Genetic Variations in Cytokines and Cytokine Receptors Associated with Psoriasis Found by Genome-Wide Association

Re-emerging concepts of immune dysregulation in autism spectrum disorders

Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by communication and social interaction deficits, and by restricted interests and stereotyped, repetitive behavior patterns. ASD has a strong genetic component and a complex architecture characterized by the interplay of rare and common genetic variants. Recently, increasing evidence suggest a significant contribution of immune system dysregulation in ASD. The present paper reviews the latest updates regarding the altered immune landscape of this complex disorder highlighting areas with potential for biomarkers discovery as well as personalization of therapeutic approaches. Cross-talk between the central nervous system and immune system has long been envisaged and recent evidence brings insights into the pathways connecting the brain to the immune system. Disturbance of cytokine levels plays an important role in the establishment of a neuroinflammatory milieu in ASD. Several other immune molecules involved in antigen presentation and inflammatory cellular phenotypes are also at play in ASD. Maternal immune activation, the presence of brain-reactive antibodies and autoimmunity are other potential prenatal and postnatal contributors to ASD pathophysiology. The molecular players involved in oxidative-stress response and mitochondrial system function, are discussed as contributors to the pro-inflammatory pattern. The gastrointestinal inflammation pathways proposed to play a role in ASD are also discussed. Moreover, the body of evidence regarding some of the genetic factors linked to the immune system dysregulation is reviewed and discussed. Last, but not least, the epigenetic traits and their interactions with the immune system are reviewed as an expanding field in ASD research. Understanding the immune-mediated pathways that influence brain development and function, metabolism, and intestinal homeostasis, may lead to the identification of robust diagnostic or predictive biomarkers for ASD individuals. Thus, novel therapeutic approaches could be developed, ultimately aiming to improve their quality of life.

Interleukin-15 in autoimmunity

Interleukin-15 (IL-15) is a member of the IL-2 family of cytokines, which use receptor complexes containing the common gamma (γ_c) chain for signaling. IL-15 plays important roles in innate and adaptative immune responses and is implicated in the pathogenesis of several immune diseases. The IL-15 receptor consists of 3 subunits namely, the ligand-binding IL-15Rα chain, the β chain (also used by IL-2) and the γ_c chain. IL-15 uses a unique signaling pathway whereby IL-15 associates with IL-15Rα during biosynthesis, and this complex is 'trans-presented' to responder cells that expresses the IL-2/15Rβγ_c receptor complex. IL-15 is subject to post-transcriptional and post-translational regulation, and evidence also suggests that IL-15 cis-signaling can occur under certain conditions. IL-15 has been implicated in the pathology of various autoimmune diseases such as rheumatoid arthritis, autoimmune diabetes, inflammatory bowel disease, coeliac disease and psoriasis. Studies with pre-clinical models have shown the beneficial effects of targeting IL-15 signaling in autoimmunity. Unlike therapies targeting other cytokines, anti-IL-15 therapies have not yet been successful in humans. We discuss the complexities of IL-15 signaling in autoimmunity and explore potential immunotherapeutic approaches to target the IL-15 signaling pathway.

Efficient synthesis of tert-butyl 3-cyano-3-cyclopropyl-2-oxopyrrolidine-4-carboxylates: Highly functionalized 2-pyrrolidinone enabling access to novel macrocyclic Tyk2 inhibitors

Herein we report an efficient method for the synthesis of a highly functionalized 2-pyrrolidinone, tert-butyl 3-cyano-3-cyclopropyl-2-oxopyrrolidine-4-carboxylate, from readily available starting materials. Utility of this compound was demonstrated in the synthesis of a novel series of macrocyclic Tyk2 inhibitors, leading to the identification of a potent and selective macrocyclic Tyk2 inhibitor (26).

Tissue-resident memory T cells and their biological characteristics in the recurrence of inflammatory skin disorders

The skin is the largest organ of the body. The establishment of immunological memory in the skin is a crucial component of the adaptive immune response. Once naive T cells are activated by antigen-presenting cells, a small fraction of them differentiate into precursor memory T cells. These precursor cells ultimately develop into several subsets of memory T cells, including central memory T (T_CM) cells, effector memory T (T_EM) cells, and tissue resident memory T (T_RM) cells. T_RM cells have a unique transcriptional profile, and their most striking characteristics are their long-term survival (longevity) and low migration in peripheral tissues, including the skin. Under physiological conditions, T_RM cells that reside in the skin can respond rapidly to pathogenic challenges. However, there is emerging evidence to support the vital role of T_RM cells in the recurrence of chronic inflammatory skin disorders, including psoriasis, vitiligo, and fixed drug eruption, under pathological or uncontrolled conditions. Clarifying and characterizing the mechanisms that are involved in skin T_RM cells will help provide promising strategies for reducing the frequency and magnitude of skin inflammation recurrence. Here, we discuss recent insights into the generation, homing, retention, and survival of T_RM cells and share our perspectives on the biological characteristics of T_RM cells in the recurrence of inflammatory skin disorders.

Association of TNF, IL12, and IL23 gene polymorphisms and psoriatic arthritis: meta-analysis

BACKGROUND

Psoriatic arthritis (PsA) is a chronic skin and joint condition that considerably affects patient quality of life. Several studies have demonstrated different associations of genetic polymorphisms in the pathogenic process of PsA. Therefore, we conducted a meta-analysis to estimate the effect of polymorphisms in the cytokines TNF, IL12B, IL23A, and IL23R on PsA risk.

METHODS

We screened 1,097 abstracts and identified 14 relevant studies published between January 2007 and December 2017. A systematic search was conducted in PubMed, Web of Knowledge and Scopus databases. Meta-analyses were performed for the comparisons of alleles and multiple genetic models.

RESULTS

Among the cytokines studied, we found 17 polymorphisms that were the most investigated. The association to PsA was observed in the presence of polymorphisms: TNF-238 G > A (rs361525), -308 G > A (rs1800629), and -857 C > T (rs1799724); IL12B C > G (rs6887695) and A > C (rs3212227); IL23A A > G (rs2066808) and IL23R G > A (rs11209026).

CONCLUSION

Our findings suggest that these variant cytokine genes may strongly influence the immunological response of PsA.

TNF Inhibitor-Induced Psoriasis: Proposed Algorithm for Treatment and Management

Tumor necrosis factor a (TNF-α)-targeted therapies have expanded the therapeutic options for patients with inflammatory bowel disease (IBD), rheumatoid arthritis (RA), psoriasis, and psoriatic arthritis (PsA) and have significantly improved patients' quality of life. Paradoxically, anti-TNF-α agents may induce psoriatic eruptions or worsen preexisting psoriatic skin disease. Currently, there is no standard approach for the management of TNF inhibitor-induced psoriasis. Here, we conduct a literature review on TNF inhibitor-induced psoriasis and introduce a novel treatment algorithm for maintaining otherwise effective anti-TNF therapy versus switching to a different class as appropriate in the management of patients with IBD, RA, psoriasis, or PsA.

Generalized Pustular Psoriasis Induced by Infliximab in a Patient With Inflammatory Bowel Disease

The incidence of anti–tumour necrosis factor (TNF)–induced psoriasiform eruptions has ranged in the literature between 0.5% and 10.9% of patients with inflammatory bowel disease (IBD). The morphology of the rash varies, with plaque psoriasis being the most common form. Generalized pustular eruption is reported in 10.2% of cases of anti–TNF-induced psoriasis. We are reporting a unique case of anti–TNF-associated psoriasiform eruption due to the severity of the rash presenting as a generalized pustular eruption in association with plaque psoriasiform rash requiring systemic therapy.

Tumor necrosis factor-α inhibitor-induced psoriasis: Systematic review of clinical features, histopathological findings, and management experience

BACKGROUND

Tumor necrosis factor-α (TNF-α) inhibitors have been reported to induce new-onset psoriasis.

OBJECTIVE

To better define the demographic, clinical features, and treatment approach of TNF-α inhibitor-induced psoriasis.

METHODS

Systematic review of published cases of TNF-α inhibitor-induced psoriasis.

RESULTS

We identified 88 articles with 216 cases of new-onset TNF-α inhibitor-induced psoriasis. The mean age at psoriasis onset was 38.5 years. The most common underlying diseases were Crohn disease (40.7%) and rheumatoid arthritis (37.0%). Patients underwent TNF-α therapy for an average of 14.0 months before psoriasis onset with 69.9% of patients experiencing onset within the first year. The majority of patients received skin-directed therapy, though patients who discontinued TNF therapy had the greatest resolution of symptoms (47.7%) compared with those who switched to a different TNF agent (36.7%) or continued therapy (32.9%).

LIMITATIONS

Retrospective review that relies on case reports and series.

CONCLUSION

While TNF-α inhibitor cessation may result in resolution of induced psoriasis, lesions may persist. Decisions regarding treatment should be weighed against the treatability of TNF-α inhibitor-induced psoriasis, the severity of the background rheumatologic or gastrointestinal disease, and possible loss of efficacy with cessation followed by retreatment. Skin-directed therapy is a reasonable initial strategy except in severe cases.

Psoriasis, psoriatic arthritis, and rheumatoid arthritis: Is all inflammation the same?

OBJECTIVES

To review the pathophysiology, co-morbidities, and therapeutic options for psoriasis, psoriatic arthritis and rheumatoid arthritis in order to further understand the similarities and differences in treatment paradigms in the management of each disease. New targets for individualized therapeutic decisions are also identified with the aim of improving therapeutic outcome and reducing toxicity.

SEARCH STRATEGY

Using the PubMed database, we searched literature published from 2000 to 2015 using combinations of the key words "psoriasis," "psoriatic arthritis," "rheumatoid arthritis," "pathogenesis," "immunomodulation," and "treatment."

INCLUSION AND EXCLUSION CRITERIA

This was a non-systematic review and there were no formal inclusion and exclusion criteria.

DATA EXTRACTION

Abstracts identified in the search were screened for relevance and articles considered appropriate evaluated further. References within these selected articles were also screened. Information was extracted from 198 articles for inclusion in this report.

DATA SYNTHESIS

There was no formal data synthesis. Articles were reviewed and summarized according to disease area (psoriasis, psoriatic arthritis, and rheumatoid arthritis).

HEADLINE RESULTS

The pathophysiology of psoriasis, psoriatic arthritis, and rheumatoid arthritis involves chronic inflammation mediated by pro-inflammatory cytokines. Dysfunction in integrated signaling pathways affecting different constituents of the immune system result in varying clinical features in the three diseases. Co-morbidities, including cardiovascular disease, malignancies, and non-alcoholic fatty liver disease are increased. Increased understanding of the immunopathogenesis allowed development of targeted treatments; however, despite a variety of potentially predictive genetic, protein and cellular biomarkers, there is still significant unmet need in these three inflammatory disorders.

Current knowledge on psoriasis and autoimmune diseases

Psoriasis is a prevalent, chronic inflammatory disease of the skin, mediated by crosstalk between epidermal keratinocytes, dermal vascular cells, and immunocytes such as antigen presenting cells (APCs) and T cells. Exclusive cellular “responsibility” for the induction and maintenance of psoriatic plaques has not been clearly defined. Increased proliferation of keratinocytes and endothelial cells in conjunction with APC/T cell/monocyte/macrophage inflammation leads to the distinct epidermal and vascular hyperplasia that is characteristic of lesional psoriatic skin. Despite the identification of numerous susceptibility loci, no single genetic determinant has been identified as responsible for the induction of psoriasis. Thus, numerous other triggers of disease, such as environmental, microbial and complex cellular interactions must also be considered as participants in the development of this multifactorial disease. Recent advances in therapeutics, especially systemic so-called “biologics” have provided new hope for identifying the critical cellular targets that drive psoriasis pathogenesis. Recent recognition of the numerous co-morbidities and other autoimmune disorders associated with psoriasis, including inflammatory bowel disease, multiple sclerosis, rheumatoid arthritis, and systemic lupus erythematosus suggest common signaling elements and cellular mediators may direct disease pathogenesis. In this review, we discuss common cellular pathways and participants that mediate psoriasis and other autoimmune disorders that share these cellular signaling pathways.

Factors affecting response to biologic treatment in psoriasis

Psoriasis is a chronic, immune-mediated inflammatory skin disease, affecting approximately 2-4% of the population in western countries. Patients with a more severe form of the disease are typically considered for systemic therapy, including biologics. In spite of the overall superiority of biologic agents, the treatment response may differ substantially among individual patients. As with other medical conditions, a range of factors contribute to response heterogeneity observed in psoriasis. Proper identification of these factors can significantly improve the therapeutic decisions. This review focuses on potential genetic and nongenetic factors that may affect the treatment response and outcomes in patients with psoriasis.

Genetic variations of cytokines and cytokine receptors in psoriasis patients from china

Psoriasis is a chronic inflammatory and hyperproliferative skin disease affected by both genetic and environmental factors. The aim of the present study was to investigate polymorphisms in a candidate gene family of interleukin (IL) in unrelated Chinese patients with psoriasis and control subjects without psoriasis. In this case-control study, 200 unrelated Chinese psoriasis patients and 298 age- and sex-matched control subjects were enrolled. Genomic DNA was prepared from peripheral blood obtained from all psoriasis patients and control subjects. We genotyped seven single-nucleotide polymorphisms (SNPs) in candidate genes of six ILs: IL4, IL10, IL12B, IL13, IL15, and IL23R, which have been shown in the literature to be associated with psoriasis in other ethnic groups. Among the seven SNPs in the six IL genes studied, only the rs3212227 in the IL12B gene was found to be associated with psoriasis at genotypic level in the studied population. The C/C genotype in the IL12B gene is a protective factor of psoriasis (P = 0.0218; OR = 0.51; 95% CI: 0.27–0.96) in Chinese. Furthermore, the studied Chinese population has extremely low minor allele frequency for IL23R. Together, the data reveal unique genetic patterns in Chinese that may be in part responsible for the lower risk for psoriasis in this population.

Association of the interleukin 15 (IL-15) gene polymorphisms with the risk of developing ulcerative colitis in Mexican individuals

Interleukin 15 (IL-15) is a Th1-related cytokine that triggers inflammatory cell recruitment with implications for pathogenesis in ulcerative colitis. The IL-15 gene is located within a 35 kb region of the q28-31 locus of chromosome 4. In the present work, the role of IL-15 gene polymorphisms as susceptibility markers for UC was evaluated. Seven polymorphisms of IL-15 (rs3806798, rs10833, rs4956403, rs2254514, rs2857261, rs10519613, and rs1057972) were genotyped by 5' exonuclease TaqMan genotyping assays in a group of 199 Mexican patients with UC and 698 Mexican Mestizo healthy unrelated individuals. UC patients and healthy controls showed similar distribution of the rs3806798, rs10833, rs4956403, rs2857261, rs10519613, and rs1057972 polymorphisms. The rs2254514 polymorphism was significantly associated with decreased risk of UC as compared to controls under both dominant and additive models (OR 0.62, Pdom = 0.014 and OR 0.65, Padd = 0.02). The rs2254514 CC genotype was associated with young age at diagnosis <40 years (P = 0.03; OR 3.67). Five polymorphisms (rs1051613, rs2254514, rs2857261, rs1057972, and rs10833) were in strong linkage disequilibrium and were included in six haplotypes: H1 (ACAAC), H2 (CCGTC), H3 (CTAAT), H4 (CCAAT), H5 (CTAAC), and H6 (CCAAC). UC patients showed an increased frequency of the H6 haplotype (P = 0.005; OR 3.2) and a decreased frequency of the H5 haplotype (P = 0.031; OR 0.40). These results suggest that the IL-15 rs2254514 polymorphism might have an important role in the development of UC in the Mexican population. We were able to distinguish one risk and one protective uncommon haplotype for the development of UC.

Immunology of psoriasis

The skin is the front line of defense against insult and injury and contains many epidermal and immune elements that comprise the skin-associated lymphoid tissue (SALT). The reaction of these components to injury allows an effective cutaneous response to restore homeostasis. Psoriasis vulgaris is the best-understood and most accessible human disease that is mediated by T cells and dendritic cells. Inflammatory myeloid dendritic cells release IL-23 and IL-12 to activate IL-17-producing T cells, Th1 cells, and Th22 cells to produce abundant psoriatic cytokines IL-17, IFN-γ, TNF, and IL-22. These cytokines mediate effects on keratinocytes to amplify psoriatic inflammation. Therapeutic studies with anticytokine antibodies have shown the importance of the key cytokines IL-23, TNF, and IL-17 in this process. We discuss the genetic background of psoriasis and its relationship to immune function, specifically genetic mutations, key PSORS loci, single nucleotide polymorphisms, and the skin transcriptome. The association between comorbidities and psoriasis is reviewed by correlating the skin transcriptome and serum proteins. Psoriasis-related cytokine-response pathways are considered in the context of the transcriptome of different mouse models. This approach offers a model for other inflammatory skin and autoimmune diseases.

Bifidobacterium infantis 35624 modulates host inflammatory processes beyond the gut

Certain therapeutic microbes, including Bifidobacteria infantis (B. infantis) 35624 exert beneficial immunoregulatory effects by mimicking commensal-immune interactions; however, the value of these effects in patients with non-gastrointestinal inflammatory conditions remains unclear. In this study, we assessed the impact of oral administration of B. infantis 35624, for 6‒8 weeks on inflammatory biomarker and plasma cytokine levels in patients with ulcerative colitis (UC) (n = 22), chronic fatigue syndrome (CFS) (n = 48) and psoriasis (n = 26) in three separate randomized, double-blind, placebo-controlled interventions. Additionally, the effect of B. infantis 35624 on immunological biomarkers in healthy subjects (n = 22) was assessed. At baseline, both gastrointestinal (UC) and non-gastrointestinal (CFS and psoriasis) patients had significantly increased plasma levels of C-reactive protein (CRP) and the pro-inflammatory cytokines tumor necrosis factor α (TNF-α) and interleukin-6 (IL-6) compared with healthy volunteers. B. infantis 35624 feeding resulted in reduced plasma CRP levels in all three inflammatory disorders compared with placebo. Interestingly, plasma TNF-α was reduced in CFS and psoriasis while IL-6 was reduced in UC and CFS. Furthermore, in healthy subjects, LPS-stimulated TNF-α and IL-6 secretion by peripheral blood mononuclear cells (PBMCs) was significantly reduced in the B. infantis 35624-treated groups compared with placebo following eight weeks of feeding. These results demonstrate the ability of this microbe to reduce systemic pro-inflammatory biomarkers in both gastrointestinal and non-gastrointestinal conditions. In conclusion, these data show that the immunomodulatory effects of the microbiota in humans are not limited to the mucosal immune system but extend to the systemic immune system.

Association study in Romanians confirms IL23A gene haplotype block rs2066808/rs11171806 as conferring risk to psoriatic arthritis

BACKGROUND

The cytokines IL12 and IL23 have been recently implicated in the pathogenesis of psoriatic arthritis (PsA). In this study we investigated the genetic variations in the genes coding for IL12, IL23 and IL23 receptor as a plausible source of susceptibility and modification of clinical symptoms of PsA in Romanian population.

METHODS

Twenty five SNPs mapping to IL12A, IL12B, IL23A, IL23R and IL12RB1 genes were genotyped in 94 PsA patients and 161 healthy controls of Romanian ethnicity using the Sequenom genotyping platform.

RESULTS

The exonic SNP rs11171806 from IL23A gene was significantly underrepresented in patients versus controls (p=0.03, OR 0.391) and the carriers of rs11171806/rs2066808 AC haplotype had decreased risk for PsA (p=0.03). The two SNPs of the highly conserved gene IL23A are in complete LD in our population. Genetic variants of IL12B gene were associated with polyarticular subtype of PsA. No associations were found between SNPs from IL12A, IL23R and IL12RB1 genes and susceptibility to PsA and its phenotypes.

CONCLUSION

We confirm the previously described association of rs2066808 variant with psoriasis and PsA and we show evidence of an extended genomic region inside IL23A gene as carrier of true disease susceptibility factors. These data suggest a role for IL23 in the PsA pathogenesis in Romanians.

Infliximab-induced psoriasis and psoriasiform skin lesions in pediatric Crohn disease and a potential association with IL-23 receptor polymorphisms

BACKGROUND

Infliximab (IFX), an established therapy for pediatric Crohn disease (CD), is also efficacious in treating psoriasis, a skin disorder, in which tumor necrosis factor-α is implicated pathogenically. Paradoxically, there have been numerous reports of new-onset psoriasis following tumor necrosis factor-α antagonist therapy in adult patients with inflammatory bowel disease, but pediatric data are sparse.

METHODS

A retrospective review of all IFX-treated patients with CD, who subsequently developed psoriasis, at a single pediatric inflammatory bowel disease center, was performed. A subset of affected patients (10/18) and CD controls (147 of 172) treated with IFX but without the development of psoriasis were genotyped for polymorphisms in the interleukin-23 receptor (IL-23R) gene, which has been identified as conferring susceptibility to both CD and psoriasis.

RESULTS

Eighteen (10.5%) of 172 IFX-treated patients with CD developed new-onset psoriasis (n = 17) or worsening of existing psoriasis (n = 1). The duration of IFX exposure was variable, ranging from 1 to 25 infusions. Three patients discontinued IFX because of this complication. Most patients responded well to topical steroid therapy. In comparison to disease-matched controls, patients with CD developing psoriasis following IFX therapy were more likely to be homozygous for specific polymorphisms in the IL-23R gene (rs10489628, rs10789229, and rs1343151).

CONCLUSIONS

As in adults, the development of psoriasis or psoriasiform skin lesions occurs in pediatric patients with CD treated with IFX. Adequately powered studies are required to further explore the preliminary findings reported here to determine whether polymorphisms in the IL-23R gene have a role in the pathogenesis of this paradoxical process, which presently remains unexplained.

Family-based association study in Tunisian familial psoriasis

BACKGROUND

The pathogenesis of all forms of psoriasis remains obscure. Segregation analysis and twin studies together with ethnic differences in disease frequency all point to an underlying genetic susceptibility to psoriasis, which is both complex and likely to reflect the action of a number of genes.

MATERIALS AND METHODS

In the present study, we performed a family-based association study, and a transmission dysequilibrium test using the PLINK program, in a set of seven Tunisian multiplex families using a panel of 96 single-nucleotide polymorphisms localized in several regions across the genome. Ninety-five of them were reported to be associated with psoriasis in different populations.

RESULTS

Besides the confirmation of association between previous associated regions: 6p, 1p, 2p, 13q, 14q, and 20p, and cutaneous psoriasis, we identified a new association with the rs1249564 in the IL17RD gene.

CONCLUSION

Our results support the complex genetic basis of psoriasis.

[Study of genetic polymorphisms in the tumor necrosis factor α promoter region in Spanish patients with psoriasis]

BACKGROUND

Several studies have reported an association between tumor necrosis factor α (TNF-α) polymorphisms and inflammatory diseases such as psoriasis vulgaris and psoriatic arthritis, although the results vary according to the population studied. No studies have been performed in the Spanish population.

OBJECTIVE

To analyze the polymorphisms of the promoter region of the TNF-α gene in patients with moderate to severe psorasis and to identify potential differences in genotype compared to a group of healthy volunteers.

MATERIAL AND METHODS

Eighty-nine patients with moderate to severe psoriasis and 76 healthy controls with no personal or family history of psoriasis were selected. Polymorphisms of the TNF-α promoter region of both groups were genotyped.

RESULTS

We observed a higher prevalence of the genotype with both wild-type alleles at positions -238 (GG genotype, 86.5% vs 70.4%, respectively) and -1031 (TT genotype, 80.2% vs 45.8%, respectively) in patients compared to the healthy control group. The differences at positions -308 and -857 were not significant.

CONCLUSION

There are differences in polymorphisms at positions -238 and -1031 in patients with moderate to severe psoriasis compared to healthy volunteers. This observation provides further support for the importance of the part that TNF-α plays in the pathophysiology of this disease.

Association of polymorphism of IL12B gene and predisposition to psoriasis among the populationof the Northwestern region of Russia

The IL12B gene encodes protein р40 being a common subunit of interleukin-12 and interleukin-23 playing an important part in the pathogenesis of psoriasis. The IL12B gene has polymorphism rs12188300, which can be associated with the risk of psoriasis development. The goal of the study was to assess the distribution of alleles of polymorphism rs12188300 in psoriatic patients in the Northwestern region of Russia. Genotyping was carried out using the real-time allele-specific polymerase chain reaction. An increased occurrence of a rare allele T in psoriatic patients as compared to healthy people was observed (OR = 1.96, р = 0.0007). The occurrence of the rare allele T in patients with psoriatic arthritis was higher than in the control group (OR = 3.49, р = 0.005). These results suggest that rs12188300 polymorphism of the IL12B gene is a new genetic marker of psoriasis and psoriatic arthritis.

Psoriasis

Psoriasis is a common relapsing and remitting immune-mediated inflammatory disease that affects the skin and joints. This review focuses on current immunogenetic concepts, key cellular players, and axes of cytokines that are thought to contribute to disease pathogenesis. We highlight potential therapeutic targets and give an overview of the currently used immune-targeted therapies.

The IL23R R381Q gene variant protects against immune-mediated diseases by impairing IL-23-induced Th17 effector response in humans

IL-23 and Th17 cells are key players in tissue immunosurveillance and are implicated in human immune-mediated diseases. Genome-wide association studies have shown that the IL23R R381Q gene variant protects against psoriasis, Crohn's disease and ankylosing spondylitis. We investigated the immunological consequences of the protective IL23R R381Q gene variant in healthy donors. The IL23R R381Q gene variant had no major effect on Th17 cell differentiation as the frequency of circulating Th17 cells was similar in carriers of the IL23R protective (A) and common (G) allele. Accordingly, Th17 cells generated from A and G donors produced similar amounts of Th17 cytokines. However, IL-23-mediated Th17 cell effector function was impaired, as Th17 cells from A allele carriers had significantly reduced IL-23-induced IL-17A production and STAT3 phosphorylation compared to G allele carriers. Our functional analysis of a human disease-associated gene variant demonstrates that IL23R R381Q exerts its protective effects through selective attenuation of IL-23-induced Th17 cell effector function without interfering with Th17 differentiation, and highlights its importance in the protection against IL-23-induced tissue pathologies.

Psoriasis: what we have learned from mouse models

Psoriasis is a common inflammatory skin disease of unknown etiology, for which there is no cure. This heterogeneous, cutaneous, inflammatory disorder is clinically characterized by prominent epidermal hyperplasia and a distinct inflammatory infiltrate. Crosstalk between immunocytes and keratinocytes, which results in the production of cytokines, chemokines and growth factors, is thought to mediate the disease. Given that psoriasis is only observed in humans, numerous genetic approaches to model the disease in mice have been undertaken. In this Review, we describe and critically assess the mouse models and transplantation experiments that have contributed to the discovery of novel disease-relevant pathways in psoriasis. Research performed using improved mouse models, combined with studies employing human cells, xenografts and patient material, will be key to our understanding of why such distinctive patterns of inflammation develop in patients with psoriasis. Indeed, a combination of genetic and immunological investigations will be necessary to develop both improved drugs for the treatment of psoriasis and novel curative strategies.

Managing pediatric patients with psoriasis

Childhood-onset psoriasis affects approximately one-third of the psoriatic population. Among many potential treatments of childhood psoriasis, biological agents are emerging as a valuable option in the management of this disease. In Europe, etanercept has recently been approved for children aged 8 years and over. Data from a well-designed clinical trial indicate that in children, etanercept effectively reduces psoriasis symptoms, with beneficial effects evident as early as 4 weeks after the initiation of treatment. Etanercept is well tolerated; adverse effects are typically mild to moderate in severity. Early data from other biological agents are promising.

Genetic variations associated with psoriasis and psoriatic arthritis found by genome-wide association

Psoriasis and psoriatic arthritis are immune disorders with a complex polygenic basis. HLA-Cw6, which lies in the major histocompatibility region on chromosome 6, is considered the major genetic determinant of psoriasis. Recent genome-wide association studies have identified new variants outside of the MHC with relevance to the immunology of psoriasis. Variants in or near genes that encode subunits of cytokines (IL12B, IL23A) or cytokine receptors (IL23R) are interesting given that the gene product of IL12B, p40, is the target of a recently approved monoclonal antibody therapy for psoriasis (ustekinumab). Association with psoriasis and psoriatic arthritis has been found in TNFAIP3 and TNFIP1, ubiquitin ligases in the NF-kappaB pathway, and IL13, a Th2 cytokine. Copy number variation of human beta-defensin and late cornified envelope genes also associate with psoriasis. Many of these genetic variations also associate with immune disorders considered psoriatic co-morbidities, including Crohn's disease and diabetes.

Valrubicin in a topical formulation treats psoriasis in a xenograft transplantation model

Valrubicin is a cytostatic drug currently approved by the American Federal Drug Administration as a trademarked Valstar sterile solution for the treatment of bladder cancer. Valrubicin has shown an excellent therapeutic potential with minimal toxicity. This study investigated the effect in vivo of treating psoriasis with a daily topical application of valrubicin cream in a psoriasis xenograft transplantation model. Psoriasis is characterized by an accelerated keratinocyte proliferation, resulting in increased epidermal thickness. We thus studied the cytostatic potential of valrubicin on epidermal keratinocytes. In vivo, valrubicin treatment resulted in a normalization of epidermal morphology and a reduction in epidermal thickness after 12 days. In addition, the dermal vessel pattern was reduced and the stratum granulosum was regained. Staining for a regenerative proliferation marker showed a decrease in keratinocyte proliferation, and scattered epidermal cells showed apoptosis. In vitro, valrubicin was shown to localize solely to the cell cytoplasm in cultured keratinocytes and to reduce keratinocyte proliferation as well as increase apoptosis by activation of caspases 3, 7, and 9. Our results indicated that valrubicin successfully treats psoriasis in a xenograft transplantation model, suggesting that topical valrubicin may become an upcoming treatment for psoriasis.

Association between IL13 polymorphisms and psoriatic arthritis is modified by smoking

Genetic and environmental factors influence the development of psoriasis (Ps) and psoriatic arthritis (PsA). Recently, we reported that three IL13 polymorphisms, rs1800925, rs20541, and rs848, on chromosome 5q31 conferred the risk for Ps. IL13 encodes IL-13, a Th2 cytokine, and rs1800925 and rs20541 confer risk of asthma. Further, smoking may increase the risk of developing Ps. We examined the association between IL13 polymorphisms, smoking, and PsA in two Ps sample sets genotyped for rs1800925, rs20541, and rs848. We found that the minor alleles (rs1800925*T, rs20541*A, and rs848*A) were significantly associated with protection from PsA versus controls, and that no association with Ps is seen when the PsA cases are excluded. This effect was strongest with rs1800925*T (odds ratio (OR) 0.40, P(allelic) 0.000067). The prevalence of PsA in cases with the rs1800925*CT or TT genotype is about half that of those with the CC genotype (15.5 vs 32.1%, P=0.0002). However, smoking appears to abrogate this effect (CT/TT/non-smoker, prevalence of PsA 13%, OR 0.20, P=0.0001; CT/TT/smoker, prevalence 38%, OR 0.88, P=0.74, CC/non-smoker, prevalence 42% (reference), CC/smoker prevalence 47%, OR 1.21, P=0.47). This study suggests that IL13 polymorphisms associate most strongly with PsA and that smoking may modulate this effect.