Allergen microarray: comparison of microarray using recombinant allergens with conventional diagnostic methods to detect allergen-specific serum immunoglobulin E

BACKGROUND: The availability of recombinant allergens and recent advances in biochip technology led to the development of a novel test system for the detection of allergen-specific IgE. OBJECTIVE: To test the performance of this allergen microarray in a serological analytical study. METHODS: Standard allergens contained in grass pollen (Phl p 1, Phl p 2, Phl p 5 and Phl p 6) and tree pollen (Bet v 1 and Bet v 2) were used as a model system. The detection of allergen-specific serum IgE using microarrays was compared with standard test systems: CAP/RAST and an in-house ELISA. In order to test the analytical sensitivity of the assays, geometric dilutions of a serum pool containing high levels of pollen-specific IgE from allergic individuals were tested in each system. To assess the analytical specificity, the sera of 51 patients with presumptive allergic symptoms were collected before diagnosis. Thereafter, the results for grass/tree-pollen-specific IgE were compared. RESULTS: The microarray has a good dynamic range similar to the CAP/RAST system. Microarray and ELISA showed comparable analytical sensitivity exceeding the CAP/RAST system. With respect to the analytical specificity, no significant cross-reactivity of the allergens was observed. For two of the allergens tested, weak positive signals were detected in the microarray test system, whereas they were not detectable by CAP/RAST. CONCLUSION: A good correlation of presently used methods to detect serum IgE and the novel microarray test system was observed. As a next step, a careful validation of this method for a multitude of allergens and a thorough clinical evaluation has to be provided. Microarray testing of allergen-specific IgE can be presumed to be the method of choice for a prospective component-resolved diagnosis of Type I allergy, and the basis for the design and monitoring of a patient-tailored specific immunotherapy in the future.     

The role of food allergens in childhood asthma

Eighty-eight patients' sera with allergen-specific IgE levels elevated only to food allergens were collected between October 1997 and March 2002 at the National Taiwan University Hospital. Thirty-three of the patients fulfilled the diagnostic criteria of asthma and were included. Most (72.7%) patients had elevated serum allergen-specific IgE levels only to one food allergen. The most common food allergens were milk and egg white. The patients with elevated soy bean-specific IgE levels had significantly higher levels of serum food allergen-specific IgE than those with either elevated milk or egg white-specific IgE levels. This study investigated some food allergen responses of asthmatic patients whose serum allergen-specific IgE levels were elevated only to food allergens. The results suggested that the allergic asthmatic response in our patients was most likely related to food rather than aeroallergens or fungal allergens.     

Dissociation of allergen-specific IgE and IgA responses in sera and tears of pollen-allergic patients: a study performed with purified recombinant pollen allergens

BACKGROUND: Trees and grass pollen allergens represent potent elicitors of allergic rhinoconjunctivitis and asthma. Little is known regarding the presence of allergen-specific IgA antibodies in sera and tears and their association with IgE responses in patients with allergic conjunctivitis. OBJECTIVE: The purpose of this study was to compare the specificities of IgE and IgA antibodies in sera and tears of pollen-allergic patients with conjunctivitis by using purified recombinant pollen allergens. METHODS: Sera and tears collected from 23 pollen-allergic and from 23 nonatopic individuals were analyzed for IgE and IgA reactivity to nitrocellulose-blotted birch and timothy grass pollen extracts. In addition, we determined the specificities of IgE, IgG(1-4), and IgA antibodies with use of a panel of purified recombinant pollen allergens (timothy grass: rPhl p 1, rPhl p 2, rPhl p 5; birch: rBet v 1, rBet v 2) in serum and tear samples by immunoblotting and ELISA. Statistical analyses of data were performed by t test and Mann Whitney U test. RESULTS: Serum and tears of many of the pollen-allergic individuals with conjunctivitis exhibited specificity for the very same pollen allergens. No allergen-specific IgE antibodies were detected in tears of nonatopic individuals. IgA antibodies in sera and tears of patients with allergic conjunctivitis were mainly directed against nonallergenic moieties and showed specificities that were significantly different from those of IgE antibodies. CONCLUSION: The dissociation of IgE and IgA responses and the lack of allergen-specific IgA antibodies in mucosal secretions (eg, tears) may contribute to allergic manifestations in target organs of atopy. Induction of allergen-specific IgA antibodies may hence be considered as a promising strategy for the treatment of mucosal forms of atopy.     

Phleum pratense-specific T cells of allergic rhinitis patients display a broader recognition pattern than Phleum pratense-specific serum immunoglobulin E

BACKGROUND: The role of allergen-specific CD4+ T lymphocytes in the pathophysiology of atopic disease is well established. Previous studies on allergen-specific T-cell responses have focused on the recognition of single major allergens to identify T-cell epitopes. OBJECTIVE: However, it is not clear whether immune responses to allergen extracts are exclusively targeted at major allergens or whether additional proteins are recognized. METHODS: Here we describe the Phleum pratense-specific immunoglobulin E (IgE) and T-cell responses of six allergic rhinitis patients. Reactivity was measured to size-separated fractions of a P. pratense extract as well as to the purified major allergens Phl p 1, Phl p 2/3 and Phl p 5. RESULTS: The specificity of the patients' serum IgE, measured in a fluid phase assay, was restricted to one or two of the major allergens. Even though the majority of the patients had IgE antibodies reactive with a single major allergen, one patient reacted with both Phl p 5 and with Phl p 2/3. Analysis of the T-cell repertoire with P. pratense-specific T-cell lines (TCLs) and CD4+ T-cell clones (TCCs) revealed that at least six different proteins were recognized, including the three major allergens, most notably Phl p 5. Simultaneous production of IL-5 and interferon (IFN) -gamma was detected in supernatants of the TCLs stimulated with P. pratense extract and the major allergens. CONCLUSION: These results indicate that allergic rhinitis patients have a large pool of circulating allergen-specific CD4+ T cells that recognize many different proteins in an allergenic extract, whereas only a small number of these proteins are recognized by serum IgE.     

Allergen-specific immunoglobulin E antibodies in tears and serum of vernal conjunctivitis patients

Tears and sera of 53 patients of vernal conjunctivitis were examined for antibodies of the IgE type to a panel of 18 allergens. In 18 of the patients (34.0%) allergen-specific IgE was demonstrated in both tears and serum, in 3 (5.7%) in tears only, and in 4 (7.5%) in serum only. The antigen-specific reactions with tear fluid were found in patients with the highest total IgE levels, not only in tears but also in serum. This is evidence for a specific, local allergic reaction in these patients. Most positive reactions were to perennial allergens, particularly house dust mites, cat epithelium and Bermuda grass. This fact is in harmony with the lack of season-linked symptoms in most patients in this geographical area.     

Enhancement of murine IgE antibody detection by IgG removal

RATIONALE: Although animal models for the study of allergic reactions are desirable, the use of mice has been hindered by the lack of sufficiently sensitive in vitro immunoglobulin epsilon (IgE) antibody assays. The aim of this study was to enhance IgE antibody measurements by immunoglobulin gamma (IgG) depletion. METHODS: Seven- to eight-week-old female mice of four strains (C3H/HeJ, CBA/J, C57Bl/6J, and Balb/c) were immunized (20 mice/group) with shrimp or peanut extracts using Al(OH)(3) as adjuvant. Following immunization, animals were sacrificed by exsanguination and the sera of each group pooled. Initial measurements of IgE antibody levels by enzyme-linked immunosorbent assay (ELISA) were relatively low; IgG and IgE reactivity patterns by immunoblot were similar. Thus, sera from shrimp or peanut immunized mice were depleted of IgG (absorbed 3-6 times with immobilized protein G) and then tested for IgE antibody to shrimp or peanut allergen. RESULTS: A 3- to 5-fold increase in IgE antibody reactivity as measured by ELISA was demonstrated when >80-90% of the IgG was removed. This increase in detection of allergen-specific IgE occurred in sera from all mouse strains and to all allergens tested. In addition, reactivity of IgE antibodies to peanut or shrimp allergens by immunoblot increased visually approximately 4- to 10-fold. CONCLUSIONS: These studies indicate that allergen-specific IgG antibodies, which may be in more than 100-fold excess to IgE antibodies, interferes with detection of allergen-specific IgE, probably by competitive binding to allergenic epitopes. Substantial depletion of IgG antibodies (>80%) result in a significant increase in the sensitivity of the antibody measurements.     

Evaluation of Oriton IgE, a new kit for measurement of allergen specific IgE antibodies]

To determine whether Oriton IgE kit, a new kit for the measurement of allergen-specific IgE antibodies, is useful in screening allergen-specific antibody, we measured the titers of IgE antibodies against 11 different allergens (house dust 2, Dermatophagoides farinae, Japanese cedar, ragweed pollen, egg white, milk, cat epithelium, dog epithelium, Candida, Alternaria and Aspergillus) with the Oriton IgE kit, and the results were compared to those of intradermal tests and RAST in 103 allergic patients and 10 normal subjects. There was a clear correlation between IgE antibody titers measured by the Oriton IgE kit and the RAST. The correlation coefficient was 0.76 (p less than 0.01) and the total correspondence rate was 85.9%. We also found strong correlation between the Oriton IgE kit and RAST in IgE antibody titer against 5 different allergens, Dermatophagoides farinae, Japanese cedar, ragweed pollen, egg white and Candida. The correlation coefficient was over 0.70. The correspondence rate, sensitivity and specificity of the Oriton IgE kit to intradermal tests was 71.8%, 45.3% and 87.8% respectively. The sensitivity of the Oriton IgE kit was slightly higher, while the specificity was slightly higher in RAST, although the differences were not statistically significant between these methods. Correspondence rate of the Oriton IgE kit was similar to that of RAST. These results suggested that the Oriton IgE kit is useful in screening allergen specific IgE antibodies.     

Evaluation of allergen-specific IgE antibodies by a newly developed mast allergy system

MAST, which stand for multiple antigen simultaneous test, uses enzyme-linked anti-human IgE and chemiluminogenic substate to determine IgE. This system is characterized by simultaneous analysis of multiple allergen items, up to 35, together with total IgE determination. We evaluated usefulness of this MAST system using 191 serum samples obtained from patients with bronchial asthma, allergic rhinitis and/or atopic dermatitis. It was found that there were statistically significant correlations between IgE antibody quantification by MAST and RAST in 24 out of 35 allergen items, with correlation coefficients more than r = 0.60. These included Dermatophagoides farinae and pteronyssinus, Japanese cedar pollen, orchard grass, Alternaria, Candida as inhalant allergens; egg white, milk, soybeans, wheat and rice as food allergens. It was also evaluated how many allergen-specific IgE antibodies could be detected in one serum sample. More than six allergen-specific IgE antibodies were simultaneously detected in 33% of 191 cases, indicating the importance of multiple-allergen analysis. These results indicate the clinical usefulness of the MAST allergy system in detecting IgE antibodies in allergic subjects.     

Some immunological aspects of patients with rhinitis in Lebanon

Background: Hitherto immunological determinates in Lebanese patients with rhinitis have not been investigated.

Objective: To identify causative allergens in Lebanese patients with allergic rhinitis and determine possible correlation's among serum allergen specific antibody, polyclonal IgE, IL-4, IL-5 and peripheral eosinophil levels.

Methods: One hundred and thirteen patients with a long lasting history of nasal obstruction, rhinorrhea, sneezing and nasal itching were investigated. Serum allergen specific antibodies using a panel of 10 potential allergens, IL-4 and IL-5 levels were determined by enzyme immunoassays. Polyclonal IgE levels were estimated by an immunochromatographic assay and eosinophil counts by a Coulter STKS counter.

Results: Based on the presence of serum allergen-specific IgE antibodies, 74 patients were considered to have an allergic etiology. Polyclonal IgE levels were elevated in 41 of the 74 allergic rhinitis patients while the other 33 patients had normal serum levels. In the remaining 39 specific IgE antibody-negative patients, 32 had normal, and 7 had elevated, polyclonal IgE levels. IgE specific antibodies to more than one allergen were detected in 59 of 74 patients. The most common causative allergens were mite, Dermatophagoides pteronyssinus, Dpt (83.8%) and Dermatophagoides farinae, Df (78.4%). Analysis of the data indicated that elevated polyclonal IgE levels correlated with the concentration of serum specific IgE antibodies and the number of the detected causative allergens per patient. Fifty-nine of 74 allergic rhinitis patients had elevated IL-4 levels and 44 had elevated IL-5 levels. The number of allergic patients with both elevated IL-4 and IL-5 levels was 24. Finally, only 9 allergic rhinitis patients had peripheral eosinophilia.

Conclusion: Mite Dpt and Df were the most common causative agents of allergic rhinitis in the Lebanese group studied. A prerequisite for Specific Immunotherapy is the identification of the causative allergen. Determinations of polyclonal IgE level and peripheral eosinophil count alone, as an aid to diagnosis are insufficient and may be misleading. On the other hand, determination of all the parameters studied in conjunction appears to be of diagnostic value.     

Molecular determinants of allergen-induced effector cell degranulation

BACKGROUND: Allergen-induced effector cell degranulation is a key event in allergic inflammation and leads to early-phase symptoms, such as allergic rhinitis, conjunctivitis, urticaria, or bronchial asthma. OBJECTIVE: We sought to study molecular determinants of effector cell degranulation using a monoclonal IgE antibody specific for a peptide epitope of one of the most important respiratory allergens, the major grass pollen allergen Phl p 1, as a model system. METHODS: A hybridoma cell line producing a monoclonal IgE antibody against a Phl p 1-derived peptide, P1, was established by means of immunization of mice and used to sensitize rat basophil leukemia cells, which were exposed to P1 monomer, P1 dimer, and P1 polymer. RESULTS: It is demonstrated that the number of IgE epitopes on an allergen molecule and the concentration of allergen-specific IgE antibodies determine the extent of degranulation. The P1 monomer did not cause mediator release and prevented degranulation induced by polymeric P1. CONCLUSION: Our results suggest that the number of IgE epitopes on an allergen molecule determines its allergenic activity and explains why increases of allergen-specific IgE levels make patients more sensitive to allergens. Allergen-derived monomeric structures isolated by means of combinatorial chemistry might be used to develop new therapeutic strategies for allergy. CLINICAL IMPLICATIONS: Our study reveals molecular factors that determine the immediate allergenic activity of allergens and hence influence clinical sensitivity to these allergens.     

SOME IMMUNOLOGICAL ASPECTS OF PATIENTS WITH RHINITIS IN LEBANON

ABSTRACT

Background: Hitherto immunological determinates in Lebanese patients with rhinitis have not been investigated.

Objective: To identify causative allergens in Lebanese patients with allergic rhinitis and determine possible correlation's among serum allergen specific antibody, polyclonal IgE, IL-4, IL-5 and peripheral eosinophil levels.

Methods: One hundred and thirteen patients with a long lasting history of nasal obstruction, rhinorrhea, sneezing and nasal itching were investigated. Serum allergen specific antibodies using a panel of 10 potential allergens, IL-4 and IL-5 levels were determined by enzyme immunoassays. Polyclonal IgE levels were estimated by an immunochromatographic assay and eosinophil counts by a Coulter STKS counter.

Results: Based on the presence of serum allergen-specific IgE antibodies, 74 patients were considered to have an allergic etiology. Polyclonal IgE levels were elevated in 41 of the 74 allergic rhinitis patients while the other 33 patients had normal serum levels. In the remaining 39 specific IgE antibody-negative patients, 32 had normal, and 7 had elevated, polyclonal IgE levels. IgE specific antibodies to more than one allergen were detected in 59 of 74 patients. The most common causative allergens were mite, Dermatophagoides pteronyssinus, Dpt (83.8%) and Dermatophagoides farinae, Df (78.4%). Analysis of the data indicated that elevated polyclonal IgE levels correlated with the concentration of serum specific IgE antibodies and the number of the detected causative allergens per patient. Fifty-nine of 74 allergic rhinitis patients had elevated IL-4 levels and 44 had elevated IL-5 levels. The number of allergic patients with both elevated IL-4 and IL-5 levels was 24. Finally, only 9 allergic rhinitis patients had peripheral eosinophilia.

Conclusion: Mite Dpt and Df were the most common causative agents of allergic rhinitis in the Lebanese group studied. A prerequisite for Specific Immunotherapy is the identification of the causative allergen. Determinations of polyclonal IgE level and peripheral eosinophil count alone, as an aid to diagnosis are insufficient and may be misleading. On the other hand, determination of all the parameters studied in conjunction appears to be of diagnostic value.     

Total and allergen-specific IgE in relation to allergic response pattern following bone marrow transplantation.

Total and allergen-specific serum IgE were measured in relation to allergic response pattern before and after bone marrow transplant (BMT) in seven sibling donor/recipient pairs. Two non-atopic recipients developed persistently raised total serum IgE levels but no apparent allergic response after BMT from non-atopic donors; three non-atopic recipients showed raised total serum IgE after BMT, with allergen-specific IgE to the same allergens as their respective atopic donors. A penicillin-tolerant recipient showed clinical sensitivity and specific IgE to penicillin after BMT from a penicillin-sensitive donor, but with this case both donor and recipient showed raised serum IgE levels. One atopic recipient showed decreased total IgE after BMT from a mildly atopic donor. These allergic response patterns could occur as a result of repopulation in the recipient with IgE-specific T lymphocytes having similar regulatory influences as in the donor. The pattern of acquired responses would also be consistent with reconstitution by primed B lymphocytes of donor origin.     

Detection of allergen-specific IgE in tears of grass pollen-allergic patients with allergic rhinoconjunctivitis

Background Allergic conjunctivitis is a common symptom amongst Type I (IgE-mediated) allergic diseases; and mosl frequently seen as rhinoconjunctivitis. However, the site of production and the significance of allergen specific IgE needs further elucidation. Objective We investigated whether the presence of IgE in tears of grass pollen allergic patients correlated with disease and clinical symptoms, whether the IgE binding pattern to the different grass pollen antigens was diflferent in sera and tears, and whether IgA antibodies to grass pollen allergens were present in tears. Finally, we looked whether specific IgE was produced locally or was exudated from serum. Methods Sera from 44 grass pollen allergic patients suffering from either allergic rhinitis (n=11) or allergic rhinoconjunctivitis (n= 33) and from healthy controls (n= l) were used for the experiments. Binding of specific IgE and IgA antibodies to the differyent groups of grass pollen allergens (Phleum pratense) was evaluated by means of immunobtotting. Results Specific IgE was detected in sera as well as in tears of allergic patients, whereby tear-derived allergen-specific IgE exerted similar specificities to the corresponding IgE from serum. The correlation between symptoms of ocular allergy and the presence of allergen-specific IgE in tears was highly significant (P 0.0001). In contrast, only a poor correlation was found between specific and/or total IgE in sera and the manifestation of ocular allergy (P = 0.73). Conclusion Allergen-specific IgE antibodies in tears seem to be produced locally rather than exsudated from serum. IgE in tears seems to be responsible for allergic conjunctivitis. IgA in tears cannot exert a protective function since the IgA antibodies recognize different antigens in a grass pollen (Phleum pratense) extract than IgE antibodies. The highly significant correlation between allergic conjunctivitis and the presence of specific tear IgE emphasizes the diagnostic value of immunoblots with tear IgE, especially in cases in which serum provides inconclusive results.     

The critical role of allergen-specific IgE,IgG4 and IgA antibodies in the tolerance of IgE-mediated food sensitisation in primary school children

Primary objective. There are about 6% of children who are either intolerant to or lose their ability to tolerate food allergens, resulting in the development of food hypersensitivity. The hypothesis that increase in food allergen-specific IgE antibody level is associated with the decrease in the levels of food allergen-specific IgG4 and IgA antibodies was used as a biomarker of food tolerance. Methods & Procedures. The Modified International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire (added gastrointestinal allergy questions) and Phadiatop infant test were used to screen one hundred 6–8-year-old allergic school children. Food allergen-specific IgE, IgG and IgA antibodies were measured by using the Phadia ImmunoCAP system radioabsorbent test (RAST). Immunoglobin E antibodies to common aeroallergens, were also detected by enzyme-linked immunosorbent assay. Main outcome. The level of analysed food specific-IgE antibody was obviously higher in the study population. Sensitivity to dust mites among the children was nearly 90%, and that to cockroach was 47%. Egg white-, cow's milk-, α-lactoalbumin-, β-lactoglobulin- and casein-specific IgG4/IgE and IgA/IgE ratios were lower in the atopic school children but not in the tropomysin-, mango- and kiwi-sensitive participants. Conclusion. The level of cow's milk- and egg white-specific IgE antibody still remained high along with a decrease in the specific IgG4/IgE and IgA/IgE ratios in our study population. Therefore, allergen-specific IgG4 and IgA antibodies are important biomarkers of tolerance establishment, and failure to establish tolerance to food allergens may be related to the regulation of the inhalant allergens encountered in late childhood stages.     

A novel liquid-phase enzyme immunoassay AlaSTAT for IgE antibody determination

To determine whether a novel liquid-phase enzyme immunoassay AlaSTAT for allergen-specific IgE antibody determination can be used to measure the absolute amounts of serum IgE antibodies, we examined the amounts of anti-house dust (HD) and anti-mite IgE antibodies in sera of 32 HD-sensitized allergic asthmatics and 14 normal subjects by this immunoassay. The amounts of anti-mite IgE antibody in serum measured by this immunoassay were found to be consistent with those assessed by the difference in serum total IgE proteins before and after the absorption with mite allergen (the value determined by this immunoassay was 113% of the latter one, n = 4). Neither nonspecific IgE protein (50 to 10000 IU/ml) nor the heat-inactivated blocking serum affected the measurement of allergen-specific IgE antibody by the liquid-phase immunoassay. There were strong correlations between the values of anti-HD and anti-mite IgE antibodies by RAST and those by AlaSTAT (r = 0.90, p less than 0.001 and r = 0.86, p less than 0.001, n = 46, respectively). Our results indicate that the commercially available liquid-phase allergen-specific IgE enzyme immunoassay can be used to measure the absolute amounts of serum IgE antibodies without interference of nonspecific IgE protein or IgG blocking antibody.     

Comparison of VIDAS Stallertest and Pharmacia CAP assays for detection of specific IgE antibodies in allergic children

In vitro determination of specific IgE antibodies in serum is the most frequently used method, besides the skin test, for diagnosing allergies. Standardized and reproducible assays of specific IgE antibodies contribute to the quality of diagnosis and treatment of allergic disease. This study compared the results and performance characteristics of the Pharmacia CAP system and a new specific IgE method using the VIDAS Stallertest (manufactured by bioMériux). To evaluate their clinical efficiency, the results of the CAP and VIDAS Stallertest assays were compared with skin prick test (SPT) results. After allergic patients completed SPTs, serum samples were collected and CAP and VIDAS Stallertest assays were performed to determine specific IgEs for Dermatophagoides farinae, D. pteronyssinus, cockroach, and alternaria. For egg and milk, we measured only the correlation between the 2 in vitro assays. When SPT was used as a reference standard, the sensitivity and specificity of the CAP assay was a little higher in respect to all inhalant allergens. There were significant correlations between the results of VIDAS Stallertest and CAP assays for IgE antibodies to inhalant and food allergens. This study indicates that the VIDAS Stallertest and Pharmacia CAP assays are feasible and replicable for measuring allergen-specific IgE.     

Possible modes of allergen-specific sensitization and boosting in an atopic child

Several studies document that allergen-specific IgE levels are boosted by allergen contact via the respiratory tract in allergic patients. Only few data are available on whether other routes of allergen contact have an influence on systemic IgE responses. We report the case of a boy who developed egg allergy after heavy consumption of eggs by the mother during pregnancy and breast feeding. In contrast to other children who outgrow egg allergy during the first years of life, the boy experienced further dramatic increases in hen egg-specific IgE antibodies after prolonged consumption of ostrich eggs containing cross-reactive allergens. IgE antibodies to most of the important respiratory allergens remained either low or not detectable. The dramatic increases in hen egg-specific IgE antibody levels after oral intake of allergens demonstrate that systemic IgE responses in allergic patients can be strongly boosted by allergen contact via routes other than the respiratory tract.     

IgE antibody-specific activity in human allergic disease

IgE antibody concentration, affinity, clonality and specific activity (also known as the allergen-specific IgE to total IgE ratio) influence the translation of IgE responses into clinically evident allergic symptoms following allergen exposure. Reported IgE-specific activity levels >3–4% place allergic individuals undergoing anti-IgE (Omalizumab^®) therapy at a disadvantage for poor resolution of their allergy symptoms following manufacturer’s recommended dosing schemes. We investigated the hypothesis that the specific activity of the IgE antibody response is highly variable with respect to age, allergen specificity and an individual’s total serum IgE level. Second, we investigated whether the IgE-specific activity level influences the extent and rate of loss of effector cell mediator release. IgE-specific activity distributions were plotted against age, allergen specificity and total serum IgE using 18,950 paired total IgE and allergen-specific IgE antibody data obtained from the analysis of sera from 3,614 allergic subjects and covering 182 allergen specificities. The fraction of specific IgE antibody of the total serum IgE was dependent on age of the individual, epitope specificity (clonality) and total serum IgE. The youngest group of allergic individuals with the lowest total serum IgE levels tended to have the highest allergen-specific IgE to total IgE ratios. Hymenoptera venom (54%), peanut (33%) and milk (27%) were the three allergen specificities that elicited the highest frequency of IgE-specific activities >4% among sensitized individuals. A prospective double-blind, placebo-controlled clinical study involving anti-IgE treatment of cat-allergic subjects showed IgE-specific activity was remarkably constant over the 16-week course of treatment, despite the up to 8-fold rise in total serum IgE following repetitive Omalizumab^® administration. Changes in specific and total IgE levels paralleled each other in patients receiving anti-IgE therapy. The fastest rate of reduction in cat allergen-induced basophil histamine release following anti-IgE therapy was observed when the cat-specific IgE to total IgE ratio was <2.5%. This reflected the more rapid loss of surface cat-specific IgE antibody with anti-IgE therapy in allergic individuals who displayed a more diverse IgE antibody repertoire. We conclude that IgE-specific activity is an age-, IgE heterogeneity- and total serum IgE-dependent variable that influences the magnitude of effector cell mediator release, and by inference, ultimate allergic symptom induction.     

The relevance of microbial allergens to the IgE antibody repertoire in atopic and nonatopic eczema

BACKGROUND: A propensity to microbial skin infections has been reported in atopic ("high IgE") and nonatopic ("low IgE") forms of eczema. However, the relationship between antimicrobial IgE antibodies and nonatopic disease is unclear. OBJECTIVE: We examined the relevance of microbial allergens to the allergen-specific IgE antibody repertoire in patients with atopic dermatitis. METHODS: Patients with IgE levels of less than 150 IU/mL were stratified according to sensitivity (n = 22) or no sensitivity (n = 27) to 11 common food allergens and aeroallergens. The prevalence and titers of antimicrobial IgE antibodies were compared with those of patients (n = 36) with increased total IgE levels (>150 IU/mL). Skin-derived serum chemokines were also analyzed. RESULTS: Patients with low IgE levels showed decreased disease severity, increased age of onset, a striking female predominance, and a distinct distribution of skin lesions. High titer IgE antibodies (sum of 8 bacterial and fungal allergens = 29.8 +/- 32.6 IU/mL) and multisensitization specific for microbial allergens was characteristic of patients with high IgE levels, with an overall 84% positivity; however, antimicrobial IgE antibodies comprised 3% or less of allergen-specific IgE antibodies. By contrast, antimicrobial IgE antibodies were detected in only 20% of patients with low IgE, and titers were negligible, irrespective of sensitization to common allergens. These patients were monosensitized, and exclusive microbial sensitivity was uncommon (10%). Patients with low IgE with no sensitivity to common allergens had lower levels of serum macrophage inflammatory protein 3alpha compared with their sensitized counterparts. CONCLUSION: Antimicrobial IgE antibodies are uncommon in patients with atopic dermatitis with low IgE levels. CLINICAL IMPLICATIONS: Hypersensitivity to microbial allergens is an unlikely trigger for eczematous eruptions in patients with low IgE levels.     

In vitro assays for the diagnosis of IgE-mediated disorders

Advances in technology have provided new laboratory tools for the quantitation of allergen-specific IgE antibodies in serum and on the surface of basophils. This review examines the evolution from qualitative IgE antibody assays of the late 1960s to the present-day, third-generation, automated and quantitative allergen-specific IgE assays. The latest technology trend is toward microarrays in which crude or purified native and recombinant allergens can be spotted in microdot arrays on silica chips to permit extensive panels of specific IgE measurements to be performed with small quantities of serum. Although these technologies hold promise, their diagnostic performance requires further assessment once their technical details have been optimized. Potential abuses of this newer IgE antibody technology include the use of allergosorbent specificities (eg, especially food and drugs) that lack validation, application of IgE antibody measurements in the diagnosis of non-IgE-dependent disorders (eg, aspirin sensitivity), and modification of IgE antibody assays to measure food-specific IgG antibody for which there is no clinical indication. Basophil mediator release assays have evolved to include flow cytometric methods that can quantitatively detect the presence of cell surface-bound allergen-specific IgE antibodies. Assays for histamine and leukotriene C 4 released after in vitro basophil activation are now more accurate and standardized. Current analytic methods for IgE antibodies provide more quantitative and reproducible measurements of IgE than ever before, although still with less sensitivity that traditional skin testing. The current challenge is to translate the quantitative IgE antibody results into a more accurate diagnosis of allergic disease.