IL-17 and IL-22 mediate IL-20 subfamily cytokine production in cultured keratinocytes via increased IL-22 receptor expression

Interleukin-22: A Bridge Between Epithelial Innate Host Defense and Immune Cells

Interleukin-22 (IL-22), an IL-10 family cytokine, is produced by various leukocytes. The receptor of IL-22, however, is preferentially detected on peripheral tissue epithelial cells. IL-22 functions as a unique messenger from immune system to tissue epithelial cells and to regulate homeostasis of epithelia. IL-22 is able to directly enhance antimicrobial defense mechanisms in epithelial cells and to facilitate epithelial barrier repair and wound healing process. It, therefore, possesses an irreplaceable role in host defense against certain pathogens that specifically invade epithelial cells. In addition, IL-22 can help to preserve the integrity and homeostasis of various epithelial organs during infection or inflammation. The importance of its tissue-protective function is manifested in many inflammatory situations such as inflammatory bowel diseases (IBD) and hepatitis. On the other hand, as a cytokine, IL-22 is capable of induction of proinflammatory responses, especially in synergy with other cytokines. Consequently, IL-22 contributes to pathogenesis of certain inflammatory diseases for example psoriasis.

Decreased interleukin-20 level in patients with systemic sclerosis: are they related with angiogenesis?

In this study, we aimed to evaluate the relation between angiogenesis indicators and T helper 17 cytokine group in patients with systemic sclerosis (SSc) which is a disease characterized by impaired angiogenesis and autoimmune response. In our study, patients with SSc are compared with patients with primary Raynaud's phenomenon (RP) and healthy controls. Forty SSc patients, 18 primary RP cases, and 20 healthy controls were included in our study. The demographic and clinical features of patients with SSc were recorded. The serum levels of vascular endothelial growth factor (VEGF), vascular endothelial (VE)-cadherin, interleukin (IL)-20, IL-22, and IL-23 were assessed. In the SSc group, IL-20 level was significantly lower than in both primary RP group and controls (p values <0.001). VE-cadherin level in SSc was significantly higher than in primary RP (p = 0.016). The IL-22 and IL-23 and VEGF levels of SSc, primary RP, and control groups were similar (p values >0.05). In SSc patients, IL-23 correlated negatively with VEGF (r = -0.36, p = 0.025) and positively with VE-cadherin (r = 0.55, p < 0.001). IL-20 levels in SSc patients correlated with disease duration (r = 0.32, p = 0.044). SSc patients with limited involvement had significantly higher VE-cadherin levels than SSc patients with diffuse involvement (p = 0.044). We observed that IL-20 which is an IL-10 group angiogenesis indicator was observed to be suppressed in SSc, suggesting abnormal angiogenesis.

Serum levels of selected Th17 and Th22 cytokines in psoriatic patients

INTRODUCTION

Psoriasis is a T cell-mediated inflammatory disease in which pathogenesis T helper (Th) lymphocytes (Th1, Th17, and Th22) play an important role. The aim of the study was to assess the serum levels of some cytokines involved in the Th17 and Th22 responses in psoriatic patients.

MATERIAL AND METHODS

The study comprised 60 psoriatic patients and 30 healthy controls. In the serum collected from psoriatic patients and healthy controls, the concentrations of IL-6, IL-12, IL-17, IL-20, IL-22, and IL-23 were examined with ELISA kits. Severity of psoriatic skin lesions was assessed by means of PASI, BSA, and PGA scores.

RESULTS

IL-6, IL-20, and IL-22 concentrations were significantly higher in psoriatic patients in comparison with the control group. The positive correlations between the concentrations of IL-22 and IL-20 and severity of psoriasis assessed with PASI and BSA scores as well as IL-17 and PASI score were found. There was also a positive correlation between IL-23 and IL-17 concentrations.

CONCLUSIONS

Results of the conducted studies suggest that Th22 response may contribute to the skin and systemic inflammatory disease in psoriasis. It seems that early identification of soluble biomarkers and initiation of well-matched treatment may prevent exacerbation and progression of psoriasis.

The role of IL-22 and Th22 cells in human skin diseases

Interleukin (IL)-22 is a cytokine that is involved in the modulation of tissue responses during inflammation. It is produced by immune cell subsets such as T cells, while the expression of its receptor is restricted to cells of non-hematopoietic origin, particularly epithelial cells. In the skin, IL-22 induces keratinocyte proliferation and epidermal hyperplasia, inhibits terminal differentiation of keratinocytes, and promotes the production of antimicrobial proteins. Although IL-22 was initially thought to be produced by T helper (Th)17 cells, IL-22 production can also occur in an apparently unique subset of cells, Th22 cells, which lack the ability to produce IL-17 and interferon-γ. Of note, Th22 cells, which express the skin homing chemokine receptors CCR4 and CCR10, reside in the normal skin and are enriched in the lesional skin of inflammatory skin diseases, indicating the importance of IL-22 in skin homeostasis and pathogenesis of skin diseases. Although a critical role of IL-22 was initially highlighted in psoriasis, a growing body of evidence indicates that this cytokine also plays a role in atopic dermatitis and other inflammatory skin diseases. Moreover, emerging experimental data suggest that IL-22 also participates in the pathophysiology of malignancies of the skin. In this review, recent findings regarding the expression, regulation, and function of the IL-22 pathway in various human skin diseases will be discussed. Considering the strong association between excess activation of the IL-22/Th22 pathway and human skin diseases, targeting this pathway may provide promising new therapeutic approaches.

Serum interleukin-22 and vascular endothelial growth factor serve as sensitive biomarkers but not as predictors of therapeutic response to biologics in patients with psoriasis

The T-helper (Th)17 cell plays a crucial role in the pathogenesis of psoriasis, and several biological therapies have shown to be highly efficient in the treatment. However, some patients respond poorly to these therapies and may even develop paradoxical adverse effects. To evaluate the significance of serum immunological factors or circulating competent cells for biomarkers or predictors to biological therapies, we retrospectively analyzed 28 patients with psoriasis (19 psoriasis vulgaris, three pustular psoriasis and six psoriasis arthropathica). The numbers of patients treated with each agents were 16 for ustekinumab, six for adalimumab and six for infliximab. Patients were classified into three types according to the responsiveness: 13 patients were high-responders showing a 75% or more reduction of Psoriasis Area and Severity Index (PASI); 10 patients were moderate-responders showing PASI reduction of less than 75%; and five patients were non-responders showing PASI elevation. During the treatments, serum levels of interleukin (IL)-22 and vascular endothelial growth factor (VEGH) [corrected] were monitored. At baseline, serum IL-22 levels were significantly higher in the psoriatic patients than the normal controls. Both serum IL-22 and VEGF levels significantly correlated with PASI. After the treatment, the high-responders showed significant decreases in serum IL-22 and VEGF. On the other hand, serum IL-22 levels in the non-responders were elevated. However, the baseline levels of serum IL-22 and VEGF were not significantly different between the three groups. These results suggest that serum IL-22 and VEGF levels serve as sensitive biomarkers but not as predictors of therapeutic response to biologics in patients with psoriasis.

Dissecting the psoriasis transcriptome: inflammatory- and cytokine-driven gene expression in lesions from 163 patients

BACKGROUND

Psoriasis lesions are characterized by large-scale shifts in gene expression. Mechanisms that underlie differentially expressed genes (DEGs), however, are not completely understood. We analyzed existing datasets to evaluate genome-wide expression in lesions from 163 psoriasis patients. Our aims were to identify mechanisms that drive differential expression and to characterize heterogeneity among lesions in this large sample.

RESULTS

We identified 1233 psoriasis-increased DEGs and 977 psoriasis-decreased DEGs. Increased DEGs were attributed to keratinocyte activity (56%) and infiltration of lesions by T-cells (14%) and macrophages (11%). Decreased DEGs, in contrast, were associated with adipose tissue (63%), epidermis (14%) and dermis (4%). KC/epidermis DEGs were enriched for genes induced by IL-1, IL-17A and IL-20 family cytokines, and were also disproportionately associated with AP-1 binding sites. Among all patients, 50% exhibited a heightened inflammatory signature, with increased expression of genes expressed by T-cells, monocytes and dendritic cells. 66% of patients displayed an IFN-γ-strong signature, with increased expression of genes induced by IFN-γ in addition to several other cytokines (e.g., IL-1, IL-17A and TNF). We show that such differences in gene expression can be used to differentiate between etanercept responders and non-responders.

CONCLUSIONS

Psoriasis DEGs are partly explained by shifts in the cellular composition of psoriasis lesions. Epidermal DEGs, however, may be driven by the activity of AP-1 and cellular responses to IL-1, IL-17A and IL-20 family cytokines. Among patients, we uncovered a range of inflammatory- and cytokine-associated gene expression patterns. Such patterns may provide biomarkers for predicting individual responses to biologic therapy.

Signaling via the IL-20 receptor inhibits cutaneous production of IL-1β and IL-17A to promote infection with methicillin-resistant Staphylococcus aureus

Staphylococcus aureus causes most infections of human skin and soft tissue and is a major infectious cause of mortality. Host defense mechanisms against S. aureus are incompletely understood. Interleukin 19 (IL-19), IL-20 and IL-24 signal through type I and type II IL-20 receptors and are associated with inflammatory skin diseases such as psoriasis and atopic dermatitis. We found here that those cytokines promoted cutaneous infection with S. aureus in mice by downregulating IL-1β- and IL-17A-dependent pathways. We noted similar effects of those cytokines in human keratinocytes after exposure to S. aureus, and antibody blockade of the IL-20 receptor improved outcomes in infected mice. Our findings identify an immunosuppressive role for IL-19, IL-20 and IL-24 during infection that could be therapeutically targeted to alter susceptibility to infection.

IL-17 in psoriasis: implications for therapy and cardiovascular co-morbidities

Psoriasis is a prevalent, chronic inflammatory disease of the skin mediated by cross-talk occurring between epidermal keratinocytes, dermal vascular cells and immunocytes, including activated antigen presenting cells (APCs), monocytes/macrophages, and Th1 and Th17 cells. Increased proliferation of keratinocytes and endothelial cells in conjunction with immune cell infiltration leads to the distinct epidermal and vascular hyperplasia that is characteristic of lesional psoriatic skin. Interaction of activated T cells with monocytes/macrophages occurs via the Th17/IL-23 axis and is crucial for maintaining the chronic inflammation. Recent epidemiological evidence has demonstrated that psoriasis patients have an increased risk of developing and dying of cardiovascular disease. Similar pathology between psoriasis and cardiovascular disease, including involvement of key immunologic cell populations together with release of common inflammatory mediators such as IL-17A suggest a mechanistic link between the two diseases. This review will focus on concepts critical to psoriasis pathogenesis, systemic manifestations of psoriasis, the role of IL-17 in psoriasis and cardiovascular disease and the potential role for IL-17 in mediating cardiovascular co-morbidities in psoriasis patients.

Photo(chemo)therapy reduces circulating Th17 cells and restores circulating regulatory T cells in psoriasis

Background

Photo(chemo)therapy is widely used to treat psoriasis, the pathogenesis of which might be caused by an imbalance of Th17 cells/regulatory T cells (Treg). In the present study, we evaluated the effects of photo(chemo)therapy on the Th17/Treg balance and Treg function.

Methods

Peripheral blood was obtained from psoriasis patients treated with bath-psoralen ultraviolet A (UVA, n = 50) or narrowband ultraviolet B (UVB, n = 18), and age-matched healthy volunteers (n = 20). CD3⁺CD4⁺IL-17A⁺ or CD4⁺CD25⁺Foxp3⁺cells were analyzed to estimate Th17 or Treg number by fluorescence–activated cell sorting. Moreover, CD4⁺ CD25⁻ T cells from patients treated with PUVA(n = 14) were incubated in CFSE and activated with or without CD4⁺ CD25⁺T cells, and the suppressive function of CD4⁺ CD25⁺T cells were analyzed.

Results

Photo(chemo)therapy significantly reduced Th17 levels from 5.66±3.15% to 2.96±2.89% in patients with increased Th17 (Th17/CD4>3.01% [mean+SD of controls]). In contrast, photo(chemo)therapy significantly increased Treg levels from 2.77±0.75 to 3.40±1.88% in patients with less than 4.07% Treg level, defined as the mean of controls. Furthermore, while Treg suppressed the CD4⁺CD25⁻ T cell proliferation to a greater extent in controls (Treg Functional Ratio 94.4±4.28%) than in patients (70.3±25.1%), PUVA significantly increased Treg Functional Ratio to 88.1±6.47%. Th17 levels in severe patients (>30 PASI) were significantly higher as compared to controls. Th17 levels that were left after treatment in the patients not achieving PASI 50 (3.78±4.18%) were significantly higher than those in the patients achieving PASI 75 (1.83±1.87%). Treg levels in patients achieving PASI 90 (4.89±1.70%) were significantly higher than those in the patients not achieving PASI 90 (3.90±1.66%). Treg levels prior to treatment with Th17 high decreased group (5.16±2.20%) was significantly higher than that with Th17 high increased group (3.33±1.39%).

Conclusion

These findings indicate that Treg is dysfunctional in psoriasis patients, and photochemotherapy restores those dysfunctional Treg. Photo(chemo)therapy resolved the Th17/Treg imbalance in patients with psoriasis.

Emerging therapies for the treatment of psoriasis

Psoriasis is an immune-mediated disease that affects 1%–2% of the European and North American population. While topical agents such as corticosteroids and vitamin D derivatives are prescribed for mild disease, they are generally unable to adequately control patients with more severe disease. Over the past decade, research into the immunopathogenesis of psoriasis, including investigations into the role of tumor necrosis factor-alpha and more recently interleukins (IL) 12/23, has led to the advent of targeted biologic therapies based on the central role of a new subset of T cells, Th17. Because of their increased specificity, biologic agents have revolutionized short- to medium-term treatment outcomes and safety profiles for moderate to severe disease over previously gold standard systemic agents. The immunopathogenesis of the disease is still a focus for researchers and novel targets for future agents are being discovered and investigated in clinical trials. In particular, specifically targeting the IL-23/Th17 pathway has given rise to IL-23p19 and IL-17 antagonists, both of which have shown significant promise in clinical trials. IL-22 is involved in keratinocyte proliferation and is being studied as a treatment target for psoriasis. New small molecule oral agents, including Janus kinase and phosphodiesterase inhibitors are currently in phase 2 and 3 clinical trials.

Etanercept suppresses regenerative hyperplasia in psoriasis by acutely downregulating epidermal expression of interleukin (IL)-19, IL-20 and IL-24

BACKGROUND

Psoriasis is a Th17/Th1-mediated skin disease that often responds to antitumour necrosis factor (TNF)-α therapies, such as etanercept.

OBJECTIVES

To better define mechanisms by which etanercept improves psoriasis and to gain insight into disease pathogenesis.

METHODS

We investigated the early biochemical and cellular effects of etanercept on skin lesions in responder patients prior to substantial clinical improvement (≤ 4 weeks).

RESULTS

By 1 week, etanercept acutely suppressed gene expression of the interleukin (IL)-20 subfamily of cytokines (IL-19, IL-20, IL-24), which were found to be predominantly epidermis-derived and which are implicated in stimulating epidermal hyperplasia. Additionally, by 1 week of therapy, suppression of other keratinocyte-derived products (chemokines, antimicrobial proteins) occurred, while suppression of epidermal regenerative hyperplasia occurred within 1-3 weeks. Th17 elements (IL-23p19, IL-12p40, IL-17A, IL-22) were suppressed by 3-4 weeks. In vitro, TNF-α and IL-17A coordinately stimulated the expression of the IL-20 subfamily in normal keratinocytes.

CONCLUSIONS

Based on the rapid suppression of regenerative hyperplasia, chemokines and other keratinocyte-derived products, including the IL-20 subfamily, we propose that epidermal activation is a very early target of etanercept. As many of these keratinocyte markers are stimulated by TNF-α, their rapid downregulation is likely to reflect etanercept's antagonism of TNF-α. Additionally, decreased epidermal hyperplasia might result specifically from acute suppression of the IL-20 subfamily, which is also a likely consequence of etanercept's antagonism of TNF-α. Thus, the IL-20 subfamily has potential importance in the pathogenesis of psoriasis and therapeutic response to etanercept.

Expression of IL-20 in synovium and lesional skin of patients with psoriatic arthritis: differential response to alefacept treatment

Introduction

Psoriatic arthritis (PsA) is an inflammatory joint disease associated with psoriasis. Alefacept (a lymphocyte function-associated antigen (LFA)-3 Ig fusion protein that binds to CD2 and functions as an antagonist to T-cell activation) has been shown to result in improvement in psoriasis but has limited effectiveness in PsA. Interleukin-20 (IL-20) is a key proinflammatory cytokine involved in the pathogenesis of psoriasis. The effects of alefacept treatment on IL-20 expression in the synovium of patients with psoriasis and PsA are currently unknown.

Methods

Eleven patients with active PsA and chronic plaque psoriasis were treated with alefacept (7.5 mg per week for 12 weeks) in an open-label study. Skin biopsies were taken before and after 1 and 6 weeks, whereas synovial biopsies were obtained before and 4 and 12 weeks after treatment. Synovial biopsies from patients with rheumatoid arthritis (RA) (n = 10) were used as disease controls. Immunohistochemical analysis was performed to detect IL-20 expression, and stained synovial tissue sections were evaluated with digital image analysis. Double staining was performed with IL-20 and CD68 (macrophages), and conversely with CD55 (fibroblast-like synoviocytes, FLSs) to determine the phenotype of IL-20-positive cells in PsA synovium. IL-20 expression in skin sections (n = 6) was analyzed semiquantitatively.

Results

IL-20 was abundantly expressed in both PsA and RA synovial tissues. In inflamed PsA synovium, CD68⁺ macrophages and CD55⁺ FLSs coexpressed IL-20, and its expression correlated with the numbers of FLSs. IL-20 expression in lesional skin of PsA patients decreased significantly (P = 0.04) 6 weeks after treatment and correlated positively with the Psoriasis Area and Severity Index (PASI). IL-20 expression in PsA synovium was not affected by alefacept.

Conclusions

Conceivably, the relatively limited effectiveness of alefacept in PsA patients (compared with anti-tumor necrosis factor (TNF) therapy) might be explained in part by persistent FLS-derived IL-20 expression.

Janus-like effects of type I interferon in autoimmune diseases

In multiple sclerosis, type I interferon (IFN) is considered immune-modulatory, and recombinant forms of IFN-β are the most prescribed treatment for this disease. This is in contrast to most other autoimmune disorders, because type I IFN contributes to the pathologies. Even within the relapsing-remitting multiple sclerosis (RRMS) population, 30-50% of MS patients are non-responsive to this treatment, and it consistently worsens neuromyelitis optica, a disease similar to RRMS. In this article, we discuss the recent advances in the field of autoimmunity and introduce the theory explain how type I IFNs can be pro-inflammatory in disease that is predominantly driven by a Th17 response and are therapeutic when disease is predominantly Th1.

IL-17 downregulates filaggrin and affects keratinocyte expression of genes associated with cellular adhesion

Atopic eczema and psoriasis are common skin diseases. While it is well established that the pathogenesis of these diseases varies, both are characterized by impairment in epidermal barrier function and abnormal IL-17 expression in the skin and peripheral blood. Recent findings indicated that filaggrin is essential during barrier formation and its insufficiency underlies the pathogenesis of atopic eczema. Filaggrin downregulation has also been reported in psoriasis. It is clear that Th1/Th2 bias influences expression of the protein, but an analysis of the effects of interleukin-17 (IL-17) on the expression of the protein and profilaggrin-processing enzymes has not yet been reported. In addition, the effect of the cytokine on components of functional epidermal barrier, tight junctions and adhesion/desmosomal proteins, has not been elucidated. Keratinocytes were exposed to interleukin-17A, and microarray analysis was performed. Filaggrin protein level was assessed by western blot. We have observed a significant decrease in profilaggrin mRNA level in interleukin-17A-exposed cultures (P = 0.008). Expression of processing enzymes was also altered, indicating an indirect effect of the cytokine on filaggrin production/degradation. Moreover, expression of many genes involved in cellular adhesion was also decreased. A significant downregulation of filaggrin at the protein level was detected by western blot in immortal and primary keratinocytes. Gene ontology analysis indicated changes in keratinization, epidermal differentiation and formation of the cornified envelope. We conclude that IL-17A downregulates the expression of filaggrin and genes important for cellular adhesion which could affect epidermal barrier formation. This effect potentially contributes to barrier dysfunction and could become a possible therapeutic target.

Interleukin-22: implications for liver ischemia-reperfusion injury

BACKGROUND

Ischemia-reperfusion injury (IRI) is common in general surgery and organ transplantation, and in the case of liver, it triggers proinflammatory innate immune cascade and hepatic necrosis, leading to increased incidence of early and late organ rejection. Interleukin (IL)-22, an inducible cytokine of T-cell origin and a member of the IL-10 superfamily, acts on target tissues through IL-22 receptor (IL-22R1).

METHODS

Partial hepatic warm ischemia was induced in C57Bl/6 wild-type (WT) and type 1 interferon receptor-deficient (KO) mice for 90 min followed by 6 to 24 hr of reperfusion. WT mice were treated at 30 min before the ischemia insult with recombinant IL-22 or anti-IL-22 neutralizing antibody; phosphate-buffered saline and IgG served as respective controls.

RESULTS

IL-22 was detected at 24 hr but not 6 hr of liver IRI. The expression of IL-22R1 was increased by 6 hr of reperfusion in WT but not type 1 interferon receptor KO mice that were protected from IRI. Treatment of WT mice with recombinant IL-22 decreased serum aspartate aminotransferase levels, ameliorated cardinal histological features of IR damage (Suzuki's score) and diminished leukocyte sequestration, along with the expression of IL-22R1 and pro-inflammatory cytokines. IL-22 antibody did not appreciably affect IRI but increased IL-22R1 transcription in the liver. Administration of IL-22 protein exerted hepatoprotection by STAT3 activation.

CONCLUSIONS

This is the first report investigating immune modulation by T-cell-derived IL-22 in liver injury caused by warm ischemia and reperfusion. Treatment with IL-22 protein may represent a novel therapeutic strategy to prevent liver IRI in transplant recipients.

IL-22, but not IL-17, dominant environment in cutaneous T-cell lymphoma

PURPOSE

Both patients with cutaneous T-cell lymphoma (CTCL) and those with atopic dermatitis (AD) have pruritus, T(H)2-biased T cells, and a tendency to have bacterial infections, suggesting a common pathologic basis for these two diseases. Recently, interleukin (IL)-22-producing T cells were reported in skin of patients with AD. In this study, we investigated expression levels of T(H)22- and T(H)17-related molecules in lesional skin and sera isolated from patients with CTCL.

EXPERIMENTAL DESIGN

Skin biopsies and sera were collected from patients with CTCL or psoriasis and from healthy volunteers. Protein and mRNA expression levels of IL-22, IL-17A, IL-17F, IL-23p19, IL-10, IL-4, CCL20, CCR6, IL-8, and IL-20 were examined in lesional tissue and a subset of these molecules in sera. Phosphorylation of STAT3 was also assessed in lesional skin of CTCL and psoriasis by immunohistochemistry.

RESULTS

IL-22, IL-10, IL-4, CCL20, and CCR6 mRNA and protein levels, but not IL-17A, IL-17F, IL-23p19, IL-8, or IL-20, were significantly elevated in lesional skin of CTCL. Phosphorylation of STAT3 was detected in epidermis of CTCL skin. Moreover, serum IL-22, IL-10, and CCL20 levels were increased in CTCL and correlated with disease severity.

CONCLUSIONS

Our results suggest that IL-22 is important in establishing the tumor microenvironment for CTCL. Enhanced expression of CCL20 may explain epidermal hyperplasia and migration of CCR6(+) cells, such as Langerhans cells, into lesional skin. Relatively low expression of IL-17 may explain the lack of neutrophils in lesions of CTCL, which correlates with bacterial infections that commonly occur in skin affected by CTCL.

Interleukin-19: a constituent of the regulome that controls antigen presenting cells in the lungs and airway responses to microbial products

BACKGROUND

Interleukin (IL)-19 has been reported to enhance chronic inflammatory diseases such as asthma but the in vivo mechanism is incompletely understood. Because IL-19 is produced by and regulates cells of the monocyte lineage, our studies focused on in vivo responses of CD11c positive (CD11c+) alveolar macrophages and lung dendritic cells.

METHODOLOGY/PRINCIPAL FINDINGS

IL-19-deficient (IL-19-/-) mice were studied at baseline (naïve) and following intranasal challenge with microbial products, or recombinant cytokines. Naïve IL-19-/- mixed background mice had a decreased percentage of CD11c+ cells in the bronchoalveolar-lavage (BAL) due to the deficiency in IL-19 and a trait inherited from the 129-mouse strain. BAL CD11c+ cells from fully backcrossed IL-19-/- BALB/c or C57BL/6 mice expressed significantly less Major Histocompatibility Complex class II (MHCII) in response to intranasal administration of lipopolysaccharide, Aspergillus antigen, or IL-13, a pro-allergic cytokine. Neurogenic-locus-notch-homolog-protein-2 (Notch2) expression by lung monocytes, the precursors of BAL CD11c+ cells, was dysregulated: extracellular Notch2 was significantly decreased, transmembrane/intracellular Notch2 was significantly increased in IL-19-/- mice relative to wild type. Instillation of recombinant IL-19 increased extracellular Notch2 expression and dendritic cells cultured from bone marrow cells in the presence of IL-19 showed upregulated extracellular Notch2. The CD205 positive subset among the CD11c+ cells was 3-5-fold decreased in the airways and lungs of naïve IL-19-/- mice relative to wild type. Airway inflammation and histological changes in the lungs were ameliorated in IL-19-/- mice challenged with Aspergillus antigen that induces T lymphocyte-dependent allergic inflammation but not in IL-19-/- mice challenged with lipopolysaccharide or IL-13.

CONCLUSIONS/SIGNIFICANCE

Because MHCII is the molecular platform that displays peptides to T lymphocytes and Notch2 determines cell fate decisions, our studies suggest that endogenous IL-19 is a constituent of the regulome that controls both processes in vivo.

[IL-23 and Th17 cells in infections and psoriasis]

IL-23 is produced by dendritic cells, and other antigen presenting cells. IL-23 is required for the induction, expansion, maintenance and downstream effector functions of Th17 cells. Th17 cells upregulate neutrophil chemokines, antimicrobial peptides, and other pro-inflammatory cytokines. The lack of Th17 cells results in susceptibility to Candida, Streptococcal and Staphylococcal infections. On the contrary, the excess of Th17 cells induce various autoimmune diseases such as psoriasis. Several studies revealed that infections were more common in psoriatics than in healthy individuals. Superantigens released by microorganisms have been suggested as exogenous triggers that stimulate T cells to initiate psoriasis. Understanding the Th17 responses and their interactions with the immune system will likely provide crucial insights in the host defense and autoimmune diseases like psoriasis, and this will provide new tools for the development of effective immunomodulatory treatment strategies for infectious diseases and autoimmune diseases.

Regulation and functions of the IL-10 family of cytokines in inflammation and disease

The IL-10 family of cytokines consists of nine members: IL-10, IL-19, IL-20, IL-22, IL-24, IL-26, and the more distantly related IL-28A, IL-28B, and IL-29. Evolutionarily, IL-10 family cytokines emerged before the adaptive immune response. These cytokines elicit diverse host defense mechanisms, especially from epithelial cells, during various infections. IL-10 family cytokines are essential for maintaining the integrity and homeostasis of tissue epithelial layers. Members of this family can promote innate immune responses from tissue epithelia to limit the damage caused by viral and bacterial infections. These cytokines can also facilitate the tissue-healing process in injuries caused by infection or inflammation. Finally, IL-10 itself can repress proinflammatory responses and limit unnecessary tissue disruptions caused by inflammation. Thus, IL-10 family cytokines have indispensable functions in many infectious and inflammatory diseases.

The effects of Th17 cytokines on the inflammatory mediator production and barrier function of ARPE-19 cells

Th17 cells have emerged as a key factor in the pathogenesis of uveitis as well as other autoimmune disorders. They secrete a number of cytokines including IL-17A, IL-17F and IL-22 and until now the effects of these cytokines on resident cells of the eye were not yet clear. The purpose of this study was to investigate the effects of Interleukin (IL)-17A, IL-17F and IL-22 on the production of inflammatory mediators and barrier function of retinal pigment epithelium cells. We showed that ARPE-19 cells, a spontaneously arisen cell line of retinal pigment epithelium (RPE), constitutively expressed IL-17RC and IL-22R, but not IL-17RA. IL-17A significantly enhanced the production of CXCL8, CCL2, CCL20 and IL-6 by these cells. IL-17F had a similar effect on the production of CXCL8, CCL2 and IL-6 by ARPE-19 cells, but did not influence the expression of CCL20. Both IL-17A and IL-17F significantly decreased the transepithelial electrical resistance (TER) of the ARPE-19 monolayer and increased the diffusion rate of fluorescein isothiocyanate (FITC)-dextran. They also disrupted the distribution of the junction proteins zonula occludens (ZO)-1 and occludin at the interface of adjacent cells. IL-22 did not have a detectable effect on the production of the tested inflammatory mediators by ARPE-19 cells, TER of the ARPE-19 monolayer, the diffusion rate of FITC-dextran or the distribution of ZO-1 and occludin. This study demonstrates that IL-17A and IL-17F, but not IL-22, significantly promoted ARPE-19 cells to secrete inflammatory mediators and compromised the ARPE-19 monolayer barrier function in association with a disrupted distribution of ZO-1 and occludin. These results suggest that both IL-17A and IL-17F may play a role in posterior segment inflammation of the eye.

Antimicrobial peptides in healthy skin and atopic dermatitis

Antimicrobial Peptides and Proteins (AMPs) represent effector molecules of the innate defense system in all organisms. AMPs are either constitutively or inducibly produced mainly by various epithelial cells, including keratinocytes. This report reviews our current knowledge about the major yet known keratinocyte-derived AMPs, its role in healthy skin and atopic dermatitis.

IL-20: biological functions mediated through two types of receptor complexes

IL-20 was discovered 10 years ago as a new member of the IL-10 family of cytokines. IL-20 shares the highest amino-acid sequence identity with IL-10, IL-24 and IL-19. IL-20 is secreted by immune cells and activated epithelial cells like keratinocytes. A high expression of the corresponding IL-20 receptor chains is detected on epithelial cells. In terms of function, IL-20 might therefore mediate a crosstalk between epithelial cells and tissue-infiltrating immune cells under inflammatory conditions. Transgenic and knockout mouse models for some cytokines and receptors of the IL-10-type cytokines have provided new insights into the biology of this family. This review will focus on the biological functions of IL-20 and its receptors within the IL-10 cytokine network.

IL-10 family of cytokines

In 2001, six immune mediators (IL-10, IL-19, IL-20, IL-22, IL-24, and IL-26) were grouped into the so-called IL-10 family of cytokines based on their similarities with respect to the structure and location of their encoding genes, their primary and secondary protein structures, and the receptor complexes used. Surprisingly, despite all these similarities, IL-10 family members possess different biological functions. The currently known facts regarding the biological effects of these six immune mediators give the impression that at least IL-10, IL-20, and IL-22 play an important role in the pathogenesis of some chronic inflammatory diseases. This review provides an overview of the most important and common aspects of the IL-10 family members.

Regulation of epidermal keratinocytes by growth factors

Epidermal keratinocytes are the main component cells of the epidermis and their function is regulated by various kinds of growth factors, cytokines, and chemokines. Of these, members of the epidermal growth factor and fibroblast growth factor families, as wells as hepatocyte growth factor and insulin-like growth factor, play central roles in keratinocyte proliferation, while transforming growth factor-beta, vitamin D3, and interferon-gamma are important inhibitors of keratinocyte growth. Keratinocytes are known to produce many of the currently identified growth factors, cytokines and chemokines. Keratinocyte-derived growth factors and cytokines regulate immune and inflammatory responses, and play important roles in pathological skin conditions. This review focuses on the regulation of keratinocytes by growth factors, cytokines, and chemokines.

Interleukin-17 and its target genes: mechanisms of interleukin-17 function in disease

Interleukin-17 (IL-17) has emerged as a central player in the mammalian immune system. Although this cytokine exerts a host-defensive role in many infectious diseases, it promotes inflammatory pathology in autoimmunity and other settings. A myriad of studies have focused on how IL-17-producing cells are generated. However, the means by which IL-17 achieves its effects, either for the benefit or the detriment of the host, are due in large part to the induction of new gene expression. Whereas many IL-17 target genes are common to different disease states, in some cases the effects of IL-17 differ depending on the target cell, infectious site or pathogen. Gene products induced by IL-17 include cytokines (IL-6, granulocyte-colony-stimulating factor, tumour necrosis factor-alpha), chemokines (CXCL1, CXCL2, CCL20, among many others), inflammatory effectors (acute-phase protesins, complement) and antimicrobial proteins (defensins, mucins). Different cell types appear to respond differently to IL-17 in terms of target gene expression, with notable differences seen in mesenchymal and epithelial cells compared with cells of haematopoietic origin. Here, we summarize the major IL-17 target genes that mediate this cytokine's activities in both autoimmune and chronic diseases as well as during various types of infections.

Review of ustekinumab, an interleukin-12 and interleukin-23 inhibitor used for the treatment of plaque psoriasis

The pathogenesis of psoriasis is unknown, although it is generally accepted that this chronic inflammatory skin disorder is a complex autoimmune condition similar to other T-cell mediated disorders. Psoriasis imposes a heavy burden on the lifestyle of those affected due to the psychological, arthritic, and cutaneous morbidities; thus significant research has focused on the genetic and immunologic features of psoriasis in anticipation of more targeted, efficacious, and safe therapies. Recently, CD4(+) T helper (Th) 17 cells and interleukins (IL)-12 and -23 have been important in the pathogenesis of T-cell mediated disorders such as psoriasis and has influenced the development of medications that specifically target these key immunological players. Ustekinumab is a monoclonal antibody belonging to a newly developed class of biological, anti-cytokine medications that notably targets the p40 subunit of both IL-12 and -23, both naturally occurring proteins that are important in regulating the immune system and are understood to play a role in immune-mediated inflammatory disorders. Ustekinumab's safety and efficacy has been evaluated for the treatment of moderate-to-severe plaque psoriasis in 3 phase III clinical trials, 2 placebo-controlled (PHOENIX 1 and 2), and 1 comparator-controlled (ACCEPT) study which proved advantageous in patients who were treatment-naive, previously failed other immunosuppressive medications including cyclosporine or methotrexate, were unresponsive to phototherapy, or were unable to use or tolerate other therapies. Ustekinumab has also been investigated for other indications such as psoriatic arthritis, Crohn's disease, and relapsing/remitting multiple sclerosis. We present a concise review evaluating the evidence that supports the use of ustekinumab in the treatment of plaque psoriasis and other conditions.