Chemokine receptor expressions and responsiveness of cord blood T cells

Perinatal Inflammation: Could Partial Blocking of Cell Adhesion Molecule Function Be a Solution?

In spite of the great advances made in recent years in prenatal and perinatal medicine, inflammation can still frequently result in injury to vital organs and often constitutes a major cause of morbidity. It is today well established that in neonates—though vulnerability to infection among neonates is triggered by functional impairments in leukocyte adhesion—the decreased expression of cell adhesion molecules also decreases the inflammatory response. It is also clear that the cell adhesion molecules, namely, the integrins, selectins, and the immunoglobulin (Ig) gene super family, all play a crucial role in the inflammatory cascade. Thus, by consolidating our knowledge concerning the actions of these vital cell adhesion molecules during the prenatal period as well as regarding the genetic deficiencies of these molecules, notably leukocyte adhesion deficiency (LAD) I, II, and III, which can provoke severe clinical symptoms throughout the first year of life, it is anticipated that intervention involving blocking the function of cell adhesion molecules in neonatal leukocytes has the potential to constitute an effective therapeutic approach for inflammation. A promising perspective is the potential use of antibody therapy in preterm and term infants with perinatal inflammation and infection focusing on cases in which LAD is involved, while a further important scientific advance related to this issue could be the combination of small peptides aimed at the inhibition of cellular adhesion.

Vaccine-Induced CD8+ T Cell Responses in Children: A Review of Age-Specific Molecular Determinants Contributing to Antigen Cross-Presentation

Infections are most common and most severe at the extremes of age, the young and the elderly. Vaccination can be a key approach to enhance immunogenicity and protection against pathogens in these vulnerable populations, who have a functionally distinct immune system compared to other age groups. More than 50% of the vaccine market is for pediatric use, yet to date vaccine development is often empiric and not tailored to molecular distinctions in innate and adaptive immune activation in early life. With modern vaccine development shifting from whole-cell based vaccines to subunit vaccines also comes the need for formulations that can elicit a CD8⁺ T cell response when needed, for example, by promoting antigen cross-presentation. While our group and others have identified many cellular and molecular determinants of successful activation of antigen-presenting cells, B cells and CD4⁺ T cells in early life, much less is known about the ontogeny of CD8⁺ T cell induction. In this review, we summarize the literature pertaining to the frequency and phenotype of newborn and infant CD8⁺ T cells, and any evidence of induction of CD8⁺ T cells by currently licensed pediatric vaccine formulations. In addition, we review the molecular determinants of antigen cross-presentation on MHC I and successful CD8⁺ T cell induction and discuss potential distinctions that can be made in children. Finally, we discuss recent advances in development of novel adjuvants and provide future directions for basic and translational research in this area.

CCL20 is elevated during obesity and differentially regulated by NF-κB subunits in pancreatic β-cells

Enhanced leukocytic infiltration into pancreatic islets contributes to inflammation-based diminutions in functional β-cell mass. Insulitis (aka islet inflammation), which can be present in both T1DM and T2DM, is one factor influencing pancreatic β-cell death and dysfunction. IL-1β, an inflammatory mediator in both T1DM and T2DM, acutely (within 1h) induced expression of the CCL20 gene in rat and human islets and clonal β-cell lines. Transcriptional induction of CCL20 required the p65 subunit of NF-κB to replace the p50 subunit at two functional κB sites within the CCL20 proximal gene promoter. The NF-κB p50 subunit prevents CCL20 gene expression during unstimulated conditions and overexpression of p50 reduces CCL20, but enhances cyclooxygenase-2 (COX-2), transcript accumulation after exposure to IL-1β. We also identified differential recruitment of specific co-activator molecules to the CCL20 gene promoter, when compared with the CCL2 and COX2 genes, revealing distinct transcriptional requirements for individual NF-κB responsive genes. Moreover, IL-1β, TNF-α and IFN-γ individually increased the expression of CCR6, the receptor for CCL20, on the surface of human neutrophils. We further found that the chemokine CCL20 is elevated in serum from both genetically obese db/db mice and in C57BL6/J mice fed a high-fat diet. Taken together, these results are consistent with a possible activation of the CCL20-CCR6 axis in diseases with inflammatory components. Thus, interfering with this signaling pathway, either at the level of NF-κB-mediated chemokine production, or downstream receptor activation, could be a potential therapeutic target to offset inflammation-associated tissue dysfunction in obesity and diabetes.

Epigenetic modification of the human CCR6 gene is associated with stable CCR6 expression in T cells

CCR6 is a chemokine receptor expressed on Th17 cells and regulatory T cells that is induced by T-cell priming with certain cytokines, but how its expression and stability are regulated at the molecular level is largely unknown. Here, we identified and characterized a noncoding region of the human CCR6 locus that displayed unmethylated CpG motifs (differentially methylated region [DMR]) selectively in CCR6(+) lymphocytes. CCR6 expression on circulating CD4(+) T cells was stable on cytokine-induced proliferation but partially down-regulated on T-cell receptor stimulation. However, CCR6 down-regulation was mostly transient, and the DMR within the CCR6 locus remained demethylated. Notably, in vitro induction of CCR6 expression with cytokines in T-cell receptor-activated naive CD4(+) T cells was not associated with a demethylated DMR and resulted in unstable CCR6 expression. Conversely, treatment with the DNA methylation inhibitor 5'-azacytidine induced demethylation of the DMR and led to increased and stable CCR6 expression. Finally, when cloned into a reporter gene plasmid, the DMR displayed transcriptional activity in memory T cells that was suppressed by DNA methylation. In summary, we have identified a noncoding region of the human CCR6 gene with methylation-sensitive transcriptional activity in CCR6(+) T cells that controls stable CCR6 expression via epigenetic mechanisms.

Mannan-binding lectin regulates dendritic cell maturation and cytokine production induced by lipopolysaccharide

Background

Mannan-binding lectin (MBL) is a pattern-recognition molecule present in serum, which is involved in the innate immune defense by activating complement and promoting opsonophagocytosis. Dendritic cells (DCs) are professional antigen presenting cells (APCs) that are crucial for the initiation of adaptive immunity. Lipopolysaccharide (LPS) has been shown to be a strong activator of the inflammatory response and immune regulation. We first examined whether MBL modulated LPS-induced cellular responses, then investigated possible mechanisms of its inhibitory effect.

Results

MBL at higher concentrations (10-20 μg/ml) significantly attenuated LPS-induced maturation of monocyte-derived DCs (MDCs) and production of proinflammatory cytokines (e.g., IL-12 and TNF-α), and inhibited their ability to activate allogeneic T lymphocytes. It bound to immature MDCs at physiological calcium concentrations, and was optimal at supraphysiological calcium concentrations. MBL also bound directly to immature MDCs and attenuated the binding of LPS to the cell surfaces, resulting in decreased LPS-induced nuclear factor-κB (NF-κB) activity in these cells.

Conclusion

All these data suggest that MBL could affect the functions of DCs by modifying LPS-induced cellular responses. This study supports an important role for MBL in the regulation of adaptive immune responses and inflammatory responses.

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.

Elevated CCR6+ CD4+ T lymphocytes in tissue compared with blood and induction of CCL20 during the asthmatic late response

CCR6 is expressed by multiple leucocyte subsets, including peripheral blood memory T cells, and mouse models implicate a role for this receptor in diverse inflammatory responses that include allergic airway disorders, inflammatory bowel disease and autoimmune encephalitis. In order to study the role of CCR6 in humans, we have investigated the patterns of CCR6 expression and function on T cells from the peripheral blood, skin, nose and lung, in health and in allergic disease. Results show that CCR6 was expressed consistently on a higher proportion of tissue versus peripheral blood-derived CD4+ T cells (P < 0.01). CCR6 was expressed predominantly on CD4+ compared with CD8+ cells in both blood- and tissue-derived T cells (P < 0.001). The number of cells showing CCR6 expression was not proportionally greater in peripheral blood or nasal mucosal T cells of subjects with symptomatic allergic rhinitis. CCR6+ cells demonstrated enhanced functional responses to CCL20 and CCL20 was increased in bronchoalveolar lavage fluid of asthmatics following endobronchial allergen provocation (P < 0.05). Thus, CCR6 may be important in the regulation of T cell recruitment to tissue and up-regulation of CCL20 expression may contribute to the recruitment and/or retention of effector T cells in allergic asthma.

Exodus-1 (CCL20): evidence for the participation of this chemokine in spontaneous labor at term, preterm labor, and intrauterine infection

AIM

CCL20, also known as MIP-3 alpha, is a chemokine that participates in chemotaxis of immature dendritic cells, effector/memory T-cells, and B-lymphocytes. The objectives of this study were to determine whether CCL20 can be detected in amniotic fluid (AF) and if AF concentration of this chemokine changes with advancing gestational age, parturition (term and preterm), and intra-amniotic infection/inflammation (IAI).

METHODS

A cross-sectional study was conducted including the following groups: (1) mid-trimester of pregnancy (n=65); (2) term not in labor (TNL; n=22); (3) term in labor (TIL; n=47); (4) spontaneous preterm labor (PTL) who delivered at term (n=57); (5) spontaneous PTL without IAI who delivered preterm (n=71); and (6) spontaneous PTL with IAI (n=38). AF CCL20 concentrations were determined using ELISA.

RESULTS

(1) The median AF CCL20 concentration in TNL was higher than that of mid-trimester patients; (2) Women in spontaneous labor at term had a higher median AF concentration of CCL20 than patients at term not in labor; (3) Patients with spontaneous PTL and IAI had a significantly higher median AF concentration of CCL20 than those without IAI who delivered preterm and those who delivered at term. Moreover, women with spontaneous PTL without IAI who delivered preterm had a significantly higher median AF concentration than those with PTL who subsequently delivered at term.

CONCLUSIONS

(1) CCL20 is a physiologic constituent of AF and its concentration increases as term approaches; (2) spontaneous labor (term and preterm) in the absence of IAI is associated with increased bioavailability of AF CCL20 suggesting that an increase in CCL20 is part of the common pathway of human parturition; (3) patients with IAI had dramatic elevations in the AF CCL20 concentrations suggesting that this chemokine participates in the host response to infection or other stimuli associated with intra-amniotic infection.

Trapping and apoptosis of novel subsets of memory T lymphocytes expressing CCR6 in the spleen of HIV-infected patients

CCR6, a homeostatic chemokine receptor, is shown here to characterize subsets of both central and effector memory T cells that secrete high levels of IL-2 and TNF-alpha in response to polyclonal and antigen-specific stimulation. CCR6(+) T lymphocytes disappeared dramatically from the peripheral blood of HIV-infected patients as HIV disease progressed. The capacity of CD4(+)CCR6(+) to secrete multiple cytokines remained intact among HIV-infected long-term nonprogressors but was partially lost from subjects with standard disease progression. CCR6(+) T lymphocytes, regardless of their CCR7 expression, accumulated in the spleen of HIV-infected patients, where they died by apoptosis. Assessment of CCR6 expression allowed us to describe novel memory T-cell subpopulations capable of high cytokine production and provided evidence of a pathologic CCR6-dependent pathway of memory T-cell homing that may participate in the loss of memory response against infections.

Pediatric cancers are infiltrated predominantly by macrophages and contain a paucity of dendritic cells: a major nosologic difference with adult tumors

PURPOSE

Adult cancer is frequently preceded by a period of prolonged chronic inflammation caused by infectious microbial agents or physical or chemical irritants. By contrast, an association between the classic pediatric neoplasias and inflammatory triggers is only rarely recognized. We hypothesized that the difference could be reflected in the inflammatory cell infiltrates of pediatric and adult cancer.

EXPERIMENTAL DESIGN

Three investigators retrospectively studied 27 pediatric and 13 adult cancers at first diagnosis by immunohistochemistry. Inflammatory cells were identified and counted, and their location in relation to tumor tissue was analyzed.

RESULTS

A majority of tumor-associated leukocytes (TAL) in adult tumors were located at the edges of tumor islands forming inflammatory foci between the supporting stroma and the malignant infiltrate. In contrast, TALs in pediatric tumors were scattered within the malignant tumor islands. In adult tumors, TALs were composed of diverse leukocyte types; but in pediatric tumors, the infiltrating cells were predominantly macrophages that accumulated in areas of necrosis within the tumors. The most striking feature in the pediatric tumors was the virtual absence of dendritic cells. The proportion of intratumoral dendritic cells in pediatric samples was 4.1%; whereas in adult tumors, they formed 36.9% of TALs within the tumor islands and 25.1% around the tumors.

CONCLUSIONS

We conclude that TALs in pediatric cancers are composed mainly of macrophages and largely devoid of dendritic cell. The findings may provide a major nosologic difference reclassifying pediatric and adult tumors based on nominal inflammatory and noninflammatory etiologies.

Differentiation of naive cord-blood T cells into CD19-specific cytolytic effectors for posttransplantation adoptive immunotherapy

Disease relapse is a barrier to achieving therapeutic success after unrelated umbilical cord-blood transplantation (UCBT) for B-lineage acute lymphoblastic leukemia (B-ALL). While adoptive transfer of donor-derived tumor-specific T cells is a conceptually attractive approach to eliminating residual disease after allogeneic hematopoietic stem cell transplantation, adoptive immunotherapy after UCBT is constrained by the difficulty of generating antigen-specific T cells from functionally naive umbilical cord-blood (UCB)-derived T cells. Therefore, to generate T cells that recognize B-ALL, we have developed a chimeric immunoreceptor to redirect the specificity of T cells for CD19, a B-lineage antigen, and expressed this transgene in UCB-derived T cells. An ex vivo process, which is compliant with current good manufacturing practice for T-cell trials, has been developed to genetically modify and numerically expand UCB-derived T cells into CD19-specific effector cells. These are capable of CD19-restricted cytokine production and cytolysis in vitro, as well as mediating regression of CD19+ tumor and being selectively eliminated in vivo. Moreover, time-lapse microscopy of the genetically modified T-cell clones revealed an ability to lyse CD19+ tumor cells specifically and repetitively. These data provide the rationale for infusing UCB-derived CD19-specific T cells after UCBT to reduce the incidence of CD19+ B-ALL relapse.

Reduced expression of NFAT-associated genes in UCB versus adult CD4+ T lymphocytes during primary stimulation

The cellular and molecular mechanisms underlying the blunted allo-responsiveness of umbilical cord blood (UCB) T cells have not been fully elucidated. Protein expression of NFATc2 (nuclear factor of activated T cells c2), a critical transcription factor necessary for up-regulation of multiple cytokines known to amplify T-cell allogeneic responses, is reduced in UCB T cells. Affymetrix oligonucleotide microarrays were used to compare gene expression of primary purified CD4+ UCB T cells to adult peripheral blood CD4+ T cells (AB) at baseline, 6, and 16 hours of primary stimulation. NFAT-regulated genes exhibited lower expression in UCB CD4+ T cells including the following: granulocyte-macrophage colony-stimulating factor (GM-CSF), interferon-gamma (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha), interleukin 3 (IL-3), IL-4, IL-5, IL-13, IL-2 receptor alpha (IL-2Ralpha; CD25), CD40L, and macrophage inflammatory protein 1 alpha (MIP-1alpha). Transcription factors involved in the NFAT pathway including C/EBPbeta, JunB, and Fosl1 (Fra-1), as well as Th1- and Th2-related transcription factors STAT4 (signal transducers and activators of transcription 4), T-bet, and c-maf showed reduced expression in UCB compared with AB during primary stimulation. Reduced cytokine, chemokine, and receptor expression was also found in UCB. Gene array data were confirmed using RNase protection assays, flow cytometry, and quantitative multiplexed cytokine measurements. Reduced global expression of NFAT-associated genes, as well as cytokines and chemokines, in UCB CD4+ T cells may contribute to the decreased graft-versus-host disease (GVHD) observed after UCB transplantation.

The CC chemokine CCL20 and its receptor CCR6

CCL20, alternatively named liver and activation-regulated chemokine (LARC), macrophage inflammatory protein-3alpha (MIP-3alpha) or Exodus-1, is the only chemokine known to interact with CC chemokine receptor 6 (CCR6), a property shared with the antimicrobial beta-defensins. The ligand-receptor pair CCL20-CCR6 is responsible for the chemoattraction of immature dendritic cells (DC), effector/memory T-cells and B-cells and plays a role at skin and mucosal surfaces under homeostatic and inflammatory conditions, as well as in pathology, including cancer and rheumatoid arthritis. In this review, the discovery, the gene and protein structure, the in vitro biological activities, the cell and inducer specific expression and the tissue distribution of CCL20 and CCR6 are discussed.

Effect of diesel on chemokines and chemokine receptors involved in helper T cell type 1/type 2 recruitment in patients with asthma

The objective of this study was to evaluate if diesel exhausts could favor helper T cell type (Th) 2-associated allergic reactions either through an increased production of Th2-associated chemokines and of their associated receptors or through a decrease of Th1-attracting chemokines and chemokine receptors. Diesel but not allergen exposure of peripheral blood mononuclear cells from subjects with allergy induced a release of I-309, whereas both diesel and Der p 1 induced an early but transient release of monokine induced by IFN-gamma and a late release of pulmonary and activation-regulated chemokine. Although both Th1- and Th2-attracting chemokines were induced, the resulting effect was an increased chemotactic activity on Th2 but not Th1 cells. Surprisingly, diesel induced a late increase in the expression of the Th1-associated CXC receptor 3 and CC receptor 5. T cell CXC receptor 3 upregulation was not associated with an increased migration to its ligands. These two antagonistic effects have been previously reported as a scavenger mechanism to clear chemokines. Altogether, these results suggest that diesel, even without allergen, may amplify a type 2 immune response but that it can also increase late Th1-associated chemokine receptor expression, perhaps as a scavenger mechanism to clear pro-Th1 chemokines and promote the Th2 pathway.

An abortive ligand-induced activation of CCR1-mediated downstream signaling event and a deficiency of CCR5 expression are associated with the hyporesponsiveness of human naive CD4+ T cells to CCL3 and CCL5

Human memory CD4(+) T cells respond better to inflammatory CCLs/CC chemokines, CCL3 and CCL5, than naive CD4(+) T cells. We analyzed the regulatory mechanism underlying this difference. Memory and naive CD4(+) T cells expressed similarly high levels of CCR1; however, CCR5 was only expressed in memory CD4(+) T cells at low levels. Experiments using mAbs to block chemokine receptors revealed that CCR1 functioned as a major receptor for the binding of CCL5 in memory and naive CD4(+) T cells as well as the ligand-induced chemotaxis in memory CD4(+) T cells. Stimulation of memory CD4(+) T cells with CCL5 activated protein tyrosine kinase-dependent cascades, which were significantly blocked by anti-CCR1 mAb, whereas this stimulation failed to induce these events in naive CD4(+) T cells. Intracellular expressions of regulator of G protein signaling 3 and 4 were only detected in naive CD4(+) T cells. Pretreatment of cell membrane fractions from memory and naive CD4(+) T cells with GTP-gamma S inhibited CCL5 binding, indicating the involvement of G proteins in the interaction of CCL5 and its receptor(s). In contrast, CCL5 enhanced the GTP binding to G(i alpha) and G(q alpha) in memory CD4(+) T cells, but not in naive CD4(+) T cells. Thus, a failure of the ligand-induced activation of CCR1-mediated downstream signaling event as well as a deficiency of CCR5 expression may be involved in the hyporesponsiveness of naive CD4(+) T cells to CCL3 and CCL5.

Expression of cytokine- and chemokine-related genes in peripheral blood mononuclear cells from lupus patients by cDNA array

Systemic lupus erythematosus (SLE) is characterized by diverse and complex immune abnormalities. In an effort to begin to characterize the full complexity of immune abnormalities, the expression pattern of 375 potentially relevant genes was analyzed using peripheral blood mononuclear cells (PBMC) from 21 SLE patients and 12 controls by cDNA arrays. When mean gene expression for patients was compared to controls, 50 genes were identified that exhibited more than 2.5-fold difference in expression level. By the Mann-Whitney U test, 20 genes were significantly different (P < 0.05) between patients and controls. Most of these genes have not been previously associated with SLE and belong to a variety of families such as TNF/death receptor, IL-1 cytokine family, and IL-8 and its receptors. Hierarchical clustering of samples and differentially expressed genes revealed that with few exceptions, patients clustered separately from controls. These results highlight the potential use of the microarray data in identifying genes associated with SLE, which could become candidate molecular markers or future therapeutic targets.

Human peripheral blood monocyte-derived interleukin-10-induced semi-mature dendritic cells induce anergic CD4(+) and CD8(+) T cells via presentation of the internalized soluble antigen and cross-presentation of the phagocytosed necrotic cellular fragments

We examined the ability of human monocyte-derived interleukin (IL)-10-induced semi-mature dendritic cells (semi-mDCs) that had been pulsed with soluble protein and necrotic cellular fragments to induce an antigen (Ag)-specific anergy in CD4(+) and CD8(+) T cells. IL-10 converted normal immature DCs (iDCs) into semi-mDCs during the maturation. In contrast to normal iDCs and mature DCs, IL-10-induced semi-mDCs as well as IL-10-treated iDCs not only had reduced their allogeneic T cell-stimulatory capacity, but also induced an allogeneic Ag-specific anergy in T cells. Normal mDCs that had been pulsed with tetanus toxin (TT) or allogeneic necrotic cellular fragments caused further activation of TT-specific CD4(+) T cells or allogeneic fibroblast-specific CD8(+) T cells, Ag-pulsed IL-10-induced semi-mDCs induced an anergic state in both cell types. Thus, our results suggest that IL-10-induced semi-mDCs induce an Ag-specific anergy in CD4(+) and CD8(+) T cells via presentation of the internalized protein and cross-presentation of the phagocytosed cellular fragments.

Up-regulation of CCR5 and CCR6 on distinct subpopulations of antigen-activated CD4+ T lymphocytes

Following infection, naive T cells are activated in the secondary lymphoid tissue, but then need to move to the infected tissue in the periphery to mediate their effector functions. The acquisition of inflammatory chemokine receptors, such as CCR5 and CCR6, may contribute to the efficient relocation of activated T cells to inflamed sites in the periphery. In keeping with this idea, the present study has demonstrated that CCR5 and CCR6 are up-regulated on CD4+ T cells upon activation in the MLR. The observed increase in expression correlated well with the acquisition of an activated/memory phenotype and was largely (CCR5) or completely (CCR6) separated temporally from the initiation of cell division. In contrast, the regulation of two other chemokine receptors, CXCR3 and CXCR4, occurred in close parallel with the cell division process. Increased mRNA levels are likely to contribute to the enhanced surface expression of CCR5 and CCR6, but in the case of CCR6, translocation of intracellular stores of protein to the cell surface may be an additional mechanism of regulation. The up-regulation of CCR5 was more extensive than that of CCR6, as only approximately half the activated CCR5+ T cells coexpressed CCR6. The increased expression of CCR5 resulted in enhanced chemotaxis toward the CCR5 ligand macrophage-inflammatory protein-1beta/CCL4, but up-regulation of CCR6 did not result in altered chemotactic responsiveness to macrophage-inflammatory protein-3alpha/CCL20, suggesting an alternative function for this receptor.