Studies on the relationship between the level of specific IgE antibodies and the clinical expression of allergy: I. Definition of levels distinguishing patients with symptomatic from patients with asymptomatic allergy to common aeroallergens

BACKGROUND

The detection of specific IgE antibodies to environmental allergens does not always coincide with a diagnosis of clinically evident allergic disease, because some patients with positive skin and/or in vitro test results have no symptoms related to the allergen or allergens that induced the antibodies.

OBJECTIVE

In a multicenter study the optimal cutoff values for specific IgE antibody levels and skin test results that could discriminate between patients with symptomatic and those with asymptomatic allergy were determined.

METHODS

IgE antibodies specific for a panel of common aeroallergens were assayed with the Pharmacia CAP System (Pharmacia, Uppsala, Sweden) in two groups of patients, a group of 267 patients with symptomatic allergy and a group of 232 with asymptomatic allergy--both with positive skin prick test results--and in a group of 243 healthy, nonallergic control subjects. The cutoff values were established by receiver operating characteristic analysis.

RESULTS

A significantly higher mean specific IgE antibody value was found in patients with symptomatic allergy compared with patients with asymptomatic allergy (p < 0.001) and in patients with symptomatic allergy compared with healthy control subjects (p < 0.001). The optimal CAP System cutoff value between patients with symptomatic and those with asymptomatic allergy was 11.7 kU/L, and when seasonal allergens were compared with perennial allergens, the cutoffs were 10.7 kU/L and 8.4 kU/L, respectively. The optimal cutoff value for the skin prick test was a wheel area of 32 mm2 for seasonal allergens and 31 mm2 for perennial allergens. The skin test had a lower diagnostic value (sum of sensitivity and specificity) than the CAP System.

CONCLUSIONS

Cutoff values for specific serum IgE antibody levels are likely to be useful in clinical practice to distinguish symptomatic from asymptomatic allergy in patients with positive skin test results.

Mechanisms in adverse reactions to food. The mouth and pharynx

Symptoms appear immediately at the site of contact with the food when a susceptible allergic patients eats the offending food. Allergy to fresh fruits and vegetables, associated with all kinds of pollinosis, is the more frequent cause of Oral Allergy Syndrome.

Allergenic cross-reactivity among peach, apricot, plum, and cherry in patients with oral allergy syndrome: an in vivo and in vitro study

BACKGROUND

Oral allergy syndrome in response to fruits and vegetables frequently occurs as clusters of hypersensitivity to members of the same botanical family, for which the immunologic basis lies in a number of common allergens, most of them still unidentified.

OBJECTIVE

This study was designed to assess the in vivo and in vitro cross-reactivity between fruits of the Prunoideae subfamily (i.e., peach, cherry, apricot, and plum) and to identify their major allergens and the cross-reactivity of the peach extract with grass and birch pollen.

METHODS

The in vivo study was conducted by skin prick tests and open food challenges with fresh fruits in 23 patients with oral allergy syndrome for peach and positive skin prick test and RAST results for the other Prunoideae. In vitro sodium dodecylsulfate-polyacrylamide gel electrophoresis was followed by immunoblotting and immunoblotting-inhibition.

RESULTS

A 13 kd component was identified as the only major allergen common to all the Prunoideae, the other major allergens were found at 14 kd in peach and at 30 kd in cherry. Immunoblotting inhibition showed wide cross-reactivity within the Prunoideae, whereas grass and birch pollen partially inhibited the peach blotting.

CONCLUSIONS

Clinical cross-reactivity to Prunoideae is essentially due to a common 13 kd IgE-binding component, which seems to be the most important major allergen of this subfamily, not shared with grass and birch pollen.

Importance of allergic etiology in nasal polyposis

Sensitization to environmental allergens in nasal polyposis was evaluated in an in vitro study conducted on 90 patients undergoing polypectomy by measuring total and specific IgE for a panel of common allergens and levels of IgG, IgA and albumin in serum, and nasal secretions (NSe). Fifty healthy individuals were chosen as a control group. Total IgE concentrations were higher in patients with nasal polyps than in controls. RAST was positive in serum in 34 (38%), in NSe in 29 (32%), and exclusively in NSe in 10 patients (11%). Allergens most frequently involved were mites and cat dander. No differences were found between the study and control groups for serum and NSe IgA, albumin, and serum IgG, whereas IgG in NSe were significantly higher in patients with nasal polyps. Subjects with positive RAST only in NSe had significantly lower secretory IgA than did controls. Our data indicate that in nasal polyposis: 1) sensitization to aeroallergens is relatively common; 2) a local production of specific IgE may occur, especially for perennial allergens; 3) prolonged exposure to these allergens gives rise to chronic nasal inflammation, with altered local production of immunoglobulins.

Comparison of rhinomanometry, symptom score, and inflammatory cell counts in assessing the nasal late-phase reaction to allergen challenge

Inspiratory nasal resistance, symptom score, and influx of inflammatory cells into the nose were evaluated before and after a nasal challenge in 15 patients with grass pollen rhinitis and in six nonallergic control subjects, to study the nasal late-phase reaction and its relationship with nasal cytology. All patients had an immediate positive reaction to specific nasal challenge. In seven allergic subjects we observed a later inspiratory nasal resistance increase, but only two had a significant late symptom score. Inflammatory cells increased by 8 hours in all the patients; the higher the cell influx, the higher the symptom score. Close correlations were found between the inspiratory nasal resistance increase, nasal obstruction at hours 8 and 24, and all cell counts. In control challenges there were no significant increases of symptom score or inspiratory nasal resistance either during the challenge or in the next 24 hours. A weakly significant increase was found only for neutrophil counts at 8 hours. These results indicate that an inflammatory reaction constantly occurs after a specific nasal challenge; its extent is closely related to inspiratory nasal resistance and to the intensity of nasal obstruction. Moreover, our data outline the pivotal role played by eosinophils and basophils in the genesis of an allergic late-phase reaction in the nose.

A double-blind, placebo-controlled study of immunotherapy with an alginate-conjugated extract of Parietaria judaica in patients with Parietaria hay fever

A double-blind, placebo-controlled study was conducted to evaluate the efficacy and safety of immunotherapy (IT) with a partially purified alginate-conjugated extract of Parietaria judaica (Conjuvac Parietaria, Dome/Hollister-Stier) in patients suffering from rhinoconjunctivitis caused by Parietaria pollen. Eighteen patients (10 women, 8 men, mean age 35 years) received active treatment and 17 (10 women, 7 men, mean age 42.5 years) received placebo. Actively treated patients had significantly lower nasal symptom/medication scores (running nose P = 0.0087 and sneezing P = 0.048) during the Parietaria pollen season. Significant decreases in specific skin (P < 0.01), nasal (P < 0.05), and conjunctival (P < 0.01) reactivity to the Parietaria extract and significant increases of specific IgG (P < 0.001), IgG1 (P < 0.001), and IgG4 (P < 0.001) in actively treated patients, but not in placebo, were found. IT was well tolerated, the active extract inducing five mild systemic reactions (four rhinitis and one urticaria) and placebo two (rhinitis). A significant correlation was found between low skin reactivity and high specific IgG (P = 0.0002) and IgG4 (P = 0.036). These findings indicate that IT with a partially purified P. judaica extract is an effective and safe treatment for Parietaria pollen allergy. The correlation between low immediate skin reactivity and high specific IgG and IgG4 suggests that, at least in the studied cutaneous model, these antibodies may exert a blocking effect.

IgE-mediated allergy from vegetable allergens

Allergy to fresh fruits and vegetables is IgE-mediated. Its main clinical features are local, such as oral pruritus and swelling of lips and tongue but systemic symptoms such as urticaria, asthma, or anaphylactic shock may occur. Clinical associations with allergic rhinitis due to cross-reactive antigens of pollens and foods are frequent.

Clinical evaluation of CAP System and RAST in the measurement of specific IgE

We investigated the diagnostic value of a new in vitro test, Pharmacia CAP System (Pharmacia Diagnostics AB, Uppsala, Sweden), for the quantitative measurement of allergen-specific IgE antibodies by comparison with RAST in 2 groups of patients, 71 atopic and 48 non-atopic. In the last 20 years RAST has supplied a good diagnostic tool, but this test presents some problems, the main one being sensitivity. The new test has a solid phase able to bind even very small amounts of specific IgE and an anti-IgE tracer with very low cross-reactivity with other immunoglobulins, thus presenting more favourable conditions. From the analysis of our results, Pharmacia CAP System gave higher sensitivity (94% compared to 88% of RAST) with no loss of specificity (96% for both tests). The reliability of these results is ensured by the proper selection of patients who were all suffering from pollinosis and were clinically diagnosed as certainly hypersensitive to a single pollen. A positive trend was found between severity of asthma and levels of specific IgE for timothy. Pharmacia CAP System appears to identify a larger number of atopic patients than RAST.

Clinical and immunological effects of immunotherapy with alum-absorbed grass allergoid in grass-pollen-induced hay fever

A double-blind, placebo-controlled study of immunotherapy was conducted in 19 patients with grass-pollen hay fever to evaluate the efficacy and safety of a formalinized depot grass allergoid. The patients were assessed before and during IT by clinical (symptom-medication scores during the grass- pollen season, specific nasal and skin reactivity) and immunological (specific IgE, IgG, IgG1 and IgG4 antibodies) parameters. High doses of grass allergoid, corresponding to a cumulative pre-seasonal dosage of 46,050 PNU, were administered, with only one systemic reaction. The actively treated patients had significantly lower symptom-medication scores than placebo (p less than 0.01) during the month of May and showed a significant decrease in specific skin (p less than 0.01) and nasal (p less than 0.05) reactivity, and a significant early increase in specific IgE (p less than 0.01), IgG (p less than 0.0005), IgG1 (p less than 0.001) and IgG4 (p less than 0.05), with a subsequent decrease of IgE and IgG1. No differences were detected in any of these parameters in the placebo group. A correlation was found between high IgG4/IgG1 ratio and the specific skin reactivity decrease (r = 0.691, p less than 0.05), whereas a high IgG4/IgG1 ratio was associated with higher symptom-medication scores (r = 0.654, p less than 0.05). Possible explanations of these apparent discrepancies are proposed.

A multicentric study on sensitivity and specificity of a new in vitro test for measurement of IgE antibodies

The sensitivity and specificity of the Pharmacia CAP System, a new in vitro assay for measuring IgE antibodies, were evaluated in a multicentric study on 286 allergic patients and 243 normal subjects. Sensitivity was 95.5%, with results significantly better than RAST for some allergens, and specificity was excellent, 98.1%.

Are double-blind food challenges necessary before starting an elimination diet?

Food allergy is normally treated by eliminating the offending food. Such a measure, however, may cause nutritional and sociopsychological problems, so an allergy must be diagnosed with the utmost certainty. To date the most reliable diagnostic test is the double-blind food challenge (DBFC). The rationale for using this test is the marked difference in positive results with open and double-blind food challenges. Only about 30% of open challenges that appear positive are confirmed on blind challenge. There is ample evidence, too, that a negative DBFC may in fact indicate tolerance to that food. From the literature it appears that almost all patients who reintroduced a certain food into their diet after a DBFC had given negative findings did not present any adverse reaction to it. In our caselist of 21 patients with probable reactions to foods but negative DBFC, 19 (90.5%) tolerated the "incriminated" food well when it was reintroduced into their diet even in unlimited amounts. Only two (9.5%) again presented symptoms when they started taking large amounts of the problem food. Therefore, one precaution recommended before reintroducing a food item into a patient's diet after a negative DBFC is to check how it is tolerated at high doses. A review of the literature confirms the unquestioned utility of the DBFC. Nevertheless, in some situations this test is not indicated. The main one, of course, is in patients with life-threatening symptoms such as anaphylactic shock or glottis edema, in whom any provocation test is contraindicated.(ABSTRACT TRUNCATED AT 250 WORDS)

A double-blind study of hyposensitization with an alginate-conjugated extract of Dermatophagoides pteronyssinus (Conjuvac) in patients with perennial rhinitis. II. Immunological aspects

In a 2-year double-blind placebo controlled study an immunological evaluation was carried out on 33 patients (15 males, 18 females, mean age 29.2 years) with mite-induced perennial rhinitis who were submitted to specific immunotherapy (IT) with an alginate-conjugated extract of D. pteronyssinus. The behaviour of IgE, IgG, IgG1 and IgG4 antibodies specific to D. pteronyssinus and its major allergen Der p1 was characterized by assessment of their changes in serum, and changes in IgG in nasal secretions during the treatment. The placebo-treated patients did not show any significant variation in the levels of specific antibodies, while in the actively treated patients we found: a statistically significant decrease (P less than 0.005) of specific IgE, a statistically significant increase of specific IgG (P less than 0.005), IgG1 (P less than 0.005) and IgG4 (P less than 0.005) in serum and a statistically significant increase (P less than 0.001) of specific IgG in nasal secretions. The IgG response showed an early relative predominance of the IgG1 subclass and a late absolute predominance of IgG4 subclass, that confirmed the model of IgG4 restriction in prolonged allergen stimulation. No correlation was found between immunological and clinical data.

Role of the elimination diet in adults with food allergy

The aim of the study was to check whether, after a period of complete exclusion of the offending foods in adult subjects suffering from food allergy, these foods could subsequently be safely reintroduced into the diet. Patients with chronic urticaria and/or perennial rhinitis negative for secondary pathology or other allergies were subjected to a strict diagnostic protocol for food allergy. Briefly, out of a case list of 207 patients, we found 23 patients whose symptoms were clearly related, on open reintroduction, to at least one food. The really offending foods in these patients were subsequently identified by double-blind, placebo-controlled food challenges. Only 10 of the 23 patients had positive challenges for 13 foods. Double-blind challenges were repeated after 1 year or more of avoidance of the offending foods to evaluate the persistence or disappearance of sensitivity. We found that five (38%) of the 13 previously offending foods were well tolerated. Thus, in adults, as previously proved in children, dietary avoidance of the offending foods appears to be an effective measure for dealing with food allergy. The kind of foods involved and the completeness of their avoidance appeared to be important factors favoring the reestablishment of tolerance in adults.

[Allergy to Hymenoptera venom in children. Diagnosis and therapy]

We studied 52 children, 3 to 15 years of age, suffering from allergic reactions following Hymenoptera stings. The diagnosis of allergy was based on history, results of skin tests and RAST performed by purified venoms of Apis mellifera, Vespula species and Polistes species. The history of children with multiple stings of the same insect showed an essential favourable prognosis, thus suggesting to submit to specific immunotherapy only children with severe reactions. For these patients it is necessary to perform therapy only in specialized Centres, because of the high frequency of adverse reactions which we observed in 33% of our treated patients.

Comparison of results of skin prick tests (with fresh foods and commercial food extracts) and RAST in 100 patients with oral allergy syndrome

One hundred adult patients with a history of oral allergy syndrome (OAS) after ingestion of fruits and vegetables, 77 patients with hay fever and 13 with skin prick tests and RAST positive to pollens but without seasonal symptoms, and 32 normal nonallergic control subjects, had Phadebas RAST and skin prick tests with commercial extracts (CSPT) and with fresh foods (FFSPT) to assess the reliability of these three tests. Sensitivity was better with FFSPT for carrot, celery, cherry, apple, tomato, orange, and peach; better with CSPT for peanut, pea, and walnut; and better with RAST for hazelnut. Specificity, negative predictive value, and positive predictive value of the three tests were determined for apple, carrot, hazelnut, orange, pea, peanut, and tomato. Specificity in the patient groups ranged between 40% (pea) and 100% (apple) for CSPT, between 61% (peanut) and 87% (carrot) for RAST, and between 42% (carrot) and 93% (peanut) for FFSPT. However, all tests were negative in the control group. Thus, false positive results may result from cross-reactivity with pollen allergens. The diagnostic accuracy of these tests in the population with OAS proved comparable for peanut, carrot, hazelnut, and pea. FFSPT proved more sensitive than CSPT or RAST in confirming a history of OAS to certain alimentary allergens, such as apple, orange, tomato, carrot, cherry, celery, and peach.

IgE-mediated food allergy

The behaviour of some immunologic parameters was studied in order to explain the presence or the lack of symptomatology in subjects with IgE specific to foods. In particular, we compared the levels of serum and salivary IgA and IgE antibody specific to apple in 33 patients allergic to birch and with anti-apple IgE, of whom 24 had oral allergy syndrome after eating apple and nine were apple tolerants. We found no differences in the IgE-related parameters such as levels of anti-apple IgE antibody in serum and secretions, mean size of apple skin prick test, and number of patients with a positive histamine release from peripheral basophils stimulated by apple. Similarly, we detected no statistically significant differences in serum and salivary total IgG and total anti-apple IgA antibody of the two groups. We could, however, observe a significantly higher anti-apple salivary IgA/anti-apple serum IgE and anti-apple salivary IgA/anti-apple serum IgA ratios and a significant correlation between the same parameters in tolerant patients when compared with the intolerants. These results seem to suggest that the presence of appropriate levels of secretory anti-apple IgA associated to anti-apple IgE might be one of the factors playing a key role in the prevention of clinical symptoms in atopic subjects.

The role of suggestion in asthma. I. Effects of inactive solution on bronchial reactivity under bronchoconstrictor or bronchodilator suggestion

Twenty-eight subjects affected by perennial asthma were selected in order to investigate the possibility of inducing or relieving an asthmatic attack by means of suggestion. Twenty-five were positive to methacholine challenge test and, among them, eleven reacted to an ultrasonic nebulized distilled water test. The effect of suggestion on airway response was assessed by eight inhalations of normal saline at 32 degrees C alternately presented as a bronchoconstrictor or as a bronchodilator drug. Eight inhalations of the same diluent without any psychic stimulus were used as control test. Seven patients reacted with bronchoconstriction to both positive and negative suggestion and to control test. Further, this group of patients showed a lower methacholine PD20 when compared with the other subjects. In this study, the effects of suggestion on bronchial reactivity were not observed and bronchoconstriction belonged to an individual hyperreactivity of the airways.

IgG subclass antibody response to hymenoptera venom

Venom immunotherapy provides clinical protection against hymenoptera stings in almost all treated allergic patients. Venom specific IgG antibodies often rise during immunotherapy and some studies found an association between their levels and clinical protection in subjects treated with Yellow Jacket venom. It is interesting to report that, among IgG subclasses, venom specific IgG4 show the most significant increase but IgG1 could represent a relevant immunological mechanism, exerting a regulatory function on venom specific IgE levels. We observed in patients submitted to Honey Bee venom immunotherapy a significant increase of venom specific IgG1 and IgG4 antibodies, while IgG2 showed an insignificant increase only in some patients. Persistent high levels of IgG4 with respect to decreasing levels of IgG1 were observed only after prolonged treatment.

The role of suggestion in asthma. II. Effects of a bronchoconstrictor drug on bronchial reactivity under bronchoconstrictor or bronchodilator suggestion

Previous studies have shown that suggestion may modify bronchial reactivity to both inactive diluents and pharmacologically bronchoconstrictor or dilator substances. In our study, 14 patients were subjected to two methacholine challenge tests presented, respectively, as a bronchoconstrictor or as a bronchodilator drug. Forced expiratory volumes in one second were recorded and a PD20 was determined. No significant differences were reported in PD20 values of each patient after the two kinds of suggestion.

Allergen specific IgG subclass antibody response in hyposensitization with Dermatophagoides pteronyssinus extract

Most of the controlled trials of specific immunotherapy (SIT) with house dust mite showed a good clinical efficacy of different kinds of extract after variable periods of treatment. However, few of them looked at all the parameters available to monitor this therapy, such as threshold dose of specific provocation test, end point titration and immunological variations. In particular, the behaviour of specific IgE antibodies is not completely known, while, in more recent studies, mite specific IgG antibodies have been shown to increase even in the early stages of treatment. Few data are available on mite specific IgG1-4 subclasses. The preliminary results of a double blind placebo controlled trial we performed with alginate conjugated Dermatophagoides pteronyssinus extract seem to indicate a good clinical and immunological response to this kind of extract. Moreover, we observed a significant increase of specific IgG antibodies, total and subclasses IgG1.2.4, with a prevalence of IgG4 subclass after three months of SIT. After two years of SIT mite specific IgG1 antibodies showed a tendency to decrease, while IgG4 antibodies maintained a constantly high level.