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• Exogenous T cell stimulation results in functional, psoriasis specific in situ activation of resident T cells in ex vivo cultured psoriasis skin. • Resumed skin T cell activities recapitulate in bona fide the inflammatory environment found in psoriasis lesions in vivo. • Histopathological features are maintained during ex vivo culture. • The model offers a versatile tool for pharmacological testing as well as for investigating the inflammatory pathways of psoriasis. Psoriasis is a chronic, inflammatory skin disorder resulting from a complex interplay between immune and skin cells via release of soluble mediators. While a lot is known about the molecular mechanisms behind psoriasis pathogenesis, there is still a need for preclinical research models that accuratelyreplicate the disease. This study aimed to develop and characterize ex vivo culture of psoriasis skin as a model for pharmacological testing, where the immunological events of psoriasis can be followed. Full thickness punch biopsies of lesional psoriasis skin were cultured in submerged conditions up to 144 h following in situ T cell stimulation with rhIL-23 and anti-CD3 and anti-CD28 antibodies. The T cell mediated skin inflammation was assessed by gene and protein l analysis for a panel of inflammatory mediators. Tissue integrity and morphology were evaluated by histological analysis. T cell stimulation resulted in functional and psoriasis specific in situ activation of T cells. The expression levels of most of the proinflammatory mediators related to both immune and skin cells were comparable to these in freshly isolated tissue at 48 and 96 h of culture. Tissue integrity and morphology were sustained up to 96 h. Treatment with a corticosteroid reduced the expression of several pro-inflammatory cytokines and chemokines, whereas anti-IL-17A antibody treatment reduced the expression of the IL-17A downstream markers IL-8 and DEFB4. By preserving keyimmunopathological mechanisms of psoriasis, ex vivo culture of psoriasis skin can be used for the investigation of inflammatory processes of psoriasis and for preclinical drug discovery research. [ABSTRACT FROM AUTHOR]

Cutaneous T-cell lymphomas (CTCLs) are the most common primary skin lymphomas, which are characterized by an accumulation of malignant T cells in the skin. The early lesion resembles both clinically and histologically benign inflammatory disorders and also presents with hyperproliferative epidermis and T-cell infiltration. Despite considerable progress in understanding the molecular mechanisms involved in the malignant transformation of T cells, the causes of the morphological and histopathological features of the disease are largely unknown. We used an organotypic model of CTCL to show that malignant T cells through the secretion of galectin-1 and -3 stimulate vigorous growth of keratinocytes. In parallel, malignant T cells induce disorganized keratinocyte stratification, resembling the early hyperproliferative stage of CTCL. We also observed a loss of attachment between the epithelial and mesenchymal compartments. In addition, hyperproliferation was followed by a downregulation of differentiation markers, such as keratin 10 and involucrin, and a decrease in barrier formation. In conclusion, we provide evidence that malignant T cells orchestrate the histopathological epidermal changes seen in CTCL. [ABSTRACT FROM AUTHOR]

Abstract: Recently it has become clear that interferon (IFN)-α, a type I interferon produced rapidly in response to infection, not only plays a key role in innate immunity, but also promotes adaptive immune responses by influencing the production or function of other cytokines. During infections IFN-α fosters the production of IL-15, which plays a pivotal role in the development, survival and function of NK cells and recruitment and activation of T cells. Since these two cytokines exert overlapping functions during infections, this investigation was undertaken to study the priming effect of IFN-α on the effect of IL-15 on human T and NK cells. We show that IFN-α induces an increased expression of IL-15Rα in human activated peripheral T cells, and in CD8+ and CD4+ T-cell lines. Functionally, the IFN-α-enhanced IL-15Rα expression resulted in an enhanced IL-15-mediated phosphorylation of STAT5 and STAT3 followed by a further increase in IL-15Rα expression. Moreover, IFN-α significantly increased the IL-15-induced cytotoxic activity of freshly isolated T and NK cells. Taken together, our data show that IFN-α boosts signaling and functional effects of IL-15, at least in part by fostering the increased IL-15R expression, thus add new facet to the emerging role of IFN-α as an important primer of adaptive immune responses. [Copyright &y& Elsevier]

IFN-α and skin-infiltrating activated T lymphocytes have important roles in the pathogenesis of psoriasis. T cells from psoriatic patients display an increased sensitivity to IFN-α, but the pathological mechanisms behind the hyperresponsiveness to IFN-α remained unknown. In this study, we show that psoriatic T cells display deficient expression of the suppressor of cytokine signaling (SOCS)3 in response to IFN-α and a low baseline expression of the SH2-domain-containing protein-tyrosine phosphatase (SHP)-1 when compared with skin T cells from nonpsoriatic donors. Moreover, IFN-α-stimulated psoriatic T cells show enhanced activation of JAKs (JAK1 and TYK2) and signal transducers and activators of transcription. Increased expression of SOCS3 proteins resulting from proteasomal blockade partially inhibits IFN-α response. Similarly, forced expression of SOCS3 and SHP-1 inhibits IFN-α signaling in psoriatic T cells. In conclusion, our data suggest that loss of regulatory control is involved in the aberrant hypersensitivity of psoriatic T cells to IFN-α. [ABSTRACT FROM AUTHOR]

The CD30-positive lymphoproliferations encompass a spectrum of disorders that share histological and phenotypic similarities but differ markedly in clinical behaviour. The basis for this diversity is not known, but it has been proposed that immune suppression by cytokines and/or regulatory T-cells (Tregs) may be implicated. In this study, skin biopsies from lymphomatoid papulosis (LyP) ( n = 14), primary cutaneous anaplastic large cells lymphoma (C-ALCL) ( n = 13) and systemic anaplastic large cells lymphoma (S-ALCL) with ( n = 9) or without ( n = 6) ALK expression were examined by immunohistology for FOXP3 expression in tumour cells and tumour infiltrating Tregs. Labelling of a majority of the neoplastic cells was seen in one case of C-ALCL. Another three cases (one LyP and two C-ALCL) displayed weak labelling of very occasional atypical T-cells. In the remaining 38 cases the atypical lymphoid infiltrate was FOXP3 negative. By contrast, all biopsies contained tumour infiltrating FOXP3-positive Tregs. Significant higher numbers were recorded in ALK negative S-ALCL and LyP than in C-ALCL and S-ALCL positive for ALK. In conclusion, it is shown that FOXP3 expression in cutaneous and systemic CD30-positive lymphoproliferations is generally confined to tumour infiltrating Tregs. These cells may have influence upon the clinical behaviour, possibly depending upon the net degree of Treg mediated immune suppression of tumour cells relative to tumour infiltrating, cytotoxic effector cells, thereby implicating the more favourable outcome of LyP compared to C-ALCL. [ABSTRACT FROM AUTHOR]

Studies the functional role of STAT6 serine phosphorylation and the kinases and phosphatases involved. Impact of the inhibition of protein phosphatase 2A on the serine phosphorylation of STAT6 and the inhibition of the DNA binding of STAT6; Analysis of pertinent topics and relevant issues; Implications on studies of enzyme catalysis and regulation.

The phosphotyrosine phosphatase SHP2 has been suggested to regulate activation of MAPK, Stat3, and Stat5 in several experimental models. In this study we investigated the role of SHP2 in IL-2 induced activation of MAPK and the Stat proteins using the human CTCL cell line MyLa2059 derived from a cutaneous T cell lymphoma (CTCL). For this purpose, MyLa2059 cells were stably transfected with wild-type SHP2 or inactive SHP2. The cells transfected with inactive SHP2 showed reduced MAPK activation upon IL-2 stimulation, suggesting that SHP2 upregulates IL-2 induced MAPK activation in T cells. However, the constitutive tyrosine phosphorylation of Stat3 as well as IL-2 induced Stat5 tyrosine phosphorylation and DNA binding were unaffected by the stably transfected wild-type SHP2 as well as the inactive SHP2. In conclusion, we show for the first time that SHP2 positively regulates IL-2 induced MAPK activation in malignant T cells. Furthermore, the results indicate that SHP2 may not be involved in the activation of Stat3 or Stat5 in CTCL cells. [ABSTRACT FROM AUTHOR]

The oncogene PIM2 is upregulated in several malignancies but has never been investigated in mycosis fungoides (MF), the most common type of cutaneous T‐cell lymphoma (CTCL). PIM2 is a well‐known oncogene and is regulated by cell signaling pathways like the JAK/STAT‐ and NF‐kB‐pathway, key regulators in the pathogenesis of CTCL. The aim of this study was to examine the role of PIM2 in MF. PIM2 gene expression was measured in 81 formalin‐fixed paraffin‐embedded skin biopsies from patients with MF and 46 control biopsies from healthy skin (HS) and benign inflammatory skin disease (BID). Validation of PIM2 protein expression was performed on selected biopsies with immunohistochemical staining. We found a significant difference in gene expression levels between both early stage MF and HS (p < 0.0001), and BID (p < 0.0001). In addition, the PIM2 gene expression was higher in advanced‐stage MF compared to early stage disease (p = 0.0001). No significant difference in gene expression levels was found between patients with and without disease progression. In conclusion, we found PIM2 expression is significantly increased in MF compared to controls, and in advanced‐stage MF compared to early stage MF. These findings could potentially have diagnostic value in discriminating early stage MF from BID. [ABSTRACT FROM AUTHOR]

Presents a study which examined the role of serine/threonine phosphatases in signal transducers and activators of transcription 3 (STAT3) signaling in human antigen-specific CD4+ T cell lines and cutaneous T cell lymphoma lines. Materials and method used; Results; Discussion.

Although impaired regeneration is important in many gastrointestinal diseases including ulcerative colitis (UC), the dynamics of mucosal regeneration in humans are poorly investigated. We have developed a model to study these processes in vivo in humans. Epithelial restitution (ER) and extracellular matrix (ECM) regulation after an experimental injury of the sigmoid colonic mucosa was assessed by repeated high-resolution endoscopic imaging, histological assessment, RNA sequencing, deconvolution analysis, and 16S rDNA sequencing of the injury niche microbiome of 19 patients with UC in remission and 20 control subjects. Human ER had a 48-h lag before induction of regenerative epithelial cells [wound-associated epithelial (WAE) and transit amplifying (TA) cells] along with the increase of fibroblast-derived stem cell growth factor gremlin 1 mRNA (GREM1). However, UC deconvolution data showed rapid induction of inflammatory fibroblasts and upregulation of major structural ECM collagen mRNAs along with tissue inhibitor of metalloproteinase 1 (TIMP1), suggesting increased profibrotic ECM deposition. No change was seen in transforming growth factor β (TGFβ) mRNA, whereas the profibrotic cytokines interleukin 13 (IL13) and IL11 were upregulated in UC, suggesting that human postinjury responses could be TGFβ-independent. In conclusion, we found distinct regulatory layers of regeneration in the normal human colon and a potential targetable profibrotic dysregulation in UC that could lead to long-term end-organ failure, i.e., intestinal damage. NEW & NOTEWORTHY: The study reveals the regulatory dynamics of epithelial regeneration and extracellular matrix remodeling after experimental injury of the human colon in vivo and shows that human intestinal regeneration is different from data obtained from animals. A lag phase in epithelial restitution is associated with induction of stromal cell-derived epithelial growth factors. Postinjury regeneration is transforming growth factor β-independent, and we find a profibrotic response in patients with ulcerative colitis despite being in remission. [ABSTRACT FROM AUTHOR]

The study investigated whether patients with atopic dermatitis (AD) have an altered response to contact allergens compared to those without AD. The researchers compared the response to a contact allergen in mice with different skin conditions. They found that mice with impaired skin barrier and pre-existing skin inflammation had a reduced inflammatory response to the allergen compared to mice with healthy skin or impaired skin barrier without inflammation. The study suggests that pre-existing skin inflammation can suppress immune responses to new allergens, which may have implications for future research in contact allergy and dermal vaccine development. [Extracted from the article]

Background: Allergic contact dermatitis (ACD) is an inflammatory disease with a complex pathophysiology in which epidermal‐resident memory CD8+ T (TRM) cells play a key role. The mechanisms involved in the activation of CD8+ TRM cells during allergic flare‐up responses are not understood. Methods: The expression of CD100 and its ligand Plexin B2 on CD8+ TRM cells and keratinocytes before and after allergen exposure was determined by flow cytometry and RT‐qPCR. The role of CD100 in the inflammatory response during the challenge phase of ACD was determined in a model of ACD in CD100 knockout and wild‐type mice. Results: We show that CD8+ TRM cells express CD100 during homeostatic conditions and up‐regulate it following re‐exposure of allergen‐experienced skin to the experimental contact allergen 1‐fluoro‐2,4‐dinitrobenzene (DNFB). Furthermore, Plexin B2 is up‐regulated on keratinocytes following exposure to some contact allergens. We show that loss of CD100 results in a reduced inflammatory response to DNFB with impaired production of IFNγ, IL‐17A, CXCL1, CXCL2, CXCL5, and IL‐1β and decreased recruitment of neutrophils to the epidermis. Conclusion: Our study demonstrates that CD100 is expressed on CD8+ TRM cells and is required for full activation of CD8+ TRM cells and the flare‐up response of ACD. [ABSTRACT FROM AUTHOR]

A study published in the journal Clinical & Experimental Allergy found that a positive basophil histamine release assay (BHRA) can help identify patients with type IIb chronic spontaneous urticaria (CSU) who are less likely to respond to standard-dosed omalizumab treatment. CSU patients with type IIb autoimmunity have a higher disease severity and are more refractory to antihistamines and omalizumab. The study also found that BHRA positivity occurs in approximately one out of seven CSU patients and may be used as a predictor of a poorer response to omalizumab, indicating the need for off-label use in these patients. [Extracted from the article]

Background: The junctional adhesion molecule‐like protein (JAML) plays important roles in wound healing and activation of epidermal γδ T cells in mice. Whether JAML plays a role in contact hypersensitivity (CHS), the animal model of allergic contact dermatitis (ACD), is not known. Methods: To examine the role of JAML in CHS, we used various mouse models of CHS in JAML knockout (KO) and wild‐type (WT) mice. Furthermore, the expression of the JAML ligand coxsackievirus and adenovirus receptor (CXADR) on keratinocytes was accessed in vitro and in vivo. Results: JAML KO mice had a diminished inflammatory response during both the sensitization and elicitation phase of CHS and had reduced numbers of CD8+ and CD4+ T cells in the epidermis. Furthermore, interferon γ (IFNγ), interleukin 1β (IL‐1β) and CXCL10 production were significantly reduced in JAML KO mice during the elicitation phase. We found that CD8+ T cells express JAML and that JAML is essential for rapid flare‐up responses to contact allergens. Finally, we show that keratinocytes up‐regulate the JAML ligand CXADR following exposure to contact allergens. Conclusion: Our study is the first to show a central role of JAML in CHS and reveals a potential new target for the treatment of ACD in humans. [ABSTRACT FROM AUTHOR]

A response by Thorbjørn Krejsgaard and colleagues to a letter to the editor on their article "Malignant cutaneous T-cell lymphoma cells express IL-17 utilizing the Jak3/Stat3 signaling pathway" in the 2011 issue is presented.

Background: CD8+ epidermal‐resident memory T (TRM) cells play central roles in local flare‐up responses to experimental contact allergens by inducing massive influx of neutrophils to the epidermis upon allergen challenge. Whether similar immunopathogenic mechanisms are involved in the responses to clinically relevant contact allergens is unknown. Methods: The immune response to cinnamal, ρ‐phenylenediamine (PPD) and methylisothiazolinone (MI) was studied in a well‐established mouse model for allergic contact dermatitis that includes formation of TRM cells by ELISA, flow cytometry, fluorescence microscopy analyses and cell depletion protocols. Results: We show that the formation of CD4+ and CD8+ epidermal TRM cells and the inflammatory response are highly allergen‐dependent. However, the magnitude of the flare‐up responses correlated with the number of epidermal CD8+ TRM cells, CXCL1/CXCL2 release and recruitment of neutrophils to the epidermis. Finally, depletion of CD4+ T cells strongly enhanced the number of epidermal CD8+ TRM cells, the flare‐up response and the epidermal infiltration of neutrophils for all allergens. Conclusion: As the first, this study demonstrates that clinically relevant contact allergens have the ability to generate pathogenic, epidermal CD8+ TRM cells that recruit neutrophils following re‐exposure to the allergen, but that this normally is counteracted by the simultaneous induction of anti‐inflammatory CD4+ T cells. [ABSTRACT FROM AUTHOR]

Sézary syndrome (SS) is a rare and aggressive type of cutaneous T-cell lymphoma, with an abnormal inflammatory response in affected skin. The cytokines IL-1B and IL-18, as key signaling molecules in the immune system, are produced in an inactive form and cleave to the active form by inflammasomes. In this study, we assessed the skin, serum, peripheral mononuclear blood cell (PBMC) and lymph-node samples of SS patients and control groups (healthy donors (HDs) and idiopathic erythroderma (IE) nodes) to investigate the inflammatory markers IL-1B and IL-18 at the protein and transcript expression levels, as potential markers of inflammasome activation. Our findings showed increased IL-1B and decreased IL-18 protein expression in the epidermis of SS patients; however, in the dermis layer, we detected increased IL-18 protein expression. In the lymph nodes of SS patients at advanced stages of the disease (N2/N3), we also detected an enhancement of IL-18 and a downregulation of IL-1B at the protein level. Moreover, the transcriptomic analysis of the SS and IE nodes confirmed the decreased expression of IL1B and NLRP3, whereas the pathway analysis indicated a further downregulation of IL1B-associated genes. Overall, the present findings showed compartmentalized expressions of IL-1B and IL-18 and provided the first evidence of their imbalance in patients with Sézary syndrome. [ABSTRACT FROM AUTHOR]

The glucagon-like peptide-1 receptor (GLP-1R) plays a key role in metabolism and is an important therapeutic target in diabetes and obesity. Recent studies in experimental animals have shown that certain subsets of T cells express functional GLP-1R, indicating an immune regulatory role of GLP-1. In contrast, less is known about the expression and function of the GLP-1R in human T cells. Here, we provide evidence that activated human T cells express GLP-1R. The expressed GLP-1R was functional, as stimulation with a GLP-1R agonist triggered an increase in intracellular cAMP, which was abrogated by a GLP-1R antagonist. Analysis of CD4+ T cells activated under T helper (Th) 1, Th2, Th17 and regulatory T (Treg) cell differentiation conditions indicated that GLP-1R expression was most pronounced in induced Treg (iTreg) cells. Through multimodal single-cell CITE- and TCR-sequencing, we detected GLP-1R expression in 29–34% of the FoxP3+CD25+CD127- iTreg cells. GLP-1R+ cells showed no difference in their TCR-gene usage nor CDR3 lengths. Finally, we demonstrated the presence of GLP-1R+CD4+ T cells in skin from patients with allergic contact dermatitis. Taken together, the present data demonstrate that T cell activation triggers the expression of functional GLP-1R in human CD4+ T cells. Given the high induction of GLP-1R in human iTreg cells, we hypothesize that GLP-1R+ iTreg cells play a key role in the anti-inflammatory effects ascribed to GLP-1R agonists in humans. [ABSTRACT FROM AUTHOR]

During the 12-week treatment period, a total of five patients (21.7%) reported at least one suspected side effect of omalizumab; headache (2 patients), fatigue (2 patients), weight gain (2 patients) and dry mouth (2 patients). Keywords: body mass index; chronic urticaria; IgE; omalizumab; pharmacokinetics EN body mass index chronic urticaria IgE omalizumab pharmacokinetics 715 718 4 04/29/22 20220501 NES 220501 Key Messages Omalizumab (anti-IgE) is effective and safe for treating antihistaminerefractory chronic spontaneous urticaria. Omalizumab serum levels predict treatment outcomes in patients with chronic spontaneous urticaria: A three-month prospective study. [Extracted from the article]

Background: Allergic contact dermatitis (ACD) is classically described as a delayed‐type hypersensitivity reaction. However, patients often experience flare‐ups characterized by itching erythema, edema, and often vesicles occurring within hours after re‐exposure of previously sensitized skin to the specific contact allergen. Recent studies have indicated that skin‐resident memory T (TRM) cells play a central role in ACD. However, the pathogenic role of TRM cells in allergen‐induced flare‐ups is not known. Methods: By the use of various mouse models and cell depletion protocols, we investigated the role of epidermal TRM cells in flare‐up reactions to the experimental contact allergen 1‐fluoro‐2,4‐dinitrobenzene. The inflammatory response was measured by changes in ear thickness, and the cellular composition in epidermis was determined by flow cytometry and confocal microscopy. Finally, adaptive transfer and inhibitors were used to determine the role of TRM cells, neutrophils, and CXCL1/CXCL2 in the response. Results: We show that CD8+ TRM cells initiate massive infiltration of neutrophils in the epidermis within 12 h after re‐exposure to the contact allergen. Depletion of neutrophils before re‐exposure to the allergen abrogated the flare‐up reactions. Furthermore, we demonstrate that CD8+ TRM cells mediate neutrophil recruitment by inducing CXCL1 and CXCL2 production in the skin, and that blockage of the C‐X‐C chemokine receptor type 1 and 2 inhibits flare‐up reactions and neutrophil infiltration. Conclusion: As the first, we show that epidermal CD8+ TRM cells cause ACD flare‐ups by rapid recruitment of neutrophils to the epidermis. [ABSTRACT FROM AUTHOR]

Ryder LR, Bartels EM, Woetmann A, Madsen HO, Ødum N, Bliddal H, Danneskiold-Samsøe B, Ribel-Madsen S, Ryder LP. FoxP3 mRNA splice forms in synovial CD4+ T cells in rheumatoid arthritis and psoriatic arthritis. APMIS 2012; 120: 387-96. Our aim was to elucidate the relative amount of the different splice forms of FoxP3 mRNA in CD4+ T cells in peripheral blood (PB) compared to synovial fluid (SF) in RA and PsA patients. FoxP3 mRNA was measured using a quantitative real-time PCR method. CD4+ T cells were isolated from 17 paired samples of PB and SF from RA and PsA patients, and PB from 10 controls. FoxP3fl and FoxP3Δ2 mRNA was significantly increased (6.7 and 2.1-fold, respectively) in PB CD4+ T cells from RA patients compared to controls. FoxP3fl and Δ2 mRNA in SF CD4+ T cells was increased compared to controls in sero-negative RA and PsA, but not in sero-positive RA patients, who had a high FoxP3 expression in both PB and SF. The FoxP3Δ2Δ7 mRNA was barely detectable in patient samples, and not at all in healthy individuals. We provide evidence of an increased expression of FoxP3 splice forms in synovial CD4+ T cells from RA patients. A skewed, high expression profile of FoxP3, but not CTLA-4, in sero-negative RA and PsA, indicates that synovial CD4+ T cells may represent unique subsets of T cells which have been induced locally or selectively recruited to the joint. [ABSTRACT FROM AUTHOR]

Abstract: For decades cytokines such as type I interferons and IL-2 have been used in immunotherapy against cancer, viral hepatitis, and autoimmune diseases such as multiple sclerosis. However, the therapeutic use of cytokines has been hampered by their pleiotropic effects on target-cells. Thus, cytokines such as IFN-α and IL-2 have multiple and severe side effects. Accordingly, they are generally used at sub-optimal doses, which limit their clinical efficacy. Here we hypothesized that a combination of IFN-α and IL-21, a novel cytokine of the IL-2 family with anti-cancer effects, will increase the anti-cancer efficacy at sub-optimal cytokine doses. We show that the combined stimulation of target-cells with IFN-α and IL-21 triggers an increased STAT3 activation whereas the activation of other STATs including STAT1/2 is unaffected. In parallel, the combined stimulation with IFN-α and IL-21 triggers a selective increase in MHC class I expression and NK- and CD8+ T-cell-mediated cytotoxicity. In an experimental in vivo model of renal carcinoma, the combined treatment of IFN-α and IL-21 also produces a significant anti-cancer effect as judged by an inhibition of tumor growth and an increased survival. Taken together our data show that the combined use of IFN-α and IL-21 boosts STAT3 signaling, cytotoxicity, and anti-tumor efficacy, suggesting that a combinatorial therapeutic use of these cytokines may benefit cancer patients. [Copyright &y& Elsevier]

Interferon (IFN)-α/β is produced by virally infected ceils and is believed to play an important role in early phases of the innate immune response. In addition, IFNα/β inhibits interleukin (IL)-4 signaling in B cells and monocytes, suggesting that IFN-α/β (like IFN-γ) is a Th1 cytokine. Here, we study cross-talk between IFN-α and IL-4 in human T cells. As expected, stimulation with IFN-α for 12-24 h inhibits IL-4 signaling. Surprisingly, however, IFN-α has the opposite effect on IL-4 signaling at earlier time points (up to 6 h). Thus, IFN-α enhances IL-4-mediated STAT6 activation in both CD4+ and CD8+ human T cells. The effect is specific because (i) another interferon, IFN-γ, does not enhance IL-4-mediated STAT6 activation, (ii) IFN-α-mediated STAT1 and STAT2 activation is not modulated by IL-4, and (iii) activation of Janus kinases is not enhanced or prolonged by simultaneous stimulation with IFN-α and IL-4. Moreover, costimulation results in a selective increased STAT6/ STAT2 association and an association between IFNAR/ IL-4R components, suggesting that the IFNAR provides an additional STAT6 docking site via STAT2, leading to a more efficient dimerization/activation of STAT6 only. The co-stimulatory effect on STAT6 activation correlates with a cooperative increase in nuclear translocation, DNA binding, transcriptional activity, and mRNA expression of STAT6 target genes (IL-4Rα and IL-15Rα). In conclusion, we provide evidence that IFN-α both upand down-regulates IL-4-mediated STAT6 signaling and thereby regulates the sensitivity to IL-4 in human T lymphocytes. Thus, our findings suggest that IFN-α has a complex regulatory role in adaptive immunity, which is different from the "classical" Th1 profile of IFN-γ. [ABSTRACT FROM AUTHOR]

Staphylococcus aureus (SA) causes superficial and severe endovascular infections. The present in vitro study investigates the anti‐SA mechanisms of hyperbaric oxygen therapy (HBOT) on direct bacterial killing, antibiotic potentiation, and polymorphonuclear leukocyte (PMN) enhancement. SA was exposed to isolated human PMNs, tobramycin, ciprofloxacin, or benzylpenicillin. HBOT was used as one 90‐min session. Bacterial survival was evaluated after 4 h by quantitative bacteriology. PMN functionality as reactive oxygen species (ROS) production was measured by means of dihydrorhodamine 123 analysis. We showed that HBOT exhibits significant direct anti‐SA effects. HBOT increased the anti‐SA effects of PMNs by 18% after PMA stimulation (p = 0.0004) and by 15% in response to SA (p = 0.36). HBOT showed an additive effect as growth reductions of 26% to sub‐MICs of tobramycin (p = 0.0057), 44% to sub‐MICs of ciprofloxacin (p = 0.0001), and 26% to sub‐MICs of penicillin (p = 0.038). The present in vitro study provides evidence that HBOT has differential mechanisms mediating its anti‐SA effects. Our observation supports the clinical possibility for adjunctive HBOT to augment the host immune response and optimize the efficacy of antibiotic treatments. [ABSTRACT FROM AUTHOR]

Background: Several cancers, including mycosis fungoides (MF), have reported dysregulation of miR‐195‐5p. miR‐195‐5p plays a role in cell cycle regulation in several malignant diseases. Objectives: This study aimed to investigate: (a) the expression level of miR‐195‐5p in lesional MF skin biopsies and (b) the potential regulatory roles of miR‐195‐5p in MF. Methods: Quantitative real‐time polymerase chain reaction (RT‐qPCR) was used to determine miR‐195‐5p expression in MF skin biopsies and cell lines. The effect of miR‐195‐5p and ADP‐ribosylation factor‐like protein 2 (ARL2) on cell cycle and apoptosis was measured by flow cytometry assays. Changes in ARL2 expression were determined by RT‐qPCR and Western blotting (WB). Results: We found lower expression levels of miR‐195‐5p in lesional skin from MF patients compared with non‐lesional MF skin and skin from healthy volunteers. Additionally, miR‐195‐5p showed lower expression levels in the skin from patients with disease progression compared with patients with stable disease. In vitro studies showed that overexpression of miR‐195‐5p induced a cell cycle arrest in G0G1. Using microarray analysis, we identified several genes that were regulated after miR‐195‐5p overexpression. The most downregulated gene after miR‐195‐5p mimic transfection was ARL2. RT‐qPCR and WB analyses confirmed downregulation of ARL2 following transfection with miR‐195‐5p mimic. Lastly, transfection with siRNA against ARL2 also induced a G0G1 arrest. Conclusion: Upregulation of miR‐195‐5p in MF inhibits cycle arrest by downregulation of ARL2. miR‐195‐5p may thus function as a tumor suppressor in MF and low miR‐195‐5p expression in lesional MF skin may promote disease progression. [ABSTRACT FROM AUTHOR]

Background: Epidermal T cells play a central role in immune surveillance and in inflammatory skin diseases. Major differences in the epidermal T cell composition are found between adult humans and antigen‐inexperienced laboratory mice. Whether this is due to inborn species differences, to different environmental exposures, or a combination of the two is a matter of debate. Objectives: To investigate the role of age and exposure to antigens on epidermal T cell subsets in human and mouse skin. Methods: We isolated T cells from the epidermis from 19 infants and 26 adults, and determined the frequency of CD4+ and CD8+ αβ T cells and γδ T cells by flow cytometry. In addition, we determined the epidermal T cell composition in antigen‐inexperienced and antigen‐experienced mice. Results: We found that humans are born with very few epidermal T cells. The number increases and the composition changes with age. In antigen‐inexperienced mice, the epidermal T cell composition is unaffected by age, but it is dramatically affected by antigen exposure. Conclusion: Taken together, we show that antigen exposure, as opposed to age, is the major factor determining the composition of epidermal T cells, suggesting that the skin of antigen‐experienced mice better reflects the immunological conditions in human skin. [ABSTRACT FROM AUTHOR]

T cell activation is intimately linked to metabolism, as distinct metabolic requirements support the functional and phenotypical differences between quiescent and activated T cells. Metabolic transition from mitochondrial oxidative phosphorylation to aerobic glycolysis is crucial for a proper T cell activation. However, the role of tricarboxylic acid cycle (TCA), and in particular succinate dehydrogenase (SDH) in activated T cells needs further elucidation. Here we show that inhibition of SDH during activation of T cells results in strong impairment of proliferation, expression of activation markers, and production of key inflammatory cytokines, despite a concomitant increase in glycolytic metabolic activity. Similar effect of SDH inhibition were demonstrated in pre-activated T cell. Interestingly, itaconic acid, an endogenous SDH inhibitor released from activated macrophages and dendritic cells, had no immunomodulator effect. Taken together, our findings demonstrate that SDH enzyme fitness is critical for mounting and maintaining appropriate activation and function of human T cells. [ABSTRACT FROM AUTHOR]

and its toxins have been linked to disease progression and mortality in advanced stages of cutaneous T-cell lymphoma (CTCL). CD8+ T cells play a crucial role in anti-cancer responses and high CD8+ T cell numbers in tumor lesions are associated with a favorable prognosis in CTCL. Here, we show that CD8+ T cells from both healthy donors and Sézary syndrome patients are highly susceptible to cell death induced by Staphylococcal alpha-toxin, whereas malignant T cells are not. Importantly, alpha-toxin almost completely blocks cytotoxic killing of CTCL tumor cells by peptide-specific CD8+ T cells, leading to their escape from induced cell death and continued proliferation. These findings suggest that alpha-toxin may favor the persistence of malignant CTCL cells in vivo by inhibiting CD8+ T cell cytotoxicity. Thus, we propose a novel mechanism by which colonization with Staphylococcus aureus may contribute to cancer immune evasion and disease progression in CTCL. [ABSTRACT FROM AUTHOR]

Microdialysis is a well-established technique for sampling of small molecules from the human skin, but larger molecules are more difficult to recover. Consequently, sampling feasibility must be evaluated before microdialysis is used in vivo. This report presents a tool for estimating the recovery of large biomarkers from human skin by microdialysis, using previously frozen human skin specimens as reservoirs for biomarker reference solutions. Recovery of the following 17 biomarkers was assessed: CCL27/CTACK, CXCL1/GROa, CXCL7/NAP-2, CXCL10/IP-10, EGF, GM-CSF, IFN-α, IL-1a, IL-6, IL-8, IL-17, IL-22, IL-23, MIF, TNF-a, TSLP and VEGF. The relative skin recoveries of 13/17 biomarkers were successfully determined in the range 4.0- 18.4%. Sampling in the skin reservoir model was not associated with probe leakage, as fluid recovery was stable, at between 80% and 110%. Furthermore, the skin reservoir model enabled studies and optimization of different parameters known to affect biomarker recovery, including flow rate and perfusate composition. [ABSTRACT FROM AUTHOR]

Staphylococcus aureus is implicated in disease progression in cutaneous T-cell lymphoma (CTCL). Here, we demonstrate that malignant T cell lines derived from CTCL patients as well as primary malignant CD4+ T cells from Sézary syndrome patients are considerably more resistant to alpha-toxin-induced cell death than their non-malignant counterparts. Thus, in a subset of Sézary syndrome patients the ratio between malignant and non-malignant CD4+ T cells increases significantly following exposure to alpha-toxin. Whereas toxin-induced cell death is ADAM10 dependent in healthy CD4+ T cells, resistance to alpha-toxin in malignant T cells involves both downregulation of ADAM10 as well as other resistance mechanisms. In conclusion, we provide first evidence that Staphylococcus aureus derived alpha-toxin can tilt the balance between malignant and non-malignant CD4+ T cells in CTCL patients. Consequently, alpha-toxin may promote disease progression through positive selection of malignant CD4+ T cells, identifying alpha-toxin as a putative drug target in CTCL. [ABSTRACT FROM AUTHOR]

Mycosis fungoides (MF) is the most frequent form of cutaneous T-cell lymphoma. The disease often takes an indolent course, but in approximately one-third of the patients, the disease progresses to an aggressive malignancy with a poor prognosis. At the time of diagnosis, it is impossible to predict which patients develop severe disease and are in need of aggressive treatment. Accordingly, we investigated the prognostic potential of microRNAs (miRNAs) at the time of diagnosis in MF. Using a quantitative reverse transcription polymerase chain reaction platform, we analyzed miRNA expression in diagnostic skin biopsies from 154 Danish patients with early-stage MF. The patients were subdivided into a discovery cohort (n = 82) and an independent validation cohort (n = 72). The miRNA classifier was built using a LASSO (least absolute shrinkage and selection operator) Cox regression to predict progression-free survival (PFS). We developed a 3-miRNA classifier, based on miR-106b-5p, miR-148a-3p, and miR-338-3p, which successfully separated patients into high-risk and low-risk groups of disease progression. PFS was significantly different between these groups in both the discovery cohort and the validation cohort. The classifier was stronger than existing clinical prognostic factors and remained a strong independent prognostic tool after stratification and adjustment for these factors. Importantly, patients in the high-risk group had a significantly reduced overall survival. The 3-miRNA classifier is an effective tool to predict disease progression of early-stage MF at the time of diagnosis. The classifier adds significant prognostic value to existing clinical prognostic factors and may facilitate more individualized treatment of these patients. [ABSTRACT FROM AUTHOR]

Spondyloarthritis (SpA) is characterized by inflammation and new bone formation and can be treated by inhibition of the proinflammatory cytokines TNF-α and IL-17A. IL-26 is considered a proinflammatory cytokine, predominantly related to Th17 cells. In the present study, we investigate IL-26 expression in SpA patients, and examine the in vitro production of IL-26 by synovial cells and the effects of IL-26 on human osteoblasts. IL-26 was measured by ELISA in plasma and synovial fluid (SF) of 15 SpA patients and in plasma samples from 12 healthy controls. Facet joints from axial SpA patients were stained for IL-26 and analyzed by fluorescence microscopy. Synovial fluid mononuclear cells, C-C motif chemokine receptor 6 memory Th17 cells, and fibroblast-like synoviocytes (FLSs) were isolated, and supernatants were analyzed for IL-26 content by ELISA. FLSs were further stained for IL-26 production and the myofibroblast marker α-smooth-muscle-actin (αSMA) and analyzed by flow cytometry. Human osteoblasts were cultured in the presence of IL-26, and the degree of mineralization was quantified. We found that IL-26 levels in SF were increased compared with plasma ( P < 0.0001). Moreover, IL-26 expression was found in facet joints of axial SpA patients within the bone marrow. IL-26 secretion was primarily found in αSMA myofibroblasts. In contrast, Th17 cells did not produce detectable amounts of IL-26. Human osteoblasts treated with IL-26 showed increased mineralization compared with untreated osteoblasts ( P = 0.02). In conclusion, IL-26 seems to be produced by myofibroblasts in the inflamed synovium and could be a possible facilitator of bone mineralization in SpA. Key messages: [ABSTRACT FROM AUTHOR]

Cutaneous T-cell lymphomas (CTCL) are characterized by the presence of chronically inflamed skin lesions containing malignant T cells. Early disease presents as limited skin patches or plaques and exhibits an indolent behavior. For many patients, the disease never progresses beyond this stage, but in approximately one third of patients, the disease becomes progressive, and the skin lesions start to expand and evolve. Eventually, overt tumors develop and the malignant T cells may disseminate to the blood, lymph nodes, bone marrow, and visceral organs, often with a fatal outcome. The transition from early indolent to progressive and advanced disease is accompanied by a significant shift in the nature of the tumor-associated inflammation. This shift does not appear to be an epiphenomenon but rather a critical step in disease progression. Emerging evidence supports that the malignant T cells take control of the inflammatory environment, suppressing cellular immunity and anti-tumor responses while promoting a chronic inflammatory milieu that fuels their own expansion. Here, we review the inflammatory changes associated with disease progression in CTCL and point to their wider relevance in other cancer contexts. We further define the term 'malignant inflammation' as a pro-tumorigenic inflammatory environment orchestrated by the tumor cells and discuss some of the mechanisms driving the development of malignant inflammation in CTCL. [ABSTRACT FROM AUTHOR]

Background Skin-resident memory T (TRM) cells are associated with immunological memory in the skin. Whether immunological memory responses to allergens in the skin are solely localized to previously allergen-exposed sites or are present globally in the skin is not clear. Furthermore, the mechanisms whereby TRM cells induce rapid recall responses need further investigation. Objectives To study whether contact allergens induce local and/or global memory, and to determine the mechanisms involved in memory responses in the skin. Methods To address these questions, we analysed responses to contact allergens in mice and humans sensitized to 2,4-dinitrofluorobenzene and nickel, respectively. Results Challenge responses in both mice and humans were dramatically increased at sites previously exposed to allergens as compared with previously unexposed sites. Importantly, the magnitude of the challenge response correlated with the epidermal accumulation of interleukin (IL)-17A-producing and interferon (IFN)-γ-producing TRM cells. Moreover, IL-17A and IFN-γ enhanced allergen-induced IL-1β production in keratinocytes. Conclusions We show that sensitization with contact allergens induces a strong, long-lasting local memory and a weaker, temporary global immunological memory response to the allergen that is mediated by IL-17A-producing and IFN-γ-producing CD8+ TRM cells. [ABSTRACT FROM AUTHOR]

Cutaneous T cell lymphoma (CTCL) is characterized by proliferation of malignant T cells in a chronic inflammatory environment. With disease progression, bacteria colonize the compromised skin barrier and half of CTCL patients die from infection rather than from direct organ involvement by the malignancy. Clinical data indicate that bacteria play a direct role in disease progression, but little is known about the mechanisms involved. Here, we demonstrate that bacterial isolates containing staphylococcal enterotoxin-A (SEA) from the affected skin of CTCL patients, as well as recombinant SEA, stimulate activation of STAT3 and up-regulation of IL-17 in immortalized and primary patient-derived malignant and non-malignant T cells. Importantly, SEA induces STAT3 activation and IL-17 expression in malignant T cells when co-cultured with non-malignant T cells indicating an indirect mode of action. In accordance, malignant T cells expressing a SEA non-responsive T cell receptor variable β chain (TCR-Vb) are non-responsive to SEA in mono-culture, but display strong STAT3 activation and IL-17 expression in co-cultures with SEA-responsive, non-malignant T cells. The response is induced via IL-2 receptor common γ chain cytokines and a Janus kinase 3 (JAK3) - dependent pathway in malignant T cells and blocked by Tofacitinib, a clinical-grade JAK3 inhibitor. In conclusion, we demonstrate that SEA induces cell cross-talk-dependent activation of STAT3 and expression of IL-17 in malignant T cells suggesting a mechanism where SEA-producing bacteria promote activation of an established oncogenic pathway previously implicated in carcinogenesis. [ABSTRACT FROM AUTHOR]

We have recently shown that the E3 ubiquitin ligase midline 1 ( MID1) is upregulated in murine cytotoxic lymphocytes ( CTL), where it controls exocytosis of lytic granules and the killing capacity. Accordingly, CTL from MID1 knock-out ( MID1−/−) mice have a 25-30% reduction in exocytosis of lytic granules and cytotoxicity compared to CTL from wild-type ( WT) mice. We wondered why the MID1 gene knock-out did not affect exocytosis and cytotoxicity more severely and speculated whether MID2, a close homologue of MID1, might partially compensate for the loss of MID1 in MID1−/− CTL. Here, we showed that MID2, like MID1, is upregulated in activated murine T cells. Furthermore, MID1−/− CTL upregulated MID2 two-twenty-fold stronger than CTL from WT mice, suggesting that MID2 might compensate for MID1. In agreement, transfection of MID2 into MID1−/− CTL completely rescued exocytosis of lytic granules in MID1−/− CTL, and vice versa, knock-down of MID2 inhibited exocytosis of lytic granules in both WT and MID1−/− CTL, demonstrating that both MID1 and MID2 play a central role in the regulation of granule exocytosis and that functional redundancy exists between MID1 and MID2 in CTL. [ABSTRACT FROM AUTHOR]

The interaction between keratinocytes (KCs) and skin-resident immune cells has an important role in induction of contact hypersensitivity. A specific subset of γδ T cells termed dendritic epidermal T cells (DETCs) are located in mouse epidermis, and we have recently shown that DETCs become activated and produce IL-17 in an IL-1β-dependent manner during contact hypersensitivity. Various receptors on DETCs, including NKG2D, are involved in DETC responses against tumors and during wound healing. The ligands for NKG2D (NKG2DL) are stress-induced proteins such as mouse UL16-binding protein-like transcript 1 (Mult-1), histocompatibility 60 (H60), and retinoic acid early inducible-1 (Rae-1) in mice and major histocompatibility complex (MHC) class I-chain-related A (MICA), MHC class I-chain-related B, and UL16-binding protein in humans. Here, we show that allergens upregulate expression of the NKG2DL Mult-1, H60, and Rae-1 in cultured mouse KCs and of MICA in primary human KCs. We demonstrate that Mult-1 is expressed in mouse skin exposed to allergen. Furthermore, we find that the vast majority of DETCs in murine epidermis and skin-homing cutaneous lymphocyte-associated antigen positive γδ T cells in humans express NKG2D. Finally, we demonstrate that blocking of NKG2D partially inhibits allergen-induced DETC activation. These findings demonstrate that NKG2D and NKG2DL are involved in allergen-induced activation of DETCs and indicate that the NKG2D/NKG2DL pathway might be a potential target for treatment of contact hypersensitivity. [ABSTRACT FROM AUTHOR]

Midline 1 (MID1) is a microtubule-associated ubiquitin ligase that regulates protein phosphatase 2 A levels. Loss-of-function mutations in MID1 lead to the human X-linked Opitz G/BBB (OS) syndrome characterized by defective midline development during embryogenesis. We have recently shown that MID1 is strongly up-regulated in murine cytotoxic T lymphocytes (CTLs), and that it has a significant impact on exocytosis of lytic granules and the killing capacity of CTLs. The aims of the present study were to determine the localization of MID1 in migrating CTLs, and to investigate whether MID1 affects CTL polarization and migration. We found that MID1 mainly localizes to the uropod of migrating CTLs and that it has a substantial impact on CTL polarization and migration in vitro. Furthermore, analysis of contact hypersensitivity responses supported that MID1 controls effector functions of CTLs in hapten-challenged skin in vivo. These results provide significant new knowledge on the role of MID1 in CTL biology. [ABSTRACT FROM AUTHOR]

Background Several attempts to establish a model in mice that reflects nickel allergy in humans have been made. Most models use intradermal injection of nickel in combination with adjuvant to induce nickel allergy. However, such models poorly reflect induction of nickel allergy following long-lasting epicutaneous exposure to nickel. Objective To develop a mouse model reflecting nickel allergy in humans induced by epicutaneous exposure to nickel, and to investigate the mechanisms involved in such allergic responses. Methods Mice were exposed to NiCl2 on the dorsal side of the ears. Inflammation was evaluated by the swelling and cell infiltration of the ears. T cell responses were determined as numbers of CD4+ and CD8+ T cells in the draining lymph nodes. Localization of nickel was examined by dimethylglyoxime staining. Results Epicutaneous exposure to nickel results in prolonged localization of nickel in the epidermis, and induces nickel allergy in mice. The allergic response to nickel following epicutaneous exposure is MyD88-dependent and interleukin ( IL)-1 receptor-dependent, but independent of toll-like receptor ( TLR)-4. Conclusion This new model for nickel allergy that reflects epicutaneous exposure to nickel in humans shows that nickel allergy is dependent on MyD88 and IL-1 receptor signalling, but independent of TLR4. [ABSTRACT FROM AUTHOR]

Background In vitro studies have shown that the active form of vitamin D3, 1α,25-dihydroxyvitamin D3 (1,25(OH)2D3), can regulate differentiation of CD4+ T cells by inhibiting Th1 and Th17 cell differentiation and promoting Th2 and Treg cell differentiation. However, the serum concentration of 1,25(OH)2D3 is far below the effective concentration of 1,25(OH)2D3 found in in vitro studies, and it has been suggested that 1,25(OH)2D3 must be produced locally from the inactive precursor 25-hydroxyvitamin D3 (25(OH)D3) to affect ongoing immune responses in vivo. Although it has been reported that activated T cells express the 25(OH)D- 1α-hydroxylase CYP27B1 that converts 25(OH)D3 to 1,25(OH)2D3, it is still controversial whether activated T cells have the capacity to produce sufficient amounts of 1,25(OH)2D3 to affect vitamin D-responsive genes. Furthermore, it is not known how the vitamin D-binding protein (DBP) found in high concentrations in serum affects T cell responses to 25(OH)D3. Results We found that activated T cells express CYP27B1 and have the capacity to produce sufficient 1,25(OH)2D3 to affect vitamin D-responsive genes when cultured with physiological concentrations of 25(OH)D3 in serum-free medium. However, if the medium was supplemented with serum or purified DBP, DBP strictly inhibited the production of 1,25(OH)2D3 and 25(OH)D3-induced T cell responses. In contrast, DBP did not inhibit the effect of exogenous 1,25(OH)2D3. Actin, arachidonic acid and albumin did not affect the sequestration of 25(OH)D3 by DBP, whereas carbonylation of DBP did. Conclusions Activated T cells express CYP27B1 and can convert 25(OH)D3 to 1,25(OH)2D3 in sufficiently high concentrations to affect vitamin D-responsive genes when cultured in serum-free medium. However, DBP sequesters 25(OH)D3 and inhibits the production of 1,25(OH)2D3 in T cells. To fully exploit the immune-regulatory potential of vitamin D, future studies of the mechanisms that enable the immune system to exploit 25(OH)D3 and convert it to 1,25(OH)2D3 in vivo are required. [ABSTRACT FROM AUTHOR]

Patients with cutaneous T-cell lymphoma (CTCL) are frequently colonized with Staphylococcus aureus (SA). Eradication of SA is, importantly, associated with significant clinical improvement, suggesting that SA promotes the disease activity, but the underlying mechanisms remain poorly characterized. Here, we show that SA isolates from involved skin express staphylococcal enterotoxins (SEs) that induce crosstalk between malignant and benign T cells leading to Stat3-mediated interleukin-10 (IL-10) production by the malignant T cells. The SEs did not stimulate the malignant T cells directly. Instead, SEs triggered a cascade of events involving cell-cell and asymmetric cytokine interactions between malignant and benign T cells, which stimulated the malignant T cells to express high levels of IL-10. Much evidence supports that malignant activation of the Stat3/IL-10 axis plays a key role in driving the immune dysregulation and severe immunodeficiency that characteristically develops in CTCL patients. The present findings thereby establish a novel link between SEs and immune dysregulation in CTCL, strengthening the rationale for antibiotic treatment of colonized patients with severe or progressive disease. [ABSTRACT FROM AUTHOR]

The active form of vitamin D3, 1,25(OH)2D3, has significant immunomodulatory properties and is an important determinant in the differentiation of CD4+ effector T cells. The biological actions of 1,25(OH)2D3 are mediated by the vitamin D receptor (VDR) and are believed to correlate with the VDR protein expression level in a given cell. The aim of this study was to determine if and how 1,25(OH)2D3 by itself regulates VDR expression in human CD4+ T cells. We found that activated CD4+ T cells have the capacity to convert the inactive 25(OH)D3 to the active 1,25(OH)2D3 that subsequently up-regulates VDR protein expression approximately 2-fold. 1,25(OH)2D3 does not increase VDR mRNA expression but increases the half-life of the VDR protein in activated CD4+ T cells. Furthermore, 1,25(OH)2D3 induces a significant intracellular redistribution of the VDR. We show that 1,25(OH)2D3 stabilizes the VDR by protecting it from proteasomal degradation. Finally, we demonstrate that proteasome inhibition leads to up-regulation of VDR protein expression and increases 1,25(OH)2D3-induced gene activation. In conclusion, our study shows that activated CD4+ T cells can produce 1,25(OH)2D3, and that 1,25(OH)2D3 induces a 2-fold up-regulation of the VDR protein expression in activated CD4+ T cells by protecting the VDR against proteasomal degradation. [ABSTRACT FROM AUTHOR]

Substances that penetrate the skin surface can act as allergens and induce a T cell-mediated inflammatory skin disease called contact hypersensitivity (CHS). IL-17 is a key cytokine in CHS and was originally thought to be produced solely by CD4+ T cells. However, it is now known that several cell types, including γδ T cells, can produce IL-17. In this study, we determine the role of γδ T cells, especially dendritic epidermal T cells (DETCs), in CHS. Using a well-established model for CHS in which 2,4-dinitrofluorobenzene (DNFB) is used as allergen, we found that gd T cells are important players in CHS. Thus, more IL-17-producing DETCs appear in the skin following exposure to DNFB in wild-type mice, and DNFB-induced ear swelling is reduced by ∼50% in TCRd-/- mice compared with wild-type mice. In accordance, DNFB-induced ear swelling was reduced by ∼50% in IL-17-/- mice. We show that DNFB triggers DETC activation and IL-1β production in the skin and that keratinocytes produce IL-1β when stimulated with DNFB. We find that DETCs activated in vitro by incubation with anti-CD3 and IL-1β produce IL-17. Importantly, we demonstrate that the IL-1R antagonist anakinra significantly reduces CHS responses, as measured by decreased ear swelling, inhibition of local DETC activation, and a reduction in the number of IL-17+ βδ T cells and DETCs in the draining lymph nodes. Taken together, we show that DETCs become activated and produce IL-17 in an IL-1β-dependent manner during CHS, suggesting a key role for DETCs in CHS. [ABSTRACT FROM AUTHOR]

In this article, we report that cutaneous T cell lymphoma (CTCL) cells and tissues ubiquitously express the immunosuppressive cell surface protein CD80 (B7-1). CD80 expression in CTCL cells is strictly dependent on the expression of both members of the STAT5 family, STAT5a and STAT5b, as well as their joint ability to transcriptionally activate the CD80 gene. In IL-2-dependent CTCL cells, CD80 expression is induced by the cytokine in a Jak1/3- and STAT5a/b-dependent manner, whereas in the CTCL cells with constitutive STAT5 activation, CD80 expression is also STAT5a/b dependent but is independent of Jak activity. Although depletion of CD80 expression does not affect the proliferation rate and viability of CTCL cells, induced expression of the cellinhibitory receptor of CD80, CD152 (CTLA-4), impairs growth of the cells. Coculture of CTCL cells with normal T lymphocytes consisting of both CD4+ and CD8+ populations or the CD4+ subset alone, transfected with CD152 mRNA, inhibits proliferation of normal T cells in a CD152- and CD80-dependent manner. These data identify a new mechanism of immune evasion in CTCL and suggest that the CD80-CD152 axis may become a therapeutic target in this type of lymphoma. [ABSTRACT FROM AUTHOR]

Anaplastic lymphoma kinase (ALK), physiologically expressed only by nervous system cells, displays a remarkable capacity to transform CD4+ T lymphocytes and other types of nonneural cells. In this study, we report that activity of nucleophosmin (NPM)/ALK chimeric protein, the dominant form of ALK expressed in T cell lymphomas (TCLs), closely resembles cell activation induced by IL-2, the key cytokine supporting growth and survival of normal CD4+ T lymphocytes. Direct comparison of gene expression by ALK+ TCL cells treated with an ALK inhibitor and IL-2-dependent ALK- TCL cells stimulated with the cytokine revealed a very similar, albeit inverse, gene-regulation pattern. Depending on the analysis method, up to 67% of the affected genes were modulated in common by NPM/ALK and IL-2. Based on the gene expression patterns, Jak/ STAT- and IL-2-signaling pathways topped the list of pathways identified as affected by both IL-2 and NPM/ALK. The expression dependence on NPM/ALK and IL-2 of the five selected genes--CD25 (IL-2Rα), Egr-1, Fosl-1, SOCS3, and Irf-4--was confirmed at the protein level. In both ALK+ TCL and IL-2-stimulated ALK- TCL cells, CD25, SOCS3, and Irf-4 genes were activated predominantly by the STAT5 and STAT3 transcription factors, whereas transcription of Egr-1 and Fosl-1 was induced by the MEK-ERK pathway. Finally, we found that Egr-1, a protein not associated previously with either IL-2 or ALK, contributes to the cell proliferation. These findings indicate that NPM/ALK transforms the target CD4+ T lymphocytes, at least in part, by using the pre-existing, IL-2-dependent signaling pathways. [ABSTRACT FROM AUTHOR]