Carsten B. Schmidt-Weber

Immune Responses in Healthy and Allergic Individuals Are Characterized by a Fine Balance between Allergen-specific T Regulatory 1 and T Helper 2 Cells

The mechanisms by which immune responses to nonpathogenic environmental antigens lead to either allergy or nonharmful immunity are unknown. Single allergen-specific T cells constitute a very small fraction of the whole CD4+ T cell repertoire and can be isolated from the peripheral blood of humans according to their cytokine profile. Freshly purified interferon-γ–, interleukin (IL)-4–, and IL-10–producing allergen-specific CD4+ T cells display characteristics of T helper cell (Th)1-, Th2-, and T regulatory (Tr)1–like cells, respectively. Tr1 cells consistently represent the dominant subset specific for common environmental allergens in healthy individuals; in contrast, there is a high frequency of allergen-specific IL-4–secreting T cells in allergic individuals. Tr1 cells use multiple suppressive mechanisms, IL-10 and TGF-β as secreted cytokines, and cytotoxic T lymphocyte antigen 4 and programmed death 1 as surface molecules. Healthy and allergic individuals exhibit all three allergen-specific subsets in different proportions, indicating that a change in the dominant subset may lead to allergy development or recovery. Accordingly, blocking the suppressor activity of Tr1 cells or increasing Th2 cell frequency enhances allergen-specific Th2 cell activation ex vivo. These results indicate that the balance between allergen-specific Tr1 cells and Th2 cells may be decisive in the development of allergy.

Th22 cells represent a distinct human T cell subset involved in epidermal immunity and remodeling

Th subsets are defined according to their production of lineage-indicating cytokines and functions. In this study, we have identified a subset of human Th cells that infiltrates the epidermis in individuals with inflammatory skin disorders and is characterized by the secretion of IL-22 and TNF-alpha, but not IFN-gamma, IL-4, or IL-17. In analogy to the Th17 subset, cells with this cytokine profile have been named the Th22 subset. Th22 clones derived from patients with psoriasis were stable in culture and exhibited a transcriptome profile clearly separate from those of Th1, Th2, and Th17 cells; it included genes encoding proteins involved in tissue remodeling, such as FGFs, and chemokines involved in angiogenesis and fibrosis. Primary human keratinocytes exposed to Th22 supernatants expressed a transcriptome response profile that included genes involved in innate immune pathways and the induction and modulation of adaptive immunity. These proinflammatory Th22 responses were synergistically dependent on IL-22 and TNF-alpha. Furthermore, Th22 supernatants enhanced wound healing in an in vitro injury model, which was exclusively dependent on IL-22. In conclusion, the human Th22 subset may represent a separate T cell subset with a distinct identity with respect to gene expression and function, present within the epidermal layer in inflammatory skin diseases. Future strategies directed against the Th22 subset may be of value in chronic inflammatory skin disorders.

GATA3-Driven Th2 Responses Inhibit TGF-β1–Induced FOXP3 Expression and the Formation of Regulatory T Cells

Transcription factors act in concert to induce lineage commitment towards Th1, Th2, or T regulatory (Treg) cells, and their counter-regulatory mechanisms were shown to be critical for polarization between Th1 and Th2 phenotypes. FOXP3 is an essential transcription factor for natural, thymus-derived (nTreg) and inducible Treg (iTreg) commitment; however, the mechanisms regulating its expression are as yet unknown. We describe a mechanism controlling iTreg polarization, which is overruled by the Th2 differentiation pathway. We demonstrated that interleukin 4 (IL-4) present at the time of T cell priming inhibits FOXP3. This inhibitory mechanism was also confirmed in Th2 cells and in T cells of transgenic mice overexpressing GATA-3 in T cells, which are shown to be deficient in transforming growth factor (TGF)-β–mediated FOXP3 induction. This inhibition is mediated by direct binding of GATA3 to the FOXP3 promoter, which represses its transactivation process. Therefore, this study provides a new understanding of tolerance development, controlled by a type 2 immune response. IL-4 treatment in mice reduces iTreg cell frequency, highlighting that therapeutic approaches that target IL-4 or GATA3 might provide new preventive strategies facilitating tolerance induction particularly in Th2-mediated diseases, such as allergy.

Decreased FOXP3 protein expression in patients with asthma.

Background:u2002 T‐regulatory cells (Treg) are important in balancing immune responses and maintaining peripheral tolerance. Current evidence suggests that asthma is characterized by a relative deficiency in Treg, allowing T helper 2 cells to expand. In this study, we aimed to evaluate circulating Treg, defined by the protein FOXP3, in both control subjects and patients with stable asthma.

Mutual Antagonism of T Cells Causing Psoriasis and Atopic Eczema

The simultaneous occurrence of psoriasis driven by type 1 helper T (Th1) cells and type 17 helper T (Th17) cells and atopic eczema dominated by type 2 helper T (Th2) cells is rare. Here, we describe three patients with co-occurring psoriasis and atopic eczema with an antagonistic course and distinct T-cell infiltrates in lesions from psoriasis and those from atopic eczema. Sensitized patients with psoriasis had a reaction to epicutaneous allergen challenge, with clinically and histologically verified eczema lesions containing a large number of allergen-reactive T cells. These findings support a causative role for T cells triggered by specific antigens in both psoriasis and atopic eczema. (Supported by the German Research Foundation and others.)

IL-22 and TNF-α represent a key cytokine combination for epidermal integrity during infection with Candida albicans

T cells exercise their full impact on target cells through a combination of secreted cytokines. The recently described T helper cell subset Th22 is characterized by a combinatorial secretion of IL‐22 and TNF‐α. Here, we demonstrate that IL‐22 increases the TNF‐α‐dependent induction and secretion of several immune‐modulatory molecules such as initial complement factors C1r and C1s, antimicrobial peptides S100A7 and HBD‐2 (human β defensin 2), and antimicrobial chemokines CXCL‐9/‐10/‐11 in primary human keratinocytes. The synergism of IL‐22 and TNF‐α is transmitted intracellularly by MAP kinases and downstream by transcription factors of the AP‐1 family. The induction of innate immunity is relevant in an in vitro infection model, where keratinocytes stimulated with Th22 supernatants or recombinant IL‐22 plus TNF‐α effectively inhibit the growth of Candida albicans and maintain survival of epithelia. Accordingly, the combinatorial stimulation of keratinocytes with IL‐22 and TNF‐α most efficiently conserves the integrity of the epidermal barrier in a three‐dimensional skin infection model as compared with IFN‐γ, IL‐17, IL‐22 or TNF‐α alone. In summary, we demonstrate that IL‐22 and TNF‐α represent a potent, synergistic cytokine combination for cutaneous immunity.

Intraindividual genome expression analysis reveals a specific molecular signature of psoriasis and eczema

Signatures from patients with both psoriasis and eczema contribute to understanding disease pathogenesis and diagnosis. Discrimination That’s Skin Deep A molecular signature may be able to aid in the differential treatment of psoriasis from eczema. Quaranta et al. examined a group of individuals affected by both psoriasis and eczema and compared molecular signatures from psoriasis and eczema lesions on the same individual. This approach limited noise from interindividual variability, allowing the authors to focus on genes involved in disease pathogenesis. They found that psoriasis-specific genes involved not only immune mediators but also regulators of metabolism. In contrast, eczema-related genes included those related to the epidermal barrier and inflammasome activation. These insights provide not only new targets for disease-specific therapies but also an independently verified classifier that can be used in difficult to diagnose patients. Previous attempts to gain insight into the pathogenesis of psoriasis and eczema by comparing their molecular signatures were hampered by the high interindividual variability of those complex diseases. In patients affected by both psoriasis and nonatopic or atopic eczema simultaneously (n = 24), an intraindividual comparison of the molecular signatures of psoriasis and eczema identified genes and signaling pathways regulated in common and exclusive for each disease across all patients. Psoriasis-specific genes were important regulators of glucose and lipid metabolism, epidermal differentiation, as well as immune mediators of T helper 17 (TH17) responses, interleukin-10 (IL-10) family cytokines, and IL-36. Genes in eczema related to epidermal barrier, reduced innate immunity, increased IL-6, and a TH2 signature. Within eczema subtypes, a mutually exclusive regulation of epidermal differentiation genes was observed. Furthermore, only contact eczema was driven by inflammasome activation, apoptosis, and cellular adhesion. On the basis of this comprehensive picture of the pathogenesis of psoriasis and eczema, a disease classifier consisting of NOS2 and CCL27 was created. In an independent cohort of eczema (n = 28) and psoriasis patients (n = 25), respectively, this classifier diagnosed all patients correctly and also identified initially misdiagnosed or clinically undifferentiated patients.

Unique Phenotype of Human Tonsillar and In Vitro-Induced FOXP3+CD8+ T Cells

Forkhead box p3 (FOXP3) is known to program the acquisition of suppressive capacities in CD4+ regulatory T cells (Treg), whereas its role in CD8+ T cells is unknown. The current study investigates whether FOXP3 also acts as a Treg master switch in peripheral blood and tonsillar CD8+ T cells. Single-cell analyses reveal the existence of a FOXP3+CD8+ population in human tonsils, whereas FOXP3+CD8+ T cells are rarely detected in peripheral blood. Tonsillar FOXP3+CD8+ T cells exhibit a Treg phenotype with high CTLA-4 and CD45RO and low CD127 and CD69 expression. Interestingly, the tonsillar FOXP3+CD8+ T cells are mostly CD25negative and some cells also express the proinflammatory cytokines TNF-α, IFN-γ, or IL-17A. Particularly, IL-17A-expressing cells are present among FOXP3+CD8+ T cells. Even though FOXP3 expression is at the detection limit in peripheral blood CD8+ T cells ex vivo, it can be induced in vitro in naive CD8+ T cells by polyclonal stimulation. The induced FOXP3+CD8+ T cells are predominantly CD25high and CD28high and similar to tonsillar cells, they produce high levels of TNF-α, IFN-γ, and granzyme B. However, IL-4 expression is mutually exclusive and IL-17A expression is not detectable. These FOXP3+CD8+ T cells suppress the proliferation of CD4+ T cells in cocultures, while showing no direct cytotoxic activity. In conclusion, the current study characterizes FOXP3-expressing CD8+ T cells from human tonsils and shows that in vitro activation leads to FOXP3 expression in CD8+ T cells and gain of suppressive activity.

Human IL-31 is induced by IL-4 and promotes TH2-driven inflammation.

BACKGROUNDnThe pruritic cytokine IL-31 has been shown to be expressed by murine activated effector T Lymphocytes of a TH2 phenotype. Like IL-17 and IL-22, IL-31 is a tissue-signaling cytokine the receptor of which is mainly found on nonimmune cells. An overabundance of IL-31 has been shown in patients with atopic disorders, including dermatitis, as well as asthma, and therefore represents a promising drug target, although its regulation in the context of the human TH2 clusters is not yet known.nnnOBJECTIVEnWe sought to address the gene regulation of human IL-31 and to test whether IL-31 possesses a similar proallergic function as members of the human TH2 cytokine family, such as IL-4, IL-5, and IL-13.nnnMETHODSnPolyclonal and purified protein derivative of tuburculin-specific T-cell clones were generated. TH phenotype was determined, and IL-31 was measured by means of ELISA. Gene expression of primary bronchial epithelial cells treated with IL-31 was also measured.nnnRESULTSnIL-31 was expressed by all of the TH2 clones and not by TH1, TH17, or TH22. This expression was dependent on autocrine IL-4 expression from these clones because it could be reduced if blocking antibodies to IL-4 were present. Interestingly, TH1 clones were able to express IL-31 if IL-4 was added to culture. This IL-31 expression was transient and did not affect the phenotype of the TH1 clones. IL-31 was able to induce proinflammatory genes, such as CCL2 and granulocyte colony-stimulating factor.nnnCONCLUSIONnIL-31 is not a TH2 cytokine in the classical sense but is likely to be expressed by a number of cells in an allergic situation in which IL-4 is present and possibly contribute to the allergic reaction.

IL-22 suppresses IFN-γ–mediated lung inflammation in asthmatic patients

BACKGROUNDnIL-22 controls tissue homeostasis by both proinflammatory and anti-inflammatory effects. However, the anti-inflammatory mechanisms of IL-22 remain poorly investigated.nnnOBJECTIVEnWe sought to investigate the anti-inflammatory role for IL-22 in human asthma.nnnMETHODSnT-cell lines derived from lung biopsy specimens of asthmatic patients were characterized by means of flow cytometry. Human bronchial epithelial cells from healthy and asthmatic subjects were stimulated with IL-22, IFN-γ, or the combination of both cytokines. Effects of cytokine stimulation were investigated by using whole-genome analysis, ELISA, and flow cytometry. The functional consequence of cytokine stimulation was evaluated in an in vitro wound repair model and T cell-mediated cytotoxicity experiments. In vivo cytokine expression was measured by using immunohistochemistry and Luminex assays in bronchoalveolar lavage fluid of healthy and asthmatic patients.nnnRESULTSnThe current study identifies a tissue-restricted antagonistic interplay of IL-22 and the proinflammatory cytokine IFN-γ. On the one hand, IFN-γ antagonized IL-22-mediated induction of the antimicrobial peptide S100A7 and epithelial cell migration in bronchial epithelial cells. On the other hand, IL-22 decreased epithelial susceptibility to T cell-mediated cytotoxicity by inhibiting the IFN-γ-induced expression of MHC-I, MHC-II, and CD54/intercellular adhesion molecule 1 molecules. Likewise, IL-22 inhibited IFN-γ-induced secretion of the proinflammatory chemokines CCL5/RANTES and CXCL10/interferon-inducible protein 10 in vitro. Consistently, the IL-22 expression in bronchoalveolar lavage fluid of asthmatic patients inversely correlated with the expression of CCL5/RANTES and CXCL10/interferon-inducible protein 10 in vivo.nnnCONCLUSIONSnIL-22 might control the extent of IFN-γ-mediated lung inflammation and therefore play a tissue-restricted regulatory role.