The crucial role of IL‐22 and its receptor in thymus and activation regulated chemokine production and T‐cell migration by house dust mite extract

House dust mite (HDM) is known as one of the factors that causes atopic dermatitis (AD). Interleukin (IL)‐22 and thymus and activation regulated chemokine (TARC) are related to skin inflammatory disease and highly expressed in AD lesions. However, the effects of HDM on IL‐22 production in T cells and on TARC production and IL‐22Rα receptor expression in keratinocytes are unknown. To identify the role of HDM in keratinocytes and T cells, we investigated IL‐22Rα expression and TARC production in the human keratinocyte cell line HaCaT and IL‐22 production in T cells treated with HDM extract as well as their roles in HDM‐induced skin inflammation. HDM extract not only increased IL‐22Rα expression and TARC production in HaCaT but also enhanced IL‐22, tumor necrosis factor (TNF)‐α and interferon (IFN)‐γ production in T cells. The HDM extract‐induced IL‐22 from T cells significantly increased the production of IL‐1α, IL‐6 and TARC in HaCaT cells. In addition, we found that TARC produced in HDM extract‐treated HaCaT induced T‐cell recruitment. These results suggest that there is a direct involvement of HDM extract‐induced IL‐22 in TARC production and T‐cell migration. Taken together, TARC production in HaCaT through the interaction between IL‐22 and IL‐22Rα facilitates T‐cell migration. These data show one of the reasons for inflammation in the skin lesions of AD patients.     

Expression of T‐cell immunoglobulin and immunoreceptor tyrosine‐based inhibitory motif domain on CD4+ T cells in patients with atopic dermatitis

The T‐cell immunoglobulin and immunoreceptor tyrosine‐based inhibitory motif domain (TIGIT) is a co‐inhibitory receptor mainly expressed on T cells. Although TIGIT plays an important role in various autoimmune diseases, its role in atopic dermatitis (AD) remains unclear. In this study, we examined the expression levels of TIGIT and their association with clinical features in patients with AD. TIGIT expression on CD4⁺ T cells, central memory T cells, effector memory T cells and regulatory T cells was determined by flow cytometry. CD4⁺ T cells exhibited enhanced TIGIT expression in patients with AD compared with healthy individuals. In particular, effector memory T cells and regulatory T cells, but not central memory T cells, exhibited higher TIGIT expression in patients with AD than in healthy individuals. The frequency of TIGIT⁺ cells among CD4⁺ T cells was significantly increased in patients with mild AD compared with healthy individuals, while decreased in patients with severe AD. Consistently, the frequency of TIGIT⁺ cells among CD4⁺ T cells was negatively correlated with both serum thymus and activation‐regulated chemokine levels and immunoglobulin E levels in patients with AD. Furthermore, TIGIT expression on CD4⁺ T cells inhibited cell proliferation in patients with AD. These results suggest that TIGIT expression on CD4⁺ T cells in patients with AD may be increased to suppress chronic cutaneous inflammation. Moreover, TIGIT expression may be impaired in a subset of patients with AD, leading to a deterioration of skin inflammation. Our study may provide new insight into a TIGIT pathway‐based therapeutic approach for AD.     

Impaired T‐cell‐dependent protection against Leishmania major infection in HIV‐positive patients is associated with worsened disease outcome

Cutaneous leishmaniasis (CL) patients coinfected with HIV are known to show a more severe, prolonged course of disease; the immunological basis is not known. We now assessed clinical features, sera and skin biopsies of HIV⁺ and HIV^? patients with CL to identify drivers of increased susceptibility to Leishmania. CL lesion numbers, surface, and healing duration were significantly increased in HIV⁺ as compared to HIV^? patients (2.5, 14 and >4‐fold, respectively). Patients with HIV infection exhibited lower serum Leishmania‐specific IgG levels and decreased IL‐6 and IL‐8. Most importantly, dramatically decreased numbers of CD4⁺ T cells (approximately eightfold), but not CD8⁺ cells, together with fewer CXCR3⁺ Th1 cells, fewer Foxp3⁺ effector/regulatory T cells, and reduced levels of IFN‐γ expression were found in lesional skin. Our findings suggest that compromised CD4⁺ T‐cell responses may be responsible for worsened disease outcome leading to defects in parasite elimination in the absence of sufficient numbers of IFN‐γ‐producing Th1 cells.     

Oral administration of poly‐γ‐glutamic acid prevents the development of atopic dermatitis in NC/Nga mice

Bacillus subtilis‐derived poly‐γ‐glutamic acid (γPGA) has demonstrated adjuvant activity in promoting Th1/Th17 cell differentiation. Here, the NC/Nga (NC) mouse model was used to determine whether γPGA modulates the outcome of atopic dermatitis (AD), which is known to be a Th2‐biased immune disease. We found that oral administration of γPGA dramatically reduced the development of AD in NC mice. Antigen‐presenting cells activated with γPGA produced pro‐inflammatory cytokines, such as IL12/23 and IFNγ, which, in turn, induced the differentiation of Th1 and Th17 cells. Concomitantly, Th2 responses, such as high levels of serum IgE, were dramatically decreased. Furthermore, in vivo γPGA treatment altered several cellular components of allergic reactions, such as mast cells and eosinophils. Taken together, our results strongly demonstrate that in vivo treatment with γPGA at early time points can prevent the development of AD in NC mice and suggest that γPGA may have therapeutic applications for human AD.     

Frequencies of circulating allergen‐specific T cells temporally associate with longitudinal changes in severity of cutaneous atopic disease

Increased levels of allergen‐specific T‐cells have been documented in the peripheral blood of patients with atopic dermatitis (AD) compared with nonatopic controls. However, little is known about how these relate to disease severity. This study sought to examine if frequencies of circulating allergen‐specific T cells correlate with changes in clinical disease severity in a cohort of seven adults with AD who were positive for human leucocyte antigen DRB1*1501. We found that frequencies of allergen‐specific CD4+ T cells across the study group were not significantly (P > 0.05) associated with clinical disease severity; however, longitudinal changes within an individual did correlate significantly (P < 0.01) with changes in disease severity. These findings support a role for allergen‐specific T‐cells in disease pathogenesis.     

Time‐dependent progression from the acute to chronic phases in atopic dermatitis induced by epicutaneous allergen stimulation in NC/Nga mice

Atopic dermatitis (AD) is a complicated skin condition influenced by genetic background and environmental factors. In this study, we applied Dermatophagoides farinae body extract (DfE) to the barrier‐disrupted skin of NC/Nga mice twice a week for 8 weeks to identify the clinical and immunological factors in AD progression. Repeated application of the DfE to the skin of NC/Nga mice showed the similar consequences for the natural course of progression in human AD, histologically and immunologically. We confirmed that the AD‐like skin lesions in NC/Nga mice did not last for the whole period of our experiment in spite of repeated topical applications of DfE twice a week. Topical DfE stimulation increased the skin mRNA expressions of Th1‐, Th2‐ and Th17‐related cytokines in the acute phase. The expression patterns of IL‐4 and IL‐13 in splenic T cells and skin lesions were consistent with the time course alterations of clinical features of AD‐like skin symptoms. We also showed that there was a remission phase either just before or right after the chronic phase in this experimental model. Interestingly, splenic T‐cell‐derived IL‐5 expression began to increase in the chronic phase, while skin‐derived IL‐5 mRNA expression increased in the acute phase. In conclusion, our results suggest that we should pay attention to the characteristics of each stage of AD progression and choose a suitable corresponding stage of animal model not only to elucidate the pathogenesis of AD but also to develop and evaluate therapeutic drugs for AD.     

Elevated serum galectin‐9 levels in patients with atopic dermatitis

Galectin‐9 is a member of the galectin family that has a wide spectrum of biological functions. Among them, galectin‐9 has been known mainly as a potent chemoattractant for eosinophils. In addition, galectin‐9 alters the T‐cell balance by negatively regulating T‐helper (Th)1 and Th17 cells, resulting in Th2 polarization. Atopic dermatitis (AD) is a skin allergic disease characterized by peripheral eosinophilia, mast cell activation and predominance of Th2 cells. To investigate possible roles of galectin‐9 in AD, we measured serum galectin‐9 levels in AD patients and investigated galectin‐9 expression in lesional skin by immunohistochemistry. Serum galectin‐9 levels in patients with AD were significantly higher than those in healthy controls and correlated with the Eczema Area and Severity Index. Serum galectin‐9 levels were decreased after treatment, accompanied by improvement of skin lesions. Immunohistochemical study revealed that galectin‐9 was expressed on epidermal keratinocytes and mast cells in lesional skin of AD. Our results suggest that elevated galectin‐9 expression is associated with progression of AD and that galectin‐9 could be a therapeutic target in AD.     

The effects of vitamin K1 and vitamin K2 on the proliferation,cytokine production and regulatory T‐cell frequency in peripheral blood mononuclear cells of paediatric atopic dermatitis patients

We estimated the pharmacological efficacy of vitamin K₁ (VK₁) and VK₂ on the mitogen‐activated peripheral blood mononuclear cells (PBMCs) of paediatric atopic dermatitis (AD) patients. VK₂ suppressed the in vitro proliferation of T‐cell mitogen‐activated PBMCs of AD patients. In contrast, VK₁ had little effect on the PBMC proliferation. The IL‐2 production from the activated PBMCs of AD patients significantly increased (P < .05), while the production significantly decreased by 100 μmol L^?1 VK₂ (P < .01). In addition, 100 μmol L^?1 VK₂ reduced the percentage of CD4+ and CD4+CD25+ cells in PBMCs. These results suggest that VK2 can modulate T‐cell function in PBMCs of AD patients.     

Role of YAP-related T cell imbalance and epidermal keratinocyte dysfunction in the pathogenesis of atopic dermatitis

BackgroundAtopic dermatitis (AD) is characterized by impaired skin barrier function and immune system dysfunction. The expression and role of Yes-associated protein (YAP) in AD are unclear.ObjectiveTo characterize the role of the YAP in T cell imbalance and epidermal keratinocyte dysfunction in the pathogenesis of AD.MethodsWe included 35 patients with AD (21 acute and 14 chronic). An AD mouse model was constructed using 2,4-dinitrofluorobenzene, and AD-like inflammatory cell model was constructed using TNF-α/IFN-γ-activated HaCaT cells. The proportion of Th1/Th2/Th17/Treg cells was detected using flow cytometry. After mononuclear cells were obtained from human peripheral blood or mouse spleen and induced to differentiate into different T cell subsets, YAP mRNA and protein expression were analyzed. Up-regulation of YAP was induced by lentivirus and down-regulation of YAP was induced by its specific inhibitor verteporfin (VP). The expression of YAP in skin lesions and infiltrating T cell subsets was detected using immunohistochemistry and double immunofluorescence staining, respectively.ResultsWe found differing degrees of Th1/Th2/Th17/Treg imbalance in acute and chronic AD. YAP expression was downregulated in Treg cells and upregulated in Th17 cells; YAP expression was downregulated in the AD epidermis. After YAP overexpression, the proportion of both Th17 and the Treg cells differentiated from mouse spleen mononuclear cells increased. There was an opposite trend after YAP inhibition. The proliferation and migration decreased and apoptosis increased after YAP inhibition in HaCaT cells.ConclusionChange of YAP expression may cause T cell imbalance and hamper the healing of the epidermis in AD.     

CD4+ T cells producing interleukin (IL)‐17, IL‐22 and interferon‐γ are major effector T cells in nickel allergy

Background It has been suggested that interleukin (IL)‐17 and IL‐22 play important roles in the elicitation of human allergic contact dermatitis; however, the frequencies of T cell subtypes producing IL‐17 and IL‐22 in human allergic contact dermatitis are unknown. Objectives To determine the frequencies of CD4⁺, CD8⁺ and γδ T cells producing IL‐17, IL‐22 and interferon (IFN)‐γ in the blood and skin from nickel‐allergic patients. Patients/materials/methods Blood samples were collected from 14 patients and 17 controls, and analysed by flow cytometry. Biopsies were taken from 5 patients and 6 controls, and analysed by immunohistochemistry and flow cytometry of skin lymphocytes. Results We found an increased frequency of γδ T cells in the blood, but no differences in the distribution of cytokine‐producing CLA⁺ T cell subtypes in nickel‐allergic patients as compared with controls. In nickel‐allergic patients, there was massive cellular infiltration dominated by CD4⁺ T cells producing IL‐17, IL‐22 and IFN‐γ in nickel‐challenged skin but not in vehicle‐challenged skin. Conclusion CD4⁺ T cells producing IL‐17, IL‐22 and IFN‐γ are important effector cells in the eczematous reactions of nickel‐induced allergic contact dermatitis in humans.     

Interleukin‐21 receptor signalling is not critically required for imiquimod‐induced psoriasiform dermatitis in mice

Psoriasis is largely mediated by interleukin (IL)‐23/T helper (Th) 17 axis, and IL‐21 is a pleiotropic cytokine expressed by Th17 cells. Despite previously reported possible pathogenic roles of IL‐21 in human psoriasis, we found that IL‐21 receptor (IL‐21R) signalling was not crucial for imiquimod‐induced psoriatic inflammation, using IL‐21R^?/? mice. The severity of imiquimod‐induced psoriatic manifestation and pro‐inflammatory Th17 cytokine levels, IL‐17A‐producing γδ T cells and CD4+ T cells, and in vitro IL‐17A production by γδ T cells after IL‐23 stimulation was comparable between wild‐type and IL‐21R^?/? mice. Collectively, IL‐21R signalling was not critically involved in IMQ‐induced psoriatic inflammation despite an increased IL‐21 expression in the IMQ‐treated mouse skin. Our data may represent the significant differences between human psoriasis and murine psoriasis model, and further studies using other models will be required to elucidate the role of IL‐21 in psoriasis pathogenesis.     

Vitamin D modulates the allergic phenotype of dendritic cells in children with atopic dermatitis

Vitamin D (VD) deficiency has been associated with increased incidence and severity of atopic dermatitis (AD), but the mechanisms through which VD may ameliorate AD are unclear. We compared the phenotypic characteristics of circulating myeloid and plasmacytoid dendritic cells (mDCs and pDCs, respectively) of children with AD vs healthy controls (HC) and evaluated if VD can modulate the allergic phenotype of circulating DCs in AD patients. Although there was no difference in frequency of circulating DCs between groups, among children with AD there was an inverse correlation between SCORAD and circulating total DCs and mDCs. In AD, serum IgE concentration correlated with FcεRI and surface‐bound IgE expression on mDCs and pDCs; pDCs expressing FcεRI and IgE were significantly increased compared to HC. Ex vivo, 1,25(OH)₂D₃ significantly decreased FcεRI expression on mDCs and surface‐bound IgE on mDCs and pDCs. Oral VD supplementation reduced expression of surface‐bound IgE on pDCs in children with AD. In summary, VD decreases the allergic phenotype of circulating DCs in children with AD, a potential mechanism for how VD supplementation may improve AD severity. Future studies are needed to further assess the role of VD supplementation as an immunomodulatory therapy for AD.     

Cutaneous T‐cell lymphoma cells are sensitive to rapamycin

Please cite this paper as: Cutaneous T‐cell lymphoma cells are sensitive to rapamycin. Experimental Dermatology 2010; 19 : 800–805. Abstract: Cutaneous T‐cell lymphomas (CTCL) are characterised by clonal expansion of helper T lymphocytes that infiltrate the skin. Only a small number of cell lines exist to study cellular pathways leading to T‐cell transformation and to identify new targets for intervention. We wanted to investigate the inhibition of mTOR as a possible therapeutic target in CTCL. Primary cells of patients with Sézary syndrome (SS) and conventional CTCL cell lines were analysed. Constitutive activation of mTOR was found, and concomitantly, we could show that rapamycin, a specific inhibitor of mTOR, inhibits CTCL cell growth in vitro by induction of cell cycle arrest. Using a previously established animal model for CTCL, we additionally observed upon rapamycin treatment tumor growth inhibition in vivo. In summary, primary cells from patients with SS as well as CTCL cell lines allowed us to identify mTOR as an important target for intervention.     

DAMP molecules S100A9 and S100A8 activated by IL‐17A and house‐dust mites are increased in atopic dermatitis

S100A9 and S100A8 are called damage‐associated molecular pattern (DAMP) molecules because of their pro‐inflammatory properties. Few studies have evaluated S100A9 and S100A8 function as DAMP molecules in atopic dermatitis (AD). We investigated how house‐dust mites affect S100A9 and S100A8 expression in Th2 cytokine‐ and Th17 cytokine‐treated keratinocytes, and how secretion of these molecules affects keratinocyte‐derived cytokines. Finally, we evaluated expression of these DAMP molecules in AD patients. S100A9 expression and S100A8 expression were strongly induced in IL‐17A‐ and Dermatophagoides (D.) farinae‐treated keratinocytes, respectively. Furthermore, co‐treatment with D. farinae and IL‐17A strongly increased expression of S100A9 and S100A8 compared with D. farinae‐Th2 cytokine co‐treatment. The IL‐33 mRNA level increased in a dose‐dependent manner in S100A9‐treated keratinocytes, but TSLP expression did not change. S100A8/A9 levels were also higher in the lesional skin and serum of AD patients, and correlated with disease severity. Taken together, S100A9 and S100A8 may be involved in inducing DAMP‐mediated inflammation in AD triggered by IL‐17A and house‐dust mites.     

Naïve CD4+ T cells from patients with atopic dermatitis show an aberrant maturation towards IL-4-producing skin-homing CLA+ cells

Abstract: Overproduction of interleukin‐4 (IL‐4) has been reported in lesional and in peripheral T cells from patients with atopic dermatitis (AD). It is not clear whether the development of IL‐4‐producing T helper type 2 (Th2) cells from naïve precursors is an intrinsic phenomenon of T cells or whether other, extrinsic factors play a significant role. To analyze these alternatives, we investigated the IL‐4 production of effector T cells generated in vitro from highly purified CD4+ CD45RA+ naïve T cells in the absence of signals derived from antigen‐presenting cells. Effector T cells generated from naïve precursors from both AD and healthy donors produced comparable amounts of IL‐4 after restimulation. Priming in the presence of exogenous IL‐4 enhanced the production of IL‐4 while neutralizing endogenously produced IL‐4 abolished IL‐4 production similarly in atopic and healthy T cells. A subset of effector T cells acquired the expression of the cutaneous lymphocyte antigen (CLA). The frequency of CLA+ T cells was not different between atopic and healthy donors. CLA+ T cells, differentiated from naïve atopic, but not healthy T cells, showed a preferential Th2 cytokine profile as assessed by intracellular cytokine staining. Also effector T cells derived from atopic patients without dermatitis tended to show this imbalance, although it was not significantly different to healthy controls. This Th2 cytokine profile did not develop when naïve T cells were cultured in the presence of IL‐12. In conclusion, high IL‐4 production in developing T cells from AD patients was associated with CLA expression, the net IL‐4 production of all effector CD4+ T cells, however, was similar to IL‐4 production by T cells from healthy donors.     

Increased circulating Th17 frequencies and serum IL‐22 levels in patients with acute generalized exanthematous pustulosis

Background/Objective Acute generalized exanthematous pustulosis (AGEP) is a diffuse pustular disorder that usually begins in intertriginous folds with widespread erythema. The causes in the majority of the cases are drugs. T cells and interleukin (IL)‐8 play roles in the development of AGEP, but the mechanism remains to be elucidated. We investigated the involvement of Th17 cells and their cytokine IL‐22 in the pathogenesis. Methods Three patients with AGEP were enrolled in this study. The percentages of IL‐17⁺ Th17 cells, interferon γ⁺ T cells and IL‐4⁺ T cells were measured in the patients’ peripheral blood lymphocytes by intracellular cytokine staining and flow cytometry. The concentration of IL‐22 in the sera was measured by enzyme‐linked immunosorbent assay. Results The percentages of Th17 cells were markedly higher in all three patients than healthy control individuals. The frequencies of interferon γ⁺ T cells were slightly high in the patients compared with the control, and there was no definite tendency in IL‐4⁺ T‐cell frequencies. The concentration of IL‐22 was remarkably high in all patients when compared with normal subjects with levels under detection. Conclusion Th17 cells and their produced cytokine IL‐22 were elevated in the peripheral blood of patients with AGEP. As IL‐17 and IL‐22 cooperatively stimulate keratinocytes to produce IL‐8, IL‐8 may contribute to the accumulation of neutrophils in the lesional epidermis of AGEP.     

Role of IL‐10 and TGF‐β in melanoma

IL‐10 and TGF‐β are immunosuppressive cytokines expressed in tumors including melanoma and, therefore, deemed major cause for failing antitumor immune responses. Re‐evaluating their role, we compared their expression by quantitative RT‐PCR in melanoma and skin of healthy individuals, tested their induction in dendritic cells and T cells co‐cultured with tumor cells, and their effects on the immune cells. Both cytokines as well as their receptors were expressed in melanoma at significantly lower levels than in healthy skin. Consequently, the expressions of IL‐10‐responsive SOCS‐3 and TGF‐β‐responsive Smad‐7 were low in tumors but high in healthy skin. T cells co‐cultured with tumor cells developed an anergic state without increased IL‐10 or TGF‐β expression. In vitro tumor‐induced immature dendritic cells produced high IL‐10 levels and less efficiently induced T‐cell proliferation. Nonetheless, they could be induced to mature, and blocking IL‐10 did not alter the capacity of the resulting mature dendritic cells to stimulate T cells. Mature dendritic cells co‐cultured with tumor cells produced increased IL‐10 but decreased TGF‐β and more efficiently induced T‐cell proliferation. The lack of correlation of IL‐10 and TGF‐β with immune deficits in situ and in vitro suggests re‐evaluating their roles in cancer.