Chemokines: control of primary and memory T-cell traffic

Astragalus Polysaccharide Alleviates Ulcerative Colitis by Regulating the Balance of mTh17/mTreg Cells through TIGIT/CD155 Signaling

The balance between memory Th17 cells (mTh17) and memory Treg cells (mTreg) plays a key role in the pathogenesis of ulcerative colitis (UC), and TIGIT signaling is involved in the differentiation of mTh17/mTreg cells. Astragalus polysaccharide (APS) has good immunomodulatory and anti-inflammatory effects. Here, the regulatory effects and potential mechanisms of APS on mTh17/mTreg cells in UC are explored. A UC model was induced with dextran sulfate sodium (DSS) and treated simultaneously with APS (200 mg/kg/day) for 10 days. After APS treatment, the mice showed a significant increase in colonic length and a significant decrease in colonic weight, colonic weight index and colonic weight/colonic length, and more intact mucosa and lighter inflammatory cell infiltration. Notably, APS significantly down-regulated the percentages of Th17 (CD4+CCR6+), cmTh17 (CD4+CCR7+CCR6+) and emTh17 (CD4+CCR7-CCR6+) cells and significantly up-regulated the percentages of cmTreg (CD4+CCR7+Foxp3+) and emTreg (CD4+CCR7-Foxp3+) cells in the mesenteric lymph nodes of the colitis mice. Importantly, APS reversed the expression changes in the TIGIT molecule on mTh17/mTreg cells in the colitis mice with fewer CD4+CCR6+TIGIT+, CD4+CCR7-CCR6+TIGIT+ and CD4+CCR7-CCR6+TIGIT+ cells and more CD4+Foxp3+TIGIT+, CD4+CCR7-Foxp3+TIGIT+ and CD4+CCR7-Foxp3+TIGIT+ cells. Meanwhile, APS significantly inhibited the protein expression of the TIGIT ligands CD155, CD113 and CD112 and downstream proteins PI3K and AKT in the colon tissues of the colitis mice. In conclusion, APS effectively alleviated DSS-induced UC in mice by regulating the balance between mTh17/mTreg cells, which was mainly achieved through regulation of the TIGIT/CD155 signaling pathway.

Full eradication of pre-clinical human papilloma virus-induced tumors by a lentiviral vaccine

Human papillomavirus (HPV) infections are the cause of all cervical and numerous oropharyngeal and anogenital cancers. The currently available HPV vaccines, which induce neutralizing antibodies, have no therapeutic effect on established tumors. Here, we developed an immuno-oncotherapy against HPV-induced tumors based on a non-integrative lentiviral vector encoding detoxified forms of the Early E6 and E7 oncoproteins of HPV16 and 18 genotypes, namely, "Lenti-HPV-07". A single intramuscular injection of Lenti-HPV-07 into mice bearing established HPV-induced tumors resulted in complete tumor eradication in 100% of the animals and was also effective against lung metastases. This effect correlated with CD8+ T-cell induction and profound remodeling of the tumor microenvironment. In the intra-tumoral infiltrates of vaccinated mice, the presence of large amounts of activated effector, resident memory, and transcription factor T cell factor-1 (TCF-1)+ "stem-like" CD8+ T cells was associated with full tumor eradication. The Lenti-HPV-07-induced immunity was long-lasting and prevented tumor growth after a late re-challenge, mimicking tumor relapse. Lenti-HPV-07 therapy synergizes with an anti-checkpoint inhibitory treatment and therefore shows promise as an immuno-oncotherapy against established HPV-mediated malignancies.

Two CcCCL19bs orchestrate an antibacterial immune response in Yellow River carp (Cyprinus carpio haematopterus)

Chemokines are a group of chemotactic cytokines with an essential role in homeostasis as well as immunity via specific G protein-coupled receptors and atypical receptors. In our study, two Yellow River carp (Cyprinus carpio haematopterus) CCL19b genes (CcCCL19bs), tentatively named CcCCL19b_a and CcCCL19b_b, were cloned. The open reading frames (ORFs) of CcCCL19b_a and CcCCL19b_b were both 333 bp that encoded a 12 kDa protein with 110 amino acid residues. CcCCL19bs contained a signal peptide and a SCY domain with four typical conserved cysteine residues. The two CcCCL19b proteins shared high similarities with each other in both secondary and three-dimensional structure. Phylogenetic analysis showed that CcCCL19bs and other CCL19bs from tetraploid cyprinid fish were clustered into one clade. CcCCL19bs were highly expressed in gill and intestine in healthy fish, and a significant up-regulation of gene expression after Aeromonas hydrophila infection and poly(I:C) stimulation was observed in gill, liver, and head kidney. Furthermore, chemotaxis and antibacterial activity of CcCCL19bs were studied. The results indicated that recombinant CcCCL19b_a and CcCCL19b_b protein (rCcCCL19b_a and rCcCCL19b_b) exhibited significant attraction to primary head kidney leukocytes (HKLs). Meanwhile, both of rCcCCL19bs could promote the proliferation of HKLs, and significantly up-regulate the expressions of IL-1β, CCR7, and IL-6, and down-regulate the expression of IL-10 in primary HKLs. In vitro, rCcCCL19bs could bind and aggregate A. hydrophila and Staphylococcus aureus. The rCcCCL19bs exhibited significant antibacterial activity against A. hydrophila, but not S. aureus. Moreover, they inhibited the growth of A. hydrophila and S. aureus. In vivo, overexpression of CcCCL19bs contributed to the bacterial clearance. These studies suggested that CcCCL19bs orchestrate an antibacterial immune response.

The cryptic role of CXCL17/CXCR8 axis in the pathogenesis of cancers: a review of the latest evidence

Chemokines are immune system mediators that mediate various activities and play a role in the pathogenesis of several cancers. Among these chemokines, C-X-C motif chemokine 17 (CXCL-17) is a relatively novel molecule produced along the airway epithelium in physiological and pathological conditions, and evidence shows that it plays a homeostatic role in most cases. CXCL17 has a protective role in some cancers and a pathological role in others, such as liver and lung cancer. This chemokine, along with its possible receptor termed G protein-coupled receptor 35 (GPR35) or CXCR8, are involved in recruiting myeloid cells, regulating angiogenesis, defending against pathogenic microorganisms, and numerous other mechanisms. Considering the few studies that have been performed on the dual role of CXCL17 in human malignancies, this review has investigated the possible pro-tumor and anti-tumor roles of this chemokine, as well as future treatment options in cancer therapy.

A2Ar-dependent PD-1+ and TIGIT+ Treg cells have distinct homing requirements to suppress autoimmune uveitis in mice

The proper function of regulatory T cells (Tregs) to suppress inflammation requires homing to the correct tissue site. Resolution of autoimmune uveitis generates distinct programmed death receptor 1 (PD-1+) and T-cell immunoreceptor with immunoglobulin and immunoreceptor tyrosine-based inhibitory motif domains (TIGIT+) Tregs in an adenosine 2A receptor (A2Ar)-dependent manner found in the spleen. Where and how these Tregs migrate from the spleen to prevent uveitis is not known. In this work, we show that A2Ar-dependent Tregs migrated to the eye and secondary lymphoid tissue and expressed chemokine receptor (CCR)6 and CCR7. Suppression of autoimmune uveitis required CCR6 and CCR7 expression for TIGIT+ Tregs but not PD-1+ Tregs. Moreover, stimulation of A2Ar on T cells from patients showed a decreased capacity to induce TIGIT+ Tregs that expressed CCR6 or CCR7, and PD-1+ Treg that expressed CCR6. This work provides a mechanistic understanding of the homing requirements of each of these Treg populations. Importantly, this work is clinically relevant because patients with chronic autoimmune uveitis are unable to induce the Treg populations identified in mice that home to the target tissue.

Molecular characterization and expression patterns of CXCL8 gene from blunt snout bream (Megalobrama amblycephala) and its chemotactic effects on macrophages and neutrophils

CXCL8 is a typical CXC-type chemokine, which mediates the migration of immune cells from blood vessels to the site of inflammation or injury to clear pathogenic microorganisms and repair damaged tissues. In this study, Megalobrama amblycephala CXCL8 (MaCXCL8) gene was identified and characterized. Sequence analysis showed that the deduced MaCXCL8 protein possessed the typical structure of CXCL8 from other species, with the characteristic CXC cysteine residues in the N-terminal and accompanied by a DLR motif (Asp-Leu-Arg motif). Phylogenetic analysis revealed that MaCXCL8 was homologous to that of Ctenopharyngodon idella and other cyprinid fishes. MaCXCL8 gene was expressed in all detected healthy tissues, with the highest expression levels in the spleen, and its expression was significantly up-regulated upon the challenge of Aeromonas hydrophila and Lipopolysaccharide (LPS) both in juvenile M. amblycephala tissues and primary macrophages. The immunohistochemical assay showed that MaCXCL8 was mainly distributed in the nucleus and cytoplasm, and its expression levels increased observably with the prolongation of bacterial infection. In addition, recombinant MaCXCL8 protein exhibited significant chemotactic effects on neutrophils and macrophages. In conclusion, MaCXCL8 is involved in the immune response of M. amblycephala, and these findings will be helpful to understand the biological roles of MaCXCL8 and provide a theoretical basis for the prevention and control of fish bacterial diseases.

The endothelial diapedesis synapse regulates transcellular migration of human T lymphocytes in a CX3CL1- and SNAP23-dependent manner

Understanding how cytotoxic T lymphocytes (CTLs) efficiently leave the circulation to target cancer cells or contribute to inflammation is of high medical interest. Here, we demonstrate that human central memory CTLs cross the endothelium in a predominantly paracellular fashion, whereas effector and effector memory CTLs cross the endothelium preferably in a transcellular fashion. We find that effector CTLs show a round morphology upon adhesion and induce a synapse-like interaction with the endothelium where ICAM-1 is distributed at the periphery. Moreover, the interaction of ICAM-1:β2integrin and endothelial-derived CX3CL1:CX3CR1 enables transcellular migration. Mechanistically, we find that ICAM-1 clustering recruits the SNARE-family protein SNAP23, as well as syntaxin-3 and -4, for the local release of endothelial-derived chemokines like CXCL1/8/10. In line, silencing of endothelial SNAP23 drives CTLs across the endothelium in a paracellular fashion. In conclusion, our data suggest that CTLs trigger local chemokine release from the endothelium through ICAM-1-driven signals driving transcellular migration.

CCL19 and CCL28 Assist Herpes Simplex Virus 2 Glycoprotein D To Induce Protective Systemic Immunity against Genital Viral Challenge

An effective HSV-2 vaccine should induce antigen (Ag)-specific immune responses against viral mucosal infection. This study reveals that chemokine CCL19 or CCL28 enhanced HSV-2 glycoprotein D ectodomain (gD-306aa)-induced immune responses against vaginal virus challenge.

Potent systemic immunity is important for recalled mucosal immune responses, but in the defense against mucosal viral infections, it usually remains low at mucosal sites. Based on our previous findings that enhanced immune responses can be achieved by immunization with an immunogen in combination with a molecular adjuvant, here we designed chemokine-antigen (Ag) fusion constructs (CCL19- or CCL28-herpes simplex virus 2 glycoprotein D [HSV-2 gD]). After intramuscular (i.m.) immunization with different DNA vaccines in a prime and boost strategy, BALB/c mice were challenged with a lethal dose of HSV-2 through the genital tract. Ag-specific immune responses and chemokine receptor-specific lymphocytes were analyzed to determine the effects of CCL19 and CCL28 in strengthening humoral and cellular immunity. Both CCL19 and CCL28 were efficient in inducing long-lasting HSV-2 gD-specific systemic immunity. Compared to CCL19, less CCL28 was required to elicit HSV-2 gD-specific serum IgA responses, Th1- and Th2-like responses of immunoglobulin (Ig) subclasses and cytokines, and CCR3⁺ T cell enrichment (>8.5-fold) in spleens. These findings together demonstrate that CCL28 tends to assist an immunogen to induce more potently protective immunity than CCL19. This work provides information for the application potential of a promising vaccination strategy against mucosal infections caused by HSV-2 and other sexually transmitted viruses.

IMPORTANCE An effective HSV-2 vaccine should induce antigen (Ag)-specific immune responses against viral mucosal infection. This study reveals that chemokine CCL19 or CCL28 enhanced HSV-2 glycoprotein D ectodomain (gD-306aa)-induced immune responses against vaginal virus challenge. In addition to eliciting robust humoral immune responses, the chemokine-Ag fusion construct also induced Th1- and Th2-like immune responses characterized by the secretion of multiple Ig subclasses and cytokines that were able to be recalled after HSV-2 challenge, while CCL28 appeared to be more effective than CCL19 in promoting gD-elicited immune responses as well as the migration of T cells to secondary lymph tissues. Of importance, both CCL19 and CCL28 significantly facilitated gD to induce protective mucosal immune responses in the genital tract. The above-described findings together highlight the potential of CCL19 or CCL28 in combination with gD as a vaccination strategy to control HSV-2 infection.

Peripheral Blood Biomarkers CXCL12 and TNFRSF13C Associate with Cerebrospinal Fluid Biomarkers and Infiltrating Immune Cells in Alzheimer Disease

Neuroinflammation-induced neurodegeneration and immune cell infiltration are two features of Alzheimer disease (AD). This study aimed to identify potential peripheral biomarkers that interact with cerebrospinal fluid (CSF) and infiltrating immune cells in AD. Blood and CSF data were downloaded from the Alzheimer's disease Neuroimaging Initiative database. We identified differentially expressed genes (DEGs) in AD and assessed infiltrating immune cells using the Immune Cell Abundance Identifier (ImmuCellAI) algorithm. Blood-brain barrier (BBB) and immune-related genes were identified from medical databases, and common genes were used to construct a protein-protein interaction network (PPI). Potential biomarkers reflecting the clinical features of AD were screened using Pearson correlations and logistic regression analysis. We identified 210 DEGs in the AD group. ImmuCellAI indicated that blood samples from patients with AD had a higher abundance of exhausted T (Tex; 0.196 vs. 0.132) and induced regulatory T (iTreg; 0.180 vs. 0.137) cells than controls. Thirty-two genes overlapped between the BBB and immune-related genes, and 27 genes in the PPI network were associated with eight pathways, including the cytokine-cytokine receptor interaction pathway (hsa04060) and the chemokine signaling pathway (hsa04062). Pearson correlations showed that five genes were associated with the CSF biomarkers, Aβ, total, and phosphorylated tau. Logistics analysis showed that the B cell-associated genes, CXCL12 and TNFRSF13C, were independent risk factors for AD diagnosis. Peripheral CXCL12 and TNFRSF13C genes that correlated with immune cell infiltration in AD might serve as easily accessible biomarkers for the early diagnosis of AD.

CCL19 enhances CD8+ T-cell responses and accelerates HBV clearance

BACKGROUND

Chemokine (C-C motif) ligand 19 (CCL19) is a leukocyte chemoattractant that plays a crucial role in cell trafficking and leukocyte activation. Dysfunctional CD8⁺ T cells play a crucial role in persistent HBV infection. However, whether HBV can be cleared by CCL19-activated immunity remains unclear.

METHODS

We assessed the effects of CCL19 on the activation of PBMCs in patients with HBV infection. We also examined how CCL19 influences HBV clearance and modulates HBV-responsive T cells in a mouse model of chronic hepatitis B (CHB). In addition, C-C chemokine-receptor type 7 (CCR7) knockdown mice were used to elucidate the underlying mechanism of CCL19/CCR7 axis-induced immune activation.

RESULTS

From in vitro experiments, we found that CCL19 enhanced the frequencies of Ag-responsive IFN-γ⁺ CD8⁺ T cells from patients by approximately twofold, while CCR7 knockdown (LV-shCCR7) and LY294002 partially suppressed IFN-γ secretion. In mice, CCL19 overexpression led to rapid clearance of intrahepatic HBV likely through increased intrahepatic CD8⁺ T-cell proportion, decreased frequency of PD-1⁺ CD8⁺ T cells in blood and compromised suppression of hepatic APCs, with lymphocytes producing a significantly high level of Ag-responsive TNF-α and IFN-γ from CD8⁺ T cells. In both CCL19 over expressing and CCR7 knockdown (AAV-shCCR7) CHB mice, the frequency of CD8⁺ T-cell activation-induced cell death (AICD) increased, and a high level of Ag-responsive TNF-α and low levels of CD8⁺ regulatory T (T_reg) cells were observed.

CONCLUSIONS

Findings in this study provide insights into how CCL19/CCR7 axis modulates the host immune system, which may promote the development of immunotherapeutic strategies for HBV treatment by overcoming T-cell tolerance.

Chemokine expression profiles in liver and kidney of mice with different susceptibilities to leptospirosis

Leptospirosis is a global disease that affects humans and animals, impacting public health and the economy. The symptoms caused by Leptospira infection can vary from mild to severe, affecting liver, lungs, and kidneys. The host-pathogen interaction in leptospirosis is still poorly understood, but there is evidence for the role of the host immune response in the pathogenesis. Chemokines are a family of structurally-related low-molecular-mass proteins (8-14 kDa) that signal the recruitment of leukocytes. In this study the profile of 22 chemokines were evaluated in liver and kidney of three mice strains with different phenotypes of susceptibility to leptospirosis. We extended our previously reported observations showing that expression of chemokines with homeostatic function, activation and chemotaxis of leukocytes are essential to modulate and to induce resistance to leptospirosis. Our findings support that an early induction of CXC chemokines in resistant BALB/c mice can be associated with the control of the infection. The correlation of chemokine expression between liver and kidney observed in BALB/c suggests that a balance of chemokine induction in the organs may contribute to resistance to leptospirosis.

CCL19 and CCR7 Expression, Signaling Pathways, and Adjuvant Functions in Viral Infection and Prevention

Chemokine (C–C motif) ligand 19 (CCL19) is a critical regulator of the induction of T cell activation, immune tolerance, and inflammatory responses during continuous immune surveillance, homeostasis, and development. Migration of CC-chemokine receptor 7 (CCR7)-expressing cells to secondary lymphoid organs is a crucial step in the onset of adaptive immunity, which is initiated by a complex interaction between CCR7 and its cognate ligands. Recent advances in knowledge regarding the response of the CCL19-CCR7 axis to viral infections have elucidated the complex network of interplay among the invading virus, target cells and host immune responses. Viruses use various strategies to evade or delay the cytokine response, gaining additional time to replicate in the host. In this review, we summarize the impacts of CCL19 and CCR7 expression on the regulation of viral pathogenesis with an emphasis on the corresponding signaling pathways and adjuvant mechanisms. We present and discuss the expression, signaling adaptor proteins and effects of CCL19 and CCR7 as these molecules differentially impact different viral infections and viral life cycles in host homeostatic strategies. The underlying mechanisms discussed in this review may assist in the design of novel agents to modulate chemokine activity for viral prevention.

Estimating Residence Times of Lymphocytes in Ovine Lymph Nodes

The ability of lymphocytes to recirculate between blood and secondary lymphoid tissues such as lymph nodes (LNs) and spleen is well established. Sheep have been used as an experimental system to study lymphocyte recirculation for decades and multiple studies document accumulation and loss of intravenously (i.v.) transferred lymphocytes in efferent lymph of various ovine LNs. Yet, surprisingly little work has been done to accurately quantify the dynamics of lymphocyte exit from the LNs and to estimate the average residence times of lymphocytes in ovine LNs. In this work we developed a series of mathematical models based on fundamental principles of lymphocyte recirculation in the body under non-inflammatory (resting) conditions. Our analysis suggested that in sheep, recirculating lymphocytes spend on average 3 h in the spleen and 20 h in skin or gut-draining LNs with a distribution of residence times in LNs following a skewed gamma (lognormal-like) distribution. Our mathematical models also suggested an explanation for a puzzling observation of the long-term persistence of i.v. transferred lymphocytes in the efferent lymph of the prescapular LN (pLN); the model predicted that this is a natural consequence of long-term persistence of the transferred lymphocytes in circulation. We also found that lymphocytes isolated from the skin-draining pLN have a 2-fold increased entry rate into the pLN as opposed to the mesenteric (gut-draining) LN (mLN). Likewise, lymphocytes from mLN had a 3-fold increased entry rate into the mLN as opposed to entry rate into pLN. In contrast, these cannulation data could not be explained by preferential retention of cells in LNs of their origin. Taken together, our work illustrates the power of mathematical modeling in describing the kinetics of lymphocyte migration in sheep and provides quantitative estimates of lymphocyte residence times in ovine LNs.

Differential Cytokine Utilization and Tissue Tropism Results in Distinct Repopulation Kinetics of Naïve vs. Memory T Cells in Mice

Naïve and memory T cells co-exist in the peripheral T cell pool, but the cellular mechanisms that maintain the balance and homeostasis of these two populations remain mostly unclear. To address this question, here, we assessed homeostatic proliferation and repopulation kinetics of adoptively transferred naïve and memory T cells in lymphopenic host mice. We identified distinct kinetics of proliferation and tissue-distribution between naïve and memory donor T cells, which resulted in the occupancy of the peripheral T cell pool by mostly naïve-origin T cells in short term (<1 week), but, in a dramatic reversal, by mostly memory-origin T cells in long term (>4 weeks). To explain this finding, we assessed utilization of the homeostatic cytokines IL-7 and IL-15 by naïve and memory T cells. We found different efficiencies of IL-7 signaling between naïve and memory T cells, where memory T cells expressed larger amounts of IL-7Rα but were significantly less potent in activation of STAT5 that is downstream of IL-7 signaling. Nonetheless, memory T cells were superior in long-term repopulation of the peripheral T cell pool, presumably, because they preferentially migrated into non-lymphoid tissues upon adoptive transfer and additionally utilized tissue IL-15 for rapid expansion. Consequently, co-utilization of IL-7 and IL-15 provides memory T cells a long-term survival advantage. We consider this mechanism important, as it permits the memory T cell population to be maintained in face of constant influx of naïve T cells to the peripheral T cell pool and under competing conditions for survival cytokines.

Origin, function and role in the development of skin diseases CLA+T-lymphocytes

The idea of CLA+T-lymphocytes, which are a special subpopulation of cells with a tropic to the skin, is given. The issues of maturation, migration and functional features of CLA+T-cells are considered. Special attention is paid to the different phenotype of memory T-cells. Modern data concerning the role of CLA+T-cells in the pathogenesis of autoimmune and allergic dermatoses, as well as malignant skin tumors are also presented. The conclusion about the necessity of further study of CLA +T-lymphocytes for detailed understanding of pathogenesis and search of variants of targeted therapy in psoriasis, atopic dermatitis, skin lymphomas and other skin diseases is made.

Selective Expression of CCR10 and CXCR3 by Circulating Human Herpes Simplex Virus-Specific CD8 T Cells

Herpes simplex virus (HSV) infection is restricted to epithelial cells and neurons and is controlled by CD8 T cells. These cells both traffic to epithelial sites of recurrent lytic infection and to ganglia and persist at the dermal-epidermal junction for up to 12 weeks after lesion resolution. We previously showed that cutaneous lymphocyte-associated antigen (CLA), a functional E-selectin ligand (ESL), is selectively expressed on circulating HSV-2-specific CD8 T cells. CLA/ESL mediates adhesion of T cells to inflamed vascular endothelium. Later stages in T-cell homing involve chemokines (Ch) and lymphocyte chemokine receptors (ChR) for vascular wall arrest and diapedesis. Several candidate ChR have been implicated in skin homing. We measured cell surface ChR on HSV-specific human peripheral blood CD8 T cells and extended our studies to HSV-1. We observed preferential cell surface expression of CCR10 and CXCR3 by HSV-specific CD8 T cells compared to CD8 T cells specific for control viruses, Epstein-Barr virus (EBV) and cytomegalovirus (CMV), and compared to bulk memory CD8 T cells. CXCR3 ligand mRNA levels were selectively increased in skin biopsy specimens from persons with recurrent HSV-2, while the mRNA levels of the CCR10 ligand CCL27 were equivalent in lesion and control skin. Our data are consistent with a model in which CCL27 drives baseline recruitment of HSV-specific CD8 T cells expressing CCR10, while interferon-responsive CXCR3 ligands recruit additional cells in response to virus-driven inflammation.IMPORTANCE HSV-2 causes very localized recurrent infections in the skin and genital mucosa. Virus-specific CD8 T cells home to the site of recurrent infection and participate in viral clearance. The exit of T cells from the blood involves the use of chemokine receptors on the T-cell surface and chemokines that are present in infected tissue. In this study, circulating HSV-2-specific CD8 T cells were identified using specific fluorescent tetramer reagents, and their expression of several candidate skin-homing-associated chemokine receptors was measured using flow cytometry. We found that two chemokine receptors, CXCR3 and CCR10, are upregulated on HSV-specific CD8 T cells in blood. The chemokines corresponding to these receptors are also expressed in infected tissues. Vaccine strategies to prime CD8 T cells to home to HSV lesions should elicit these chemokine receptors if possible to increase the homing of vaccine-primed cells to sites of infection.

T Lymphocytes and Inflammatory Mediators in the Interplay between Brain and Blood in Alzheimer's Disease: Potential Pools of New Biomarkers

Alzheimer's disease (AD) is a chronic neurodegenerative disorder and the main cause of dementia. The disease is among the leading medical concerns of the modern world, because only symptomatic therapies are available, and no reliable, easily accessible biomarkers exist for AD detection and monitoring. Therefore extensive research is conducted to elucidate the mechanisms of AD pathogenesis, which seems to be heterogeneous and multifactorial. Recently much attention has been given to the neuroinflammation and activation of glial cells in the AD brain. Reports also highlighted the proinflammatory role of T lymphocytes infiltrating the AD brain. However, in AD molecular and cellular alterations involving T cells and immune mediators occur not only in the brain, but also in the blood and the cerebrospinal fluid (CSF). Here we review alterations concerning T lymphocytes and related immune mediators in the AD brain, CSF, and blood and the mechanisms by which peripheral T cells cross the blood brain barrier and the blood-CSF barrier. This knowledge is relevant for better AD therapies and for identification of novel biomarkers for improved AD diagnostics in the blood and the CSF. The data will be reviewed with the special emphasis on possibilities for development of AD biomarkers.

Apocynin inhibits Toll-like receptor-4-mediated activation of NF-κB by suppressing the Akt and mTOR pathways

Microbial product lipopolysaccharide has been shown to be involved in the pathogenesis of inflammatory skin diseases. Apocynin has demonstrated to have an anti-inflammatory effect. However, the effect of apocynin on the Toll-like receptor-4-dependent activation of Akt, mammalian target of rapamycin (mTOR), and nuclear factor (NF)-κB pathway, which is involved in productions of inflammatory mediators in keratinocytes, has not been studied. Using human keratinocytes, we investigated the effect of apocynin on the inflammatory mediator production in relation to the Toll-like receptor-4-mediated-Akt/mTOR and NF-κB pathways, which regulates the transcription genes involved in immune and inflammatory responses. Apocynin, Akt inhibitor SH-5, Bay 11-7085 and N-acetylcysteine each attenuated the lipopolysaccharide-induced production of cytokines, PGE₂, and chemokines, changes in the levels of Toll-like receptor-4, p-Akt, mTOR, and NF-κB, and production of reactive oxygen species in keratinocytes. The results show that apocynin appears to attenuate the lipopolysaccharide-stimulated production of inflammatory mediators in keratinocytes by suppressing the Toll-like receptor-4-mediated activation of the Akt, mTOR, and NF-κB pathways. The effect of apocynin appears to be attributed to its inhibitory effect on the production of reactive oxygen species. Apocynin appears to attenuate the microbial product-mediated inflammatory skin diseases.

Flavonoid myricetin inhibits TNF-α-stimulated production of inflammatory mediators by suppressing the Akt, mTOR and NF-κB pathways in human keratinocytes

Flavonoid myricetin has been shown to exhibit anti-inflammatory and anti-oxidant effects. Nevertheless, the effect of myricetin on the TNF-α-stimulated production of inflammatory mediators in keratinocytes has not been studied. Using human keratinocytes, we examined the effect of myricetin on the TNF-α-stimulated production of inflammatory mediators in relation to the Akt, mTOR and NF-κB pathways, which regulate the transcription genes involved in immune and inflammatory responses. TNF-α stimulated production of the inflammatory mediators and reactive oxygen species in keratinocytes, and activation of the Akt, mTOR and NF-κB pathways in HaCaT cells and primary keratinocytes. Myricetin, Akt inhibitor, Bay 11-7085 (an inhibitor of NF-κB activation), rapamycin (mTOR inhibitor) and N-acetylcysteine attenuated TNF-α-induced activation of Akt, mTOR and NF-κB. Myricetin and N-acetylcysteine attenuated the TNF-α-stimulated production of cytokines and chemokines, and production of reactive oxygen species in keratinocytes. The results show that myricetin may reduce TNF-α-stimulated inflammatory mediator production in keratinocytes by suppressing the activation of the Akt, mTOR and NF-κB pathways. The effect of myricetin appears to be associated with inhibition of the production of reactive oxygen species. Further, myricetin appears to attenuate the proinflammatory mediator-induced inflammatory skin diseases.

Follicular helper T cell-mediated mucosal barrier maintenance

The basic functions of the immune system are protection from pathogens and maintenance of tolerance to self. The maintenance of commensal microbiota at mucosal surfaces adds a layer of complexity to these basic functions. Recent reports suggest follicular helper T cells (Tfh), a CD4(+) T cell subset specialized to provide help to B cells undergoing isotype switching and affinity maturation in germinal centers (GC), interact with the microbiota and are essential to maintenance of mucosal barriers. Complicating the issue is ongoing controversy in the field regarding origin of the Tfh subset and its distinction from other effector CD4 T cell phenotypes (Th1/Th17/Treg). This review focuses on the differentiation, phenotypic plasticity, and function of CD4 T cells, with an emphasis on commensal-specific GC responses in the gut.

Peripheral and site-specific CD4(+) CD28(null) T cells from rheumatoid arthritis patients show distinct characteristics

Proinflammatory CD4(+) CD28(null) T cells are frequently found in the circulation of patients with rheumatoid arthritis (RA), but are less common in the rheumatic joint. In the present study, we sought to identify functional differences between CD4(+) CD28(null) T cells from blood and synovial fluid in comparison with conventional CD28-expressing CD4(+) T cells. Forty-four patients with RA, displaying a distinct CD4(+) CD28(null) T cell population in blood, were recruited for this study; the methylation status of the IFNG locus was examined in isolated T cell subsets, and intracellular cytokine production (IFN-γ, TNF, IL-17) and chemokine receptor expression (CXCR3, CCR6 and CCR7) were assessed by flow cytometry on T cells from the two compartments. Circulating CD4(+) CD28(null) T cells were significantly more hypomethylated in the CNS-1 region of the IFNG locus than conventional CD4(+) CD28(+) T cells and produced higher levels of both IFN-γ and TNF after TCR cross-linking. CD4(+) CD28(null) T cells from the site of inflammation expressed significantly more CXCR3 and CCR6 compared to their counterparts in blood. While IL-17A production could hardly be detected in CD4(+) CD28(null) cells from the blood, a significant production was observed in CD4(+) CD28(null) T cells from synovial fluid. CD4(+) CD28(null) T cells were not only found to differ from conventional CD4(+) CD28(+) T cells in the circulation, but we could also demonstrate that synovial CD4(+) CD28(null) T cells showed additional effector functions (IL-17 coproduction) as compared to the same subset in peripheral blood, suggesting an active role for these cells in the perpetuation of inflammation in the subset of patients having a CD28(null) population.

Lung disease, T-cells and inflammation in common variable immunodeficiency disorders

INTRODUCTION

Besides hypogammaglobulinemia and recurrent infections, abnormalities of T-cells might contribute to lung damage in common variable immunodeficiency disorders (CVID).

MATERIALS AND METHODS

In 16 adult patients, the majority of whom had pulmonary abnormalities, we studied T-cell subsets and markers of inflammation in bronchoalveolar lavage fluid (BALF) and blood and their relations with pulmonary function and high resolution computed tomography (HRCT).

RESULTS

We demonstrated that some of the lymphocyte abnormalities previously demonstrated in peripheral blood from CVID patients, such as low CD4/CD8 T-cell ratio, were also present in BALF. Moreover, low BALF CD4/CD8 ratio (≤ 1), found in seven patients, was significantly associated with higher blood CD8⁺ cell count and to lower values of the lung function variables; forced expiratory volume (FVC), total lung capacity (TLC), vital capacity (VC) and residual volume (RV) in % of predicted. The expression of the inflammatory markers HLA-DR and CCR5 on T-cells was significantly higher, and the expression of CCR7 significantly lower, in BALF compared to blood, possibly reflecting an inflammatory/cytotoxic T-cell phenotype within pulmonary tissue in CVID. Furthermore, patients with bronchiectasis had higher concentrations of the pro-inflammatory cytokine TNFα in plasma, compared to those without.

CONCLUSION

Our findings suggest that inflammation and T-cell activation may be involved in the immunopathogenesis of pulmonary complications in CVID.

Targeting cells in motion: migrating toward improved therapies

The development of clinical therapeutics that interfere with the migration of leukocytes has revolutionized the treatment of multiple sclerosis and holds great promise for the treatment of a wide range of inflammatory diseases. As the molecules essential for the multi-step adhesion cascade that mediates cellular migration have been elucidated, the number of potential targets available to modulate leukocyte trafficking has increased exponentially. In this Viewpoint, we briefly review our current understanding of these mole-cular targets and how these targets vary by tissue and leukocyte subset with emphasis on T cells. We then describe the two currently approved therapeutics that target cell migration, natalizumab and fingolimod, and discuss how an improved understanding of their function could pave the way for the development of safer and more efficacious therapies for inflammatory and autoimmune diseases.

Skin- and gut-homing molecules on human circulating γδ T cells and their dysregulation in inflammatory bowel disease

Changes in phenotype and function of γδ T cells have been reported in inflammatory bowel disease (IBD), including Crohn's disease (CD) and ulcerative colitis (UC). Dysregulation of lymphocyte migration plays a key role in IBD pathogenesis; however, data on migratory properties of γδ T cells are scarce. Human circulating γδ T cells from healthy controls (n = 27), patients with active CD (n = 15), active UC (n = 14) or cutaneous manifestations of IBD (n = 2) were characterized by flow cytometry. Circulating γδ T cells in healthy controls were CD3(hi) and expressed CD45RO. They expressed gut-homing molecule β7 but not gut-homing molecule corresponding chemokine receptors (CCR)9, or skin-homing molecules cutaneous lymphocyte-associated antigen (CLA) and CCR4, despite conventional T cells containing populations expressing these molecules. CCR9 expression was increased on γδ T cells in CD and UC, while skin-homing CLA was expressed aberrantly on γδ T cells in patients with cutaneous manifestations of IBD. Lower levels of CD3 expression were found on γδ T cells in CD but not in UC, and a lower proportion of γδ T cells expressed CD45RO in CD and UC. Enhanced expression of gut-homing molecules on circulating γδ T cells in IBD and skin-homing molecules in cutaneous manifestations of IBD may be of clinical relevance.

Chemokine-based immunotherapy: delivery systems and combination therapies

A major role of chemokines is to mediate leukocyte migration through interaction with G-protein-coupled receptors. Various delivery systems have been developed to utilize the chemokine properties for combating disease. Viral and mutant viral vectors expressing chemokines, genetically modified dendritic cells with chemokine or chemokine receptors, engineered chemokine-expressing tumor cells and pDNA encoding chemokines are among these methods. Another approach for inducing a targeted immune response is fusion of a targeting antibody or antibody fragment to a chemokine. In addition, chemokines induce more effective antitumor immunity when used as adjuvants. In this regard, chemokines are codelivered along with antigens or fused as a targeting unit with antigenic moieties. In this review, several chemokines with their role in inducing immune response against different diseases are discussed, with a major emphasis on cancer.

Elevated pretreatment serum levels of interferon-inducible protein-10 (CXCL10) predict disease relapse and prognosis in diffuse large B-cell lymphoma patients

Although standard clinical prognostic factors predict outcome in diffuse large B-cell lymphoma (DLBCL), predicting the outcome of patients might be further refined using biological factors. We tested whether serum cytokines could provide prognostic information in DLBCL patients. Thirty cytokines were measured in pretreatment samples from newly diagnosed DLBCL patients using a multiplex ELISA. Sixty-nine patients treated with R-CHOP plus epratuzumab were used in an initial cohort and 185 patients treated with standard R-CHOP served as a subsequent validation cohort. In the initial cohort, elevated serum interleukin-10 [IL-10; hazard ratio (HR) = 6.6, P = 0.022], granulocyte macrophage colony-stimulating factor (HR = 10.8, P= 0.027) and IP-10 (interferon-inducible protein-10, CXCL10; HR = 3.32, P = 0.015) were associated with event-free survival (EFS). An identical analysis of the subsequent validation cohort confirmed that elevated serum levels of IP-10 were strongly associated with a poor EFS (HR = 2.42, P = 0.0007); and also identified interleukin-8 (IL-8; HR = 3.40, P = 0.00002) and interleukin-2 receptor (IL-2R, CD25; HR = 2.59, P = 0.0012) as significantly associated with prognosis. The prognostic significance of elevated IP-10 remained significant after adjustment for the International Prognostic Index (EFS - HR 1.99, P = 0.009, overall survival-HR 1.93, P = 0.021). Elevated pretreatment serum IP-10 levels are therefore associated with an increased likelihood of disease relapse and an inferior survival in patients with DLBCL.

Chemokine-dependent T cell migration requires aquaporin-3-mediated hydrogen peroxide uptake

The water/glycerol channel aquaporin-3 is required for chemokine-dependent T cell migration during immune responses.

Chemokine-dependent trafficking is indispensable for the effector function of antigen-experienced T cells during immune responses. In this study, we report that the water/glycerol channel aquaporin-3 (AQP3) is expressed on T cells and regulates their trafficking in cutaneous immune reactions. T cell migration toward chemokines is dependent on AQP3-mediated hydrogen peroxide (H₂O₂) uptake but not the canonical water/glycerol transport. AQP3-mediated H₂O₂ transport is essential for the activation of the Rho family GTPase Cdc42 and the subsequent actin dynamics. Coincidentally, AQP3-deficient mice are defective in the development of hapten-induced contact hypersensitivity, which is attributed to the impaired trafficking of antigen-primed T cells to the hapten-challenged skin. We therefore suggest that AQP3-mediated H₂O₂ uptake is required for chemokine-dependent T cell migration in sufficient immune response.

Loss of CD127 & increased immunosenescence of T cell subsets in HIV infected individuals

Background & objectives:

HIV infection is characterized by a perturbation in T cell homeostasis, leading to alteration in T cell subsets. In addition to alteration in differentiation, HIV infection also leads to change in T cell survival and regenerative capacity, as suggested by differential expression of CD127 and CD57. We evaluated the expression patterns of CD127 and CD57 on CD4 and CD8 effector, memory and naïve T cell subsets in HIV-infected and uninfected individuals.

Methods:

We characterized T cell subsets based on expression of these markers, and compared their expression pattern in HIV infected subjects and uninfected controls. We further assessed therapy generated changes in these subsets and expression of CD127 and CD57 on them.

Results:

There was a generalized decrease in naïve CD4 and CD8 T cells in HIV infected subjects. These changes in T cell subset distribution were related to antigen load. CD127 expression was significantly reduced in T cells from HIV infected subject. In association to this, HIV infected subjects had higher percentage of T cell subsets expressing CD57. Increased CD57 and reduced CD127 expression correlated with plasma viraemia and CD8 T cell activation state. Incomplete restoration of T cell subset proportions was observed, despite suppression of viral replication and increase in CD4 T cell counts. Further, the improvement was more pronounced in CD127 expression.

Interpretation & conclusions:

HIV infected subjects have reduced T cell regenerative capacity along with increased senescence, highlighting decreased proliferation and effector activities.

CCR9+ T cells contribute to the resolution of the inflammatory response in a mouse model of intestinal amoebiasis

Analysis of the mechanisms underlying the inflammatory response in amoebiasis is important to understand the immunopathology of the disease. Mucosal associated effector and regulatory T cells may play a role in regulating the inflammatory immune response associated to Entamoeba histolytica infection in the colon. A subpopulation of regulatory T cells has recently been identified and is characterized by the expression of the chemokine receptor CCR9. In this report, we used CCR9 deficient (CCR9(-/-)) mice to investigate the role of the CCR9(+) T cells in a murine model of E. histolytica intestinal infection. Intracecal infection of CCR9(+/+), CCR9(+/-) and CCR9(-/-) mice with E. histolytica trophozoites, revealed striking differences in the development and nature of the intestinal inflammatory response observed between these strains. While CCR9(+/+) and CCR9(+/-) mice were resistant to the infection and resolved the pathogen-induced inflammatory response, CCR9(-/-) mice developed a chronic inflammatory response, which was associated with over-expression of the cytokines IFN-γ, TNF-α, IL-4, IL-6 and IL-17, while IL-10 was not present. In addition, increased levels of CCL11, CCL20 and CCL28 chemokines were detected by qRT-PCR in CCR9(-/-) mice. E. histolytica trophozoites were identified in the lumen of the cecum of CCR9(-/-) mice at seven days post infection (pi), whereas in CCR9(+/+) mice trophozoites disappeared by day 1 pi. Interestingly, the inflammation observed in CCR9(-/-) mice, was associated with a delayed recruitment of CD4(+)CD25(+)FoxP3(+) T cells to the cecal epithelium and lamina propria, suggesting that this population may play a role in the early regulation of the inflammatory response against E. histolytica, likely through IL-10 production. In support of these data, CCR9(+) T cells were also identified in colon tissue sections obtained from patients with amoebic colitis. Our data suggest that a population of CCR9(+)CD4(+)CD25(+)FoxP3(+) T cells may participate in the control and resolution of the inflammatory immune response to E. histolytica infection.

FOXO1 increases CCL20 to promote NF-κB-dependent lymphocyte chemotaxis

Hepatic insulin resistance (IR) is associated with liver inflammatory diseases, but molecular mechanisms for the association remained elusive. IR is known to increase activity of forkhead box-containing protein O subfamily-1 (FOXO1), a transcription factor that was recently shown to enhance proinflammatory cytokine production in macrophages and adipocytes. Here we report that overexpression of constitutively active FOXO1 markedly increased chemokine ligand 20 (CCL20) expression and secretion in HepG2 hepatoma cells treated with TNF-α. The opposite was seen when endogenous FOXO1 was silenced. FOXO1 did not bind CCL20 promoter directly; instead, it potentiated CCL20 transcription through increasing the binding of p65/p50 heterodimer to a functional nuclear factor-κB site in the human CCL20 promoter. The conditional medium from TNF-α-treated HepG2 cells stimulated migration of human peripheral blood mononuclear cells. This stimulation was significantly enhanced when FOXO1 was overexpressed, and attenuated when FOXO1 was silenced. CCL20 antibody partly blocked the synergistic effect of FOXO1 and TNF-α on peripheral blood mononuclear cells migration. Additionally, TNF-α antagonizes the insulin/Akt signal transduction, thus leading to activation of FOXO1, which is capable of mediating a transcriptional activation role in response to TNF-α on CCL20 gene expression in HepG2 cells and promotes lymphocyte chemotaxis. Furthermore, we found that FOXO1 and CCL20 were coordinately up-regulated in the insulin resistant and inflammatory cell-infiltrated liver of db/db mice, an animal model that displayed hepatic and systemic low-grade inflammation. In conclusion, our data suggest that FOXO1 links IR to lymphocyte chemotaxis in the insulin-resistant hepatocytes and livers by amplifying nuclear factor-κB-dependent hepatic CCL20 production.

Integrin activation in the immune system

Modulation of leukocyte adhesiveness is critical to leukocyte function during the immune response. A central paradigm in this phenomenon is represented by integrin activation, which is controlled by inside-out signal transduction mechanisms triggered by selectins, chemoattractants and TcR-bound Ag and facilitated by mechanochemical forces. Integrins are heterodimeric adhesive receptors differently expressed on all leukocyte subtypes. At least two distinct modalities of integrin activation are known, namely conformational changes, leading to increased affinity, and lateral mobility leading to increased valency, both enhancing cell avidity (adhesiveness). Several signal transduction events have been correlated to integrin activation in leukocytes. The complexity of intracellular signaling networks leading to leukocyte integrin activation is likely functional to generate robustness and fine tuning of integrin activation allowing integration of qualitative and quantitative variations of extracellular signals leading to leukocyte-, agonist- and integrin-specific control of adhesion. In this context, the recent modular abstraction proposed for the functional architecture of biological networks may provide a powerful paradigm to understand regulation and specificity of signaling events. Accordingly, pro-adhesive intracellular signaling networks may be organized in regulatory signalosomes, or modules, corresponding to discrete clusters of interacting signaling proteins, with some devoted to context-dependent regulation of specificity and dynamics of integrin activation. The principles and technologies of systems biology, and more specifically of network theory, may help to address this complexity and unveil the inner logic governing leukocyte recruitment during the immune response.

T cell-mediated rejection of kidney transplants: a personal viewpoint

In kidney allografts, T cell mediated rejection (TCMR) is characterized by infiltration of the interstitium by T cells and macrophages, intense IFNG and TGFB effects, and epithelial deterioration. Recent experimental and clinical studies provide the basis for a provisional model for TCMR. The model proposes that the major unit of cognate recognition in TCMR is effector T cells engaging donor antigen on macrophages. This event creates the inflammatory compartment that recruits effector and effector memory CD4 and CD8 T cells, both cognate and noncognate, and macrophage precursors. Cognate T cells cross the donor microcirculation to enter the interstitium but spare the microcirculation. Local inflammation triggers dedifferentiation of the adjacent epithelium (e.g. loss of transporters and expression of embryonic genes) rather than cell death, via mechanisms that do not require known T-cell cytotoxic mechanisms or direct contact of T cells with the epithelium. Local epithelial changes trigger a response of the entire nephron and a second wave of dedifferentiation. The dedifferentiated epithelium is unable to exclude T cells, which enter to produce tubulitis lesions. Thus TCMR is a cognate recognition-based process that creates local inflammation and epithelial dedifferentiation, stereotyped nephron responses, and tubulitis, and if untreated causes irreversible nephron loss.

Progress of gut associated lymphocyte homing in inflammatory bowel disease

Inflammatory bowel disease (IBD) is characterized by chronic inflammation of intestinal tract, and it is classified into 2 subtypes traditionally, namely ulcerative colitis (UC) and Crohn's disease (CD). Many investigations have shown that intestinal lymphocyte homing (lymphocyte homing, LH) is closely related to IBD. This paper reviews the advances in the relationship between inflammatory bowel disease and lymphocyte homing.

Mechanisms of drug-induced allergy

We identified English-language publications on hypersensitivity reactions to xenobiotics through the PubMed database, using the search terms drug and/or xenobiotic, hypersensitivity reaction, mechanism, and immune mediated. We analyzed articles pertaining to the mechanism and the role of T cells. Immune hypersensitivity reactions to drugs are mediated predominantly by IgE antibodies or T cells. The mechanism of IgE-mediated reactions is well investigated, but the mechanisms of T-cell-mediated drug hypersensitivity are not well understood. The literature describes 2 concepts: the hapten/prohapten concept and the concept of pharmacological interactions of drugs with immune receptors. In T-cell-mediated allergic drug reactions, the specificity of the T-cell receptor that is stimulated by the drug may often be directed to a cross-reactive major histocompatibility complex-peptide compound. Thus, previous contact with the causative drug is not obligatory, and an immune mechanism should be considered as the cause of hypersensitivity, even in reactions that occur on primary exposure. Indeed, immune-mediated reactions to xenobiotics in patients without prior exposure to the agent have been described recently for radiocontrast media and neuromuscular blocking agents. Thus, the "allergenic" potential of a drug under development should be evaluated not only by screening its haptenlike characteristics but also by assessing its direct immunostimulatory potential.

Mechanisms of drug-induced allergy

We identified English-language publications on hypersensitivity reactions to xenobiotics through the PubMed database, using the search terms drug and/or xenobiotic, hypersensitivity reaction, mechanism, and immune mediated. We analyzed articles pertaining to the mechanism and the role of T cells. Immune hypersensitivity reactions to drugs are mediated predominantly by IgE antibodies or T cells. The mechanism of IgE-mediated reactions is well investigated, but the mechanisms of T-cell-mediated drug hypersensitivity are not well understood. The literature describes 2 concepts: the hapten/prohapten concept and the concept of pharmacological interactions of drugs with immune receptors. In T-cell-mediated allergic drug reactions, the specificity of the T-cell receptor that is stimulated by the drug may often be directed to a cross-reactive major histocompatibility complex-peptide compound. Thus, previous contact with the causative drug is not obligatory, and an immune mechanism should be considered as the cause of hypersensitivity, even in reactions that occur on primary exposure. Indeed, immune-mediated reactions to xenobiotics in patients without prior exposure to the agent have been described recently for radiocontrast media and neuromuscular blocking agents. Thus, the "allergenic" potential of a drug under development should be evaluated not only by screening its haptenlike characteristics but also by assessing its direct immunostimulatory potential.

Potent and broad-spectrum antimicrobial activity of CXCL14 suggests an immediate role in skin infections

The skin is constantly exposed to commensal microflora and pathogenic microbes. The stratum corneum of the outermost skin layer employs distinct tools such as harsh growth conditions and numerous antimicrobial peptides (AMPs) to discriminate between beneficial cutaneous microflora and harmful bacteria. How the skin deals with microbes that have gained access to the live part of the skin as a result of microinjuries is ill defined. In this study, we report that the chemokine CXCL14 is a broad-spectrum AMP with killing activity for cutaneous gram-positive bacteria and Candida albicans as well as the gram-negative enterobacterium Escherichia coli. Based on two separate bacteria-killing assays, CXCL14 compares favorably with other tested AMPs, including human beta-defensin and the chemokine CCL20. Increased salt concentrations and skin-typical pH conditions did not abrogate its AMP function. This novel AMP is highly abundant in the epidermis and dermis of healthy human skin but is down-modulated under conditions of inflammation and disease. We propose that CXCL14 fights bacteria at the earliest stage of infection, well before the establishment of inflammation, and thus fulfills a unique role in antimicrobial immunity.

The evolution of chemotaxis assays from static models to physiologically relevant platforms

The role of chemotactic gradients in the immunological response is an area which elicits a lot of attention due to its impact on the outcome of the inflammatory process. Consequently there are numerous standard in vitro designs which attempt to mimic chemotactic gradients, albeit in static conditions, and with no control over the concentration of the chemokine gradient. In recent times the design of the standard chemotaxis assay has incorporated modern microfluidic platforms, computer controlled flow devices and cell tracking software. Assays under fluid flow which use biochips have provided data which highlight the importance of shear stress on cell attachment and migration towards a chemokine gradient. However, the in vivo environment is far more complex in comparison to conventional cell assay chambers. The designs of biochips are therefore in constant flux as advances in technology permit ever greater imitations of in vivo conditions. Researchers are focused on designing a generation of new biochips and enhancing the physiological relevance of the current assays. The challenge is to combine a shear flow with a 3D scaffold containing the endothelial layer and permitting a natural diffusion of chemokines through a tissue-like basal matrix. Here we review the latest range of chemotaxis assays and assess the innovative features of their designs which enable them to better imitate the in vivo environment. We also present some alternative designs that were initially employed in tissue engineering which could potentially be used in the establishment of novel chemotaxis assays.

Early development of human hematopoietic and acquired immune systems in new born NOD/Scid/Jak3null mice intrahepatic engrafted with cord blood-derived CD34 + cells

An animal model in which the human immune system can be reconstituted is necessary to study acquired immunity in vivo. We report here a novel model, the NOD/SCID/JAK3(null) mouse, for the human immune system's development. Newborn mice transplanted with human cord blood CD34(+) cells intrahepatically, developed human T and B cells, and myeloid and plasmacytoid dendritic cells. The T and B cells had a naïve to memory phenotype, and included plasma cells. The human acquired immune system can be reconstituted from CD34(+) cells in NOD/SCID/JAK3(null) mice. This model is a powerful tool for the study of human immunity.

Constitutive expression of CXCL14 in healthy human and murine epithelial tissues

CXCL14 (BRAK) is an ill-described chemokine with unknown receptor selectivity. The human chemokine is constitutively expressed in epithelial tissues and is selective for dendritic cell precursors, indicating a possible function in the maintenance of epithelial DCs. Several studies have addressed the question of human CXCL14 expression in cancerous tissues; however, distribution in healthy tissues and, in particular, the cellular origin of this chemokine has not been thoroughly investigated. The expression pattern of murine CXCL14 is largely unknown. In agreement with the human chemokine, we demonstrated ubiquitous and constitutive expression of murine CXCL14 in various tissues, foremost in those of epithelial origin such as the skin and the gastrointestinal tract. In addition, we did not find any CXCL14 in lymphoid tissues. Interestingly and in contrast to humans, murine CXCL14 was strongly expressed in the lung. In the skin, CXCL14 was produced by keratinocytes and dermal macrophages in both mice and humans, whereas CXCL14-expressing mast cells could only be found in the human dermis. Therefore, despite the remarkable structural homology and the broad similarity in the tissue distribution of human and murine CXCL14, distinct differences point to diverse, species-specific needs for CXCL14 in epithelial immunity.

Migration of dendritic cell subsets and their precursors

The ability of dendritic cells (DCs) to initiate and orchestrate immune responses is a consequence of their localization within tissues and their specialized capacity for mobilization. The migration of a given DC subset is typified by a restricted capacity for recirculation, contrasting markedly with T cells. Routes of DC migration into lymph nodes differ notably for distinct DC subsets. Here, we compare the distinct migratory patterns of plasmacytoid DCs (pDCs), CD8alpha(+) DCs, Langerhans cells, and conventional myeloid DCs and discuss how the highly regulated patterns of DC migration in vivo may affect their roles in immunity. Finally, to gain a more molecular appreciation of the specialized migratory properties of DCs, we review the signaling cascades that govern the process of DC migration.

IL-21 induces in vivo immune activation of NK cells and CD8(+) T cells in patients with metastatic melanoma and renal cell carcinoma

PURPOSE

Human interleukin-21 (IL-21) is a class I cytokine previously reported in clinical studies on immune responsive cancers. Here we report the effects of systemic IL-21 therapy on the immune system in two phase 1 trials with this novel cytokine.

EXPERIMENTAL DESIGN

Recombinant IL-21 was administered by intravenous bolus injection at dose levels from 1 to 100 microg/kg using two planned treatment regimens: thrice weekly for 6 weeks (3/week); or once daily for five consecutive days followed by nine dose-free days (5 + 9). The following biomarkers were studied in peripheral blood mononuclear cells (PBMC) during treatment: phosphorylation of STAT3, alterations in the composition of leukocyte subsets, ex vivo cytotoxicity, expression of effector molecules in enriched CD8(+) T cells and CD56(+) NK cells by quantitative RT-PCR, and gene array profiling of CD8(+) T cells.

RESULTS

Effects of IL-21 were observed at all dose levels. In the 5 + 9 regimen IL-21 induced a dose dependent decrease in circulating NK cells and T cells followed by a return to baseline in resting periods. In both CD8(+) T cells and CD56(+) NK cells we found up-regulation of perforin and granzyme B mRNA. In addition, full transcriptome analysis of CD8(+) T cells displayed changes in several transcripts associated with increased cell cycle progression, cellular motility, and immune activation. Finally, cytotoxicity assays showed that IL-21 enhanced the ability of NK cells to kill sensitive targets ex vivo.

CONCLUSIONS

IL-21 was biologically active at all dose levels administered with evidence of in vivo NK cell and CD8(+) T cell activation.