IgE Binding Sites Research Articles

High-resolution crystal structure and IgE recognition of the major grass pollen allergen Phl p 3.

Group 2 and 3 grass pollen allergens are major allergens with high allergenic activity and exhibit structural similarity with the C-terminal portion of major group 1 allergens. In this study, we aimed to determine the crystal structure of timothy grass pollen allergen, Phl p 3, and to study its IgE recognition and cross-reactivity with group 2 and group 1 allergens. The three-dimensional structure of Phl p 3 was solved by X-ray crystallography and compared with the structures of group 1 and 2 grass pollen allergens. Cross-reactivity was studied using a human monoclonal antibody which inhibits allergic patients' IgE binding and by IgE inhibition experiments with patients' sera. Conformational Phl p 3 IgE epitopes were predicted with the algorithm SPADE, and Phl p 3 variants containing single point mutations in the predicted IgE binding sites were produced to analyze allergic patients' IgE binding. Phl p 3 is a globular β-sandwich protein showing structural similarity to Phl p 2 and the Phl p 1-C-terminal domain. Phl p 3 showed IgE cross-reactivity with group 2 allergens but not with group 1 allergens. SPADE identified two conformational IgE epitope-containing areas, of which one overlaps with the epitope defined by the monoclonal antibody. The mutation of arginine 68 to alanine completely abolished binding of the blocking antibody. This mutation and a mutation of D13 in the predicted second IgE epitope area also reduced allergic patients' IgE binding. Group 3 and group 2 grass pollen allergens are cross-reactive allergens containing conformational IgE epitopes. They lack relevant IgE cross-reactivity with group 1 allergens and therefore need to be included in diagnostic tests and allergen-specific treatments in addition to group 1 allergens.

A range of Cℇ3-Cℇ4 interdomain angles in IgE Fc accommodate binding to its receptor CD23.

The antibody IgE plays a central role in allergic disease, functioning principally through two cell-surface receptors: FcℇRI and CD23. FcℇRI on mast cells and basophils mediates the immediate hypersensitivity response, whilst the interaction of IgE with CD23 on B cells regulates IgE production. Crystal structures of the lectin-like `head' domain of CD23 alone and bound to a subfragment of IgE consisting of the dimer of Cℇ3 and Cℇ4 domains (Fcℇ3-4) have recently been determined, revealing flexibility in the IgE-binding site of CD23. Here, a new crystal form of the CD23-Fcℇ3-4 complex with different molecular-packing constraints is reported, which together with the earlier results demonstrates that conformational variability at the interface extends additionally to the IgE Fc and the quaternary structure of its domains.

Structural analysis of the endogenous glycoallergen Hev b 2 (endo-β-1,3-glucanase) fromHevea brasiliensisand its recognition by human basophils

Endogenous glycosylated Hev b 2 (endo-β-1,3-glucanase) from Hevea brasiliensis is an important latex allergen that is recognized by IgE antibodies from patients who suffer from latex allergy. The carbohydrate moieties of Hev b 2 constitute a potentially important IgE-binding epitope that could be responsible for its cross-reactivity. Here, the structure of the endogenous isoform II of Hev b 2 that exhibits three post-translational modifications, including an N-terminal pyroglutamate and two glycosylation sites at Asn27 and at Asn314, is reported from two crystal polymorphs. These modifications form a patch on the surface of the molecule that is proposed to be one of the binding sites for IgE. A structure is also proposed for the most important N-glycan present in this protein as determined by digestion with specific enzymes. To analyze the role of the carbohydrate moieties in IgE antibody binding and in human basophil activation, the glycoallergen was enzymatically deglycosylated and evaluated. Time-lapse automated video microscopy of basophils stimulated with glycosylated Hev b 2 revealed basophil activation and degranulation. Immunological studies suggested that carbohydrates on Hev b 2 represent an allergenic IgE epitope. In addition, a dimer was found in each asymmetric unit that may reflect a regulatory mechanism of this plant defence protein.

Antigenic Determinants On Der p 1 Identified By Mutagenesis Analysis Based On The Structure Of Allergen-Antibody Complexes

S U N D A Y 568 Antigenic Determinants On Der p 1 Identified By Mutagenesis Analysis Based On The Structure Of Allergen-Antibody Complexes Dr. Anna Pomes, PhD, FAAAAI, Ms. Jill Glesner, Ms. Lisa D. Vailes, Dr. Wladek Minor, PhD, Dr. Maksymilian Chruszcz, PhD, Dr. Martin D. Chapman, PhD, FAAAAI; Indoor Biotechnologies, Inc., Charlottesville, VA, University of Virginia, Charlottesville, VA, University of South Carolina, Columbia, SC. RATIONALE: Der p 1 is a major dust mite allergen, cross-reactive with the homolog Der f 1. Two structures of Der p 1 in complex with Fab fragments of either monoclonal antibody (mAb) 4C1 or 5H8, that partially inhibit IgE antibody binding, were solved by X-ray crystallography. The goal was to identify the residues involved in allergen-antibody interactions, and IgE antibody binding sites by site-directed mutagenesis. METHODS: Single or multiple mutants of Der p 1 residues involved in mAb 5H8 and/or 4C1 binding were expressed in Pichia pastoris and purified by affinity chromatography. IgE and mAb binding assays were performed by ELISA using sera from mite allergic patients. RESULTS: The capacity of the mutants to bind the mAbs was reduced up to 40 times for 5H8 and almost completely for 4C1, depending on the mutation, and according to the displacement of the mAb direct binding or inhibition curves. This result confirmed the importance of specific residues in the allergen-antibody interaction. Specific mutations in each epitope also reduced IgE antibody binding in different degrees (up to 40%) depending on the patient’s serum and the mutation, and proved an overlap between IgE and mAb binding sites. CONCLUSIONS: Site-directed mutagenesis analysis of residues from epitopes identified by X-ray crystallography revealed mechanisms of antibody recognition. Amino acids important for allergen-antibody interaction were identified for the expression of allergen mutants with reduced IgE antibody reactivity with potential use for immunotherapy.

Conformational plasticity at the IgE-binding site of the B-cell receptor CD23

IgE antibodies play a central role in allergic disease. They recognize allergens via their Fab regions, whilst their effector functions are controlled through interactions of the Fc region with two principal cell surface receptors, FcɛRI and CD23. Crosslinking of FcɛRI-bound IgE on mast cells and basophils by allergen initiates an immediate inflammatory response, while the interaction of IgE with CD23 on B-cells regulates IgE production. We have determined the structures of the C-type lectin “head” domain of CD23 from seven crystal forms. The thirty-five independent structures reveal extensive conformational plasticity in two loops that are critical for IgE binding.

Enhanced cell‐binding by allergen multimers: how complex is it?

Allergic diseases are the most common chronic disease of the western world, costing $7.8 billion per year in lost productivity and medical care in Australia alone.1 IgE is central to the immunopathogenesis of allergic diseases and important advances are now being made on multiple fronts of IgE research. In particular, two groups independently invested in the generation of IgE reporter mice to address the vexing question of the route of development of the elusive IgE+ B cell.2, 3 Two new anti-IgE mAb targeting membrane IgE and cell-bound IgE have the potential to deplete the cellular source of IgE.4, 5 These could be candidates for alternative anti-IgE treatment options with advantages over current anti-IgE therapy (OmalizumAb), which depletes free serum IgE. Researchers are still intrigued by the modes of interaction of IgE with allergen, and with both its receptors; the high affinity FceR1 on mast cells and basophils, and the low affinity, C-type lectin, IgE receptor, CD23,6 on B cells and monocytes (Figure 1a and b). A new approach to the study of the complexity of these interactions was recently reported by Reginald et al.7 on page 167 of this issue.

Immunoglobulin E and G4 epitopes of the major allergen of birch pollen Bet v 1 share residues critical for antibody binding

Background Millions of patients with allergy to birch pollen develop clinically cross-reactive IgE against Bet v 1-like proteins in plant foods. Specific immunotherapy (SIT) with birch pollen extracts induces the biosynthesis of Bet v 1-specific immunoglobulin (Ig)G4. IgG4 is believed to act as a blocking antibody preventing IgE binding to Bet v 1, thus alleviating allergic symptoms. Only little information on the location and relationship of IgE and IgG4 binding sites of Bet v 1 is available. In this study we seek to identify epitopes of IgE and IgG4 antibodies on Bet v 1.

Safety of engineered allergen-specific immunotherapy vaccines

The purpose of the review is to summarize and comment on recent developments regarding the safety of engineered immunotherapy vaccines. In the last 2 years, several studies were published in which allergy vaccines were developed on the basis of chemical modification of natural allergen extracts, the engineering of allergen molecules by recombinant DNA technology and synthetic peptide chemistry, allergen genes, new application routes and conjugation with immune modulatory molecules. Several studies exemplified the general applicability of hypoallergenic vaccines on the basis of recombinant fusion proteins consisting of nonallergenic allergen-derived peptides fused to allergen-unrelated carrier molecules. These vaccines are engineered to reduce both, immunoglobulin E (IgE) as well as allergen-specific T cell epitopes in the vaccines, and thus should provoke less IgE and T-cell-mediated side-effects. They are made to induce allergen-specific IgG antibodies against the IgE-binding sites of allergens with the T-cell help of the carrier molecule. Several interesting examples of allergy vaccines with potentially increased safety profiles have been published. The concept of fusion proteins consisting of allergen-derived hypoallergenic peptides fused to allergen-unrelated proteins that seems to be broadly applicable for a variety of allergens appears to be of particular interest because it promises not only to reduce side-effects but also to increase efficacy and convenience of allergy vaccines.

Histamine-releasing factor (HRF) in asthma and atopic dermatitis (177.16)

Abstract Effects of monomeric IgE on mast cell biology exhibit vast heterogeneity, depending on IgE used. Highly cytokinergic (HC) IgEs can induce many activation events such as degranulation, cytokine production, etc, whereas poorly cytokinergic (PC) IgEs can induce only weak survival promotion. Because of the reminiscence to the heterogeneity in the ability of IgE molecules to prime basophils in response to HRF, this dichotomy has led us to find that a subset of IgEs bind to HRF via their Fab portions; the IgE-binding sites were mapped to two different sites of HRF, indicating that dimeric HRF can cross-link IgE-bound FcϵRI; N19 and H3 peptides blocked HRF-Ig interactions; administration of these inhibitors drastically reduced airway inflammation in asthma models, implying that blockade of HRF-Ig interactions may represent a potential prophylactic and therapeutic strategy for the treatment of asthma. Importantly, most HC, but no PC, IgEs exhibit polyreactivity to HRF and other autoantigens. Interestingly, sera from atopic dermatitis (AD) patients showed increased reactivity to autoantigens and increased levels of HRF. Some AD patients, but not healthy individuals, had high serum levels of HRF-reactive IgE. AD sera with high titers of autoreactive IgE could induce increased IL-8 secretion from human mast cells. Collectively, these results show support the autoimmune mechanism in the pathogenesis of atopic dermatitis.

Reduced in vitro T‐cell responses induced by glutaraldehyde‐modified allergen extracts are caused mainly by retarded internalization of dendritic cells

Although allergen-specific immunotherapy is a clinically effective therapy for IgE-mediated allergic diseases, the risk of IgE-mediated adverse effects still exists. For this reason, chemically modified allergoids have been introduced, which may destroy IgE-binding sites while T-cell activation should be retained. The aim of the study was to analyse the differences between intact allergens and differently modified/aggregated allergoids concerning their internalization as well as T-cell and basophil activation. For this purpose human monocyte-derived immature dendritic cells (DC) were incubated with Phleum pratense or Betula verrucosa pollen extract or with the corresponding allergoids, modified with formaldehyde or glutaraldehyde. After an additional maturation process, the antigen-loaded mature DC were co-cultured with autologous CD4(+) T cells. Allergenicity was tested by leukotriene release from basophils. In addition, the uptake of intact allergens and allergoids by immature DC was analysed. The proliferation of, as well as the interleukin-4 (IL-4), IL-10, IL-13 and interferon-γ production by, CD4(+) T cells which had been stimulated with glutaraldehyde allergoid-treated DC was reduced compared with CD4(+) T cells stimulated with intact allergen-treated or formaldehyde allergoid-treated DC. In line with this, glutaraldehyde-modified allergoids were more aggregated and were internalized more slowly. Furthermore, only the allergoids modified with glutaraldehyde induced a decreased leukotriene release by activated basophils. These findings suggest that IgE-reactive epitopes were destroyed more efficiently by modification with glutaraldehyde than with formaldehyde under the conditions chosen for these investigations. Glutaraldehyde-modified allergoids also displayed lower T-cell stimulatory capacity, which is mainly the result of greater modification/aggregation and diminished uptake by DC.

Subtropical grass pollen allergens are important for allergic respiratory diseases in subtropical regions

BackgroundGrass pollen allergens are a major cause of allergic respiratory disease but traditionally prescribing practice for grass pollen allergen-specific immunotherapy has favoured pollen extracts of temperate grasses. Here we aim to compare allergy to subtropical and temperate grass pollens in patients with allergic rhinitis from a subtropical region of Australia.MethodsSensitization to pollen extracts of the subtropical Bahia grass (Paspalum notatum), Johnson grass (Sorghum halepense) and Bermuda grass (Cynodon dactylon) as well as the temperate Ryegrass (Lolium perenne) were measured by skin prick in 233 subjects from Brisbane. Grass pollen-specific IgE reactivity was tested by ELISA and cross-inhibition ELISA.ResultsPatients with grass pollen allergy from a subtropical region showed higher skin prick diameters with subtropical Bahia grass and Bermuda grass pollens than with Johnson grass and Ryegrass pollens. IgE reactivity was higher with pollen of Bahia grass than Bermuda grass, Johnson grass and Ryegrass. Patients showed asymmetric cross-inhibition of IgE reactivity with subtropical grass pollens that was not blocked by temperate grass pollen allergens indicating the presence of species-specific IgE binding sites of subtropical grass pollen allergens that are not represented in temperate grass pollens.ConclusionsSubtropical grass pollens are more important allergen sources than temperate grass pollens for patients from a subtropical region. Targeting allergen-specific immunotherapy to subtropical grass pollen allergens in patients with allergic rhinitis in subtropical regions could improve treatment efficacy thereby reducing the burden of allergic rhinitis and asthma.

Three-Dimensional Modelling of Honeybee Venom Allergenic Proteases: Relation to Allergenicity

Api SI and Api SII are serine proteases of the honeybee venom containing allergenic determinants. Each protease consists of two structural modules: an N-terminal CUB (Api SI) or a clip domain (Api SII) and a C-terminal serine protease-like (SPL) domain. Both domains are connected with a linker peptide. The knowledge about the structure and function of Api SI and Api SII is limited mainly to their amino acid sequences. We constructed 3-D models of the two proteases using their amino acid sequences and crystallographic coordinates of related proteins. The models of the SPL domains were built using the structure of the prophenoloxidase-activating factor (PPAF)-II as a template. For modelling of the Api SI CUB domain the coordinates of porcine spermadhesin PSP-I were used. The models revealed the catalytic and substrate-binding sites and the negatively charged residue responsible for the trypsin-like activity. IgE-binding and antigenic sites in the two allergens were predicted using the models and programs based on the structure of known epitopes. Api SI and Api SII show structural and functional similarity to the members of the PPAF-II family. Most probably, they are part of the defence system of Apis mellifera.

A Soluble Form of the High Affinity IgE Receptor, Fc-Epsilon-RI, Circulates in Human Serum

Soluble IgE receptors are potential in vivo modulators of IgE-mediated immune responses and are thus important for our basic understanding of allergic responses. We here characterize a novel soluble version of the IgE-binding alpha-chain of Fc-epsilon-RI (sFcεRI), the high affinity receptor for IgE. sFcεRI immunoprecipitates as a protein of ∼40 kDa and contains an intact IgE-binding site. In human serum, sFcεRI is found as a soluble free IgE receptor as well as a complex with IgE. Using a newly established ELISA, we show that serum sFcεRI levels correlate with serum IgE in patients with elevated IgE. We also show that serum of individuals with normal IgE levels can be found to contain high levels of sFcεRI. After IgE-antigen-mediated crosslinking of surface FcεRI, we detect sFcεRI in the exosome-depleted, soluble fraction of cell culture supernatants. We further show that sFcεRI can block binding of IgE to FcεRI expressed at the cell surface. In summary, we here describe the alpha-chain of FcεRI as a circulating soluble IgE receptor isoform in human serum.

In-vitro-Diagnostik und molekulare Grundlagen von IgE-vermittelten Nahrungsmittelallergien

Detection of allergen-specific IgE represents the most important tool for in vitro diagnostic testing of food allergy. Applied methods vary in design (single allergen sources or mixtures, panel tests, single allergen components) and diagnostic efficacy. High specific IgE to hens egg, cows milk, peanut and fish is associated with an increased risk for clinical reactions, but rarely supersedes oral challenge tests. Cellular tests with basophil leukocytes, demonstrating IgE-mediated sensitizations indirectly, are useful only in selected cases. Particular protein families (i.e. Bet v 1 homologs, lipid transfer proteins and profilins) consist of allergenic molecules with similar sequence and structure. Their shared IgE binding sites form the basis of cross-reactivity. Cross-reactive carbohydrate determinants (CCD), frequently from plant origin, can also bind IgE being rarely clinically relevant. Allergy to plants (i.e. tree nuts, fruits, legumes) and animals (cows milk, hens egg, fish) is diagnosed with extracts, if their quality is sufficient. Detecting IgE to single allergenic components allows molecule-specific diagnoses, their value varies for each allergen source and single allergen component. Allergen-specific IgE detections are indicated in case of suspected food-allergic reactions despite uncertain history and skin tests, sensitizations to foods not applicable for skin testing, severe reactions to foods, conditions hampering skin testing or its interpretation, and in children. Interpreting should consider incorrect results due to inferior reagents or laboratory errors and clinically irrelevant results due to highly elevated total IgE, low assay thresholds or cross-reactive allergens (errors of interpretation). Positive test results indicate allergen-specific sensitizations, being clinically relevant only in case of corresponding symptoms. The following methods are not useful for diagnosing food allergy: bioresonance, electroacupuncture, kinesiology, cytotoxic food allergy test (methods without validity and/or evidence), lymphocyte stimulation test, food-specific IgG and IgG4 (methods with invalid interpretation).

Vaccine progress

Despite the recent development of new anti-mould agents, there remains a significant incidence of invasive aspergillosis in the most immunocompromised hosts and the response to these agents is still dismal. There is a need for a different approach: prevention by vaccination. We have demonstrated that a hyphal sonicate of Aspergillus fumigatus was capable of conferring protection against subsequent invasive pulmonary aspergillosis in corticosteroid immunosuppressed mice. Subcutaneous vaccination was superior to nasal vaccination. Mice exposed intranasally to viable conidia were noted to respond serologically to a 19 kDa protein. This protein was identified as the allergen Asp f 3 by mass spectrometry. Vaccination with recombinant Asp f 3 was protective. Truncated forms of Asp f 3 that lacked either one of the two known IgE binding sites were cloned and also demonstrated protection against aspergillosis. Although all of these recombinant proteins required an adjuvant (TiterMax) for efficacy, a particulate preparation of rAsp f 3 was also found to be protective without requiring adjuvant. At least two T-cell epitopes (11-mer and 13-mer) have been identified in Asp f 3. There are homologues of Asp f 3 in other Aspergillus species as well as in other moulds (Coccidioides posadasii, Penicillium citrinum) and yeasts (Candida albicans, C. boidinii, Saccharomyces cerevisiae). Asp f 3, truncated non-allergenic versions of Asp f 3, and T-cells epitopes of Asp f 3 are potential candidates for vaccines potentially capable of protecting immunocompromised hosts against invasive aspergillosis.

Amino Acid Substitution in Par j 2 Recombinant Allergen and Its Effect on IgE Binding Capacity

Therapeutic attempts to cure allergic diseases reduce symptoms without circumventing the onset of the allergic reaction. Specific immunotherapy (SIT), is the most commonly used treatment. Nevertheless, SIT may account for various adverse events. Therefore, different therapies have been developed in order to treat and prevent allergic reactions. Among these therapies, there is an increased interest in studying recombinant peptides mutated in the IgE binding site. Several studies have shown two major allergens of <i>Parietaria judaica</i> (Pj) named Par j 1 and Par j 2, which have been cloned and characterized by us. In our study we have fragmented the Par j 2 protein in order to determine the major epitopes recognized by human IgE and we used site-directed mutagenesis to identify potential amino acid residues involved in IgE binding. The IgE binding activity of the recombinant peptides was tested and the results showed that site-specific mutagenesis at positions K41, T42, T43, and C52 caused a loss of IgE binding. The goal of this work is to synthesize molecules which can induce a protective immune response against Pj. These molecules will be used in immunotherapy in order to create new vaccines for the treatment of Parietaria pollen allergy.

Changes in the Ovalbumin Proteolysis Profile by High Pressure and Its Effect on IgG and IgE Binding

Egg proteins are responsible for one of the most common forms of food allergy, especially in children, and one of the major allergens is ovalbumin (OVA). With the aim to examine the potential of high pressure to enhance the enzymatic hydrolysis of OVA and modify its immunoreactivity, the protein was proteolyzed with pepsin under high-pressure conditions (400 MPa). Characterization of the hydrolysates and peptide identification was performed by reversed-phase high-performance liquid chromatography-tandem mass spectrometry (RP-HPLC-MS/MS). The antigenicity (binding to IgG) and binding to IgE, using the sera of patients with specific IgE to OVA, were also assessed. The results showed that, upon treatment with pepsin at 400 MPa, all of the intact protein was removed in minutes, leading to the production of hydrolysates with lower antigenicity than those produced in hours at atmospheric pressure. However, the exposure of new target residues only partially facilitated the removal of allergenic epitopes, because the hydrolysates retained residual IgG- and IgE-binding properties as a result of the accumulation of large and hydrophobic peptides during the initial stages of hydrolysis. These peptides disappeared at later stages of proteolysis, although reactivity toward IgG and IgE was not completely abolished. Some fragments identified in the hydrolysates (such as Leu124-Phe134, Ile178-Ala187, Leu242-Leu252, Gly251-Ile259, Lys322-Gly343, Phe358-Phe366, and Phe378-Pro385) carried previously identified IgE-binding epitopes. Because some of the peptides found, such as Phe358-Phe366, probably contain only one binding site for IgE, the possibility to use high pressure to tailor hydrolysates that contain mostly peptides with only one IgE-binding site, which may help the immune system to tolerate egg proteins, is suggested.

Natural Rubber Latex Allergy in Pediatric Patients

During the last fifteen years better hygienic standards led to an increased consumption of natural rubber latex (NRL) gloves for the protection of medical staff. At the same time case reports about an IgE-mediated allergy to NRL sometimes causing life-threatening anaphylactic reactions came up. This allergy was different from the well-known type IV reactions caused by latex additives. Health care workers and patients with multiple surgery surgeries were identified as high risk groups. For unknown reasons patients with spina bifida (SB) showed the highest prevalence of NRL-specific IgE-antibodies. A pre-existing atopy increased the risk of latex sensitization. Allergic reactions were caused mainly by medical procedures, especially surgeries, if latex gloves and other latex containing devices were used. Meanwhile some allergenic proteins in NRL (named Hev b in accordance with the rubber tree Hevea brasiliensis) could be identified. Patients in different risk groups showed distinct prevalences of sensitization to these allergens. The way of the allergen uptake (aerogen or by direct mucosal contact during surgeries) played an important role in the sensitization to different allergens. Most of the latex allergens like Hev b 1, Hev b 3, Hev b 6.02 have been totally sequenced. Since the sequence of all registrated allergens (Hev b 1 - Hev b 13) is known, it was possible to localize in Hev b 1, Hev b 5 and Hev b 6.01 several IgE binding sites as well as T cell epitopes. Cross-reacting antibodies between NRL and numerous fruit were described and for some proteins structural homologies were well characterized. For the in vitro diagnosis of NRL allergy serologic tests with improved extracts and recombinant allergens (for instance ImmunoCAPTM system) are available. NRL protein extracts for skin prick tests were difficult to standardize. The use of natural extracts in combination with recombinant latex allergens could be one possible future perspective for skin testing. The problem of NRL allergy is still not resolved but significant progress has been made in its prevention. In high risk patients like persons with spina bifida a primary prophylaxis was performed with success, but also secondary or tertiary prophylaxis allows safe operations without symptoms of NRL allergy.

Cell-bound IgE and increased expression of Faɛ-receptors on dendritic cells in cutaneous infiltrates of mycosis fungoides

Skin biopsies of 31 non-atopic patients, 20 with mycosis fungoides, six with psoriasis and five with contact dermatitis, and of five non-atopic healthy controls were compared for the presence of cell-bound IgE and vacant IgE binding sites. IgE+ cells were demonstrated in the cutaneous infiltrate of nine (45%) patients with mycosis fungoides, two (33%) with psoriasis and one (20%) with contact dermatitis. Following pre-incubation of skin sections with IgE myeloma protein to saturate vacant IgE-binding sites, 14 out of 16 patients (88%) with stage I mycosis fungoides, five (83%) patients with psoriasis and one (20%) with contact dermatitis showed an increase in the number of IgE+ cells. While cell-bound IgE was positively related to serum IgE levels the expression of IgE-binding sites was not. All IgE+ cells were HLA-DR+ dendritic cells identified as either macrophages (CD68+, CD14+) or Langerhans cells (CD1+). Skin biopsies of non-atopic healthy controls or clinically uninvolved skin in mycosis fungoides had neither any IgE+ cells nor any vacant binding sites. Inhibition studies with IgG1, IgG4 and IgE myeloma proteins as well as with several enzymatic fragments of IgE demonstrated that IgE interacted with Fc epsilon-receptors through isotype-specific structures on the Fc epsilon-fragment. Four anti-CD23 monoclonal antibodies, however, were unable to stain vacant Fc epsilon-receptors nor could they block IgE-binding. We hypothesize that locally-secreted lymphokines, like IL-4 or interferon-gamma, induce Fc epsilon-receptors on dendritic cells in the cutaneous infiltrate and that these receptors become occupied in parallel with elevated serum IgE levels.

New Strategies for Allergen Immunotherapy

Specific allergen immunotherapy, consisting in the administration of increasing amounts of offending allergens into sensitive patients was first used nearly one hundred years ago and remains in use worldwide for treatment of allergic rhinitis and asthma. It has been recognised as the only effective treatment for type I allergic diseases when the appropriate quantities of allergens are used. The immunological mechanisms by which specific immunotherapy is effective include the modulation of T cells and the response of B-cells and is accompanied by significant decreases of specific IgE and increases in allergen specific IgG antibodies, mainly IgG4. While specific allergen injection immunotherapy is highly effective and the most common way of administration other routes such as oral or intranasal ways have been considered as and alternative to subcutaneous injections. During the last century, allergenic vaccines have been prepared using individual allergens adsorbed to different adjuvant substances. These vaccines have demonstrated efficacy and good results in different clinical trials. However, many novel approaches to allergen immunotherapy have been developed in the last years in order to increase the safety and efficacy of allergenic vaccines. In that way, different and modern vaccines have been prepared including more purified products such as depigmented allergen extracts; allergoids, consisting on big molecules of thousands of kDa, which contain all the individual allergens and show a significant decrease in severe adverse reactions; peptides or small aminoacid sequences; recombinant allergens; hypoallergenic vaccines where the IgE binding sites have been modified; or allergen-CpG fusion molecules. New presentations are under study and new treatments will be developed in the near future with the objective that the prevention of allergic disease may become a reality. The review article also discuss recent patent related to the field.