Functional characterization of CD4+CD25+ regulatory T cells differentiated in vitro from bone marrow-derived haematopoietic cells of psoriasis patients with a family history of the disorder

Review: A Contemporary, Multifaced Insight into Psoriasis Pathogenesis

Psoriasis is a chronic recurrent inflammatory autoimmune pathology with a significant genetic component and several interferences of immunological cells and their cytokines. The complex orchestration of psoriasis pathogenesis is related to the synergic effect of immune cells, polygenic alterations, autoantigens, and several other external factors. The major act of the IL-23/IL-17 axis, strongly influencing the inflammatory pattern established during the disease activity, is visible as a continuous perpetuation of the pro-inflammatory response and keratinocyte activation and proliferation, leading to the development of psoriatic lesions. Genome-wide association studies (GWASs) offer a better view of psoriasis pathogenic pathways, with approximately one-third of psoriasis's genetic impact on psoriasis development associated with the MHC region, with genetic loci located on chromosome 6. The most eloquent genetic factor of psoriasis, PSORS1, was identified in the MHC I site. Among the several factors involved in its complex etiology, dysbiosis, due to genetic or external stimulus, induces a burst of pro-inflammatory consequences; both the cutaneous and gut microbiome get involved in the psoriasis pathogenic process. Cutting-edge research studies and comprehensive insights into psoriasis pathogenesis, fostering novel genetic, epigenetic, and immunological factors, have generated a spectacular improvement over the past decades, securing the path toward a specific and targeted immunotherapeutic approach and delayed progression to inflammatory arthritis. This review aimed to offer insight into various domains that underline the pathogenesis of psoriasis and how they influence disease development and evolution. The pathogenesis mechanism of psoriasis is multifaceted and involves an interplay of cellular and humoral immunity, which affects susceptible microbiota and the genetic background. An in-depth understanding of the role of pathogenic factors forms the basis for developing novel and individualized therapeutic targets that can improve disease management.

High-dimensional profiling of regulatory T cells in psoriasis reveals an impaired skin-trafficking property

BACKGROUND

Psoriasis is a chronic inflammatory skin disease with a Th17-skewed immune phenotype. Although it has been generally accepted that regulatory T cells (Tregs) in lesional psoriatic skin have functional impairment due to the local inflammatory microenvironment, the molecular properties of skin-homing psoriatic Tregs have not been well explored.

METHODS

We designed an extensive 39 marker mass cytometry (CyTOF) panel to deeply profile the immune landscape of skin-homing Tregs from 31 people with psoriasis stratified by psoriasis area severity index score as mild (n = 15) to moderate-severe (n = 16) and 32 healthy controls. We further validated the findings with an in-vitro chemokine-mediated Treg migration assay, immunofluorescent imaging of normal and psoriatic lesional skin and analysed public single-cell RNA-sequencing datasets to expand upon our findings into the local tissue microenvironments.

FINDINGS

We discovered an overall decrease in CLAhi Tregs and specifically, CLAhiCCR5+ Tregs in psoriasis. Functional markers CD39 and FoxP3 were elevated in psoriatic Tregs. However, CCR7 expression was significantly increased while CCR4 and CLA expression was reduced in psoriatic Tregs and CLAhi Tregs, which was associated with disease severity. Moreover, psoriatic Tregs revealed increased migratory capacity towards CCR7's ligands, CCL19/CCL21. Interrogation of public single-cell RNA sequencing data confirmed reduced expression of skin-trafficking markers in lesional-skin Tregs compared to non-lesioned skin, further substantiated by immunofluorescent staining.

INTERPRETATION

Psoriatic circulating Tregs showed an impaired skin-trafficking phenotype thus leading to insufficient suppression of ongoing inflammation in the lesional skin, expanding upon our current understanding of the impairment of Treg-mediated immunosuppression in psoriasis.

FUNDING

This research was supported by the Basic Science Research Program through the National Research Foundation of Korea funded by the Ministry of Science and Information and Communications Technology (2020R1C1C1014513, 2021R1A4A5032185, 2020R1F1A1073692); and the new faculty research seed money grant of Yonsei University College of Medicine for 2021 (2021-32-0033).

Regulatory T cells (Tregs) and their therapeutic potential against autoimmune disorders - Advances and challenges

Autoimmune diseases are caused when immune cells act against self-protein. This biological self-non-self-discrimination phenomenon is controlled by a distinct group of lymphocytes known as regulatory T cells (Tregs), which are key inflammatory response regulators and play a pivotal role in immune tolerance and homeostasis. Treg-mediated robust immunosuppression provides self-tolerance and protection against autoimmune diseases. However, once this system fails to operate or poorly operate, it leads to an extreme situation where immune system reacts against self-antigens and destroys host organs, thus causing autoimmune diseases. Tregs can target both innate and adaptive immunity via modulating multiple immune cells such as neutrophils, monocytes, antigen-presenting cells, B cells, and T cells. This review highlights the Treg-mediated immunosuppression, role of several markers and their interplay during Treg development and differentiation, and advances in therapeutic aspects of Treg cells to reduce severity of autoimmunity-related conditions along with emphasizing limitations and challenges of their usages.

Pathogenesis, multi-omics research, and clinical treatment of psoriasis

Psoriasis is a common inflammatory skin disease involving interactions between keratinocytes and immune cells that significantly affects the quality of life. It is characterized by hyperproliferation and abnormal differentiation of keratinocytes and excessive infiltration of immune cells in the dermis and epidermis. The immune mechanism underlying this disease has been elucidated in the past few years. Research shows that psoriasis is regulated by the complex interactions among immune cells, such as keratinocytes, dendritic cells, T lymphocytes, neutrophils, macrophages, natural killer cells, mast cells, and other immune cells. An increasing number of signaling pathways have been found to be involved in the pathogenesis of psoriasis, which has prompted the search for new treatment targets. In the past decades, studies on the pathogenesis of psoriasis have focused on the development of targeted and highly effective therapies. In this review, we have discussed the relationship between various types of immune cells and psoriasis and summarized the major signaling pathways involved in the pathogenesis of psoriasis, including the PI3K/AKT/mTOR, JAK-STAT, JNK, and WNT pathways. In addition, we have discussed the results of the latest omics research on psoriasis and the epigenetics of the disease, which provide insights regarding its pathogenesis and therapeutic prospects; we have also summarized its treatment strategies and observations of clinical trials. In this paper, the various aspects of psoriasis are described in detail, and the limitations of the current treatment methods are emphasized. It is necessary to improve and innovate treatment methods from the molecular level of pathogenesis, and further provide new ideas for the treatment and research of psoriasis.

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.

Role of regulatory T cells in psoriasis pathogenesis and treatment

Psoriasis is a chronic inflammatory disease with a strong genetic component that can be triggered by environmental factors. Disease pathogenesis is mainly driven by type 1 and type 17 cytokine-producing cells which, in healthy individuals, are modulated by regulatory T cells (Tregs). Tregs play a fundamental role in immune homeostasis and contribute to the prevention of autoimmune disease by suppressing immune responses. In psoriasis, Tregs are impaired in their suppressive function leading to an altered T-helper 17/Treg balance. Although Treg dysfunction in patients with psoriasis is associated with disease exacerbation, it is unknown how they are functionally regulated. In this review, we discuss recent insights into Tregs in the setting of psoriasis with an emphasis on the effect of current treatments on Tregs and how already available therapeutics that modulate Treg frequency or functionality could be exploited for treatment of psoriasis.

Cross-sectional study reveals thatHLA-C*07:02 is a potential biomarker of early onset/lesion severityof psoriasis

Psoriasis is a common chronic autoimmune skin disease, with T cells playing a predominant role in its pathogenesis.Here, we aimed to investigate the relation of T cell repertoires (TCR) and major histocompatibility complex (MHC) in psoriatic patients to further understand mechanisms in disease pathogenesis.We conducted a cross-sectional study involving 9 pairs of monozygotic twins with inconsistent psoriasis and examined the TCR diversity and MHC haplotype ofthe individuals using multiple-PCR and high-throughput sequencing. Additionally, 665 psoriatic patients were applied to validate the relation of human leukocyte antigen (HLA)-class I allele HLA-C*07:02 and early onset or lesion severity of psoriasis.The immune diversity was lower in psoriatic patients compared with unaffected individuals within the twin pairs, although the difference was not significant.The clonotypes of TCR significantly decreased in psoriatic patients with high PASI score and early onset. HLA-C*07:02, a haplotype associated with psoriasis, was positively correlated with the diversity of the TCRV gene. Moreover, HLA-C*07:02 clustered in patients with high PASI and early onset. In the replication stage, we found that the PASI and onset age in psoriasis with HLA-C*07:02 were significantly different from those without HLA-C*07:02 and without HLA-C*06:02. Our observations indicate that HLA-C*07:02 is positively correlated with the diversity of TCRV gene in psoriasis, and maybe a potential biomarker of early onset/severe lesions of psoriasis.

Pathogenesis of psoriasis in the "omic" era. Part I. Epidemiology, clinical manifestation, immunological and neuroendocrine disturbances

Psoriasis is a common, chronic, inflammatory, immune-mediated skin disease affecting about 2% of the world's population. According to current knowledge, psoriasis is a complex disease that involves various genes and environmental factors, such as stress, injuries, infections and certain medications. The chronic inflammation of psoriasis lesions develops upon epidermal infiltration, activation, and expansion of type 1 and type 17 Th cells. Despite the enormous progress in understanding the mechanisms that cause psoriasis, the target cells and antigens that drive pathogenic T cell responses in psoriatic lesions are still unproven and the autoimmune basis of psoriasis still remains hypothetical. However, since the identification of the Th17 cell subset, the IL-23/Th17 immune axis has been considered a key driver of psoriatic inflammation, which has led to the development of biologic agents that target crucial elements of this pathway. Here we present the current understanding of various aspects in psoriasis pathogenesis.

Anti-IL-17A and IL-23p19 antibodies but not anti-TNFα antibody induce expansion of regulatory T cells and restoration of their suppressive function in imiquimod-induced psoriasiform dermatitis

BACKGROUND

Psoriasis is a chronic inflammatory skin disease. Anti-TNFα, IL-17A and IL-23p19 antibodies are effective for psoriasis. However, the contribution of regulatory T cells (Treg) in their effectiveness remains to be elucidated.

OBJECTIVE

We investigated the effects of TNFα, IL-17A and IL-23p19 inhibition on Tregs in imiquimod-induced psoriasiform dermatitis.

METHODS

Psoriasiform dermatitis was induced by imiquimod application on murine shaved back skin for six days. Mice were treated with anti-TNFα, IL-17A or IL-23p19 monoclonal antibodies every other day from one day before imiquimod application.

RESULTS

Administration of anti-TNFα, IL-17A or IL-23p19 antibodies improved the clinical score and downregulated Th17-related cytokines and chemokines, while IL-23p19 antibodies upregulated IL-10 mRNA expression. Anti-IL-17A or IL-23p19 antibody-treated imiquimod-applied mice showed a significant increase in the number of Foxp3⁺ IL-10⁺ Tregs. Recipient mice adoptively transferred with Tregs derived from donor mice treated with antibodies demonstrated clinical and pathological improvement in imiquimod-induced psoriasiform dermatitis. Anti-IL-17A or IL-23p19 antibody-induced Tregs significantly increased the number of Foxp3⁺ cells and IL-10 expression in imiquimod-induced psoriasiform dermatitis in recipient mice but anti-TNFα antibody-induced Tregs did not.

CONCLUSION

Anti-IL-17A or IL-23p19 antibody inhibits the IL-17/IL-23 signaling pathway, and induces expansion of Tregs and their suppressive capacity in imiquimod-induced psoriasiform dermatitis.

The role of regulatory T cells and genes involved in their differentiation in pathogenesis of selected inflammatory and neoplastic skin diseases. Part II: The Treg role in skin diseases pathogenesis

Regulatory FOXP3+ T cells (Tregs) constitute 5% to 10% of T cells in the normal human skin. They play an important role in the induction and maintenance of immunological tolerance. The suppressive effects of these cells are exerted by various mechanisms including the direct cytotoxic effect, anti-inflammatory cytokines, metabolic disruption, and modulation of the dendritic cells function. The deficiency of Treg cells number or function are one of the basic elements of the pathogenesis of many skin diseases, such as psoriasis, atopic dermatitis, bacterial and viral infections. They also play a role in the pathogenesis of T cell lymphomas of the skin (cutaneous T cell lymphomas - CTCL), skin tumors and mastocytosis. Here, in the second part of the cycle, we describe dysfunctions of Tregs in selected skin diseases.

Stem Cells as Potential Candidates for Psoriasis Cell-Replacement Therapy

Recent years have seen considerable progress in explaining the mechanisms of the pathogenesis of psoriasis, with a significant role played in it by the hyper-reactivity of Th1 and Th17 cells, Treg function disorder, as well as complex relationships between immune cells, keratinocytes, and vascular endothelium. The effect of stem cells in the epidermis and stem cells on T cells has been identified and the dysfunction of various types of stem cells may be a prime cause of dysregulation of the inflammatory response in psoriasis. However, exploring these mechanisms in detail could provide a chance to develop new therapeutic strategies. In this paper, the authors reviewed data on the role played by stem cells in the pathogenesis of psoriasis and initial attempts at using them in treatment.

The Inflammatory Response in Psoriasis: a Comprehensive Review

Psoriasis is a chronic inflammatory autoimmune disease characterized by an excessively aberrant hyperproliferation of keratinocytes. The pathogenesis of psoriasis is complex and the exact mechanism remains elusive. However, psoriasis is thought to result from a combination of genetic, epigenetic, and environmental influences. Recent studies have identified that epigenetic factors including dysregulated DNA methylation levels, abnormal histone modification and microRNAs expressions are involved in the development of psoriasis. The interplay of immune cells and cytokines is another critical factor in the pathogenesis of psoriasis. These factors or pathways include Th1/Th2 homeostasis, the Th17/Treg balance and the IL-23/Th17 axis. Th17 is believed particularly important in psoriasis due to its pro-inflammatory effects and its involvement in an integrated inflammatory loop with dendritic cells and keratinocytes, contributing to an overproduction of antimicrobial peptides, inflammatory cytokines, and chemokines that leads to amplification of the immune response. In addition, other pathways and signaling molecules have been found to be involved, including Th9, Th22, regulatory T cells, γδ T cells, CD8(+) T cells, and their related cytokines. Understanding the pathogenesis of psoriasis will allow us to develop increasingly efficient targeted treatment by blocking relevant inflammatory signaling pathways and molecules. There is no cure for psoriasis at the present time, and much of the treatment involves managing the symptoms. The biologics, while lacking the adverse effects associated with some of the traditional medications such as corticosteroids and methotrexate, have their own set of side effects, which may include reactivation of latent infections. Significant challenges remain in developing safe and efficacious novel targeted therapies that depend on a better understanding of the immunological dysfunction in psoriasis.

Stem cells in psoriasis

Psoriasis is a complex chronic relapsing inflammatory disease. Although the exact mechanism remains unknown, it is commonly accepted that the development of psoriasis is a result of multi-system interactions among the epidermis, dermis, blood vessels, immune system, neuroendocrine system, metabolic system, and hematopoietic system. Many cell types have been confirmed to participate in the pathogenesis of psoriasis. Here, we review the stem cell abnormalities related to psoriasis that have been investigated recently.

Characterization of Th17 and FoxP3(+) Treg Cells in Paediatric Psoriasis Patients

Psoriasis is one of the most common inflammatory skin conditions affecting both children and adults. Growing evidence indicates that T-helper 17 (Th17) cells and CD4(+) CD25(+) regulatory T (Treg) cells play an important role in the pathogenesis of psoriasis. However, the relationship between Th17 and Treg cells and their dynamic variations in paediatric psoriasis remain unclear. In this study, we found that both Th17 and FoxP3(+) Treg cells and the ratio of Th17 to Treg cell frequency in the peripheral circulation were increased in patients with paediatric psoriasis and were positively correlated with the disease severity. The function of Treg to suppress CD4(+) CD25(-) T cell proliferation and IFN-γ secretion was impaired during the onset of psoriasis. After disease remission, both the Th17 and Treg cell frequencies were decreased, and the suppressive function of the Treg cells was obviously restored. However, neither Treg cells from the disease onset nor those after remission can regulate IL-17 secretion by CD4(+) T cells. These findings will further our understanding of the associations between Th17 and Treg cells in paediatric psoriasis and their influence on disease severity.

Increased, but Functionally Impaired, CD14(+) HLA-DR(-/low) Myeloid-Derived Suppressor Cells in Psoriasis: A Mechanism of Dysregulated T Cells

The clinical extent of psoriasis pathology is regulated in part by defects in immune networks, including a defect in the suppressive actions of regulatory T cells. Recently, CD14(+) HLA-DR(-/low) monocytic myeloid-derived suppressor cells (Mo-MDSCs) have been shown to suppress T-cell activation as one of their suppressive mechanisms. However, little is known about the role of Mo-MDSCs and their functional relationship to T-cell suppression in relation to human chronic immune-mediated inflammatory diseases, including psoriasis. Despite psoriasis being a hyperinflammatory condition, Mo-MDSCs were elevated in psoriatic patient peripheral blood mononuclear cells compared to nonpsoriatic healthy controls (2.6% vs. 0.9%, P < 0.002). Freshly isolated psoriatic Mo-MDSCs directly suppressed CD8 T-cell proliferation less efficiently than healthy control Mo-MDSCs. In addition, psoriatic Mo-MDSCs expressed reduced surface expression of programmed cell death protein 1 compared to healthy controls. Additional in vitro assays also demonstrated that psoriatic and control Mo-MDSCs both induce regulatory T-cell conversion from naïve T effector cells, but, importantly, the regulatory T cells induced by psoriatic Mo-MDSCs displayed decreased suppressive functionality. These results suggest that aberrations in psoriatic Mo-MDSCs prevent proper suppression of effector T-cell expansion and hamper the immune system's ability to correctly self-regulate.

Recurrent Streptococcus agalactiae Toxic Shock Syndrome Triggered by a Tumor Necrosis Factor-α Inhibitor

Streptococcal toxic shock syndrome caused by group B streptococcus (GBS) is a rare, but lethal disease. We experienced a 45-year-old woman with pustular psoriasis who developed toxic shock-like syndrome during infliximab treatment. Surprisingly, similar episodes recurred three times in one year with restarting of infliximab treatments. In the third episode, GBS were detected in blood, urine, and vaginal secretion cultures. These episodes of shock syndrome were possibly due to GBS. To the best of our knowledge, this is the first case report of recurrent streptococcal toxic shock syndrome possibly caused by GBS which was induced by anti-TNF-α inhibitor therapy. The restarting of biological agents in patients with a history of toxic shock syndrome should therefore be avoided as much as possible.

Treg Cell Differentiation: From Thymus to Peripheral Tissue

Regulatory T cells (Tregs) are crucial mediators of self-tolerance in the periphery. They differentiate in the thymus, where interactions with thymus-resident antigen-presenting cells, an instructive cytokine milieu, and stimulation of the T cell receptor lead to the selection into the Treg lineage and the induction of Foxp3 gene expression. Once mature, Treg cells leave the thymus and migrate into either the secondary lymphoid tissues, e.g., lymph nodes and spleen, or peripheral nonlymphoid tissues. There is growing evidence that Treg cells go beyond the classical modulation of immune responses and also play important functional roles in nonlymphoid peripheral tissues. In this review, we summarize recent findings about the thymic Treg lineage differentiation as well as the further specialization of Treg cells in the secondary lymphoid and in the peripheral nonlymphoid organs.

Importance of regulatory T cells in the pathogenesis of psoriasis: review of the literature

Psoriasis is a common chronic relapsing inflammatory cutaneous disease; the main role in the inflammation of this condition is played by lymphocyte Th1, Th17 and their cytokines. The activity of these cells is modulated by a particular kind of T cells recently described: the T regulatory cells (Treg). These are able to inhibit the immunological response and to maintain the cutaneous immunological homeostasis, thus preventing autoimmunity against self antigens. Few data are available in the literature as to Treg in psoriasis; several studies demonstrate that the function of these cells is impaired in this condition and treatments for psoriasis may increase the number and activity of Treg. The role of these cells in the pathogenesis of psoriasis is very important to understand how they may contribute to the development of this cutaneous disorder. In the near future it would be possible to target therapies at these defects, improving the activity of these cells and maintaining cutaneous homeostasis, preventing psoriasis or other inflammatory cutaneous conditions.

Expression of Notch receptor and its target gene Hes-1 in bone marrow CD34+ cells from patients with psoriasis

Psoriasis is an autoimmune disease mediated mainly by dysfunctional peripheral blood T cells. Both CD4+/CD8+ T cells and CD4+CD25+ regulatory T cells derived from psoriatic CD34+ bone marrow cells in vitro have been found to be functionally similar to those psoriatic circulating and lesional T cells. Notch signaling participates in diverse cell fate decisions during T cell development and has been reported to influence the proliferation of hematopoietic stem cells and the differentiation of T cells. The purpose of this study was to investigate the expression levels of Notch receptor 1, 2 and its target gene Hes-1 in CD34+ cells from patients with psoriasis. The total RNA and protein of CD34+ cells were extracted, and the mRNA as well as protein expression of Notch1, Notch2 and Hes-1 were investigated using real-time PCR and Western blot assays. We found that the mRNA and protein expression levels of Notch1 and Hes-1 in psoriasis patients were higher compared to normal controls, while the Notch2 mRNA and protein expression levels in psoriasis patients were similar to those of normal controls. The elevated Notch1 and Hes-1 expression levels in psoriatic CD34+ cells might be one reason for the immune disorders which are mainly mediated by T cells.

Decreased colony formation of high proliferative potential colony-forming cells and granulocyte-macrophage colony-forming units and increased Hes-1 expression in bone marrow mononuclear cells from patients with psoriasis

BACKGROUND

Psoriasis is a chronic inflammatory disease of the skin. The dysfunctional immunity experienced by patients with psoriasis is believed to influence the bone marrow haematopoietic cells and their surrounding microenvironment. Phagocytes derived from the bone marrow of patients with active psoriasis exhibit enhanced monocytopoietic activity and hyperplasia in vitro. However, direct evidence supporting the hypothesis that bone marrow is involved in the pathogenesis of psoriasis has yet to be established.

OBJECTIVES

To investigate the involvement of bone marrow in the pathogenesis of psoriasis.

METHODS

Bone marrow mononuclear cells (BMMNCs) were isolated from patients with psoriasis and healthy individuals. The high proliferative potential colony-forming cells (HPP-CFCs), granulocyte-macrophage colony-forming units (CFU-GM) and erythroid colony-forming units (CFU-E) were cultured in the presence of defined cytokines, and the effects of secreted factors from psoriatic peripheral blood mononuclear cells (PBMCs) on colony formation of normal haematopoietic cells were analysed. Furthermore, the telomere activity of psoriatic and normal BMMNCs was determined using the polymerase chain reaction (PCR)-based telomeric repeat amplification protocol, while the expression of human telomerase reverse transcriptase (hTERT) and HES1 mRNA was detected by reverse transcription-PCR assay.

RESULTS

The numbers of HPP-CFCs and CFU-GM, but not CFU-E, were significantly reduced in cultured haematopoietic cells from patients with psoriasis. The culture supernatant of PBMCs from patients with psoriasis was found to inhibit the colony formation capacity of HPP-CFCs, CFU-GM and CFU-E of normal haematopoietic cells. We also detected low levels of telomerase activity and hTERT gene expression in psoriatic and control BMMNCs that was statistically similar between the two groups. In contrast, the HES1 gene expression appeared to be significantly elevated in psoriatic BMMNCs (P < 0.05).

CONCLUSIONS

Together, our results indicate the involvement of bone marrow in the immunopathogenesis of psoriasis, and suggest a mechanism mediated by certain inflammatory or haematopoietic cytokines present in the bone marrow microenvironment. Elevated expression levels of HES1 mRNA suggest a potential role for the Notch signalling pathway in this process.

More than skin deep: atherosclerosis as a systemic manifestation of psoriasis

There is now growing evidence that psoriasis, like other inflammatory diseases such as rheumatoid arthritis and systemic lupus erythematosus, is a systemic disorder that is associated with enhanced atherosclerosis and risk of coronary artery disease. Here we summarize the available epidemiological evidence for this association and analyse pathogenic features that are common to psoriasis and atherosclerosis. Further prospective studies are urgently needed to extend knowledge of the risk of cardiovascular morbidity and mortality in patients with psoriasis and to confirm the degree to which treatment of psoriasis reduces this risk. Nevertheless, existing data are sufficient to indicate that severe psoriasis should be more widely recognized as a potential risk factor for cardiovascular disease and should be considered with the established factors when formulating strategies for the management of cardiovascular risk.

Regulatory T cells in bronchial asthma

The main focus of this review was the role of a specific subset of T cells with immunomodulatory or immunosuppressive activities, termed regulatory T cells (Tregs), in the pathogenesis and treatment of bronchial asthma. Evidence that these cells are important in maintaining immune homeostasis in health and exhibit impaired activity in active disease will be discussed. Their therapeutic potential is perhaps best highlighted by evidence that therapies with demonstrated efficacy in allergic and asthmatic disease are associated with the induction or restoration of regulatory T-cell function, e.g. glucocorticoids, allergen immunotherapy. Strategies to improve the safety and efficacy of these treatments and that induce or boost Tregs in bronchial asthma are discussed.