T cells involved in psoriasis vulgaris belong to the Th1 subset

Genetic control directed toward spontaneous IFN-alpha/IFN-beta responses and downstream IFN-gamma expression influences the pathogenesis of a murine psoriasis-like skin disease

Psoriasis is an inflammatory skin disease, onset and severity of which are controlled by multiple genetic factors; aberrant expression of and responses to several cytokines including IFN-alpha/IFN-beta and IFN-gamma are associated with this "type 1" disease. However, it remains unclear whether genetic regulation influences these cytokine-related abnormalities. Mice deficient for IFN regulatory factor-2 (IRF-2) on the C57BL/6 background (IRF-2(-/-)BN mice) exhibited accelerated IFN-alpha/IFN-beta responses leading to a psoriasis-like skin inflammation. In this study, we found that this skin phenotype disappeared in IRF-2(-/-) mice with the BALB/c or BALB/c x C57BL/6 F(1) backgrounds. Genome-wide scan revealed two major quantitative trait loci controlled the skin disease severity. Interestingly, these loci were different from that for the defect in CD4(+) dendritic cells, another IFN-alpha/IFN-beta-dependent phenotype of the mice. Notably, IFN-gamma expression as well as spontaneous IFN-alpha/IFN-beta responses were up-regulated several fold spontaneously in the skin in IRF-2(-/-)BN mice but not in IRF-2(-/-) mice with "resistant" backgrounds. The absence of such IFN-gamma up-regulation in IRF-2(-/-)BN mice lacking the IFN-alpha/IFN-beta receptor or beta(2)-microglobulin indicated that accelerated IFN-alpha/IFN-beta signals augmented IFN-gamma expression by CD8(+) T cells in the skin. IFN-gamma indeed played pathogenic roles as skin inflammation was delayed and was much more infrequent when IRF-2(-/-)BN mice lacked the IFN-gamma receptor. Our current study thus revealed a novel genetic mechanism that kept the skin immune system under control and prevented skin inflammation through regulating the magnitude of IFN-alpha/IFN-beta responses and downstream IFN-gamma production, independently of CD4(+) dendritic cells.

Immunopathogenesis of psoriasis

Psoriasis is a chronic skin disease that affects about 1.5% of the Caucasian population and is characterized by typical macroscopic and microscopic skin alterations. Psoriatic lesions are sharply demarcated, red and slightly raised lesions with silver-whitish scales. The microscopic alterations of psoriatic plaques include an infiltration of immune cells in the dermis and epidermis, a dilatation and an increase in the number of blood vessels in the upper dermis, and a massively thickened epidermis with atypical keratinocyte differentiation. It is considered a fact that the immune system plays an important role in the pathogenesis of psoriasis. Since the early 1990s, it has been assumed that T1 cells play the dominant role in the initiation and maintenance of psoriasis. However, the profound success of anti-tumor necrosis factor-alpha therapy, when compared with T-cell depletion therapies, should provoke us to critically re-evaluate the current hypothesis for psoriasis pathogenesis. Recently made discoveries regarding other T-cell populations such as Th17 and regulatory T cells, dendritic cells, macrophages, the keratinocyte signal transduction and novel cytokines including interleukin (IL)-22, IL-23 and IL-20, let us postulate that the pathogenesis of psoriasis consists of distinct subsequent stages, in each of them different cell types playing a dominant role. Our model helps to explain the varied effectiveness of the currently tested immune modulating therapies and may enable the prediction of the success of future therapies.

Heart disease in psoriasis

Psoriasis has been traditionally viewed as an inflammatory skin disorder of unknown origin. Recent advances in the immunopathogenesis and genetics of psoriasis have broadened our understanding of psoriasis. Psoriasis is now considered a systemic inflammatory condition analogous to other inflammatory immune disorders. Patients with other immune disorders, such as systemic lupus erythematosus or rheumatoid arthritis, are known to be at increased risk of heart disease. Similarly, patients with psoriasis may carry an excess risk of heart disease, which would represent an important previously unrecognized cause of morbidity and mortality. This review summarizes the current evidence for an increased cardiovascular risk in patients with psoriasis and outlines deficits in our knowledge in this area.

Adhesion of peripheral blood mononuclear cells and CD4+ T cells from patients with psoriasis to cultured endothelial cells via the interaction between lymphocyte function-associated antigen type 1 and intercellular adhesion molecule 1

BACKGROUND

The adhesion of CD4+ T cells to endothelial cells and their subsequent migration to skin tissue are essential to develop the psoriatic skin lesion. However, few studies have examined the role of adhesion molecules in the binding of T cells from patients with chronic plaque psoriasis to endothelial cells in vitro; thus, the adhesion molecules responsible for the development of skin lesions are still unclear.

OBJECTIVES

To identify the responsible adhesion molecules in the interaction between CD4+ T cells in patients with chronic plaque psoriasis and cytokine-stimulated endothelial cells.

METHODS

An in vitro adhesion assay between Calcein-labelled peripheral blood mononuclear cells (PBMC) and cytokine-stimulated human endothelial cultures, which exhibit a higher adhesion capacity to PBMC, was established, and the adhesion-inhibitory effects of a panel of antiadhesion molecule antibodies on the adhesion of PBMC from patients with psoriasis to endothelial cells were examined. Then, the inhibitory effects of selected antibodies acting on the interaction between CD4+ T cells from patients with psoriasis (purified by negative magnetic cell sorting) and cultured endothelial cells were examined.

RESULTS

A significant increase (P < 0.01) in the adhesion of psoriatic PBMC to both endothelial cultures, human skin microvascular endothelial cells from adults (HMVEC-Ad) and human coronary arterial endothelial cells (HCAEC), compared with healthy PBMC, was demonstrated in our in vitro cell adhesion assay. Pretreatment of both endothelial cultures with tumour necrosis factor (TNF)-alpha (1000 U mL(-1)) induced the most frequent adhesion of PBMC from patients with psoriasis among the three inflammatory cytokines examined, i.e. TNF-alpha, interleukin-1beta and interferon-gamma [TNF-alpha-treated vs. nontreated: P < 0.001 (in both HMVEC-Ad and HCAEC)]. In both endothelial cultures treated with TNF-alpha, PBMC from patients with psoriasis exhibited significantly more frequent adhesion compared with those from healthy individuals (P < 0.001). The TNF-alpha-stimulated HMVEC-Ad, which exhibited the most frequent adhesion of PBMC, were selected for adhesion-inhibition experiments using monoclonal antibodies (mAbs) to adhesion molecules that are upregulated in psoriatic lesions, and the combination of antilymphocyte function-associated antigen type 1 (LFA-1) and anti-intercellular adhesion molecule 1 (ICAM-1) mAbs gave the greatest reduction of adhesion of PBMC from patients with psoriasis (approximately 69% reduction; P < 0.01). This combination of mAbs significantly reduced also the adhesion of CD4+ T cells from patients with psoriasis to TNF-alpha-stimulated HMVEC-Ad (approximately 62% reduction), compared with pretreatment with isotype control mAbs (P < 0.01).

CONCLUSIONS

These findings indicate that the LFA-1/ICAM-1 interaction plays a major role in the adhesion of CD4+ T cells to endothelial cells and that TNF-alpha might play an important role for the induction of adhesion molecules on endothelial cells at psoriatic skin lesions.

The effects of IL-20 subfamily cytokines on reconstituted human epidermis suggest potential roles in cutaneous innate defense and pathogenic adaptive immunity in psoriasis

IL-19, IL-20, IL-22, IL-24, and IL-26 are members of the IL-10 family of cytokines that have been shown to be up-regulated in psoriatic skin. Contrary to IL-10, these cytokines signal using receptor complex R1 subunits that are preferentially expressed on cells of epithelial origin; thus, we henceforth refer to them as the IL-20 subfamily cytokines. In this study, we show that primary human keratinocytes (KCs) express receptors for these cytokines and that IL-19, IL-20, IL-22, and IL-24 induce acanthosis in reconstituted human epidermis (RHE) in a dose-dependent manner. These cytokines also induce expression of the psoriasis-associated protein S100A7 and keratin 16 in RHE and cause persistent activation of Stat3 with nuclear localization. IL-22 had the most pronounced effects on KC proliferation and on the differentiation of KCs in RHE, inducing a decrease in the granular cell layer (hypogranulosis). Furthermore, gene expression analysis performed on cultured RHE treated with these cytokines showed that IL-19, IL-20, IL-22, and IL-24 regulate many of these same genes to variable degrees, inducing a gene expression profile consistent with inflammatory responses, wound healing re-epithelialization, and altered differentiation. Many of these genes have also been found to be up-regulated in psoriatic skin, including several chemokines, beta-defensins, S100 family proteins, and kallikreins. These results confirm that IL-20 subfamily cytokines are important regulators of epidermal KC biology with potentially pivotal roles in the immunopathology of psoriasis.

The evaluation of psoriasis therapy with biologics leads to a revision of the current view of the pathogenesis of this disorder

Psoriasis is a common chronic, recurring skin disease that is characterised by typical macroscopic and microscopic skin alterations. It is widely accepted that the immune system plays an important role in the pathogenesis of this disorder. Since the early 1990s, the dominant role of a subpopulation of T cells, so-called T1 cells, and their prominent cytokine IFN-gamma has been assumed in the pathogenesis of psoriasis. Surprisingly, the comparison of the therapeutic success of treatments with recombinant proteins directed against defined immunological structures shows that those that directly affect T cells (alefacept, efalizumab, Hu-max-CD4, OKTcdr4a) were clearly less effective than those targeting TNF-alpha (etanercept, adalimumab, infliximab). For this reason, the authors critically re-evaluated the view of psoriasis pathogenesis and postulate that in the majority of patients the T1 cells do not play a dominant role in the clinical, visible stage of this disease.

Srcasm overexpression in psoriasis-insights into pathogenesis

BACKGROUND

Psoriasis is a prevalent, chronic cutaneous disorder associated with a T-cell lymphocytic infiltrate and altered keratinocyte growth. Some of the molecular features of enhanced keratinocyte growth include increased growth factor receptor activation leading to enhanced cellular tyrosine kinase activity. Receptor tyrosine kinases, including the epidermal growth factor (EGF) receptor, are important regulators of keratinocyte growth, and increased activity of this receptor has been detected in psoriasis. A recently discovered, novel regulator of Src tyrosine kinases, termed Src-activating and signaling molecule (Srcasm), has been shown to modulate EGF signaling and promote differentiation in human keratinocytes. Given the properties of Srcasm, it would be of interest to characterize its expression in psoriasis. In this study, the levels of Srcasm mRNA and protein are characterized, and the relationship of these experimental observations to the psoriasis pathogenesis is discussed.

METHODS

The levels of Srcasm mRNA were determined by quantitative reverse transcriptase polymerase chain reaction (RT-PCR) on RNA isolated from unremarkable and lesional patient tissue. These data were supplemented by performing radioactive in situ hybridization on formalin-fixed biopsy specimens of psoriatic lesions and unremarkable epidermis. Expression of Srcasm protein was evaluated by protein immunohistochemistry and Western blotting of protein lysates derived from patient samples.

RESULTS

All experimental modalities show that levels of Srcasm mRNA and protein were elevated in psoriatic lesions compared to unremarkable epidermis.

CONCLUSIONS

Increased levels of Srcasm mRNA and protein are seen in psoriasis. Given what is known regarding Srcasm function, increased levels of this molecule in keratinocytes may represent a cell compensatory mechanism that is primed to re-establish a physiologic differentiation program.

Inhibition of T helper 2 chemokine production by narrowband ultraviolet B in cultured keratinocytes

BACKGROUND

Narrowband ultraviolet B (NB-UVB) has recently been used for the treatment of various skin disorders. Its effects on the production of cytokines and chemokines by keratinocytes are unknown.

OBJECTIVES

To investigate the effect of NB-UVB on production of chemokines and proinflammatory cytokines by keratinocytes in comparison with broadband (BB)-UVB.

METHODS

Normal human epidermal keratinocytes (or the human keratinocyte cell line HaCaT in some experiments) at semiconfluency were irradiated with NB-UVB at 10, 100, 500 or 1000 mJ cm(-2) or BB-UVB at 10 or 100 mJ cm(-2). The cultures were maintained in the presence or absence of interferon (IFN)-gamma at 200 U mL(-1). The 72-h culture supernatants were analysed by enzyme-linked immunosorbent assay to quantify T helper (Th)1 chemokines (IFN-inducible protein 10 and monokine induced by IFN-gamma), Th2 chemokines [macrophage-derived chemokine (MDC) and thymus and activation-regulated chemokine (TARC)] and proinflammatory cytokines [interleukin (IL)-1alpha and tumour necrosis factor (TNF)-alpha]. The expression of mRNA for these molecules was simultaneously assessed by reverse transcriptase-polymerase chain reaction. The culture supernatants were also tested for their chemotactic activity for Th1 and Th2 cells. The two UVB sources were compared on the basis of their minimal erythemal doses and clinically used doses.

RESULTS

Although both NB-UVB and BB-UVB increased the production of IL-1alpha and TNF-alpha, the augmentative effect of NB-UVB was less than that of BB-UVB. Both wavelength ranges of UVB enhanced or had no effect on Th1 chemokine production, but suppressed the production of Th2 chemokines MDC and TARC. This was confirmed by chemotactic assay, which showed decreased chemotactic activity for Th2 cells by the culture supernatants from NB-UVB-irradiated keratinocytes.

CONCLUSIONS

NB-UVB reduces the production of Th2 chemokines without excess production of proinflammatory cytokines, suggesting its therapeutic effectiveness on Th2-mediated skin disorders as well as its relative safety in clinical usage.

Interleukin-22, a T(H)17 cytokine, mediates IL-23-induced dermal inflammation and acanthosis

Psoriasis is a chronic inflammatory skin disease characterized by hyperplasia of the epidermis (acanthosis), infiltration of leukocytes into both the dermis and epidermis, and dilation and growth of blood vessels. The underlying cause of the epidermal acanthosis in psoriasis is still largely unknown. Recently, interleukin (IL)-23, a cytokine involved in the development of IL-17-producing T helper cells (T(H)17 cells), was found to have a potential function in the pathogenesis of psoriasis. Here we show that IL-22 is preferentially produced by T(H)17 cells and mediates the acanthosis induced by IL-23. We found that IL-23 or IL-6 can directly induce the production of IL-22 from both murine and human naive T cells. However, the production of IL-22 and IL-17 from T(H)17 cells is differentially regulated. Transforming growth factor-beta, although crucial for IL-17 production, actually inhibits IL-22 production. Furthermore, IL-22 mediates IL-23-induced acanthosis and dermal inflammation through the activation of Stat3 (signal transduction and activators of transcription 3) in vivo. Our results suggest that T(H)17 cells, through the production of both IL-22 and IL-17, might have essential functions in host defence and in the pathogenesis of autoimmune diseases such as psoriasis. IL-22, as an effector cytokine produced by T cells, mediates the crosstalk between the immune system and epithelial cells.

Immunopathogenesis of psoriasis

This paper reviews the pathogenesis of psoriasis, in particular, the immunological cascade in psoriasis. Psoriasis is an immune-mediated skin disease where the T cell plays a pivotal role in the pathogenesis of the disease. The critical steps involved in the pathogenesis include Langerhans cell activation and maturation by antigens in the skin, activation of the T cell by mature Langerhans cells, differentiation and expansion of T cells within the lymph nodes, trafficking of activated T cells from the lymph node to the skin and the subsequent release of cytokines. These cytokines are responsible for epidermal and vascular hyperproliferation and pro-inflammatory effects. Each of these steps provides an opportunity for biological agents designed to block the psoriatic immunological cascade. This paper reviews the immunopathogenesis of psoriasis. Biologic agents in psoriasis, to be published separately, reviews the new biologic therapies that aim to selectively block the immunological steps implicated in the pathogenesis of psoriasis outlined in this paper.

Regulatory mechanisms of galectin-9 and eotaxin-3 synthesis in epidermal keratinocytes: possible involvement of galectin-9 in dermal eosinophilia of Th1-polarized skin inflammation

BACKGROUND

Skin eosinophilia is a common feature of allergic skin diseases, but it is unclear how epidermal and dermal eosinophil infiltration is controlled. To investigate regulation of localization of eosinophils in skin, we examined the regulatory mechanisms of expression of eosinophil-specific chemoattractants in dermal fibroblasts and epidermal keratinocytes.

METHODS

We analyzed production of eotaxin, eotaxin-2, eotaxin-3 and galectin-9 by dermal fibroblasts and epidermal keratinocytes in response to several stimuli in vitro.

RESULTS

Dermal fibroblasts produced eotaxin and eotaxin-3 in response to stimulation by interleukin (IL)-4 and/or tumor necrosis factor-alpha. Similarly, IL-4 stimulated epidermal keratinocytes to secrete eotaxin-3. However, we did not detect eotaxin mRNA expression or protein secretion by keratinocytes stimulated in vitro. Interferon (IFN)-gamma induced galectin-9 expression on dermal fibroblasts. Conversely, expression of galectin-9 on epidermal keratinocytes was dose-dependently inhibited by IFN-gamma. The immunohistochemical assays revealed that dermal fibroblasts (but not epidermal keratinocytes) in the lesional skin of psoriasis vulgaris (a Th1-polarized disease) express significant levels of galectin-9.

CONCLUSION

Eotaxin-3 contributes to dermal and epidermal eosinophil infiltration in Th2-polarized skin inflammation in which IL-4 is produced. In contrast, IFN-gamma-dominated inflammation appears to mediate eosinophil extravasation into the dermis and eosinophil adhesion to dermal fibroblasts via galectin-9 in association with decreased chemoattractant activity of epidermal galectin-9. The present results reveal a novel mechanism of dermal eosinophilia in IFN-gamma-mediated skin inflammation, and reflect concerted chemoattractant production involving dermal and/or epidermal eosinophilia during changes in the local cytokine profile.

In situ depletion of CD4+ T cells in human skin by Zanolimumab

CD4(+) T cells, in activated or malignant form, are involved in a number of diseases including inflammatory skin diseases such as psoriasis, and T cell lymphomas such as the majority of cutaneous T cell lymphomas (CTCL). Targeting CD4 with an antibody that inhibits and/or eliminates disease-driving T cells in situ may therefore be a useful approach in the treatment of inflammatory and malignant skin diseases. Depletion of CD4(+) T cells in intact inflamed human skin tissue by Zanolimumab, a fully human therapeutic monoclonal antibody (IgG1, kappa) against CD4, was studied in a human psoriasis xenograft mouse model. Zanolimumab treatment was shown to induce a significant reduction in the numbers of inflammatory mononuclear cells in upper dermis. This reduction in inflammatory mononuclear cells in situ was primarily due to a significant reduction in the numbers of skin-infiltrating CD4(+), but not CD8(+) CD3(+) T cells. The capacity of Zanolimumab to deplete the CD4(+) T cells in the skin may be of importance in diseases where CD4(+) T cells play a central role. Indeed, in a phase II clinical trial Zanolimumab has shown a dose-dependent clinical response in patients with CTCL and the antibody is currently in a phase III clinical trial for CTCL, a disease for which there is no safe and effective treatment available today.

Biologic agents in psoriasis

This paper reviews the new biologic agents that selectively block the immunologic steps implicated in the pathogenesis of psoriasis. Four strategies have been targeted: reduction of the number of pathogenic T cells; inhibition of T-cell activation and migration; modulation of the immune system; and blockage of the activity of inflammatory cytokines. There are three classes: monoclonal antibodies, fusion proteins and recombinant cytokines or growth factors. The actions, efficacy and side-effect profile of the biologic agents, alefacept, efalizumab, etanercept and infliximab, are reviewed.

Nitric oxide levels in patients with psoriasis treated with methotrexate

Psoriasis is a chronic, recurrent, inflammatory, and hyperproliferative disease. Recently there have been studies regarding increases in the levels of NO in inflammatory dermatoses including psoriasis. In this study, 22 patients with psoriasis were scored with PASI (psoriasis area and severity index) and the levels of serum nitrite-nitrate were evaluated before and after therapy with methotrexate (Mtx). The results were compared with age- and sex-matched healthy volunteers. The relation of the results with the clinical severity and the cumulative Mtx dose were also evaluated. The serum levels of nitrite-nitrate of the psoriatic patients with active lesions were found to be significantly higher than the levels of the healthy volunteers and the patients after therapy. The elevated nitrite-nitrate serum levels in the inflammatory period may suggest the possible role of this mediator in the etiopathogenesis of psoriasis and the potential future use of No inhibitors in the treatment of psoriasis.

An Anti-IL-12p40 Antibody Down-Regulates Type 1 Cytokines, Chemokines, and IL-12/IL-23 in Psoriasis

Psoriasis is characterized by activation of T cells with a type 1 cytokine profile. IL-12 and IL-23 produced by APCs are essential for inducing Th1 effector cells. Promising clinical results of administration of an Ab specific for the p40 subunit of IL-12 and IL-23 (anti-IL-12p40) have been reported recently. This study evaluated histological changes and mRNA expression of relevant cytokines and chemokines in psoriatic skin lesions following a single administration of anti-IL-12p40, using immunohistochemistry and real-time RT-PCR. Expression levels of type 1 cytokine (IFN-gamma) and chemokines (IL-8, IFN-gamma-inducible protein-10, and MCP-1) were significantly reduced at 2 wk posttreatment. The rapid decrease of these expression levels preceded clinical response and histologic changes. Interestingly, the level of an anti-inflammatory cytokine, IL-10, was also significantly reduced. Significant reductions in TNF-alpha levels and infiltrating T cells were observed in high responders (improvement in clinical score, > or =75% at 16 wk), but not in low responders. Of importance, the levels of APC cytokines, IL-12p40 and IL-23p19, were significantly decreased in both responder populations, with larger decreases in high responders. In addition, baseline levels of TNF-alpha significantly correlated with the clinical improvement at 16 wk, suggesting that these levels may predict therapeutic responsiveness to anti-IL-12p40. Thus, in a human Th1-mediated disease, blockade of APC cytokines by anti-IL-12p40 down-regulates expression of type 1 cytokines and chemokines that are downstream of IL-12/IL-23, and also IL-12/IL-23 themselves, with a pattern indicative of coordinated deactivation of APCs and Th1 cells.

Misbehaving macrophages in the pathogenesis of psoriasis

Psoriasis is a chronic inflammatory skin disease unique to humans. In this issue of the JCI, 2 studies of very different mouse models of psoriasis both report that macrophages play a key role in inducing psoriasis-like skin disease. Psoriasis is clearly a polygenic, inherited disease of uncontrolled cutaneous inflammation. The debate that currently rages in the field is whether psoriasis is a disease of autoreactive T cells or whether it reflects an intrinsic defect within the skin--or both. However, these questions have proven difficult to dissect using molecular genetic tools. In the current studies, the authors have used 2 different animal models to address the role of macrophages in disease pathogenesis: Wang et al. use a mouse model in which inflammation is T cell dependent, whereas the model used by Stratis et al. is T cell independent (see the related articles beginning on pages 2105 and 2094, respectively). Strikingly, both groups report an important contribution by macrophages, implying that macrophages can contribute to both epithelial-based and T cell-mediated pathways of inflammation.

Activated macrophages are essential in a murine model for T cell-mediated chronic psoriasiform skin inflammation

The CD18 hypomorphic (CD18hypo) PL/J mouse model clinically resembling human psoriasis is characterized by reduced expression of the common chain of beta2 integrins (CD11/CD18) to only 2-16% of WT levels. Previously we found that this chronic psoriasiform skin inflammation also depends on the presence of CD4+ T cells. Herein we investigated the role of macrophages in this CD18hypo mouse model. Activated macrophages were significantly increased in lesional skin as well as in inflamed skin draining lymph nodes (DLNs) of affected CD18hypo mice and were identified as being an important source of TNF-alpha in vivo. Both depletion of macrophages and neutralization of TNF-alpha resulted in a significant alleviation of psoriasiform skin inflammation. As monocyte chemotactic protein 1 was enhanced in lesional skin of affected CD18hypo mice, we intradermally injected recombinant murine monocyte chemotactic protein-1 (rJE/MCP-1) alone or in combination with rTNF-alpha into the skin of healthy CD18hypo mice. Only simultaneous injection of rJE/MCP-1 and rTNF-alpha, but neither substance alone, resulted in the induction of psoriasiform skin inflammation around the injection sites with recruitment and activation of macrophages. Collectively, our data suggest that maintenance of psoriasiform skin inflammation critically depends on efficient recruitment and activation of macrophages with sufficient release of TNF-alpha.

STAT-6-mediated control of P-selectin by substance P and interleukin-4 in human dermal endothelial cells

P-Selectin expressed on endothelial cells contributes to acute and chronic inflammation by promoting leukocyte tethering/rolling. Despite increasing evidence of P-selectin expression on human umbilical vein endothelial cells in vitro, the regulatory mechanisms of P-selectin expression on dermal endothelial cells in skin diseases are not fully understood. Here, we demonstrate increased expression of P-selectin in dermal vessels of regional skin in urticaria and atopic dermatitis. The present in vitro analyses with human dermal microvascular endothelial cells (HDMECs) revealed that histamine rapidly induced P-selectin expression. Interleukin (IL)-4 and IL-13 induced prolonged expression of surface P-selectin by HDMECs. A combination of tumor necrosis factor-alpha and IL-4 inhibited P-selectin expression. Pretreatment of HDMECs with tumor necrosis factor-alpha followed by incubation with IL-4 markedly increased P-selectin expression. Notably, incubation with substance P alone induced prolonged P-selectin expression. Activation of STAT6 appears to be a key factor in P-selectin expression induced by substance P and IL-4 because treatment with STAT6 decoy oligodeoxynucleotides significantly inhibited P-selectin expression. The present results indicate that novel, complex mechanisms are involved in endothelial P-selectin expression in the skin. STAT6 in dermal endothelial cells appears to be a potent target for controlling cellular infiltrate in allergic and/or neuroinflammatory skin diseases.

Psoriasis is associated with lipid abnormalities at the onset of skin disease

BACKGROUND

Psoriasis appears to have increased cardiovascular morbidity. The underlying pathogenetic mechanisms remain unclear. Multiple factors, including systemic inflammation, oxidative stress, aberrant lipid profile, and concomitant established risk factors, have been discussed. However, previous studies consist of heterogeneous patient materials, including persons with highly varying disease duration and treatment.

METHODS

Two-hundred patients were investigated at the onset of psoriasis, comparing plasma concentrations of lipids, lipoproteins, and apolipoproteins with those of matched controls (N = 285).

RESULTS

Psoriasis patients manifest significant lipid abnormalities. Specifically, patients had significantly higher cholesterol concentrations in the very-low-density lipoprotein and high-density-lipoprotein fractions. Adjustment for established environmental risk factors did not affect the results.

LIMITATION

The response rate among control subjects was low. However, an additional analysis of a random subset of nonresponders demonstrated no substantial differences in the main results.

CONCLUSION

The study supports the notion that lipid abnormalities in psoriasis may be genetically determined rather than acquired.

Dramatic improvement of psoriatic erythroderma after acute hepatitis: analysis of cytokine synthesis capability in peripheral blood T cells

We report a patient with psoriasis and hepatitis C virus infection who initially presented with psoriatic erythroderma and eventually showed complete clearance of psoriatic lesions following acute hepatitis induced by etretinate treatment. Cytokine synthesis capabilities in peripheral blood T cells obtained at different stages were evaluated in this patient. A dramatic increase in the frequency of interferon-gamma-producing CD8+ T cells in peripheral blood was observed during the erythrodermic stage. In contrast, the frequencies of interleukin (IL)-4- and IL-13-producing CD4+ T and CD8+ T cells were remarkably high at the resolution stage. These results clearly indicate that a shift towards type 2 cytokine predominance contributes to the resolution of severe psoriasis.

Immunological aspects of pregnancy

Alterations to the immune status of the pregnant woman are necessary to allow mothers to tolerate genetically different fetal tissues during pregnancy. These alterations lead to impaired cell-mediated immunity with increased susceptibility to certain infections such as tuberculosis. During pregnancy, the maternal immune system also shows a relative bias toward T helper type 2 immunity. Several inflammatory dermatoses are either unique to pregnancy or altered by the pregnant state. Immunologists are now beginning to understand the various factors that contribute to the maternal immune tolerance and, in particular, the role of classic (human leukocyte antigen [HLA]-A, HLA-B, HLA-C, and HLA-D) and non-classic (HLA-E, HLA-F, and HLA-G) major histocompatability antigens in this process. Human leukocyte antigen-G, in particular, seems to be important in protecting HLA mismatched tissue from the innate immune system, and investigation of HLA-G expression may help to explain how pregnancy affects inflammatory skin disease. Immunologists are now beginning to understand the alterations to the immune status of the pregnant woman that are necessary to allow mothers to tolerate genetically different fetal tissues during pregnancy. These alterations may help to explain how pregnancy effects inflammatory skin disease.

Psoriasis confined strictly to vitiligo areas - a Koebner-like phenomenon?

Vitiligo and psoriasis are both common skin disorders. However, psoriasis strictly confined to pre-existing vitiligo areas is rare and suggests a causal relationship. We report here on two patients with a strict anatomical colocalization of vitiligo and psoriasis. The histopathological examinations showed typical changes for both diseases together with a dense infiltrate of CD4+ and CD8+ T cells. By immunohistochemistry, intracytoplasmatic granzyme B and tumour necrosis factor alpha (TNF-alpha) were detected within the T-cell population, suggesting the functional activity of these cells and the creation of a local T helper 1 (Th1)-cytokine milieu. Additionally, in one patient we could identify anti-melanocytic T cells by tetramer staining and enzyme-linked immunospot (ELISPOT) analysis. These skin-infiltrating lymphocytes might trigger, by the local production of Th-1 cytokines such as TNF-alpha and interferon-gamma (IFN-gamma), the eruption of psoriatic plaques in patients with a genetic predisposition for psoriasis.

Phototherapy: how does UV work?

Phototherapy has been largely empirical. Thus, despite the long term use its mechanisms of action are quite unclear. Because of the recent achievements in photoimmunology and molecular photobiology we are now beginning to understand some of the mechanisms. Many of the effects are certainly mediated via induction of apoptotic cell death. Another major mechanism is the induction of immunosuppression. This review primarily focuses on recent advances in photoimmunology which will contribute to the further understanding how phototherapy acts.

PsEma--a hitherto unnamed dermatologic entity with clinical features of both psoriasis and eczema

INTRODUCTION

Recent advances in molecular biology have helped establish differences between psoriasis and a group of inflammatory skin disorders commonly referred to as eczema. The authors have observed significant overlap between these two conditions such that a distinction between them may not always be made, even with histologic examination of skin biopsy specimens.

OBJECTIVE

To determine how frequently psoriasis patients present features of both psoriasis and eczema.

METHODS

The authors conducted a prospective analysis of 100 consecutive psoriasis patients in their clinic.

RESULTS

The authors found that 20% could be diagnosed as "intermediate," having lesions with characteristics of both psoriasis and eczema, or a personal history of both. The authors suggest naming this category of inflammatory dermatosis "PsEma"--an overlap condition in which the clinical, histologic, molecular, biologic, and therapeutic responses show characteristics of both psoriasis and eczema.

T Cell-Regulated Neutrophilic Inflammation in Autoinflammatory Diseases

Previous studies of acute generalized exanthematous pustulosis, a peculiar drug hypersensitivity reaction, suggested that CXCL8-producing T cells regulate sterile, polymorphonuclear neutrophil-rich skin inflammations. In this study, we test the hypothesis of whether CXCL8-producing T cells are present in autoinflammatory diseases like pustular psoriasis and Behçet's disease. Immunohistochemistry of normal skin revealed few CD4+ and CD8+ T cells, few CXCL8+ cells, and no neutrophilic infiltration, whereas in acute exacerbations of atopic dermatitis, numerous CD4+ T cells but few CD8+ T cells, neutrophils, or CXCL8+ cells were detected. In contrast, a pronounced infiltration of neutrophils and of predominantly CD4+ T cells was observed in skin biopsies from pustular psoriasis, Behçet's disease, and acute generalized exanthematous pustulosis, with infiltrating T cells strongly positive for CXCL8 and the chemokine receptor CCR6. Skin-derived T cell clones from pustular skin reactions were positive for CCR6 but negative for CCR8 and secreted high amounts of CXCL8 and GM-CSF, often together with IFN-gamma and TNF-alpha after in vitro stimulation. Moreover, some skin-derived T cell clones from Behçet's disease and from pustular psoriasis predominantly produced CXCL8 and GM-CSF, but failed to secrete IL-5 and IFN-gamma. These cells might represent a particular subset as they differ from both Th1 as well as Th2 T cells and are associated with a unique, neutrophil-rich sterile inflammation. Our findings suggest that CXCL8/GM-CSF-producing T cells may orchestrate neutrophil-rich pathologies of chronic autoinflammatory diseases like pustular psoriasis and Behçet's disease.

Increased Sensitivity to Interferon-α in Psoriatic T Cells

Psoriasis is a chronic inflammatory skin disease characterized by abnormal epidermal proliferation. Several studies have shown that skin-infiltrating activated T cells and cytokines play a pivotal role during the initiation and maintenance of the disease. Interferon (IFN)-alpha plays an important role in host defense against infections, but recent data have also implicated IFN-alpha in psoriasis. Thus, IFN-alpha induces or aggravates psoriasis in some patients, and mice lacking a transcriptional attenuator of IFN-alpha/beta signaling spontaneously develop a psoriasis-like inflammatory skin disease characterized by CD8(+)-infiltrating T cells. In this study, we therefore investigate IFN-alpha signaling in T cells isolated from involved skin of psoriatic patients. We show that psoriatic T cells have increased and prolonged responses to IFN-alpha, on the level of signal transducers and activators of transcription (STAT) activation, compared with infiltrating T cells from skin of non-psoriatic donors. Functionally, the increased IFN-alpha signaling leads to an increased binding of STAT4 to the IFN-gamma promotor, IFN-gamma production, and inhibition of T cell growth. In contrast, to STAT responses to other cytokines were not changed in psoriasis. In conclusion, we provide evidence that psoriatic T cells have an increased sensitivity to IFN-alpha. Thus, our data suggest that increased IFN-alpha signaling is involved in the pathogenesis of psoriasis.

Plaque psoriasis vs. atopic dermatitis and lichen planus: a comparison for lesional T-cell subsets, epidermal proliferation and differentiation

BACKGROUND

T-cell infiltration in plaque psoriasis has recently been an important subject of investigation. Interestingly, comparative analyses of the disease-specific composition of the lesional T-cell infiltrate in plaque psoriasis and other inflammatory dermatoses have only sparsely been performed.

OBJECTIVES

To compare plaque psoriasis vs. atopic dermatitis and lichen ruber planus with respect to T-cell subsets, epidermal proliferation and keratinization.

PATIENTS AND METHODS

Biopsies were taken from untreated lesional skin of patients, six with psoriasis, six with atopic dermatitis and six with lichen planus. T-cell subsets (CD4+, CD8+, CD45RO+, CD45RA+, CD2+, CD25+), an epidermal proliferation (Ki-67) and a keratinization marker (K10) were stained immunohistochemically and quantified using image analysis.

RESULTS

The high number of CD8+ T cells (52 +/- 13 cells mm(-1)) found in the psoriatic epidermis was not found in the epidermis of atopic dermatitis (9 +/- 4), nor in the epidermis of lichen planus (34 +/- 10). The other T-cell subsets in the epidermis and dermis showed no statistically significant differences between psoriasis and atopic dermatitis. In contrast to the limited presence of CD4+, CD8+ and CD2+ in the psoriatic dermis (110 +/- 19, 27 +/- 9, 127 +/- 41, cells mm(-1), respectively), more impressive numbers of these cells were observed in the dermis of lichen planus (300 +/- 53, 144 +/- 38, 272 +/- 48, respectively). CD45RO+ memory effector T-cell counts were significantly higher in the epidermis of lichen planus (39 +/- 10) than in psoriasis (19 +/- 5). Psoriatic epidermis proved to have major keratinocyte hyperproliferation (247 +/- 26 cells mm(-1) lamina basalis), as compared with atopic dermatitis (134 +/- 15) and lichen planus (128 +/- 20). Furthermore, a marked decreased expression of keratin 10 was observed in psoriasis (41% of epidermal area) contrary to atopic dermatitis (70%).

CONCLUSIONS

Psoriatic epidermis exhibits a pronounced CD8+ epidermotropism with accompanying epidermal hyperproliferation and abnormal keratinization, which changes are only minimally expressed in atopic dermatitis and lichen planus. In plaque psoriasis, substantially fewer activated CD4+ and CD8+ T cells in the dermis and less CD45RO+ T cells in the epidermis are present in comparison with lichen ruber planus.

The therapeutic effects of vitamin D3 and its analogues in psoriasis

Psoriasis is a common skin disease which is characterised by the proliferation and abnormal differentiation of keratinocytes, coupled with complex immune disturbances. The beneficial effects of vitamin D derivatives in this disease are due to their capacity to inhibit proliferation, their ability to induce normal differentiation and their immunomodulatory properties. Since the systemic administration of these compounds is limited by their effect on calcium metabolism, topical preparations have become available in most countries. Topical calcipotriol and/or tacalcitol are now considered as first-line treatment for mild-to-moderate psoriasis and can be taken in combination with other systemic therapies in more severe cases of the disease. Novel orally active vitamin D analogues, with minimal calcitropic effercts, are, however, required for more effective treatment.

Analysis of T cell receptor alpha-chain variable region (Valpha) usage and CDR3alpha of T cells infiltrated into lesions of psoriasis patients

Psoriasis is a common inflammatory skin disease and is considered as T cell-mediated immune response. In this study, we analyzed T cell receptor alpha-chain variable region (TCR Valpha) usage in the lesions of psoriasis patients using 5'-RACE. As the results, Valpha1, -2, -7, -8, -10, -11, -12, and -23 were commonly detected in psoriatic lesions and comparison of expressions of these Valpha types between psoriasis patients and healthy individuals showed that Valpha1, -7, -11, and -12 were highly increased in psoriasis patients than in healthy individuals. Compared with atopy dermatitis patients, the expressions of Valpha1 and Valpha7 were increased in psoriasis patients. Then, to identify CDR3alpha of T cells infiltrated in psoriatic lesions, we examined which type of J gene segment was rearranged with Valpha1 or Valpha7, which the expressions was specifically increased in psoriatic lesions. The result showed that the V-J rearrangements between the examined patients were not equivalent and their frequencies were diverse, however, several common rearrangements such as Valpha1-Jalpha13, -23, -27, or -34 and Valpha7-Jalpha12, -33 were detected. The results in this study might provide the clue to define the characteristics of T cells associated with the pathogenesis of psoriasis.

The Psoriasis Area and Severity Index Is the Adequate Criterion to Define Severity in Chronic Plaque-Type Psoriasis

BACKGROUND

Chronic plaque-type psoriasis is a major dermatosis, but a significant question is still unanswered: What defines severity in chronic plaque-type psoriasis? While objective assessments like the Psoriasis Area and Severity Index (PASI) have frequently been used in clinical trials, quality of life (QOL) questionnaires are currently becoming more and more popular.

OBJECTIVE

This article summarizes the most important objective and subjective measurements of severity in psoriasis. For every dermatologist it is critically important to distinguish between severe psoriasis and psoriasis that severely affects QOL. Even if the PASI also has disadvantages, it is the most adequate instrument available to evaluate severity in plaque-type psoriasis.

RESULT

We provide reasons why PASI >12 defines severe, PASI 7-12 moderate and PASI <7 mild chronic plaque-type psoriasis.

Compartmental imbalance and aberrant immune function of blood CD123+ (plasmacytoid) and CD11c+ (myeloid) dendritic cells in atopic dermatitis

Atopic dermatitis (AD) is a pruritic, chronically relapsing skin disease in which Th2 cells play a crucial role in cutaneous and extracutaneous immune reactions. In humans, CD11c+CD123- myeloid dendritic cells (mDC) and CD11c-CD123+ plasmacytoid DC (pDC) orchestrate the decision-making process in innate and acquired immunity. Since the number and function of these blood dendritic cell (DC) subsets reportedly reflect the host immune status, we studied the involvement of the DC subsets in the pathogenesis of AD. Patients with AD had an increased DC number and a low mDC:pDC ratio with pDC outnumbering mDC in the peripheral blood compared with normal subjects and psoriasis patients (a Th1 disease model group). The mDC:pDC ratio was correlated with the total serum IgE level, the ratio of IFN-gamma-producing blood cells:IL-4-producing blood cells, and the disease severity. In vitro allogeneic stimulation of naive CD4+ cells with atopic DC showed that the ability of pDC for Th1 induction was superior or comparable to that of mDC. In skin lesions, pDC infiltration was in close association with blood vessels expressing peripheral neural addressins. Therefore, compartmental imbalance and aberrant immune function of the blood DC subsets may deviate the Th1/Th2 differentiation and thus induce protracted allergic responses in AD.

Psoriasis treatment: current and emerging directed therapies

Quality of life studies in patients with cutaneous psoriasis attest to its significant impact on day to day activities and personal social interactions. Up to 40% of patients with psoriasis may develop psoriatic arthritis, usually within 5-10 years after onset of the cutaneous disease, heightening quality of life issues. These data have prompted an increased awareness and interest in more aggressive management of psoriasis; coupled with a better understanding of immunopathogenesis, this has led to the development of new agents targeting specific cells and molecules involved in the development and maintenance of psoriatic plaques. Although non-biological therapies, including methotrexate and ciclosporin, show significant efficacy their side effect profiles have precluded their long term use for moderate to severe psoriasis. This review concentrates on new biological agents, focusing on the three agents approved for psoriasis within the past 18 months (alefacept, efalizumab, and etanercept). Phase II and III trial data on other agents in development (adalimumab and infliximab) are also presented. Surveys show many patients want to be treated more aggressively. It is hoped that the introduction of new agents that are more targeted and that hold the promise of fewer side effects will cause patients and their physicians to reconsider systemic treatment and, as a consequence, stimulate other patients to reconsider treatment for psoriasis. Close cooperation between dermatologists and rheumatologists, particularly in the area of psoriatic joint disease, will enhance these considerations.

Therapeutic potential of macrolide immunosuppressants in dermatology

Dermatologists are frequently presented with inflammatory dermatoses that are responsive to treatment with immunomodulating drugs. Corticosteroids, particularly when applied topically, have been the mainstay of treatment in the past. Their undoubted efficacy, however, has been undermined by problems with repeated use including tachyphylaxis and side effects such as skin atrophy and hypertension. Macrolide immunosuppressive drugs, originally used for prophylaxis of organ transplant rejection, have been shown to be effective in the treatment of inflammatory dermatoses. The original drugs used in dermatology in this class have their own limitations including poor absorption when used topically and their distinct side-effect profiles. A search for other immunosuppressive macrolide antibiotics has led to the development of new agents, which have enhanced profiles for the treatment of skin disease. This review discusses the main dermatoses that may be targeted by this class of drugs and summarises the topical and systemic macrolides either currently in use, in clinical trials or preclinical development.

Gene expression profiles in psoriasis: analysis of impact of body site location and clinical severity

BACKGROUND

Psoriasis is characterized by symmetry of plaques and modulation of multiple genes within those plaques.

OBJECTIVES

We compared gene expression profiles of plaques of psoriasis at different anatomical sites for both symmetrical and asymmetrical disease to ascertain whether the same genes were expressed.

METHODS

Gene expression profiles were analysed in biopsies from lesional and uninvolved skin from two groups of patients with either predominantly symmetrical or truncal plaques of psoriasis vulgaris, and from normal skin of healthy volunteers. Genomic analyses were performed using cDNA array and kinetically monitored reverse transcriptase-initiated polymerase chain reaction (kRT-PCR) approaches. A cluster of genes upregulated in involved psoriasis skin as compared with normal skin was identified using each of these two technologies.

RESULTS

Clustering of patients based on their gene expression profile did not reveal any correlation with family history of psoriasis, age at onset or association of psoriasis with arthritis. There was no difference in gene expression profile between the type (symmetrical vs. truncal) or location (left vs. right side of body) of psoriatic plaques. Gene expression profiles of involved psoriatic skin analysed by kRT-PCR analysis did correlate with both global (Psoriasis Area and Severity Index) and local (erythema, desquamation and plaque elevation) clinical severity.

CONCLUSIONS

These results indicate that it may be feasible to analyse the molecular effects of pharmacological agents on psoriatic skin in 'minizone' protocols, that the obtained data can be correlated with clinical severity and that plaques of psoriasis in the same individual express the same genes.

Novel biologic therapies for psoriasis

There has been a recent explosion in knowledge regarding the central role of the immune system in the pathogenesis of psoriasis. Originally felt to be primarily a disorder of keratinocyte hyperproliferation, it has recently been classified as a T cell-mediated, autoimmune disease. Type 1 cytokines released predominantly from activated T lymphocytes are now considered to cause the psoriatic phenotype, including the epidermal and vascular changes. Armed with this new knowledge, pharmaceutical and biotechnology companies have developed more specific, immunologically directed interventions. These newer agents aim to be both more effective in clearing a condition that is associated with much morbidity and to be more selective, resulting in fewer toxic side effects than current therapies. This article gives an overview of the newer immunotherapeutic approaches from the points of view of safety, efficacy and mechanisms of action. The review also outlines the steps involved in the immune response leading to psoriasis and considers how each step could offer a target for therapeutic intervention. Infliximab, etanercept, alefacept and efalizumab are considered in detail.

Intracellular IFN-gamma production and IL-12 serum levels in latent autoimmune diabetes of adults (LADA) and in type 2 diabetes

Th1 cytokines, such as interleukin-2 (IL-2) and interferon-gamma (IFN-gamma), and Th1-inducing cytokines, such as IL-12, are involved in the pathogenesis of various organ-specific autoimmune diseases, including autoimmune diabetes. In this study, we investigated intracellular IFN-gamma release by T lymphocytes and IL-12 serum levels in 48 type 2 and 36 latent autoimmune diabetes of adults (LADA) diabetics and 25 control subjects in an attempt to evaluate their role in the pathogenesis of these clinical entities. Ionomycin (ION) and phorbol-12-myristate-13-acetate (PMA)-activated peripheral blood mononuclear cells (PBMCs) were stained with anti-CD4-FITC or anti-CD8-FITC and anti-IFN-gamma phycoerythrin (PE) monoclonal antibodies (mAbs) and analyzed by flow cytometry. IL-12 serum levels were determined by enzyme-linked immunosorbent assay (ELISA). In all study groups, IFN-gamma content of CD4(+) and CD8(+) lymphocytes was significantly upregulated by stimulation. Furthermore, it was observed that CD4(+) and CD8(+) lymphocytes from type 2 diabetics produced significantly lower levels of IFN-gamma compared with LADA patients and controls. However, the percentages of CD4(+)/IFN-gamma(+) and CD8(+)/IFN-gamma(+) cells from type 2 diabetics were significantly higher compared with controls. The flow cytometric picture of intracellular IFN-gamma release in LADA patients did not differ from that observed in controls. However, IL-12 serum levels in type 2 and LADA diabetics were lower than in controls. Because Th1 cytokines have been associated with the pathogenesis of autoimmune diabetes, these results preclude Th1 involvement in the autoimmune phenomena observed in LADA patients. In contrast, the low IFN-gamma levels observed in type 2 diabetics in combination with the low IL-12 serum levels might be a contributing factor in the frequently observed chronic complications in these patients.

Overview of psoriasis

Psoriasis is a chronic disease that affects the skin and joints. Clinical hallmarks comprise erythematous plaques covered by silvery scaling and a chronic recurrent course. Histologically, psoriasis is characterized by the hyperproliferation of the epidermis, elongated and prominent blood vessels and a thick perivascular lymphocytic infiltrate. Psoriasis is now considered an auto-immune disease. Although many different therapies are available, there is clearly a need for new treatments. Our improvement of understanding of the pathogenesis of psoriasis together with the possibility to develop bioactive proteins ("biologicals") targeted at specific steps in the pathogenesis of psoriasis, have opened a new field of promising future treatments. In the development and assessment of new therapeutical modalities for psoriasis, a clear definition of a patient's psoriasis severity is essential. The impact of a given therapy can only then be evaluated, based on the changes in the severity score during and after application of the treatment.

From laboratory to clinic: rationale for biologic therapy

Traditional systemic therapy for psoriasis is limited by either lack of efficacy or the long-term side effect profile of the medications used. Newer information about the pathophysiology of the disease has led to new perspectives on developing novel techniques for attacking psoriasis. This article discusses the pathogenesis of psoriasis, looks at the immunologic factors that contribute to forming a psoriatic plaque, reviews how novel biologic therapies are made, and explores how biologics can target each of these specific parts of the immunologic cascade.

Psoriasis: future research needs and goals for the twenty-first century

Psoriasis research is entering a new era. Progress in delineating immunogenetics and pathomechanisms of disease brings with it a need to understand fully the clinical spectrum of disease and integrate phenotype with genomics and proteomics. Involvement of patient groups and an understanding of the psychosocial aspects of psoriasis, particularly its significant impairment of quality of life, are keys to progress. The biologic revolution in therapy of inflammatory disease has embraced psoriasis bringing with it an urgent need for evidence-base, consensus on outcome measures, and long-term real-life studies.A concerted effort between academia, industry, and patients will take forward the understanding of, and therapy for, psoriasis.

Psoriasis vulgaris: an interplay of T lymphocytes, dendritic cells, and inflammatory cytokines in pathogenesis

PURPOSE OF REVIEW

Discuss and update concepts and hypotheses for the pathogenesis of psoriasis based on new research reports (primarily from 2003 and early 2004).

RECENT FINDINGS

Increases in newly defined dendritic cell subsets, cytokines, and chemokines have been identified in psoriasis lesions and have modified views of T-cell-mediated pathogenesis. In addition, the psoriasis transcriptome has been defined by large-scale genomic expression studies, and these data suggest distinct molecular mechanisms of type 1 T-cell-mediated inflammation. Somewhat surprisingly, therapeutic clinical trials suggest that tumor necrosis factor is a major pathogenic cytokine in psoriasis, whereas translational studies point to roles of other innate pathways mediated by heat shock proteins, glycolipids, natural killer T cells, or dendritic cells in disease pathogenesis.

SUMMARY

An interactive network of inflammatory cytokines, chemokines, dendritic cells, and type 1 T cells or natural killer T cells potentially drives pathogenic inflammation in psoriasis vulgaris. Continued clinical studies with defined immune antagonists provide a critical means to dissect the contribution of different cell subsets and genomic pathways to the pathogenesis of psoriasis vulgaris.

Current concepts in the immunopathogenesis of psoriasis

There is much evidence to support the concept that psoriasis is a type 1 autoimmune disease, primarily mediated by interferon gamma and other inflammatory cytokines. There has been renewed interest in the role of components of the innate immune system, however,and it may be that overlap between the innate and acquired arms of the immune system can better explain immunopathogenesis in psoriasis. Relevant cell types, receptors, and immune mediators within these traditional boundaries of the immune system are discussed.Finally, pathogenic contributions from important psoriatic mouse models and recent genomic data using the new gene chip technology are elaborated.

Recent insights into the immunopathogenesis of psoriasis provide new therapeutic opportunities

Chronic and excessive inflammation in skin and joints causes significant morbidity in psoriasis patients. As a prevalent T lymphocyte-mediated disorder, psoriasis, as well as the side effects associated with its treatment, affects patients globally. In this review, recent progress is discussed in the areas of genetics, the immunological synapse, the untangling of the cytokine web and signaling pathways, xenotransplantation models, and the growing use of selectively targeted therapies. Since psoriasis is currently incurable, new management strategies are proposed to replace previous serendipitous approaches. Such strategic transition from serendipity to the use of novel selective agents aimed at defined targets in psoriatic lesions is moving rapidly from research benches to the bedsides of patients with this chronic and debilitating disease.

Recent insights into the immunopathogenesis of psoriasis provide new therapeutic opportunities

Chronic and excessive inflammation in skin and joints causes significant morbidity in psoriasis patients. As a prevalent T lymphocyte-mediated disorder, psoriasis, as well as the side effects associated with its treatment, affects patients globally. In this review, recent progress is discussed in the areas of genetics, the immunological synapse, the untangling of the cytokine web and signaling pathways, xenotransplantation models, and the growing use of selectively targeted therapies. Since psoriasis is currently incurable, new management strategies are proposed to replace previous serendipitous approaches. Such strategic transition from serendipity to the use of novel selective agents aimed at defined targets in psoriatic lesions is moving rapidly from research benches to the bedsides of patients with this chronic and debilitating disease.