Tamara Kopp

Dimerization of the Major Birch Pollen Allergen Bet v 1 Is Important for its In Vivo IgE-Cross-Linking Potential in Mice

In type I allergy, the cross-linking of membrane IgE on B lymphocytes and of cytophilic IgE on effector cells by their respective allergens are key events. For cross-linking two IgE molecules, allergens need at least two epitopes. On large molecules, these could be different epitopes in a multivalent, or identical epitopes in a symmetrical, fashion. However, the availability of epitopes may be limited on small allergens such as Bet v 1, the major birch pollen allergen. The present work analyzes whether dimerization is required for the cross-linking capacity of this allergen. In immunoblots, murine monoclonal and polyclonal human Bet v 1-specific Abs detected, besides a Bet v 1 monomer of 17 kDa, a dimer of 34 kDa. In dynamic light scattering, Bet v 1 appeared as dimers and even multimers, but a single condition could be defined where it behaved exclusively monomerically. Small-angle x-ray scattering of the monomeric and dimeric samples resulted in diagrams agreeing with the calculated models. Circular dichroism measurements indicated that the structure of Bet v 1 was preserved under monomeric conditions. Skin tests in Bet v 1-allergic mice were positive with Bet v 1 dimer, but remained negative using the monomer. Furthermore, in contrast to dimeric Bet v 1, the monomer was less capable of activating murine memory B cells for IgE production in vivo. Our data indicate that the presentation of two identical epitopes by dimerized allergens is a precondition for cross-linking of IgE on mast cells and B lymphocytes.

Serum IgE Autoantibodies Target Keratinocytes in Patients with Atopic Dermatitis

Previous studies have shown that sera of patients with severe atopic dermatitis (AD) contain IgE specific for self-proteins, supporting the hypothesis of autoreactivity as a pathogenic factor in AD. In this study, we screened a large panel of AD patients (n=192) by western blotting (WB) for IgE reactivity not only against the human epithelial cell line A431 but also against primary keratinocytes (KCs). To investigate autoantigenic cell structures in detail, normal human skin and primary KCs were incubated with sera from both WB-reactive patients and, for control purposes, healthy individuals, and analyzed by immunohistology, confocal laser microscopy, and flow cytometry. Our analysis revealed that 28% of AD patients, but not healthy individuals, display serum IgE autoreactivity by WB analysis. The individual IgE reaction patterns of the sera pointed to the existence of unique as well as common specificities against epidermal or A431-derived proteins. Immunostainings identified cytoplasmic and, occasionally, also cell membrane-associated moieties as targets for autoreactive IgE antibodies. Interestingly, in certain autoreactive patients, the surface-staining pattern was accentuated at cellular contact sites. We conclude that IgE autoreactivity is common, particularly among severe AD patients, and that non-transformed primary cells are needed for characterization of the entire spectrum of IgE-defined autoantigens.

Hom s 4, an IgE-Reactive Autoantigen Belonging to a New Subfamily of Calcium-Binding Proteins, Can Induce Th Cell Type 1-Mediated Autoreactivity

Skin inflammation in atopic dermatitis starts with Th2 and IgE-mediated responses against exogenous allergens and, for unknown reasons, resembles features of a Th1-driven reaction in the chronic stages. We report the characterization of a human protein, Hom s 4, recognized by IgE autoantibodies from atopic dermatitis patients. The complete Hom s 4 cDNA codes for a 54-kDa basic protein containing two typical calcium-binding domains separated by an unusually long α-helical domain. Therefore, Hom s 4 and homologous proteins found by sequence comparison in mice, fruit flies, and nematodes constitute a novel subfamily of calcium-binding proteins. Using Hom s 4-specific Abs, it is demonstrated that the protein is strongly expressed within epidermal keratinocytes and dermal endothelial cells. Purified Hom s 4 showed IgE cross-reactivity with exogenous calcium-binding allergens from plants and fish but, in contrast to the exogenous allergens, induced only weak histamine release from patient basophils. However, the analysis of Hom s 4-specific cytokine and humoral immune responses indicated that Hom s 4 strongly induces Th1 responses which are accompanied by the release of IFN-γ, a cytokine implicated in epithelial cell damage. Hom s 4-induced IFN-γ production was found in normal individuals, in patients with chronic inflammatory skin diseases and in Th2-prone atopic persons, suggesting that Hom s 4 represents a protein with an intrinsic property to induce Th1-mediated autoreactivity. It may thus contribute to chronic skin inflammation in atopic as well as in nonatopic persons.

Specific roles for dendritic cell subsets during initiation and progression of psoriasis

Several subtypes of APCs are found in psoriasis patients, but their involvement in disease pathogenesis is poorly understood. Here, we investigated the contribution of Langerhans cells (LCs) and plasmacytoid DCs (pDCs) in psoriasis. In human psoriatic lesions and in a psoriasis mouse model (DKO* mice), LCs are severely reduced, whereas pDCs are increased. Depletion of pDCs in DKO* mice prior to psoriasis induction resulted in a milder phenotype, whereas depletion during active disease had no effect. In contrast, while depletion of Langerin‐expressing APCs before disease onset had no effect, depletion from diseased mice aggravated psoriasis symptoms. Disease aggravation was due to the absence of LCs, but not other Langerin‐expressing APCs. LCs derived from DKO* mice produced increased IL‐10 levels, suggesting an immunosuppressive function. Moreover, IL‐23 production was high in psoriatic mice and further increased in the absence of LCs. Conversely, pDC depletion resulted in reduced IL‐23 production, and therapeutic inhibition of IL‐23R signaling ameliorated disease symptoms. Therefore, LCs have an anti‐inflammatory role during active psoriatic disease, while pDCs exert an instigatory function during disease initiation.

Dendritic Cells in Atopic Dermatitis: Expression of FcεRI on Two Distinct Inflammation-Associated Subsets

Background: Dendritic cells (DCs) represent a major portion within the infiltrate of atopic dermatitis (AD) lesions. As antigen-presenting cells they have the ability to regulate both the quantity and quality of T-cell responses and, thus, are likely to play a key role in the pathogenesis of T-cell-dominated skin diseases such as AD. Thus we sought to identify the DC repertoire occurring in AD patients. Methods: For this purpose, we phenotypically analyzed various defined DC subsets of AD patients and healthy controls in skin biopsies and peripheral blood by immunofluorescence staining. Results: In AD lesions, two inflammation-associated DC subsets with varying expression of costimulatory molecules occurred besides epidermal Langerhans cells (LCs) and dermal myeloid DCs (dmDCs) indigenously residing in normal skin: (1) CD1a+/CD1c+/FcεRI+/IgE+/CD207– myeloid DCs (mDCs) in the epidermis and dermis and (2) CD123+/BDCA-2+/CD45RA+/CD68+ plasmacytoid DCs (pDCs) in the dermis. In the peripheral blood of the patients, these cells exhibited an immature phenotype. Interestingly, we found FcεRI and cell-bound IgE to be expressed not only on myeloid, but also on plasmacytoid DCs from both the skin and peripheral blood of AD patients. Conclusions: It is tempting to speculate that the disease-regulating role of inflammatory DCs in AD is influenced by both FcεRI occupancy and their degree of maturity.

The impact of aluminium in acid-suppressing drugs on the immune response of BALB/c mice.

Background Recently we have shown that anti‐acid drugs lead to an enhanced risk of food allergy. This may be due to hindered peptic digestion, caused by an elevation of the gastric pH. Additionally, it is known that aluminium‐linked antigens lead to an increased probability of sensitization.

Analysis of four prevalent filaggrin mutations (R501X, 2282del4, R2447X and S3247X) in Austrian and German patients with atopic dermatitis.

Background  Recently, mutations in the filaggrin gene (FLG) have been shown to be a major predisposing factor for atopic dermatitis (AD).

3D parallel coordinate systems—A new data visualization method in the context of microscopy-based multicolor tissue cytometry

Presentation of multiple interactions is of vital importance in the new field of cytomics. Quantitative analysis of multi‐ and polychromatic stained cells in tissue will serve as a basis for medical diagnosis and prediction of disease in forthcoming years. A major problem associated with huge interdependent data sets is visualization. Therefore, alternative and easy‐to‐handle strategies for data visualization as well as data meta‐evaluation (population analysis, cross‐correlation, co‐expression analysis) were developed.

Clinical and Cytological Effects of Pimecrolimus Cream 1% after Resolution of Active Atopic Dermatitis Lesions by Topical Corticosteroids: A Randomized Controlled Trial

Background: Topical pimecrolimus may maintain remissions of atopic dermatitis (AD) by inhibiting subclinical inflammation. Objective: To evaluate clinical and cytological effects of pimecrolimus in topical corticosteroid-treated and resolved AD lesions. Methods: Patients (n = 67) with resolved AD lesions were randomized to 3-week double-blind treatment with either pimecrolimus cream 1% or vehicle cream. Outcome measures were reduction in Eczema Area and Severity Index (EASI) and number of leukocytes in skin biopsies in all randomized patients who were evaluable at the end of study. Results: The proportion of patients with a localized EASI <2 at the end of study was higher with pimecrolimus cream 1% than with vehicle cream (73.5 vs. 39.4%, respectively). There was a significant decrease in the number of infiltrating CD45+ cells in pimecrolimus cream 1% compared with placebo cream (–88.2 vs. 43.2 cells/mm2, respectively, p = 0.047) and a slight but nonsignificant reduction in the number of dermal dendritic cells, Langerhans cells, T cells and macrophages with pimecrolimus versus vehicle cream. Limitations: This was an exploratory study. Conclusion: Topical pimecrolimus was effective at maintaining betamethasone-17α-valerate-induced AD remission by inhibiting recurrences of the inflammatory infiltrate in the skin.

Establishing an allergic eczema model employing recombinant house dust mite allergens Der p 1 and Der p 2 in BALB/c mice

The major house dust mite allergens Der p 1 and Der p 2 are prevalent inducers of eczema. Der p 1 is a cysteine protease disrupting epithelial barriers, whereas Der p 2 functionally mimics the LPS‐binding compound MD‐2 within the TLR4 complex. In this work, we tested the percutaneous sensitizing capacity of recombinant (r) Der p 1 and Der p 2 in BALB/c mice. Mice were sensitized by percutaneous application of low (10 μg/application) and high dose (100 μg) rDer p 1 or rDer p 2, or with rDer p 1 followed by rDer p 2. Allergen‐specific and total IgE antibodies were determined by ELISA. Eczema of BALB/c was classified by the itching score and corresponded to erosions. Infiltrating immune cells were identified by haematoxylin/eosin and Giemsa staining for eosinophils or mast cells, CD3 staining for T lymphocytes. Percutaneous treatments with rDer p 1, but not rDer p 2‐induced specific IgG1. However, cotreatment with rDer p 1 led to increase in anti‐Der p 2 IgG titres. Both allergens elicited skin erosions because of scratching, thickening of the epidermis, and eosinophil and T‐cell infiltration. Our data indicate that recombinant mite allergens in the absence of adjuvant are sufficient for inducing eczema in BALB/c mice. As the enzymatic activity of an allergen might be an important cofactor for specific sensitization via the skin, Der p 1 may act as adjuvant for other allergens too. The presented mouse model is suitable for investigating the mechanisms of allergic eczema.