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Differentiation of naive CD4+ T cells into effector T cells is a dynamic process in which the cells are polarized into T helper (Th) subsets. The subsets largely consist of four fundamental categories: Th1, Th2, Th17, and regulatory T cells. We show that human memory CD4+ T cells can produce hepatocyte growth factor (HGF), a pleiotropic cytokine which can affect several tissue types through signaling by its receptor, c-Met. In vitro differentiation of T cells into Th-like subsets revealed that HGF producing T cells increase under Th1 conditions. Enrichment of HGF producing cells was possible by targeting cells with surface CD30 expression, a marker discovered through single-cell RNA-sequencing. Furthermore, pharmacological inhibition of PI3K or mTOR was found to inhibit HGF mRNA and protein, while an Akt inhibitor was found to increase these levels. The findings suggest that HGF producing T cells could play a role in disease where Th1 are present. [ABSTRACT FROM AUTHOR]

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]

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]

The coronavirus disease 2019 (COVID-19) pandemic has severely impacted daily life all over the world. Any measures to slow down the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and to decrease disease severity are highly requested. Recent studies have reported inverse correlations between plasma levels of vitamin D and susceptibility to SARS-CoV-2 infection and COVID-19 severity. Therefore, it has been proposed to supplement the general population with vitamin D to reduce the impact of COVID-19. However, by studying the course of COVID-19 and the immune response against SARS-CoV-2 in a family with a mutated, non-functional vitamin D receptor, we here demonstrate that vitamin D signaling was dispensable for mounting an efficient adaptive immune response against SARS-CoV-2 in this family. Although these observations might not directly be transferred to the general population, they question a central role of vitamin D in the generation of adaptive immunity against SARS-CoV-2. [ABSTRACT FROM AUTHOR]

The active form of vitamin D3 (1,25(OH)2D3) has a great impact on T cell effector function. Thus, 1,25(OH)2D3 promotes T helper 2 (Th2) and regulatory T (Treg) cell function and concomitantly inhibits Th1 and Th17 cell function. Thus, it is believed that vitamin D exerts anti-inflammatory effects. However, vitamin D binding protein (DBP) strongly binds both 1,25(OH)2D3 and the precursor 25(OH)D3, leaving only a minor fraction of vitamin D in the free, bioavailable form. Accordingly, DBP in physiological concentrations would be expected to block the effect of vitamin D on T cells and dendritic cells. In the present study, we show that pro-inflammatory, monocyte-derived M1 macrophages express very high levels of the 25(OH)D-1α-hydroxylase CYP27B1 that enables them to convert 25(OH)D3 into 1,25(OH)2D3 even in the presence of physiological concentrations of DBP. Co-cultivation of M1 macrophages with T cells allows them to overcome the sequestering of 25(OH)D3 by DBP and to produce sufficient levels of 1,25(OH)2D3 to affect T cell effector function. This study suggests that in highly inflammatory conditions, M1 macrophages can produce sufficient levels of 1,25(OH)2D3 to modify T cell responses and thereby reduce T cell-mediated inflammation via a vitamin D-mediated negative feed-back loop. [ABSTRACT FROM AUTHOR]

Th22 cells constitute a recently described CD4+ T cell subset defined by its production of interleukin (IL)-22. The action of IL-22 is mainly restricted to epithelial cells. IL-22 enhances keratinocyte proliferation but inhibits their differentiation and maturation. Dysregulated IL-22 production has been associated to some inflammatory skin diseases such as atopic dermatitis and psoriasis. How IL-22 production is regulated in human T cells is not fully known. In the present study, we identified conditions to generate Th22 cells that do not co-produce IL-17 from naïve human CD4+ T cells. We show that in addition to the transcription factors AhR and RORγt, the active form of vitamin D3 (1,25(OH)2D3) regulates IL-22 production in these cells. By studying T cells with a mutated vitamin D receptor (VDR), we demonstrate that the 1,25(OH)2D3-induced inhibition of il22 gene transcription is dependent on the transcriptional activity of the VDR in the T cells. Finally, we identified a vitamin D response element (VDRE) in the il22 promoter and demonstrate that 1,25(OH)2D3-VDR directly inhibits IL-22 production via this repressive VDRE. [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]

The active form of vitamin D, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), mediates its immunomodulatory effects by binding to the vitamin D receptor (VDR). Here, we describe a new point mutation in the DNA-binding domain of the VDR and its consequences for 1,25(OH)2D3 signaling in T cells from heterozygous and homozygous carriers of the mutation. The mutation did not affect the overall structure or the ability of the VDR to bind 1,25(OH)2D3 and the retinoid X receptor. However, the subcellular localization of the VDR was strongly affected and the transcriptional activity was abolished by the mutation. In heterozygous carriers of the mutation, 1,25(OH)2D3-induced gene regulation was reduced by ~ 50% indicating that the expression level of wild-type VDR determines 1,25(OH)2D3 responsiveness in T cells. We show that vitamin D-mediated suppression of vitamin A-induced gene regulation depends on an intact ability of the VDR to bind DNA. Furthermore, we demonstrate that vitamin A inhibits 1,25(OH)2D3-induced translocation of the VDR to the nucleus and 1,25(OH)2D3-induced up-regulation of CYP24A1. Taken together, this study unravels novel aspects of vitamin D signaling and function of the VDR in human T cells. [ABSTRACT FROM AUTHOR]

Background: The thioredoxin-interacting protein (TXNIP) is involved in cellular metabolism and cell proliferation, and recently, deficient expression of TXNIP has been associated with progression and poor outcome for cancer patients. Objectives: To assess TXNIP expression and function in malignant T cells from cutaneous T-cell lymphoma (CTCL). Methods: CTCL-derived malignant (MyLa2059, PB2B) and non-malignant (MyLa1850) cell lines were analysed by Western blotting and qPCR for TXNIP expression. Subsequently, the malignant CTCL cell lines were treated with GSK126 – an inhibitor of enhancer of zeste homolog 2 (EZH2) methyltransferase activity or assessed by bisulphite sequencing for TXNIP promoter methylation. Methylation was also assessed with the demethylating agent 5-azacytidine (5AZA). Finally, TXNIP was overexpressed in the malignant PB2B cell line via plasmid transduction, and the effect of TXNIP was further analysed by flow cytometry. Results: We report on low expression of TXNIP protein in all cell lines representing different subtypes and stages of CTCL when compared to non-malignant T cells. Epigenetic silencing and other mechanisms were involved in the repression of TXNIP whereas forced expression of TXNIP strongly inhibited proliferation of malignant T cells. Conclusions: Epigenetic silencing and other as yet unknown mechanisms repress TXNIP expression in malignant T cells. As forced expression of TXNIP inhibits malignant proliferation, we propose that TXNIP is a putative tumour suppressor in CTCL. [ABSTRACT FROM AUTHOR]

Background: Mycosis fungoides (MF), the most common form of cutaneous T-cell lymphoma (CTCL), is a lymphoproliferative disorder characterized by proliferation of malignant T cells in a chronic inflammatory environment in the skin. The nature of MF is still not fully understood, but aberrant microRNA (miR) expression and function seem to play an important role in the pathogenesis and disease progression and have been proposed as a putative disease marker. Recent studies have reported aberrant expression of miR-93 in situin MF lesions and linked dysregulated miR-93 expression to advanced stages of MF. However, the pathophysiological role of miR-93 in MF is unknown. Objective: Here, we provide the first evidence that miR-93 targets the cell cycle regulator cyclin-dependent kinase inhibitor p21 and promotes growth of malignant T cells in MF. Methods/Results: Thus, inhibition of miR-93 in MF patient-derived malignant T-cell lines increases expression of p21 and inhibition of malignant proliferation. Notably, treatment with the histone deacetylase inhibitor Vorinostat (SAHA) reduces miR-93 expression and enhances p21 expression in the malignant T cells. Importantly, transfection with an miR-93 mimic partly blocks SAHA-induced p21 expression. Conclusions: we provide evidence that enhanced expression of the putative oncogenic miR, miR-93, represses the cell cycle inhibitor p21 and promotes proliferation of malignant T cells. Moreover, we demonstrate that SAHA triggers p21 expression – at least partly – through an inhibition of miR-93. [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]

Background: The voltage-gated potassium channel Kv1.3 (KCNA3) is expressed by effector memory T cells (TEM) and plays an important role in their activation and proliferation. Mycosis fungoides (MF), the most common subtype of cutaneous T-cell lymphoma (CTCL), was recently proposed to be a malignancy of skin-resident TEM. However, the expression of Kv1.3 in CTCL has not been investigated.Objectives: This study aims to examine the expression of Kv1.3 in situ and in vitro in CTCL.Methods: The expression of Kv1.3 was examined by immunohistochemistry in skin lesions from 38 patients with MF, 4 patients with Sézary syndrome (SS), and 27 patients with benign dermatosis. In 4 malignant T-cell lines of CTCL (Myla2059, PB2B, SeAx, and Mac2a) and a non-malignant T-cell line (MyLa1850), the expression of Kv1.3 was determined by flow cytometry. The proliferation of those cell lines treated with various concentrations of Kv1.3 inhibitor ShK was measured by 3H-thymdine incorporation.Results: Half of the MF patients (19/38) displayed partial Kv1.3 expression including 1 patient with moderate Kv1.3 positivity, while the other half (19/38) exhibited Kv1.3 negativity. An almost identical distribution was observed in patients with benign conditions, that is, 44.4% (12/27) were partially positive for Kv1.3 including 1 patient with moderate Kv1.3 positivity, while 55.6% (15/27) were Kv1.3 negative. In contrast, 3 in 4 SS patients displayed partial Kv1.3 positivity including 2 patients with weak staining and 1 with moderate staining, while 1 in 4 SS patients was Kv1.3 negative. In addition, all malignant T-cell lines, and a non-malignant T-cell line, displayed low Kv1.3 surface expression with a similar pattern. Whereas 2 cell lines (PB2B and Mac2a) were sensitive to Kv1.3 blockade, the other 2 (Myla2059 and SeAx) were completely resistant.Conclusions: We provide the first evidence of a heterogeneous Kv1.3 expression in situ in CTCL lesions. [ABSTRACT FROM AUTHOR]

• 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]

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]

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]

Mutations in the filaggrin gene (Flg) are associated with increased systemic levels of Th17 cells and increased IL-17A production following antigen exposure in both humans and mice. In addition to Th17 cells, γδ T cells can produce IL-17A. The differentiation of γδ T cells to either IFNγ or IL-17A-producing (γδT17) cells is mainly determined in the thymus. Interestingly, it has been reported that filaggrin is expressed in the Hassall bodies in the human thymic medulla. However, whether filaggrin affects γδ T cell development is not known. Here, we show that filaggrin-deficient flaky tail (ft/ft) mice have an increased number of γδT17 cells in the spleen, epidermis, and thymus compared to wild-type (WT) mice. We demonstrate that filaggrin is expressed in the mouse thymic medulla and that blocking the egress of cells from the thymus results in accumulation of Vγ2+ γδT17 cells in the thymus of adult ft/ft mice. Finally, we find increased T cell receptor expression levels on γδ T cells and increased levels of IL-6 and IL-23 in the thymus of ft/ft mice. These findings demonstrate that filaggrin is expressed in the mouse thymic medulla and that production of Vγ2+ γδT17 cells is dysregulated in filaggrin-deficient ft/ft mice. [ABSTRACT FROM AUTHOR]

Tuberculosis (TB) presents a serious health problem with approximately one-third of the world's population infected with Mycobacterium tuberculosis in a latent state. Experience from the pre-antibiotic era and more recent clinical studies have established a beneficial role of sunlight and vitamin D in patients with TB. At the same time, experimental data have shown that Th1 cells through production of IFNγ are crucial for cathelicidin release by macrophages, bacterial killing, and containment of M. tuberculosis in granulomas. Paradoxically, vitamin D has repeatedly been ascribed an immune-suppressive function inhibiting Th1 differentiation and production of IFNγ in T cells. The aim of this study was to investigate this apparent paradox. We studied naïve human CD4+ T cells activated either with CD3 and CD28 antibodies or with allogeneic dendritic cells (DC) stimulated with heat-killed M. tuberculosis (HKMT) or purified toll-like receptor (TLR) ligands. We show that vitamin D does not block differentiation of human CD4+ T cells to Th1 cells and that interleukin (IL)-12 partially counteracts vitamin D-mediated inhibition of IFNγ production promoting production of equal amounts of IFNγ in Th1 cells in the presence of vitamin D as in T cells activated in the absence of vitamin D and IL-12. Furthermore, we show that HKMT and TLR2 ligands strongly downregulate cathelicidin expression in DC and that vitamin D counteracts this by upregulating cathelicidin expression. In conclusion, we demonstrate that vitamin D counteracts M. tuberculosis-induced cathelicidin downregulation and allows Th1 differentiation and IFNγ secretion. [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]

Midline 1 (MID1) is a microtubule-associated ubiquitin ligase that regulates protein phosphatase 2A activity. Loss-of-function mutations in MID1 lead to the X-linked Opitz G/BBB syndrome characterized by defective midline development during embryogenesis. Here, we show that MID1 is strongly upregulated in murine cytotoxic lymphocytes (CTLs), and that it controls TCR signaling, centrosome trafficking, and exocytosis of lytic granules. In accordance, we find that the killing capacity of MID1−/− CTLs is impaired. Transfection of MID1 into MID1−/− CTLs completely rescued lytic granule exocytosis, and vice versa, knockdown of MID1 inhibited exocytosis of lytic granules in WT CTLs, cementing a central role for MID1 in the regulation of granule exocytosis. Thus, MID1 orchestrates multiple events in CTL responses, adding a novel level of regulation to CTL activation and cytotoxicity. [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]

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]

Recently, miR-155 has been implicated in cutaneous T-cell lymphoma (CTCL). Thus, elevated levels of miR-155 were observed in skin lesions from CTCL patients as judged from qPCR and micro-array analysis and aberrant, high miR-155 expression was associated with severe disease. Moreover, miR-155 promoted proliferation of malignant T cells in vitro. Little is, however, known about which cell types express miR-155 in vivo in CTCL skin lesions. Here, we study miR-155 expression using in situ hybridization (ISH) with a miR-155 probe, a negative control (scrambled), and a miR-126 probe as a positive control in nine patients with mycosis fungoides, the most frequent subtype of CTCL. We provide evidence that both malignant and non-malignant T cells stain weakly to moderately positive with the miR-155 probe, but generally negative with the miR-126 and negative control probes. Reversely, endothelial cells stain positive for miR-126 and negative for miR-155 and the control probe. Solitary T cells with a malignant morphology display brighter staining with the miR-155 probe. Taken together, our findings suggest that both malignant and non-malignant T cells express miR-155 in situ in CTCL. Moreover, they indicate heterogeneity in miR-155 expression among malignant T cells. [ABSTRACT FROM AUTHOR]

Here, we have studied vascular endothelial growth factor receptor-3 (VEGFR-3) expression in mycosis fungoides (MF), the most common type of cutaneous T-cell lymphoma (CTCL). Immunohistochemistry revealed that in two-thirds of 34 patients, VEGFR-3 was expressed in situ by both tumor and stromal cells irrespective of the disease stage. The natural VEGFR-3 ligand, VEGF-C, partially protected malignant T-cell lines from growth inhibition by the histone deacetylase inhibitor, suberoylanilide hydroxamic acid (SAHA). Whereas the malignant T cells did not produce VEGF-C in vitro, its expression was induced during tumor formation in vivo in a xenograft mouse model of MF. In conclusion, malignant and stromal cells express high levels of VEGFR-3 in all stages of MF. Moreover, malignant T cells trigger enhanced VEGF-C expression in fibroblasts, suggesting that cross-talk between tumor and stromal cells plays a role in lymphangiogenesis and possibly disease progression. [ABSTRACT FROM AUTHOR]

Successful/effective cancer therapy in low grade lymphoma is often hampered by cell resistance to anti-neoplastic agents. The crucial mechanisms responsible for this phenomenon are poorly understood. Overcoming resistance of tumor cells to anticancer agents, such as proteasome inhibitors, could improve their clinical efficacy. Using cutaneous T-cell lymphoma (CTCL) as a model of the chemotherapy-resistant peripheral lymphoid malignancy, we demonstrated that resistance to proteasome inhibition involved a signaling between the oncogene cMyc and miR-125b-5p. Bortezomib repressed cMyc and simultaneously induced miR-125b-5p that exerted a cytoprotective effect through the downmodulation of MAD4. Overexpression of cMyc repressed miR-125b-5p transcription and sensitized lymphoma cells to bortezomib. The central role of miR-125b-5p was further confirmed in a mouse model of T-cell lymphoma, where xenotransplantation of human CTCL cells overexpressing miR-125b-5p resulted in enhanced tumor growth and a shorter median survival. Our findings describe a novel mechanism through which miR-125b-5p not only regulates tumor growth in vivo, but also increases cellular resistance to proteasome inhibitors via modulation of MAD4. [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: 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]

Please cite this paper as: A novel xenograft model of cutaneous T-cell lymphoma. Experimental Dermatology 2010; : 1096-1102. Cutaneous T-cell lymphomas (CTCLs) are characterized by accumulation of malignant T cells in the skin. Early disease resembles benign skin disorders but during disease progression cutaneous tumors develop, and eventually the malignant T cells can spread to lymph nodes and internal organs. However, because of the lack of suitable animal models, little is known about the mechanisms driving CTCL development and progression in vivo. Here, we describe a novel xenograft model of tumor stage CTCL, where malignant T cells (MyLa2059) are transplanted to NOD/SCID-B2m (NOD.Cg-Prkdc B2m/J) mice. Subcutaneous transplantation of the malignant T cells led to rapid tumor formation in 43 of 48 transplantations, whereas transplantation of non-malignant T cells isolated from the same donor did not result in tumor development. Importantly, the tumor growth was significantly suppressed in mice treated with vorinostat when compared to mice treated with vehicle. Furthermore, in most mice the tumors displayed subcutaneous and/or lymphatic dissemination. Histological, immunohistochemical and flow cytometric analyses confirmed that both tumors at the inoculation site, as well as distant subcutaneous and lymphatic tumors, originated from the transplanted malignant T cells. In conclusion, we describe a novel mouse model of tumor stage CTCL for future studies of disease dissemination and preclinical evaluations of new therapeutic strategies. [ABSTRACT FROM AUTHOR]

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]

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.

An amendment to this paper has been published and can be accessed via a link at the top of the paper. [ABSTRACT FROM AUTHOR]

Simple Summary: JAK3 plays an important role in the pathogenesis of cutaneous T cell lymphoma. JAK3 belongs to the Janus kinase family of receptor-associated tyrosine kinases located in cytoplasm adjacent to the plasma membrane. In this study, we show that JAK3 can also be ectopically expressed in the nucleus in CTCL cell lines and primary cells from CTCL patients. Importantly, JAK3 interacts with the nuclear protein RNA polymerase II and phosphorylates Histone H3. Thus, our data provide first evidence for nuclear expression of JAK3 and interactions with key nuclear proteins in malignant T cells suggesting a novel non-canonical role in CTCL. Perturbation in JAK-STAT signaling has been reported in the pathogenesis of cutaneous T cell lymphoma (CTCL). JAK3 is predominantly associated with the intra-cytoplasmic part of IL-2Rγc located in the plasma membrane of hematopoietic cells. Here we demonstrate that JAK3 is also ectopically expressed in the nucleus of malignant T cells. We detected nuclear JAK3 in various CTCL cell lines and primary malignant T cells from patients with Sézary syndrome, a leukemic variant of CTCL. Nuclear localization of JAK3 was independent of its kinase activity whereas STAT3 had a modest effect on nuclear JAK3 expression. Moreover, JAK3 nuclear localization was only weakly affected by blockage of nuclear export. An inhibitor of the nuclear export protein CRM1, Leptomycin B, induced an increased expression of SOCS3 in the nucleus, but only a weak increase in nuclear JAK3. Importantly, immunoprecipitation experiments indicated that JAK3 interacts with the nuclear protein POLR2A, the catalytic subunit of RNA Polymerase II. Kinase assays showed tyrosine phosphorylation of recombinant human Histone H3 by JAK3 in vitro—an effect which was blocked by the JAK inhibitor (Tofacitinib citrate). In conclusion, we provide the first evidence of nuclear localization of JAK3 in malignant T cells. Our findings suggest that JAK3 may have a cytokine-receptor independent function in the nucleus of malignant T cells, and thus a novel non-canonical role in CTCL. [ABSTRACT FROM AUTHOR]

In addition to antigen-driven signals, T cells need co-stimulatory signals for robust activation. Several receptors, including members of the tumor necrosis factor receptor superfamily (TNFRSF), can deliver co-stimulatory signals to T cells. Thioredoxin interacting protein (TXNIP) is an important inhibitor of glucose uptake and cell proliferation, but it is unknown how TXNIP is regulated in T cells. The aim of this study was to determine expression levels and regulation of TXNIP in human T cells. We found that naïve T cells express high levels of TXNIP and that treatment of blood samples with TNF results in rapid down-regulation of TXNIP in the T cells. TNF-induced TXNIP down-regulation correlated with increased glucose uptake. Furthermore, we found that density gradient centrifugation (DGC) induced down-regulation of TXNIP. We demonstrate that DGC induced TNF production that paralleled the TXNIP down-regulation. Treatment of blood with toll-like receptor (TLR) ligands induced TNF production and TXNIP down-regulation, suggesting that damage-associated molecular patterns (DAMPs), such as endogenous TLR ligands, released during DGC play a role in DGC-induced TXNIP down-regulation. Finally, we demonstrate that TNF-induced TXNIP down-regulation is dependent on caspase activity and is caused by caspase-mediated cleavage of TXNIP. [ABSTRACT FROM AUTHOR]

The article reports on research which was conducted to investigate the validity of a diagnostic microRNA classifier in cutaneous T-cell lymphomas (CTCL). Researchers evaluated the classifier with 78 patients using a standard TaqMan real-time quantitative polymerase chain reaction (qRT-PCR) assay. They found that while the classifier is diagnostically informative in a wide variety of malignancies, it alone is not sufficient to identify cases of CTCL.

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]

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]

Inappropriately regulated expression of interleukin (IL)-17A is associated with the development of inflammatory diseases and cancer. However, little is known about the role of other IL-17 family members in carcinogenesis. Here, we show that a set of malignant T-cell lines established from patients with cutaneous T-cell lymphoma (CTCL) spontaneously secrete IL-17F and that inhibitors of Janus kinases and Signal transducer and activator of transcription 3 are able to block that secretion. Other malignant T-cell lines produce IL-17A but not IL-17F. Upon activation, however, some of the malignant T-cell lines are able to coexpress IL-17A and IL-17F, leading to formation of IL-17A/F heterodimers. Clinically, we demonstrate that IL-17F messenger RNA expression is significantly increased in CTCL skin lesions compared with healthy donors and patients with chronic dermatitis. IL-17A expression is also increased and a significant number of patients express high levels of both IL-17A and IL-17F. Concomitantly, we observed that the expression of the IL-17 receptor is significantly increased in CTCL skin lesions compared with control subjects. Importantly, analysis of a historic cohort of 60 CTCL patients indicates that IL-17F expression is associated with progressive disease. These findings implicate IL-17F in the pathogenesis of CTCL and suggest that IL-17 cytokines and their receptors may serve as therapeutic targets. [ABSTRACT FROM AUTHOR]

IL-17 is a proinflammatory cytokine that is crucial for the host's protection against a range of extracellular pathogens. However, inappropriately regulated expression of IL-17 is associated with the development of inflammatory diseases and cancer. In cutaneous T-cell lymphoma (CTCL), malignant T cells gradually accumulate in skin lesions characterized by massive chronic inflammation, suggesting that IL-17 could be involved in the pathogenesis. In this study we show that IL-17 protein is present in 10 of 13 examined skin lesions but not in sera from 28 CTCL patients. Importantly, IL-17 expression is primarily observed in atypical lymphocytes with characteristic neoplastic cell morphology. In accordance, malignant T-cell lines from CTCL patients produce IL-17 and the synthesis is selectively increased by IL-2 receptor β chain cytokines. Small-molecule inhibitors or small interfering RNA against Jak3 and signal transducer and activator of transcription 3 (Stat3) reduce the production of IL-17, showing that the Jak3/Stat3 pathway promotes the expression of the cytokine. In summary, our findings indicate that the malignant T cells in CTCL lesions express IL-17 and that this expression is promoted by the Jak3/Stat3 pathway. [ABSTRACT FROM AUTHOR]

Studies intestinal T cells from Crohn's disease and healthy volunteers. Attempt to show that STAT3 and STAT4 are constitutively activated in Crohn's patients but not in healthy volunteers; Critical approach for better understanding the immunopathogenesis of Crohn's disease.