A role for CCR5(+)CD4 T cells in cutaneous psoriasis and for CD103(+) CCR4(+) CD8 Teff cells in the associated systemic inflammation

The role and therapeutic strategies for tissue-resident memory T cells, central memory T cells, and effector memory T cells in psoriasis

Psoriasis is a skin disease that is inflammatory and persistent, causing a high rate of recurrence, poor quality of life, and significant socioeconomic burden. Its main pathological manifestations are abnormal activation and infiltration of T cells and excessive proliferation of keratinocytes (KCs). The great majority of patients with psoriasis will relapse after remission. It usually lasts a lifetime and necessitates long-term treatment strategies. During periods of activity and remission, one of the main cell types in psoriasis is memory T cells, which include tissue-resident memory T (TRM) cells, central memory T (TCM) cells, and effector memory T (TEM) cells. They work by releasing inflammatory factors, cytotoxic particles, or altering cell subpopulations, leading to increased inflammation or recurrence. This review summarizes the role of memory T cells in the pathology and treatment of psoriasis, with a view to potential novel therapies and therapeutic targets.

T cells promote distinct transcriptional programs of cutaneous inflammatory disease in human skin structural cells

T cells and structural cells coordinate appropriate inflammatory responses and restoration of barrier integrity following insult. Dysfunctional T cell activity precipitates tissue pathology that occurs alongside disease-associated alterations of structural cell subsets, but the mechanisms by which T cells promote these changes remain unclear. We show that subsets of circulating and skin-resident CD4+ T cells promote distinct transcriptional outcomes in human keratinocytes and dermal fibroblasts that correspond with divergent T cell cytokine production. Using these transcriptional signatures, we identify T cell-dependent outcomes associated with inflammatory skin disease, including a set of Th17 cell-induced genes in keratinocytes that are enriched in the skin during psoriasis and normalized by anti-IL-17 therapy, and a skin-resident T cell-induced gene module enriched in scleroderma-associated fibroblasts. Interrogating clinical data using T cell-derived structural cell gene networks enables investigation of the immune-dependent contribution to inflammatory disease and the heterogeneous patient response to biologic therapy.

TLR7-dependent eosinophil degranulation links psoriatic skin inflammation to small intestinal inflammatory changes in mice

Recent evidence of gut microbiota dysbiosis in the context of psoriasis and the increased cooccurrence of inflammatory bowel disease and psoriasis suggest a close relationship between skin and gut immune responses. Using a mouse model of psoriasis induced by the Toll-like receptor (TLR) 7 ligand imiquimod, we found that psoriatic dermatitis was accompanied by inflammatory changes in the small intestine associated with eosinophil degranulation, which impaired intestinal barrier integrity. Inflammatory responses in the skin and small intestine were increased in mice prone to eosinophil degranulation. Caco-2 human intestinal epithelial cells were treated with media containing eosinophil granule proteins and exhibited signs of inflammation and damage. Imiquimod-induced skin and intestinal changes were attenuated in eosinophil-deficient mice, and this attenuation was counteracted by the transfer of eosinophils. Imiquimod levels and the distribution of eosinophils were positively correlated in the intestine. TLR7-deficient mice did not exhibit intestinal eosinophil degranulation but did exhibit attenuated inflammation in the skin and small intestine following imiquimod administration. These results suggest that TLR7-dependent bidirectional skin-to-gut communication occurs in psoriatic inflammation and that inflammatory changes in the intestine can accelerate psoriasis.

From PsO to PsA: the role of TRM and Tregs in psoriatic disease, a systematic review of the literature

Introduction

Psoriasis (PsO) is a chronic skin condition driven by immune mediators like TNFα, INFγ, IL-17, and IL-23. Psoriatic arthritis (PsA) can develop in PsO patients. Although psoriatic lesions may apparently resolve with therapy, subclinical cutaneous inflammation may persist. The role of tissue-resident memory T-cells (TRM), and regulatory T cells (Tregs) that also contribute to chronic inflammation are being explored in this context. This systematic review explores TRM and Tregs in psoriatic disease (PsD) and its progression.

Methods

A systematic review, following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, was performed using Pubmed® and Web of Science™ databases on June 3rd 2023, using patient/population, intervention, comparison, and outcomes (PICO) criteria limited to the English language.

Results

A total of 62 reports were identified and included. In PsO, chronic inflammation is driven by cytokines including IL-17 and IL-23, and cellular mediators such as CD8+ and CD4+ T cells. TRM contributes to local inflammation, while Tregs may be dysfunctional in psoriatic skin lesions. Secukinumab and guselkumab, which target IL-17A and the IL-23p19 subunit, respectively, have different effects on CD8+ TRM and Tregs during PsO treatment. Inhibition of IL-23 may provide better long-term results due to its impact on the Treg to CD8+ TRM ratio. IL-23 may contribute to inflammation persisting even after treatment. In PsA, subclinical enthesitis is perceived as an early occurence, and Th17 cells are involved in this pathogenic process. Recent EULAR guidelines highlight the importance of early diagnosis and treatment to intercept PsA. In PsA, CD8+ TRM cells are present in synovial fluid and Tregs are reduced in peripheral blood. The progression from PsO to PsA is marked by a shift in immune profiles, with specific T-cells subsets playing key roles in perpetuating inflammation. Early intervention targeting TRM cells may hold promising, but clinical studies are limited. Ongoing studies such as IVEPSA and PAMPA aim to improve our knowledge regarding PsA interception in high-risk PsO patients, emphasizing the need for further research in this area.

Conclusion

Early intervention is crucial for PsO patients at high risk of PsA; T cells, particularly type 17 helper T cells, and CD8+ cells are key in the progression from PsO-to-PsA. Early targeting of TRM in PsD shows promise but more research is needed.

The Use of Microbial Modifying Therapies to Prevent Psoriasis Exacerbation and Associated Cardiovascular Comorbidity

Psoriasis has emerged as a systemic disease characterized by skin and joint manifestations as well as systemic inflammation and cardiovascular comorbidities. Many progresses have been made in the comprehension of the immunological mechanisms involved in the exacerbation of psoriatic plaques, and initial studies have investigated the mechanisms that lead to extracutaneous disease manifestations, including endothelial disfunction and cardiovascular disease. In the past decade, the involvement of gut dysbiosis in the development of pathologies with inflammatory and autoimmune basis has clearly emerged. More recently, a major role for the skin microbiota in establishing the immunological tolerance in early life and as a source of antigens leading to cross-reactive responses towards self-antigens in adult life has also been evidenced. Gut microbiota can indeed be involved in shaping the immune and inflammatory response at systemic level and in fueling inflammation in the cutaneous and vascular compartments. Here, we summarized the microbiota-mediated mechanisms that, in the skin and gut, may promote and modulate local or systemic inflammation involved in psoriatic disease and endothelial dysfunction. We also analyze the emerging strategies for correcting dysbiosis or modulating skin and gut microbiota composition to integrate systemically existing pharmacological therapies for psoriatic disease. The possibility of merging systemic treatment and tailored microbial modifying therapies could increase the efficacy of the current treatments and potentially lower the effect on patient's life quality.

From the Skin to Distant Sites: T Cells in Psoriatic Disease

Human skin has long been known as a protective organ, acting as a mechanical barrier towards the external environment. More recent is the acquisition that in addition to this fundamental role, the complex architecture of the skin hosts a variety of immune and non-immune cells playing preeminent roles in immunological processes aimed at blocking infections, tumor progression and migration, and elimination of xenobiotics. On the other hand, dysregulated or excessive immunological response into the skin leads to autoimmune reactions culminating in a variety of skin pathological manifestations. Among them is psoriasis, a multifactorial, immune-mediated disease with a strong genetic basis. Psoriasis affects 2-3% of the population; it is associated with cardiovascular comorbidities, and in up to 30% of the cases, with psoriatic arthritis. The pathogenesis of psoriasis is due to the complex interplay between the genetic background of the patient, environmental factors, and both innate and adaptive responses. Moreover, an autoimmune component and the comprehension of the mechanisms linking chronic skin inflammation with systemic and joint manifestations in psoriatic patients is still a major challenge. The understanding of these mechanisms may offer a valuable chance to find targetable molecules to treat the disease and prevent its progression to severe systemic conditions.

Early disease intervention with guselkumab in psoriasis leads to a higher rate of stable complete skin clearance ('clinical super response'): Week 28 results from the ongoing phase IIIb randomized, double-blind, parallel-group, GUIDE study

BACKGROUND

Guselkumab is an interleukin (IL)-23 inhibitor with demonstrated efficacy in patients with psoriasis.

OBJECTIVES

Evaluate the impact of early disease intervention on clinical responses following 28 weeks of guselkumab treatment in patients with moderate-to-severe plaque psoriasis. Correlate clinical response and disease duration data with serum biomarker data.

METHODS

GUIDE is a phase IIIb randomized, double-blind, parallel-group, multicentre study of adults with moderate-to-severe plaque psoriasis. In study part 1, patients with a short disease duration (SDD [≤2 years]) or a long disease duration (LDD [>2 years]) received guselkumab 100 mg at Week (W) 0, 4, 12, and 20. Those achieving complete skin clearance at W20 and W28 were defined as a super responder (SRe). A multivariable logistic regression analysed the association between baseline factors and the likelihood of becoming an SRe. The relationship between clinical response, disease duration and serum biomarker data was assessed at W0 and 4.

RESULTS

In total, 880 patients were enrolled (SDD/LDD = 40.6%/59.4% of patients). More SDD than LDD patients achieved absolute Psoriasis Area and Severity Index (PASI) = 0 at W28 (51.8% vs. 39.4%) and were SRes (43.7% vs. 28.1% [overall 34.4%]). SDD patients also achieved PASI = 0 quicker than LDD patients (median 141 vs. 200 days). Disease duration and prior biologic use had the greatest impact on becoming an SRe, with no strong association among these independent variables. At baseline, there were no significant differences in the serum biomarker levels of IL-17A, IL-17F, IL-22 and β-defensin 2 between SDD and LDD patients, or between SRe and non-SRe patients. Guselkumab rapidly decreased these markers of systemic inflammation across all patient groups analysed at W4. Guselkumab was well tolerated.

CONCLUSIONS

Guselkumab efficacy was consistent across subpopulations, on the skin and systemically. The proportion of SRes was higher in SDD than LDD patients, indicating early treatment intervention may improve clinical outcomes.

Varicella Zoster Virus infects mucosal associated Invariant T cells

Introduction

Mucosal Associated Invariant T (MAIT) cells are innate-like T cells that respond to conserved pathogen-derived vitamin B metabolites presented by the MHC class I related-1 molecule (MR1) antigen presentation pathway. Whilst viruses do not synthesize these metabolites, we have reported that varicella zoster virus (VZV) profoundly suppresses MR1 expression, implicating this virus in manipulation of the MR1:MAIT cell axis. During primary infection, the lymphotropism of VZV is likely to be instrumental in hematogenous dissemination of virus to gain access to cutaneous sites where it clinically manifests as varicella (chickenpox). However, MAIT cells, which are found in the blood and at mucosal and other organ sites, have yet to be examined in the context of VZV infection. The goal of this study was to examine any direct impact of VZV on MAIT cells.

Methods

Using flow cytometry, we interrogated whether primary blood derived MAIT cells are permissive to infection by VZV whilst further analysing differential levels of infection between various MAIT cell subpopulations. Changes in cell surface extravasation, skin homing, activation and proliferation markers after VZV infection of MAIT cells was also assessed via flow cytometry. Finally the capacity of MAIT cells to transfer infectious virus was tested through an infectious center assay and imaged via fluorescence microscopy.

Results

We identify primary blood-derived MAIT cells as being permissive to VZV infection. A consequence of VZV infection of MAIT cells was their capacity to transfer infectious virus to other permissive cells, consistent with MAIT cells supporting productive infection. When subgrouping MAIT cells by their co- expression of a variety cell surface markers, there was a higher proportion of VZV infected MAIT cells co-expressing CD4+ and CD4+/CD8+ MAIT cells compared to the more phenotypically dominant CD8+ MAIT cells, whereas infection was not associated with differences in co-expression of CD56 (MAIT cell subset with enhanced responsiveness to innate cytokine stimulation), CD27 (co-stimulatory) or PD-1 (immune checkpoint). Infected MAIT cells retained high expression of CCR2, CCR5, CCR6, CLA and CCR4, indicating a potentially intact capacity for transendothelial migration, extravasation and trafficking to skin sites. Infected MAIT cells also displayed increased expression of CD69 (early activation) and CD71 (proliferation) markers.

Discussion

These data identify MAIT cells as being permissive to VZV infection and identify impacts of such infection on co- expressed functional markers.

CCR4+ CD8+ T cells clonally expand to differentiated effectors in murine psoriasis and in human psoriatic arthritis

Psoriasis is a chronic inflammatory skin disease with an autoimmune component and associated with joint inflammation in up to 30% of cases. To investigate autoreactive T cells, we developed an imiquimod-induced psoriasis-like inflammation model in K5-mOVA.tg C57BL/6 mice expressing ovalbumin (OVA) on the keratinocyte membrane, adoptively transferred with OT-I OVA-specific CD8⁺ T cells. We evaluated the expansion of OT-I CD8⁺ T cells and their localization in skin, blood, and spleen. scRNA-seq and TCR sequencing data from patients with psoriatic arthritis were also analyzed. In the imiquimod-treated K5-mOVA.tg mouse model, OT-I T cells were markedly expanded in the skin and blood at early time points. OT-I T cells in the skin showed mainly CXCR3⁺ effector memory phenotype, whereas in peripheral blood there was an expansion of CCR4⁺ CXCR3⁺ OT-I cells. At a later time point, expanded OVA-specific T-cell population was found in the spleen. In patients with psoriatic arthritis, scRNA-seq and TCR sequencing data showed clonal expansion of CCR4⁺ T_CM cells in the circulation and further expansion in the synovial fluid. Importantly, there was a clonotype overlap between CCR4⁺ T_CM in the peripheral blood and CD8⁺ T-cell effectors in the synovial fluid. This mechanism could play a role in the generation and spreading of autoreactive T cells to the synovioentheseal tissues in psoriasis patients at risk of developing psoriatic arthritis.

Emerging Concepts of Tissue-resident Memory T Cells in Transplantation

In this review, we summarize and discuss recent advances in understanding the characteristics of tissue-resident memory T cells (TRMs) in the context of solid organ transplantation (SOT). We first introduce the traditionally understood noncirculating features of TRMs and the key phenotypic markers that define this population, then provide a detailed discussion of emerging concepts on the recirculation and plasticity of TRM in mice and humans. We comment on the potential heterogeneity of transient, temporary resident, and permanent resident T cells and potential interchangeable phenotypes between TRM and effector T cells in nonlymphoid tissues. We review the literature on the distribution of TRM in human nonlymphoid organs and association of clinical outcomes in different types of SOT, including intestine, lung, liver, kidney, and heart. We focus on both tissue-specific and organ-shared features of donor- and recipient-derived TRMs after transplantation whenever applicable. Studies with comprehensive sample collection, including longitudinal and cross-sectional controls, and applied advanced techniques such as multicolor flow cytometry to distinguish donor and recipient TRMs, bulk, and single-cell T-cell receptor sequencing to track clonotypes and define transcriptome profiles, and functional readouts to define alloreactivity and proinflammatory/anti-inflammatory activities are emphasized. We also discuss important findings on the tissue-resident features of regulatory αβ T cells and unconventional γδ T cells after transplantation. Understanding of TRM in SOT is a rapidly growing field that urges future studies to address unresolved questions regarding their heterogeneity, plasticity, longevity, alloreactivity, and roles in rejection and tolerance.

Combined Single Cell Transcriptome and Surface Epitope Profiling Identifies Potential Biomarkers of Psoriatic Arthritis and Facilitates Diagnosis via Machine Learning

Early diagnosis of psoriatic arthritis (PSA) is important for successful therapeutic intervention but currently remains challenging due, in part, to the scarcity of non-invasive biomarkers. In this study, we performed single cell profiling of transcriptome and cell surface protein expression to compare the peripheral blood immunocyte populations of individuals with PSA, individuals with cutaneous psoriasis (PSO) alone, and healthy individuals. We identified genes and proteins differentially expressed between PSA, PSO, and healthy subjects across 30 immune cell types and observed that some cell types, as well as specific phenotypic subsets of cells, differed in abundance between these cohorts. Cell type-specific gene and protein expression differences between PSA, PSO, and healthy groups, along with 200 previously published genetic risk factors for PSA, were further used to perform machine learning classification, with the best models achieving AUROC ≥ 0.87 when either classifying subjects among the three groups or specifically distinguishing PSA from PSO. Our findings thus expand the repertoire of gene, protein, and cellular biomarkers relevant to PSA and demonstrate the utility of machine learning-based diagnostics for this disease.

Mass cytometry analysis of blood immune cells from psoriasis patients on biological therapy

Psoriasis is a chronic immune-mediated skin disease accompanied by systemic inflammation and comorbidities. We analyzed peripheral blood mononuclear cells (PBMCs) in the search for immune signatures and biomarkers related to psoriasis severity and treatment effect. Thirty-two patients with psoriasis and 10 matched healthy controls were included. PBMCs were collected before and after initiation of anti-TNF, anti-IL-17 or anti-IL-12/23 treatment and analyzed utilizing 26-parameter mass cytometry. The number of circulating Th17, Th22, Th9, and cytotoxic T cells were increased in severe psoriasis. Intracellular pp38 and pERK in T helper cells were associated with disease severity. Differences between responders and nonresponders regarding cell composition and intracellular signaling were identifiable already at inclusion. Biological treatment induced memory cells, restored inhibitory PD-1 function of T cells, and reduced a potential pro-atherogenic profile in monocytes. In conclusion, these results indicate amelioration of systemic inflammation in psoriasis after biological treatment. Such broad immune profiling may enable prospective stratification of patients regarding future treatment response. Successful early intervention may lead to a healthier trajectory with favorable implications on later comorbidities.

Interleukin-9 serves as a key link between systemic inflammation and angiogenesis in psoriasis

BACKGROUND

Psoriasis is a T helper cell-mediated chronic immune-mediated inflammatory disease affecting mainly the skin, although systemic pathological effects are also observed. Cytokine-mediated interaction between T lymphocytes and keratinocytes lead to excessive proliferation of keratinocytes, which in turn leads to formation of a proinflammatory milieu and finally to psoriatic plaque formation.

AIM

To measure interleukin (IL)-9, IL-17 and vascular endothelial growth factor (VEGF) levels in patients with psoriasis compared with controls, and to evaluate the effect of methotrexate (MTX) monotherapy on the aforesaid cytokine levels in psoriasis.

METHODS

This cohort study included 54 patients with psoriasis and 54 age- and sex-matched healthy controls (HCs). IL-9, IL-17 and VEGF levels were measured by using commercially available ELISA kits. Patients with psoriasis who were on MTX monotherapy were followed up for a period of 3 months.

RESULTS

Patients with psoriasis had increased levels of IL-9, IL-17 and VEGF at baseline, compared with the HC group. After 3 months of MTX monotherapy, Psoriasis Area Severity Index (PASI), Dermatology Life Quality Index (DLQI) and levels of cytokines (IL-9, IL-17 and VEGF) were significantly decreased compared with baseline. PASI and DLQI at baseline also showed a positive correlation with IL-9, IL-17 and VEGF.

CONCLUSION

Our results suggest the existence of a proinflammatory milieu in psoriasis, with increased levels of IL-9, IL-17 and the proangiogenic growth factor VEGF, showing an increasing trend with increasing disease severity and impaired quality of life (QoL). MTX treatment helps to reduce levels of IL-9, IL-17 and VEGF, thereby limiting disease progression and improving QoL in psoriasis.

Different epigenome regulation and transcriptome expression of CD4+ and CD8+ T cells from monozygotic twins discordant for psoriasis

OBJECTIVES

Psoriasis is an immunodeficient skin disorder, and its exact pathogenesis is unclear. Monozygotic twins are presumed to be genetically identical, and their phenotypic differences may be due to transcriptional regulation or epigenome factors. To explain the inconsistency between twins, we have collected 3 pairs of monozygotic twins who are discordant for psoriasis.

METHODS

Reduced representation of bisulfite sequencing and RNA sequencing was conducted using the peripheral blood of the twins to find the genes playing important roles in psoriasis pathogenesis.

RESULTS

As a result, we found methylation diversity in four genes (MAST3, MTOR, PM20D1 and ZNF99), and we also found 9 differentially expressed genes (PPAN-P2RY11, PIGV, RPS18, TMEM121, KIF21A, KCNH2, WNT10B, PRX and CDH24) by RNA sequencing. According to the conjoint analysis of methylation and the mRNA results, PTPN6, CCL5, NFATC1 and PRF1 were found to be closely related to psoriasis. We then annotated the genes to explore the associations between these genes and psoriasis.

CONCLUSIONS

These findings provide a better understanding of psoriasis that can improve the diagnosis and treatment of the disease.

Advances in the role of helper T cells in autoimmune diseases

Autoimmune diseases are primary immune diseases in which autoreactive antibodies or sensitized lymphocytes destroy and damage tissue and cellular components, resulting in tissue damage and organ dysfunction. Helper T cells may be involved in the pathogenesis of autoimmune diseases under certain conditions. This review summarizes recent research on the role of helper T cells in autoimmune diseases from two aspects, helper T cell-mediated production of autoantibodies by B cells and helper T cell-induced activation of abnormal lymphocytes, and provides ideas for the treatment of autoimmune diseases. The abnormal expression of helper T cells promotes the differentiation of B cells that produce autoantibodies, which leads to the development of different diseases. Among them, abnormal expression of Th2 cells and T follicular helper cells is more likely to cause antibody-mediated autoimmune diseases. In addition, abnormal activation of helper T cells also mediates autoimmune diseases through the production of abnormal cytokines and chemokines. Helper T cells play an essential role in the pathogenesis of autoimmune diseases, and a full understanding of their role in autoimmune diseases is helpful for providing ideas for the treatment of autoimmune diseases.

CCR4+ Skin-Tropic Phenotype as a Feature of Central Memory CD8+ T Cells in Healthy Subjects and Psoriasis Patients

The chemokine receptor CCR4 has emerged as a skin-homing molecule important for the migration of T cells from the blood to the dermis. From our previous data on psoriasis patients, CCR4⁺ memory T cells emerged as a putative recirculating population between skin and blood. Here we focused our attention on the expression of CCR4 and skin-tropic molecules in the different stages of memory T cell differentiation. We analyzed the chemokine receptor profile in CD8⁺ and CD4⁺ CD45RA^-CCR7⁺ (T_CM) and CD45RA^-CCR7^- (T_EM) cells. Subpopulations were further divided on the basis of CD62L expression, and the distribution among the subsets of the skin-homing molecule CLA (Cutaneous Lymphocyte Antigen) was evaluated. The characterization was performed on peripheral blood mononuclear cells isolated from 21 healthy subjects and 24 psoriasis patients. The results indicate that (i) the skin-homing CCR4 marker is mainly expressed in T_CM cells, (ii) CCR4⁺ T_CM cells also express high level of CLA and that (iii) the more differentiated phenotype T_EM expresses CXCR3 and CCR5 but lower level of CCR4 and CLA. This indicates that progressive stages of memory T cell differentiation have profoundly different chemokine receptor patterns, with CD8⁺ T_CM displaying a marked skin-tropic phenotype CLA⁺CCR4⁺. Differential skin-tropic phenotype between T_CM and T_EM cells was observed in both healthy subjects and psoriasis patients. However, patients showed an expanded circulating population of CD8⁺ T_CM cells with phenotype CCR4⁺CXCR3⁺ that could play a role in the pathophysiology of psoriasis and possibly in disease recurrence.

Immunological Memory of Psoriatic Lesions

The natural course of psoriasis is the appearance of new lesions in the place of previous ones, which disappeared after a successful therapy. Recent studies of psoriasis etiopathogenesis showed that after psoriatic plaques have disappeared, in healthy skin we can still find a trace of inflammation in the form of tissue resident memory cells (TRM). They are originally responsible for protection against viral and bacterial infections in non-lymphatic tissues. In psoriatic inflammation, they are characterized by heterogeneity depending on their origin. CD8+ T cells TRM are abundantly present in psoriatic epidermis, while CD4+ TRM preferentially populate the dermis. In psoriasis, epidermal CD8+ TRM cells express CLA, CCR6, CD103 and IL-23R antigen and produce IL-17A during ex vivo stimulation. However, CD4+ CD103+ TRM can also colonize the epidermis and produce IL-22 during stimulation. Besides T cells, Th22 and epidermal DCs proved that epidermal cells in healed skin were still present and functioning after several years of disease remission. It explains the clinical phenomenon of the tendency of psoriatic lesions to relapse in the same location and it allows to develop new therapeutic strategies in the future.

Increased frequency of activated CD8+ T cell effectors in patients with psoriatic arthritis

The aim of this study is to identify subsets of T cells differentially represented in the circulation of patients with psoriatic arthritis and to evaluate the possibility that they can recirculate between peripheral blood and the inflamed joints. We analyzed the phenotype and cytokine expression in circulating CD8+ and CD4+ T cells in 69 subjects: 28 with cutaneous psoriasis, 15 patients with psoriatic arthritis, and 26 healthy subjects. In the circulation, the percentage of each subset was compared among the groups and correlation was calculated with the serum concentration of C-reactive protein. To investigate the migration of T cells towards the inflamed joints, we performed a transwell migration assay towards patient serum and synovial fluid. In selected patients we analyzed in parallel T cells from peripheral blood and from synovial fluid. In the circulation, we found increased percentage of CD8+ CCR6+ T cell effectors expressing CD69 and of IL-17-producing T cells in patients with psoriatic arthritis. CD8+ effector/effector memory T cells showed increased migration towards synovial fluid. Finally, in synovial fluid we found accumulation of CXCR3+ CD8+ T cells and CD69+ cells. CD4+ T cells in the two compartments shared many similarities with CD8+ T cells. The results indicate a role for memory T cell effectors in systemic and joint manifestations of psoriatic arthritis.

Lymphocyte mass cytometry identifies a CD3-CD4+ cell subset with a potential role in psoriasis

Psoriasis (PS) is a systemic, immune-mediated inflammatory disorder. However, the whole lymphocyte compartment and the potential pathologies of PS have not been fully characterized. In the present study, we examined whole lymphocyte subsets and signal transduction proteins using high-dimensional single-cell mass cytometry and a bioinformatics pipeline for an in-depth characterization of the immune cell subsets and protein profiles involved in pathways in the peripheral blood of patients with PS. We identified 15 major immune cell populations in T cell lineages and characterized various CD3+CD4+ Th and CD3+CD8+ T cytotoxic cell populations simultaneously across 24 leukocyte markers and 7 proteins related to the signal transduction pathways. High-dimensional analysis identified 3 new subsets that are abundant in PS peripheral blood, resembling CD3-CD4+ lymphoid tissue inducer cells, Tc17 cells, and CD8+CXCR3+ Tregs. We confirmed the CD3-CD4+ cells, and their features and functions, in an independent PS cohort. The use of single-cell mass cytometry allows systemic-level characterization of lymphocyte subpopulations and dysregulated signaling pathways in the blood of patients with PS, identifying abnormalities of different immune cell subsets. We validated that the CD3-CD4+ cells had elevated OX40 and decreased FRA2 expression, which were positively associated with the PS area and severity index.

T Cell Hierarchy in the Pathogenesis of Psoriasis and Associated Cardiovascular Comorbidities

The key role of T cells in the pathogenesis of cutaneous psoriasis has been well described in the last decade and the knowledge of the relative role of the different subsets of T cells in psoriasis pathogenesis has considerably evolved. Now, it is clear that IL-17A-producing T cells, including Th17/Tc17, have a central role in the pathogenesis of cutaneous psoriasis and therapies blocking the IL-17A pathway show high clinical efficacy. By contrast, the contribution of IFNγ-producing T cells has progressively become less clear because of the lack of efficacy of anti-IFNγ antibodies in clinical studies. In parallel, the role of CD8⁺ T cells specific for self-antigens has been revived and increasing evidence now indicates that in psoriatic skin the majority CD8⁺ T cells are present in the form of epidermal tissue-resident memory T cells. In the last years it also emerged the possibility of a contribution of T cell recirculation in the pathogenesis of psoriasis and its systemic manifestations. The aim of this review is to define a hierarchy for the different subsets of T cells in the T cell-mediated inflammatory cascade in psoriatic skin. This analysis will possibly help to distinguish the subsets that initiate the disease, those involved in the establishment of the self-sustaining amplification loop that leads to the cutaneous clinical manifestations and finally the subsets that act as downstream players in established lesions. Specific T cell subpopulations finally will be considered for their possible role in propagating inflammation at distant sites and for representing a link with systemic inflammation and cardiovascular comorbidities.

Autoimmunity in 2016

The number of peer-reviewed articles published during the 2016 solar year and retrieved using the "autoimmunity" key word remained stable while gaining a minimal edge among the immunology articles. Nonetheless, the quality of the publications has been rising significantly and, importantly, acquisitions have become available through scientific journals dedicated to immunology or autoimmunity. Major discoveries have been made in the fields of systemic lupus erythematosus, rheumatoid arthritis, autoimmunity of the central nervous system, vasculitis, and seronegative spondyloarthrithritides. Selected examples include the role of IL17-related genes and long noncoding RNAs in systemic lupus erythematosus or the effects of anti-pentraxin 3 (PTX3) in the treatment of this paradigmatic autoimmune condition. In the case of rheumatoid arthritis, there have been reports of the role of induced regulatory T cells (iTregs) or fibrocytes and T cell interactions with exciting implications. The large number of studies dealing with neuroimmunology pointed to Th17 cells, CD56(bright) NK cells, and low-level TLR2 ligands as involved in multiple sclerosis, along with a high salt intake or the micriobiome-derived Lipid 654. Lastly, we focused on the rare vasculitides to which numerous studies were devoted and suggested that unsuspected cell populations, including monocytes, mucosal-associated invariant T cells, and innate lymphoid cells, may be crucial to ANCA-associated manifestations. This brief and arbitrary discussion of the findings published in 2016 is representative of a promising background for developments that will enormously impact the work of laboratory scientists and physicians at an exponential rate.

The epigenetic mechanism for discordance of autoimmunity in monozygotic twins

Monozygotic twins share an identical DNA sequence but are not truly "identical". In fact, when it comes to health and disease, they may often display some level of phenotypic discordance. The cause of this discordance is often unknown. Epigenetic modifications such as DNA methylation, histone modification, and microRNAs-mediated regulation regulate gene expression and are sensitive to external stimuli. These modifications may be seen to bridge the gap between genetics and the environment. Over the years, the importance of epigenetics as a primary mechanism for the role that the environment plays in defining phenotype has been increasingly appreciated. Mechanisms of epigenetics include DNA methylation, histone modifications and microRNAs. Discordance rates in monozygotic twins vary depending on the specific condition, from 11% in SLE to 64% in psoriasis and 77% in PBC. Other autoimmune diseases in which discordance is found among monozygotic twins has also been studied include type 1 diabetes, multiple sclerosis, rheumatoid arthritis, dermatomyositis and systemic sclerosis. In some cases, the differences in various epigenetic modifications is slight, even though the concordance rate is low, suggesting that epigenetics is not the only factor that needs to be considered. Nonetheless, the study of phenotypic discordance in monozygotic twins may shed light on the pathogenesis of autoimmune diseases and contribute to the development of new methodologies for the diagnosis and treatment of these diseases.

Blood to skin recirculation of CD4+ memory T cells associates with cutaneous and systemic manifestations of psoriatic disease

Blood to skin recirculation could play a role in the pathogenesis of psoriasis. To investigate this possibility we dissected the phenotype of circulating T cells in psoriasis patients, calculated the correlation the clinical parameters of the disease and performed a parallel bioinformatics analysis of gene expression data in psoriatic skin. We found that circulating CCR6⁺ CD4⁺ T_EM and T_EFF cells significantly correlated with systemic inflammation. Conversely, the percentage of CXCR3⁺ CD4⁺ T_EM cells negatively correlated with the severity of the cutaneous disease. Importantly CLA⁺ CD4⁺ T_CM cells expressing CCR6⁺ or CCR4⁺CXCR3⁺ negatively correlated with psoriasis severity suggesting recruitment to the skin compartment. This assumption was reinforced by gene expression data showing marked increase of CCR7 and CLA-encoding gene SELPLG expression in psoriatic skin and strong association of their expression. The data enlightens a role for CD4⁺ T cells trafficking between blood and skin in cutaneous and systemic manifestations of psoriasis.

T Helper Cell Subsets in Clinical Manifestations of Psoriasis

Psoriasis is a chronic inflammatory skin disease, which is associated with systemic inflammation and comorbidities, such as psoriatic arthritis and cardiovascular diseases. The autoimmune nature of psoriasis has been established only recently, conferring a central role to epidermal CD8 T cells recognizing self-epitopes in the initial phase of the disease. Different subsets of helper cells have also been reported as key players in the psoriasis pathogenesis. Here, we reviewed the knowledge on the role of each subset in the psoriatic cascade and in the different clinical manifestations of the disease. We will discuss the role of Th1 and Th17 cells in the initiation and in the amplification phase of cutaneous inflammation. Moreover, we will discuss the recently proposed role of tissue resident Th22 cells in disease memory in sites of recurrent psoriasis and the possible involvement of Th9 cells. Finally, we will discuss the hypothesis of a link between T helper cell subsets recirculating from the skin and the systemic manifestations of psoriasis.