Cutting edge: C-C chemokine receptor 6 is essential for arrest of a subset of memory T cells on activated dermal microvascular endothelial cells under physiologic flow conditions in vitro

Oncostatin M triggers brain inflammation by compromising blood-brain barrier integrity

Oncostatin M (OSM) is an IL-6 family member which exerts neuroprotective and remyelination-promoting effects after damage to the central nervous system (CNS). However, the role of OSM in neuro-inflammation is poorly understood. Here, we investigated OSM's role in pathological events important for the neuro-inflammatory disorder multiple sclerosis (MS). We show that OSM receptor (OSMRβ) expression is increased on circulating lymphocytes of MS patients, indicating their elevated responsiveness to OSM signalling. In addition, OSM production by activated myeloid cells and astrocytes is increased in MS brain lesions. In experimental autoimmune encephalomyelitis (EAE), a preclinical model of MS, OSMRβ-deficient mice exhibit milder clinical symptoms, accompanied by diminished T helper 17 (Th17) cell infiltration into the CNS and reduced BBB leakage. In vitro, OSM reduces BBB integrity by downregulating the junctional molecules claudin-5 and VE-cadherin, while promoting secretion of the Th17-attracting chemokine CCL20 by inflamed BBB-endothelial cells and reactive astrocytes. Using flow cytometric fluorescence resonance energy transfer (FRET) quantification, we found that OSM-induced endothelial CCL20 promotes activation of lymphocyte function-associated antigen 1 (LFA-1) on Th17 cells. Moreover, CCL20 enhances Th17 cell adhesion to OSM-treated inflamed endothelial cells, which is at least in part ICAM-1 mediated. Together, these data identify an OSM-CCL20 axis, in which OSM contributes significantly to BBB impairment during neuro-inflammation by inducing permeability while recruiting Th17 cells via enhanced endothelial CCL20 secretion and integrin activation. Therefore, care should be taken when considering OSM as a therapeutic agent for treatment of neuro-inflammatory diseases such as MS.

Decreased MIP-3α Production from Antigen-Activated PBMCs in Symptomatic HIV-Infected Subjects

CD4⁺ CCR6⁺ T cells are highly susceptible to HIV infection, and a high cytokine producing CCR6⁺ T cell subset is selectively lost during HIV infection. The CCR6 chemokine MIP-3α (CCL20) is produced at sites of infection in SIV animal models. Recently, we have shown that MIP-3α inhibits HIV replication. This inhibition of HIV infection is mediated by CCR6 signaling and eventuates in increased APOBEC3G expression. Since there are few existing reports on the role of MIP-3α in health or disease, we studied its production by PBMCs from HIV-seronegative and HIV+ subjects. We evaluated the ability of PBMCs to produce MIP-3α in response to antigen stimulation using cells obtained from two groups: one composed of HIV-seronegative subjects (n = 16) and the other composed of HIV+ subjects (n = 58), some asymptomatic and some with clinically defined AIDS. Antigens included fragment C of the tetanus toxin, Candida albicans, whole-inactivated HIV, and HIV p24. MIP-3α was detected by ELISA in tissue culture supernatants of antigen-stimulated PBMCs. MIP-3α production by antigen-stimulated PBMCs was readily measured for HIV-negative subjects and for HIV-seropositive asymptomatic subjects, but not for patients with AIDS. These results suggest that subversion of the MIP-3α-CCR6 axis by HIV during the course of infection contributes to the loss of immune function that eventually leads to AIDS.

B Cell Responses in the Development of Mammalian Meat Allergy

Studies of meat allergic patients have shown that eating meat poses a serious acute health risk that can induce severe cutaneous, gastrointestinal, and respiratory reactions. Allergic reactions in affected individuals following meat consumption are mediated predominantly by IgE antibodies specific for galactose-α-1,3-galactose (α-gal), a blood group antigen of non-primate mammals and therefore present in dietary meat. α-gal is also found within certain tick species and tick bites are strongly linked to meat allergy. Thus, it is thought that exposure to tick bites promotes cutaneous sensitization to tick antigens such as α-gal, leading to the development of IgE-mediated meat allergy. The underlying immune mechanisms by which skin exposure to ticks leads to the production of α-gal-specific IgE are poorly understood and are key to identifying novel treatments for this disease. In this review, we summarize the evidence of cutaneous exposure to tick bites and the development of mammalian meat allergy. We then provide recent insights into the role of B cells in IgE production in human patients with mammalian meat allergy and in a novel mouse model of meat allergy. Finally, we discuss existing data more generally focused on tick-mediated immunomodulation, and highlight possible mechanisms for how cutaneous exposure to tick bites might affect B cell responses in the skin and gut that contribute to loss of oral tolerance.

Beyond migration-Chemokines in lymphocyte priming, differentiation, and modulating effector functions

Chemokines and their receptors coordinate the positioning of leukocytes, and lymphocytes in particular, in space and time. Discrete lymphocyte subsets, depending on their activation and differentiation status, express various sets of chemokine receptors to be recruited to distinct tissues. Thus, the network of chemokines and their receptors ensures the correct localization of specialized lymphocyte subsets within the appropriate microenvironment enabling them to search for cognate antigens, to become activated, and to fulfill their effector functions. The chemokine system therefore is vital for the initiation as well as the regulation of immune responses to protect the body from pathogens while maintaining tolerance towards self. Besides the well investigated function of orchestrating directed cell migration, chemokines additionally act on lymphocytes in multiple ways to shape immune responses. In this review, we highlight and discuss the role of chemokines and chemokine receptors in controlling cell-to-cell contacts required for lymphocyte arrest on endothelial cells and immunological synapse formation, in lymphocyte priming and differentiation, survival, as well as in modulating effector functions.

C/EBPδ drives interactions between human MAIT cells and endothelial cells that are important for extravasation

Many mediators and regulators of extravasation by bona fide human memory-phenotype T cells remain undefined. Mucosal-associated invariant T (MAIT) cells are innate-like, antibacterial cells that we found excelled at crossing inflamed endothelium. They displayed abundant selectin ligands, with high expression of FUT7 and ST3GAL4, and expressed CCR6, CCR5, and CCR2, which played non-redundant roles in trafficking on activated endothelial cells. MAIT cells selectively expressed CCAAT/enhancer-binding protein delta (C/EBPδ). Knockdown of C/EBPδ diminished expression of FUT7, ST3GAL4 and CCR6, decreasing MAIT cell rolling and arrest, and consequently the cells' ability to cross an endothelial monolayer in vitro and extravasate in mice. Nonetheless, knockdown of C/EBPδ did not affect CCR2, which was important for the step of transendothelial migration. Thus, MAIT cells demonstrate a program for extravasastion that includes, in part, C/EBPδ and C/EBPδ-regulated genes, and that could be used to enhance, or targeted to inhibit T cell recruitment into inflamed tissue.

Enhancement of β-Globin Gene Expression in Thalassemic IVS2-654 Induced Pluripotent Stem Cell-Derived Erythroid Cells by Modified U7 snRNA

The therapeutic use of patient‐specific induced pluripotent stem cells (iPSCs) is emerging as a potential treatment of β‐thalassemia. Ideally, patient‐specific iPSCs would be genetically corrected by various approaches to treat β‐thalassemia including lentiviral gene transfer, lentivirus‐delivered shRNA, and gene editing. These corrected iPSCs would be subsequently differentiated into hematopoietic stem cells and transplanted back into the same patient. In this article, we present a proof of principle study for disease modeling and screening using iPSCs to test the potential use of the modified U7 small nuclear (sn) RNA to correct a splice defect in IVS2‐654 β‐thalassemia. In this case, the aberration results from a mutation in the human β‐globin intron 2 causing an aberrant splicing of β‐globin pre‐mRNA and preventing synthesis of functional β‐globin protein. The iPSCs (derived from mesenchymal stromal cells from a patient with IVS2‐654 β‐thalassemia/hemoglobin (Hb) E) were transduced with a lentivirus carrying a modified U7 snRNA targeting an IVS2‐654 β‐globin pre‐mRNA in order to restore the correct splicing. Erythroblasts differentiated from the transduced iPSCs expressed high level of correctly spliced β‐globin mRNA suggesting that the modified U7 snRNA was expressed and mediated splicing correction of IVS2‐654 β‐globin pre‐mRNA in these cells. Moreover, a less active apoptosis cascade process was observed in the corrected cells at transcription level. This study demonstrated the potential use of a genetically modified U7 snRNA with patient‐specific iPSCs for the partial restoration of the aberrant splicing process of β‐thalassemia. Stem Cells Translational Medicine2017;6:1059–1069

Early CCR6 expression on B cells modulates germinal centre kinetics and efficient antibody responses

The CC-chemokine receptor 6 (CCR6) can be detected on naive and activated B cells. Counterintuitively, its absence accelerates the appearance of germinal centres (GCs) and increases the production of low-affinity antibodies. The detailed mechanism of CCR6 function during the humoral response has remained elusive, but previously we identified a distinct CCR6^high B-cell population in vivo early after antigenic challenge. In this study, we defined this population specifically as early, activated pre-GC B cells. In accordance, we show that CCR6 is upregulated rapidly within hours on the protein or mRNA level after activation in vitro. In addition, only activated B cells migrated specifically towards CCL20, the specific ligand for CCR6. Lack of CCR6 increased the dark zone/light zone ratio of GC and led to decreased antigen-specific IgG1 and IgG2a antibody generation in a B-cell intrinsic manner in mixed bone marrow chimeras. In contrast, antigen-specific IgM responses were normal. Hence, CCR6 negatively regulates entry of activated, antigen-specific pre-GC B cells into the GC reaction.

Revisiting the role of B cells in skin immune surveillance

Whereas our understanding of the skin immune system has increased exponentially in recent years, the role of B cells in cutaneous immunity remains poorly defined. Recent studies have revealed the presence of B cells within lymphocytic infiltrates in chronic inflammatory skin diseases and cutaneous malignancies including melanoma, and have examined their functional significance in these settings. We review these findings and discuss them in the context of the current understanding of the role of B cells in normal skin physiology, as well as in both animal and human models of skin pathology. We integrate these findings into a model of cutaneous immunity wherein crosstalk between B cells and other skin-resident immune cells plays a central role in skin immune homeostasis.

CCR6 is a prognostic marker for overall survival in patients with colorectal cancer, and its overexpression enhances metastasis in vivo

The chemokine receptor CCR6 has been recently shown to be associated with colorectal cancer (CRC) progression. However, the direct evidence for whether CCR6 in tumors is a prognostic marker for the survival of patients with CRC and whether it plays a critical role in CRC metastasis in vivo is lacking. Here we show that the levels of CCR6 were upregulated in CRC cell lines and primary CRC clinical samples. CCR6 upregulation was closely correlated with disease stages and the survival time of CRC patients. Knockdown of CCR6 inhibited the migration of CRC cells in vitro. Overexpression of CCR6 in CRC cells increased their proliferation, migration, and colony formation in vitro and promoted their metastatic potential in vivo. CCR6 activated Akt signaling, upregulated metastasis genes and downregulated metastasis suppressor genes. Selective targeting of CCR6 in tumors dramatically inhibited the growth of CRC in mice. Thus, the tumor expression of CCR6 plays a critical role in CRC metastasis, upregulated CCR6 predicts poor survival in CRC patients, and targeting CCR6 expression in tumors may be a potential therapeutic strategy for CRC.

The CCR6/CCL20 axis mediates Th17 cell migration to the ocular surface in dry eye disease

PURPOSE

Th17 cells are believed to be the primary effector cells in the pathogenesis of dry eye disease (DED). However, the mechanisms by which Th17 cells migrate from the lymphoid tissues to the ocular surface are unknown. The purpose of this study was to investigate the role of the C-C chemokine receptor 6/C-C chemokine ligand 20 (CCR6/CCL20) chemokine axis in mediating Th17 cell migration in DED.

METHODS

DED was induced by housing C57BL/6 mice in a low-humidity environment supplemented with scopolamine treatment. Th17 cell expression of CCR6 was evaluated using flow cytometry and ocular surface expression of CCL20 was measured using PCR and ELISA assays. CCL20 neutralizing antibody was administered subconjunctivally to DED mice and disease severity, including the frequency of conjunctival Th17 cells, was evaluated.

RESULTS

CCR6 is preferentially expressed by Th17 cells in both normal and DED mice and DED significantly upregulates ocular surface expression of CCL20. Disruption of CCR6/CCL20 binding with CCL20 neutralizing antibody decreases T-cell migration in vitro and reduces Th17 cell infiltration of the conjunctiva when administered in vivo, significantly improving clinical signs of DED. These changes were accompanied by a decrease in ocular surface inflammatory cytokine levels and corneal CD11b+ cell frequencies. Treatment also significantly reduced the generation of Th17 cells.

CONCLUSIONS

Local neutralization of CCL20 decreases Th17 cell infiltration of the ocular surface in DED, leading to improvement in clinical signs of disease. This suggests that CCR6/CCL20 interactions direct Th17 cell migration in DED and that disruption of this axis may be a novel therapeutic approach to this condition.

Chemokine receptors in the pathogenesis and therapy of psoriasis

Chemokine receptors are G-protein-coupled, seven-transmembrane-spanning surface receptors that play key roles in cell trafficking, cell motility, and survival. These receptors are activated by small molecular weight chemotactic cytokines called chemokines. Chemokine receptors and their corresponding chemokine ligands play roles in the migration and localization of normal T cells (and other cells) during physiological responses in inflamed or infected skin. In psoriasis, the chemokine receptor CCR6 is expressed on the Th17 cells and γδ T cells, which produce a variety of cytokines (IL17 and IL22 among others), that play a role in the immunological activation. CCR6 and its ligand, CCL20, are highly expressed in psoriatic skin lesion and CCR6 is essential for the development of the psoriasiform phenotype following IL23 injection in mouse skin. In this review, we focus on the roles of chemokine receptors, particularly of CCR6, in the pathogenesis of psoriasis and discuss chemokine receptors as novel therapeutic targets for psoriasis.

Increased frequency of circulating Th22 in addition to Th17 and Th2 lymphocytes in systemic sclerosis: association with interstitial lung disease

INTRODUCTION

T cell abnormalities have been associated with the pathogenesis of systemic sclerosis (SSc). Recently, besides T helper (Th)17 cells, the Th22 subset has been identified in humans. Our purpose was to investigate the pattern of cytokines produced and chemokine-receptors expressed by peripheral blood (PB) Th cells in SSc and healthy donors (HD) focusing on cells producing interleukin (IL)-17 and IL-22 and to identify specific clinical associations.

METHODS

Clinical data and peripheral blood were collected in 33 SSc individuals and 29 HD. IL-17A, IL-22, interferon gamma (IFN-γ), IL-4 production, the chemokine receptors CCR4, CCR6, CCR10, CXCR3 expression and the CD161 Th17 cell marker were assessed by multiparametric flow cytometry in PB CD4+ T cells. Intracellular cytokine accumulation was further investigated in CD4+ T cells expanded in vitro for seven days.

RESULTS

The frequency of Th22, Th17, Th2, but not Th1 cells, was significantly increased in SSc individuals compared to HD. The percentage of CD161+CD4+ T cells was increased in SSc and correlated with the percentage of IL-17A producing cells. Moreover, the expression of the skin- and lung-homing chemokine receptor CCR6 correlated with the frequency of IL-22 and IL-17A-producing cells in SSc but not in HD. Finally, SSc interstitial lung disease (ILD) was strongly associated with higher numbers of IL-22 and, to a lesser extent, IL-17A-producing cells.

CONCLUSIONS

IL-22 and IL-17A-producing T cells with skin- and lung-homing capabilities are characteristically increased in SSc. These findings support the hypothesis that Th22, in addition to Th17 cells, may be involved in pathological processes leading to SSc. While the association between IL-22 producing cells and ILD needs to be assessed in larger cohorts of patients, the increased frequency of Th22 cells appears to be a useful novel biomarker in SSc.

Keratinocyte Growth Factor Stimulates Macrophage Inflammatory Protein 3α and Keratinocyte-derived Chemokine Secretion by Mouse Uterine Epithelial Cells

PROBLEM

communication between uterine epithelial cells and the underlying stromal fibroblasts is critical for proper endometrial function. Stromal fibroblast-derived growth factors have been shown to regulate epithelial immune functions. The purpose of this study was to determine whether keratinocyte growth factor (KGF) regulates uterine epithelial cell chemokine and antimicrobial secretion.

METHOD OF STUDY

uterine epithelial cells were isolated from Balb/c mice and cultured in either 96-well plates or transwell inserts. Epithelial cells were treated with KGF, epidermal growth factor (EGF), or hepatocyte growth factor (HGF). Macrophage inflammatory protein 3α (MIP3α) and keratinocyte-derived chemokine (KC) levels were measured by ELISA.

RESULTS

keratinocyte growth factor stimulated the secretion of MIP3α and KC. The effects on MIP3α by KGF were specific because EGF and HGF had no effect. In contrast, KGF, EGF, and HGF had similar effects on KC. Furthermore, KGF administered to the apical side of epithelial cells had no effect on MIP3α or KC secretion, indicating that the KGF receptor is located on the basolateral surface of uterine epithelial cells.

CONCLUSION

we demonstrate that KGF plays a role in uterine epithelial cell secretion of MIP3α and KC, key immune mediators involved in the protection of mucosal surfaces in the female reproductive tract.

In vivo dioxin favors interleukin-22 production by human CD4+ T cells in an aryl hydrocarbon receptor (AhR)-dependent manner

BACKGROUND

The transcription factor aryl hydrocarbon receptor (AhR) mediates the effects of a group of chemicals known as dioxins, ubiquitously present in our environment. However, it is poorly known how the in vivo exposure to these chemicals affects in humans the adaptive immune response. We therefore assessed the functional phenotype of T cells from an individual who developed a severe cutaneous and systemic syndrome after having been exposed to an extremely high dose of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD).

METHODOLOGY/PRINCIPAL FINDINGS

T cells of the TCDD-exposed individual were studied for their capacity to produce cytokines in response to polyclonal and superantigenic stimulation, and for the expression of chemokine receptors involved in skin homing. The supernatants from T cells of the exposed individual contained a substantially increased amount of interleukin (IL)-22 but not of IL-17A, interferon (IFN)-γ or IL-10 when compared to nine healthy controls. In vitro experiments confirmed a direct, AhR-dependent, enhancing effect of TCDD on IL-22 production by CD4+ T cells. The increased production of IL-22 was not dependent on AhR occupancy by residual TCDD molecules, as demonstrated in competition experiments with the specific AhR antagonist CH-223191. In contrast, it was due to an increased frequency of IL-22 single producing cells accompanied by an increased percentage of cells expressing the skin-homing chemokine receptors CCR6 and CCR4, identified through a multiparameter flow cytometry approach. Of interest, the frequency of CD4+CD25(hi)FoxP3+ T regulatory cells was similar in the TCDD-exposed and healthy individuals.

CONCLUSIONS/SIGNIFICANCE

This case strongly supports the contention that human exposure to persistent AhR ligands in vivo induce a long-lasting effect on the human adaptive immune system and specifically polarizes CD4+ T cells to produce IL-22 and not other T cell cytokines with no effect on T regulatory cells.

CCL20 and β-defensin-2 induce arrest of human Th17 cells on inflamed endothelium in vitro under flow conditions

CCR6 is a chemokine receptor that is expressed at the cell surface of Th17 cells, an IL-17- and IL-22-secreting population of CD4(+) T cells with antipathogenic, as well as inflammatory, properties. In the current study, we have determined the involvement of CCR6 in human Th17 lymphocyte migration toward inflamed tissue by analyzing the capacity of its ligands to induce arrest of these cells onto inflamed endothelium in vitro under flow conditions. We show that polarized, in situ-differentiated, skin-derived Th17 clones activated via the TCR-CD3 complex produce CCL20 in addition to IL-17 and IL-22. The latter cytokines induce, in a synergic fashion, the production of human β-defensin (hBD)-2, but neither hBD-1 nor hBD-3, by epidermal keratinocytes. Both CCL20 and hBD-2 are capable of inducing the arrest of Th17 cells, but not Th1 or Th2 cells, on HUVEC in an CD54-dependent manner that is CCR6 specific and independent from the expression of CXCR4, reported to be an alternative receptor for hBD-2. In addition, Ag-specific activation induces a transient loss of CCR6 expression, both at the transcriptional and protein level, which occurs with slow kinetics and is not due to endogenous CCL20-mediated internalization of CCR6. Together, these results indicate that Ag-specific activation will initially contribute to CCR6-mediated Th17 cell trafficking toward and sequestration in inflamed tissue, but that it eventually results in a transitory state of nonresponsiveness to further stimulation of these cells with CCR6 ligands, thus permitting their subsequent migration out of the inflamed site.

The immune system, the skin, and childhood rheumatic disease

As the body's largest organ and first line of defense against the environment, the skin plays a vital role in host immune defense. In addition to its function as a physical barrier, the skin contains an active immune surveillance network and can mount highly specific responses to eliminate invading organisms. In this review, we discuss the functions of adhesion molecules in regulating the recruitment of distinct cell populations to skin in both healthy and disease states, and the interaction between innate and adaptive immune mechanisms active in the skin. We also review how these systems underlie the pathogenesis of skin manifestations of pediatric rheumatologic diseases.

Expression of the chemokine receptor CCR6 correlates with a favorable prognosis in patients with adenocarcinoma of the lung

The relation between CCR6 expression and the clinicopathological characteristics of lung cancer and patient prognosis is not well understood and remains controversial. We, therefore, investigated the relationship between CCR6 expression and prognosis in patients with adenocarcinoma of the lung. We used semiquantitative real-time reverse transcription polymerase chain reaction to assess the expression of CCR6 mRNA in tumor samples from 84 patients with adenocarcinoma of the lung. We then correlated the levels of CCR6 mRNA with known clinicopathological features. The 5-year disease-free survival rate among patients expressing higher levels of CCR6 mRNA was significantly better than among those expressing lower levels (P = 0.009 by log-rank test). Multivariate Cox proportional hazard analyses revealed, being male [hazard ratio, 3.94; 95% confidence interval (CI), 1.58 to 10.36; P = 0.003], tumor size >30 mm (hazard ratio, 2.46; 95% CI, 1.08 to 5.73; P = 0.030), nodal metastasis (hazard ratio, 7.66; 95% CI, 2.62 to 23.3; P = 0.0002), and CCR6 (hazard ratio, 0.34; 95% CI, 0.11 to 0.93; P = 0.034) to be independent factors affecting the 5-year disease-free survival rate. Greater expression of CCR6 by tumor cells is an independent predictor of a better prognosis in patients with adenocarcinoma of the lung.

Regulatory T cells can prevent memory CD8+ T-cell-mediated rejection following polymorphonuclear cell depletion

Accumulating evidence suggests that alloreactive memory T cells (Tm) may form a barrier to tolerance induction in large animals and humans due in part to a resistance to suppression by Treg. However, why Tm are resistant to regulation and how the Tm response to an allograft differs from that of naïve T cells, which are amenable to suppression by Treg, remains unknown. Here, we show that accelerated graft rejection mediated by CD8⁺ Tm was due to the enhanced recruitment of PMN to allografts in a mouse skin allograft model. Importantly, depletion of PMN slowed the kinetics of (but did not prevent) rejection mediated by Tm and created a window of opportunity that allowed subsequent suppression of rejection by Treg. Taken together, we conclude that CD8⁺ Tm are not intrinsically resistant to suppression by Treg but may rapidly inflict substantial graft damage before the establishment of regulatory mechanisms. These data suggest that if Tm responses can be attenuated transiently following transplantation, Treg may be able to maintain tolerance through the suppression of both memory and naïve alloreactive T-cell responses in the long term.

CCR6 as a possible therapeutic target in psoriasis

IMPORTANCE OF THE FIELD

Psoriasis is a common, chronic autoimmune disease of the skin. Despite a number of effective treatments, new therapies are needed with enhanced efficacy, safety and convenience. Chemokine receptors are GPCRs that control leukocyte trafficking, and like other GPCRs, are good potential drug targets. The chemokine receptor CCR6 is expressed on the T(H)17 subset of CD4(+) T cells, which produces IL-17A/F, IL-22, TNF-alpha and other cytokines, and which has been implicated in the pathogenesis of psoriasis. CCR6 and its ligand, CCL20/MIP-3alpha, are highly expressed in psoriatic skin and CCR6 is necessary for the pathology induced in a mouse model of psoriasis-like inflammation.

AREAS COVERED IN THIS REVIEW

This review summarizes the evidence for the importance of the IL-23/T(H)17 axis, and in particular CCR6 and CCL20 in psoriasis, dating from 2000 to the present, and discusses the possibility of inhibiting CCR6 as a treatment for the disease.

WHAT THE READER WILL GAIN

The review informs the reader of the current thinking on the mechanisms of inflammation in psoriasis and the possible roles for CCR6 (and CCL20) in disease pathogenesis.

TAKE HOME MESSAGE

We conclude that CCR6 should be investigated as a potential therapeutic target in psoriasis.

Induced Sézary syndrome PBMCs poorly express immune response genes up-regulated in stimulated memory T cells

BACKGROUND

Dysfunctions in memory T cells contribute to various inflammatory autoimmune diseases and neoplasms. We hypothesize that investigating the differences of genetic profiles between resting and activated naïve and memory T cells may provide insight into the characterization of abnormal memory T cells in diseases, such as Sézary syndrome (SS), a neoplasm composed of CD4(+) CD45RO(+) cells.

OBJECTIVE

We determined genes distinctively expressed between resting and activated naive and memory cells. Levels of up-regulated genes in resting and activated memory cells were measured in SS PBMCs, which were largely comprised of CD4(+) CD45RO(+) cells, to quantitatively assess how different Sézary cells were from memory cells.

METHODS

We compared gene expression profiles using high-density oligo-microarrays between resting and activated naïve and memory CD4(+) T cells. Differentially expressed genes were confirmed by qRT-PCR and immunoblotting. Levels of genes up-regulated in activated and resting memory T cells were determined in SS PBMCs by qRT-PCR.

RESULTS

Activated memory cells expressed greater numbers of immune-mediated genes involved in effector function compared to naïve cells in our microarray analysis and qRT-PCR. Nine out of 14 genes with enhanced levels in activated memory cells had reduced levels in SS PBMCs (p<0.05).

CONCLUSIONS

Activation of memory and naïve CD4(+) T cells revealed a diverging gap in gene expression between these subsets, with memory cells expressing immune-related genes important for effector function. Many of these genes were markedly depressed in SS patients, implying Sézary cells are markedly impaired in mounting immune responses compared to memory cells.

CCR6 ligands inhibit HIV by inducing APOBEC3G

We have identified a post-entry CCR6-dependent mechanism of inhibition of HIV occurring at an early stage of infection mediated by the induction of the host restriction factor apolipoprotein B mRNA-editing enzyme-catalytic polypeptide-like 3G (APOBEC3G). We observed induction of APOBEC3G expression only in CCR6(+) cells but not in cells treated with the G inhibitory (Gi) pathway inhibitor pertussis toxin. CCR6 is highly expressed on peripheral blood CD4(+)CCR5(+) memory T cells and by 2 populations of CD4(+) T cells within the gut, alpha4beta7(+) and T helper type 17, that have been implicated in cell-to-cell spread of HIV and enhanced restoration of CD4(+) T cells within gut-associated lymphoid tissue, respectively. This novel CCR6-mediated mechanism of inhibition allows the identification of pathways that induce intrinsic immunity to HIV, which could be useful in devising novel therapeutics that selectively target CCR6(+) cells.

Chemokine receptors in T-cell-mediated diseases of the skin

The chemokine/chemokine receptor network is an integral element of the complex system of homeostasis and immunosurveillance. Initially studied because of their role in coordinating tissue-specific migration and activation of leucocytes, chemokines have been implicated in the pathogenesis of various malignancies and diseases with strong inflammatory components. We discuss recent findings suggesting a critical involvement of chemokine receptor interactions in the immunopathogenesis of classical inflammatory skin disorders such as psoriasis and atopic dermatitis, as well as neoplastic diseases with a T-cell origin, such as mycosis fungoides. A deeper understanding of the underlying contribution of the chemokine network in the disease processes is key for the development of selective targeted immunotherapeutics that may meet the delicate balance between efficacy and safety.

Inhibition of CCR6 function reduces the severity of experimental autoimmune encephalomyelitis via effects on the priming phase of the immune response

Chemokines are essential for homeostasis and activation of the immune system. The chemokine ligand/receptor pairing CCL20/CCR6 is interesting because these molecules display characteristics of both homeostatic and activation functions. These dual characteristics suggest a role for CCR6 in the priming and effector phases of the immune response. However, while CCR6 has been implicated in the effector phase in several models, a role in the priming phase is less clear. Herein we analyze the role of CCR6 in these two important arms of the immune response during experimental autoimmune encephalomyelitis (EAE). Both CCR6 and its chemokine ligand CCL20 were up-regulated in the draining lymph nodes and spinal cord during EAE, and CCR6 was up-regulated on CD4(+) T cells that had divided following induction of EAE. The functional role of this expression was demonstrated by impaired development of EAE in gene-targeted CCR6-deficient mice and in mice treated either with a neutralizing anti-CCR6 Ab or with a novel receptor antagonist. Inhibition of EAE was due to reduced priming of autoreactive CD4(+) T cells probably as a result of impaired late-stage influx of dendritic cells into draining lymph nodes. This was accompanied by reduced egress of activated lymphocytes from the lymph nodes. These results demonstrate a novel role for CCR6 in the mechanism of autoreactive lymphocyte priming and emigration to the efferent lymphatics.

CCL20 production is induced in human dental pulp upon stimulation by Streptococcus mutans and proinflammatory cytokines

INTRODUCTION

Pulpitis is characterized by the marked infiltration of inflammatory cells in response to an invasion of caries-related bacteria. It is well known that chemokines regulate the trafficking of lymphocytes, and CC chemokine ligand 20 (CCL20) has been recently shown to play a crucial role in the recruitment of memory T cells and immature dendritic cells into inflammatory lesions. We previously reported that CCL20 was mainly expressed in microvascular endothelial cells and macrophages that accumulated in inflamed pulp tissues and that its specific receptor, CCR6, was expressed on infiltrated lymphocytes. However, the mechanism of CCL20 expression remains unclear.

METHODS AND RESULTS

In this study, we investigated the expression of CCL20 in monocytes/macrophages, endothelial cells, and pulpal fibroblasts after stimulation with Streptococcus mutans, a representative of caries-related bacteria, or proinflammatory cytokines. CCL20 messenger RNA was detected by reverse transcription-polymerase chain reaction in inflamed pulp, but not in clinically normal pulp. By enzyme-linked immunosorbent assay, S. mutans induced a human monocytic cell line, differentiated macrophage-like THP-1 cells, and human umbilical vein endothelial cells (HUVEC) to produce an increased amount of CCL20. Lipoteichoic acid from S. mutans also elicited CCL20 production by HUVEC. Moreover, CCL20 production from pulpal fibroblasts was increased by stimulation with inetrleukin-1beta and tumor necrosis factor-alpha.

CONCLUSION

Our results indicate that CCL20 expression is induced by stimulation with caries-related bacteria that have invaded deeply into the dentinal tubules as well as by proinflammatory cytokines in the inflamed pulpal lesions. It may be involved in the progression of pulpitis via accumulation of inflammatory cells.

Tracing functional antigen-specific CCR6 Th17 cells after vaccination

Background

The function of T helper cell subsets in vivo depends on their location, and one hallmark of T cell differentiation is the sequential regulation of migration-inducing chemokine receptor expression. CC-chemokine receptor 6 (CCR6) is a trait of tissue-homing effector T cells and has recently been described as a receptor on T helper type 17 (Th17) cells. Th17 cells are associated with autoimmunity and the defence against certain infections. Although, the polarization of Th cells into Th17 cells has been studied extensively in vitro, the development of those cells during the physiological immune response is still elusive.

Methodology/Principal Findings

We analysed the development and functionality of Th17 cells in immune-competent mice during an ongoing immune response. In naïve and vaccinated animals CCR6⁺ Th cells produce IL-17. The robust homeostatic proliferation and the presence of activation markers on CCR6⁺ Th cells indicate their activated status. Vaccination induces antigen-specific CCR6⁺ Th17 cells that respond to in vitro re-stimulation with cytokine production and proliferation. Furthermore, depletion of CCR6⁺ Th cells from donor leukocytes prevents recipients from severe disease in experimental autoimmune encephalomyelitis, a model for multiple sclerosis in mice.

Conclusions/Significance

In conclusion, we defined CCR6 as a specific marker for functional antigen-specific Th17 cells during the immune response. Since IL-17 production reaches the highest levels during the immediate early phase of the immune response and the activation of Th17 cells precedes the Th1 cell differentiation we tent to speculate that this particular Th cell subset may represent a first line effector Th cell subpopulation. Interference with the activation of this Th cell subtype provides an interesting strategy to prevent autoimmunity as well as to establish protective immunity against infections.

Comparative analysis of transcriptional profiling of CD3+, CD4+ and CD8+ T cells identifies novel immune response players in T-cell activation

Background

T-cell activation is an essential step of the immune response and relies on the tightly controlled orchestration of hundreds of genes/proteins, yet the cellular and molecular events underlying this complex process are not fully understood, especially at the genome-scale. Significantly, a comparative genome-scale transcriptional analysis of two T-cell subsets (CD4+ and CD8+) against each other and against the naturally mixed population (CD3+ cells) remains unexplored.

Results

Comparison of the microarray-based gene expression patterns between CD3+ T cells, and the CD4+ and CD8+ subsets revealed largely conserved, but not identical, transcriptional patterns. We employed a Gene-Ontology-driven transcriptional analysis coupled with protein abundance assays in order to identify novel T-cell activation genes and cell-type-specific genes associated with the immune response. We identified potential genes involved in the communication between the two subsets (including IL23A, NR4A2, CD83, PSMB2, -8, MIF, IFI16, TNFAIP1, POU2AF1, and OTUB1) and would-be effector-function-specific genes (XCL2, SLAMF7, TNFSF4, -5, -9, CSF3, CD48 and CD244). Chemokines induced during T-cell activation, but not previously identified in T cells, include CCL20, CXCL9, -10, -11 (in all three populations), and XCL2 (preferentially in CD8+ T cells). Increased expression of other unexpected cytokines (GPI, OSM and MIF) suggests their involvement in T-cell activation with their functions yet to be examined. Differential expression of many receptors, not previously reported in the context of T-cell activation, including CCR5, CCR7, IL1R2, IL1RAP, IL6R, TNFRSF25 and TNFRSF1A, suggests their role in this immune process. Several receptors involved in TCR activation (CD3D, CD3G, TRAT1, ITGAL, ITGB1, ITGB2, CD8A and B (CD8+ T-cell specific) along with LCK, ZAP70 and TYROBP were synchronously downregulated. Members of cell-surface receptors (HLA-Ds and KLRs), none previously identified in the context of T-cell activation, were also downregulated.

Conclusion

This comparative genome-scale, transcriptional analysis of T-cell activation in the CD4+ and CD8+ subsets and the mixed CD3+ populations made possible the identification of many immune-response genes not previously identified in the context of T-cell activation. Significantly, it made possible to identify the temporal patterns of many previously known T-cell activation genes, and also identify genes implicated in effector functions of and communication between CD4+ and CD8+ T cells.

Activated renal macrophages are markers of disease onset and disease remission in lupus nephritis

Costimulatory blockade with CTLA4Ig and anti-CD40L along with a single dose of cyclophosphamide induces remission of systemic lupus erythematosus nephritis in NZB/W F(1) mice. To understand the mechanisms for remission and for impending relapse, we examined the expression profiles of 61 inflammatory molecules in the perfused kidneys of treated mice and untreated mice at different stages of disease. Further studies using flow cytometry and immunohistochemistry allowed us to determine the cellular origins of several key markers. We show that only a limited set of inflammatory mediators is expressed in the kidney following glomerular immune complex deposition but before the onset of proteinuria. Formation of a lymphoid aggregate in the renal pelvis precedes the invasion of the kidney by inflammatory cells. Regulatory molecules are expressed early in the disease process and during remission but do not prevent the inevitable progression of active inflammation. Onset of proliferative glomerulonephritis and proteinuria is associated with activation of the renal endothelium, expression of chemokines that mediate glomerular cell infiltration, and infiltration by activated dendritic cells and macrophages that migrate to different topographical areas of the kidney but express a similar profile of inflammatory cytokines. Increasing interstitial infiltration by macrophages and progressive tubular damage, manifested by production of lipocalin-2, occur later in the disease process. Studies of treated mice identify a type II (M2b)-activated macrophage as a marker of remission induction and impending relapse and suggest that therapy for systemic lupus erythematosus nephritis should include strategies that prevent both activation of monocytes and their migration to the kidney.

Helicobacter pylori induces CCL20 expression

CCL20 attracts immature dendritic cells and memory T cells and plays a role on mucosal surfaces in inflammation. However, whether Helicobacter pylori infection induces CCL20 in human gastric epithelial cells remains to be determined. The aim of this study was to analyze the molecular mechanism of H. pylori-induced CCL20 expression. Expression of CCL20 mRNA was assessed by reverse transcription-PCR. Five normal and five H. pylori-infected gastric tissue samples were stained immunohistochemically for CCL20. A luciferase assay was used to monitor activation of the CCL20 gene promoter, and an electrophoretic mobility shift assay was used to explore the binding of transcription factors to this promoter. The CCL20 expression in epithelial cells of H. pylori-positive tissues was higher than that in H. pylori-negative tissues. H. pylori induced CCL20 expression in gastric epithelial cell lines, and the induction was dependent on an intact cag pathogenicity island. Activation of the CCL20 promoter by H. pylori occurred through the action of NF-kappaB. Transfection of IkappaB kinase and NF-kappaB-inducing kinase dominant negative mutants inhibited H. pylori-mediated activation of CCL20. Treatment with an inhibitor of Hsp90 suppressed H. pylori-induced CCL20 mRNA due to deactivation of NF-kappaB. Collectively, these results suggest that H. pylori activates NF-kappaB through an intracellular signaling pathway that involves IkappaB kinase and NF-kappaB-inducing kinase, leading to CCL20 gene transcription, and that Hsp90 is a crucial regulator of H. pylori-induced CCL20 expression, presumably contributing to the immune response in H. pylori.

Expression of the chemokine receptor CCR6 in the Lewis lung carcinoma (LLC) cell line reduces its metastatic potential in vivo

Chemokines and their receptors play important roles in various aspects of tumoral processes, and evidence was provided for their critical involvement in determining the metastatic destination of tumor cells. Here, we analyzed in vitro and in vivo, how CCR6 expression could alter the behavior of Lewis lung carcinoma (LLC) cells, which were shown to express low levels of the CCR6 ligand, CCL20 (LARC), both in vitro and in vivo. The expression of CCR6 significantly decreased the number of metastases in immunocompetent C57BL/6 mice, without affecting the tumor-forming ability of LLC cells. This was correlated with a decrease in clonogenicity in soft and hard agar, and with increased adhesion to type-IV collagen. These two observations made in basal conditions were enhanced when CCL20 was added to the assay medium. Thus, expression of CCR6 in tumor cells, associated with the local production of CCL20, decreased the metastatic potential of the LLC line. We propose a model, in which the expression of a chemokine receptor in tumor cells can act as a metastasis-suppressor, or a metastasis-promoting factor, according to the expression, or the absence of expression of the cognate ligand(s) in the tumor.

MIP-3alpha neutralizing monoclonal antibody protects against TNBS-induced colonic injury and inflammation in mice

A characteristic feature of human inflammatory bowel disease, particularly Crohn's disease, is the presence of activated CD4(+) T cells. Recently, we have shown that colonic epithelial cell production of macrophage inflammatory protein (MIP)-3alpha, a CD4 T cell-directed chemokine, is elevated in inflammatory bowel disease. However, the functional relevance of MIP-3alpha production during intestinal inflammation is poorly understood. The aim of this study was to determine whether MIP-3alpha production is increased during murine 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis and to examine the effect of anti-MIP-3alpha neutralizing monoclonal antibody administration in this model. We found that the administration of TNBS significantly increased colonic MIP-3alpha protein levels in Balb/c mice. Consistent with this, a marked increase in the number of CCR6-bearing lamina propria CD4(+) and CD8(+) T cells was also observed in TNBS-treated animals. Treatment of mice with an anti-MIP-3alpha neutralizing monoclonal antibody significantly reduced TNBS-mediated increases in colonic weight-to-length ratio, mucosal ulceration, histological damage, and myeloperoxidase activity. TNBS-mediated increases in the number of CCR6-bearing lamina propria T cells were also substantially reduced by anti-MIP-3alpha neutralizing monoclonal antibody treatment. Taken together, our findings indicate that blockade of MIP-3alpha bioactivity can significantly reduce TNBS-mediated colonic injury and T cell recruitment, suggesting a role for this chemokine in the pathophysiology of intestinal inflammation.

The role of CC chemokine receptor 6 in host defense in a model of invasive pulmonary aspergillosis

RATIONALE

Invasive aspergillosis is a severe fungal infection afflicting immunocompromised patients, particularly patients with neutrophil defects. CCR6, a beta-chemokine receptor, mediates migration of dendritic cells (DCs) and several lymphocyte subsets to sites of epithelial inflammation, but its role in infections has not been examined extensively.

OBJECTIVES

To test the hypothesis that CCR6-mediated leukocyte recruitment is necessary for effective host defense in neutropenic hosts with invasive pulmonary aspergillosis.

METHODS

Neutropenic wild-type mice and mice with targeted deletion of CCR6 were infected with Aspergillus fumigatus. The host responses to the infection were compared in vivo and leukocyte responses to the fungus were examined in vitro.

MEASUREMENTS AND MAIN RESULTS

In the context of infection, immature myeloid DCs were the major population of CCR6-expressing cells in the lungs. As compared with wild-type animals, CCR6-deficient mice developed a more severe infection when challenged with A. fumigatus conidia, as documented by a higher mortality rate and greater lung fungal burden. This was associated with reduced accumulation of DCs in the lungs. CCR6-deficient and wild-type DCs did not differ in their phagocytosis of conidia, cytokine response, or maturation in vitro. In adoptive transfer experiments, however, DCs from CCR6-deficient donors showed lesser accumulation in the lungs of infected mice as compared with wild-type cells, and transfer of wild-type, but not CCR6-deficient, DCs resulted in attenuated severity of infection in CCR6-deficient recipients.

CONCLUSIONS

Taken together, these results implicate CCR6-mediated DC influx into the lung in the initial host defense in invasive aspergillosis.

Protective immunity and delayed type hypersensitivity reaction are uncoupled in experimental Leishmania major infection of CCR6-negative mice

The chemokine receptor CCR6 is expressed on naïve B cells, dendritic cell and T-cell subpopulations and is involved in cell navigation during organogenesis and recruitment in response to inflammatory stimuli. Gene-deficient C57BL/6 CCR6(-/-) mice infected with the protozoan parasite Leishmania (L.) major were able to mount a protective immune response and survived the infection. Whereas macrophage production of nitric oxide (NO), the key leishmanicidal effector molecule during the immune response to L. major, did not require CCR6, the migration of CD4(+) T cells to the site of infection was reduced in CCR6(-/-) mice. Furthermore, the induction of a T-cell-dependent delayed-type-hypersensitivity (DTH) reaction was defective in CCR6(-/-) mice, whereas resistance to re-infection was maintained in the absence of CCR6. We conclude that CCR6 contributes to the recruitment of T cells to the site of infection, but is largely dispensable for the control of L. major parasites during primary or secondary infection.

Oncostatin M Enhances CCL21 Expression by Microvascular Endothelial Cells and Increases the Efficiency of Dendritic Cell Trafficking to Lymph Nodes

CCL21, a lymphatic endothelial cell (LEC)-derived chemokine, and its receptor CCR7 regulate dendritic cell (DC) trafficking to lymph nodes (LN), but it is unclear how CCL21 expression is regulated. Oncostatin M (OSM) is an IL-6-like cytokine synthesized by activated DC and other leukocytes. In vitro, OSM (but not TNF-alpha) stimulated CCL21 mRNA and protein expression by human dermal microvascular EC (DMEC) in an ERK1/2-dependent fashion. Conditioned medium from OSM-treated DMEC stimulated CCL21-dependent chemotaxis of mouse bone marrow-derived DC (BMDC). Cultured BMDC expressed OSM, which was increased with the addition of LPS. Topical application of the contact-sensitizing hapten, trinitrochlorobenzene, resulted in enhanced OSM expression in the skin, whereas cutaneous injection of TNF-alpha did not. Injection of OSM into the footpad increased CCL21 mRNA expression in the draining LN by approximately 10-fold and in mouse skin by approximately 4-fold without increasing CCR7 mRNA. In vitro, OSM increased the permeability of DMEC and lung microvascular EC monolayers to FITC-dextran beads, and, in vivo, it enhanced accumulation of Evans blue dye in draining LN by approximately 3-fold (p = 0.0291). Of note, OSM increased trafficking of BMDC injected in footpads to draining LN by 2-fold (p = 0.016). In summary, OSM up-regulates CCL21 expression in skin and draining regional LN. We propose that OSM is a regulator of CCL21 expression and endothelial permeability in skin, contributing to efficient migration of DC to regional LN.

Intralymphatic dendritic cell vaccination induces tumor antigen-specific, skin-homing T lymphocytes

PURPOSE

The identification of tumor antigens recognized by cytotoxic and T helper lymphocytes has led to the development of specific cancer vaccines. Immunization with tumor antigen-pulsed dendritic cells has proved effective at eliciting elevated levels of tumor antigen-specific T cells in patient blood, but objective clinical responses remain rare, suggesting that vaccine-induced T cells are not trafficking optimally to site(s) of tumor burden. Accumulating evidence from animal models suggests that route of immunization can have a substantial influence on the subsequent migration of primed, activated T cells in vivo.

EXPERIMENTAL DESIGN

In a clinical trial designed to elicit more effective cytotoxic T-cell mediated antitumor responses, metastatic melanoma patients were immunized directly via a peripheral intralymphatic route with autologous dendritic cells pulsed with HLA-A*0201-restricted melanoma-associated peptide antigens derived from MART-1 and gp100.

RESULTS

Within 10 days of intralymphatic dendritic cell vaccination, four of six patients developed dramatic and diffuse erythematous rashes in sun-exposed areas of skin that showed extensive T-cell infiltration. CTLs grown from rash biopsies were strongly enriched for tumor antigen-specific T cells that had elevated expression of cutaneous lymphocyte antigen and chemokine receptor-6, consistent with a skin-homing phenotype. Of note, the only patient in the study with cutaneously localized disease showed a significant regression of metastatic lesions following the development of a surrounding rash.

CONCLUSIONS

The evidence presented here is consistent with immunization studies in animal models and supports the concept that T cells are "imprinted" in peripheral lymph node sites to express specific ligands and chemokine receptors that allow them to migrate to skin. Furthermore, the preferential migration of the T cells to sun-exposed cutaneous sites suggests that inflammation plays a critical role in this migration. These observations suggest that further study of the effects of immunization route and inflammation on T-cell migration in humans is warranted, and could lead to vaccination approaches that would more reliably direct trafficking of activated T cells to diverse sites of metastatic disease.

The Majority of Human Peripheral Blood CD4+CD25highFoxp3+ Regulatory T Cells Bear Functional Skin-Homing Receptors

CD4+CD25+ T regulatory cells (Treg) are thought to be important in the peripheral tolerance. Recent evidence suggests that human peripheral blood CD4+CD25+ T cells are heterogeneous and contain both CD4+CD25(high) T cells with potent regulatory activity and many more CD4+CD25(low/med) nonregulatory T cells. In this study, we found that virtually all peripheral blood CD4+CD25(high)Foxp3+ Treg expressed high levels of the chemokine receptor CCR4. In addition, 80% of Treg expressed cutaneous lymphocyte Ag (CLA) and 73% expressed CCR6. These molecules were functional, as CLA+ Treg showed CD62E ligand activity and demonstrable chemotactic responses to the CCR4 ligands CCL22 and CCL17 and to the CCR6 ligand CCL20. The phenotype and chemotactic response of these Treg were significantly different from those of CD4+CD25(med) nonregulatory T cells. We further demonstrated that blood CLA+ Treg inhibited CD4+CD25- T cell proliferation induced by anti-CD3. Based on homing receptor profile, CLA+ Treg should enter normal skin. We next isolated CD4+CD25(high) T cells directly from normal human skin; these cells suppressed proliferation of skin CD4+CD25- T cells. Therefore, the majority of true circulating Treg express functional skin-homing receptors, and human Treg may regulate local immune responses in normal human skin.

The impact of memory T cells on rejection and the induction of tolerance

Accumulating evidence suggests that alloreactive memory T cells (Tm) may be generated in transplant recipients that have not previously been exposed to alloantigen through mechanisms such as cross-reactivity and homeostatic proliferation. The presence of Tm correlates with both acute and chronic rejection episodes and, furthermore, may be responsible for the failure to induce tolerance in large animal and clinical settings. A clearer understanding of how Tm function and their requirements to mount an effective response to alloantigen will be key to further attempts to translate tolerance induction protocols from the experimental setting to the clinic.

Effect of oestradiol on PAMP-mediated CCL20/MIP-3 alpha production by mouse uterine epithelial cells in culture

The present study was undertaken to establish whether mouse uterine epithelial cells produce CCL20/macrophage inflammatory protein 3 alpha (CCL20/MIP-3 alpha) and to determine whether secretion is under hormonal control and influenced by pathogen-associated molecular patterns (PAMPs). In the absence of PAMPs, polarized uterine epithelial cells grown to confluence on cell culture inserts constitutively secreted CCL20/MIP-3 alpha with preferential accumulation into the apical compartment. When epithelial cells were treated with the Toll-like receptor (TLR) agonists Pam3Cys (TLR2/1), peptidoglycan (TLR2/6) or lipopolysaccharide (LPS; TLR4), CCL20/MIP-3 alpha increased rapidly (4 hr) in both apical and basolateral secretions. Time-course studies indicated that responses to PAMPs added to the apical surface persisted for 12-72 hr. Stimulation with loxoribin (TLR7) and DNA CpG motif (TLR9) increased basolateral but not apical secretion of CCL20/MIP-3 alpha. In contrast, the viral agonist Poly(I:C) (TLR3) had no effect on either apical or basolateral secretion. In other studies, we found that oestradiol added to the culture media decreased the constitutive release of CCL20/MIP-3 alpha. Moreover, when added to the culture media along with LPS, oestradiol inhibited LPS-induced increases in CCL20/MIP-3 alpha secretion into both the apical and basolateral compartments. In summary, these results indicate that CCL20/MIP-3 alpha is produced in response to PAMPs. Since CCL20/MIP-3 alpha is chemotactic for immature dendritic cells, B cells and memory T cells and has antimicrobial properties, these studies suggest that CCL20/MIP-3 alpha production by epithelial cells, an important part of the innate immune defence in the female reproductive tract, is under hormonal control and is responsive to microbial challenge.

A Chronic Contact Eczema Impedes Migration of Antigen-Presenting Cells in Alopecia Areata

Long-lasting allergen treatment is the most efficient therapy in alopecia areata (AA). The underlying mechanism is unknown. We here asked whether treatment with a contact sensitizer influences leukocyte migration such that dendritic cell (DC) migration or the recruitment of activated T-cells towards the skin become hampered. Allergen treatment of AA mice was not accompanied by a decrease in skin-infiltrating leukocytes or draining lymph node cells (LNC). However, the distribution of leukocyte subsets was changed with a dominance of monocytes in the skin and a reduced percentage of DCs in draining nodes. Chemokine and chemokine receptor expression in skin and draining nodes was strikingly increased and LNC from untreated and allergen-treated AA mice showed high migratory activity in vitro and readily homed in draining nodes and skin after intravenous injection. However, FITC labelling of the skin and subcutaneous transfer of dye-labelled DC revealed that allergen treatment created a chemokine milieu severely hampering DC migration from the skin towards the draining node. An allergic eczema-induced reduction in DC migration and antigen transfer could well contribute to insufficient T-cell activation and the recovery of hair follicle in AA and possibly be of relevance for other skin-related autoimmune diseases.

A Novel Method for the Isolation of Skin Resident T Cells from Normal and Diseased Human Skin

T cells resident in normal skin likely conduct immunosurveillance and are implicated in the development of inflammatory disorders such as psoriasis. This population of cells is difficult to study because existing techniques allow isolation of only few cells. We report here a novel method of isolating T cells from both normal and diseased human skin. Explants of skin cultured on three-dimensional matrices led to the outgrowth of dermal fibroblasts that elaborated T cell chemoattractant factors. These factors led to the migration of skin resident T cells out of skin explants where they could be collected and studied. Skin resident T cells isolated from explant cultures were CD45RO(+) memory T cells and expressed high levels of cutaneous lymphocyte antigen (CLA) and chemokine receptor (CCR)4. Inclusion of IL-2 and IL-15 in explant cultures produced up to a 10-fold expansion of skin-resident T cells, while maintaining the CLA(+)CCR4(+) skin-homing phenotype as well as a diverse T cell repertoire. This method also allowed efficient isolation of malignant T cells from the skin lesions of cutaneous T cell lymphoma and the isolation of tumor-infiltrating lymphocytes from primary squamous cell carcinomas and melanoma metastases.

Homing and function of human skin gammadelta T cells and NK cells: relevance for tumor surveillance

Normal (noninflamed) human skin contains a network of lymphocytes, but little is known about the homing and function of these cells. The majority of alphabeta T cells in normal skin express CCR8 and produce proinflammatory cytokines. In this study we examined other subsets of cutaneous lymphocytes, focusing on those with potential function in purging healthy tissue of transformed and stressed cells. Human dermal cell suspensions contained significant populations of Vdelta1(+) gammadelta T cells and CD56(+)CD16(-) NK cells, but lacked the subsets of Vdelta2(+) gammadelta T cells and CD56(+)CD16(+) NK cells, which predominate in peripheral blood. The skin-homing receptors CCR8 and CLA were expressed by a large fraction of both cell types, whereas chemokine receptors associated with lymphocyte migration to inflamed skin were absent. Neither cell type expressed CCR7, although gammadelta T cells up-regulated this lymph node-homing receptor upon TCR triggering. Stimulation of cutaneous Vdelta1(+) gammadelta T cell lines induced secretion of large amounts of TNF-alpha, IFN-gamma, and the CCR8 ligand CCL1. In contrast to cutaneous alphabeta T cells, both cell types had the capacity to produce intracellular perforin and displayed strong cytotoxic activity against melanoma cells. We therefore propose that gammadelta T cells and NK cells are regular constituents of normal human skin with potential function in the clearance of tumor and otherwise stressed tissue cells.