Chemokines and dendritic cells: a crucial alliance

Chemokines: A key driver for inflammation in protozoan infection

Chemokines belong to the group of small proteins within the cytokine family having strong chemo-attractant properties. In most cases, the strong immuno-modulatory role of chemokines is crucial for generating the immune response against pathogens in various protozoan diseases. In this review, we have given a brief update on the classification, characterization, homeostasis, transcellular migration, and immuno-modulatory role of chemokines. Here we will evaluate the potential role of chemokines and their regulation in various protozoan diseases. There is a significant direct relationship between parasitic infection and the recruitment of effector cells of the immune response. Chemokines play an indispensable role in mediating several defense mechanisms against infection, such as leukocyte recruitment and the generation of innate and cell-mediated immunity that aids in controlling/eliminating the pathogen. This process is controlled by the chemotactic movement of chemokines induced as a primary host immune response. We have also addressed that chemokine expressions during infection are time-dependent and orchestrated in a systematic pattern that ultimately assists in generating a protective immune response. Taken together, this review provides a systematic understanding of the complexity of chemokines profiles during protozoan disease conditions and the rationale of targeting chemokines for the development of therapeutic strategies.

Tumor eradication by hetIL-15 locoregional therapy correlates with an induced intratumoral CD103intCD11b+ dendritic cell population

Locoregional monotherapy with heterodimeric interleukin (IL)-15 (hetIL-15) in a triple-negative breast cancer (TNBC) orthotopic mouse model resulted in tumor eradication in 40% of treated mice, reduction of metastasis, and induction of immunological memory against breast cancer cells. hetIL-15 re-shaped the tumor microenvironment by promoting the intratumoral accumulation of cytotoxic lymphocytes, conventional type 1 dendritic cells (cDC1s), and a dendritic cell (DC) population expressing both CD103 and CD11b markers. These CD103intCD11b+DCs share phenotypic and gene expression characteristics with both cDC1s and cDC2s, have transcriptomic profiles more similar to monocyte-derived DCs (moDCs), and correlate with tumor regression. Therefore, hetIL-15, a cytokine directly affecting lymphocytes and inducing cytotoxic cells, also has an indirect rapid and significant effect on the recruitment of myeloid cells, initiating a cascade for tumor elimination through innate and adoptive immune mechanisms. The intratumoral CD103intCD11b+DC population induced by hetIL-15 may be targeted for the development of additional cancer immunotherapy approaches.

The mechanobiology of NK cells- 'Forcing NK to Sense' target cells

Natural killer (NK) cells are innate immune lymphocytes that recognize and kill cancer and infected cells, which makes them unique 'off-the-shelf' candidates for a new generation of immunotherapies. Biomechanical forces in homeostasis and pathophysiology accrue additional immune regulation for NK immune responses. Indeed, cellular and tissue biomechanics impact NK receptor clustering, cytoskeleton remodeling, NK transmigration through endothelial cells, nuclear mechanics, and even NK-dendritic cell interaction, offering a plethora of unexplored yet important dynamic regulation for NK immunotherapy. Such events are made more complex by the heterogeneity of human NK cells. A significant question remains on whether and how biochemical and biomechanical cues collaborate for NK cell mechanotransduction, a process whereby mechanical force is sensed, transduced, and translated to downstream mechanical and biochemical signalling. Herein, we review recent advances in understanding how NK cells perceive and mechanotransduce biophysical cues. We focus on how the cellular cytoskeleton crosstalk regulates NK cell function while bearing in mind the heterogeneity of NK cells, the direct and indirect mechanical cues for NK anti-tumor activity, and finally, engineering advances that are of translational relevance to NK cell biology at the systems level.

Host responses against the fish parasitizing ciliate Cryptocaryon irritans

The parasitic ciliate Cryptocaryon irritans, which infects almost all marine fish species occurring in both tropical and subtropical regions throughout the world. The disease, cryptocaryonosis, accounts for significant economic losses to the aquaculture industry. This review attempts to provide a comprehensive overview of the biology of the parasite, host-parasite interactions and both specific and non-specific host defense mechanisms are responsible for the protection of fish against challenge infections with this ciliate. Also, this article reflects the current interest in this subject area and the quest to develop an available vaccine against the disease. Due to the high frequency of clinical fish cryptocaryonosis, the study of fish immune responses to C. irritans provides an optimal experimental model for understanding immunity against extracellular protozoa.

Resolving the immune landscape of human prostate at a single-cell level in health and cancer

The prostate gland produces prostatic fluid, high in zinc and citrate and essential for the maintenance of spermatozoa. Prostate cancer is a common condition with limited treatment efficacy in castration-resistant metastatic disease, including with immune checkpoint inhibitors. Using single-cell RNA-sequencing to perform an unbiased assessment of the cellular landscape of human prostate, we identify a subset of tumor-enriched androgen receptor-negative luminal epithelial cells with increased expression of cancer-associated genes. We also find a variety of innate and adaptive immune cells in normal prostate that were transcriptionally perturbed in prostate cancer. An exception is a prostate-specific, zinc transporter-expressing macrophage population (MAC-MT) that contributes to tissue zinc accumulation in homeostasis but shows enhanced inflammatory gene expression in tumors, including T cell-recruiting chemokines. Remarkably, enrichment of the MAC-MT signature in cancer biopsies is associated with improved disease-free survival, suggesting beneficial antitumor functions.

Impaired Dendritic Cell Homing in COVID-19

The high mortality of COVID-19 is mostly attributed to acute respiratory distress syndrome (ARDS), whose histopathological correlate is diffuse alveolar damage (DAD). Furthermore, severe COVID-19 is often accompanied by a cytokine storm and a disrupted response of the adaptive immune system. Studies aiming to depict this dysregulation have mostly investigated the peripheral cell count as well as the functionality of immune cells. We investigated the impact of SARS-CoV-2 on antigen-presenting cells using multiplexed immunofluorescence. Similar to MERS-CoV and SARS-CoV, SARS-CoV-2 appears to be impairing the maturation of dendritic cells (DCs). DC maturation involves a switch in surface antigen expression, which enables the cells' homing to lymph nodes and the subsequent activation of T-cells. As quantitative descriptions of the local inflammatory infiltrate are still scarce, we compared the cell population of professional antigen-presenting cells (APC) in the lungs of COVID-19 autopsy cases in different stages of DAD. We found an increased count of myeloid dendritic cells (mDCs) in later stages. Interestingly, mDCs also showed no significant upregulation of maturation markers in DAD-specimens with high viral load. Accumulation of immature mDCs, which are unable to home to lymph nodes, ultimately results in an inadequate T-cell response.

Extracellular vesicles cargo from head and neck cancer cell lines disrupt dendritic cells function and match plasma microRNAs

Extracellular vesicles (EVs) are mediators of the immune system response. Encapsulated in EVs, microRNAs can be transferred between cancer and immune cells. To define the potential effects of EVs originated from squamous cell carcinoma cells on immune system response, we performed microRNA profiling of EVs released from two distinct cell lines and treated dendritic cells derived from circulating monocytes (mono-DCs) with these EVs. We confirmed the internalization of EVs by mono-DCs and the down-regulation of microRNA mRNA targets in treated mono-DCs. Differences in surface markers of dendritic cells cultivated in the presence of EVs indicated that their content disrupts the maturation process. Additionally, microRNAs known to interfere with dendritic cell function, and detected in EVs, matched microRNAs from squamous cell carcinoma patients' plasma: miR-17-5p in oropharyngeal squamous cell carcinoma, miR-21 in oral squamous cell carcinoma, miR-16, miR-24, and miR-181a circulating in both oral and oropharyngeal squamous cell carcinoma, and miR-23b, which has not been previously described in plasma of head and neck squamous cell carcinoma, was found in plasma from patients with these cancer subtypes. This study contributes with insights on EVs in signaling between cancer and immune cells in squamous cell carcinoma of the head and neck.

Characterization and Manipulation of the Crosstalk Between Dendritic and Natural Killer Cells Within the Tumor Microenvironment

Cellular therapy has entered the daily clinical life with the approval of CAR T cell therapeutics and dendritic cell (DCs) vaccines in the US and the EU. In addition, numerous other adoptive cellular products, including natural killer (NK) cells, are currently evaluated in early phase I/ II clinical trials for the treatment of cancer patients. Despite these promising accomplishments, various challenges remain to be mastered in order to ensure sustained therapeutic success. These include the identification of strategies by which tumor cells escape the immune system or establish an immunosuppressive tumor microenvironment (TME). As part of the innate immune system, DCs and NK cells are both present within the TME of various tumor entities. While NK cells are well known for their intrinsic anti-tumor activity by their cytotoxicity capacities and the secretion of pro-inflammatory cytokines, the role of DCs within the TME is a double-edged sword as different DC subsets have been described with either tumor-promoting or -inhibiting characteristics. In this review, we will discuss recent findings on the interaction of DCs and NK cells under physiological conditions and within the TME. One focus is the crosstalk of various DC subsets with NK cells and their impact on the progression or inhibition of tumor growth. In addition, we will provide suggestions to overcome the immunosuppressive outcome of the interaction of DCs and NK cells within the TME.

Exploring the Emerging Role of the Gut Microbiota and Tumor Microenvironment in Cancer Immunotherapy

The tumor microenvironment (TME) is a complex ecosystem, which includes many different types of cells, abnormal vascular systems, and immunosuppressive cytokines. TME serves an important function in tumor tolerance and escapes from immune surveillance leading to tumor progression. Indeed, there is increasing evidence that gut microbiome is associated with cancer in a variety of ways, as specific microbial signatures are known to promote cancer development and influence safety, tolerability, and efficacy of therapies. Studies over the past five years have shown that the composition of the intestinal microbiota has a significant impact on the efficacy of anticancer immunosurveillance, which contribute to the therapeutic activity of cancer immunotherapies based on targeting cytotoxic T lymphocyte protein 4 (CTLA-4) or programmed cell death protein 1 (PD-1)-programmed cell death 1 ligand 1 (PD-L1) axis. In this review, we mainly discuss the impact of TME on cancer and immunotherapy through immune-related mechanisms. We subsequently discuss the influence of gut microbiota and its metabolites on the host immune system and the formation of TME. In addition, this review also summarizes the latest research on the role of gut microbiota in cancer immunotherapy.

Association of serum chemokine ligand 21 levels with asthma control in adults

OBJECTIVES

The chemokine ligand (CCL) 21 regulates the maturation, migration, and function of dendritic cells, and has been implicated in the pathogenesis of asthma. This study aimed to investigate the association between serum CCL21 levels and asthma control.

METHODS

The serum levels of CCL21 and other inflammatory cytokines were analyzed in patients with asthma (n=44) and healthy controls (n=35) by enzyme-linked immunosorbent assay. IgE levels and eosinophil counts were determined by turbidimetric inhibition immunoassay and fully automatic blood analysis, respectively. The Asthma Control Test (ACT) questionnaire was used, and spirometry and fractional exhaled nitric oxide (FENO) measurements were performed. A multiple unpaired Student's t-test was performed to analyze the differences in CCL21 and interleukin levels between patients with asthma and healthy controls. The correlation of CCL21 levels with disease severity was evaluated using the Pearson's rank correlation test.

RESULTS

Serum CCL21 levels were lower in patients with asthma (254.78±95.66 pg/mL) than in healthy controls (382.95±87.77 pg/mL) (p<0.001). Patients with asthma had significantly higher levels of IL-1β (19.74±16.77 vs. 2.63±5.22 pg/mL), IL-6 (7.55±8.65 vs. 2.37±2.47 pg/mL), and tumor necrosis factor-α (12.70±12.03 vs. 4.82±3.97 pg/mL) compared with the controls. CCL21 levels were positively correlated with the ACT score (rs=0.1653, p=0.0062), forced expiratory volume in 1s (FEV1)/forced vital capacity (rs=0.3607, p<0.0001), and FEV1 (rs=0.2753, p=0.0003), and negatively correlated with FENO (rs=0.1060, p=0.0310). CCL21 levels were negatively correlated with serum IgE levels (rs=0.1114, p=0.0268) and eosinophil counts (rs=0.3476, p<0.0001).

CONCLUSIONS

Serum CCL21 levels may be a new biomarker for assessing asthma control.

WITHDRAWN: Allergic mechanisms of asthma are enhanced during the summer with oxidant PM10 components

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A New Microfluidic Platform for Studying Natural Killer Cell and Dendritic Cell Interactions

The importance of the bi-directional natural killer–dendritic cell crosstalk in coordinating anti-tumour and anti-microbial responses in vivo has been well established. However, physical parameters associated with natural killer–dendritic cell interactions have not been fully elucidated. We have previously used a simple “Y” shaped microfluidic device to study natural killer cell-migratory responses toward chemical gradients from a conditioned medium of dendritic cells. There are, however, limitations of the Y-shaped microfluidic devices that could not support higher throughput analyses and studies of cell–cell interactions. Here, we report two novel microfluidic devices (D³-Chip, T²-Chip) we applied in advanced studies of natural killer-cell migrations and their interactions with dendritic cells in vitro. The D³-Chip is an improved version of the previously published Y-shaped device that supports high-throughput analyses and docking of the cells of interest in the migration assay before they are exposed to a chemical gradient. The T²-Chip is created to support analyses of natural killer–dendritic cell cell–cell interactions without the requirement of promoting a natural killer cell to migrate long distances to find a loaded dendritic cell in the device. Using these two microfluidic platforms, we observe quantitative differences in the abilities of the immature and lipopolysaccharide-activated mature dendritic cells to interact with activated natural killer cells. The contact time between the activated natural killer cells and immature dendritic cells is significantly longer than that of the mature dendritic cells. There is a significantly higher frequency of an immature dendritic cell coming into contact with multiple natural killer cells and/or making multiple simultaneous contacts with multiple natural killer cells. To contrast, an activated natural killer cell has a significantly higher frequency of coming into contact with the mature dendritic cells than immature dendritic cells. Collectively, these differences in natural killer–dendritic cell interactions may underlie the differential maturation of immature dendritic cells by activated natural killer cells. Further applications of these microfluidic devices in studying natural killer–dendritic cell crosstalk under defined microenvironments shall enrich our understanding of the functional regulations of natural killer cells and dendritic cells in the natural killer–dendritic cell crosstalk.

Aspects of intradermal immunization with different adjuvants: The role of dendritic cells and Th1/Th2 response

Intradermal (i.d.) application of vaccine is promising way how to induce specific immune response against particular pathogens. Adjuvants, substances added into vaccination dose with the aim to increase immunogenicity, play important role in activation of dendritic cells with subsequent activation of lymphocytes. They can, however, induce unwanted local reactions. The aim of the study was to determine the effect of i.d. administration of model antigen keyhole limped hemocyanine alone or with different adjuvants-aluminium hydroxide and oil-based adjuvants-on local histopathological reaction as well as dendritic cell activation at the site of administration and local cytokine and chemokine response. This was assessed at 4 and 24 hours after application. Selection of the adjuvants was based on the fact, that they differently enhance antibody or cell-mediated immunity. The results showed activation of dendritic cells and both Th1 and Th2 response stimulated by oil-based adjuvants. It was associated with higher expression of set of genes, incl. chemokine receptor CCR7 or Th1-associated chemokine CXCL10 and cytokine IFNγ. Application of the antigen with aluminium hydroxide induced higher expression of Th2-associated IL4 or IL13. On the other hand, both complete and incomplete Freund´s adjuvants provoked strong local reaction associated with influx of neutrophils. This was accompanied with high expression of proinflammatory IL1 or neutrophil chemoattractant CXCL8. Surprisingly, similarly strong local reaction was detected also after application of aluminium hydroxide-based adjuvant. The best balanced local reaction with sufficient activation of immune cells was detected after application of oil-based adjuvants Montanide and Emulsigen.

Role of the p38 MAPK/C/EBPβ Pathway in the Regulation of Phenotype and IL-10 and IL-12 Production by Tolerogenic Bone Marrow-Derived Dendritic Cells

Dendritic cells (DCs) play a major role in innate and adaptive immunity and self-immune tolerance. Immunogenic versus tolerogenic DC functions are dictated by their levels of costimulatory molecules and their cytokine expression profile. The transcription factor C/EBPβ regulates the expression of several inflammatory genes in many cell types including macrophages. However, little is known regarding the role of C/EBPβ in tolerogenic versus immunogenic DCs functions. We have previously reported that bone marrow-derived DCs generated with GM-CSF (GM/DCs) acquire the signature of semi-mature tolerogenic IL-10-producing DCs as opposed to immunogenic DCs generated with GM-CSF and IL-4 (IL-4/DCs). Here, we show that tolerogenic GM/DCs exhibit higher levels of phosphorylation and enhanced DNA binding activity of C/EBPβ and CREB than immunogenic IL-4/DCs. We also show that the p38 MAPK/CREB axis and GSK3 play an important role in regulating C/EBPβ phosphorylation and DNA binding activity. Inhibition of p38 MAPK in GM/DCs resulted in a drastic decrease of C/EBPβ and CREB DNA binding activities, a reduction of their IL-10 production and an increase of their IL-12p70 production, a characteristic of immunogenic IL-4/DCs. We also present evidence that GSK3 inhibition in GM/DCs reduced C/EBPβ DNA binding activity and increased expression of costimulatory molecules in GM/DCs and their production of IL-10. Analysis of GM/DCs of C/EBPβ^-/- mice showed that C/EBPβ was essential to maintain the semimature phenotype and the production of IL-10 as well as low CD4⁺ T cell proliferation. Our results highlight the importance of the p38MAPK-C/EBPβ pathway in regulating phenotype and function of tolerogenic GM/DCs.

Elderly dendritic cells respond to LPS/IFN-γ and CD40L stimulation despite incomplete maturation

There is evidence that dendritic cells (DCs) undergo age-related changes that modulate their function with their key role being priming antigen-specific effector T cells. This occurs once DCs develop into antigen-presenting cells in response to stimuli/danger signals. However, the effects of aging on DC responses to bacterial lipopolysaccharide (LPS), the pro-inflammatory cytokine interferon (IFN)-γ and CD40 ligand (CD40L) have not yet been systematically evaluated. We examined responses of blood myeloid (m)DC1s, mDC2s, plasmacytoid (p)DCs, and monocyte-derived DCs (MoDCs) from young (21–40 years) and elderly (60–84 years) healthy human volunteers to LPS/IFN-γ or CD40L stimulation. All elderly DC subsets demonstrated comparable up-regulation of co-stimulatory molecules (CD40, CD80 and/or CD86), intracellular pro-inflammatory cytokine levels (IFN-γ, tumour necrosis factor (TNF)-α, IL-6 and/or IL-12), and/or secreted cytokine levels (IFN-α, IFN-γ, TNF-α, and IL-12) to their younger counterparts. Furthermore, elderly-derived LPS/IFN-γ or CD40L-activated MoDCs induced similar or increased levels of CD8⁺ and CD4⁺ T cell proliferation, and similar T cell functional phenotypes, to their younger counterparts. However, elderly LPS/IFN-γ-activated MoDCs were unreliable in their ability to up-regulate chemokine (IL-8 and monocyte chemoattractant protein (MCP)-1) and IL-6 secretion, implying an inability to dependably induce an inflammatory response. A key age-related difference was that, unlike young-derived MoDCs that completely lost their ability to process antigen, elderly-derived MoDCs maintained their antigen processing ability after LPS/IFN-γ maturation, measured using the DQ-ovalbumin assay; this response implies incomplete maturation that may enable elderly DCs to continuously present antigen. These differences may impact on the efficacy of anti-pathogen and anti-tumour immune responses in the elderly.

Astrocyte-derived CCL20 reinforces HIF-1-mediated hypoxic responses in glioblastoma by stimulating the CCR6-NF-κB signaling pathway

During tumor development, stromal cells are co-opted to the tumor milieu and provide favorable conditions for the tumor. Hypoxia stimulates cancer cells to acquire a more malignant phenotype via activation of hypoxia-inducible factor 1 (HIF-1). Given that cancer cells and astrocytes in glioblastomas coexist in a hypoxic microenvironment, we examined whether astrocytes affect the adaptation of glioblastoma cells to hypoxia. Immunoblotting, reporter assays, quantitative RT-PCR, and chromatin immunoprecipitation were performed to evaluate HIF-1 signaling in glioblastoma cells. Astrocyte-derived chemokine C-C motif ligand 20 (CCL20) was identified using cytokine arrays, and its role in glioblastoma development was evaluated in orthotopic xenografts. Astrocytes augmented HIF-1α expression in glioblastoma cells under hypoxia. The expression of HIF-1 downstream genes, cancer colony formation, and Matrigel invasion of glioblastoma cells were stimulated by conditioned medium from astrocytes pre-exposed to hypoxia. CCL20 was secreted in a hypoxia-dependent manner from astrocytes and busted the hypoxic induction of HIF-1α in glioblastoma cells. Mechanistically, the CCL20/CCR6 signaling pathway upregulates HIF-1α by stimulating nuclear factor kappa B-driven transactivation of the HIF1A gene. Compared with the control tumors, CCR6-deficient glioblastoma xenografts grew more slowly, with poor vascularization, and expressed lower levels of HIF-1α and its downstream proteins. Furthermore, CCR6 expression was correlated with HIF-1α expression in GEO and TCGA datasets from human glioblastoma tissues. These results suggest that glioblastoma cells adapt well to hypoxic stress by virtue of CCL20 derived from neighboring astrocytes.

NK Cells Stimulate Recruitment of cDC1 into the Tumor Microenvironment Promoting Cancer Immune Control

Conventional type 1 dendritic cells (cDC1) are critical for antitumor immunity, and their abundance within tumors is associated with immune-mediated rejection and the success of immunotherapy. Here, we show that cDC1 accumulation in mouse tumors often depends on natural killer (NK) cells that produce the cDC1 chemoattractants CCL5 and XCL1. Similarly, in human cancers, intratumoral CCL5, XCL1, and XCL2 transcripts closely correlate with gene signatures of both NK cells and cDC1 and are associated with increased overall patient survival. Notably, tumor production of prostaglandin E2 (PGE2) leads to evasion of the NK cell-cDC1 axis in part by impairing NK cell viability and chemokine production, as well as by causing downregulation of chemokine receptor expression in cDC1. Our findings reveal a cellular and molecular checkpoint for intratumoral cDC1 recruitment that is targeted by tumor-derived PGE2 for immune evasion and that could be exploited for cancer therapy.

Sex-based differences in CD103+ dendritic cells promote female-predominant Th2 cytokine production during allergic asthma

BACKGROUND

Gender disparities in adult patients with asthma regarding its prevalence and severity are mainly due to enhanced type 2 T-helper (Th2) cytokine production in female patients compared to that in male patients. However, the pathways mediating this effect remain unclear.

OBJECTIVE

We aimed to determine the roles of two major subsets of dendritic cells (DCs) in females, specifically those displaying CD11b or CD103, during enhanced Th2 priming after allergen exposure, using an ovalbumin-induced asthma mouse model.

METHODS

Sex-based differences in the number of DCs at inflamed sites, costimulatory molecule expression on DCs, and the ability of DCs to differentiate naïve CD4⁺ T cells into Th2 population were evaluated after allergen exposure in asthmatic mice. In addition, we assessed the role of 17β-oestradiol in CD103⁺ DC function during Th2 priming in vitro.

RESULTS

The number of CD11b^high DCs and CD103⁺ DCs in the lung and bronchial lymph node (BLN) was increased to a greater extent in female mice than in male mice at 16 to 20 hours after ovalbumin (OVA) inhalation. In BLNs, CD86 and I-A/I-E expression levels and antigen uptake ability in CD103⁺ DCs, but not in CD11b^high DCs, were greater in female mice than in male mice. Furthermore, CD4⁺ T cells cultured with CD103⁺ DCs from female mice produced higher levels of interleukin (IL)-4, IL-5, and IL-13, compared with CD4⁺ T cells cultured with CD103⁺ DCs from male mice. The 17β-oestradiol-oriented enhancement of CD86 expression on CD103⁺ DCs after allergen exposure induced the enhanced IL-5 production from CD4⁺ T cells.

CONCLUSIONS AND CLINICAL RELEVANCE

These findings suggest that with regard to asthma, enhanced Th2 cytokine production in females might be attributed to 17β-oestradiol-mediated Th2-oriented CD103⁺ DCs in the BLN.

Knockdown of myeloid cell hypoxia-inducible factor-1α ameliorates the acute pathology in DSS-induced colitis

Inflammation and hypoxia are hallmarks of inflammatory bowel disease. Low oxygen levels activate hypoxia-inducible factors as central transcriptional regulators of cellular responses to hypoxia, particularly in myeloid cells where hypoxia-inducible factors control immune cell function and survival. Still, the role of myeloid hypoxia-inducible factor-1 during inflammatory bowel disease remains poorly defined. We therefore investigated the role of hypoxia-inducible factor-1 for myeloid cell function and immune response during colitis. Experimental colitis was induced by administration of 2.5% dextran sulfate sodium to mice with a conditional knockout of hypoxia-inducible factor-1α in myeloid cells and their wild type siblings. Murine colon tissue was examined by histologic analysis, immunohistochemistry, and quantitative polymerase chain reaction. Induction of experimental colitis increased levels of hypoxia and accumulation of hypoxia-inducible factor-1α positive cells in colon tissue of both treated groups. Myeloid hypoxia-inducible factor-1α knockout reduced weight loss and disease activity index when compared to wild type mice. Knockout mice displayed less infiltration of macrophages into intestinal mucosa and reduced mRNA expression of markers for dendritic cells and interleukin-17 secreting T helper cells. Expression of inflammatory and anti-inflammatory cytokines also showed a reduced and delayed induction in myeloid hypoxia-inducible factor-1α knockout mice. Our results show a disease promoting role of myeloid hypoxia-inducible factor-1 during intestinal inflammation. This might result from a hypoxia-inducible factor-1 dependent increase in pro-inflammatory interleukin-17 secreting T helper cells in the absence of obvious changes in regulatory T cells. In contrast, knockout mice appear to shift the balance to anti-inflammatory signals and cells resulting in milder intestinal inflammation.

Applications of chemokines as adjuvants for vaccine immunotherapy

Vaccinations are expected to aid in building immunity against pathogens. This objective often requires the addition of an adjuvant with certain vaccine formulations containing weakly immunogenic antigens. Adjuvants can improve antigen processing, presentation, and recognition, thereby improving the immunogenicity of a vaccine by simulating and eliciting an immune response. Chemokines are a group of small chemoattractant proteins that are essential regulators of the immune system. They are involved in almost every aspect of tumorigenesis, antitumor immunity, and antimicrobial activity and also play a critical role in regulating innate and adaptive immune responses. More recently, chemokines have been used as vaccine adjuvants due to their ability to modulate lymphocyte development, priming and effector functions, and enhance protective immunity. Chemokines that are produced naturally by the body's own immune system could serve as potentially safer and more reliable adjuvant options versus synthetic adjuvants. This review will primarily focus on chemokines and their immunomodulatory activities against various infectious diseases and cancers.

Endogenous glucocorticoid signaling in chondrocytes attenuates joint inflammation and damage

Previous studies demonstrated that endogenous glucocorticoid signaling in osteoblasts promotes inflammation in murine immune arthritis. The current study determined whether disruption of endogenous glucocorticoid signaling in chondrocytes also modulates the course and severity of arthritis. Tamoxifen-inducible chondrocyte-targeted glucocorticoid receptor-knockout (chGRKO) mice were generated by breeding GR^flox/flox mice with tamoxifen-inducible collagen 2a1 Cre (Col2a1-CreER^T2) mice. Antigen-induced arthritis (AIA) and K/BxN serum transfer-induced arthritis (STIA) were induced in both chGRKO mice and their Cre-negative GR^flox/flox littermates [wild type (WT)]. Arthritis was assessed by measurement of joint swelling and histology of joints collected at d 14. Neutrophil activity and gene expression patterns associated with cartilage damage were also evaluated. In both arthritis models clinical (joint swelling) and histologic indices of inflammatory activity were significantly greater in chGRKO than in WT mice. The STIA model was characterized by early up-regulation of CXCR2/CXCR2 ligand gene expression in ankle tissues, and significant and selective expansion of splenic CXCR2⁺ neutrophils in chGRKO arthritic compared to WT arthritic mice. At later stages, gene expression of enzymes involved in cartilage degradation was up-regulated in chGRKO but not WT arthritic mice. Therefore, we summarize that chondrocytes actively mitigate local joint inflammation, cartilage degradation and systemic neutrophil activity via a glucocorticoid-dependent pathway.-Tu, J., Stoner, S., Fromm, P. D., Wang, T., Chen, D., Tuckermann, J., Cooper, M. S., Seibel, M. J., Zhou, H. Endogenous glucocorticoid signaling in chondrocytes attenuates joint inflammation and damage.

Immunomodulatory effects of heat-killed Mycobacterium obuense on human blood dendritic cells

Heat-killed (HK) Mycobacterium obuense is a novel immunomodulator, currently undergoing clinical evaluation as an immunotherapeutic agent in the treatment of cancer. Here, we examined the effect of in vitro exposure to HK M. obuense on the expression of different categories of surface receptors on human blood myeloid (m) and plasmacytoid (p) DCs. Moreover, we have characterized the cytokine and chemokine secretion patterns of purified total blood DCs stimulated with HK M. obuense. HK M. obuense significantly up-regulated the expression of CD11c, CD80, CD83, CD86, CD274 and MHC class II in whole-blood mDCs and CD80, CD123 and MHC class II in whole-blood pDCs. Down-regulation of CD195 expression in both DC subpopulations was also noted. Further analysis showed that HK M. obuense up-regulated the expression of CD80, CD83 and MHC class II on purified blood DC subpopulations. TLR2 and TLR1 were also identified to be engaged in mediating the HK M. obuense-induced up-regulation of surface receptor expression on whole blood mDCs. In addition, our data demonstrated that HK M. obuense augmented the secretion of CCL4, CCL5, CCL22, CXCL8, IL-6, IL-12p40 and TNF-α by purified total blood DCs. Taken together, our data suggest that HK M. obuense exerts potent differential immunomodulatory effects on human DC subpopulations.

The role of chemokines and their receptors during protist parasite infections

Protists are a diverse collection of eukaryotic organisms that account for a significant global infection burden. Often, the immune responses mounted against these parasites cause excessive inflammation and therefore pathology in the host. Elucidating the mechanisms of both protective and harmful immune responses is complex, and often relies of the use of animal models. In any immune response, leucocyte trafficking to the site of infection, or inflammation, is paramount, and this involves the production of chemokines, small chemotactic cytokines of approximately 8–10 kDa in size, which bind to specific chemokine receptors to induce leucocyte movement. Herein, the scientific literature investigating the role of chemokines in the propagation of immune responses against key protist infections will be reviewed, focussing onPlasmodiumspecies,Toxoplasma gondii, Leishmaniaspecies andCryptosporidiumspecies. Interestingly, many studies find that chemokines can in fact, promote parasite survival in the host, by drawing in leucocytes for spread and further replication. Recent developments in drug targeting against chemokine receptors highlights the need for further understanding of the role played by these proteins and their receptors in many different diseases.

Examining Roles of Glycans in Chemokine-Mediated Dendritic-Endothelial Cell Interactions

Interactions between glycosaminoglycans (GAGs) and chemokines play a critical role in multiple physiological and pathological processes, including tumor metastasis and immune-cell trafficking. During our studies examining the genetic importance of the GAG subtype known as heparan sulfate (HS) on lymphatic endothelial cells (LECs), we established a repertoire of methods to assess how HS affects chemokine-mediated cell-cell interactions. In this chapter, we describe methods for monitoring migration and adhesion interactions of dendritic cells (DCs), the most potent antigen-presenting cells, with LECs. We will also report a methodology to assess chemokine-receptor interactions while incorporating approaches to target HS in the system. This includes in situ methods to visualize and quantify direct interactions between chemokines and chemokine receptors on DC surfaces, and how targeting HS produced by LECs or even DCs affects these interactions. These methods enable the mechanistic and functional characterization of GAG-chemokine interactions in cell-based studies that model physiologic interactions ex vivo. They may also be used to obtain novel insights into GAG-mediated biological processes.

Characterization and expression analysis of two novel CCR6 chemokine receptors and their three potential ligands CCL20Ls of grouper (Epinephelus coioides) post Cryptocaryon irritans infection

CCR6 have been demonstrated playing an important role in immune cells homing to mucosal tissues, mediating antigen presentation and immune response in mammals. CCR6 in lower vertebrate leukocyte homing has not yet been revealed. Cryptocaryon irritans is believed to be a good pathogen model for skin and gill mucosal immunity. In this study, we identified two CCR6s and their three possible ligands CCL20 like cDNA sequences, designated as grouper EcCCR6A, EcCCR6B, EcCCL20L1, EcCCL20L2 and EcCCL20L3. It is interesting to find that EcCCR6A has a longer second extracellular loop than EcCCR6B, which is more similar to mammalian CCR6. Tissue distribution analysis showed that EcCCR6A pronouncedly dominates in gill and brain while EcCCR6B dominates in head kidney, trunk kidney and thymus. Three chemokine ligands have their own distinct expression pattern in health grouper tissues. EcCCL20L1 dominates in spleen and head kidney, EcCCL20L2 dominates in gill and thymus, whereas EcCCL20L3 dominates in skin and brain. The expression patterns of these chemokines and chemokine receptors were detected in C. irritans infected grouper and the results showed that EcCCR6A, EcCCR6B and EcCCL20L1 were significantly up-regulated in the skin of C. irritans infected fish, which indicated these two chemokine receptors and their ligand may play important role in immune cells' homing to skin mucosal immune tissues under pathogen caused inflammation.

Chemokines as Cancer Vaccine Adjuvants

We are witnessing a new era of immune-mediated cancer therapies and vaccine development. As the field of cancer vaccines advances into clinical trials, overcoming low immunogenicity is a limiting step in achieving full success of this therapeutic approach. Recent discoveries in the many biological roles of chemokines in tumor immunology allow their exploitation in enhancing recruitment of antigen presenting cells (APCs) and effector cells to appropriate anatomical sites. This knowledge, combined with advances in gene therapy and virology, allows researchers to employ chemokines as potential vaccine adjuvants. This review will focus on recent murine and human studies that use chemokines as therapeutic anti-cancer vaccine adjuvants.

Chemokine programming dendritic cell antigen response: part I - select chemokine programming of antigen uptake even after maturation

Here, we report on the successful programming of dendritic cells (DCs) using selectively applied mixtures of chemokines as a novel protocol for engineering vaccine efficiency. Antigen internalization by DCs is a pivotal step in antigen uptake/presentation for bridging innate and adaptive immunity and in exogenous gene delivery used in vaccine strategies. Contrary to most approaches to improve vaccine efficiency, active enhancement of antigen internalization by DCs as a vaccine strategy has been less studied because DCs naturally down-regulate antigen internalization upon maturation. Whereas chemokines are mainly known as signal proteins that induce leucocyte chemotaxis, very little research has been carried out to identify any additional effects of chemokines on DCs following maturation. Here, immature DCs are pre-treated with select chemokines before intentional maturation using lipopolysaccharide (LPS). When pre-treated with a mixture of CCL3 and CCL19 in a 7 : 3 ratio, then matured with LPS, chemokine pre-treated DCs exhibited 36% higher antigen uptake capacity than immature DCs and 27% higher antigen-processing capacity than immature DCs treated only with LPS. Further, CCL3 : CCL19 (7 : 3) pre-treatment of DCs modulated MHC molecule expression and secretion of various cytokines of DCs. Collectively, DC programming was feasible using a specific chemokine combination and these results provide a novel strategy for enhancing DC-based vaccine efficiency. In Part II, we report on the phenotype changes and antigen presentation capacity of chemokine pre-treated murine bone marrow-derived DCs examined in long-term co-culture with antigen-specific CD4(+) T cells.

The possible diagnostic and prognostic use of systemic chemokine profiles in clinical medicine—the experience in acute myeloid leukemia from disease development and diagnosis via conventional chemotherapy to allogeneic stem cell transplantation

Chemokines are important regulators of many different biological processes, including (i) inflammation with activation and local recruitment of immunocompetent cells; (ii) angiogenesis as a part of inflammation or carcinogenesis; and (iii) as a bridge between the coagulation system and inflammation/immune activation. The systemic levels of various chemokines may therefore reflect local disease processes, and such variations may thereby be used in the routine clinical handling of patients. The experience from patients with myeloproliferative diseases, and especially patients with acute myeloid leukemia (AML), suggests that systemic plasma/serum cytokine profiles can be useful, both as a diagnostic tool and for prognostication of patients. However, cytokines/chemokines are released by a wide range of cells and are involved in a wide range of biological processes; the altered levels may therefore mainly reflect the strength and nature of the biological processes, and the optimal clinical use of chemokine/cytokine analyses may therefore require combination with organ-specific biomarkers. Chemokine levels are also altered by clinical procedures, therapeutic interventions and the general status of the patients. A careful standardization of sample collection is therefore important, and the interpretation of the observations will require that the overall clinical context is considered. Despite these limitations, we conclude that analysis of systemic chemokine/cytokine profiles can reflect important clinical characteristics and, therefore, is an important scientific tool that can be used as a part of future clinical studies to identify clinically relevant biomarkers.

oxLDL downregulates the dendritic cell homing factors CCR7 and CCL21

INTRODUCTION

Dendritic cells (DCs) and oxLDL play an important role in the atherosclerotic process with DCs accumulating in the plaques during plaque progression. Our aim was to investigate the role of oxLDL in the modulation of the DC homing-receptor CCR7 and endothelial-ligand CCL21.

METHODS AND RESULTS

The expression of the DC homing-receptor CCR7 and its endothelial-ligand CCL21 was examined on atherosclerotic carotic plaques of 47 patients via qRT-PCR and immunofluorescence. In vitro, we studied the expression of CCR7 on DCs and CCL21 on human microvascular endothelial cells (HMECs) in response to oxLDL. CCL21- and CCR7-mRNA levels were significantly downregulated in atherosclerotic plaques versus non-atherosclerotic controls [90% for CCL21 and 81% for CCR7 (P < 0.01)]. In vitro, oxLDL reduced CCR7 mRNA levels on DCs by 30% and protein levels by 46%. Furthermore, mRNA expression of CCL21 was significantly reduced by 50% (P < 0.05) and protein expression by 24% in HMECs by oxLDL (P < 0.05).

CONCLUSIONS

The accumulation of DCs in atherosclerotic plaques appears to be related to a downregulation of chemokines and their ligands, which are known to regulate DC migration. oxLDL induces an in vitro downregulation of CCR7 and CCL21, which may play a role in the reduction of DC migration from the plaques.

Antigen presenting cells in a non-mammalian model system, the chicken

The chicken has a different repertoire of tissues, cells and genes of the immune response compared to mammals, yet generally survives infection with viral, bacterial, protozoal and fungal pathogens, and also worms and ectoparasites, just like mammals. Poultry are also probably the most heavily vaccinated group of farmed animals. Antigen presentation to the adaptive immune response therefore obviously normally occurs efficiently in birds. Although comparatively much is known about macrophages and B cells in the chicken, there is as yet little work on the other, professional, antigen-presenting cells, the dendritic cells (DC). Birds also have at least two other sets of phagocytic cells, heterophils and thrombocytes, which may also have the ability to present antigen. Here we review the current state of knowledge about antigen presenting cells in the chicken, concentrating mainly on recent advances in our knowledge of DC.

Chicken CCR6 and CCR7 are markers for immature and mature dendritic cells respectively

In mammals, the CC chemokine receptors 6 and 7 (CCR6 and CCR7) play important roles in controlling the trafficking of dendritic cells (DC). CCR6 is expressed primarily on immature DC in the periphery and plays a role in the recruitment of immature DC to sites of potential antigen entry. On encountering pathogens, DC mature and migrate to secondary lymphoid organs where they present pathogen antigen to T cells to initiate specific adaptive immune responses. Maturation involves down-regulation of CCR6 but up-regulation of CCR7. To investigate the role of these two chemokine receptors in the function of DC in the chicken, a full-length chicken CCR7 (chCCR7) cDNA was cloned. Chicken CCR6 (chCCR6) was already available (Munoz et al., 2009). ChCCR7 shows the typical secondary structure of a seven-transmembrane G protein-coupled receptor and has 66% and 64% amino acid identity with human and mouse CCR7, respectively. Like its mammalian orthologues, chCCR7 mRNA was highly expressed in most lymphoid tissues (with the exception of the Harderian gland) and also in some non-lymphoid tissues (especially the heart, lung, skin and small intestine). Both chCCR6 and chCCR7 were expressed at the mRNA level in immature chicken bone marrow-derived dendritic cells (chBM-DC), as measured by real-time quantitative RT-PCR. After DC maturation following stimulation with LPS or CD40L, expression levels of chCCR6 mRNA were down-regulated, whereas those of chCCR7 were up-regulated, suggesting that these two chemokine receptors play a similar role in the trafficking of chicken DC as they do in mammals and that they act as markers of immature (chCCR6) and mature (chCCR7) DC.

Epigenetic regulation of immune cell functions during post-septic immunosuppression

Studies in humans and animal models indicate that profound immunosuppression is one of the chronic consequences of severe sepsis. This immune dysfunction encompasses deficiencies in activation of cells in both the myeloid and lymphoid cell lineages. As a result, survivors of severe sepsis are at risk of succumbing to infections perpetrated by opportunistic pathogens that are normally controlled by a fully functioning immune system. Recent studies have indicated that epigenetic mechanisms may be one driving force behind this immunosuppression, through suppression of proinflammatory gene production and subsequent immune cell activation, proliferation and effector function. A better understanding of epigenetics and post-septic immunosuppression can improve our diagnostic tools and may be an important potential source of novel molecular targets for new therapies. This review will discuss important pathways of immune cell activation affected by severe sepsis, and highlight pathways of epigenetic regulation that may be involved in post-septic immunosuppression.

The atypical chemokine receptor CCX-CKR scavenges homeostatic chemokines in circulation and tissues and suppresses Th17 responses

Our previous in vitro studies led to proposals that the atypical chemokine receptor CCX-CKR is a scavenger of CCR7 ligand homeostatic chemokines. In the present study, we generated CCX-CKR−/− mice and confirm this scavenger function in vivo. Compared with wild-type mice, CCX-CKR−/− have a 5-fold increase in the level of CCL21 protein in blood, and 2- to 3-fold increases in CCL19 and CCL21 in peripheral lymph nodes. The effect of these protein increases on immunity was investigated after immunization with MOG35-55 peptide emulsified in complete Freund adjuvant (CFA). The subsequent characteristic paralysis develops with enhanced kinetics and severity in CCX-CKR−/− versus wild-type mice. Despite this effect, antigen-specific immune responses in the draining lymph nodes are diminished in CCX-CKR−/− mice. Instead, the earlier onset of disease is associated with enhanced T-cell priming in the CCX-CKR−/− spleen and a skewing of CD4+ T-cell responses toward Th17 rather than Th1. This observation correlates with increased expression of IL-23 in the CCX-CKR−/− spleen and increased CCL21 levels in the central nervous system postimmunization. The early onset of disease in CCX-CKR−/− mice is reversed by systemic administration of neutralizing anti-CCL21 antibodies. Thus, by regulating homeostatic chemokine bioavailability, CCX-CKR influences the localization, kinetics, and nature of adaptive immune responses in vivo.

Epigenetic mechanisms of promigratory chemokine CXCL14 regulation in human prostate cancer cells

Chemokines play the key role in initiating immune responses by regulating the attraction and homing of immune cells to the lymphoid and nonlymphoid tissues. CXCL14 is a chemokine that in tumors may act as chemoattractant for monocytes and dendritic cells (DC), which may modulate antitumor immune responses in certain cancers. In this study, we investigated the mechanisms of loss of CXCL14 in prostate cancer cells. Cell treatment with the demethylating agent 5-aza-2-deoxycytidine resulted in the recovery of CXCL14 mRNA and protein expression. Hypermethylated CpG island sequences encompassing the CXCL14 gene promoter were identified. The restoration of CXCL14 by 5-aza-2-deoxycytidine treatment had functional impact, based on the DC chemoattractant activity of conditioned medium from drug-treated cells. Conversely, CXCL14 removal from conditioned media by affinity chromatography abolished its chemotactic properties, confirming that functionally active CXCL14 was generated in prostate cancer cells by relieving its transcriptional silencing with 5-aza-2-deoxycytidine. Our findings offer the first direct evidence for epigenetic regulation of chemokine expression in tumor cells.

Pathogenesis of giant cell arteritis: More than just an inflammatory condition?

Giant cell arteritis (GCA) is characterized by intimal hyperplasia and luminal obstruction leading to ischemic manifestations involving extra-cranial branches of carotid arteries and aorta. Histopathological lesions involve all layers of the arterial wall and are associated with multinucleated giant cells, fragmented internal elastic lamina and polymorphic cellular infiltrates, including T lymphocytes and macrophages. The pathophysiology of GCA is still poorly understood. After dendritic cell activation, CD4(+) T lymphocytes, T helper 1 (Th1) cells, produce interferon gamma and modulate macrophage activation and functions, and Th17 cells produce interleukin 17 (IL-17), which can induce cytokine production by macrophages and fibroblasts. Macrophages in the adventitia produce pro-inflammatory cytokines such as IL-1, IL-6 and tumor necrosis factor alpha. These cytokines promote arterial wall and systemic inflammation. Questions remain regarding the nature of the antigen(s) triggering dendritic cell activation and the mechanisms underlying vascular remodeling. Here we review recent advances in the pathogenesis of GCA, with emphasis on the interactions between cells of the immune system and components of the vessel wall, including vascular smooth muscle cells and endothelial cells, leading to vascular remodeling. Finally, we propose new areas of investigation that could help understand the triggering factors and key pathogenic events in GCA.

Canine CXCL7 and its functional expression in dendritic cells undergoing maturation

Many cells, including leucocytes and stromal cells, express CXCL7, a member of the CXC chemokine family, also known as platelet basic protein. CXCL7 is a potent chemoattractant and activator of neutrophil function. Dendritic cells (DCs) play a pivotal role in antigen processing and presentation. Very little information is available on the ability of DCs to recruit neutrophils by producing chemokines. In this work, we have cloned canine CXCL7. Based on the predicted gene sequence and using the 3'RACE technique, the full-length gene was amplified from LPS-treated canine peripheral blood mononuclear cells. The cloned cDNA sequence consisted of 357 nucleotides and encoded a 118 amino acid protein, including a 38 amino acid signal peptide. The use of CXCL7-containing supernatants from CXCL7-transfected BALB/3T3 in the neutrophil migration assay confirmed that canine CXCL7 had chemoattractive activity for neutrophils. We then used canine monocyte-derived DCs to generate CXCL7 for the rest of the experiment. Expression of CXCL7 by DCs treated with LPS, IL-1beta, IL-6, TGF-beta, TNF-alpha, or IFN-gamma was compared using real-time RT-PCR and Western blotting. When treated with IL-1beta, IL-6, TNF-alpha, or TGF-beta, canine DCs expressed significantly higher levels of CXCL7 mRNA and protein than when treated with IFN-gamma or LPS. It is concluded that dog DCs express high levels of the neutrophil chemotactic factor CXCL7 when stimulated by proinflammatory cytokines, including IL-1beta, IL-6, TNF-alpha, or TGF-beta, and may play an important role in modulating inflammatory responses.

Early response of mucosal epithelial cells during Toxoplasma gondii infection

The innate immune response of mucosal epithelial cells during pathogen invasion plays a central role in immune regulation in the gut. Toxoplasma gondii is a protozoan intracellular parasite that is usually transmitted through oral infection. Although much of the information on immunity to T. gondii has come from i.p. infection models, more recent studies have revealed the importance of studying immunity following infection through the natural peroral route. Oral infection studies have identified many of the key players in the intestinal response; however, they have relied on responses detected days to weeks following infection. Much less is known about how the gut epithelial layer senses and reacts during initial contact with the pathogen. Given the importance of epithelial cells during pathogen invasion, this study uses an in vitro approach to isolate the key players and examine the early response of intestinal epithelial cells during infection by T. gondii. We show that human intestinal epithelial cells infected with T. gondii elicit rapid MAPK phosphorylation, NF-kappaB nuclear translocation, and secretion of IL-8. Both ERK1/2 activation and IL-8 secretion responses were shown to be MyD88 dependent and TLR2 was identified to be involved in the recognition of the parasite regardless of the parasite genotype. Furthermore, we were able to identify additional T. gondii-regulated genes in the infected cells using a pathway-focused array. Together, our findings suggest that intestinal epithelial cells were able to recognize T. gondii during infection, and the outcome is important for modulating intestinal immune responses.

Oversecretion of cytokines and chemokines in lupus nephritis is regulated by intraparenchymal dendritic cells: a review

Lupus nephritis (LN) occurs in more than one-third of patients with systemic lupus erythematosus. Its pathogenesis is attributed to the glomerular deposition of immune complexes as well as to imbalance of the cytokine homeostasis. In this context, high production of cytokines and chemokines by dendritic cells (DCs) may concur to LN. In addition, urinary cytokine excretion may reflect the accumulation of DCs within glomeruli. DCs are differentiated in both myeloid and plasmacytoid (p) subsets in relation to their typical antigen and chemokine expression. Both subsets migrate in response to chemotactic stimuli because pDCs are susceptible to IL-18 expressed by resident glomerular cells. pDCs bear the IL-18R, and it is conceivable that DCs migrate to the kidney under the attraction of IL-18. Therefore, the depletion of DCs reflects the inflammation severity in LN, whereas measurement of Th1 cytokines may represent an effective tool for monitoring the onset of LN.

HIV-1 gp120-induced migration of dendritic cells is regulated by a novel kinase cascade involving Pyk2, p38 MAP kinase, and LSP1

Targeting dendritic cell (DC) functions such as migration is a pivotal mechanism used by HIV-1 to disseminate within the host. The HIV-1 envelope protein is the most important of the virally encoded proteins that exploits the migratory capacity of DCs. In the present study, we elucidated the signaling machinery involved in migration of immature DCs (iDCs) in response to HIV-1 envelope protein. We observed that M-tropic HIV-1 glycoprotein 120 (gp120) induces phosphorylation of the nonreceptor tyrosine kinase, Pyk2. Inhibition of Pyk2 activity using a pharmacologic inhibitor, kinase-inactive Pyk2 mutant, and Pyk2-specific small interfering RNA blocked gp120-induced chemotaxis, confirming the role of Pyk2 in iDC migration. In addition, we also illustrated the importance of Pyk2 in iDC migration induced by virion-associated envelope protein, using aldithriol-2-inactivated M-tropic HIV-1 virus. Further analysis of the downstream signaling mechanisms involved in gp120-induced migration revealed that Pyk2 activates p38 mitogen-activated protein kinase, which in turn activates the F-actin-binding protein, leukocyte-specific protein 1, and enhances its association with actin. Taken together, our studies provide an insight into a novel gp120-mediated pathway that regulates DC chemotaxis and contributes to the dissemination of HIV-1 within an infected person.

Lung vascular endothelial growth factor expression induces local myeloid dendritic cell activation

We previously demonstrated that vascular endothelial growth factor (VEGF) expression in the murine lung increases local CD11c+MHCII+ DC number and activation. In this study, employing a multicolor flow cytometry, we report increases in both myeloid (mDC) and plasmacytoid (pDC) DC in the lungs of VEGF transgenic (tg) compared to WT mice. Lung pDC from VEGF tg mice exhibited higher levels of activation with increased expression of MHCII and costimulatory molecules. As VEGF tg mice display an asthma-like phenotype and lung mDC play a critical role in asthmatic setting, studies were undertaken to further characterize murine lung mDC. Evaluations of sorted mDC from VEGF tg lungs demonstrated a selective upregulation of cathepsin K, MMP-8, -9, -12, and -14, and chemokine receptors as compared to those obtained from WT control mice. They also had increased VEGFR2 but downregulated VEGFR1 expression. Analysis of chemokine and regulatory cytokine expression in these cells showed an upregulation of macrophage chemotactic protein-3 (MCP-3), thymus-expressed chemokine (TECK), secondary lymphoid organ chemokine (SLC), macrophage-derived chemokine (MDC), IL-1beta, IL-6, IL-12 and IL-13. The antigen (Ag) OVA-FITC uptake by lung DC and the migration of Ag-loaded DC to local lymph nodes were significantly increased in VEGF tg mice compared to WT mice. Thus, VEGF may predispose the lung to inflammation and/or repair by activating local DC. It regulates lung mDC expression of innate immunity effector molecules. The data presented here demonstrate how lung VEGF expression functionally affects local mDC for the transition from the innate response to a Th2-type inflammatory response.

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.

Chemokine–chemokine receptors in cancer immunotherapy

A surge in interest in the chemokine–chemokine receptor network is probably related to the expanding roles that chemokines have now been identified to play in human biology, particularly immunity. Specific tissue microenvironments express distinct chemokines and both hematopoietic and nonhematopoietic cells have receptor expression profiles that permit the coordinated trafficking and organization of cells within these specific tissues. Since the chemokine network plays critical roles in both the function of the immune system and the progression of cancer, it is an attractive target for therapeutic manipulation. This review will focus on chemokine and chemokine receptor network-related therapeutic interventions that utilize host–tumor interactions particularly involving the immune system.