IgG anti-IgE from atopic dermatitis induces mediator release from basophils and mast cells

Mechanism underlying polyvalent IgG-induced regulatory T cell activation and its clinical application: Anti-idiotypic regulatory T cell theory for immune tolerance

The regulatory T (Treg) cells constitute a functionally defined subpopulation of T cells that modulate the immune system and maintain immune tolerance through suppression of the development of autoimmune responses to self-antigens and allergic reactions to external antigens. Reduction in the number or function of Treg cells has been suggested as a key immune abnormality underlying the development of autoimmune and allergic diseases. In vitro studies have demonstrated that purified polyvalent immunoglobulin G (IgG) from multiple healthy blood donors can exert immunomodulatory effects on Treg cells. Incubation of polyvalent human IgG with purified CD4+CD25high T cells increased the intracellular expression of interleukin (IL)-10. Intravenous administration of polyvalent human IgG induced significant expansions of CD4+ Foxp3+ Treg cells and clinical improvements in patients with autoimmune diseases. In human clinical trials, intramuscular administration of autologous total IgG significantly increased the percentage of IL-10-producing CD4+ Treg cells in the peripheral blood of healthy subjects and provided significant clinical improvements in patients with atopic dermatitis. These results suggest a clinical usefulness of polyvalent IgG-induced activation of Treg cells in human subjects. This review proposes a new hypothesis for immune tolerance mechanism by integrating the pre-existing "idiotypic network theory" and "Treg cell theory" into an "anti-idiotypic Treg cell theory." Based on this hypothesis, an "active anti-idiotypic therapy" for allergic and autoimmune diseases using autologous polyvalent IgG (as immunizing antigens) is suggested as follows: (1) Intramuscular or subcutaneous administration of autologous polyvalent IgG produces numerous immunogenic peptides derived from idiotypes of autologous IgG through processing of dendritic cells, and these peptides activate anti-idiotypic Treg cells in the same subject. (2) Activated anti-idiotypic Treg cells secrete IL-10 and suppress Th2 cell response to allergens and autoimmune T cell response to self-antigens. (3) These events can induce a long-term clinical improvements in patients with allergic and autoimmune diseases. Further studies are needed to evaluate the detailed molecular mechanism underlying polyvalent IgG-induced Treg cell activation and the clinical usefulness of this immunomodulatory therapy for autoimmune and allergic diseases.

Basophils from allergy to cancer

Human basophils, first identified over 140 years ago, account for just 0.5-1% of circulating leukocytes. While this scarcity long hampered basophil studies, innovations during the past 30 years, beginning with their isolation and more recently in the development of mouse models, have markedly advanced our understanding of these cells. Although dissimilarities between human and mouse basophils persist, the overall findings highlight the growing importance of these cells in health and disease. Indeed, studies continue to support basophils as key participants in IgE-mediated reactions, where they infiltrate inflammatory lesions, release pro-inflammatory mediators (histamine, leukotriene C₄: LTC₄) and regulatory cytokines (IL-4, IL-13) central to the pathogenesis of allergic diseases. Studies now report basophils infiltrating various human cancers where they play diverse roles, either promoting or hampering tumorigenesis. Likewise, this activity bears remarkable similarity to the mounting evidence that basophils facilitate wound healing. In fact, both activities appear linked to the capacity of basophils to secrete IL-4/IL-13, with these cytokines polarizing macrophages toward the M2 phenotype. Basophils also secrete several angiogenic factors (vascular endothelial growth factor: VEGF-A, amphiregulin) consistent with these activities. In this review, we feature these newfound properties with the goal of unraveling the increasing importance of basophils in these diverse pathobiological processes.

Autoantibodies to IgE can induce the release of proinflammatory and vasoactive mediators from human cardiac mast cells

Mast cells are multifunctional immune cells with complex roles in tissue homeostasis and disease. Cardiac mast cells (HCMCs) are strategically located within the human myocardium, in atherosclerotic plaques, in proximity to nerves, and in the aortic valve. HCMCs express the high-affinity receptor (FcεRI) for IgE and can be activated by anti-IgE and anti-FcεRI. Autoantibodies to IgE and/or FcεRI have been found in the serum of patients with a variety of immune disorders. We have compared the effects of different preparations of IgG anti-IgE obtained from patients with atopic dermatitis (AD) with rabbit IgG anti-IgE on the release of preformed (histamine and tryptase) and lipid mediators [prostaglandin D₂ (PGD₂) and cysteinyl leukotriene C₄ (LTC₄)] from HCMCs. Functional human IgG anti-IgE from one out of six AD donors and rabbit IgG anti-IgE induced the release of preformed (histamine, tryptase) and de novo synthesized mediators (PGD₂ and LTC₄) from HCMCs. Human IgG anti-IgE was more potent than rabbit IgG anti-IgE in inducing proinflammatory mediators from HCMCs. Human monoclonal IgE was a competitive antagonist of both human and rabbit IgG anti-IgE. Although functional anti-IgE autoantibodies rarely occur in patients with AD, when present, they can powerfully activate the release of proinflammatory and vasoactive mediators from HCMCs.

IgG Autoantibodies Against IgE from Atopic Dermatitis Can Induce the Release of Cytokines and Proinflammatory Mediators from Basophils and Mast Cells

IgE-mediated release of proinflammatory mediators and cytokines from basophils and mast cells is a central event in allergic disorders. Several groups of investigators have demonstrated the presence of autoantibodies against IgE and/or FcεRI in patients with chronic spontaneous urticaria. By contrast, the prevalence and functional activity of anti-IgE autoantibodies in atopic dermatitis (AD) are largely unknown. We evaluated the ability of IgG anti-IgE from patients with AD to induce the in vitro IgE-dependent activation of human basophils and skin and lung mast cells. Different preparations of IgG anti-IgE purified from patients with AD and rabbit IgG anti-IgE were compared for their triggering effects on the in vitro release of histamine and type 2 cytokines (IL-4, IL-13) from basophils and of histamine and lipid mediators (prostaglandin D₂ and cysteinyl leukotriene C₄) from human skin and lung mast cells. One preparation of human IgG anti-IgE out of six patients with AD induced histamine release from basophils, skin and lung mast cells. This preparation of human IgG anti-IgE induced the secretion of cytokines and eicosanoids from basophils and mast cells, respectively. Human monoclonal IgE was a competitive antagonist of both human and rabbit IgG anti-IgE. Human anti-IgE was more potent than rabbit anti-IgE for IL-4 and IL-13 production by basophils and histamine, prostaglandin D₂ and leukotriene C₄ release from mast cells. Functional anti-IgE autoantibodies rarely occur in patients with AD. When present, they induce the release of proinflammatory mediators and cytokines from basophils and mast cells, thereby possibly contributing to sustained IgE-dependent inflammation in at least a subset of patients with this disorder.

Clinical and Translational Significance of Basophils in Patients with Cancer

Despite comprising a very small proportion of circulating blood leukocytes, basophils are potent immune effector cells. The high-affinity receptor for IgE (FcɛRI) is expressed on the basophil cell surface and powerful inflammatory mediators such as histamine, granzyme B, and cytokines are stored in dense cytoplasmic granules, ready to be secreted in response to a range of immune stimuli. Basophils play key roles in eliciting potent effector functions in allergic diseases and type 1 hypersensitivity. Beyond allergies, basophils can be recruited to tissues in chronic and autoimmune inflammation, and in response to parasitic, bacterial, and viral infections. While their activation states and functions can be influenced by Th2-biased inflammatory signals, which are also known features of several tumor types, basophils have received little attention in cancer. Here, we discuss the presence and functional significance of basophils in the circulation of cancer patients and in the tumor microenvironment (TME). Interrogating publicly available datasets, we conduct gene expression analyses to explore basophil signatures and associations with clinical outcomes in several cancers. Furthermore, we assess how basophils can be harnessed to predict hypersensitivity to cancer treatments and to monitor the desensitization of patients to oncology drugs, using assays such as the basophil activation test (BAT).

IL-33 and Superantigenic Activation of Human Lung Mast Cells Induce the Release of Angiogenic and Lymphangiogenic Factors

Human lung mast cells (HLMCs) express the high-affinity receptor FcεRI for IgE and are strategically located in different compartments of human lung, where they play a role in several inflammatory disorders and cancer. Immunoglobulin superantigens (e.g., protein A of Staphylococcus aureus and protein L of Peptostreptococcus magnus) bind to the variable regions of either the heavy (V_H3) or light chain (κ) of IgE. IL-33 is a cytokine expressed by epithelial cells that exerts pleiotropic functions in the lung. The present study investigated whether immunoglobulin superantigens protein A and protein L and IL-33 caused the release of inflammatory (histamine), angiogenic (VEGF-A) and lymphangiogenic (VEGF-C) factors from HLMCs. The results show that protein A and protein L induced the rapid (30 min) release of preformed histamine from HLMCs. By contrast, IL-33 did not induce the release of histamine from lung mast cells. Prolonged incubation (12 h) of HLMCs with superantigens and IL-33 induced the release of VEGF-A and VEGF-C. Preincubation with IL-33 potentiated the superantigenic release of histamine, angiogenic and lymphangiogenic factors from HLMCs. Our results suggest that IL-33 might enhance the inflammatory, angiogenic and lymphangiogenic activities of lung mast cells in pulmonary disorders.

Is There a Role for Basophils in Cancer?

Basophils were identified in human peripheral blood by Paul Ehrlich over 140 years ago. Human basophils represent <1% of peripheral blood leukocytes. During the last decades, basophils have been described also in mice, guinea pigs, rabbits, and monkeys. There are many similarities, but also several immunological differences between human and mouse basophils. There are currently several strains of mice with profound constitutive or inducible basophil deficiency useful to prove that these cells have specific roles in vivo. However, none of these mice are solely and completely devoid of all basophils. Therefore, the relevance of these findings to humans remains to be established. It has been known for some time that basophils have the propensity to migrate into the site of inflammation. Recent observations indicate that tissue resident basophils contribute to lung development and locally promote M2 polarization of macrophages. Moreover, there is increasing evidence that lung-resident basophils exhibit a specific phenotype, different from circulating basophils. Activated human and mouse basophils synthesize restricted and distinct profiles of cytokines. Human basophils produce several canonical (e.g., VEGFs, angiopoietin 1) and non-canonical (i.e., cysteinyl leukotriene C₄) angiogenic factors. Activated human and mouse basophils release extracellular DNA traps that may have multiple effects in cancer. Hyperresponsiveness of basophils has been demonstrated in patients with JAK2^V617F-positive polycythemia vera. Basophils are present in the immune landscape of human lung adenocarcinoma and pancreatic cancer and can promote inflammation-driven skin tumor growth. The few studies conducted thus far using different models of basophil-deficient mice have provided informative results on the roles of these cells in tumorigenesis. Much more remains to be discovered before we unravel the hitherto mysterious roles of basophils in human and experimental cancers.

HIV gp120 Induces the Release of Proinflammatory, Angiogenic, and Lymphangiogenic Factors from Human Lung Mast Cells

Human lung mast cells (HLMCs) express the high-affinity receptor FcεRI for IgE and are involved in chronic pulmonary diseases occurring at high frequency among HIV-infected individuals. Immunoglobulin superantigens bind to the variable regions of either the heavy or light chain of immunoglobulins (Igs). Glycoprotein 120 (gp120) of HIV-1 is a typical immunoglobulin superantigen interacting with the heavy chain, variable 3 (V_H3) region of human Igs. The present study investigated whether immunoglobulin superantigen gp120 caused the release of different classes of proinflammatory and immunoregulatory mediators from HLMCs. The results show that gp120 from different clades induced the rapid (30 min) release of preformed mediators (histamine and tryptase) from HLMCs. gp120 also caused the de novo synthesis of cysteinyl leukotriene C₄ (LTC₄) and prostaglandin D₂ (PGD₂) from HLMCs. Incubation (6 h) of HLMC with gp120 induced the release of angiogenic (VEGF-A) and lymphangiogenic (VEGF-C) factors from HLMCs. The activating property of gp120 was mediated through the interaction with IgE V_H3⁺ bound to FcεRI. Our data indicate that HIV gp120 is a viral superantigen, which induces the release of different proinflammatory, angiogenic, and lymphangiogenic factors from HLMCs. These observations could contribute to understanding, at least in part, the pathophysiology of chronic pulmonary diseases in HIV-infected individuals.

Superantigenic Activation of Human Cardiac Mast Cells

B cell superantigens, also called immunoglobulin superantigens, bind to the variable regions of either the heavy or light chain of immunoglobulins mirroring the lymphocyte-activating properties of classical T cell superantigens. Protein A of Staphylococcus aureus, protein L of Peptostreptococcus magnus, and gp120 of HIV are typical immunoglobulin superantigens. Mast cells are immune cells expressing the high-affinity receptor for IgE (FcεRI) and are strategically located in the human heart, where they play a role in several cardiometabolic diseases. Here, we investigated whether immunoglobulin superantigens induced the activation of human heart mast cells (HHMCs). Protein A induced the de novo synthesis of cysteinyl leukotriene C₄ (LTC₄) from HHMCs through the interaction with IgE V_H3⁺ bound to FcεRI. Protein L stimulated the production of prostaglandin D₂ (PGD₂) from HHMCs through the interaction with κ light chains of IgE. HIV glycoprotein gp120 induced the release of preformed (histamine) and de novo synthesized mediators, such as cysteinyl leukotriene C₄ (LTC₄), angiogenic (VEGF-A), and lymphangiogenic (VEGF-C) factors by interacting with the V_H3 region of IgE. Collectively, our data indicate that bacterial and viral immunoglobulin superantigens can interact with different regions of IgE bound to FcεRI to induce the release of proinflammatory, angiogenic, and lymphangiogenic factors from human cardiac mast cells.

Omalizumab in chronic spontaneous urticaria: steroid sparing effect

Omalizumab has been recognized to be effective in the treatment of chronic spontaneous urticaria (CSU). The Italian Medicines Agency authorizes two omalizumab courses, only for patients with CSU unresponsive to antihistamines, and this schedule may limit omalizumab use. Unfortunately, in the majority of CSU, the schedule is unsatisfactory because symptoms usually recur shortly after discontinuation of treatment. A case of a patient needing more than two treatment courses with omalizumab is reported, in order to discuss the rationale for its long-term use. Patient had needed systemic steroids almost continuously for 4 years. Two severe glucocorticoid-associated adverse events (GAEs) occurred during long-term treatment. Omalizumab 300 mg monthly was started with immediate disappearance of the urticarial lesions. Beneficial effects waned shortly after discontinuation of treatment, and further steroid use was needed. A second omalizumab course showed the same clinical pattern, with prompt response and recurrence of symptoms after suspension. Therefore, we decided to repeat the 6 months omalizumab treatment as soon as symptoms recurred, to avoid further emergency steroid treatments and GAEs. This experience suggests that long-term use of omalizumab could be useful. Evidences show that omalizumab is effective and safe for re-treatment and long-term use of responding patients after recurrence.

Scar management in burn injuries using drug delivery and molecular signaling: Current treatments and future directions

In recent decades, there have been tremendous improvements in burn care that have allowed patients to survive severe burn injuries that were once fatal. However, a major limitation of burn care currently is the development of hypertrophic scars in approximately 70% of patients. This significantly decreases the quality of life for patients due to the physical and psychosocial symptoms associated with scarring. Current approaches to manage scarring include surgical techniques and non-surgical methods such as laser therapy, steroid injections, and compression therapy. These treatments are limited in their effectiveness and regularly fail to manage symptoms. As a result, the development of novel treatments that aim to improve outcomes and quality of life is imperative. Drug delivery that targets the molecular cascades of wound healing to attenuate or prevent hypertrophic scarring is a promising approach that has therapeutic potential. In this review, we discuss current treatments for scar management after burn injury, and how drug delivery targeting molecular signaling can lead to new therapeutic strategies.

Treatment of chronic spontaneous urticaria: Immunomodulatory approaches

This paper summarizes and reviews the mechanisms of action and data concerning efficacy of recommended treatments as well as other treatments that have been tested, independently of the outcomes, in the management of chronic spontaneous urticaria. Due to the central role of mast cells, basophils and histamine in the pathophysiology of this disease, H₁-antihistamines remain the first-line treatment. However, current knowledge about this complex disease, also recognizes an important role for T lymphocytes, B lymphocytes, and autoantibodies. Implications of these others mediators thus provide further targets for treatment. Indeed, agents previously used to treat other autoimmune and inflammatory diseases, have demonstrated efficacy in chronic spontaneous urticaria and are therefore potential therapeutic alternatives for antihistamine unresponsive patients.

Angiogenesis and lymphangiogenesis in inflammatory skin disorders

Angiogenesis, the growth of new blood vessels from pre-existing vessels, occurs physiologically in wound healing, during inflammatory diseases, and in tumor growth. Lymphangiogenesis can be activated in inflammation and tumor metastasis. The family of vascular endothelial growth factors (VEGFs) and angiopoietins are essential for angiogenesis and lymphangiogenesis. The angiogenic process is tightly regulated by VEGFs, angiopoietins, and endogenous inhibitors. VEGFs and angiopoietins exert their effects by activating specific receptors present on blood and lymphatic endothelial cells. There is now compelling evidence that cells of innate and adaptive immunity (macrophages, mast cells, neutrophils, eosinophils, lymphocytes) are a major source of angiogenic and lymphangiogenic factors. Chronic inflammatory skin diseases such as psoriasis and atopic dermatitis are characterized by altered angiogenesis, lymphangiogenesis, or both. Also such acute inflammatory skin disorders as urticaria, ultraviolet B-induced damage, and angioedema are associated with changes in angiogenic factors. In systemic sclerosis there is a switch from proangiogenic to antiangiogenic factors that play a role in the defective vascular process of this disorder. As yet, there are no clinical trials showing that canonical VEGF/VEGF receptor-targeted strategies can modulate inflammatory skin diseases. Novel strategies targeting other angiogenic/lymphangiogenic pathways should also be investigated.

Human heart as a shock organ in anaphylaxis

Anaphylaxis is a potentially fatal, immediate hypersensitivity reaction. Mast cells and basophils, by elaborating vasoactive mediators and cytokines, are the main primary effector cells of anaphylaxis. Mast cells have been identified in human heart between myocardial fibers, perivascularly, in the adventitia, and in the arterial intima. Mast cells isolated from human heart tissue (HHMC) of patients undergoing cardiac transplantation express high affinity immunglobulin E (IgE) receptors (FcεRI), C3a, C5a, and kit receptors (KIT). Anti-IgE, anti-FcεRI, and immunoglobulin superallergens induce in vitro secretion of preformed mediators (histamine, tryptase, chymase, and renin) and the de novo synthesis of cysteinyl leukotriene C4 (LTC4) and prostaglandin D2 (PGD2) from HHMC. Complement is activated and anaphylatoxin forms during anaphylaxis. C5a and C3a cause the in vitro release of histamine and tryptase from HHMC. Therapeutic (general anesthetics, protamine, etc.) and diagnostic agents (radio contrast media, etc.), which can cause anaphylactoid reactions, activate HHMC in vitro. Low concentrations of histamine and cysteinyl leukotrienes given to subjects undergoing diagnostic catheterisation caused significant systemic and coronary hemodynamic effects. These data indicate that human heart mast cells and their mediators play a role in severe anaphylactic reactions.

Histamine enhances keratinocyte-mediated resolution of inflammation by promoting wound healing and response to infection

BACKGROUND

The role of the epidermis in the immune response is well known. While multiple cytokines are implicated in keratinocyte-mediated infection clearance and wound healing, little is known about the involvement of keratinocytes in promoting resolution of inflammation.

AIM

To assess effects of histamine stimulation on keratinocyte function.

METHODS

We performed a combined microarray/Gene Ontology analysis of histamine-stimulated keratinocytes. Functional changes were tested by apoptosis assessment and scratch assays. Histamine receptor involvement was also assessed by blocking wound closure with specific antagonists.

RESULTS

Histamine treatment had extensive effects on keratinocytes, including effects on proinflammatory responses and cellular functions promoting wound healing. At the functional level, there was reduced apoptosis and enhancement of wound healing in vitro. At the receptor level, we identified involvement of all keratinocyte-expressed histamine receptors (HRHs), with HRH1 blockage resulting in the most prominent effect.

CONCLUSIONS

Histamine activates wound healing and infection clearance-related functions of keratinocytes. While enhancement of histamine-mediated wound healing is mediated predominantly via the HRH1 receptor, other keratinocyte-expressed receptors are also involved. These effects could promote resolution of skin inflammation caused by infection or superficial injury.

Pathogenesis of chronic urticaria

Chronic urticaria is defined as the presence of urticaria (hives) for at least 6 weeks with the assumption that it occurs daily or close to it. If we eliminate physical urticarias and urticarial vasculitis from consideration, the remainder can be divided into autoimmune chronic urticaria (45%) and idiopathic chronic urticaria (55%). The autoimmune subgroup is associated with the IgG anti-IgE receptor alpha subunit in 35-40% of patients and IgG anti-IgE in an additional 5-10%. These autoantibodies have been shown to activate blood basophils and cutaneous mast cells in vitro with augmentation of basophil activation by complement and release of C5a, in particular. Binding methods (immunoblot and ELISA) yield positives in many autoimmune diseases as well as occasional normal subjects or patients with other forms of urticaria but most such sera are non-functional. Activation of basophils or mast cells causing histamine release is quite specific for chronic urticaria and defines the autoimmune subgroup. Although pathogenicity is not formally proven, the antibodies cause wealing upon intradermal injection, and removal of the autoantibody leads to remission. A cellular infiltrate is seen to be characterized by mast cell degranulation and infiltration of CD4+ T lymphocytes, monocytes, neutrophils, eosinophils, and basophils. The intensity of the infiltrate and clinical severity of the disease (including accompanying angio-oedema) is more severe in the autoimmune subpopulation. This latter group also has a higher evidence of human leucocyte antigen DR alleles associated with autoimmunity and a 25% incidence of antithyroid antibodies with diagnosed hypothyroidism in some. Hypo-responsiveness of patients' basophils to anti-IgE and hyperresponsiveness to serum defines another subpopulation (at least 50%) that overlaps the idiopathic and autoimmune subgroups. Hypo-responsiveness to anti-IgE has been shown to be associated with elevated levels of cytoplasmic phosphatases that inhibit degranulation. Reversal of the abnormality is seen with disease remission. Further work will be needed to distinguish whether this is a cause or a consequence of persistent urticaria and to further assess the relationship (or lack thereof) of altered responsiveness (decreased or increased) with the presence or absence of activating autoantibodies.

Conventional and new approaches to hyposensitization

Hyposensitization in IgE-mediated allergic diseases has traditionally been induced by immunotherapy in which increasing amounts of allergens have been injected until a maximal tolerated dose has been achieved. Among the most obvious immunological effects of immunotherapy have been the production of allergen-specific IgG and some impairment in the synthesis of allergen-specific IgE. In addition to allergen-specific IgG (sometimes described as blocking antibodies) anti-idiotypic and anti-isotypic (IgG anti-IgE) have recently attracted attention as possibly being involved in hyposensitization. The effects of immunotherapy at the cellular level (either as T cell control of IgE synthesis or as modulation of mediator release by effector cells) also deserve further investigation.

Histamine-releasing factors, a heterogeneous group of different activities

Histamine-releasing factor or HRF is a collective term used for a heterogeneous group of factors with different modes of action. The current review is focussed on IgE-dependent HRF that require the presence of certain types of IgE (designated IgE+) to induce histamine release. IgE+ might be a structurally different IgE molecule, or, alternatively, autoreactive IgE. A subgroup of IgE-dependent HRF does not bind to IgE, such as cloned HRF p23. This factor turned out to be a basophil-priming cytokine. Alternatively IgE-dependent HRF might be an autoallergen. Several groups demonstrated IgE antibodies to human proteins. However, not all IgE autoallergen-containing extracts induce histamine release of appropriately sensitized basophils. In culture supernatants of human mononuclear cells an autoallergenic activity (Agmn) is found, but no binding to IgE+ was found yet. Agmn might be an autoallergen, since it is cross-reactive with a grass pollen allergen in the stripped basophil assay. IgE-dependent HRF and IgE+ may play a role in the late allergic reaction (LAR). However, IgE+ responsiveness to Agmn (IgEmn+) was not required for a bronchial LAR. IgEmn+ is associated with chronic allergic disease, since the prevalence of IgEmn+ is high in the serum of severe asthmatics and atopic dermatitis patients. Our hypothesis is that exogenous allergens induce IgE antibodies cross-reactive with an endogenous protein. During a LAR, these endogenous proteins are released and the subsequent IgE-mediated reaction prolongs and aggravates the allergic and/or asthmatic symptoms. In conclusion, HRF is a confusing term since it is used for different activities. It might be better to avoid this terminology on and just describe the activity of the factors. Autoallergenic activity is likely to explain most, if not all, IgE-dependent activity.

Molecular aspects of allergy

Atopic diseases such as asthma, rhinitis, eczema and food allergies have increased in most industrialised countries of the world during the last 20 years. The reasons for this increase are not known and different hypotheses have been assessed including increased exposure to sensitising allergens or decreased stimulation of the immune system during critical periods of development. In allergic diseases there is a polarisation of the Th2 response and an increase in the production of type 2 cytokines which are involved in the production of immunoglobulin E and the development of mast cells, basophils and eosinophils leading to inflammation and disease. The effector phase of atopy is initiated by interaction with Fc epsilon RI expressed on effector cells such as mast cells and basophils but also found on an ever increasing list of cells. Binding of a polyvalent allergen to the variable part of IgE leads to a cross-link of the receptor that triggers the cell to release histamine and pharmacological mediators of the symptomatic allergic response. Cross-linking of Fc epsilon RI by autoantibodies against the alpha-chain of the Fc epsilon RI, causing subsequent histamine release is thought to be involved in the pathogenesis of other diseases such as chronic idiopathic urticaria (CIU). To date, most therapeutic strategies are aimed at inhibiting and controlling components of the inflammatory response. Recently, new treatment strategies have emerged that focus on the development of preventive and even curative treatments. The most promising therapeutic approaches are aimed at inhibiting the IgE-Fc epsilon RI interaction with the use of non-anaphylactogenic anti-IgE or anti-Fc epsilon RIalpha autoantibodies. Clinical trials in humans using an humanised anti-IgE antibody showed that this antibody was well tolerated and reduced both symptoms and use of medication in asthma and allergic rhinitis. Thus interruption of the atopic cascade at the level of the IgE-Fc epsilon RI interaction with the use of non-anaphylactogenic antibodies is effective and represents an attractive therapy for the treatment of atopic disease.

Studies on the association between immunoglobulin E autoreactivity and immunoglobulin E-dependent histamine-releasing factors

It has been reported that serum immunoglobulin E (IgE) from certain atopic patients can sensitize basophils to release histamine in response to IgE-dependent histamine-releasing factors (HRFs). It has also been shown that patients suffering from severe forms of atopy may contain IgE autoantibodies. It was investigated whether HRF-responsive sera contained IgE autoantibodies and if there was an association between IgE autoreactivity and IgE-dependent responsiveness to HRF. The presence of HRF-responsive IgE (IgE+) in serum of patients with respiratory atopy was determined by stimulating stripped human basophils sensitized by serum with peripheral blood mononuclear cell (PBMC)-derived HRF, and measuring the release of histamine. In parallel, these sera were screened for the presence of IgE autoantibodies to nitrocellulose-blotted human cellular extracts. The capacity of IgE autoantigen-containing preparations to induce histamine release was tested in the stripped basophil assay. Eleven out of 52 sera contained IgE autoantibodies to blotted cellular extracts of human PBMCs or of the human epithelial cell line A431. No significant association was found between IgE autoreactivity and IgE-dependent responsiveness to HRF: 7/26 IgE+ sera contained IgE to human cellular extracts, and 4/26 of the sera without IgE+ did also. IgE autoantigen-containing extracts did not induce histamine release of appropriately sensitized basophils. By size-exclusion chromatography it was shown that a 32 000 MW autoantigen eluted in the >55 000 MW fraction, which indicates that this protein forms polymers or complexes with other macromolecules. This might explain the discrepancy between binding and histamine-releasing activity. A 20 000 MW IgE-defined autoantigen cross-reacted with a shrimp allergen. Our results indicate that IgE-reactivity to immunoblotted human protein and IgE-dependent HRF activity are distinct entities that may co-occur in atopic patients.

Autoantibodies in atopic dermatitis

Recent progress in the autoimmune aspects of atopic dermatitis has clarified that patients with atopic dermatitis develop IgE-class autoantibodies mainly against intracellular proteins. The cloning of cDNAs encoding autoallergens with human expression cDNA libraries and serum IgE from atopic dermatitis patients has unraveled the molecular characteristics of IgE-binding autoantigens. Some patients with atopic dermatitis also have IgG-class autoantibodies, especially anti-nuclear antibodies. One of the nuclear autoantigens was identified as DFS70/transcription coactivator p75. In addition, p80-coilin in nuclear coiled bodies is also targetted. Several lines of evidence suggest that a subset of atopic dermatitis may be associated with an autoimmune response.

The immunoglobulin superantigen-binding site of HIV-1 gp120 activates human basophils

OBJECTIVE

To investigate the mechanism whereby HIV-1 envelope glycoprotein gp120 from four different isolates obtained in three different countries induces proinflammatory mediator release from normal human basophils.

METHODS

Histamine, cysteinyl leukotriene C4 (LTC4) and interleukin 4 (IL-4) release into the supernatant was measured in gp120-stimulated peripheral blood basophils from HIV-1 and HIV-2 negative subjects.

RESULTS

The HIV glycoprotein was a potent stimulus for release of these mediators in basophils purified from donors negative for HIV-1 and HIV-2. There was also a correlation (r = 0.58; P < 0.01) between the maximum IL-4 release from basophils induced by gp120 and by anti-IgE. Basophils from which IgE had been dissociated by brief exposure to lactic acid no longer released histamine in response to gp120 and anti-IgE. Anti-IgE specifically desensitized basophils to a subsequent challenge with anti-IgE and gp120. Human monoclonal IgM carrying the VH3 domain, but not that carrying the VH6 domain, inhibited gp120-induced secretion of histamine from basophils in a concentration-dependent manner. Synthetic peptides identical to regions distant from the N- and C-termini of gp120MN inhibited its activating capacity.

CONCLUSIONS

gp120 acts as a viral superantigen interacting with the VH3 domain of IgE to induce the release of preformed and de novo synthesized mediators from human cells carrying the Fc fragment Fc epsilonRI receptor.

Immunological modulation of human cardiac mast cells

Human mast cells, by elaborating various cytokines, chemokines and proinflammatory mediators play a complex role in several allergic and inflammatory disorders. Mast cells have been identified in human heart tissue in close proximity to the sarcolemma, in perivascular and adventitial locations and in the shoulder region of coronary atheroma. Human heart mast cells (HHMC) can be isolated from patients undergoing heart transplantation and can be immunologically activated in vitro to induce the release of tryptase, chymase, cysteinyl leukotriene C4 and prostaglandin D2. Several cytokines (e.g., stem cell factor and TNF-alpha) reside in secretory granules of HHMC. Mast cell density is increased in the hearts of patients with ischemic and idiopathic dilated cardiomyopathy. Cardiac mast cells might contribute to the evolution of atherosclerosis, dilated cardiomyopathy, cardiac and systemic anaphylaxis through the release of cytokines and vasoactive and proinflammatory mediators.

The high-affinity IgE receptor (Fc epsilon RI): from physiology to pathology

The high affinity receptor for immunoglobulin E (designated Fc epsilon RI) is the member of the antigen (Ag) receptor superfamily responsible for linking pathogen-or allergen-specific IgEs with cellular immunologic effector functions. This review provides background information on Fc epsilon RI function combined with more detailed summaries of recent progress in understanding specific aspects of Fc epsilon RI biology and biochemistry. Topics covered include the coordination and function of the large multiprotein signaling complexes that are assembled when Fc epsilon RI and other Ag receptors are engaged, new information on human receptor structures and tissue distribution, and the role of the FcR beta chain in signaling and its potential contribution to atopic phenotypes.

The anti-IgE/anti-FcepsilonRIalpha autoantibody network in allergic and autoimmune diseases

Basophil granulocytes and tissue mast cells and their mediators play a role in the pathogenesis of several immune and inflammatory disorders. Human basophils and mast cells (FcepsilonRI+ cells) can be activated through immunological interaction with the IgE-FcepsilonRI network. FcepsilonRI+ cells can be triggered by cross-linking between the Fab portions of IgE and multivalent antigens (direct anaphylaxis). 'Reverse type' anaphylaxis can occur through three distinct mechanisms: antibodies against the Fcepsilon portion of IgE (anti-IgE), antibodies against epitopes of the alpha chain of FcepsilonRI (anti-FcepsilonRIalpha) and anti-IgG acting on IgG-IgE complexes bound to FcepsilonRI. Anti-IgE autoantibodies are occasionally present even in normal donors and more frequently in a variety of allergic (chronic urticaria, atopic dermatitis and bronchial asthma) and autoimmune disorders (rheumatoid arthritis, lupus erythematosus and systemic sclerosis). IgG anti-IgE from a small percentage of patients induces the release of mediators from human FcepsilonRI+ cells. Some of the anti-IgE autoantibodies present in allergic patients are non-anaphylactogenic, thus representing a possible protective mechanism preventing the association of IgE with FcepsilonRI. Anti-FcepsilonRIalpha autoantibodies also occur in a significant percentage of patients of chronic urticaria and probably non-allergic asthma and some autoimmune diseases. Although anti-IgE and anti-FcepsilonRIalpha autoantibodies, present in a percentage of patients with immune disorders, are relevant to the pathogenesis of these conditions, much remains to be learnt about their immunochemistry, their prevalence and precise role in various inflammatory diseases.

High IgE in rheumatoid arthritis (RA) patients is complexed with anti-IgE autoantibodies

This study presents data on more than 300 RA and allergic patients analysed for their serum levels of anti-immunoglobulin isotype autoantibodies and IgE. We observed high levels of IgE in sera of RA and allergic patients. Interestingly, we measured significantly higher specific IgE levels against Alternaria but not against nine other allergens in the RA compared with the allergic group. As expected, anti-IgG autoantibodies (rheumatoid factors (RF)) of different isotypes were detected in sera from RA patients only. However, we found increased titres of complexed anti-IgE autoantibodies in all RF+ groups and in the allergic group. These findings may explain why despite elevated IgE levels a decreased prevalence of allergic diseases in RA patients has been observed.

Endogenous Superallergen Protein Fv Induces IL-4 Secretion from Human FcεRI+ Cells Through Interaction with the VH3 Region of IgE

We investigated the mechanism whereby protein Fv (pFv), a human sialoprotein found in normal liver and largely released in the intestinal tract in patients with viral hepatitis, induces mediator release from basophils and mast cells and evaluated whether it also induces IL-4 synthesis and secretion in basophils. pFv is a potent stimulus for histamine and IL-4 release from purified basophils. Histamine and IL-4 secretion from basophils activated by pFv was significantly correlated (rs = 0.70; p &lt; 0.001). There was also a correlation (rs = 0.58; p &lt; 0.01) between the maximum pFv- and anti-IgE-induced IL-4 release from basophils. The average t1/2 for pFv-induced histamine release was lower (3.5 ± 1.5 min) than for IL-4 release (79.5 ± 8.5 min; p &lt; 0.01). IL-4 mRNA, constitutively present in basophils, was increased after stimulation by pFv and was inhibited by cyclosporin A and tacrolimus. Basophils from which IgE had been dissociated by brief exposure to lactic acid no longer released IL-4 in response to pFv and anti-IgE. The response to an mAb cross-linking the α-chain of FcεRI was unaffected by this treatment. Three human VH3+ monoclonal IgM concentration-dependently inhibited pFv-induced secretion of IL-4 and histamine from basophils and of histamine from human lung mast cells. In contrast, VH6+ monoclonal IgM did not inhibit the release of IL-4 and histamine induced by pFv. These results indicate that pFv, which acts as an endogenous superallergen, interacts with the VH3 domain of IgE to induce the synthesis and release of IL-4 from human FcεRI+ cells.

Toxocara infestations in humans: symptomatic course of toxocarosis correlates significantly with levels of IgE/anti-IgE immune complexes

Infestations of humans with the parasitic nematode T. canis are common in both developing and industrialized countries. Most infestations induce a clinically inapparent course of infection, however, severe clinical manifestations, i.e. visceral larva migrans (VLM) or ocular larva migrans (OLM) syndromes are observed. To find an explanation for the different courses of toxocarosis we examined several serological parameters: the expression of (i) specific IgE (Immunoblot, IB), (ii) specific IgG subclasses (IgG1-4, ELISA and the formation of (iii) IgE/anti-IgE immune complexes. Serum samples were obtained from persons with symptomatic (VLM, OLM) and asymptomatic course (AS) of the infestation. As antigen, T. canis excretory/secretory (TES) antigen from L3 larvae was used. Reactivity of IgE against SDS-PAGE separated TES antigens was marginally higher in toxocarosis patients (35%) than in asymptomatics (24%), but without statistical significance. TES-specific IgG (1-4), predominant subclass in all three groups was IgG1, followed by IgG2, IgG4 and IgG3. Subclass IgG1, 2, 4 showed significant differences between patients with VLM associated symptoms and asymptomatic persons (P < 0.001) but not between patients with OLM associated symptoms and asymptomatics. Significantly elevated levels of IgE/anti-IgE immune complexes were detected in sera of patients with symptomatic course of the disease, both VLM and OLM (P < 0.001). Whereas specific IgG may act via antibody dependent cell-mediated cytotoxicity mechanisms, IgE/anti-IgE immune complexes might possibly participate in VLM and OLM by inducing type III hypersensitivity.

Anti-IgE and anti-Fc epsilon RI autoantibodies in clinical allergy

Autoantibodies recognizing critical effector molecules of type I allergic reactions have been identified. Anti-IgE autoantibodies occur at high frequencies not only in atopic diseases but also in healthy individuals and, depending on their epitope specificities, may promote or prevent the elicitation of allergic symptoms. In contrast, anti-Fc epsilon RI autoantibodies with basophil/mast cell activating properties were selectively found in patients with chronic urticaria, a condition characterized by the continuous degranulation of mast cells. Thus, humoral anti-Fc epsilon RI autoreactivity defines a distinctive subset of chronic urticaria and may well be the causative and pathogenetic principle in this disease.

Human synovial mast cells. I. Ultrastructural in situ and in vitro immunologic characterization

OBJECTIVE

To examine the ultrastructure of human synovial mast cells in situ, to identify immunologic and nonimmunologic stimuli that activate these cells in vitro, and to quantify a number of preformed and de novo-synthesized mediators.

METHODS

We conducted an ultrastructural study of synovial mast cells in situ and performed immunoelectron microscopy localization of tryptase and chymase. Isolated synovial mast cells were analyzed biochemically, immunologically, and functionally in vitro and compared with cells from human lung, heart, and skin.

RESULTS

Ultrastructural study of synovial tissue revealed mast cells with homogeneously dense, scrolled, crystal, and mixed granules, and lipid bodies in the cytoplasm. A small percentage of mast cells showed evidence of degranulation. Immunoelectron microscopy demonstrated the subcellular localization of tryptase and chymase over granules of > 90% of the mast cells, which were of the MCTC subtype. Isolated synovial mast cells released histamine in response to immunologic (anti-IgE and anti-Fc epsilon receptor I [anti-Fc epsilon RI]) and nonimmunologic (substance P, recombinant human stem cell factor, and 48/80) stimuli, but did not respond to recombinant human C5a in vitro. Synovial mast cells differed from those isolated from other human tissues, in a variety of immunologic and biochemical features. There was a linear correlation between the percentage of histamine secretion and tryptase release (r = 0.79, P < 0.001) induced by cross-linking of Fc epsilon RI. Cross-linking of IgE with anti-IgE on synovial mast cells induced de novo synthesis of prostaglandin D2 (mean +/- SEM 87.5 +/- 4.9 ng/10(6) cells) and of leukotriene C4 (57.6 +/- 17.8 ng/10(6) cells).

CONCLUSION

Mast cells ultrastructurally characterized in situ in synovial tissue were seen to differ from mast cells previously isolated from other human tissues. This raises the possibility that the local microenviroment influences their phenotype. Isolation of mast cells from human synovia can be useful for studying their role and their mediators in patients with arthritis.

Characteristics of histamine-releasing activity in the sera of patients with chronic idiopathic urticaria

BACKGROUND

The serum histamine-releasing activity (HRA) found in a sizable percentage of patients with chronic idiopathic urticaria (CIU) has been partially characterized. However, the variable effect of individual HRA+ sera in basophils of different donors and the relationship of HRA to the clinical course require further investigation.

OBJECTIVE

The study was performed to characterize the HRA found in sera of some members of a sizable group of carefully evaluated patients with CIU.

METHODS

Sera of 70 patients with CIU, evaluated with a standard protocol, were screened for increased HRA. HRA+ sera were fractionated, heated, and tested on unaltered and altered basophils obtained from a panel of normal donors. HRA levels were compared with concomitant clinical manifestations.

RESULTS

HRA+ sera were found in 30% of our patients with CIU, HRA was predominantly in the IgG fraction, sensitive to 56 degrees C heating for 4 hours, and generally reacted more with IgE-stripped basophils. Considerable variation in the degree of response to HRA+ sera in the basophils of different normal subjects did not correlate with the degree of response of these cells to heterologous anti-IgE antiserum. Serum HRA levels were generally much lower when symptoms decreased in these patients with CIU.

CONCLUSION

Serum HRA from patients with CIU appears to bind most commonly to the IgE receptor and may be a marker of clinical disease activity. HRA appears in an IgG-containing fraction of the serum and may contain IgE in some cases.

Urticaria and angioedema: a clinical spectrum

OBJECTIVE

The objective of this review is to give the reader a global insight into the spectrum of urticaria, focusing on differential diagnosis and pathogenic mechanisms. This review will define the role of the mast cell, explore a possible autoimmune basis for urticaria, and examine the purported role of food allergy in chronic urticaria. Last, the work-up and treatment of urticaria will be discussed in the context of the histologic diagnosis.

STUDY SELECTION

The relevant past medical literature will be reviewed in the context of new and novel research into the mechanisms of chronic urticaria.

RESULTS

Urticaria can be classified histopathologically into the following three categories: (1) neutrophilic vasculitis, (2) polymorphous perivascular infiltrate, and (3) sparse perivascular lymphocytic infiltrate. Each of the above histologic patterns correlates with a distinct clinical entity and the work-up and treatment of urticaria will be related to each of the above histologic types.

CONCLUSIONS

Urticaria and angioedema are frustrating problems for both physicians and their patients; however, the problem can best be approached by considering urticaria as a symptom that may be part of a larger clinical spectrum. The physical examination and medical history remain the two most important pieces of information. The allergist frequently overlooks the value of a skin biopsy as an aid in sorting out the pathophysiology of urticaria and the biopsy results may help to classify urticaria into subgroups which respond differently to treatment.

Anti-IgE in allergic sensitization

Anti-IgE autoantibodies exist predominantly in the sera of patients with atopic disease. For some time such anti-IgE autoantibodies have been considered a phenomenon that may not be of clinical importance. The cloning of such anti-IgE autoantibodies has eliminated doubts of whether these antibodies exist, but it is still unclear whether such autoantibodies play a pathophysiological role. However, there are ongoing clinical trials that use humanized anti-IgE antibodies for passive immunization of atopic individuals. While this approach may not definitely clarify the role of anti-IgE autoantibodies, it will nevertheless clarify the role of IgE.

Serum IgG autoantibodies directed against the alpha chain of Fc epsilon RI: a selective marker and pathogenetic factor for a distinct subset of chronic urticaria patients?

While it is well established that acute allergic urticaria is caused by degranulation of skin mast cells occurring after allergen/IgE-dependent cross-linking of high affinity IgE receptors (FcepsilonRI), the pathophysiologic mechanisms operative in chronic urticaria (CU) are less well understood. Some evidence points to the existence of histamine-releasing activity in the serum of CU patients which possibly acts via triggering of FcepsilonRI. In this study, we aimed to better characterize this anti-FcepsilonRIalpha reactivity of CU patients using affinity-purified, IgE-depleted IgG fractions of such individuals (CU-IgG). Using immobilized, recombinant soluble FcepsilonRIalpha as a a reaction target for Western blot studies, we found that 12/32 (37%) CU-IgG serum samples exhibited IgG autoreactivity against FcepsilonRI- alpha. These findings were confirmed by experiments demonstrating that immunoblot-reactive, but not immunoblot-nonreactive, CU-IgG preparations precipitated the FcepsilonRIalpha from FcepsilonRI- alphagamma-transfected cells. No anti-FcepsilonRIalpha reactivity was observed in IgG fractions from atopic dermatitis (AD) patients (0/15) or healthy control individuals (CO:0/15). As opposed to the selective occurrence of IgG anti-Fc epsilon RI alpha autoantibodies in CU patients, IgG anti-IgE antibodies were detected in all groups investigated (CU: 69%; AD: 73%; CO: 26%). While both types of autoantibodies can exhibit histamine-releasing properties, not all of the autoantibodies proved to be functional in vitro. Our results indicate that the occurrence of IgG anti-FcepsilonRIalpha reactivity defines an autoimmune-mediated subentity of CU and provide a basis for the development of new diagnostic procedures and, perhaps, therapeutic strategies for this disease.

Immunological characterization and functional importance of human heart mast cells

Mast cells are present in normal and even more abundant in diseased human heart tissue and their localization is of particular relevance to their function. Within heart tissue mast cells lie between myocytes and in close contact with blood vessels. They are also found in the coronary adventitia and in the shoulder regions of a coronary atheroma. The density of cardiac mast cells is markedly higher in some patients with myocarditis and dilated cardiomyopathy than in accident victims without cardiovascular diseases. More importantly, in some of these conditions there is in situ evidence of mast cell activation. We have described an original technique to isolate and purify HHMC for in vitro study. This procedure gives viable cells and after stimulation with immunological or non-immunological stimuli they release performed (histamine and tryptase) and newly generated mediators (PGD2 and LTC4). We have demonstrated that HHMC differ from those in other anatomical districts in that they are activated by specific immunological and non-immunological stimuli, and in their relation to the arachidonic acid metabolism, suggesting that the local microenvironment can influence their phenotypic and biochemical characteristics. Our own and other findings suggest that HHMC have complex and significant roles in different pathophysiological conditions involving the cardiovascular system. Direct activation of HHMC by therapeutic and diagnostic substances injected intravenously explains some of the anaphylactoid reactions caused by these agents. HHMC possess Fc epsilon RI and IgE bound to the surface and C5a receptors, which could explain how cardiac mast cells are involved in systemic and cardiac anaphylaxis. Cardiac mast cells and those in human coronary arteries also play a role in the early and late stages of atherogenesis and during ischemic myocardial injury. In conclusion, although studies of HHMC are in their infancy, their in vitro isolation may be useful in identifying additional mediators synthesized and released, stimuli relevant to human pathophysiology, and pharmacological agents selectively modulating the activation of these cells and their mediators. Drugs specifically acting on HHMC or on their mediators may eventually be useful in treating different cardiovascular diseases.

Human auto-anti-idiotypic antibodies to mite-specific IgE can degranulate human basophils in vitro

BACKGROUND

Anti-idiotypic antibodies (anti-Ids) to specific IgE antibodies are formed spontaneously during an anti-allergen immune response and can be induced by immunotherapy. Although anti-Ids can down-regulate the production of IgE antibodies, at least in experimental models, their possible role in the modulation of target cell reactivity remains ill-defined.

OBJECTIVE

The capacity of human anti-Ids to modulate the release of histamine was examined in an in vitro system of human basophil degranulation. Anti-Ids were prepared from the serum of six Dermatophagoides pteronyssinus (Dp)-hypersensitive patients suffering from atopic dermatitis and who had never been desensitized. Basophils were obtained from the blood of atopic donors. The extent of histamine release was determined using a fluorometric assay.

RESULTS

We show that: anti-Ids trigger the release of histamine in an allergen-specific, dose- and IgE-dependent manner; the release is not due to the presence of allergen and/or anti-IgE antibodies; and that the degranulating activity can be removed by absorption with affinity-purified anti-Dp antibodies of the corresponding patient.

CONCLUSION

These results indicate that spontaneously produced human anti-Ids can modulate the reactivity of human basophils.

IgE autoantibodies in atopic dermatitis--occurrence of different antibodies against the CH3 and the CH4 epitopes of IgE

Levels of "free" anti-IgE autoantibodies and IgE/anti-IgE immune complexes were measured in the sera of patients with atopic dermatitis before and after treatment, psoriasis patients, and nonatopic controls. In this measurement, we used two monoclonal antibodies with distinct in vitro functions (LE 27, BSW 17), directed against the epsilon CH3 and CH4 domains of the IgE Fc-fragment, in a novel immunobinding assay. In patients with atopic dermatitis, elevated levels of "free" anti-IgE antibodies and IgE/anti-IgE immune complexes were detected in comparison to psoriasis patients and controls. In addition, there was a positive correlation between total IgE and the amount of IgE/anti-IgE complexes detected by LE 27 (r = 0.7; P < 0.001) or BSW 17 (r = 0.64; P < 0.001) in patients with atopic dermatitis. In contrast, an inverse correlation was observed between total IgE and "free" anti-IgE antibodies (r = -0.34; P < or = 0.05) in atopic dermatitis. However, serum levels of anti-IgE autoantibodies before and after therapy in patients with atopic dermatitis did not differ, and levels of anti-IgE antibodies did not correlate with clinical severity, as evaluated by an established clinical scoring system. Our data clearly indicate that significantly elevated amounts of anti-IgE antibodies could be observed in patients with atopic dermatitis, which are directed against different epitopes on the IgE molecule. It is tempting to speculate that these autoantibodies exert different effects of IgE-receptor-bearing effector cells and may play an important role in IgE regulation.

Anti-IgE autoantibodies and bee-sting allergy

Serum anti-IgE autoantibodies (aaIgE) were investigated by dot immunobinding assay in bee-allergic patients in comparison with nonallergic beekeepers, healthy blood donors, and atopic subjects. Elevated serum levels of aaIgE--either free or combined with IgE--were found in both bee-allergic patients and atopic subjects as compared with beekeepers and healthy donors. With regard to a possible significance of aaIgE for the protective mechanism induced by specific allergen immunotherapy, we estimated aaIgE in bee-allergic patients before, during, and after bee-venom immunotherapy (BVIT) in relation to the outcome of a provocation test with a living bee (PT). During the first year of BVIT, there was no significant change in either free or combined aaIgE, but aaIgE decreased during protracted BVIT over 3-7 years. By using two monoclonal anti-IgE antibodies with different epitope specificity (Le27 and BSW17), we were able to detect two kinds of IgE/aaIgE immune complexes. Our data show that during and after BVIT the levels of one kind of IgE-aaIgE immune complex (the non-BSW17 type) tended to decrease in PT-negative patients but stayed elevated in PT-positive patients. The levels of the other kind of immune complex (the non-Le27 type) were similar in treatment failures and successfully treated patients. These data suggest that there are various kinds of aaIgE with different in vivo functions related to their epitope specificity. Some of them (non-BSW17 type) might be associated with BVIT failure.

Naturally occurring human IgA autoantibodies against IgE-DES myeloma protein. Prevalence and specificity

The prevalence and specificity of naturally occurring human IgA anti-IgE autoantibodies (a-E Ab) were studied by ELISA with anti-IgA monoclonal antibodies (mAb) and a purified myeloma IgE as solid-phase protein, i.e., IgE-DES(kappa). Such detected IgA a-E Ab were common among adults, and significantly increased geometric means (GM) were found in patients with atopy (P = 0.006; n = 41; GM = 79.3 arbitrary units (AU)/ml) and filariasis (P = 0.02; n = 41; GM = 75.9 AU/ml), as compared with nonatopic controls (n = 42; GM = 48.8 AU/ml). No such difference was observed between age-matched nonatopic (n = 22; GM = 36.7 AU/ml) and atopic (n = 22; GM = 38.6 AU/ml) children. Children had significantly (P < 0.001) lower IgA a-E Ab concentrations than adults, probably as a result of age, because IgA a-E Ab concentrations and age of children were significantly correlated (n = 44; P < 0.05; r = 0.30). IgA a-E Ab concentrations were very low in cord serum (n = 32; median < 0.1 AU/ml). Sex did not influence IgA a-E Ab concentrations in any study group. The specificity of IgA a-E Ab in nine sera was studied by ELISA inhibition assay using IgE-DES myeloma as solid-phase protein and inhibitory proteins of the IgG, IgM, IgD, and IgE classes, including five different IgE myeloma proteins, as well as three enzymatic fragments of IgE-DES. The inhibitions indicated that all IgA a-E Ab tested reacted in a low-affinity reaction with determinants restricted to IgE-DES, i.e., the solid-phase protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Human anti-IgE antibodies by repertoire cloning

Anti-IgE antibodies have been detected in sera of patients with an allergic disease where they might play a role in the regulation of (Ig)E-mediated reactions. Using a recombinant phage surface display expression system a combinatorial library of antibody heavy and light chains was constructed from peripheral blood mononuclear cells from an atopic donor immunized with tetanus toxoid. Screening of the library allowed the identification of a large number of phages displaying human monovalent antigen-binding fragments (Phab) against tetanus toxoid and IgE. Surprisingly, we found a high frequency of Phab against particular IgE myelomas that was comparable to the frequency found for Phab against tetanus toxoid. However, most of these Phab were directed to different idiotypic determinants, depending on the IgE myeloma used for the panning procedure. Nevertheless, two clones were found to have anti-isotypic specificity and were shown to react specifically with the CH2 domain of the IgE heavy chain.