Serum IgE autoantibodies target keratinocytes in patients with atopic dermatitis. J Invest Dermatol. 2008;128:2232-2239. [PMID: 18480840 DOI: 10.1038/jid.2008.80]

Immunoglobulin E-binding autoantigens: biochemical characterization and clinical relevance

Although immediate-Type I skin reactions to human dander have been described six decades ago, only the recent application of molecular biology to allergology research allowed fast and detailed characterization of IgE-binding autoantigens. These can be functionally subdivided into three classes: (1) self-antigens with sequence homology to environmental allergens belonging to the class of phylogenetically conserved proteins, (2) self-antigens without sequence homology to known environmental allergens, and (3) chemically modified self-antigens deriving from workplace exposure. As environmental allergens, also IgE-binding autoantigens belong to different protein families without common structural features that would explain their IgE-binding capability. Many of the self-antigens showing sequence homology to environmental allergens, are phylogenetically conserved proteins like manganese dependent superoxide dismutase, thioredoxin or cyclopilin. Their IgE-binding capability can be explained by molecular mimicry resulting from shared B-cell epitopes. A common factor of IgE-binding self-antigens without sequence homology to known environmental allergens is that they elicit IgE responses only in individuals suffering from long-lasting atopic diseases. In contrast, IgE-mediated reactions to modified self-antigens might be explained with the generation of novel B-cell epitopes. Chemically modified self-antigens are likely to be recognized as non-self by the immune system. The clinical relevance of IgE responses to self-antigens remains largely unclear. Well documented is their ability to induce immediate Type I skin reactions in vivo, and to induce mediator release from effector cells of sensitized individuals in vitro. Based on these observations it is reasonable to assume that IgE-mediated cross-linking of FcRIε receptors on effector cells can elicit the same symptoms as those induced by environmental allergens, and this could explain exacerbations of chronic allergic diseases in the absence of external exposure. However, because most of the described IgE-binding self-antigens are intracellular proteins normally not accessible for antigen-antibody interactions, local release of the antigens is required to explain the induction of symptoms.

Presence of functional, autoreactive human milk-specific IgE in infants with cow's milk allergy

BACKGROUND

Occasionally, exclusively breastfed infants with cow's milk allergy (CMA) remain symptomatic despite strict maternal milk avoidance.

OBJECTIVE

To determine whether or not persistence of symptoms could be due to sensitization against endogenous human milk proteins with a high degree of similarity to bovine allergens.

METHODS

Ten peptides representing known bovine milk IgE-binding epitopes [α-lactalbumin (ALA), β- and κ-casein] and the corresponding, highly homologous human milk peptides were labelled with sera from 15 breastfed infants with CMA, aged 3 weeks to 12 months, and peptide (epitope)-specific IgE antibodies were assessed. Nine of the 15 breastfed infants became asymptomatic during strict maternal avoidance of milk and other major food allergens; six infants remained symptomatic until weaned. Ten older children, aged 5-15 years, with CMA were also assessed. The functional capacity of specific IgE antibodies was assessed by measuring β-hexosaminidase release from rat basophilic leukaemia cells passively sensitized and stimulated with human and bovine ALA.

RESULTS

A minimum of one human milk peptide was recognized by IgE antibodies from 9 of 15 (60%) milk-allergic infants, and the majority of older children with CMA. Genuine sensitization to human milk peptides in the absence of IgE to bovine milk was occasionally seen. There was a trend towards specific IgE being detected to more human milk peptides in those infants who did not respond to the maternal milk elimination diet than in those who did (P = 0.099). Functional IgE antibody to human ALA was only detected in infants not responding to the maternal diet.

CONCLUSIONS AND CLINICAL RELEVANCE

Endogenous human milk epitopes are recognized by specific IgE from the majority of infants and children with CMA. Such autoreactive, human milk-specific IgE antibodies appear to have functional properties in vitro. Their role in provoking allergic symptoms in infants exclusively breastfed by mothers strictly avoiding dietary milk remains unclear.

Atopic dermatitis - from new pathophysiologic insights to individualized therapy

Recently, important novel insights into the complex pathophysiology of atopic dermatitis (AD) have been gained. However, in most cases the therapy of AD is limited to base line therapy with emollients combined with symptomatic, rather general immunosuppressive treatment approaches of the flare-ups. Latest research findings together with experiences from daily clinical practice, which support the concept that a combination of general disease features together with specific trigger factors in the individual patients drive the disease, might be helpful for a subclassification of patients with AD based on the most relevant pathophysiologic modifications. Subclassification of patients with AD seems indispensable to introduce rationale-based, individualized treatment approaches of AD, which target specific modified pathways. In this review, we provide an overview about a selection of pathophysiologic pathways, which hold promise to represent targets of such therapeutic approaches in the near future.

Contrasting pathogenesis of atopic dermatitis and psoriasis--part I: clinical and pathologic concepts

Atopic dermatitis and psoriasis are 2 of the most common inflammatory skin diseases. They are similar in that they are complex inherited diseases involving genes that encode immune components and structural proteins that regulate differentiation of epidermal cells. Each disease is characterized by proliferation of epidermal keratinocytes and abnormal cornification or terminal differentiation in the epidermis; skin lesions contain immune infiltrates of T cells, dendritic cells, and other types of leukocytes. We review similarities between the diseases and differences in epidermal barrier defects and immune cells. We also propose mechanisms of pathogenesis based on differences in the balance of immune cell subsets that could cause the phenotypes that distinguish these diseases. The first part of this 2-part review focuses on the clinical and pathologic features of the diseases; the second part discusses differences in immune cell subsets between atopic dermatitis and psoriasis and recent therapeutic strategies.

[Natural history of atopic dermatitis-outside-inside-outside story-]

In this review, I summarized recent studies about nonatopic dermatitis, IgE associated atopic dermatitis and autoallergic atopic dermatitis in the natural history of atopic dermatitis with gene -gene and gene -environment interaction. Also, new hypothesis of the mechanism of atopic dermatitis which was called OUTSIDE-INSIDE-OUTSIDE story wes introduced.

Therapeutic Implications of a Barrier-based Pathogenesis of Atopic Dermatitis

In this review, I first provide relevant background information about normal epidermal barrier structure and function. I then update recent information about how inherited defects in either filaggrin and/or in the serine protease inhibitor, lymphoepithelial Kazal-type inhibitor 1, converge to stimulate the development of atopic dermatitis (AD). Next I explain the multiple mechanisms whereby a primary barrier abnormality in AD can lead to inflammation. Furthermore, I explore how certain acquired stressors, such as a reduced external humidity, high pH soaps/surfactants, psychological stress, as well as secondary Staphylococcus aureus infections initiate or further aggravate AD. Finally, and most importantly, I compare various therapeutic paradigms for AD, highlighting the risks and benefits of glucocorticoids and immunomodulators vs. corrective, lipid replacement therapy.

Recent insights into atopic dermatitis and implications for management of infectious complications

Atopic dermatitis (AD) is a common complex disease that frequently follows a chronic relapsing course and affects the quality of life of patients and families in a significant manner. New insights into the pathophysiology of AD point to an important role of structural abnormalities in the epidermis combined with immune dysregulation. Patients with AD have a unique predisposition to colonization or infection by a number of microbial organisms, most notably Staphylococcus aureus and herpes simplex virus. A multipronged approach directed at healing or protecting the skin barrier and addressing the immune dysregulation is necessary to improve the likelihood of successful outcomes.

Abnormal skin barrier in the etiopathogenesis of atopic dermatitis

PURPOSE OF REVIEW

Many recent studies have revealed the key roles played by Th1/Th2 cell dysregulation, IgE production, mast cell hyperactivity, and dendritic cell signaling in the pathogenesis of atopic dermatitis. Accordingly, current therapy has been largely directed towards ameliorating Th2-mediated inflammation and/or pruritus. We will review here emerging evidence that the inflammation in atopic dermatitis results from inherited and acquired insults to the barrier and the therapeutic implications of this new paradigm.

RECENT FINDINGS

Recent molecular genetic studies have shown a strong association between mutations in FILAGGRIN and atopic dermatitis, particularly in Northern Europeans. But additional acquired stressors to the barrier are required to initiate inflammation. Sustained hapten access through a defective barrier stimulates a Th1 --> Th2 shift in immunophenotype, which in turn further aggravates the barrier. Secondary Staphylococcus aureus colonization not only amplifies inflammation but also further stresses the barrier in atopic dermatitis.

SUMMARY

These results suggest a new 'outside-to-inside, back to outside' paradigm for the pathogenesis of atopic dermatitis. This new concept is providing impetus for the development of new categories of 'barrier repair' therapy.

Abnormal skin barrier in the etiopathogenesis of atopic dermatitis

Prior studies revealed the key roles played by T-helper type 1 and type 2 (Th1/Th2) cell dysregulation, IgE production, mast cell hyperactivity, and dendritic cell signaling in the evolution of the chronic, pruritic, inflammatory dermatosis that characterizes atopic dermatitis (AD). Accordingly, current therapy has been largely directed toward ameliorating Th2-mediated inflammation and pruritus. This article reviews emerging evidence that the inflammation in AD results from inherited and acquired insults to the barrier, as well as the therapeutic implications of this new paradigm.

History of atopy or autoimmunity increases risk of alopecia areata

BACKGROUND

The association between a history of atopy or autoimmune diseases and risk of alopecia areata (AA) is not well established.

OBJECTIVE

The purpose of this study was to use the National AA Registry database to further investigate the association between history of atopy or autoimmune diseases and risk of AA.

METHODS

A total of 2613 self-registered sporadic cases (n = 2055) and controls (n = 558) were included in this analysis.

RESULTS

Possessing a history of any atopic (odds ratio = 2.00; 95% confidence interval 1.50-2.54) or autoimmune (odds ratio = 1.73; 95% confidence interval 1.10-2.72) disease was associated with an increased risk of AA. There was no trend for possessing a history of more than one atopic or autoimmune disease and increasing risk of AA.

LIMITATIONS

Recall, reporting, and recruiting bias are potential sources of limitations in this analysis.

CONCLUSION

This analysis revealed that a history of atopy and autoimmune disease was associated with an increased risk of AA and that the results were consistent for both the severe subtype of AA (ie, alopecia totalis and alopecia universalis) and the localized subtype (ie, AA persistent).

Exploring the repertoire of IgE-binding self-antigens associated with atopic eczema

BACKGROUND

Atopic eczema (AE) is the most common chronic inflammatory skin disease. Recent data demonstrate the presence of autoreactive serum IgE antibodies correlating with the severity of the disease.

OBJECTIVE

Although several IgE-binding self-antigens have been reported, the whole repertoire of IgE-binding self-antigens is unknown. We aimed to estimate the repertoire size of autoreactive proteins related to AE and clone, produce, and characterize humoral and T-cell responses against novel self-antigens.

METHODS

Phage surface-displayed human cDNA libraries were enriched for clones binding to serum IgE from patients with AE and screened by using high-throughput technology. Selected clones were used to produce the encoded proteins, to test their IgE-binding ability in Western blots and ELISAs, and their ability to induce mediator release from basophils of sensitized individuals.

RESULTS

One hundred forty sequences encoding potential IgE-binding self-antigens associated with AE were identified. Sixteen sequences encoded already described self-antigens. Three new sequences showed homology with environmental allergens, 86 encoded known human proteins, 7 predicted proteins, and 28 showed sequence identity with genomic contigs. Immunoblotting and ELISA experiments demonstrated the presence of IgE antibodies in sera from patients with AE to 5 selected recombinant self-antigens and their ability to induce mediator release from basophils of patients with AE who have self-antigen-specific IgE antibodies.

CONCLUSION

These data demonstrate a broad spectrum of at least 140 IgE-binding self-antigens associated with AE. By binding IgE antibodies or activating specific T cells, they might promote, perpetuate, or both existing skin inflammation.

Linking allergy to autoimmune disease

Type I allergy is a classical Th2-driven hypersensitivity disease based on IgE recognition of environmental allergens. Exposure of allergic individuals to exogenous allergens leads to immediate type inflammation caused by degranulation of mast cells via IgE-allergen immune complexes and the release of inflammatory mediators, proteases and pro-inflammatory cytokines. However, allergic inflammation can occur and persist in the absence of exposure to exogenous allergens and might paradoxically resemble a Th1-mediated chronic inflammatory reaction. We summarize evidence supporting the view that autoimmune mechanisms might contribute to these processes. IgE recognition of autoantigens might augment allergic inflammation in the absence of exogenous allergen exposure. Moreover, autoantigens that activate Th1-immune responses could contribute to chronic inflammation in allergy, thus linking allergy to autoimmunity.