Cutaneous lymphocyte antigen-positive T lymphocytes preferentially migrate to the skin but not to the joint in psoriatic arthritis

Etiopathogenesis of Psoriasis from Genetic Perspective: An updated Review

Psoriasis is an organ-specific autoimmune disease characterized by the aberrant proliferation and differentiation of keratinocytes, leading to skin lesions. Abnormal immune responses mediated by T cells and dendritic cells and increased production of inflammatory cytokines have been suggested as underlying mechanisms in the pathogenesis of psoriasis. Emerging evidence suggests that there is a heritable basis for psoriatic disorders. Moreover, numerous gene variations have been associated with the disease risk, particularly those in innate and adaptive immune responses and antigen presentation pathways. Herein, this article discusses the genetic implications of psoriatic diseases' etiopathogenesis to develop novel investigative and management options.

Current Insights Into the Role of Neuropeptide Y in Skin Physiology and Pathology

Neuropeptide Y is widely distributed within the body and has long been implicated as a contributor to skin disease based on the correlative clinical data. However, until recently, there have been few empirical investigations to determine whether NPY has a pathophysiological role in the skin. Due to appearance-altering phenotypes of atopic dermatitis, psoriasis, and vitiligo, those suffering from these diseases often face multiple forms of negative social attention. This often results in psychological stress, which has been shown to exacerbate inflammatory skin diseases - creating a vicious cycle that perpetuates disease. This has been shown to drive severe depression, which has resulted in suicidal ideation being a comorbidity of these diseases. Herein, we review what is currently known about the associations of NPY with skin diseases and stress. We also review and provide educated guessing what the effects NPY can have in the skin. Inflammatory skin diseases can affect physical appearance to have significant, negative impacts on quality of life. No cure exists for these conditions, highlighting the need for identification of novel proteins/neuropetides, like NPY, that can be targeted therapeutically. This review sets the stage for future investigations into the role of NPY in skin biology and pathology to stimulate research on therapeutic targeting NPY signaling in order to combat inflammatory skin diseases.

Human CLA+ Memory T Cell and Cytokines in Psoriasis

Psoriasis is a common inflammatory skin condition resulting from the interplay between epidermal keratinocytes and immunological cellular components. This sustained inflammation is essentially driven by pro-inflammatory cytokines with the IL-23/IL-17 axis playing a critical central role, as proved by the clinical efficacy of their blockade in patients. Among all the CD45R0⁺ memory T cell subsets, those with special tropism for cutaneous tissues are identified by the expression of the Cutaneous Lymphocyte-associated Antigen (CLA) carbohydrate on their surface, that is induced during T cell maturation particularly in the skin-draining lymph nodes. Because of their ability to recirculate between the skin and blood, circulating CLA⁺ memory T cells reflect the immune abnormalities found in different human cutaneous conditions, such as psoriasis. Based on this premise, studying the effect of different environmental microbial triggers and psoriatic lesional cytokines on CLA⁺ memory T cells, in the presence of autologous epidermal cells from patients, revealed important IL-17 cytokines responses that are likely to enhance the pro-inflammatory loop underlying the development of psoriatic lesions. The goal of this mini-review is to present latest data regarding cytokines implicated in plaque and guttate psoriasis immunopathogenesis from the prism of CLA⁺ memory T cells, that are specifically related to the cutaneous immune system.

Tissue-Resident Memory CD8+ T Cells From Skin Differentiate Psoriatic Arthritis From Psoriasis

OBJECTIVE

To compare immune cell phenotype and function in psoriatic arthritis (PsA) versus psoriasis in order to better understand the pathogenesis of PsA.

METHODS

In-depth immunophenotyping of different T cell and dendritic cell subsets was performed in patients with PsA, psoriasis, or axial spondyloarthritis and healthy controls. Subsequently, we analyzed cells from peripheral blood, synovial fluid (SF), and skin biopsy specimens using flow cytometry, along with high-throughput transcriptome analyses and functional assays on the specific cell populations that appeared to differentiate PsA from psoriasis.

RESULTS

Compared to healthy controls, the peripheral blood of patients with PsA was characterized by an increase in regulatory CD4+ T cells and interleukin-17A (IL-17A) and IL-22 coproducing CD8+ T cells. One population specifically differentiated PsA from psoriasis: i.e., CD8+CCR10+ T cells were enriched in PsA. CD8+CCR10+ T cells expressed high levels of DNAX accessory molecule 1 and were effector memory cells that coexpressed skin-homing receptors CCR4 and cutaneous lymphocyte antigen. CD8+CCR10+ T cells were detected under inflammatory and homeostatic conditions in skin, but were not enriched in SF. Gene profiling further revealed that CD8+CCR10+ T cells expressed GATA3, FOXP3, and core transcriptional signature of tissue-resident memory T cells, including CD103. Specific genes, including RORC, IFNAR1, and ERAP1, were up-regulated in PsA compared to psoriasis. CD8+CCR10+ T cells were endowed with a Tc2/22-like cytokine profile, lacked cytotoxic potential, and displayed overall regulatory function.

CONCLUSION

Tissue-resident memory CD8+ T cells derived from the skin are enhanced in the circulation of patients with PsA compared to patients with psoriasis alone. This may indicate that aberrances in cutaneous tissue homeostasis contribute to arthritis development.

Recapitulating T cell infiltration in 3D psoriatic skin models for patient-specific drug testing

Drug screening studies for inflammatory skin diseases are currently performed using model systems that only partially recapitulate human diseased skin. Here, we developed a new strategy to incorporate T cells into human 3D skin constructs (HSCs), which enabled us to closely monitor and quantitate T cell responses. We found that the epidermis promotes the activation and infiltration of T cells into the skin, and provides a directional cue for their selective migration towards the epidermis. We established a psoriatic HSC (pHSC) by incorporating polarized Th1/Th17 cells or CCR6+CLA+ T cells derived from psoriasis patients into the constructs. These pHSCs showed a psoriatic epidermal phenotype and characteristic cytokine profiles, and responded to various classes of psoriasis drugs, highlighting the potential utility of our model as a drug screening platform. Taken together, we developed an advanced immunocompetent 3D skin model to investigate epidermal-T cell interactions and to understand the pathophysiology of inflammatory skin diseases in a human-relevant and patient-specific context.

Origin, function and role in the development of skin diseases CLA+T-lymphocytes

The idea of CLA+T-lymphocytes, which are a special subpopulation of cells with a tropic to the skin, is given. The issues of maturation, migration and functional features of CLA+T-cells are considered. Special attention is paid to the different phenotype of memory T-cells. Modern data concerning the role of CLA+T-cells in the pathogenesis of autoimmune and allergic dermatoses, as well as malignant skin tumors are also presented. The conclusion about the necessity of further study of CLA +T-lymphocytes for detailed understanding of pathogenesis and search of variants of targeted therapy in psoriasis, atopic dermatitis, skin lymphomas and other skin diseases is made.

Physician’s Global Assessment in Psoriatic Arthritis: A Multicenter GRAPPA Study

Objective.

Physician’s global assessment (PGA) of disease activity is a major determinant of therapeutic decision making. This study assesses the reliability of the PGA, measured by means of 0–100 mm visual analog scale (VAS), and the additional use of separate VAS scales for musculoskeletal (PhysMSK) and dermatologic (PhysSk) manifestations in patients with psoriatic arthritis (PsA).

Methods.

Sixteen centers from 8 countries enrolled 319 consecutive patients with PsA. PGA, PhysMSK, and PhysSk evaluation forms were administered at enrollment (W0) and after 1 week (W1). Detailed clinical data regarding musculoskeletal (MSK) manifestations, as well as dermatological assessment, were recorded.

Results.

Comparison of W0 and W1 scores showed no significant variation (intraclass correlation coefficients were PGA 0.87, PhysMSK 0.86, PhysSk 0.78), demonstrating the reliability of the instrument. PGA scores were dependent on PhysMSK and PhysSk (p < 0.0001) with a major effect of the MSK component (B = 0.69) compared to skin (B = 0.32). PhysMSK was correlated with the number of swollen joints, tender joints, and presence of dactylitis (p < 0.0001). PhysSk scores were correlated with the extent of skin psoriasis and by face, buttocks or intergluteal, and feet involvement (p < 0.0001). Finally, physician and patient assessments were compared showing frequent mismatch and a scattered dot plot: PGA versus patient’s global assessment (r = 0.36), PhysMSK versus patient MSK (r = 0.39), and PhysSk versus patient skin (r = 0.49).

Conclusion.

PGA assessed by means of VAS is a reliable tool to assess MSK and dermatological disease activity. PGA may diverge from patient self-evaluation. Because MSK and skin/nail disease activity may diverge, it is suggested that both PhysMSK and PhysSk are assessed.

Role of the IL-23/IL-17 Axis in Psoriasis and Psoriatic Arthritis: The Clinical Importance of Its Divergence in Skin and Joints

Psoriasis is a chronic systemic inflammatory disease causing erythematosus and scaly skin plaques; up to 30% of patients with psoriasis develop Psoriatic Arthritis (PsA), which is characterised by inflammation and progressive damage of the peripheral joints and/or the spine and/or the entheses. The pathogenic mechanisms driving the skin disorder in psoriasis and the joint disease in PsA are sustained by the activation of inflammatory pathways that can be overlapping, but also, at least partially, distinct. Cytokines members of the IL-23/IL-17 family, critical in the development of autoimmunity, are abundantly expressed within the cutaneous lesions but also seem to be involved in chronic inflammation and damage of the synovium though, as it will be here discussed, not in all patients. In this review, we will focus on the state of the art of the molecular features of psoriatic skin and joints, focusing on the specific role of the IL-23/IL-17 pathway in each of these anatomical districts. We will then offer an overview of the approved and in-development biologics targeting this axis, emphasising how the availability of the “target” in the diseased tissues could provide a plausible explanation for the heterogeneous clinical efficacy of these drugs, thus opening future perspective of personalised therapies.

Management of psoriasis with nutraceuticals: An update

Psoriasis is a chronic skin disorder that speeds up the life cycle of skin cells, typically on the surface of the skin. Additional skin cells form thick scales and red fixes which are awfully itchy and sometimes painful. Although there are many therapeutic systems available to get symptomatic relief, unfortunately replete cure for psoriasis is not yet reported. Moreover, poor treatment outcomes as well as high toxicity profile of drugs makes these therapies more inconvenient to treat psoriasis. In search of alternative and complementary therapy for this disease, the focus has been shifted to nutraceuticals, few of them were reported since ages. It includes vitamins, herbal extracts, phytochemicals and dietary supplements. In this review, the attempt has been made to highlight key nutraceuticals for better management of psoriasis. Supplementation of appropriate nutraceutical may improve the quality of patient's life and have positive impact on overall state of disease.

Current perspective on the role of the interleukin-23/interleukin-17 axis in inflammation and disease (chronic arthritis and psoriasis)

TH17 is a lymphocyte subset, which is characterized by its polarization to secrete interleukin (IL)-17. IL-23 is the pivotal mediator responsible for TH17 differentiation and the IL-23/IL-17 axis has been strongly implicated in the pathogenesis of several immune mediated diseases, in particular chronic arthritis and skin psoriasis. This review will summarize the basic immunology and the new monoclonal antibodies, which antagonize this pathway allowing a new therapeutic approach.

Genetic, Epigenetic and Pharmacogenetic Aspects of Psoriasis and Psoriatic Arthritis

There is a strong familial component to psoriatic disease as well as a complex array of genetic, immunologic, and environmental factors. The dominant genetic effect is located on chromosome 6p21.3 within the major histocompatibility complex region, accounting for one-third of genetic contribution. Genome-wide association studies (GWAS) identified additional genes, including skin barrier function, innate immune response, and adaptive immune response genes. To better understand disease susceptibility and progression requires replication in larger cohorts, fine-mapping efforts, new technologies, and functional studies of genetic variants, gene-gene interactions and gene-environmental interactions. New technologies available include next-generation sequencing, copy number variation analysis, and epigenetics.

Psoriasis

Psoriasis is a common chronic inflammatory skin disease with a spectrum of clinical phenotypes and results from the interplay of genetic, environmental, and immunological factors. Four decades of clinical and basic research on psoriasis have elucidated many of the pathogenic mechanisms underlying disease and paved the way to effective targeted therapies. Here, we review this progress and identify future directions of study that are supported by a more integrative research approach and aim at further improving the patients' life.

Clinical potential of apremilast in the treatment of psoriatic arthritis

Psoriatic arthritis (PsA) is a frequent chronic inflammatory disease characterized by joint and skin involvement, and by typical extra-articular manifestations. Although the pathogenesis of PsA is still under investigation, the available evidence suggests the importance of the patient’s genetic background, microbial or environmental triggers, and an imbalance in the adaptive and acquired immune system, resulting in the production of inflammatory mediators. New therapeutic approaches have been proposed, among them the use of modulators of intracellular signals and gene transcription such as PDE4-inhibiting compounds, which are able to modulate the activity of transcription factors such as CREB and NF-κB and therefore the synthesis of inflammatory mediators, resulting in immunoregulation. This paper summarizes the mechanism of action of apremilast, a PDE4 inhibitor, and the clinical data available on its clinical efficacy and safety profile in the treatment of PsA patients.

Investigation of the cutaneous response to recall antigen in humans in vivo

In this paper we provide a detailed description of an experimental method for investigating the induction and resolution of recall immune response to antigen in humans in vivo. This involves the injection of tuberculin purified protein derivative (PPD) into the skin, followed by inducing suction blisters at the site of injection, from which leucocytes and cytokines that are involved in the response can be isolated and characterized. Using this technique we found that although the majority of CD4(+) T cells in the skin that are present early in the response express cutaneous lymphocyte antigen (CLA), the expression of this marker is reduced significantly in later phases. This may enable these cells to leave the skin during immune resolution. Furthermore, interleukin (IL)-2 production can be detected both in CD4(+) T cells and also in the blister fluid at the peak of the response at day 7, indicating that mediators found in the blister fluid are representative of the cytokine microenvironment in vivo. Finally, we found that older humans have defective ability to respond to cutaneous PPD challenge, but this does not reflect a global immune deficit as they have similar numbers of circulating functional PPD-specific CD4(+) T cells as young subjects. The use of the blister technology enables further characterization of the skin specific defect in older humans and also general mechanisms that govern immune regulation in vivo.

The immune system--a hidden treasure for biomarker discovery in cutaneous melanoma

This chapter describes how skin immune system (SIS) is specifically involved in the development of cutaneous melanoma. Local immune surveillance is presented as a complex process that comprises markers to be monitored in disease's evolution and in therapy. The ranking of tissue or soluble immune markers in a future panel of diagnostic/prognostic panel are evaluated. Taking into account the difficulties of cutaneous melanoma patients' management, this chapter shows the immune surveillance at the skin level, the conditions that favor the tumor escape from the immunological arm, the immune pattern of skin melanoma with diagnostic/prognostic relevance, the circulatory immune markers, and, last but not least, how immune markers are used in immune-therapy monitoring. The chapter cannot be exhaustive but will give the reader a glimpse of the complex immune network that lies within tumor escape and where to search for immune-therapeutical targets in skin melanoma.

Synovitis in psoriatic arthritis: immunohistochemistry, comparisons with rheumatoid arthritis, and effects of therapy

Psoriatic arthritis (PsA) is a chronic inflammatory arthropathy associated with psoriasis that affects the peripheral joints, spine, and entheses. Most patients with PsA present with peripheral synovitis of the oligoarticular or polyarticular subtype. As one of the targets of this disease, studies on the synovium may provide insight into the mechanisms involved in this condition. Key findings from the available studies comparing synovial tissue of PsA and rheumatoid arthritis patients are discussed in this review. Also, changes in the synovial infiltrate, expression of proinflammatory cytokines and adhesion molecules, and vascularity in synovial tissue after treatment with various medications are addressed. Finally, a model for proof-of-principle study design using serial synovial biopsies is described, which could be used to predict clinical (in)efficacy in early clinical trial design in PsA.

Patient global assessment in psoriatic arthritis: a multicenter GRAPPA and OMERACT study

OBJECTIVE

During OMERACT 8, delegates selected patient global assessment (PGA) of disease as a domain to be evaluated in randomized controlled trials in psoriatic arthritis (PsA). This study assessed the reliability of the PGA, measured by means of 0-100 mm visual analog scale (VAS), and the additional utility of separate VAS scales for joints (PJA) and skin (PSA).

METHODS

In total, 319 consecutive patients with PsA (186 men, 133 women, mean age 51 ± 13 yrs) were enrolled. PGA, PJA, and PSA were administered at enrolment (W0) and after 1 week (W1). Detailed clinical data, including ACR joint count, Psoriasis Area and Severity Index (PASI), and Hospital Anxiety and Depression Scale, were recorded.

RESULTS

Comparison of W0 and W1 scores showed no significant variations (intraclass correlation coefficients for PGA 0.87, PJA 0.86, PSA 0.78), demonstrating the reliability of the instrument. PGA scores were not influenced by patient anxiety or depression, but were dependent on PJA and PSA (p = 0.00001). PJA was dependent on the number of swollen and tender joints (p < 0.00001). PSA scores were influenced by the extent of skin psoriasis and by hand skin involvement (p = 0.00001). Joint and skin disease were found not to correlate in terms of disease activity as evidenced by the swollen joint count compared to PASI (r = 0.11) and by the PJA compared to PSA (r = 0.38).

CONCLUSION

PGA assessed by means of VAS is a reliable tool related to joint and skin disease activity. Because joint and skin disease often diverge it is suggested that in some circumstances both PJA and PSA are also assessed.

Immunopathogenesis of psoriatic arthritis: Recent advances

Psoriatic Arthritis (PsA) is a chronic inflammatory arthritis associated with psoriasis. The pathophysiology of PsA includes genetic, environmental and immunologic factors. Recent studies revealed the dynamic role of the immune system in the pathogenesis of the disease. Adhesion molecules, proinflammatory cytokines, angiogenic factors and metalloproteinases appear to orchestrate the inflammatory response in PsA. This article summarizes the current immunologic findings and suggests future therapeutic and researching approaches in the field of PsA.

Immune response profiles in human skin

In addition to the function as a physical barrier human skin has been shown to be an important immune organ displaying various defense mechanisms, which can be divided into three major functional compartments: (i) Epithelial defense, which is characterized by antimicrobial peptides and proteins (AP) and which can be induced in inflammatory lesions but also in the absence of inflammation. (ii) Innate-inflammatory immunity, which involves recognition of microbial compounds by particular receptors like Toll-like receptors (TLR) and subsequent activation of signalling pathways resulting in expression of pro-inflammatory cytokines and interferons, as well as genes of adaptive immunity. Interferon alpha (IFNalpha) produced by plasmacytoid dendritic cells (DC) may stimulate myeloid DC to produce IL-12 resulting in classical T-cell activation or to produce IL-23 activating IL-17 producing T-cells (IL-23/IL-17 pathway). (iii) Adaptive immunity, which is based on antigen presenting cells, T-cells and B-cells and which is characterized by specificity and memory. In contrast to epithelial defense and innate-inflammatory immunity, adaptive immune functions provide slowly reacting protection. Recent improvements of our knowledge of dysregulated immune pathways associated with inflammatory skin diseases represent an important basis of novel immunomodulatory treatment modalities.

T cells in psoriatic arthritis

Psoriatic arthritis is characterized by chronic inflammation of the skin and synovial joint. T cells are abundant in the inflamed joint and skin. Disease susceptibility is associated with major histocompatibility complex, which presents antigens to T cells. T cells in the synovial joints have an activated phenotype and demonstrate selective T-cell receptor usage suggestive of oligoclonal expansions. Taken together, these facts suggest that psoriatic arthritis is driven by antigen or autoantigen-driven T-cell activation. The therapeutic benefit of anti-T-cell agents further supports an important pathogenic role for T cells in persistent synovial inflammation and joint damage in psoriatic arthritis.

Psoriasis and psoriatic arthritis: separate or one and the same?

The presence and severity of skin and joint symptoms in patients with psoriasis and psoriatic arthritis frequently do not correspond, a discrepancy that has raised the question of whether they represent two related but different disease processes. The fact that some agents seem to work preferentially in one state over the other reinforces this idea. However, there are also several agents with combined efficacy against cutaneous and articular inflammation that appear to support the existence of a common aetiology. Here we review the clinical, epidemiological and genetic evidence for and against a common pathogenesis for the two diseases. We then discuss the cellular and molecular targets of their selected therapies and how they potentially implicate effector pathways as a common immunopathogenic mechanism. Finally, we examine a recently proposed model of psoriasis pathogenesis involving type 1 interferon-producing plasmacytoid dendritic cells and how it may provide further clues to the aetiological links between psoriasis and psoriatic arthritis.

Adhesion molecules in cutaneous immunity

Skin serves a vital role, providing protection from the broad array of pathogens present in our environment. In addition to the passive barrier functions of the skin, mammals have evolved a robust and versatile surveillance and rapid response system for recognition and elimination of invading organisms. This immune surveillance network directs the movement of immune cells, regulating homeostatic populations of immune cells in the skin, as well as recruitment to sites of inflammation. In this review, we discuss current understanding of the regulation and function of adhesion molecules in cutaneous immune surveillance and their relevance to the immunopathology of inflammatory skin disease.

Pathogenesis and clinical features of psoriasis

Psoriasis, a papulosquamous skin disease, was originally thought of as a disorder primarily of epidermal keratinocytes, but is now recognised as one of the commonest immune-mediated disorders. Tumour necrosis factor alpha, dendritic cells, and T-cells all contribute substantially to its pathogenesis. In early-onset psoriasis (beginning before age 40 years), carriage of HLA-Cw6 and environmental triggers, such as beta-haemolytic streptococcal infections, are major determinants of disease expression. Moreover, at least nine chromosomal psoriasis susceptibility loci have been identified. Several clinical phenotypes of psoriasis are recognised, with chronic plaque (psoriasis vulgaris) accounting for 90% of cases. Comorbidities of psoriasis are attracting interest, and include impairment of quality of life and associated depressive illness, cardiovascular disease, and a seronegative arthritis known as psoriatic arthritis. A more complete understanding of underlying pathomechanisms is leading to new treatments, which will be discussed in the second part of this Series.

Psoriatic arthritis as a distinct disease entity

Psoriatic arthritis (PsA) is a chronic systemic inflammatory disease characterized by joint inflammation associated with cutaneous psoriasis. For many years, the amount of attention directed to PsA had been less than that for various other arthropathies. With the advances in understanding its pathogensis, it is now recognized as a distinct disease entity with characteristic features. Psoriatic arthritis has a greater tendency towards asymmetric oligoarticular involvement, distal interphalangeal involvement and spondylitis. Associated features such as enthesitis and dactylitis are more common. Specific radiological features include ankylosis and bone resorption. With the availability of potent new therapeutic agents for psoriasis and PsA, interest in research and clinical care for these conditions has been reinvigorated. Anti-TNF therapy has achieved encouraging efficacy in both the joints and skin disease, improving function and quality of life and inhibiting radiological progression measured in patients with PsA and psoriasis. Biologic agents may have the potential in addressing the unmet medical need in patients with PsA.

Mantoux Test as a model for a secondary immune response in humans

The Mantoux Test (MT) is a classical delayed-type hypersensitivity (DTH) response to the intradermal injection of tuberculin purified protein derivative (PPD). It represents a cutaneous T cell mediated memory recall immune response. The test is typically used to determine immunity to tuberculosis in humans and positive reactions develop in individuals previously exposed to Mycobacterium tuberculosis, and those immunised with the Bacillus of Calmette and Guérin (BCG) vaccine. In view of its relative accessibility human skin represents a convenient tissue for the investigation of human immune responses. Using the MT, we have been able to determine that significant cellular proliferation and clonal expansion occur at the site of antigen deposition in the skin. Furthermore, cells undergoing proliferation in the skin also undergo accelerated differentiation. Taken together with other studies, in humans and in mice, these observations shed new light on the importance of the microenvironment at the site of the immune response for the proliferation and differentiation of memory T cells.

Identical TCR beta-chain rearrangements in streptococcal angina and skin lesions of patients with psoriasis vulgaris

Tonsillar infection with Streptococcus pyogenes may induce several nonsuppurative autoimmune sequelae. The precise pathogenetic mechanisms behind this clinically well-established association are still unresolved. Using TCR analysis, we sought to identify a link between streptococcal tonsillitis and the T cell-mediated autoimmune response in psoriasis. Three patients with streptococcal-induced psoriasis underwent tonsillectomy. Using size spectratyping and sequencing of TCR beta-chain variable region gene (TCRBV) rearrangements, we compared the TCR usage of psoriatic skin lesions, blood, tonsils, and tonsillar T cells fractionated according to the expression of the skin address in "cutaneous lymphocyte-associated Ag" (CLA). TCRBV-size spectratype analysis of the blood lymphocytes, tonsils, and the CLA-negative tonsillar T cells revealed largely unselected T cell populations. Instead, TCRBV gene families of the psoriatic lesions and skin-homing CLA-positive tonsillar T cells displayed highly restricted spectratypes. Sequencing of TCRBV cDNA identified various clonal TCRBV rearrangements within the psoriatic lesions that indicated Ag-driven T cell expansion. Several of these clonotypes were also detected within the tonsils and, in one of the patients, within the small subset of CLA-positive tonsillar T cells, suggesting that T cells from the same T cell clones were simultaneously present within skin and tonsillar tissue. Because after tonsillectomy psoriasis cleared in all three patients our observations indicate that T cells may connect psoriatic inflammation to streptococcal angina. They suggest that the chronic streptococcal immune stimulus within the tonsils could act as a source for pathogenic T cells in poststreptococcal disorders, and they may help to explain why eliminating this source with tonsillectomy may improve streptococcal-induced sequelae.

Psoriatic arthritis: One or more diseases?

Psoriatic arthritis (PsA) is a common, debilitating auto-immune disease with diverse clinical features. In this paper, published evidence is examined, which addresses the issues that (a) PsA exists; and (b) PsA can or cannot be viewed as a distinct rheumatic disease from other spondyloarthritides. Evidence derived from epidemiological, clinical, genetic and immunohistological studies is included. Summarizing the evidence, it is clear that PsA does indeed exist, with the prevalence of rheumatic disease in patients with psoriasis (Ps) higher than would be expected. Certain clinical features also occur more commonly in PsA, although none can differentiate consistently from other arthropathies. Both genetic and immunohistological studies suggest that PsA, both oligo- and polyarticular disease, can be clearly separated from rheumatoid arthritis and that it belongs to the family of spondyloarthritides. The presence of Ps may confer a more severe clinical phenotype with poor radiological outcome. It may be that, with time, a specific genetic marker or diagnostic feature will emerge; additional, more detailed pathogenic studies are required. In the meanwhile, particularly with new treatments being evaluated, it is important to continue to develop specific classification or diagnostic criteria and to define both clinical and laboratory-based outcome measures.

CD43 is a ligand for E-selectin on CLA+ human T cells

The recruitment of memory T cells from blood into tissues is a central element of immune surveillance and adaptive immune responses and a key feature of chronic cutaneous inflammatory diseases such as psoriasis and atopic dermatitis. Human memory T cells that infiltrate skin express the carbohydrate epitope cutaneous lymphocyte-associated antigen (CLA). Expression of the CLA epitope on T cells has been described on P-selectin glycoprotein ligand-1 (PSGL-1) and associated with the acquisition of both E-selectin and P-selectin ligand functions. In this report, we show that CD43, a sialomucin expressed constitutively on T cells, can also be decorated with the CLA epitope and serve as an E-selectin ligand. CLA expressed on CD43 was found exclusively on the high-molecular-weight (125 kDa) glycoform bearing core-2-branched O-linked glycans. CLA+ CD43 purified from human T cells supported tethering and rolling in shear flow via E-selectin but did not support binding of P-selectin. The identification and characterization of CD43 as a T-cell E-selectin ligand distinct from PSGL-1 expands the role of CD43 in the regulation of T-cell trafficking and provides new targets for the modulation of immune functions in skin.

Psoriatic arthritis: pathogenesis and novel immunomodulatory approaches to treatment

Psoriatic arthritis (PsA) is a chronic inflammatory arthropathy characterized by the association of arthritis and psoriasis. PsA runs a variable course, from mild synovitis to severe, progressive, erosive arthropathy. The pathogenesis of PsA involves alteration in the components of the immune response, although the exact cause of PsA is unknown. A number of patients with severe peripheral arthritis fail to respond to standard conventional therapy. Advances in biotechnology and in our understanding of the immunopathogenesis of PsA have led to great interest and progress in regards to biologic treatments for PsA. Notable success achieved with recently introduced biologic therapies has paved the way for further research and development of additional therapies that should improve outcomes for affected patients.

Expression of cutaneous lymphocyte-associated antigen (CLA) in tonsillar T-cells and its induction by in vitro stimulation with alpha-streptococci in patients with pustulosis palmaris et plantaris (PPP)

Pustulosis palmaris et plantaris (PPP) is known to be a one of the tonsil-related diseases because tonsillectomy is quite effective in curing this condition. However etiological association between tonsils and PPP have not fully clarified yet. Cutaneous lymphocyte-associated antigen (CLA) is known to be a specific homing receptor that facilitates T-cell migration into skin. In this study, we investigated the expression of CLA on T-cells in tonsil, peripheral blood, and skin from patients with PPP. Two-color flow cytometric and two-color immunohistological analyses revealed that the numbers of CLA/CD3 double-positive cells in freshly isolated tonsillar mononuclear cells (TMC) and in tonsillar tissues were significantly higher in patients with PPP than in patients without PPP (P<0.01, each). In vitro stimulus with alpha-streptococcal antigens enhanced CLA expression of tonsillar T-cells and TGF-beta production of TMC in patients with PPP (P<0.01, each), but did not in patients without PPP. In peripheral blood from PPP patients, the number of the CLA/CD3 double-positive cells significantly decreased at 6 months after tonsillectomy (P<0.05). The CLA/CD3 double-positive cells and the postcapillary venule that expressed with a ligand of CLA, E-selectin, were found more frequently in the plantar skin from patients with PPP as compared to that from healthy volunteers (P<0.01, each). These data suggest that a novel immune response to alpha-streptococci may enhance CLA expression on tonsillar T-cells through TGF-beta production in patients with PPP, resulting in moving of CLA-positive tonsillar T-cells to skin and tissue damages. This may play a key role in pathogenesis of PPP.

Clinical analysis of 21 patients with psoriasis arthropathy

Psoriasis arthropathy (PsA) is a chronic inflammatory arthropathy characterized by the association of arthritis with psoriasis. In this study, clinical, laboratory and radiographic signs of 21 patients (12 males and 9 females), mean age of 42.2 years old, with PsA were assessed. The clinical forms defined by Moll and Wright revealed that oligoarticular pattern was most commonly observed in ten patients (47.6%), followed by polyarticular (5 patients), distal (3 patients), spondyloarthropathy (2 patients), and mutilans (1 patient). Positive rheumatoid factor was detected in three patients and antinuclear antibodies in eight patients, suggesting the involvement of immunological disregulation in this disorder. Twelve patients were onychopathic, of whom 11 showed distal interphalangeal (DIP) joint arthritis. Based on radiologic observation, spur formation of the calcaneus (1 patient) and destructive changes of the articulatio coxa (1 patient) were seen, in addition to the findings such as joint space narrowing, erosive changes, resorptive changes and 'pencil-in-cup' appearances. Non-steroidal anti-inflammatory drugs (NSAIDs) were used in all cases for the control of joint pain, solely or in combination with immunomodulatory drugs such as bucillamine, sulfasalazine, methotrexate, cyclosporin, etretinate, and mizoribine. However, some of those drugs were often ineffective for the joint pain, while effective for cutaneous psoriasis. Immunohistological studies of the biopsied synovial tissues from two patients showed increased expressions of CD45RO and HLA-DR, suggesting that the vast majority of inflammatory cells are mature and activated T-cells. Parallel immunostaining using the involved psoriatic skin from one of the patients also showed enhanced expression of CD45RO, but less expression of HLA-DR as compared with its expression in the synovium. On the other hand, cutaneous leukocyte antigen (CLA) was abundantly detected in the inflammatory cells in the lesional skin, although less expressed in the synovium. These results are consistent with earlier observations suggesting a different subpopulation of inflammatory cells in the skin than the joint.

Immunopathology of psoriasis and psoriatic arthritis

Psoriatic arthritis (PsA) is characterised by several unique clinical features that differentiate it from rheumatoid arthritis (RA). Attempts to identify immunopathological mechanisms, some shared with psoriasis, that underlie these differences from RA have been most challenging. Recent research studies, however, highlight novel findings in PsA at the molecular, cellular, and tissue levels that form the basis for a new understanding of this relatively common form of inflammatory arthritis. In particular, the availability of new, biological antitumour necrosis factor alpha therapies have allowed further insight into the immunopathology of psoriasis and PsA. This brief review focuses on immunohistological studies in psoriatic skin, PsA synovium, and bone to demonstrate how these data advance our knowledge of disease pathogenesis.

Deactivation of endothelium and reduction in angiogenesis in psoriatic skin and synovium by low dose infliximab therapy in combination with stable methotrexate therapy: a prospective single-centre study

Psoriasis and psoriatic arthritis are inflammatory diseases that respond well to anti-tumour necrosis factor-α therapy. To evaluate the effects of anti-tumour necrosis factor-α treatment on expression of adhesion molecules and angiogenesis in psoriatic lesional skin and synovial tissue, we performed a prospective single-centre study with infliximab therapy combined with stable methotrexate therapy. Eleven patients with both active psoriasis and psoriatic arthritis received infusions of infliximab (3 mg/kg) at baseline, and at weeks 2, 6, 14 and 22 in an open-label study. In addition, patients continued to receive stable methotrexate therapy in dosages ranging from 5 to 20 mg/week. Clinical assessments, including Psoriasis Area and Severity Index (PASI) and Disease Activity Score (DAS), were performed at baseline and every 2 weeks afterward. In addition, skin biopsies from a target psoriatic plaque and synovial tissue biopsies from a target joint were taken before treatment and at week 4. Immunohistochemical analysis was performed to detect the number of blood vessels, the expression of adhesion molecules and the presence of vascular growth factors. Stained sections were evaluated by digital image analysis. At week 16, the mean PASI was reduced from 12.3 ± 2.4 at baseline to 1.8 ± 0.4 (P ≤ 0.02). The mean DAS was reduced from 6.0 ± 0.5 to 3.6 ± 0.6 (P ≤ 0.02). We found some fluctuations in DAS response as compared with the change in PASI, with the latter exhibiting a steady decrease over time. After 4 weeks the cell infiltrate was reduced in both skin and synovium. There was a significant reduction in the number of blood vessels in dermis and synovium at week 4. A significant reduction in the expression of α_vβ₃ integrin, a marker of neovascularization, was also found in both skin and synovium at week 4. In addition, a significant reduction in the expression of adhesion molecules was observed in both skin and synovium at week 4. We also observed a trend toward reduced expression of vascular endothelial growth factor in both skin and synovium. In conclusion, low-dose infliximab treatment leads to decreased neoangiogenesis and deactivation of the endothelium, resulting in decreased cell infiltration and clinical improvement in psoriasis and psoriatic arthritis.

Recent advances in the treatment of psoriatic arthritis

This article provides an overview of recent developments in the treatment of psoriatic arthritis with an emphasis on patent literature for the period January 1998 to December 2002. The main pathogenic pathways thought to be operative in psoriatic arthritis are highlighted and some novel compounds that can potentially interfere with such pathways at different levels are discussed. Among the new agents proposed, the inhibitors of cytokine signaling, angiogenesis, and extracellular matrix degradation appear to be of particular interest for the treatment of psoriatic arthritis resistant to conventional therapies. Finally, new formulations of existing drugs and natural remedies claimed to be useful for the treatment of psoriatic arthritis are reviewed.

Interleukin-12 alone can not enhance the expression of the cutaneous lymphocyte associated antigen (CLA) by superantigen-stimulated T lymphocytes

It has been reported that bacterial superantigens induce interleukin (IL)-12 dependent expression of the cutaneous lymphocyte associated antigen (CLA) and that this may be relevant to the association between certain skin diseases and infections including psoriasis and streptococcal tonsillitis. We have confirmed that the streptococcal pyrogenic superantigen C (SpeC) increases CLA expression by both CD4+ and CD8+ T cells when PBMCs are incubated in medium enriched with fetal calf serum (FCS). However, such an increase could not be induced in medium enriched with human serum (HS) even when recombinant IL-12 was added to the PBMCs cultures. Strikingly, CD4+ T cells incubated with SpeC in HS showed a marked reduction in CLA expression, which was not due to apoptosis. In contrast, SpeC did induce T cell proliferation and expression of CD25, CD54 and CD103 in the presence of HS indicating that the absence of SpeC induced CLA expression in HS was not due to SpeC inhibitors. Although addition of low amounts of lipopolysaccharide endotoxin (LPS) caused a highly significant increase in CLA expression in the absence of SpeC in cultures enriched with HS, a combination of LPS and SpeC did not increase CLA expression beyond that induced by LPS alone. The superantigen-induced CLA expression in FCS was partially inhibited by anti-IL-12 but not by anti-IL-18 or antibodies to transforming growth factor (TGF)-beta. It is concluded that IL-12 alone can not increase CLA expression but requires the help of other factor(s) present in FCS but not in HS. Although LPS can induce CLA expression it does not seem to be the factor that interacts with IL-12 to induce superantigen-mediated CLA expression in cultures enriched with FCS.

The effects of ultraviolet B treatment on the expression of adhesion molecules by circulating T lymphocytes in psoriasis

BACKGROUND

T lymphocytes are believed to play a role in the pathogenesis of psoriasis; > 80% of T lymphocytes that infiltrate psoriatic lesions express the surface glycoprotein cutaneous lymphocyte-associated antigen (CLA), compared with < 20% in the blood. Exposure to ultraviolet (UV) B is an effective treatment for psoriasis.

OBJECTIVES

To compare the effects of UVB treatment of psoriasis on the expression of CLA and several other surface markers expressed by circulating T lymphocytes.

METHODS

Peripheral blood mononuclear cells from psoriatic patients were stained for adhesion molecules and stimulated with streptococcal antigens before and once weekly during 3 weeks of UVB treatment.

RESULTS

A marked and progressive decrease was observed during the treatment in expression of the CLA and the very late antigen-4alpha by T cells; this decrease correlated closely with clinical improvement (Psoriasis Area and Severity Index). T-cell expression of intercellular adhesion molecule-1 was not significantly affected during the treatment and no change was observed in the activation markers CD25 and CD69 or lymphocyte proliferation after stimulation with streptococcal antigens or superantigens.

CONCLUSIONS

UVB treatment is associated with a marked reduction in the expression of skin-homing molecules by circulating T cells. This may be relevant to the therapeutic effect of UVB in psoriasis.

Analyzing the migration of labeled T cells in vivo: an essential approach with challenging features

T cells are involved in the pathogenesis of many diseases. To exert a pathological effect, T cells enter the tissues. We show that the determination of their entry site requires isolation of the respective T cell population, injection into genetically un-manipulated animals, and identification of the cells in vivo at various time points after injection. We indicate variables influencing in vivo migration experiments artificially, and outline how resulting problems can be either avoided or taken into account. Reviewing experiments performed according to the outlined criteria reveals two types of migration patterns for T cell subsets in vivo: 1). Naïve and memory T cells enter lymphoid and non-lymphoid organs in comparable numbers, but selectively accumulate in lymphoid tissues over time, 2). Effector T cells, too, enter lymphoid and non-lymphoid organs in comparable numbers. However, most of them die within 24 hours. Depending on the presence of cytokines, chemokines and extracellular matrix compounds they are able to survive, thereby preferentially accumulating in their target tissues. This information might help to understand the role of migration in the pathogenesis of T cell mediated diseases.