Sabine Zeller

Interleukins, from 1 to 37, and interferon-γ: Receptors, functions, and roles in diseases

Advancing our understanding of mechanisms of immune regulation in allergy, asthma, autoimmune diseases, tumor development, organ transplantation, and chronic infections could lead to effective and targeted therapies. Subsets of immune and inflammatory cells interact via ILs and IFNs; reciprocal regulation and counter balance among T(h) and regulatory T cells, as well as subsets of B cells, offer opportunities for immune interventions. Here, we review current knowledge about ILs 1 to 37 and IFN-γ. Our understanding of the effects of ILs has greatly increased since the discoveries of monocyte IL (called IL-1) and lymphocyte IL (called IL-2); more than 40 cytokines are now designated as ILs. Studies of transgenic or knockout mice with altered expression of these cytokines or their receptors and analyses of mutations and polymorphisms in human genes that encode these products have provided important information about IL and IFN functions. We discuss their signaling pathways, cellular sources, targets, roles in immune regulation and cellular networks, roles in allergy and asthma, and roles in defense against infections.

Cross-Reactivity and 1.4-Å Crystal Structure of Malassezia sympodialis Thioredoxin (Mala s 13), a Member of a New Pan-Allergen Family

We have identified thioredoxins (Trx) of Malassezia sympodialis, a yeast involved in the pathogenesis of atopic eczema, and of Aspergillus fumigatus, a fungus involved in pulmonary complications, as novel IgE-binding proteins. We show that these Trx, including the human enzyme, represent cross-reactive structures recognized by serum IgE from individuals sensitized to M. sympodialis Trx. Moreover, all three proteins were able to elicit immediate-type allergic skin reactions in sensitized individuals, indicating a humoral immune response based on molecular mimicry. To analyze structural elements involved in these reactions, the three-dimensional structure of M. sympodialis Trx (Mala s 13) has been determined at 1.4-Å resolution by x-ray diffraction analysis. The structure was solved by molecular replacement and refined to a crystallographic R factor of 14.0% and a free R factor of 16.8% and shows the typical Trx fold. Mala s 13 shares 45% sequence identity with human Trx and superposition of the solved Mala s 13 structure with those of human Trx reveals a high similarity with a root mean square deviation of 1.11 Å for all Cα atoms. In a detailed analysis of the molecular surface in combination with sequence alignment, we identified conserved solvent-exposed amino acids scattered over the surface in both structures which cluster to patches, thus forming putative conformational B cell epitopes potentially involved in IgE-mediated cross- and autoreactivity.

Cross-reactivity among fungal allergens: a clinically relevant phenomenon?

Atopic patients suffering from allergic asthma, allergic rhinitis, or atopic eczema often have detectable levels of serum IgE antibodies to fungi. Although the association between fungal sensitisation and different forms of allergic diseases, including allergic asthma and life‐threatening allergic bronchopulmonary aspergillosis, is well established, the clinical relevance of cross‐reactivity among different fungal species remains largely unknown. Recent progress in molecular cloning of fungal allergens and the availability of more than 40 completely sequenced fungal genomes facilitates characterisation, cloning, and production of highly pure recombinant allergens, identification of homologous and orthologous allergens widespread among the fungal kingdom, in silico prediction, and experimental in vitro and in vivo verification of cross‐reactivity between homologous pan‐allergens. These studies indicate that cross‐reactivity is an important component of fungal sensitisation.

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.

Immunoglobulin-E-Mediated Reactivity to Self Antigens: A Controversial Issue

Immunoglobulin E (IgE) reactivity to self antigens is well established in vitro by ELISA, inhibition ELISA, Western blot analyses and T cell proliferation experiments. In vivo, IgE-binding self antigens are able to elicit strong type I reactions in sensitized individuals and, in the case of human manganese superoxide dismutase, to elicit eczematous reactions on healthy skin areas of patients suffering from atopic eczema. The reactions against self antigens sharing structural homology with environmental allergens can be plausibly explained by molecular mimicry between common B cell epitopes. For the second class of IgE-binding self antigens without sequence homology to known allergens, it is still unclear if the structures are able to induce a B cell switch to IgE production, or if the reactivity is due to sequence similarity shared with not yet detected environmental allergens. However, in all cases, cross-reactivity is never complete, indicating either a lower affinity of IgE antibodies to self allergens than to the homologous environmental allergens or the presence of additional B cell epitopes on the surface of the environmental allergens, or both. Increasing evidence shows that self allergens could play a decisive role in the exacerbation of long-lasting atopic diseases. However, the only observation supporting a clinical role of IgE-mediated autoreactivity is confined to the fact that IgE levels against self antigens correlate with disease severity.

Molecular and immunological characterization of Asp f 34, a novel major cell wall allergen of Aspergillus fumigatus

Background:  Although fungal spores have been recognized as triggers of respiratory allergy and asthma, only two allergenic fungal cell wall components have so far been described.

Auto- and cross-reactivity to thioredoxin allergens in allergic bronchopulmonary aspergillosis

Background:  Thioredoxins are cross‐reactive allergens involved in the pathogenesis of atopic eczema and asthma. Cross‐reactivity to human thioredoxin can contribute to the exacerbation of severe atopic diseases.

HIV interferes with SOCS‐1 and ‐3 expression levels driving immune activation

HIV infection is characterized by sustained immune activation, which is reflected by activated T cells and, in particular, by increased levels of phosphorylated STAT proteins. Here, we hypothesized that T‐cell activation in HIV infection is partially due to the inability of SOCS‐1 and SOCS‐3 to control the JAK/STAT pathway. We found higher levels of SOCS‐1/3 mRNA levels in CD4+ T cells of HIV‐infected patients than in healthy controls. However, SOCS protein levels were lower, explaining the lack of attenuation of the JAK/STAT pathway. Infection of CD4+ T cells alone did not activate STATs, while ex vivo infection of PBMC did, indicating that non‐T cells critical for shaping the immune response, e.g. DC were responsible for the STAT‐1 activation. Supernatants from ex vivo‐infected PBMC transferred to CD4+ T cells induced JAK/STAT activation, pointing to a central role of soluble factors. Notably, over‐expression of SOCS‐1/3 in CD4+ T cells prevented JAK/STAT activation. Thus, HIV infection interferes with SOCS‐1/3 expression driving immune activation. Sustained immune activation disrupts the lymphoid system and favors HIV replication since HIV preferentially infects activated cells. We speculate that regulating SOCS may be a potential way to counteract immune activation in HIV disease.

Structural aspects and clinical relevance of Aspergillus fumigatus antigens/allergens

Robotics-based high throughput screening of Aspergillus fumigatus cDNA libraries displayed on phage surfaces revealed at last 81 different structures able to bind IgE from serum of patients sensitized to this fungus. Among these, species-specific as well as phylogenetically highly conserved structures and such with unknown function have been detected. A subset of cDNAs have been used to produce and characterize the corresponding recombinant allergens which have proven to be useful diagnostic reagents allowing specific detection of A. fumigatus sensitization and differential diagnosis of allergic bronchopulmonary aspergillosis. Phylogenetically highly conserved structures like manganese-dependent superoxide dismutase, P2 acidic ribosomal protein, cyclophilins and thioredoxins induce, beyond sensitization, IgE antibodies able to cross-react with the corresponding homologous self antigens. These reactions, likely to contribute to the exacerbation and perpetuation of allergic bronchopulmonary aspergillosis, can be traced back to shared conformational B-cell epitopes build up from conserved amino acid residues scattered over the surface of the molecules as shown by detailed analyses of the crystal structures.

The Ige-Binding Self-Antigens Tubulin-ÃÂ and HLA-DR-ÃÂ are Overexpressed in Lesional Skin of Atopic Eczema Patients

Background: Atopic eczema is the most common chronic, relapsing, inflammatory skin disorder with an atopic background. Previous studies have shown that IgE-mediated reactivity to self-antigens plays a role in the pathogenesis of the disease. However, the expression of self-antigens associated with atopic eczema in the lesional skin is poorly investigated.Aim of the study: This study was aimed to show that IgE-binding self antigens are over-expressed in atopic eczema lesions. Methods: Tubulin-α and HLA-DR-α, two recently described self-antigens, were stained by immunohistochemistry in skin specimens from chronic and acute atopic eczema lesions, unaffected skin from the same patients or skin from healthy controls.Results: The expression of tubulin-α and HLA-DR-α is up-regulated in atopic eczema lesions compared to nonlesional or healthy skin and correlates with the number of infiltrating immune cells and the degree of inflammation.Conclusion: Upregulation of IgE-binding self-antigens in lesional skin of atopic eczema patients might further promote the existing inflammation and induce exacerbations of the disease in the absence of exposure to environmental allergens.