Potential role of the chemokine receptors CXCR3, CCR4, and the integrin alphaEbeta7 in the pathogenesis of psoriasis vulgaris

Survenue d’un psoriasis au cours d’un traitement par infliximab pour fasciite de Shulman

BACKGROUND

Anti-TNFalpha drugs are used in certain rheumatologic and gastrointestinal inflammatory diseases and are also effective in cutaneous psoriasis. Several case reports have recently been published concerning induction of paradoxical psoriasis during the course of anti-TNF therapy. We report a new case involving infliximab used to treat Shulman fasciitis.

CASE REPORT

A 39-year-old woman was treated with infliximab for corticoid-dependent Shulman fasciitis. No personal or familial cutaneous psoriasis was noted in her history. Two months after the third infusion, she developed psoriasis vulgaris and pustular palmoplantar psoriasis which improved under topical corticosteroids. Her psoriatic lesions worsened one month after the first maintenance infusion. Since the Shulman fasciitis was not under control, infliximab was withdrawn and replaced with azathioprine. Six months later, her psoriasis was in remission and the Shulman fasciitis was under control.

DISCUSSION

TNFalpha plays an important role in the physiopathology of psoriasis through its action on inflammatory infiltrate, angiogenesis and keratinocyte proliferation. Several studies have reported the efficiency of TNFalpha inhibitors in moderate to severe cutaneous psoriasis. However, fourteen cases of induction or worsening of psoriasis have been reported with these drugs, suggesting a class effect. We report a new case of cutaneous psoriasis induced by infliximab in a patient presenting corticoid-dependent Shulman fasciitis, and we discuss the possible immunological mechanisms responsible for this paradoxical side effect. Other cutaneous lesions have been reported during treatment with TNFalpha inhibitors. The benefits of this treatment on the underlying inflammatory disease must be balanced against the potential cutaneous side effects when deciding whether to continue with anti-TNFalpha treatment.

The chemokine receptor CXCR3 attenuates the control of chronic Mycobacterium tuberculosis infection in BALB/c mice

The chemokine receptor CXCR3 plays a significant role in regulating the migration of Th1 cells. Given the importance of Th1 immunity in the control of tuberculous infection, the results of the present study demonstrating that CXCR3-deficient BALB/c mice are more resistant to Mycobacterium tuberculosis, compared with wild-type mice, is surprising. This enhanced resistance manifests in the chronic but not the acute phase of infection. Remarkable differences in the cellular composition of the pulmonic granuloma of the CXCR3(-/-) and wild-type mice were found, the most striking being the increase in the number of CD4(+) T cells in the knockout strain. In the chronic phase of infection, the number of CD69-expressing CD4(+) T lymphocytes in the lungs of CXCR3(-/-) mice was higher than in wild-type mice. Additionally, at 1 mo postinfection, the number of IFN-gamma-producing CD4(+) T cells in the lungs and mediastinal lymph nodes of the CXCR3-deficient strain was elevated compared with wild-type mice. Pulmonic expression of IFN-gamma, IL-12, TNF-alpha, or NO synthase 2, the principal antimycobacterial factors, were equivalent in the two mouse strains. These results indicate that: 1) CXCR3 plays a role in modulating the cellular composition of tuberculous granuloma; 2) CXCR3 impairs antimycobacterial activity in chronic tuberculosis; and 3) in the absence of CXCR3, mice exhibit a heightened state of CD4(+) T lymphocyte activation in the chronic phase of infection that is associated with enhanced CD4(+) T cell priming. Therefore, CXCR3 can attenuate the host immune response to M. tuberculosis by adversely affecting T cell priming.

Expression pattern of chemokine receptors and chemokine release in inflammatory erythroderma and Sézary syndrome

BACKGROUND

Erythroderma can be caused by inflammatory dermatoses or cutaneous T-cell lymphoma. Even if chemokines and their receptors are involved in the skin-selective lymphocyte recruitment, their role in inflammatory erythroderma is yet unclear.

OBJECTIVE

To evaluate the chemokine release (TARC, MDC, IP-10) and to define the expression pattern of Th1- (CCR5, CXCR3) and Th2-related (CCR4) chemokine receptors in inflammatory erythroderma and Sézary syndrome (SS).

MATERIALS AND METHODS

Flow cytometry has been carried out on both circulating and skin-infiltrating T lymphocytes; serum chemokine levels have been evaluated using ELISA techniques.

RESULTS

CCR4, CCR5 and CXCR3 were expressed on about 40% of peripheral blood lymphocytes and on the majority of skin-infiltrating lymphocytes in the inflammatory erythroderma patients, whereas the leukemic CD4+CD26- subpopulation in SS was characterized by a high CCR4 expression without a concurrent increase in CCR5 or CXCR3. TARC, MDC and IP-10 serum levels were significantly increased in both erythrodermic and SS patients.

CONCLUSIONS

Our results confirm that SS is a Th2 disorder with a selective expression of CCR4, whereas inflammatory erythroderma shares an overexpression of both Th1- and Th2-related chemokine receptors, suggesting an activation of different pathways driving reactive lymphocytes to the skin.

DCs metabolize sunlight-induced vitamin D3 to 'program' T cell attraction to the epidermal chemokine CCL27

During adaptive immune responses, dendritic cells activate T cells and endow them with specific homing properties. Mechanisms that 'imprint' specific tropisms, however, are not well defined. We show here that 1,25(OH)(2)D(3), the active form of vitamin D3, signaled T cells to express CC chemokine receptor 10, which enabled them to migrate to the skin-specific chemokine CCL27 secreted by keratinocytes of the epidermis. In contrast, 1,25(OH)(2)D(3) suppressed the gut-homing receptors alpha4beta7 and CCR9. Vitamin D3, the inactive prohormone naturally generated in the skin by exposure to the sun, was processed by dendritic cells and T cells to the active metabolite, providing a mechanism for the local regulation of T cell 'epidermotropism'. Our findings support a model in which dendritic cells process and 'interpret' locally produced metabolites to 'program' T cell homing and microenvironmental positioning.

Exogenous hydrogen sulfide induces functional inhibition and cell death of cytotoxic lymphocytes subsets

The toxic effects of exogenous hydrogen sulfide on peripheral blood lymphocytes have been investigated in detail. Hydrogen sulfide is now considered as a gasotransmitter with specific functional roles in different cell types, like neurons and vascular smooth muscle. Here we show that exogenous hydrogen sulfide induces a caspase-independent cell death of peripheral blood lymphocytes that depends on their intracellular glutathione levels, with a physiologically relevant subset specificity for CD8+ T cells and NK cells. Although lymphocyte activation does not modify their sensitivity to HS-, after 24 h exposure to hydrogen sulfide surviving lymphocyte subsets show a dramatically decreased proliferation in response to mitogens and a reduced IL-2 production. Overall, our data demonstrate that HS- reduces the cellular cytotoxic response of peripheral blood lymphocytes as well as their production of IL-2, therefore de-activating the major players of local inflammatory responses, adding new basic knowledge to the clinically well known anti-inflammatory effects of sulfur compounds.

Psoriasis: genetic associations and immune system changes

Psoriasis is a common inflammatory skin disease characterized by infiltration of inflammatory cells into the epidermis and altered keratinocyte differentiation. Psoriasis is currently thought of as a T-cell mediated 'Type-1' autoimmune disease. Gene expression changes in psoriasis lesions have been well documented, and strongly support an important role for tumor necrosis factor and interferon gamma signal pathways in its pathogenesis. The strongest genetic determinant of psoriasis identified to date lies within the class I region of the multiple histocompatibility locus antigen cluster, although its low penetrance implicates a requirement for other genetic risk factors. Multiple genome-wide linkage and an increasing number of association studies have been carried out, leading to multiple linkage peaks, and the identification of potential low risk variants. A number of these variants lie within genes encoding components of the immune system. However, the functional relationships between predisposing genetic variation is unclear, and presumably involves genetic susceptibility factors affecting both immune cell activation and keratinocyte differentiation. The interaction of environmental trigger factors with genetic effects is also not understood, but provide further evidence for the complex basis of this disease.

A retrospective search for predictors of clinical response to selective granulocyte and monocyte apheresis in patients with ulcerative colitis

Recently, selective granulocytapheresis (Adacolumn) has appeared as a new treatment for patients with inflammatory bowel disease. This study sought to determine predictors of response to this new nonpharmacologic mode of therapy by retrospectively evaluating 28 patients who received granulocytapheresis after experiencing active ulcerative colitis (UC). Between April 2000 and March 2004, 28 consecutive patients received granulocytapheresis for active UC with the Adacolumn, which is filled with cellulose acetate beads as the column leukocytapheresis carriers; the carriers adsorb granulocytes, monocytes/macrophages, and a small fraction of lymphocytes (FcgammaR and complement receptors bearing leukocytes). Each patient could receive up to 10 Adacolumn sessions, at 2 sessions per week. In 2004, clinical response was retrospectively evaluated. Seven days after the last Adacolumn session, 20 of 28 patients had remission (colitis activity index [CAI] < or =4) including all 8 patients who had their first UC episode. The mean duration of UC in the 8 first episode cases was 3.4 months compared with 40.2 months for all 28 patients and 65.4 months for the 8 nonresponders. The response to Adacolumn was independent of basal CAI. The 8 nonresponders were given conventional medication (CM) or cyclosporine (CsA) if the former failed. Two responded to CM, 3 to CsA, and 3 underwent colectomy. First UC episode and short disease duration appear good predictors of response to granulocytapheresis. Selective granulocytapheresis might be an effective first-line treatment.

Emerging drugs for psoriasis

Psoriasis is a chronic immune-mediated inflammatory skin disease characterised by abnormal keratinocyte differentiation and proliferation. The immunopathogenesis is complex and novel evidence shows the involvement of both innate and adaptive immune response. Type 1 T cells and their effector cytokines play a pivotal role. Several drugs under preclinical and clinical development for psoriasis are directed against the immune response, targeting activation or proliferation of T cells, their trafficking and skin-homing, or effector cytokines. Among these, great attention has been given to TNF-alpha, following the demonstration of effectiveness of anti-TNF-alpha biologicals, and to IFN-gamma inducers. Another appealing approach concerns drugs capable of inducing immunological tolerance. Progress made in the recognition of intracellular events has prompted the development of small molecules and oligonucleotides that can inhibit specific molecular targets. There is, however, a plethora of other emerging drugs, clearly suggestive of the current interest for psoriasis, which are briefly described in this paper.

Chemokine receptor expression in cutaneous T cell and NK/T-cell lymphomas: immunohistochemical staining and in vitro chemotactic assay

Interactions between chemokines and chemokine receptors are involved in migration and invasion of lymphoma cells. We investigated expression profiles of CXCR3 and CCR4 by immunohistochemistry and flow cytometry, and their biologic behaviors by real-time horizontal chemotaxis assay in cutaneous T cell and NK/T-cell lymphomas (TCLs). Tumor cells in mycosis fungoides (MF) constantly expressed CXCR3 at the patch stage, and expressed CCR4 at the tumor stage and in the folliculotropic variant of MF. Neoplastic cells at the plaque stage expressed CXCR3 and/or CCR4. Sezary cells in the dermis and circulation were positive for CCR4. Epidermotropic atypical cells in pagetoid reticulosis expressed CXCR3. CD30 cells exclusively expressed CCR4 in anaplastic large-cell lymphoma, and CXCR3 and/or CCR4 in lymphomatoid papulosis. In CD8TCL and extranodal NK/TCL characterized by extensive epidermotropism, tumor cells were positive for CXCR3. These data demonstrated preferential expression of CXCR3 in epidermotropic tumor cells, and of CCR4 in dermis-based lymphomas. In chemotaxis assays, CCR4 tumor cells in MF and CXCR3 tumor cells in CD8TCL migrated to thymus and activation-regulated chemokine and inducible protein-10, respectively. Therefore, spatial and temporal interactions between chemokine receptors and their ligands seem to dictate recruitment and retention of lymphoma cells in the skin.

Lymphocyte trafficking to inflamed skin--molecular mechanisms and implications for therapeutic target molecules

Tissue-selective recruitment of lymphocytes to peripheral organs, such as the skin, is crucial for spatial compartmentalisation within the immune system as well as immune surveillance under normal conditions. In addition, this process plays a key role for the pathogenesis of various diseases including common inflammatory disorders such as atopic dermatitis or psoriasis, but also malignancies such as cutaneous T cell lymphomas. Recruitment of lymphocytes to the skin is a highly complex process that involves adhesion to the endothelial lining, extravasation, migration through the connective tissue, and, finally, localisation of a subpopulation of lymphocytes to the epithelial compartment, the epidermis. An intertwined network of constitutively expressed and inducible cytokines, chemokines and other mediators provides guidance for lymphocyte migration, and a large number of adhesion receptors mediate sequential steps of cell-cell- and cell-substrate-interactions resulting in tissue-specific localisation of immune cells. Selectively targeting the functions of one or several key molecules involved in this complex cascade promises exciting new therapeutic options for treating inflammatory disorders, but at the same time, bears considerable imponderables which will be discussed in this article.

IL-31: a new link between T cells and pruritus in atopic skin inflammation

BACKGROUND

IL-31 is a novel T-cell-derived cytokine that induces severe pruritus and dermatitis in transgenic mice, and signals through a heterodimeric receptor composed of IL-31 receptor A and oncostatin M receptor.

OBJECTIVE

To investigate the role of human IL-31 in pruritic and nonpruritic inflammatory skin diseases.

METHODS

The expression of IL-31 was analyzed by quantitative real-time PCR in skin samples of healthy individuals and patients with chronic inflammatory skin diseases. Moreover, IL-31 expression was analyzed in nonlesional skin of atopic dermatitis patients after allergen or superantigen exposure, as well as in stimulated leukocytes. The tissue distribution of the IL-31 receptor heterodimer was investigated by DNA microarray analysis.

RESULTS

IL-31 was significantly overexpressed in pruritic atopic compared with nonpruritic psoriatic skin inflammation. Highest IL-31 levels were detected in prurigo nodularis, one of the most pruritic forms of chronic skin inflammation. In vivo, staphylococcal superantigen rapidly induced IL-31 expression in atopic individuals. In vitro, staphylococcal enterotoxin B but not viruses or T(H)1 and T(H)2 cytokines induced IL-31 in leukocytes. In patients with atopic dermatitis, activated leukocytes expressed significantly higher IL-31 levels compared with control subjects. IL-31 receptor A showed most abundant expression in dorsal root ganglia representing the site where the cell bodies of cutaneous sensory neurons reside.

CONCLUSION

Our findings provide a new link among staphylococcal colonization, subsequent T-cell recruitment/activation, and pruritus induction in patients with atopic dermatitis. Taken together, these findings show that IL-31 may represent a novel target for antipruritic drug development.

Granulocytapheresis in patients with refractory ocular Behcet's disease

Intraocular inflammation (uveoretinitis) is one major complication of Behcet's disease (BD) and responds poorly to drug therapy. This open prospective study was to assess the efficacy of selective granulocytapheresis in patients with refractory uveoretinitis of BD. Fourteen patients aged 20-56 years were treated. Granulocytapheresis was done with an Adacolumn filled with cellulose acetate leucocyte carries or beads that adsorb granulocytes and monocytes from the blood in the column. Each patient received 5 Adacolumn sessions at one session/week over 5 consecutive weeks. The study was designed to allow each patient to serve as his or her own control. The total numbers of ocular attacks (OA) were monitored for 6 months before and after 5 Adacolumn sessions. The number of OA (mean +/- SD) per patient for the 6 months before Adacolumn was 4.21 +/- 1.6 and for the 6 months post Adacolumn was 2.93 +/- 1.39 ( P = 0.0275). Nine patients (64%) improved and 5 did not change or worsened. Further, for a sub-group (n = 7) with duration of BD > or =5 years, the number of OA were 4.71 +/- 1.89 for the first 6 months and 2.29 +/- 1.38 for the second 6 months ( P = 0.0054). The corresponding values for a sub-group (n = 7) with duration of BD<5 years were 3.71 +/- 1.25 and 3.57 +/- 1.13, indicating that patients with long duration of BD are better responders. We conclude that granulocytapheresis might be effective and safe for patients with refractory ocular BD. Further studies are necessary to fully evaluate the clinical efficacy of granulocytapheresis for BD.

Adacolumn for selective leukocytapheresis as a non-pharmacological treatment for patients with disorders of the immune system: an adjunct or an alternative to drug therapy?

Inflammatory and/or autoimmune diseases like ulcerative colitis (UC) or Crohn's disease (CD) are debilitating chronic disorders that poorly respond to pharmacological interventions. Further, drug therapy has adverse effects that add to disease complications. The current thinking is that disorders like inflammatory bowel disease (IBD) reflect an over exuberant immune activation driven by cytokines including TNF-alpha. Major sources of cytokines include myeloid leukocytes (granulocytes, monocytes/macrophages), which in IBD are elevated with activation behavior and are found in vast numbers within the inflamed intestinal mucosa. Accordingly, myeloid cells should be the targets of therapy. Adacolumn is filled with cellulose acetate beads that selectively adsorb and deplete myeloid cells and a small fraction of lymphocytes (FcgammaR and complement receptors bearing cells). In one study, 20 steroid naive patients with moderate (n = 14) or severe (n = 6) UC according to Rachmilewitz despite 1.5-2.25 g/day of 5-aminosalicylic acid received 6 to 10 Adacolumn sessions at 2 sessions/week. Efficacy was assessed 1 week after the last session. The majority of patients responded to 6 sessions, 17 (85%) achieved remission. In 2 of the 3 non-responders, CAI was 8 and 12 in 1; all 3 had deep colonic ulcers at study initiation. Decreases were seen in total leukocytes (P = 0.003), % neutrophils (P = 0.003), % monocytes (P = 0.004), an increase in lymphocytes (P = 0.001), decreases in C-reactive protein (P = 0.0002), and rises in blood levels of soluble TNF-alpha receptors I (P = 0.0007), II (P = 0.0045). In a separate study, a case with very severe steroid refractory UC who received up to 11 sessions responded well and avoided colectomy. Further, myeloid cell purging with Adacolumn has been associated with the release of IL-1 receptor antagonist, suppression of TNF-alpha, IL-1beta, IL-6, IL-8, down-modulation of L-selectin and the chemokine receptor CXCR3. In conclusion, selective depletion of myeloid cells appears to induce anti-inflammatory effects and represents a non-pharmacological treatment for patients with active IBD. The treatment has a clear drug-sparing role. Changes in blood levels of inflammatory and anti-inflammatory factors are thought to contribute to the efficacy of this procedure.

Critical role of the fifth domain of E-cadherin for heterophilic adhesion with alpha E beta 7, but not for homophilic adhesion

The integrin alpha(E)beta(7) is expressed on intestinal intraepithelial T lymphocytes and CD8(+) T lymphocytes in inflammatory lesions near epithelial cells. Adhesion between alpha(E)beta(7)(+) T and epithelial cells is mediated by the adhesive interaction of alpha(E)beta(7) and E-cadherin; this interaction plays a key role in the damage of target epithelia. To explore the structure-function relationship of the heterophilic adhesive interaction between E-cadherin and alpha(E)beta(7), we performed cell aggregation assays using L cells transfected with an extracellular domain-deletion mutant of E-cadherin. In homophilic adhesion assays, L cells transfected with wild-type or a domain 5-deficient mutant formed aggregates, whereas transfectants with domain 1-, 2-, 3-, or 4-deficient mutants did not. These results indicate that not only domain 1, but domains 2, 3, and 4 are involved in homophilic adhesion. When alpha(E)beta(7)(+) K562 cells were incubated with L cells expressing the wild type, 23% of the resulting cell aggregates consisted of alpha(E)beta(7)(+) K562 cells. In contrast, the binding of alpha(E)beta(7)(+) K562 cells to L cells expressing a domain 5-deficient mutant was significantly decreased, with alpha(E)beta(7)(+) K562 cells accounting for only 4% of the cell aggregates, while homophilic adhesion was completely preserved. These results suggest that domain 5 is involved in heterophilic adhesion with alpha(E)beta(7), but not in homophilic adhesion, leading to the hypothesis that the fifth domain of E-cadherin may play a critical role in the regulation of heterophilic adhesion to alpha(E)beta(7) and may be a potential target for treatments altering the adhesion of alpha(E)beta(7)(+) T cells to epithelial cells in inflammatory epithelial diseases.

Cutaneous lymphocyte antigen expression on activated lymphocytes and its association with IL-12R (beta1 and beta2), IL-2Ralpha, and CXCR3

The majority of T lymphocytes that infiltrate psoriatic lesions express cutaneous lymphocyte antigen (CLA), a skin homing receptor involved in the influx of memory T cells to cutaneous sites. We investigated CLA expression on normal human peripheral blood mononuclear cells (PBMCs) and evaluated its association with IL-12 receptors, chemokine receptor, CXCR3, and IL-2Ralpha. PBMCs were stimulated in vitro with or without polyclonal activators (mitogen, or superantigens, or anti-CD3+anti-CD28) in the presence or absence of exogenous rhIL-12. The percentage of CLA+ T lymphocytes increased significantly after superantigen stimulation compared to anti-CD3+anti-CD28 or mitogen activation. The majority of activation induced CLA+ T lymphocytes co-expressed IL-12Rbeta1, IL-12Rbeta2, CXCR3, and CD25 in the presence of rhIL-12. Our results indicate that CLA expression on activated T lymphocytes is IL-12 and activation dependent and correlates with the expression of IL-12 receptors, IL-2Ralpha, and CXCR3. Monitoring the levels of Th1 differentiation markers such as CXCR3 and IL-12Rbeta2 along with activation marker, CD25 on skin homing CLA+ T lymphocytes may provide insight into the mechanism of action of immunotherapies directed against Th1 type skin inflammatory diseases.

Getting under the skin: the immunogenetics of psoriasis

Psoriasis is a chronic inflammatory disorder of the skin that is mediated by T cells, dendritic cells and inflammatory cytokines. We now understand many of the cellular alterations that underlie this disease, and genomic approaches have recently been used to assess the alterations of gene expression in psoriatic skin lesions. Genetic susceptibility factors that contribute to predisposition to psoriasis are now also being identified. It is hoped that we will soon be able to correlate the cellular pathogenesis that occurs in psoriasis with these genetic factors. In this Review article, we describe what is known about genes that confer increased susceptibility to psoriasis, and we integrate this with what is known about the molecular and cellular mechanisms that occur in other inflammatory and autoimmune disorders.

Emerging drugs in psoriasis

Psoriasis is a relatively common, chronic skin disease affecting 1-2% of the population in the developed countries. It is an inflammatory, autoimmune skin disorder characterised by an accelerated rate of epidermal proliferation and disordered differentiation. Since our last review in 1999, considerable progress has been made in understanding the immunopathogenesis of this disease, and new drugs have become available for its treatment. Recent clinical trials showed the efficacy of novel biotechnology approaches, such as blocking tumour necrosis factor-alpha or T-cell-mediated immune response by the anti-CD2, anti-CD11a, anti-B7, anti-CD4 or anti-CD25 approaches. Agents which block type 1 cytokines or skew immune reactions into type 2 are other promising approaches. Other possible targets are chemokines and their receptors, the cytokines and receptors involved in T cell trafficking into the skin, and peroxisome proliferator-activated receptors. Relatively little development is reported of the drugs targeting the keratinocyte or the classical antipsoriatic compounds which include glucocorticoids, vitamin D derivatives and cytostatic agents.

CXCR3 is required for migration to dermal inflammation by normal andin vivo activated T cells: differential requirements by CD4 and CD8 memory subsets

Lymphocytes in inflamed tissues express numerous chemokine receptors. The relative importance of these receptors for migration in inflammation is unclear. The role of CXCR3 in T cell subset migration was examined using monoclonal antibodies developed to rat CXCR3. CXCR3 was expressed on sixfold more CD8(+) ( approximately 30%) than CD4(+) ( approximately 5%) T cells in spleen, lymph nodes and blood, and on approximately 10% of CD4(+)CD45RC(-) (memory) and approximately 50% of CD8(+)CD45RC(+) spleen T cells. After immunization, CXCR3 increased tenfold on CD4(+) lymph node lymphoblasts ( approximately 55%), and >90% of inflammatory exudate T cells were CXCR3(+). CXCR3(+) T cells migrated significantly better than CXCR3(-) T cells to all dermal inflammatory stimuli tested in vivo, even though these T cells are a minority of the memory T cells. Blocking CXCR3 inhibited recruitment of 60-85% of unstimulated T cells and up to 90% of CD8(+)CD45RC(+) effector T cells, but caused <50% inhibition of CD4(+) and CD8(+) memory (CD45RC(-)) T cells. About 90% of T lymphoblast migration to IFN-gamma, IFN-gamma plus TNF-alpha, polyinosinic polycytidylic acid, lipopolysaccharide, and delayed-type hypersensitivity (DTH)-induced inflammation was inhibited. Blockade also reduced DTH-induced induration. Thus, CXCR3 has a non-redundant role in T cell migration to dermal inflammation and is critical for activated T lymphoblast recruitment, but memory T cells are less dependent on CXCR3 for their infiltration.

Homing receptor and chemokine receptor on intraepidermal T cells in psoriasis vulgaris

Intraepidermal T lymphocytes found in psoriatic skin lesions are involved in the development and maintenance of lesional pathology. It has become clear that differential expression of homing and chemokine receptors determines the specific migration of T cells to distinct tissues and microenvironments, including psoriasis lesions. The aim of the present study was to clarify expression of homing (CLA, VLA-4, and LFA-1) and chemokine (CCR4, CCR6, CCR7, and CXCR3) receptors on intraepidermal T cells in psoriatic lesions using flow cytometry. The vast majority of intraepidermal T cells in psoriatic lesions expressed CLA and LFA-1, whereas 58% of CD4+ and 85% of CD8+ T cells expressed VLA-4. The majority of CD4+ T cells and about half of the CD8+ T cells expressed CCR4 and CCR6, whereas less than one-third of CD4+ and CD8+ T cells expressed CXCR3 or CCR7. In patients with psoriasis the percentages of T cells expressing CLA, CCR4, and CCR6 were much higher in the epidermis of psoriatic plaques than in the peripheral blood. Thus, CLA, CCR4, and CCR6 may play a more important role in the migration of T cells to psoriatic epidermis.

Chemokine-receptor expression on T cells in lung compartments of challenged asthmatic patients

BACKGROUND

The interaction of chemokines with their receptors strongly influences the migration of leucocytes.

OBJECTIVE

In order to assess the contribution of these molecules to the local recruitment of T cells in bronchial asthma, we analysed the expression of 14 chemokine receptors on lung-derived T cells.

METHODS

Chemokine-receptor expression by T cells derived from the peripheral blood, the bronchoalveolar lavage fluid and the bronchial mucosa was analysed by flow cytometry and immunohistochemistry. Expression profiles in healthy and mildly asthmatic individuals were compared, the latter prior and after segmental allergen provocation.

RESULTS

Compared with peripheral blood, alveolar T cells expressed significantly more CCR2, CCR5, CCR6, CXCR3 and CCR4. However, no differences were observed between healthy controls and unchallenged asthmatics. In patients developing significant inflammatory responses following specific allergen challenge, a marked increase in the percentage of CCR4+ and CCR7+, and reduced numbers of CXCR3-bearing alveolar T cells were detected. Following specific allergen challenge, chemokine-receptor expression profiles of T cells from the alveolar space and the mucosa or the submucosa were similar, excluding a particular subcompartmentalization of the chemokine/chemokine-receptor system.

CONCLUSION

The expression of certain chemokine receptors by lung T cells suggests a contribution to the physiological recruitment of T cells to the lungs, both in healthy controls and unchallenged mild asthmatics. However, strong allergen-induced airway responses were associated with a specific chemokine-receptor profile, suggesting the involvement of certain chemokine receptors in the pathogenesis of allergic bronchial inflammation.

CXCR3-/- mice mount an efficient Th1 response but fail to control Leishmania major infection

Chemokines play a critical role in recruitment of leukocytes to the site of infection, which is essential for host defense. We analyzed the role of CXC chemokine receptor 3 (CXCR3) in the control of cutaneous leishmaniasis using CXCR3-/- C57BL/6 mice. We found that Leishmania major-infected CXCR3-/- mice mount an efficient Th1 response as evident by markedly increased serum levels of Th1-associated IgG2a and significant production of IFN-gamma and IL-12 by the draining lymph node cells, restrict systemic spread of infection, but fail to control parasite replication at the site of infection and develop chronic non-healing lesions. Furthermore, the inability of CXCR3-/- mice to control cutaneous L. major growth was associated with fewer CD4+ and CD8+ T cells and significantly lower levels of IFN-gamma in their lesions as compared to CXCR3+/+ mice. These results demonstrate that CXCR3 plays a critical role in the host defense against cutaneous leishmaniasis caused by L. major. Furthermore, they also suggest that the susceptibility of CXCR3-/- mice to L. major is due to impaired CD4+ and CD8+ T cell trafficking and decreased production of IFN-gamma at the site of infection rather than to their inability to mount a parasite-specific Th1 response.

Psoriasis pathophysiology: current concepts of pathogenesis

Psoriasis vulgaris is a common skin disorder characterised by focal formation of inflamed, raised plaques that constantly shed scales derived from excessive growth of skin epithelial cells. The disease is defined by a series of linked cellular changes in the skin: hyperplasia of epidermal keratinocytes, vascular hyperplasia and ectasia, and infiltration of T lymphocytes, neutrophils, and other types of leucocyte in affected skin. In a relatively short period, psoriasis vulgaris has been conceptualised as a T lymphocyte mediated autoimmune disease and new biological therapies that target T cells have just entered routine clinical practice. Similarly, rapid progress has been made towards dissecting cellular and molecular pathways of inflammation that contribute to disease pathogenesis. This short review presents current pathogenic concepts that have emerged from genetic, genomic, and cellular information obtained in basic studies and from clinical studies of selective immune targeting drugs.

Psoriasis induced by anti-tumor necrosis factor therapy: A paradoxical adverse reaction

Administration of anti-tumor necrosis factor (anti-TNF) agents is beneficial in a variety of chronic inflammatory conditions, including psoriasis. We describe 5 patients in whom psoriasiform skin lesions developed 6-9 months after the initiation of anti-TNF therapy for longstanding, seropositive rheumatoid arthritis (etanercept or adalimumab), typical ankylosing spondylitis (infliximab), and Adamantiades-Behçet's disease (infliximab). In all 5 patients, the underlying disease had responded well to anti-TNF therapy. Four patients developed a striking pustular eruption on the palms and/or soles accompanied by plaque-type psoriasis at other skin sites, while 1 patient developed thick erythematous scaly plaques localized to the scalp. In 3 patients there was nail involvement with onycholysis, yellow discoloration, and subungual keratosis. Histologic findings from skin biopsies were consistent with psoriasis. None of these patients had a personal or family history of psoriasis. In all patients, skin lesions subsided either with topical treatment alone, or after discontinuation of the responsible anti-TNF agent. The interpretation of this paradoxical side effect of anti-TNF therapy remains unclear but may relate to altered immunity induced by the inhibition of TNF activity in predisposed individuals.

Expression of rat I-TAC/CXCL11/SCYA11 during central nervous system inflammation: comparison with other CXCR3 ligands

The chemokines are a large gene superfamily with critical roles in development and immunity. The chemokine receptor CXCR3 appears to play a major role in the trafficking of activated Th1 lymphocytes. There are at least three major ligands for CXCR3: mig/CXCL9, IP-10/CXCL10 and I-TAC/CXCL11, and of these three ligands, CXCL11 is the least well-characterized. In this study, we have cloned a rat ortholog of CXCL11, evaluated its function, and examined its expression in the Th-1-mediated disease, experimental autoimmune encephalomyelitis (EAE) in the rat. Based on its predicted primary amino-acid sequence, rat I-TAC/CXCL11 was synthesized and shown to induce chemotaxis of activated rat T lymphocytes in vitro and the in vivo migration of T lymphocytes when injected into the skin. I-TAC/CXCL11 expression, as determined by RT-PCR, increased in lymph node and spinal cord tissue collected from rats in which EAE had been actively induced, and in spinal cord tissue from rats in which EAE had been passively induced. The kinetics of expression were similar to that of CXCR3 and IP-10/CXCL10, although expression of both CXCR3 and IP-10/CXCL10 was more intense than that of I-TAC/CXCL11 and increased more rapidly in both lymph nodes and the spinal cord. Only minor levels of expression of the related chemokine mig/CXCL9 were observed. Immunohistochemistry revealed that the major cellular source of I-TAC/CXCL11 in the central nervous system (CNS) during EAE is likely to be the astrocyte. Together, these data indicate that I-TAC/CXCL11 is expressed in the CNS during the clinical phase of EAE. However, the observation that I-TAC/CXCL11 is expressed after receptor expression is detected suggests that it is not essential for the initial migration of CXCR3-bearing cells into the CNS.

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 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.

Granulocyte adsorptive apheresis for leg ulcers complicated by rheumatoid arthritis: a report on three successfully treated cases

BACKGROUND

The treatment of inflammatory leg ulcers complicated by rheumatoid arthritis (RA), which are unresponsive to conventional care, can be frustrating. Furthermore, as granulocytes and monocytes (GM) are major sources of inflammatory cytokines, they have the potential to initiate and perpetuate inflammatory skin lesions. Accordingly, a recent study reported the remission of pyoderma gangrenosum following the reduction of activated peripheral blood GM by adsorptive apheresis (GMA).

METHODS

In this clinical study, we applied GMA to three cases, each with one leg ulcer below the knee and RA. The ulcers had not responded to conventional therapy, including disinfection, dressing, and antimicrobials, and therefore were thought to represent inflammatory vasculitic lesions. GMA was performed using a column with a capacity of 335 mL, filled with cellulose acetate beads that selectively adsorb granulocytes and monocytes/macrophages (Adacolumn). Each patient received one GMA session/week for five consecutive weeks. The duration of one session was 60 min, with a flow rate of 30 mL/min.

RESULTS

The ulcers began to recede after two GMA sessions and, by the end of the fifth session, the ulcers in all three patients had healed. No recurrence has been observed up to the time of this report. The treatment was well tolerated and no severe side-effects were observed.

CONCLUSIONS

GMA, which depletes activated neutrophils and monocytes/macrophages, appears to be effective for inflammatory skin ulcers which do not respond to conventional medications.

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.

TH1 and TH2 lymphocyte development and regulation of TH cell-mediated immune responses of the skin

Since the first description of the subpopulations of TH1 and TH2 cells, insights into the development and control of these cells as two polarized and physiologically balanced subsets have been generated. In particular, implications of the TH1-TH2 concept for TH cell-mediated skin disorders have been discovered. This article will review the basic factors that control the development of TH1 and TH2 cells, such as the cytokines IL-12 and IL-4 and transcription factors, the possible role of costimulatory molecules, and specialized dendritic cell populations. These regulatory mechanisms will be discussed in the context of polarized TH1 or TH2 skin disorders such as psoriasis and atopic dermatitis. Also presented are the principles that govern how chemokines and chemokine receptors recruit TH1 and TH2 cells to inflammatory sites and how they amplify these polarized TH cell responses. All of these concepts, including a novel role for IL-4-inducing TH1 responses, can contribute to the design of better therapeutic strategies to modulate TH cell-mediated immune responses.

Differential effects of interleukin 12 and interleukin 10 on superantigen-induced expression of cutaneous lymphocyte-associated antigen (CLA) and αEβ7 integrin (CD103) by CD8+ T cells

At both cutaneous and mucosal sites, interleukin (IL)-10, IL-12 and transforming growth factor (TGF)-beta are important regulators of chronic inflammatory disease, where cutaneous lymphocyte-associated antigen (CLA) and alphaE integrin (CD103) may be expressed. Stimulation with streptococcal pyrogenic exotoxin C (SpeC) increased the expression of CD103 by CD8+ but not CD4+ T cells. While adding IL-12 augmented the expression of CLA, superantigen-induced expression of CD103 was markedly suppressed by IL-12, which could be reversed by TGF-beta. Antibodies against TGF-beta inhibited, and a combination of anti-TGF-beta and IL-12 completely abrogated the induced CD103 expression. IL-10 strongly decreased the frequency of CLA+ and although not increasing the frequency of CD103+CD8+ T cells, the amount of CD103 expressed per cell was markedly increased. Thus, the expression of CLA and CD103 may be antagonistically regulated by IL-10 and IL-12 and the balance between these cytokines could influence the T cell migration of inflammatory cells into epithelial tissues.

Psoriasis genomics: analysis of proinflammatory (type 1) gene expression in large plaque (Western) and small plaque (Asian) psoriasis vulgaris

BACKGROUND

Type 1 T cells are hypothesized to be central in the immunopathogenesis of psoriasis. Through elaboration of interferon (IFN)-gamma, type 1 T cells regulate the expression of many 'downstream' inflammatory genes, including an array of chemokines that regulate leucocyte trafficking and activation in skin lesions. Accordingly, disease progression and/or severity might be controlled by the degree to which differing cytokines and chemokines are overexpressed in focal skin regions. To examine this possibility, we studied two forms of chronic psoriasis vulgaris that differ significantly in overall severity and progression: small plaque (SP) psoriasis occurring in Korean patients, and large plaque (LP) psoriasis occurring in North American patients.

OBJECTIVES

To characterize LP and SP psoriasis vulgaris with respect to expression of proinflammatory genes that define the type 1 T-cell axis in skin lesions [genes encoding interleukin (IL)-12, IFN-gamma, and IFN-gamma-regulated chemokines or inflammatory mediators].

METHODS

Total cellular RNA of skin samples from groups of patients with LP or SP psoriasis was analysed by quantitative reverse transcription-polymerase chain reaction (TaqMan analysis) to compare the differences in mRNA expression of genes related to the IFN-gamma pathway.

RESULTS

The mRNA expression of keratin 16, CD25, IFN-gamma, IL-12 p40, signal transducer and activator of transcription-1, inducible nitric oxide synthase, IL-8, macrophage inflammatory protein-3alpha, monocyte chemoattractant protein-1, S100A12, IFN-gamma-inducible protein of 10 kDa, IFN-inducible T-cell alpha-chemoattractant and monokine induced by IFN-gamma was increased in the lesions of both LP psoriasis and SP psoriasis. However, IL-18 mRNA expression was significantly different in the lesions of LP psoriasis in comparison with those of SP psoriasis.

CONCLUSIONS

The results indicate that proinflammatory type 1 genes regulated by IFN-gamma are similarly increased in both SP and LP psoriasis, but a potential difference in IL-18 exists between these disease forms. The consistent activation of this set of genes argues for a central role of IFN-gamma as a molecular regulator of inflammation in these distinct subtypes of psoriasis vulgaris. In contrast, disease extent/severity must be controlled by yet other factors.

In vivo modulation of leukocyte trafficking receptor following therapeutic purging of myeloid cells: implications for treatment of HIV infection and other immune disorders

Therapeutic purging of myeloid cells (monocytes and granulocytes) (MYP) has been proposed as a treatment of severe inflammatory conditions like ulcerative colitis and rheumatoid arthritis. Although direct purging of inflammatory cells contributes to its efficacy, the precise mechanism of action is still unclear. We have tested MYP in a pilot study on 12 patients with chronic HIV infection, of whom 6 underwent MYP. Three/6 MYP patients and none of the controls displayed a strong and long-lasting decrease of cells expressing CXCR3, a major chemokine receptor responsible for trafficking of inflammatory cells. In these three patients, the number of circulating CD4 T cells increased during treatment. The data provide a rational for the use of MYP as a therapeutic tool acting via the modulation of immune cell trafficking.

Chemokine receptor expression on neoplastic and reactive T cells in the skin at different stages of mycosis fungoides

We analyzed the expression of 13 chemokine receptors in mycosis fungoides, in order to assess the contribution of chemotaxis to the pathogenesis of the disease. Material from skin biopsies of six patients with early disease and six patients at the tumor stage of mycosis fungoides was analyzed by immunohistochemistry and partly also by flow cytometry. The receptors CCR1, CCR2, CCR3, CCR5, CCR6, CXCR1, CXCR2, CXCR5, and CX3CR1 were rarely and inconsistently detected in lesional skin and thus their participation in mycosis fungoides could largely be ruled out. In contrast, CCR4, CXCR3, and CXCR4 were substantially expressed on both mycosis fungoides cells and the surrounding reactive T cells in the early patch and plaque stages of the disease, indicating an involvement of these chemokine receptors in the disease process. In the tumor stage of mycosis fungoides, we interestingly observed a loss of a relevant chemokine receptor in four out of six patients. In three patients CXCR3 and in one patient CCR4 was absent on tumor mycosis fungoides cells, whereas the reactive T cells showed normal levels of expression. Within these samples, tumor mycosis fungoides cells exhibited high levels of CCR7, a chemokine receptor central for the entry of T cells to lymphatic tissue. Taken together, our data suggest that the loss of one or more of the chemokine receptors involved in the homing of the mycosis fungoides cells to the skin may trigger the latent potential of these cells to metastasize into regional lymphatic tissue.

The molecular basis of lymphocyte recruitment to the skin: clues for pathogenesis and selective therapies of inflammatory disorders

Spatial compartmentalization and tissue-selective localization of T lymphocytes to the skin are crucial for immune surveillance and the pathogenesis of various disorders including common inflammatory diseases such as atopic dermatitis or psoriasis, but also malignancies such as cutaneous T cell lymphomas. Cutaneous recruitment of lymphocytes is a highly complex process that involves extravasation, migration through the dermal connective tissue, and eventually, localization to the epidermis. An intertwined network of cytokines and chemokines provides the road signs for leukocyte migration, while various adhesion receptors orchestrate the dynamic events of cell-cell and cell-substrate interactions resulting in cutaneous localization of T cells. Selectively targeting the functions of molecules involved in this interplay promises exciting new therapeutic options for treating inflammatory skin disorders.

Chemokines and inflammatory skin diseases

Accumulating evidence indicates that chronically relapsing inflammatory skin diseases such as atopic dermatitis and psoriasis are T cell-mediated diseases. Thus, understanding the underlying mechanisms of memory T-cell homing to the skin may provide promising targets for the development of novel therapeutics to interfere with inflammatory processes of the skin. Chemokines, a superfamily of small cytokine-like, chemotactic proteins, have recently been shown to critically regulate leukocyte trafficking. Here we summarize results of recent studies associating chemokines with a psoriatic or atopic dermatitis phenotype and delineating their role in the recruitment of memory T cells to the skin.

The T-lymphocyte chemoattractant Mig is highly expressed in vernal keratoconjunctivitis

PURPOSE

To examine the expression of the three interferon-gamma-inducible CXCR3-binding chemokines, CXCL10/IP-10 (interferon-gamma-inducible protein of 10 KDa), CXCL9/Mig (monokine induced by interferon-gamma), and CXCL11/I-TAC (interferon-inducible T-cell alpha chemoattractant) in the conjunctiva of patients with vernal keratoconjunctivitis (VKC). These chemokines exhibit potent T-lymphocyte chemoattractant activity.

DESIGN

Immunohistochemical study.

METHODS

Conjunctival biopsy specimens from 16 patients with active VKC and nine control subjects were studied by immunohistochemical techniques using monoclonal antibodies directed against IP-10, Mig, and I-TAC. The phenotype of inflammatory cells expressing chemokines was examined by double immunohistochemistry.

RESULTS

In the normal conjunctiva, very weak Mig immunoreactivity was observed on basal epithelial cells and on vascular endothelial cells in the upper substantia propria. There was no immunoreactivity for the other chemokines. In all VKC specimens, strong immunoreactivity for Mig was expressed by epithelial cells, vascular endothelial cells, and inflammatory mononuclear cells. Inflammatory mononuclear cells expressing IP-10 and I-TAC were noted in 10 and nine specimens, respectively. The numbers of Mig(+) inflammatory cells were significantly higher than the numbers of IP-10(+) and I-TAC(+) inflammatory cells (P <.001). Inflammatory cells expressing Mig were CD4(+) T-helper/inducer cells (71.6 +/- 3.2%), CD8(+) T-cytotoxic/suppressor cells (19.5 +/- 1.5%), and CD68(+) monocytes/macrophages (5.3 +/- 5%). All inflammatory cells expressing IP-10 and I-TAC were CD68(+) monocytes/macrophages.

CONCLUSIONS

The CXC chemokine Mig is selectively and highly expressed in VKC suggesting a pathogenic role of the chemokine receptor CXCR3 and the ligand Mig in the recruitment of activated T lymphocytes.

The immunology of psoriasis and biologic immunotherapy

In this review, we will discuss the immunological basis for psoriasis with special emphasis on the role of effector T cells. With the understanding of this immunologic process, we will present a model for the development of targeted immune response modifiers, termed biologic immunotherapies, and their potential role for the benefit of patients with psoriasis.

The inhibitory effect of VitD3 on proliferation of keratinocyte cell line HACAT is mediated by down-regulation of CXCR2 expression

Psoriasis is a disease characterized by inflammation and increased population of hyperproliferative keratinocytes. It is well known that chemokines and chemokine receptors, such as interleukin-8 and its receptors (CXCR1 and CXCR2), play important roles in the pathogenesis of psoriasis. So far, examination of CXCR2 expression in psoriatic lesional keratinocytes by FACS calibur has not been reported and whether VitD3 inhibits psoriatic lesional keratinocyte proliferation through down-regulation of CXCR2 expression has not been elucidated. In the present study, CXCR2 expression in psoriatic lesional keratinocytes and HACAT treated with VitD3 was detected by flow cytometry. The proliferative capacity of HACAT treated with VitD3 was assayed by MTT assay. The results showed that CXCR2 expression in psoriatic lesional keratinocytes was higher than that in normal human keratinocytes. At the correct concentration VitD3 could inhibit human keratinocyte proliferation and down-regulate CXCR2 expression in HACAT. The data demonstrate that the inhibitory effect of VitD3 on keratinocyte proliferation might be mediated by down-regulation of CXCR2 expression.

Infiltrating CD8+ T cells in oral lichen planus predominantly express CCR5 and CXCR3 and carry respective chemokine ligands RANTES/CCL5 and IP-10/CXCL10 in their cytolytic granules: a potential self-recruiting mechanism

Lichen planus is a chronic inflammatory disease of the skin and oral mucosa in which the cell-mediated cytotoxicity is regarded as a major mechanism of pathogenesis. To understand its pathophysiology further, the present study examined the in situ expression of chemokines and chemokine receptors in oral lichen planus. Immunohistochemical analysis of 15 cases has consistently revealed that infiltrating CD4(+) and CD8(+) T cells in the submucosa predominantly expressed CCR5 and CXCR3. Furthermore, infiltrating T cells, particularly CD8(+) T cells, were positive for RANTES/CCL5 and IP-10/CXCL10, the ligands of CCR5 and CXCR3, respectively. By immunoelectron microscopy, these chemokines were localized in the cytolytic granules of CD8(+) T cells. Lesional keratinocytes also overexpressed the ligands of CXCR3, namely, MIG/CXCL9, CXCL10, and I-TAC/CXCL11. Our data suggest that the chemokines signaling via CCR5 and CXCR3, which are known to be selectively expressed by type 1 T cells, are predominantly involved in T-cell infiltration of oral lichen planus. Furthermore, the presence of CCL5 and CXCL10 in the cytolytic granules of tissue-infiltrating CD8(+) T cells expressing CCR5 and CXCR3 reveals a potential self-recruiting mechanism involving activated effector cytotoxic T cells.

Normal keratinocytes express Toll-like receptors (TLRs) 1, 2 and 5: modulation of TLR expression in chronic plaque psoriasis

BACKGROUND

Toll-like receptors (TLRs) are part of the innate immune system involved in the response to microbial pathogens. TLR2 recognizes various ligands expressed by Gram-positive bacteria, while TLR3, TLR4 and TLR5 are specific for double-stranded RNA, Gram-negative lipopolysaccharides and bacterial flagellin, respectively.

OBJECTIVES

To determine, firstly, whether epidermal keratinocytes of normal skin express TLRs and, secondly, whether modulation of TLR expression occurs in psoriasis, an inflammatory skin disease associated with certain microorganisms such as streptococci, staphylococci and yeasts.

METHODS

Eight samples of normal, and 15 samples of lesional and nonlesional psoriatic skin were stained with polyclonal antibodies specific for TLR1-5 using an avidin-biotin-peroxidase technique.

RESULTS

Epidermal keratinocytes in normal skin constitutively expressed TLR1, TLR2 and TLR5, while TLR3 and TLR4 were, in most cases, barely detectable. Cytoplasmic TLR1 and TLR2 were expressed throughout the epidermis, with higher staining of the latter on basal keratinocytes, while TLR5 expression was concentrated in the basal layer. In contrast, in lesional epidermis from patients with psoriasis, TLR2 was more highly expressed on the keratinocytes of the upper epidermis than on the basal layer, while TLR5 was downregulated in basal keratinocytes compared with corresponding nonlesional psoriatic epidermis. In addition, nuclear TLR1 staining was observed in the upper layers of both nonlesional and lesional psoriatic epidermis, but not in that of normal skin.

CONCLUSIONS

These findings suggest that TLRs expressed by epidermal keratinocytes constitute part of the innate immune system of the skin. The relevance of altered keratinocyte TLR expression in psoriasis remains to be determined.

Both IL-4 and IL-13 inhibit the TNF-alpha and IFN-gamma enhanced MDC production in a human keratinocyte cell line, HaCaT cells

BACKGROUND

Macrophage-derived chemokine (MDC) is a Th2 type chemokine and its receptor CC chemokine receptor 4 (CCR4) is preferentially expressed on Th2 cells. Recent reports demonstrated that MDC is expressed not only by macrophages, dendritic cells and lymphocytes, but also by cultured human keratinocytes (KCs). However, the regulation of MDC production in KCs by various cytokines has not been well documented.

OBJECTIVE

In this study, we investigated how Th1/Th2 cytokines regulate MDC production in a human KC cell line, HaCaT cells.

METHODS

HaCaT cells were cultured with or without various cytokines for 24 h and RT-PCR was performed using these cells to evaluate MDC mRNA levels. ELISA was carried out using supernatant of HaCaT cells to calculate secreted MDC protein levels.

RESULTS

MDC mRNA was weakly expressed in HaCaT cells, and upon stimulation with TNF-alpha or IFN-gamma, MDC expression was strongly upregulated. The supernatant MDC levels when stimulated with TNF-alpha or IFN-gamma were significantly higher than those without stimulation, and were synergistically increased when stimulated with a combination of TNF-alpha and IFN-gamma. Both interleukin-4 (IL-4) and IL-13 inhibited TNF-alpha and IFN-gamma enhanced MDC production in HaCaT cells in a dose-dependent manner.

CONCLUSION

Th2-type cytokines IL-4 and IL-13 downregulate the production of MDC, a Th2 type chemokine, by KCs. This may partially contribute to maintaining Th1/Th2 balance in inflammatory skin diseases like atopic dermatitis.