vascular collapse (three out of twenty). A strong association between clinical reactions to celery and mugwort sensitization, and to a lesser degree between celery allergy and birch pollen sensitization was established. Celery allergy is mediated by IgE antibodies and can be easily diagnosed by cutaneous tests using fresh material and/or by adequate RAST test. RAST inhibitions performed on individual sera suggest the existence of common antigens in celery and mugwort, and in celery and birch pollen. However, the exact nature of these common antigens has not yet been determined.