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Background Thymic stromal lymphopoietin (TSLP) is a cytokine with pleiotropic functions in the immune system. It has been associated with allergic reactions in the skin and lungs but also homeostatic tolerogenic responses in the thymus and gut. Objective In human subjects TSLP is present in 2 isoforms, short and long. Here we wanted to investigate the differential expression of the TSLP isoforms and discern their biological implications under homeostatic or inflammatory conditions. Methods We evaluated the expression of TSLPs in tissues from healthy subjects, patients with ulcerative colitis, patients with celiac disease, and patients with atopic dermatitis and on epithelial cells and keratinocytes under steady-state conditions or after stimulation. We then tested the immune activity of TSLP isoforms both in vitro and in vivo . Results We showed that TSLP isoforms are responsible for 2 opposite immune functions. The short isoform is expressed under steady-state conditions and exerts anti-inflammatory activities by affecting the capacity of PBMCs and dendritic cells to produce inflammatory cytokines. Moreover, the short isoform TSLP ameliorates experimental colitis in mice and prevents endotoxin shock. The long isoform of TSLP is proinflammatory and is only expressed during inflammation. The isoforms are differentially regulated by pathogenic bacteria, such as Salmonella species and adhesive-invasive Escherichia coli . Conclusions We have solved the dilemma of TSLP being both homeostatic and inflammatory. The TSLP isoform ratio is altered during several inflammatory disorders, with strong implications in disease treatment and prevention. Indeed, targeting of the long isoform of TSLP at the C-terminal portion, which is common to both isoforms, might lead to unwanted side effects caused by neutralization of the homeostatic short isoform. [ABSTRACT FROM AUTHOR]

Background Thymic stromal lymphopoietin (TSLP) is a major proallergic cytokine that promotes TH2 responses through dendritic cell (DC) activation. Whether it also plays a role in human autoimmune inflammation and associated pathways is not known. Objective In this study we investigated the potential role of several epithelium-derived factors, including TSLP, in inducing IL-23 production by human DCs. We further dissected the role of TSLP in patients with psoriasis, an IL-23-associated skin autoimmune disease. Methods The study was performed in human subjects using primary cells and tissue samples from patients with psoriasis and healthy donors. We analyzed the production of IL-23 in vitro by blood and skin DCs. We studied the function for TSLP and its interaction with other components of the inflammatory microenvironment in situ and ex vivo. Results We found that TSLP synergized with CD40 ligand to promote DC activation and pathogenic IL-23 production by primary blood and skin DCs. In situ TSLP was strongly expressed by keratinocytes of untreated psoriatic lesions but not in normal skin. Moreover, we could demonstrate that IL-4, an important component of the TH2 inflammation seen in patients with atopic dermatitis, inhibited IL-23 production induced by TSLP and CD40 ligand in a signal transducer and activator of transcription 6-independent manner. Conclusion Our results identify TSLP as a novel player within the complex psoriasis cytokine network. Blocking TSLP in patients with psoriasis might contribute to decreasing DC activation and shutting down the production of pathogenic IL-23. [ABSTRACT FROM AUTHOR]

Abstract: Lupus erythematosus (LE) represents an autoimmune disease with great clinical variability in which photosensitivity is a common feature for all forms and subsets. The nature and characteristics of clinical photosensitivity in LE have been elucidated through standardized phototesting procedures. The development of skin lesions after UV-injury is typically delayed starting from a few days up to three weeks after the irradiation, and may persist for months. Therefore, patients may not be aware of the detrimental effects of sunlight for their disease. The most photosensitive subset of LE is LE tumidus, followed by subacute cutaneous LE. Phototesting has also been crucial for studying the pathophysiology of LE-photosensitivity. Abnormalities of generation and clearance of UV-triggered apoptotic cells in LE are an important source of autoantigens. Recent data demonstrate the linkage of innate with adoptive immune pathways in UV-induced autoimmune response. Plasmocytoid dendritic cells (PDC) and their secreted IFN-α play a central role in the LE-pathogenesis. The recruitment of relevant leukocyte subsets is dependant on certain chemokines, which have been characterized in recent studies. An amplification cycle has been postulated, in which UV induces apoptosis and necrosis resulting in the production and release of chemokines. Subsequently, effector memory T cells as well as PDCs are recruited and activated perpetuating an amplification process that leads to UV-induced cutaneous LE lesion. [Copyright &y& Elsevier]

Abstract: In recent years, our knowledge of the immunopathogenesis of chronic inflammatory skin diseases has increased significantly. Accumulating evidence indicates that the complex interaction of structural cells, in particular keratinocytes and endothelial cells, with skin-infiltrating leukocytes is key to our understanding of psoriasis. The recruitment of pathogenic leukocyte subsets into the skin represents a prerequisite for the initiation and maintenance of psoriasis vulgaris and is mediated by a complex chemokine and cytokine network. Results of recent studies associating cytokines and chemokines with a psoriatic phenotype are outlined herein, and their role as therapeutic targets in psoriasis is discussed in detail. [Copyright &y& Elsevier]

Background: As clinical and histological features of allergic and irritant contact dermatitis share common characteristics, the differentiation between them in the preclinical and clinical evaluations of chemicals remains difficult. Objective: To identify the differences in the underlying immunological mechanisms of chemical-induced allergic or irritant skin responses. Methods: We systematically studied the involvement of chemokines in both diseases by quantitative real-time polymerase chain reaction in mice and humans. The cellular origin of relevant chemokines and receptors was determined using immunohistochemistry; functional relevance was demonstrated in vitro by transwell chemotaxis and in vivo by adoptive transfer experiments using a model of hapten-induced murine contact hypersensitivity. Results: Independent of overall skin inflammation, chemical-induced allergic and irritant skin responses showed distinct molecular expression profiles. In particular, chemokine genes predominantly regulated by T-cell effector cytokines demonstrated differential upregulation in hapten-specific skin inflammation. Notably, the expression of CXCR3 ligands, such as CXCL9 (Mig) and CXCL10 (IP-10), was upregulated in chemical-induced allergic skin responses when compared with irritant skin responses. Furthermore, we showed that inflammatory chemokines such as CXCL10 prime leukocytes to respond to CXCL12 (SDF-1), increasing their recruitment both in vitro and in vivo. Conclusion: We provide important insights into the molecular basis of chemical-induced allergic and irritant contact dermatitis, identify novel markers suitable for their differentiation, and demonstrate the cooperation of inflammatory and homeostatic chemokines in the recruitment of pathogenic leukocyte subsets. Clinical implications: Molecular differences between both diseases represent the basis for new approaches to diagnostics and therapy. [Copyright &y& Elsevier]

Atopic dermatitis (AD) is a common pruritic and chronically relapsing inflammatory skin disease. The pathophysiology of AD includes disturbed skin barrier functions, frequent allergic responses against allergens, defects in the antimicrobial immune defense, and a genetic predisposition. In this review we summarize advances in our understanding of the complex interdependent network of members of the rapidly growing protein superfamilies of cytokines and chemokines that lead to the development of AD. [Copyright &y& Elsevier]

Atopic dermatitis (AD) lesions are characterized by differences in the activation state of endothelial cells and vascular smooth muscle cells and the release of inflammatory mediators by and toward the vasculature. The vascular system, including endothelial cells and smooth muscle cells, is ultimately involved in clinical symptoms of AD, such as erythema, edema, leukocyte recruitment, and white dermographism. Various mediators and bidirectional neurovascular interactions regulate the inflammatory response during AD. T cell–endothelial cell interactions are a crucial component to establish acute AD. Various immune cells, including monocytes and mast cells, communicate with the endothelium by releasing inflammatory mediators, thereby stimulating inflammatory mediator release from activated endothelial cells. The process of adhesion, tethering, and transmigration of infiltrating cells is a highly regulated and an active communication process between endothelial cells and leukocytes. Endothelial cells play a pivotal role in the pathophysiology of AD and represent future targets for the treatment of AD. [Copyright &y& Elsevier]

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 TH1 and TH2 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. [Copyright &y& Elsevier]

Abstract: For a long time, systemic lupus erythematosus (SLE) was considered a potentially deadly disease. Since the introduction of immunosuppressive therapy, the life expectancy and the quality of life of patients suffering from lupus erythematosus has been dramatically improved. Today, the 5-year survival rate for SLE varies between 50% and 95%. Still, not all patients benefit equally from medical advances. Ethnic and/or socioeconomic minorities show severely disadvantageous prognosis or outcome in various studies. A substantial reduction in the quality of life as well as unemployment are other frequent side effects of this disease. Vocational handicaps related to discoid lupus erythematodes (DLE) was seen in nearly 45% of the patients. Therefore, the management of lupus erythematosus patients requires interdisciplinary cooperation between physicians, psychologists and social workers. The major aim of this article is to summarize the history of lupus erythematosus on the one and the other hand to consider the role of the socioeconomic factors influencing the prognosis of systemic and cutaneous lupus erythematosus. [Copyright &y& Elsevier]

Background: Phototherapy has a profound immunosuppressive effect and is able to inhibit hypersensibility reactions in the skin. Objective: We evaluated whether phototherapy using a combination of UV-B (5%), UV-A (25%), and visible light (70%), referred to as mUV/VIS, is effective in treating allergic rhinitis. Methods: We conducted a randomized, double-blind study, in 49 patients with hay fever. The study was performed during the ragweed season. Each intranasal cavity was illuminated 3 times a week for 3 weeks with mUV/VIS or with low-intensity visible light. Symptom scores, inflammatory cells, and their mediators were assessed in nasal lavages. In vitro effects of mUV/VIS irradiation on T-cell and eosinophil apoptosis and its inhibitory effect on mediator release from basophils were examined. Results: Rhinophototherapy was tolerated well and resulted in a significant improvement of clinical symptoms for sneezing (P < .016), rhinorrhea (P < .007), nasal itching (P < .014), and total nasal score (P < .004). None of the scores improved significantly in the control group. Scores for nasal obstruction slightly improved after mUV/VIS treatment and significantly increased in the control group (P < .017). In the nasal lavage, phototherapy significantly reduced the number of eosinophils and the level of eosinophil cationic protein and IL-5. In vitro irradiation of T cells and eosinophils with mUV/VIS light dose-dependently induced apoptosis. Furthermore, mUV/VIS irradiation inhibited the mediator release from RBL-2H3 basophils. Conclusion: These results suggest that phototherapy is an effective modality to treat allergic rhinitis and offer new options for the treatment of immune-mediated mucosal diseases. [ABSTRACT FROM AUTHOR]

Presents a letter to the editor on sunscreen's offering immunosuppression in mice, published in the September 1997 issue of "The Journal of Investigative Dermatology."

Background: Although the cytokine IL-31 has been implicated in inflammatory and lymphoma-associated itch, the cellular basis for its pruritic action is yet unclear. Objective: We sought to determine whether immune cell–derived IL-31 directly stimulates sensory neurons and to identify the molecular basis of IL-31–induced itch. Methods: We used immunohistochemistry and quantitative real-time PCR to determine IL-31 expression levels in mice and human subjects. Immunohistochemistry, immunofluorescence, quantitative real-time PCR, in vivo pharmacology, Western blotting, single-cell calcium imaging, and electrophysiology were used to examine the distribution, functionality, and cellular basis of the neuronal IL-31 receptor α in mice and human subjects. Results: Among all immune and resident skin cells examined, IL-31 was predominantly produced by TH2 and, to a significantly lesser extent, mature dendritic cells. Cutaneous and intrathecal injections of IL-31 evoked intense itch, and its concentrations increased significantly in murine atopy-like dermatitis skin. Both human and mouse dorsal root ganglia neurons express IL-31RA, largely in neurons that coexpress transient receptor potential cation channel vanilloid subtype 1 (TRPV1). IL-31–induced itch was significantly reduced in TRPV1-deficient and transient receptor channel potential cation channel ankyrin subtype 1 (TRPA1)–deficient mice but not in c-kit or proteinase-activated receptor 2 mice. In cultured primary sensory neurons IL-31 triggered Ca2+ release and extracellular signal-regulated kinase 1/2 phosphorylation, inhibition of which blocked IL-31 signaling in vitro and reduced IL-31–induced scratching in vivo. Conclusion: IL-31RA is a functional receptor expressed by a small subpopulation of IL-31RA+/TRPV1+/TRPA1+ neurons and is a critical neuroimmune link between TH2 cells and sensory nerves for the generation of T cell–mediated itch. Thus targeting neuronal IL-31RA might be effective in the management of TH2-mediated itch, including atopic dermatitis and cutaneous T-cell lymphoma. [Copyright &y& Elsevier]

Background: Exposure to house dust mites (HDMs) aggravates the course of atopic dermatitis (AD) in patients sensitized to HDMs. Objectives: This study investigated the efficacy and safety of subcutaneous allergen-specific immunotherapy with the use of depigmented polymerized mite extract as an add-on therapy to basic (ie, topical and, as necessary, systemic) medication. Methods: Patients (n = 168) were recruited in a randomized, double-blind, placebo-controlled parallel group phase III study conducted in Germany (21 sites), in adult patients with AD aggravated by HDMs. The primary end points of the study were the assessments of the area under the curves of the total Severity Scoring Atopic Dermatitis (SCORAD) score and of the use of basic medication during the 18-month treatment period. Post hoc subgroup analyses were also performed. Results: Overall efficacy analysis of the intention-to-treat and per-protocol study populations showed no statistically significant differences between the active treatment and placebo groups. However, the subgroup of patients with severe AD (SCORAD > 50) showed a statistically significant reduction of the median total SCORAD by 18% (P = .02) compared with placebo. The frequency of adverse reactions was similar in both groups, suggesting the safety of the active treatment. Conclusion: Although subcutaneous allergen-specific immunotherapy showed no statistically significant difference in the overall population of patients with AD, statistically significant reduction of the total SCORAD could be achieved in a subgroup of patients with severe AD. [ABSTRACT FROM AUTHOR]

Background: MicroRNAs (miRNAs) are short noncoding RNAs that suppress gene expression at the posttranscriptional level. Atopic dermatitis is a common chronic inflammatory skin disease characterized by the presence of activated T cells within the skin. Objective: We sought to explore the role of miRNAs in the pathogenesis of atopic dermatitis. Methods: Global miRNA expression in healthy and lesional skin of patients with atopic dermatitis was compared by using TaqMan MicroRNA Low Density Arrays. miR-155 expression in tissues and cells was quantified by means of quantitative real-time PCR. The cellular localization of miR-155 was analyzed by means of in situ hybridization. The regulation of cytotoxic T lymphocyte–associated antigen (CTLA-4) by miR-155 was investigated by using luciferase reporter assays and flow cytometry. CTLA-4 expression and functional assays were performed on TH cells overexpressing miR-155. Results: miR-155 was one of the highest-ranked upregulated miRNAs in patients with atopic dermatitis. In the skin miR-155 was predominantly expressed in infiltrating immune cells. miR-155 was upregulated during T-cell differentiation/activation and was markedly induced by T-cell activators in PBMCs in vitro and by superantigens and allergens in the skin in vivo. CTLA-4, an important negative regulator of T-cell activation, was identified as a direct target of miR-155. Overexpression of miR-155 in TH cells resulted in decreased CTLA-4 levels accompanied by an increased proliferative response. Conclusion: miR-155 is significantly overexpressed in patients with atopic dermatitis and might contribute to chronic skin inflammation by increasing the proliferative response of TH cells through the downregulation of CTLA-4. [Copyright &y& Elsevier]

Clinical manifestations of lichenoid tissue reactions are heterogenous and include the cutaneous lupus erythematosus and lichen planus. Lichenoid tissue reactions are characterized by epidermal basal-cell damage and a variable subepithelial inflammatory infiltrate including cytotoxic TH1 cells and plasmacytoid dendritic cells. Here, we summarize the current knowledge of the role of chemokines in the pathophysiology of lichenoid tissue reactions and propose mechanisms by which recruitment and local activation of cytotoxic TH1 cells and plasmacytoid dendritic cells may result in initiation and amplification of lichen planus and cutaneous lupus erythematosus.Journal of Investigative Dermatology (2009) 129, 315–319; doi:10.1038/jid.2008.251; published online 21 August 2008 [ABSTRACT FROM AUTHOR]

The ability to obtain gene expression profiles from human disease specimens provides an opportunity to identify relevant gene pathways, but is limited by the absence of data sets spanning a broad range of conditions. Here, we analyzed publicly available microarray data from 16 diverse skin conditions in order to gain insight into disease pathogenesis. Unsupervised hierarchical clustering separated samples by disease as well as common cellular and molecular pathways. Disease-specific signatures were leveraged to build a multi-disease classifier, which predicted the diagnosis of publicly and prospectively collected expression profiles with 93% accuracy. In one sample, the molecular classifier differed from the initial clinical diagnosis and correctly predicted the eventual diagnosis as the clinical presentation evolved. Finally, integration of IFN-regulated gene programs with the skin database revealed a significant inverse correlation between IFN-β and IFN-γ programs across all conditions. Our study provides an integrative approach to the study of gene signatures from multiple skin conditions, elucidating mechanisms of disease pathogenesis. In addition, these studies provide a framework for developing tools for personalized medicine toward the precise prediction, prevention, and treatment of disease on an individual level. [ABSTRACT FROM AUTHOR]

Abstract: Background: Recent studies provided insights into the recruitment and activation pathways of leukocytes in atopic dermatitis, however, the underlying mechanisms of tissue remodeling in atopic skin inflammation remain elusive. Objective: To identify chemokine-mediated communication pathways regulating tissue remodeling during atopic skin inflammation. Methods: Analysis of the chemokine receptor repertoire of human dermal fibroblasts using flow cytometry and immunofluorescence. Quantitative real-time polymerase chain reaction and immunohistochemical analyses of chemokine expression in atopic vs. non-atopic skin inflammation. Investigation of the function of chemokine receptor CCR3 on human dermal fibroblasts through determining intracellular Ca2+ mobilization, cell proliferation, migration, and repair capacity. Results: Analyses on human dermal fibroblasts showed abundant expression of the chemokine receptor CCR3 in vitro and in vivo. Among its corresponding ligands (CCL5, CCL8, CCL11, CCL24 and CCL26) CCL26 demonstrated a significant and specific up-regulation in atopic when compared to psoriatic skin inflammation. In vivo, epidermal keratinocytes showed most abundant CCL26 protein expression in lesional atopic skin. In structural cells of the skin, TH2-cytokines such as IL-4 and IL-13 were dominant inducers of CCL26 expression. In dermal fibroblasts, CCL26 induced CCR3 signaling resulting in intracellular Ca2+ mobilization, as well as enhanced fibroblast migration and repair capacity, but no proliferation. Conclusion: Taken together, findings of the present study suggest that chemokine-driven communication pathways from the epidermis to the dermis may modulate tissue remodeling in atopic skin inflammation. [Copyright &y& Elsevier]

Cutaneous squamous cell carcinoma (cSCC) is the second most common human cancer. Although dysregulation of microRNAs (miRNAs) is known to be involved in a variety of cancers, the role of miRNAs in cSCC is unclear. In this study, we aimed to identify tumor suppressive and oncogenic miRNAs involved in the pathogenesis of cSCC. MiRNA expression profiles in healthy skins (n = 4) and cSCCs (n = 4) were analyzed using MicroRNA Low Density Array. MiR-125b expression was analyzed by quantitative real-time PCR and in situ hybridization in skin biopsies from 40 healthy donors, 13 actinic keratosis, and 74 cSCC patients. The effect of miR-125b was analyzed in wound closure, colony formation, migration, and invasion assays in two cSCC cell lines, UT-SCC-7 and A431. The genes regulated by miR-125b in cSCC were identified by microarray analysis and its direct target was validated by luciferase reporter assay. Comparing cSCC with healthy skin, we identified four up-regulated miRNAs (miR-31, miR-135b, miR-21, and miR- 223) and 54 down-regulated miRNAs, including miR-125b, whose function was further examined. We found that miR-125b suppressed proliferation, colony formation, migratory, and invasive capacity of cSCC cells. Matrix metallopeptidase 13 (MMP13) was identified as a direct target suppressed by miR-125b, and there was an inverse relationship between the expression of miR-125b and MMP13 in cSCC. Knockdown of MMP13 expression phenocopied the effects of miR-125b overexpression. These findings provide a novel molecular mechanism by which MMP13 is up-regulated in cSCCs and indicate that miR- 125b plays a tumor suppressive role in cSCC. [ABSTRACT FROM AUTHOR]

Hyaluronan (HA) and versican are key components of the dermis and are responsive to ultraviolet (UV)B-induced remodeling. The aim of this study was to explore the molecular mechanisms mediating the effects of estrogen (E2) on HA-rich extracellular matrix during photoaging. Hairless skh-1 mice were irradiated with UVB (three times, 1 minimal erythema dose (80 mJ/cm2), weekly) for 10 weeks, and endogenous sex hormone production was abrogated by ovariectomy. Subcutaneous substitution of E2 by means of controlled-release pellets caused a strong increase in the dermal HA content in both irradiated and nonirradiated skin. The increase in dermal HA correlated with induction of HA synthase HAS3 by E2. Expression of splice variant 2 of the HA-binding proteoglycan versican was also increased by E2. In search of candidate mediators of these effects, it was found that E2 strongly induced the expression of epidermal growth factor (EGF) in UVB-irradiated epidermis in vivo and in keratinocytes in vitro. EGF in turn up-regulated the expression of HAS3 and versican V2 in dermal fibroblasts. HAS3 knockdown by shRNA caused inhibition of fibroblast proliferation. Furthermore, HAS3 and versican V2 induction by E2 correlated positively with proliferation in vivo. In addition, the accumulation of inflammatory macrophages, expression of inducible cyclooxygenase 2, as well as proinflammatory monocyte chemotactic protein 1 were decreased in response to E2 in the dermis. Collectively, these data suggest that E2 treatment increases the amount of dermal HA and versican V2 via paracrine release of EGF, which may be implicated in the pro-proliferative and anti-inflammatory effects of E2 during photoaging. [ABSTRACT FROM AUTHOR]

Immune activation of fibrosis likely has a crucial role in the pathogenesis of systemic sclerosis (SSc). The aim of this study was to better understand the innate immune regulation and associated IFN- and transforming growth factor-β (TGFβ)-responsive gene expression in SSc skin and dermal fibroblasts, in particular the effect of different Toll-like receptor (TLR) ligands. To better understand the relationship between inflammation and fibrosis in vivo, we developed a murine model for chronic innate immune stimulation. We found that expression of both IFN- and TGFβ-responsive genes is increased in SSc skin and SSc fibroblasts when stimulated by TLR ligands. In contrast, cutaneous lupus skin showed much more highly upregulated IFN-responsive and much less highly upregulated TGFβ-responsive gene expression. Of the TLRs ligands tested, the TLR3 ligand, polyinosinic/polycytidylic acid (Poly(I:C)), most highly increased fibroblast expression of both IFN- and TGFβ-responsive genes as well as TLR3. Chronic subcutaneous immune stimulation by Poly(I:C) stimulated inflammation, and IFN- and TGFβ-responsive gene expression. However, in this model, type I IFNs had no apparent role in regulating TGFβ activity in the skin. These results suggest that TLR agonists may be important stimuli of dermal fibrosis, which is potentially mediated by TLR3 or other innate immune receptors. [ABSTRACT FROM AUTHOR]

Recent studies have demonstrated that the chemokine receptor CXCR4 plays a crucial role in organ-specific metastasis formation. Although a variety of studies showed the expression of chemokine receptors, in particular, CXCR4, by gastrointestinal tumors, the precise mechanisms of chemokine receptor-mediated homing of cancer cells to specific sites of metastasis remained elusive. Here, we used liver metastatic human HEP-G2 hepatoma and HT-29LMMcolon cancer cells expressing functional CXCR4 to dissect the metastatic cascade by intravital fluorescence microscopy. Immunohistochemistry revealed that the CXCR4 ligand CXCL12 is expressed by endothelial cells and likely Kupffer cells lining the liver sinusoids. Tumor cell adhesion and extravasation in vivo was quantitatively analyzed using intravital fluorescence microscopy. Treatment of cells with an anti-CXCR4 antibody did not affect cell adhesion but significantly impaired tumor cell extravasation (HEP-G2; isotype control: 22.3% ± 4.3% vs anti-CXCR4: 6.0% ± 5.0%, P < .001). In addition, pretreatment of tumor cells with the ligand CXCL12 enhanced the activation of the small GTPases Rho, Rac, and cdc42 as well as tumor cell extravasation without affecting tumor cell adhesion within liver sinusoids. Taken together, the findings of the present study provide first in vivo insights into the early events of chemokine ligand/receptor-mediated liver metastasis formation of tumor cells and define tumor cell extravasation rather than tumor cell arrest as the rate-limiting event. [ABSTRACT FROM AUTHOR]

Tissue-specific T cell localization is crucial for immune surveillance of normal tissues and the pathogenesis of inflammatory disorders. In psoriatic skin, CD8+ lymphocytes predominantly reside within the epidermis, whereas CD4+ T cells are most abundant within the dermis. Molecular mechanisms guiding this spatial compartmentalization are not completely understood, however. Here, we demonstrate that 55% (±9.7%, n = 14) of the epidermal T cells, predominantly of the CD8+ phenotype, expressed the integrin αE (CD103)β7 . In contrast, only 5% (±2.0%) of the dermal T cells were αE (CD103)β7 + . Integrin αE (CD103)β7 was not detected in normal skin (n = 10), and less than 1% of peripheral blood lymphocytes derived from normal (n = 11) or psoriatic (n = 10) donors expressed αE (CD103). When cultured T lymphoblasts (n = 12 donors) were stimulated with transforming growth factor β1 , expression of integrin αE (CD103)β7 was induced on 52.8% (±16.2%) of CD8+ cells, but only on 6.1% (±2.3%) of CD4+ cells, suggesting selective inducibility on CD8+ lymphocytes. Whereas similar overall expression of transforming-growth-factor-β1 -specific mRNA was detected in normal and psoriatic skin by real-time quantitative polymerase chain reaction, immunohistochemistry revealed focal overexpression of transforming growth factor β1 underneath psoriatic, but not normal, epidermis. This heterogenous transforming growth factor β1 expression may contribute to induction of αE (CD103) in vivo . Adhesion of transforming-growth-factor-β1 -stimulated CD8+ , but not CD4+ , T cells to cultured keratinocytes and psoriatic epidermis in frozen... [ABSTRACT FROM AUTHOR]