Overrepresentation of IL-17A and IL-22 producing CD8 T cells in lesional skin suggests their involvement in the pathogenesis of psoriasis

Cytokines in psoriasis: From pathogenesis to targeted therapy

Psoriasis is a multifactorial disease that affects 0.84% of the global population and it can be associated with disabling comorbidities. As patients present with thick scaly lesions, psoriasis was long believed to be a disorder of keratinocytes. Psoriasis is now understood to be the outcome of the interaction between immunological and environmental factors in individuals with genetic predisposition. While it was initially thought to be solely mediated by cytokines of type-1 immunity, namely interferon-γ, interleukin-2, and interleukin-12 because it responds very well to cyclosporine, a reversible IL-2 inhibitor; the discovery of Th-17 cells advanced the understanding of the disease and helped the development of biological therapy. This article aims to provide a comprehensive review of the role of cytokines in psoriasis, highlighting areas of controversy and identifying the connection between cytokine imbalance and disease manifestations. It also presents the approved targeted treatments for psoriasis and those currently under investigation.

Paradoxical psoriasis induced by IL-17 inhibitors: a case series of patients with axial spondyloarthritis and a systematic literature review

Following the market authorization of interleukin (IL)-17 inhibitors, a growing number of cases of IL-17 inhibitor-induced paradoxical psoriasis (PsO) have been reported. Our objectives were to present two cases of IL-17 inhibitor-induced paradoxical PsO and to systematically review the literature for similar cases, summarizing and presenting the relevant data. A systematic literature review of previously presented cases of paradoxical PsO induced by IL-17 inhibitors was conducted. We presented two patients with axial spondyloarthritis (axSpA) and paradoxical PsO induced by secukinumab (SEC). One patient's psoriatic lesions responded well to adjuvant topical treatment, while the other patient required a combination of topical treatment and cyclosporine Α for successful treatment. SEC was continued in both cases. We also identified 35 patients with IL-17 inhibitor-induced paradoxical PsO in the literature review. The most frequent types of paradoxical PsO were palmoplantar pustular and plaque PsO, while the median latency period was 11 weeks. Approximately one-third of patients continued IL-17 inhibitor treatment with adjunctive therapy, primarily topical, which produced satisfactory results in most patients. Almost two-thirds of the patients discontinued the IL-17 inhibitor, with the majority of patients switching to another biological agent with a different mechanism of action or initiating other systemic antipsoriatic treatments, resulting in mainly satisfactory outcomes. Therefore, paradoxical PsO induced by IL-17 inhibitors appears to respond well in both patients who continue IL-17 inhibitors with adjunctive treatment and those who discontinue IL-17 inhibitors while switching to a different class of biological agent or initiating other systemic antipsoriatic treatments.

T cell-mediated skin-brain axis: Bridging the gap between psoriasis and psychiatric comorbidities

Psoriasis, a chronic inflammatory skin condition, is often accompanied by psychiatric comorbidities such as anxiety, depression, suicidal ideation, and other mental disorders. Psychological disorders may also play a role in the development and progression of psoriasis. The intricate interplay between the skin diseases and the psychiatric comorbidities is mediated by the 'skin-brain axis'. Understanding the mechanisms underlying psoriasis and psychiatric comorbidities can help improve the efficacy of treatment by breaking the vicious cycle of diseases. T cells and related cytokines play a key role in the pathogenesis of psoriasis and psychiatric diseases, and are crucial components of the 'skin-brain axis'. Apart from damaging the blood-brain barrier (BBB) directly, T cells and secreted cytokines could interact with the hypothalamic-pituitary-adrenal axis (HPA axis) and the sympathetic nervous system (SNS) to exacerbate skin diseases or mental disorders. However, few reviews have systematically summarized the roles and mechanisms of T cells in the interaction between psoriasis and psychiatric comorbidities. In this review, we discussed several key T cells and their roles in the 'skin-brain axis', with a focus on the mechanisms underlying the interplay between psoriasis and mental commodities, to provide data that might help develop effective strategies for the treatment of both psoriasis and psychiatric comorbidities.

The Immunology of Psoriasis-Current Concepts in Pathogenesis

Psoriasis is one of the most common inflammatory skin diseases with a chronic, relapsing-remitting course. The last decades of intense research uncovered a pathological network of interactions between immune cells and other types of cells in the pathogenesis of psoriasis. Emerging evidence indicates that dendritic cells, TH17 cells, and keratinocytes constitute a pathogenic triad in psoriasis. Dendritic cells produce TNF-α and IL-23 to promote T cell differentiation toward TH17 cells that produce key psoriatic cytokines IL-17, IFN-γ, and IL-22. Their activity results in skin inflammation and activation and hyperproliferation of keratinocytes. In addition, other cells and signaling pathways are implicated in the pathogenesis of psoriasis, including TH9 cells, TH22 cells, CD8+ cytotoxic cells, neutrophils, γδ T cells, and cytokines and chemokines secreted by them. New insights from high-throughput analysis of lesional skin identified novel signaling pathways and cell populations involved in the pathogenesis. These studies not only expanded our knowledge about the mechanisms of immune response and the pathogenesis of psoriasis but also resulted in a revolution in the clinical management of patients with psoriasis. Thus, understanding the mechanisms of immune response in psoriatic inflammation is crucial for further studies, the development of novel therapeutic strategies, and the clinical management of psoriasis patients. The aim of the review was to comprehensively present the dysregulation of immune response in psoriasis with an emphasis on recent findings. Here, we described the role of immune cells, including T cells, B cells, dendritic cells, neutrophils, monocytes, mast cells, and innate lymphoid cells (ILCs), as well as non-immune cells, including keratinocytes, fibroblasts, endothelial cells, and platelets in the initiation, development, and progression of psoriasis.

Regulation of the Immune Cell Repertoire in Psoriasis Patients Upon Blockade of IL-17A or TNFα

INTRODUCTION

Targeting of the proinflammatory cytokine interleukin 17A (IL-17A) or tumor necrosis factor alpha (TNFα) with the monoclonal antibodies (mAbs) ixekizumab or adalimumab, respectively, is a successful therapy for chronic plaque psoriasis. The effects of these treatments on immune cell populations in the skin are largely unknown.

METHODS

In this study, we compared the composition of cutaneous, lesional and non-lesional immune cells and blood immune cells in ixekizumab- or adalimumab-treated patients with psoriasis.

RESULTS

Our data reveal that both treatments efficiently downregulate T cells, macrophages and different subsets of dendritic cells (DCs) in lesional skin towards levels of healthy skin. In contrast to lesional skin, non-lesional areas in patients harbor only few or no detectable DCs compared to the skin of healthy subjects. Treatment with neither ixekizumab nor adalimumab reversed this DC imbalance in non-lesional skin of psoriatic patients.

CONCLUSION

Our study shows that anti-IL-17A and anti-TNFα therapy rebalances the immune cell repertoire of lesional skin in psoriatic patients but fails to restore the disturbed immune cell repertoire in non-lesional skin.

HELIOS-expressing human CD8 T cells exhibit limited effector functions

Introduction

The transcription factor HELIOS is primarily known for its expression in CD4 regulatory T cells, both in humans and mice. In mice, HELIOS is found in exhausted CD8 T cells. However, information on human HELIOS+ CD8 T cells is limited and conflicting.

Methods

In this study, we characterized by flow cytometry and transcriptomic analyses human HELIOS+ CD8 T cells.

Results

These T cells primarily consist of memory cells and constitute approximately 21% of blood CD8 T cells. In comparison with memory HELIOS- T-BEThigh CD8 T cells that displayed robust effector functions, the memory HELIOS+ T-BEThigh CD8 T cells produce lower amounts of IFN-γ and TNF-α and have a lower cytotoxic potential. We wondered if these cells participate in the immune response against viral antigens, but did not find HELIOS+ cells among CD8 T cells recognizing CMV peptides presented by HLA-A2 and HLA-B7. However, we found HELIOS+ CD8 T cells that recognize a CMV peptide presented by MHC class Ib molecule HLA-E. Additionally, a portion of HELIOS+ CD8 T cells is characterized by the expression of CD161, often used as a surface marker for identifying TC17 cells. These CD8 T cells express TH17/TC17-related genes encoding RORgt, RORa, PLZF, and CCL20.

Discussion

Our findings emphasize that HELIOS is expressed across various CD8 T cell populations, highlighting its significance beyond its role as a transcription factor for Treg or exhausted murine CD8 T cells. The significance of the connection between HELIOS and HLA-E restriction is yet to be understood.

Human in vitro-induced IL-17A+ CD8+ T-cells exert pro-inflammatory effects on synovial fibroblasts

IL-17A+ CD8+ T-cells, termed Tc17 cells, have been identified at sites of inflammation in several immune-mediated inflammatory diseases. However, the biological function of human IL-17A+ CD8+ T-cells is not well characterized, likely due in part to the relative scarcity of these cells. Here, we expanded IL-17A+ CD8+ T-cells from healthy donor PBMC or bulk CD8+ T-cell populations using an in vitro polarization protocol. We show that T-cell activation in the presence of IL-1β and IL-23 significantly increased the frequencies of IL-17A+ CD8+ T-cells, which was not further enhanced by IL-6, IL-2, or anti-IFNγ mAb addition. In vitro-generated IL-17A+ CD8+ T-cells displayed a distinct type-17 profile compared with IL-17A- CD8+ T-cells, as defined by transcriptional signature (IL17A, IL17F, RORC, RORA, MAF, IL23R, CCR6), high surface expression of CCR6 and CD161, and polyfunctional production of IL-17A, IL-17F, IL-22, IFNγ, TNFα, and GM-CSF. A significant proportion of in vitro-induced IL-17A+ CD8+ T-cells expressed TCRVα7.2 and bound MR1 tetramers indicative of MAIT cells, indicating that our protocol expanded both conventional and unconventional IL-17A+ CD8+ T-cells. Using an IL-17A secretion assay, we sorted the in vitro-generated IL-17A+ CD8+ T-cells for functional analysis. Both conventional and unconventional IL-17A+ CD8+ T-cells were able to induce pro-inflammatory IL-6 and IL-8 production by synovial fibroblasts from patients with psoriatic arthritis, which was reduced upon addition of anti-TNFα and anti-IL-17A neutralizing antibodies. Collectively, these data demonstrate that human in vitro-generated IL-17A+ CD8+ T-cells are biologically functional and that their pro-inflammatory function can be targeted, at least in vitro, using existing immunotherapy.

T cells in the pathogenesis of axial spondyloarthritis

Axial spondyloarthritis (axSpA) is the prototype of the spondyloarthritis spectrum. The involvement of T cells in its pathogenesis has long been suspected on the basis of the association with the major histocompatibility complex I molecule HLA-B27 and the pivotal role of interleukin 17 in the inflammatory mechanisms associated with the disease. Moreover, the presence of unconventional or "innate-like" T cells within the axial enthesis suggests an important role for these cells in the pathophysiology of the disease. In this review, we describe the characteristics and the interleukin 17 secretion capacity of the T-cell subsets identified in axSpA. We discuss the genetic and epigenetic mechanisms that support the alteration of T-cell functions and promote their activation in axSpA. We also discuss recent data on T cells that could explain the extra-articular manifestations of the SpA spectrum.

Crosstalk: keratinocytes and immune cells in psoriasis

In the past, psoriasis was considered a skin disease caused only by keratinocyte disorders. However, the efficacy of immunosuppressive drugs and biologics used to treat psoriasis proves that psoriasis is an immune-mediated disease. Indeed, a variety of immune cells are involved in the pathogenesis of psoriasis, including dendritic cells, Th17 cells, and resident memory T cells. Furthermore, keratinocytes play a role in the development of psoriasis as immune cells by secreting antibacterial peptides, chemokines, tumor necrosis factor-α, interleukin (IL)-36, and IL-23. These immune cells and skin cells interact and drive the aberrant differentiation and proliferation of keratinocytes. This crosstalk between keratinocytes and immune cells critical in the pathogenesis of psoriasis forms an inflammatory loop, resulting in the persistence or exacerbation of psoriasis plaques.

CD8 T-cell subsets: heterogeneity, functions, and therapeutic potential

CD8 T cells play crucial roles in immune surveillance and defense against infections and cancer. After encountering antigenic stimulation, naïve CD8 T cells differentiate and acquire effector functions, enabling them to eliminate infected or malignant cells. Traditionally, cytotoxic T cells, characterized by their ability to produce effector cytokines and release cytotoxic granules to directly kill target cells, have been recognized as the constituents of the predominant effector T-cell subset. However, emerging evidence suggests distinct subsets of effector CD8 T cells that each exhibit unique effector functions and therapeutic potential. This review highlights recent advancements in our understanding of CD8 T-cell subsets and the contributions of these cells to various disease pathologies. Understanding the diverse roles and functions of effector CD8 T-cell subsets is crucial to discern the complex dynamics of immune responses in different disease settings. Furthermore, the development of immunotherapeutic approaches that specifically target and regulate the function of distinct CD8 T-cell subsets holds great promise for precision medicine.

The roles of T cells in psoriasis

Psoriasis is a recurring inflammatory skin condition characterized by scaly, red patches on the skin. It affects approximately 3% of the US population and is associated with histological changes such as epidermal hyperplasia, increased blood vessel proliferation, and infiltration of leukocytes into the skin's dermis. T cells, which are classified into various subtypes, have been found to play significant roles in immune-mediated diseases, particularly psoriasis. This paper provides a review of the different T lymphocyte subtypes and their functions in psoriasis, as well as an overview of targeted therapies for treating psoriasis.

IL-22 as a target for therapeutic intervention: Current knowledge on its role in various diseases

IL-22 has emerged as a crucial cytokine mediating protective response against pathogens and tissue regeneration. Dysregulated production of IL-22 has been shown to play a pivotal role in the pathogenesis of various diseases like malignant tumours, viral, cardiovascular, allergic and autoimmune disorders. Interleukin 22 belongs to IFN-IL-10 cytokine family. It is a major proinflammatory cytokine secreted by activated Th1 cells (Th22), though can also be secreted by many other immune cells like group 3 innate lymphocytes, γδ T cells, NK cells, NK T cells, and mucosal associated invariant T cells. Th22 cells exclusively release IL-22 but not IL-17 or IFN-γ (as Th1 cells releases IFN-γ along with IL-22 and Th17 cells releases IL-17 along with IL-22) and also express aryl hydrocarbon receptor as the key transcription factor. Th22 cells also exhibit expression of chemokine receptor CCR6 and skin-homing receptors CCR4 and CCR10 indicating the involvement of this subset in bolstering epithelial barrier immunity and promoting secretion of antimicrobial peptides (AMPs) from intestinal epithelial cells. The function of IL-22 is modulated by IL-22 binding protein (binds to IL-22 and inhibits it binding to its cell surface receptor); which serves as a competitor for IL-22R1 chain of IL-22 receptor. The pathogenic and protective nature of the Th22 cells is modulated both by the site of infected tissue and the type of disease pathology. This review aims to discuss key features of IL-22 biology, comparisons between IL and 22 and IFN-γ and its role as a potential immune therapy target in different maladies.

Eicosapentaenoic acid reduces the proportion of IL-17A-producing T cells in a 3D psoriatic skin model

Psoriasis is a skin disease presenting as erythematous lesions with accentuated proliferation of epidermal keratinocytes, infiltration of leukocytes, and dysregulated lipid metabolism. T cells play essential roles in the disease. n-3 polyunsaturated fatty acids are anti-inflammatory metabolites, which exert an immunosuppressive effect on healthy T cells. However, the precise mechanistic processes of n-3 polyunsaturated fatty acids on T cells in psoriasis are still unrevealed. In this study, we aimed to evaluate the action of eicosapentaenoic acid (EPA) on T cells in a psoriatic skin model produced with T cells. A coculture of psoriatic keratinocytes and polarized T cells was prepared using culture media, which was either supplemented with 10 μM EPA or left unsupplemented. Healthy and psoriatic skin substitutes were produced according to the self-assembly method. In the coculture model, EPA reduced the proportion of IL-17A-positive cells, while increasing that of FOXP3-positive cells, suggesting an increase in the polarization of regulatory T cells. In the 3D psoriatic skin model, EPA normalized the proliferation of psoriatic keratinocytes and diminished the levels of IL-17A. The expression of the proteins of the signal transducer and activator of transcription was influenced following EPA supplementation with downregulation of the phosphorylation levels of signal transducer and activator of transcription 3 in the dermis. Finally, the NFκB signaling pathway was modified in the EPA-supplemented substitutes with an increase in Fas amounts. Ultimately, our results suggest that in this psoriatic model, EPA exerts its anti-inflammatory action by decreasing the proportion of IL-17A-producing T cells.

Three cases of subcorneal pustular dermatosis with immunohistochemical examinations

Subcorneal pustular dermatosis, a rare, benign skin disease, is a type of neutrophilic dermatosis. The authors reported three cases of subcorneal pustular dermatosis. In case 1, a 9-year-old girl developed a skin rash with blisters following a mycoplasma infection and had a flare-up due to a common cold. She was successfully treated with a topical corticosteroid. In case 2, a 70-year-old woman who had been treated for rheumatoid arthritis with adalimumab, salazosulfapyridine, and leflunomide developed 3- to 5-mm pustules on her trunk and thighs 4 days after flu vaccination. The rash disappeared with drug withdrawal and treatment with diaminodiphenyl sulfone. In case 3, an 81-year-old man, who was diagnosed with pyoderma gangrenosum at 61 years old, developed multiple small flaccid pustules on his trunk and extremities due to an infection in the arteriovenous shunt area on the forearm. The pustule disappeared with intravenous antibiotic therapy; however, the pustules subsequently flared up along with ulcers typical of pyoderma gangrenosum. He was given oral prednisolone therapy, which was effective for the small pustules and some ulcers. Immunohistochemical examination of the three cases revealed neutrophilic infiltration in the subcorneal layer of the epidermis. The pustules contained neutrophils as well as some CD68+ and a few CD1a+ cells. The epidermis and dermis were more predominantly infiltrated by CD4+ cells than by CD8+ cells. Positive stainings for interleukin 8, interleukin 36γ, and phospho-extracellular signal-regulated kinases 1 and 2 were observed in the upper layers of the epidermis below the pustules. Although the pathogenesis of subcorneal pustular dermatosis has not been clarified, the current results suggest that a variety of inflammatory cells, including those responsible for both innate and acquired immunity, are involved in the accumulation of neutrophils in subcorneal pustular dermatosis.

The biological basis of disease recurrence in psoriasis

Despite the amazing advances produced in our understanding of the pathogenesis of psoriasis, which have led to a therapeutic revolution, our knowledge of the mechanisms of relapse and elicitation of lesions is just starting to unravel. This narrative review tours the different cell types and mechanisms involved in the priming, maintenance, and relapse of psoriasis vulgaris. Our discussion includes dendritic cells, T cells, tissue resident memory cells and mast cells, with a foray into the epigenetic mechanisms of inflammatory memory in keratinocytes. Increasing knowledge is providing a glimpse of a potential therapeutic window of opportunity in psoriasis, providing long term remission and eventual modification of the natural history of the disease.

Serum IL-23 significantly decreased in obese patients with psoriatic arthritis six months after a structured weight loss intervention

INTRODUCTION

Patients with psoriatic arthritis (PsA) are frequently obese. We have previously shown decreased disease activity in patients with PsA with a body mass index (BMI) ≥ 33 kg/m² following weight loss treatment with Very Low Energy Diet (VLED), resulting in a median weight loss of 18.6% at six months (M6) after baseline (BL). In this study we assessed the effects of VLED on cytokines and adipokines at M6 in the same patients with PsA and controls (matched on sex, age and weight).

METHODS

VLED (640 kcal/day) during 12 or 16 weeks, depending on BL BMI < 40 or ≥ 40 kg/m², was taken and followed by an energy-restricted diet. Cytokines and adipokines were measured with Magnetic Luminex Assays at BL and M6.

RESULTS

Serum interleukin (IL)-23, (median (interquartile range) 0.40 (0.17-0.54) ng/mL vs. 0.18 (0.10-0.30) ng/mL, p < 0.001) and leptin (26.28 (14.35-48.73) ng/mL vs. 9.25 (4.40-16.24) ng/mL, p < 0.001) was significantly decreased in patients with PsA. Serum total (tot)-adiponectin and high molecular weight (HMW) adiponectin increased significantly. Similar findings were found in controls. Also, in patients with PsA, ∆BMI was positively correlated with ∆IL-23 (r_S = 0.671, p < 0.001). In addition, significant positive correlations were found between ΔBMI and ΔDisease Activity Score (DAS28CRP), ΔCRP, Δtumor necrosis factor (TNF)-α, ΔIL-13, ∆IL-17 and Δleptin, and negative correlations between ΔBMI and Δtot-adiponectin.

CONCLUSIONS

Weight loss was associated with decreased levels of leptin and cytokines, in particular IL-23. These findings may partly explain the anti-inflammatory effect of weight reduction in PsA.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT02917434, registered on September 21, 2016, retrospectively registered.

Friend or Foe - Tc17 cell generation and current evidence for their importance in human disease

The term Tc17 cells refers to interleukin 17 (IL-17)-producing CD8+ T cells. While IL-17 is an important mediator of mucosal defense, it is also centrally involved in driving the inflammatory response in immune-mediated diseases, such as psoriasis, multiple sclerosis, and inflammatory bowel disease. In this review, we aim to gather the current knowledge on the phenotypic and transcriptional profile, the in vitro and in vivo generation of Tc17 cells, and the evidence pointing towards a relevant role of Tc17 cells in human diseases such as infectious diseases, cancer, and immune-mediated diseases.

MCAM+CD161- Th17 Subset Expressing CD83 Enhances Tc17 Response in Psoriasis

Recent studies have highlighted the pathogenic roles of IL-17-producing CD8+ T cells (T-cytotoxic 17 [Tc17]) in psoriasis. However, the underlying mechanisms of Tc17 induction remain unclear. In this study, we focused on the pathogenic subsets of Th17 and their mechanism of promotion of Tc17 responses. We determined that the pathogenic Th17-enriched fraction expressed melanoma cell adhesion molecule (MCAM) and CCR6, but not CD161, because this subset produced IL-17A abundantly and the presence of these cells in the peripheral blood of patients has been correlated with the severity of psoriasis. Intriguingly, the serial analysis of gene expression revealed that CCR6+MCAM+CD161-CD4+ T cells displayed the gene profile for adaptive immune responses, including CD83, which is an activator for CD8+ T cells. Coculture assay with or without intercellular contact between CD4+ and CD8+ T cells showed that CCR6+MCAM+CD161-CD4+ T cells induced the proliferation of CD8+ T cells in a CD83-dependent manner. However, the production of IL-17A by CD8+ T cells required exogenous IL-17A, suggesting that intercellular contact via CD83 and the production of IL-17A from activated CD4+ T cells elicit Tc17 responses. Intriguingly, the CD83 expression was enhanced in the presence of IL-15, and CD83+ cells stimulated with IL-1β, IL-23, IL-15, and IL-15Rα did not express FOXP3. Furthermore, CCR6+MCAM+CD161-CD4+ T cells expressing CD83 were increased in the peripheral blood of patients, and the CD83+ Th17-type cells accumulated in the lesional skin of psoriasis. In conclusion, pathogenic MCAM+CD161- Th17 cells may be involved in the Tc17 responses via IL-17A and CD83 in psoriasis.

Single cell and spatial sequencing define processes by which keratinocytes and fibroblasts amplify inflammatory responses in psoriasis

The immunopathogenesis of psoriasis, a common chronic inflammatory disease of the skin, is incompletely understood. Here we demonstrate, using a combination of single cell and spatial RNA sequencing, IL-36 dependent amplification of IL-17A and TNF inflammatory responses in the absence of neutrophil proteases, which primarily occur within the supraspinous layer of the psoriatic epidermis. We further show that a subset of SFRP2+ fibroblasts in psoriasis contribute to amplification of the immune network through transition to a pro-inflammatory state. The SFRP2+ fibroblast communication network involves production of CCL13, CCL19 and CXCL12, connected by ligand-receptor interactions to other spatially proximate cell types: CCR2+ myeloid cells, CCR7+ LAMP3+ dendritic cells, and CXCR4 expressed on both CD8+ Tc17 cells and keratinocytes, respectively. The SFRP2+ fibroblasts also express cathepsin S, further amplifying inflammatory responses by activating IL-36G in keratinocytes. These data provide an in-depth view of psoriasis pathogenesis, which expands our understanding of the critical cellular participants to include inflammatory fibroblasts and their cellular interactions.

An optical system for noninvasive microscopy of psoriatic mice in vivo

Psoriasis is a chronic inflammatory skin disease involved with both complex morphological changes of skin and immune processes. The clinical diagnostics and research of psoriasis often require invasive biopsy which lacks their real-time dynamics in vivo. Here we report a noninvasive microscopic system developed by combining in vivo fluorescent microscopy, optical clearing, and immunolabeling to enable real-time imaging of immune cells and cytokines in blood flow in psoriatic animal models. The vascular morphology and time-lapse kinetics of interleukin (IL)-23, IL-17, tumor necrosis factor-α, and CD4+ cells in blood are captured at submicron resolution through the thickening epidermis and opaque scales during the development of psoriasis in vivo. Our data suggest IL-23 recruits CD4+ cells to release IL-17 in blood that further leaks out in the psoriatic skin area. This optical system enables noninvasive and real-time assessment of immune molecules and cells in vivo, providing good potential for medical researches on psoriasis.

Understanding the squamous cell carcinoma immune microenvironment

Primary cutaneous squamous cell carcinoma (cSCC) is the second most common human cancer with a rising incidence of about 1.8 million in the United States annually. Primary cSCC is usually curable by surgery; however, in some cases, cSCC eventuates in nodal metastasis and death from disease specific death. cSCC results in up to 15,000 deaths each year in the United States. Until recently, non-surgical options for treatment of locally advanced or metastatic cSCC were largely ineffective. With the advent of checkpoint inhibitor immunotherapy, including cemiplimab and pembrolizumab, response rates climbed to 50%, representing a vast improvement over chemotherapeutic agents used previously. Herein, we discuss the phenotype and function of SCC associated Langerhans cells, dendritic cells, macrophages, myeloid derived suppressor cells and T cells as well as SCC-associated lymphatics and blood vessels. Possible role(s) of SCC-associated cytokines in progression and invasion are reviewed. We also discuss the SCC immune microenvironment in the context of currently available and pipeline therapeutics.

The Potential Importance of CXCL1 in the Physiological State and in Noncancer Diseases of the Cardiovascular System, Respiratory System and Skin

In this paper, we present a literature review of the role of CXC motif chemokine ligand 1 (CXCL1) in physiology, and in selected major non-cancer diseases of the cardiovascular system, respiratory system and skin. CXCL1, a cytokine belonging to the CXC sub-family of chemokines with CXC motif chemokine receptor 2 (CXCR2) as its main receptor, causes the migration and infiltration of neutrophils to the sites of high expression. This implicates CXCL1 in many adverse conditions associated with inflammation and the accumulation of neutrophils. The aim of this study was to describe the significance of CXCL1 in selected diseases of the cardiovascular system (atherosclerosis, atrial fibrillation, chronic ischemic heart disease, hypertension, sepsis including sepsis-associated encephalopathy and sepsis-associated acute kidney injury), the respiratory system (asthma, chronic obstructive pulmonary disease (COPD), chronic rhinosinusitis, coronavirus disease 2019 (COVID-19), influenza, lung transplantation and ischemic-reperfusion injury and tuberculosis) and the skin (wound healing, psoriasis, sunburn and xeroderma pigmentosum). Additionally, the significance of CXCL1 is described in vascular physiology, such as the effects of CXCL1 on angiogenesis and arteriogenesis.

Genetic deletion of Cyp4f18 disrupts the omega-3 epoxidation pathway and results in psoriasis-like dermatitis

Cyp4f18 catalyzes the conversion of n-3 polyunsaturated fatty acids (PUFAs) into omega-3 epoxides, such as 17,18-epoxyeicosatetraenoic acid (17,18-EpETE) and 19,20-epoxydocosapentaenoic acid (19,20-EpDPE) from eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), respectively. Cyp4f18-deficient mice spontaneously develop psoriasis-like dermatitis. A significant increase in the number of IL-17A-positive gamma delta (γδ) T cells in the skin and enlargement of draining lymph nodes was observed. These symptoms were drastically suppressed by antibiotic treatment. Cyp4f18 is highly expressed in dendritic cells (DCs), and Cyp4f18-deficient bone marrow-derived dendritic cells (BMDCs) show markedly increased expression levels of cytokines such as IL-23 and IL-1β in response to lipopolysaccharide (LPS) stimulation. Lipidomic analysis of lymph nodes and BMDCs revealed a significant decrease in a series of omega-3 epoxidized metabolites. Among them, 17,18-dihydroxyeicosatetraenoic acid (17,18-diHETE), a vicinal diol derived from EPA omega-3 epoxidation suppressed IL-23 production in LPS-stimulated BMDCs in Cyp4f18-deficient mice. These results demonstrate that Cyp4f18 endogenously produces omega-3-epoxidized metabolites in the draining lymph nodes, and these metabolites contribute to skin homeostasis by suppressing the excessive activation of the IL-23/IL-17 axis initiated by DCs.

The Role of T Helper 22 Cells in Dermatological Disorders

T helper 22 (Th22) cells are a newly identified subset of CD4+ T cells that secrete the effector cytokine interleukin 22 (IL-22) upon specific antigen stimulation, barely with IFN-γ or IL-17. Increasing studies have demonstrated that Th22 cells and IL-22 play essential roles in skin barrier defense and skin disease pathogenesis since the IL-22 receptor is widely expressed in the skin, especially in keratinocytes. Herein, we reviewed the characterization, differentiation, and biological activities of Th22 cells and elucidated their roles in skin health and disease. We mainly focused on the intricate crosstalk between Th22 cells and keratinocytes and provided potential therapeutic strategies targeting the Th22/IL-22 signaling pathway.

Secukinumab demonstrated sustained retention, effectiveness and safety in a real-world setting in patients with moderate to severe plaque psoriasis: long-term results from an interim analysis of the SERENA study

BACKGROUND

Randomised controlled trials of secukinumab have shown sustained efficacy and a favourable safety profile in multiple manifestations of psoriatic disease.

OBJECTIVES

To assess the long-term, real-world retention, effectiveness, and safety of secukinumab in routine clinical practice for the treatment of moderate to severe plaque-type psoriasis (PsO).

METHODS

SERENA (CAIN457A3403) is a large, ongoing, longitudinal, observational study conducted at 438 sites and 19 countries across Europe for an expected duration of up to 5 years in adult patients with moderate to severe PsO, psoriatic arthritis, and ankylosing spondylitis. Patients received ≥16 weeks of secukinumab treatment before enrolment. This interim analysis presents data from PsO patients, who were enrolled in the study between October-2016-October-2018 and were observed for ≥2 years.

RESULTS

In total, 1756 patients (67.3% male) with a mean age of 48.4 years and body mass index of 28.8 kg/m² were included in the analysis. The secukinumab treatment retention rates after 1, 2 and 3 years in the study were 88.0%, 76.4% and 60.5%, respectively. Out of the 648 patients who discontinued the study, the most common reasons included lack of efficacy (42.6%), adverse event (17.4%), physician decision (12.2%) and subject decision (11.6%). Mean±SD absolute PASI was 21.0±13.0 at the start of treatment (n=1,564). At Baseline, the mean±SD PASI score reduced to 2.6±4.8 and remained low at Year 1 (2.3±4.3), Year 2 (1.9±3.6) and Year 3 (1.9±3.5). The safety profile of secukinumab during the SERENA study was consistent with its known safety profile, with no new safety signals reported. Particularly low rates of inflammatory bowel disease (0.3%; Incidence Rate [IR]:0.15), candida infections (3.1%; IR:1.43) and MACE (0.9%; IR:0.37) were observed.

CONCLUSIONS

Secukinumab showed high treatment persistence, sustained effectiveness and a favourable safety profile up to 3 years of follow-up in the real-world population of PsO patients observed in SERENA.

Increased proportions of inflammatory T cells and their correlations with cytokines and clinical parameters in patients with ankylosing spondylitis from northern Sweden

Ankylosing spondylitis (AS) is an autoimmune disease affecting parts of the skeletal structure in particular. Previously increased levels of the inflammatory cell types Th17, Th22, Tc17 and Tc22 cells have been shown to be associated with AS. Here, we analysed the levels of inflammatory T cell subsets, related cytokines and clinical characteristics of AS patients vs controls from northern Sweden. Peripheral blood mononuclear cells (PBMCs) obtained from 50 AS patients and 50 matched controls were short term stimulated with PMA/Ionomycin, stained and analysed by flow cytometry. Plasma levels of Interleukin (IL)‐17, IL‐22, IL‐10 as well as clinically relevant markers were determined. Compared to male controls, male AS patients showed 1.5‐ to 2‐fold increases of Th17 (P = .013), Th22 (P = .003) and Tc22 (P = .024) among CD45⁺CD3⁺ lymphocytes. Plasma IL‐22 levels correlated with the Tc17 proportion in male patients (R_s = 0.499, P = .003) and plasma IL‐10 levels were inversely correlated with Tc17 among all patients (R_s = −0.276, P = .05). Male patients with syndesmophytes showed significantly higher Th17 proportions (P = .038). In female AS patients, Tc22 was negatively correlated with C‐reactive protein (high sensitivity) (hsCRP) (R_s = −0.573, P = .016). We confirmed increased proportions of inflammatory T cells and correlations with relevant cytokines from male AS patients. The correlation between Th17 and syndesmophytes supports a role of Th17 in the pathogenic process.

Transcriptomes of MPO-deficient patients with generalized pustular psoriasis reveals expansion of CD4+ cytotoxic T cells and an involvement of the complement system

Generalized pustular psoriasis (GPP) is a severe psoriatic subtype characterized by epidermal neutrophil infiltration. Although variants in IL36RN and MPO have been shown to affect immune cells, a systematic analysis of neutrophils and peripheral blood mononuclear cells (PBMCs) subsets and their differential gene expression dependent on MPO genotypes was not performed yet. We assessed transcriptomes of MPO-deficient patients using single cell RNA-sequencing (scRNAseq) of PBMCs and RNA-sequencing of neutrophils in stable disease state. Cell type annotation by multimodal reference mapping of scRNAseq data was verified by flow cytometry of surface and intracellular markers; proportions of CD4⁺ cytotoxic T-lymphocytes (CTLs) and other CD4⁺ effector cells were increased in GPP, while frequencies of naïve CD4⁺ T cells were significantly lower. The expression of FGFBP2 marking CD4⁺ CTLs and CD8⁺ effector memory T-cells (TEMs) was elevated in GPP patients with disease-contributing variants compared to non-carriers (p=0.0015). In neutrophils, differentially expressed genes (DEGs) were significantly enriched in genes of the classical complement activation pathway. Future studies assessing affected cell-types and pathways will show their contribution to GPP's pathogenesis, and indicate whether findings can be transferred to the acute epidermal situation and whether depletion or inactivation of CD4⁺ CTLs may be a reasonable therapeutic approach.

The biological basis of disease recurrence in psoriasis: a historical perspective and current models

A key challenge in psoriasis therapy is the tendency for lesions to recur in previously affected anatomical locations after treatment discontinuation following lesion resolution. Available evidence supports the concept of a localized immunological ‘memory’ that persists in resolved skin after complete disappearance of visible inflammation, as well as the role of a specific subpopulation of T cells characterized by the dermotropic CCR4⁺ phenotype and forming a local memory. Increasing knowledge of the interleukin (IL)‐23/T helper 17 (Th17) cell pathway in psoriasis immunopathology is pointing away from the historical classification of psoriasis as primarily a Th1‐type disease. Research undertaken from the 1990s to the mid‐2000s provided evidence for the existence of a large population of CD8⁺ and CD4⁺ tissue‐resident memory T cells in resolved skin, which can initiate and perpetuate immune responses of psoriasis in the absence of T‐cell recruitment from the blood. Dendritic cells (DCs) are antigen‐presenting cells that contribute to psoriasis pathology via the secretion of IL‐23, the upstream regulator of Th17 cells, while plasmacytoid DCs are involved via IL‐36 signalling and type I interferon activation. Overall, the evidence discussed in this review indicates that IL‐23‐driven/IL‐17‐producing T cells play a critical role in psoriasis pathology and recurrence, making these cytokines logical therapeutic targets. The review also explains the clinical efficacy of IL‐17 and IL‐23 receptor blockers in the treatment of psoriasis.

Interleukin-17 family members in health and disease

The interleukin-17 (IL-17) family consists of six family members (IL-17A-IL-17F) and all the corresponding receptors have been identified recently. This family is mainly involved in the host defense mechanisms against bacteria, fungi and helminth infection by inducing cytokines and chemokines, recruiting neutrophils, inducing anti-microbial proteins and modifying T-helper cell differentiation. IL-17A and some other family cytokines are also involved in the development of psoriasis, psoriatic arthritis and ankylosing spondylitis by inducing inflammatory cytokines and chemokines, and antibodies against IL-17A as well as the receptor IL-17RA are being successfully used for the treatment of these diseases. Involvement in the development of inflammatory bowel disease, multiple sclerosis, rheumatoid arthritis and tumors has also been suggested in animal disease models. In this review, we will briefly review the mechanisms by which IL-17 cytokines are involved in the development of these diseases and discuss possible treatment of inflammatory diseases by targeting IL-17 family members.

New Insights on CD8+ T Cells in Inflammatory Bowel Disease and Therapeutic Approaches

CD8⁺ T cells are involved in the pathogenesis of inflammatory bowel disease (IBD), a complex multifactorial chronic disease. Here, we present an overview of the current research with the controversial findings of CD8⁺ T cell subsets and discuss some possible perspectives on their therapeutic value in IBD. Studies on the role of CD8⁺ T cells in IBD have contradictory outcomes, which might be related to the heterogeneity of the cells. Recent data suggest that cytotoxic CD8⁺ T cells (Tc1) and interleukin (IL) 17-producing CD8⁺ (Tc17) cells contribute to the pathogenesis of IBD. Moreover, subsets of regulatory CD8⁺ T cells are abundant at sites of inflammation and can exhibit pro-inflammatory features. Some subsets of tissue resident memory CD8⁺ T cells (Trm) might be immunosuppressant, whereas others might be pro-inflammatory. Lastly, exhausted T cells might indicate a positive outcome for patients. The function and plasticity of different subsets of CD8⁺ T cells in health and IBD remain to be further investigated in a challenging field due to the limited availability of mucosal samples and adequate controls.

Regulation of IL-17A-Producing Cells in Skin Inflammatory Disorders

This review focuses on the IL-17A family of cytokines produced by T lymphocytes and other immune cells and how they are involved in cutaneous pathogenic responses. It will also discuss cutaneous dysbiosis and FOXP3⁺ regulatory T cells in the context of inflammatory conditions linked to IL-17 responses in the skin. Specifically, it will review key literature on chronic mucocutaneous candidiasis and psoriasis.

Single-cell RNA sequencing of psoriatic skin identifies pathogenic Tc17 cell subsets and reveals distinctions between CD8+ T cells in autoimmunity and cancer

BACKGROUND

Psoriasis is an inflammatory, IL-17-driven skin disease in which autoantigen-induced CD8⁺ T cells have been identified as pathogenic drivers.

OBJECTIVE

Our study focused on comprehensively characterizing the phenotypic variation of CD8⁺ T cells in psoriatic lesions.

METHODS

We used single-cell RNA sequencing to compare CD8⁺ T-cell transcriptomic heterogeneity between psoriatic and healthy skin.

RESULTS

We identified 11 transcriptionally diverse CD8⁺ T-cell subsets in psoriatic and healthy skin. Among several inflammatory subsets enriched in psoriatic skin, we observed 2 Tc17 cell subsets that were metabolically divergent, were developmentally related, and expressed CXCL13, which we found to be a biomarker of psoriasis severity and which achieved comparable or greater accuracy than IL17A in a support vector machine classifier of psoriasis and healthy transcriptomes. Despite high coinhibitory receptor expression in the Tc17 cell clusters, a comparison of these cells with melanoma-infiltrating CD8⁺ T cells revealed upregulated cytokine, cytolytic, and metabolic transcriptional activity in the psoriatic cells that differed from an exhaustion program.

CONCLUSION

Using high-resolution single-cell profiling in tissue, we have uncovered the diverse landscape of CD8⁺ T cells in psoriatic and healthy skin, including 2 nonexhausted Tc17 cell subsets associated with disease severity.

The Association Between Psoriasis and Cardiovascular Diseases

Cardiovascular diseases and psoriasis have been well established as separate entities, however, there is uncertainty with regards to a link between the two diseases. A few environmental, psychological and social factors have been implicated as potential common risk factors that may exacerbate the two diseases, and an array of complex immune and non-immune inflammatory mediators can potentially explain a plausible link. Pharmacotherapy has also played a role in establishing a potential association, especially with the advent of biological agents which directly act on inflammatory factors shared by the two diseases. This review will look at existing evidence and ascertain a potential correlation between the two.

Anti-IL-17 Agents in the Treatment of Axial Spondyloarthritis

Axial spondyloarthritis (axSpA) describes a group of chronic inflammatory rheumatic diseases primarily involving the axial skeleton. IL-17 is involved in the pathogenesis of numerous inflammatory diseases, including inflammatory arthritis. Until a few years ago, the only biological agents licensed for the treatment of axSpA and nr-axSpA were TNF inhibitors. However, as some patients did not respond to TNF inhibition or experienced secondary failure, the introduction of the first two IL-17 inhibitors (secukinumab [SEC] and ixekizumab [IXE]) has extended the treatment options, and there are now three others (bimekizumab, brodalumab and netakimab) in various stages of clinical development. The last ten years have seen the development of a number of therapeutic recommendations that aimed at improving the management of axSpA patients. The aim of this narrative review of the published literature concerning the role of IL-17 in the pathogenesis of SpA, and the role of IL-17 inhibitors in the treatment of axSpA, is to provide a comprehensive picture of the clinical efficacy and safety of the drugs themselves, and the treatment strategies recommended in the international guidelines.

Drivers of Inflammation in Psoriatic Arthritis: the Old and the New

PURPOSE OF REVIEW

The recognition that IL-17 is produced by many lymphoid-like cells other than CD4+ T helper (Th17) cells raises the potential for new pathogenic pathways in IBD/psoriasis/SpA. We review recent knowledge concerning the role of unconventional and conventional lymphocytes expressing IL-17 in human PsA and axSpA.

RECENT FINDINGS

Innate-like lymphoid cells, namely gamma delta (γδ) T-cells, invariant natural killer T (iNKT) cells and mucosal-associated invariant T (MAIT) cells, together with innate lymphoid cells (ILCs) are found at sites of disease in PsA/SpA. These cells are often skewed to Type-17 profiles and may significantly contribute to IL-17 production. Non-IL-23 dependent IL-17 production pathways, utilising cytokines such as IL-7 and IL-9, also characterise these cells. Both conventional CD4 and CD8 lymphocytes show pathogenic phenotypes at sites of disease. A variety of innate-like lymphoid cells and conventional lymphocytes contribute towards IL-17-mediated pathology in PsA/SpA. The responses of these cells to non-conventional immune and non-immune stimuli may explain characteristic clinical features of these diseases and potential therapeutic mechanisms of therapies such as Jak inhibitors.

Immune responses and therapeutic options in psoriasis

Psoriasis is a chronic inflammatory disease of the skin that affects about 2-3% of the population and greatly impairs the quality of life of affected individuals. Psoriatic skin is characterized by excessive proliferation and aberrant differentiation of keratinocytes, as well as redness caused by increased dilation of the dermal blood vessels and infiltration of immune cells. Although the pathogenesis of psoriasis has not yet been completely elucidated, it is generally believed to arise from a complex interplay between hyperproliferating keratinocytes and infiltrating, activated immune cells. So far, the exact triggers that elicit this disease are still enigmatic, yet, it is clear that genetic predisposition significantly contributes to the development of psoriasis. In this review, we summarize current knowledge of important cellular and molecular mechanisms driving the initiation and amplification stages of psoriasis development, with a particular focus on cytokines and emerging evidence illustrating keratinocyte-intrinsic defects as key drivers of inflammation. We also discuss mouse models that have contributed to a better understanding of psoriasis pathogenesis and the preclinical development of novel therapeutics, including monoclonal antibodies against specific cytokines or cytokine receptors that have revolutionized the treatment of psoriasis. Future perspectives that may have the potential to push basic research and open up new avenues for therapeutic intervention are provided.

Interleukin-22 Influences the Th1/Th17 Axis

Interleukin-22 (IL-22) is secreted by a wide range of immune cells and its downstream effects are mediated by the IL-22 receptor, which is present on non-immune cells in many organs throughout the body. IL-22 is an inflammatory mediator that conditions the tissue compartment by upregulating innate immune responses and is also a homeostatic factor that promotes tissue integrity and regeneration. Interestingly, the IL-22 system has also been linked to many T cell driven inflammatory diseases. Despite this, the downstream effects of IL-22 on the adaptive immune system has received little attention. We have reviewed the literature for experimental data that suggest IL-22 mediated effects on T cells, either transduced directly or via mediators expressed by innate immune cells or non-immune cells in response to IL-22. Collectively, the reviewed data indicate that IL-22 has a hitherto unappreciated influence on T helper cell polarization, or the secretion of signature cytokines, that is context dependent but in many cases results in a reduction of the Th1 type response and to some extent promotion of regulatory T cells. Further studies are needed that specifically address these aspects of IL-22 signaling, which can benefit the understanding and treatment of a wide range of diseases.

Recent advances on the role of cytotoxic T lymphocytes in the pathogenesis of spondyloarthritis

Spondyloarthritis (SpA) is a chronic inflammatory disorder with complex etiology and pathogenesis. Its pathogenesis likely involves a combination of different factors. These factors include host genetics, environmental triggers, and immune and microbiota dysregulation. One of the strongest genetic associations with SpA is HLA-B27, implicating the involvement of cytotoxic T lymphocytes (CTLs) in SpA pathogenesis. Despite this discovery dating back decades ago, the CTL compartment that underlies SpA inflammation has yet to be fully defined until recently. Indeed, recent published studies support a significant role that CTLs play in contributing to chronic joint inflammation, which is a hallmark of SpA pathology. In this review chapter, we discuss emerging evidence that supports a newfound role of CTLs in SpA pathogenesis. This emerging evidence includes enrichment of CTL-related genes from genome-wide association studies, overrepresentation of pathogenic synovial CTL phenotype, clonal expansion, and immune dysregulation of CTLs. The discoveries of this mounting evidence suggest that CTL homeostasis is altered, and a disrupted adaptive immunity underlies the chronic inflammatory features seen in SpA pathology.

T cell epitope mapping of secukinumab and ixekizumab in healthy donors

Secukinumab, a human monoclonal antibody that selectively neutralizes IL-17A, has consistently shown low anti-drug antibody responses in patients with psoriasis, psoriatic arthritis, and ankylosing spondylitis. Secukinumab has also shown lower in vitro immunogenicity potential compared with other monoclonal antibodies used to treat psoriasis and psoriatic arthritis, and a significantly lower in vitro T cell precursor frequency compared with ixekizumab, which targets the same antigen. Here, secukinumab and ixekizumab were further examined regarding their specific T cell epitopes. Secukinumab- or ixekizumab-specific CD4 T cell lines were generated from 31 healthy, treatment-naïve donors via 28-day co-culture with mature monocyte-derived dendritic cells exposed to either antibody. Consistent with previous data, the frequency of preexisting T cells to secukinumab was significantly lower as compared with ixekizumab. Only two T cell lines from two different donors could be derived for secukinumab, but no specific T cell epitope was identified. In contrast, 32 T cell lines from eight donors were obtained for ixekizumab. For 11 of these T cell lines, the specific T cell epitopes could be identified and confirmed by major histocompatibility complex–associated peptide proteomics as being naturally presented peptides. All identified T cell epitopes cluster in four main regions that are overlapping with the complementarity-determining regions HCDR3, LCDR1, LCDR2 and LCDR3. Interestingly, ixekizumab CDRs contain amino acids that are not found in any of the germline family members. These amino acids may be associated with the higher number of T cell epitopes identified for ixekizumab light chain and may contribute to the increased in vitro immunogenicity potential observed for ixekizumab vs. secukinumab.

Galectin-7 downregulation in lesional keratinocytes contributes to enhanced IL-17A signaling and skin pathology in psoriasis

Psoriasis is a chronic inflammatory skin disease characterized by inflammatory cell infiltration, as well as hyperproliferation of keratinocytes in skin lesions, and is considered a metabolic syndrome. We found that the expression of galectin-7 is reduced in skin lesions of patients with psoriasis. IL-17A and TNF-α, 2 cytokines intimately involved in the development of psoriatic lesions, suppressed galectin-7 expression in human primary keratinocytes (HEKn cells) and the immortalized human keratinocyte cell line HaCaT. A galectin-7 knockdown in these cells elevated the production of IL-6 and IL-8 and enhanced ERK signaling when the cells were stimulated with IL-17A. Galectin-7 attenuated IL-17A-induced production of inflammatory mediators by keratinocytes via the microRNA-146a/ERK pathway. Moreover, galectin-7-deficient mice showed enhanced epidermal hyperplasia and skin inflammation in response to intradermal IL-23 injection. We identified fluvastatin as an inducer of galectin-7 expression by connectivity map analysis, confirmed this effect in keratinocytes, and demonstrated that fluvastatin attenuated IL-6 and IL-8 production induced by IL-17A. Thus, we validate a role of galectin-7 in the pathogenesis of psoriasis, in both epidermal hyperplasia and keratinocyte-mediated inflammatory responses, and formulate a rationale for the use of statins in the treatment of psoriasis.

SLAMF7 and IL-6R define distinct cytotoxic versus helper memory CD8+ T cells

The prevailing ‘division of labor’ concept in cellular immunity is that CD8⁺ T cells primarily utilize cytotoxic functions to kill target cells, while CD4⁺ T cells exert helper/inducer functions. Multiple subsets of CD4⁺ memory T cells have been characterized by distinct chemokine receptor expression. Here, we demonstrate that analogous CD8⁺ memory T-cell subsets exist, characterized by identical chemokine receptor expression signatures and controlled by similar generic programs. Among them, Tc2, Tc17 and Tc22 cells, in contrast to Tc1 and Tc17 + 1 cells, express IL-6R but not SLAMF7, completely lack cytotoxicity and instead display helper functions including CD40L expression. CD8⁺ helper T cells exhibit a unique TCR repertoire, express genes related to skin resident memory T cells (T_RM) and are altered in the inflammatory skin disease psoriasis. Our findings reveal that the conventional view of CD4⁺ and CD8⁺ T cell capabilities and functions in human health and disease needs to be revised.

We classically consider the T cell compartment divided into cytotoxic CD8⁺ T cells and multiple, different helper CD4⁺ T cell subsets. Here the authors demonstrate that distinct memory CD8⁺ T cell subsets phenotypically inhabit CD4⁺ T cell like populations including some with helper-like characteristics.

Involvement of the cytokine TWEAK in the pathogenesis of psoriasis vulgaris, pustular psoriasis, and erythrodermic psoriasis

Psoriasis is a common chronic inflammatory dermatitis in which various cytokines play a detrimental role. The cytokine tumor necrosis factor-related weak inducer of apoptosis (TWEAK) is involved in the pathogenesis of multiple inflammatory disorders. However, the potential role of TWEAK in various subtypes of psoriasis has not been studied in depth. To investigate whether the levels of TWEAK are associated with clinical traits and the levels of some known psoriasis-related cytokines, such as interleukin (IL)-17A, IL-22, interferon (IFN)-γ, and IL-36γ, 20 patients with psoriasis vulgaris (PV), 8 patients with pustular psoriasis (PP), 8 patients with erythrodermic psoriasis (EP), and 20 healthy controls (HCs) were recruited into this study. The levels of serum cytokines were detected by commercial enzyme-linked immunosorbent assay kits. The average levels of TWEAK, IL-17A, IL-22, IFN-γ, and IL-36γ were significantly higher in the psoriasis groups than in the HC group. Furthermore, there was a statistically significant correlation between TWEAK and IL-17A/IFN-γ in PV and IL-36γ in EP, but there was no correlation between TWEAK and IL-22 in any subtype of psoriasis. This study suggests that TWEAK may have a role in the pathogenesis of PV, PP, and EP via synergy with IL-17A, IFN-γ, or IL-36γ, but not with IL-22.

Differential Skewing of Circulating MR1-Restricted and γδ T Cells in Human Psoriasis Vulgaris

Psoriasis vulgaris (PV) is a chronic, recurrent inflammatory dermatosis mediated by aberrantly activated immune cells. The role of the innate-like T cells, particularly gammadelta T (γδT) cells and MR1-restricted T lymphocytes, is incompletely explored, mainly through animal models, or by use of surrogate lineage markers, respectively. Here, we used case-control settings, multiparameter flow cytometry, 5-OP-RU-loaded MR1-tetramers, Luminex technology and targeted qRT-PCR to dissect the cellular and transcriptional landscape of γδ and MR1-restricted blood T cells in untreated PV cases (n=21, 22 matched controls). High interpersonal differences in cell composition were observed, fueling transcriptional variability at healthy baseline. A minor subset of canonical CD4+CD8+MR1-tet+TCRVα7.2+ and CD4+CD8-MR1-tet+TCRVα7.2+ T cells was the most significantly underrepresented community in male PV individuals, whereas Vδ2+ γδ T cells expressing high levels of TCR and Vδ1-δ2- γδ T cells expressing intermediate levels of TCR were selectively enriched in affected males, partly reflecting disease severity. Our findings highlight a formerly unappreciated skewing of human circulating MAIT and γδ cytomes during PV, and reveal their compositional changes in relation to sex, CMV exposure, serum cytokine content, BMI, and inflammatory burden. Complementing numerical alterations, we finally show that flow-sorted, MAIT and γδ populations exhibit divergent transcriptional changes in mild type I psoriasis, consisting of differential bulk expression for signatures of cytotoxicity/type-1 immunity (EOMES, RUNX3, IL18R), type-3 immunity (RORC, CCR6), and T cell innateness (ZBTB16).

The IL-23/IL-17 Pathway in Inflammatory Skin Diseases: From Bench to Bedside

Interleukin-17 (IL-17) is an essential proinflammatory cytokine, which is mainly secreted by the CD4⁺ helper T cells (Th17 cells) and subsets of innate lymphoid cells. IL-17A is associated with the pathogenesis of inflammatory diseases, including psoriasis, atopic dermatitis, hidradenitis suppurativa, alopecia areata, pityriasis rubra pilaris, pemphigus, and systemic sclerosis. Interleukin-23 (IL-23) plays a pivotal role in stimulating the production of IL-17 by activating the Th17 cells. The IL-23/IL-17 axis is an important pathway for targeted therapy for inflammatory diseases. Emerging evidence from clinical trials has shown that monoclonal antibodies against IL-23, IL-17, and tumor necrosis factor are effective in the treatment of patients with psoriasis, atopic dermatitis, hidradenitis suppurativa, pityriasis rubra pilaris, pemphigus, and systemic sclerosis. Here, we summarize the latest knowledge about the biology, signaling, and pathophysiological functions of the IL-23/IL-17 axis in inflammatory skin diseases. The currently available biologics targeting the axis is also discussed.

Pathogenesis of psoriasis in the "omic" era. Part IV. Epidemiology, genetics, immunopathogenesis, clinical manifestation and treatment of psoriatic arthritis

Psoriatic arthritis (PsA) is a chronic, progressive, inflammatory arthropathy associated with psoriasis as well as a complex pathogenesis. Genetic and environmental factors trigger the development of the immune-mediated auto-inflammatory response in different sites: skin, bone marrow, entheses and synovial tissues. Studies of the last two decades have changed the view of PsA from a mild, non-progressive arthritis to an inflammatory systemic disease with serious health consequences, not only associated with joint dysfunction, but also with an increased risk of cardiovascular disease and socioeconomic consequences with significantly reduced quality of life. The joint damage starts early in the course of the disease, thus early recognition and treatment with modern biological treatments, which may modify the natural history and slow down progression of this debilitating disease, is essential for the patient long-term outcome.

Interleukin 22 and 6 serum concentrations decrease under long-term biologic therapy in psoriasis

Introduction

Psoriasis, affecting approximately 2% of the worldwide population, is a chronic, inflammatory skin disease in which overexpression of proinflammatory cytokines is observed. Most of the available data on the influence of antipsoriatic therapy on the cytokine serum concentration are inconsistent and based on short-term observations.

Aim

To evaluate the influence of long-term biologic therapy with tumor necrosis factor α (TNF-α) blockers (adalimumab, etanercept, infliximab) and IL-12/23 inhibitor (ustekinumab) on the level of IL-6, IL-22 in the sera of patients with psoriasis.

Material and methods

Blood samples were collected from 42 psoriatic patients in order to determine IL-6 and IL-22 serum concentrations prior to and at the 3^rd, 12^th, 24^th and 36^th month of biologic therapy. Psoriasis Activity and Severity Index (PASI) was assessed at the same time points. The control group consisted of 30 sex- and age-matched healthy volunteers.

Results

Mean PASI index at baseline was 14.49 ±3.69 and decreased significantly until the end of the observation. Mean IL-6 serum concentration decreased significantly in all study groups (p < 0.05). A statistically significant decrease in IL-22 concentrations was demonstrated during the treatment with adalimumab and infliximab but not etanercept or ustekinumab.

Conclusions

According to obtained results, IL-6 and IL-22 serum concentration may be an accurate marker of response to antipsoriatic therapy, even though not correlated with PASI index. Biologic therapy in psoriasis allows for long-term clinical improvement expressed not only by the remission of skin lesions, but also by lowering serum concentrations of pro-inflammatory interleukins.

Interleukin-17 in rheumatoid arthritis: Trials and tribulations

Interleukin-17A (IL-17A) is a pro-inflammatory cytokine with well-characterized biological effects on stromal cell activation, angiogenesis, and osteoclastogenesis. The presence of this cytokine in the inflamed joints of patients with rheumatoid arthritis (RA), together with compelling data from in vitro and experimental arthritis models demonstrating its pro-inflammatory effects, made this cytokine a strong candidate for therapeutic targeting. Clinical trials, however, have shown relatively modest success in RA as compared with other indications. Guided by recent insights in IL-17 biology, this review aims to explore possible reasons for the limited clinical efficacy of IL-17A blockade in RA, and what we can learn from these results going forward.

New Treatment Addressing the Pathogenesis of Psoriasis

Psoriasis is an immune cell-mediated inflammatory skin disease. The interleukin (IL)23/IL17 axis plays an important role in the development of psoriasis. The effectiveness of biologic treatments such as tumor necrosis factor (TNF)α inhibitors (infliximab, adalimumab, certolizumab pegol), IL23 inhibitors (ustekinumab, guselkumab, tildrakizumab, risankizumab), and IL17 inhibitors (secukinumab, ixekizumab, brodalumab) have verified these findings. Immune-related cells such as dendritic cells (DCs) and macrophages, in addition to Toll-like receptors and cytokines such as interferon (IFN)α, TNFα, IFNɤ, IL12, IL22, IL23, and IL17, are related to the pathogenesis of psoriasis. Here, we first review new insights regarding the pathogenesis of psoriasis, as it relates to DCs, Langerhans cells, macrophages, the signal transducer and activator of transcription 3 pathway, and aryl hydrocarbon receptor in cutaneous vascular endothelial cells. Based on these findings, we summarize currently available oral treatments and biologics. Furthermore, we describe a new treatment option including Janus kinase inhibitor, tyrosine kinase 2 inhibitor, modulator of sphingosine 1-phosphate receptor 1, and Rho-associated kinase 2 inhibitor.

Interleukin-17A Is Produced by CD4+ but Not CD8+ T Cells in Synovial Fluid Following T Cell Receptor Activation and Regulates Different Inflammatory Mediators Compared to Tumor Necrosis Factor in a Model of Psoriatic Arthritis Synovitis

OBJECTIVE

Interleukin-17A (IL-17A) and tumor necrosis factor (TNF) contribute to the pathogenesis of psoriatic arthritis (PsA). However, their functional relationship in PsA synovitis has not been fully elucidated. Additionally, although CD8+ T cells in PsA have been recognized via flow cytometry as a source of IL-17A production, it is not clear whether CD8+ T cells secrete IL-17A under more physiologically relevant conditions in the context from PsA synovitis. This study was undertaken to clarify the roles of IL-17A and TNF in the synovial fluid (SF) from patients with PsA and investigate the impact of CD8+ T cells on IL-17A production.

METHODS

IL-17A+ T cells were identified by flow cytometry in SF samples from 20 patients with active PsA, blood samples from 22 treatment-naive patients with PsA, and blood samples from 22 healthy donors. IL-17A+ T cells were sorted from 12 PsA SF samples and stimulated using anti-CD3/anti-CD28 or phorbol myristate acetate (PMA) and ionomycin ex vivo, alone (n = 3) or together with autologous monocytes (n = 3) or PsA fibroblast-like synoviocytes (FLS) (n = 5-6). To evaluate the differential allogeneic effects of neutralizing IL-17A and TNF, SF CD4+ T cells and PsA FLS cocultures were also used (n = 5-6).

RESULTS

Flow cytometry analyses of SF samples from patients with PsA showed IL-17A positivity for CD4+ and CD8+ T cells (IL-17A, median 0.71% [interquartile range 0.35-1.50%] in CD4+ cells; median 0.44% [interquartile range 0.17-1.86%] in CD8+ T cells). However, only CD4+ T cells secreted IL-17A after anti-CD3/anti-CD28 activation, when cultured alone and in cocultures with PsA monocytes or PsA FLS (each P < 0.05). Remarkably, CD8+ T cells only secreted IL-17A after 4- or 72-hour stimulation with PMA/ionomycin. Anti-IL-17A and anti-TNF treatments both inhibited PsA synovitis ex vivo. Neutralizing IL-17A strongly inhibited IL-6 (P < 0.05) and IL-1β (P < 0.01), while anti-TNF treatment was more potent in reducing matrix metalloproteinase 3 (MMP-3) (P < 0.05) and MMP-13.

CONCLUSION

CD8+ T cells, in contrast to CD4+ T cells, in SF specimens obtained from PsA patients did not secrete IL-17A following T cell receptor activation. Overlapping, but distinct, effects at the level of inflammatory cytokines and MMPs were found after neutralizing IL-17A or TNF ex vivo in a human model of PsA synovitis.