Chemoattractants and their receptors in homeostasis and inflammation

MIP-4 is Induced by Bleomycin and Stimulates Cell Migration Partially via Nir-1 Receptor

Background

CC-chemokine ligand 18 also known as MIP-4 is a chemokine with roles in inflammation and immune responses. It has been shown that MIP-4 is involved in the development of several diseases including lung fibrosis and cancer. How exactly MIP-4 is regulated and exerts its role in lung fibrosis remains unclear. Therefore, in the present study, we examined how MIP-4 is regulated and whether it acts via its potential receptor Nir-1.

Materials and Methods

A549 cells were grown and maintained in DMEM : F12 (1 : 1) and supplemented with 10% FBS and 1000 U of penicillin/streptomycin and maintained as recommended by the manufacturer (ATCC). Cell migration and invasion, immunohistochemistry (IHC), Western blot, qPCR, and siRNA Nir-1 were used to determine MIP-4 regulation and its role in cell migration.

Results

Cell migration was increased following stimulation of cells with recombinant (r) MIP-4 and bleomycin (BLM), whereas quenching rMIP-4 with its antibody (Ab) or addition of the Ab to BLM or H2O2 diminished rMIP-4-induced cell migration. Along with cell migration, rMIP-4, BLM, and H2O2 induced the formation of actin filaments dynamic structures whereas costimulation with MIP-4 Ab limited BLM- and H2O2-induced effects. MIP-4 mRNA and protein were increased by BLM and H2O2, and the addition of its Ab significantly reduced treatments effect. Experiments with siRNA investigating whether Nir-1 is a potential MIR-4 receptor indicated that the inhibition of Nir-1 decreased cell migration/invasion but did not totally inhibit rMIP-4-induced cell migration.

Conclusion

Therefore, our data indicate that MIP-4 is regulated by BLM and H2O2 and costimulation with its Ab limits the effects on MIP-4 and that the Nir-1 receptor partially mediates MIP-4's effects on increased cell migration. These data also evidenced that MIP-4 is regulated by fibrotic and oxidative stimuli and that quenching MIP-4 with its Ab or therapeutically targeting the Nir-1 receptor may partially limit MIP-4 effects under fibrotic or oxidative stimulation.

Characterization and ex vivo expansion of rare in situ cytokine secreting T cell populations from tumor tissue and blood of oral squamous cell carcinoma patients

Rare subpopulations of tumor antigen-reactive memory T cells, which actively secrete type-1 effector cytokines, particularly TNF-α in situ, possess anti-tumor activity and prognostic relevance. These cells are relevant for cancer immunotherapy; however, their low frequencies make them difficult to study and novel protocols for their culture and expansion ex vivo are needed. Here, we studied the presence of T cells secreting type-1 cytokines (Cy⁺T cells) in the blood and tumors of 24 patients with oral squamous cell carcinomas (OSCC) and explored possibilities for their isolation and expansion. More than 90% of OSCC patients contained enriched numbers Cy⁺T cells in the blood and tumors compared to healthy donors in which these were hardly detectable. The majority of TNF-α⁺T cells were CD4⁺ T helper cells while IFN-γ⁺TIL were predominantly CD8⁺. Cy⁺T helper cells in the blood were early-differentiated memory T cells while Cy⁺TIL and Cy⁺CD8⁺T cells showed advanced-differentiated memory T cell phenotypes. We explored different conditions for their in vitro culture and found that Cy⁺T cells can be efficiently expanded in vitro to similar levels as Cy^-T cells and after expansion maintained their TNF-α secreting capacity. However, for optimal expansion they required specific culture conditions to support the maintenance of stem-like and central memory T cell phenotype. In conclusion, we show that Cy⁺T cells are enriched in OSCC patients and report a novel cell culture protocol optimized to specifically expand and functionally maintain these cells for further functional characterization or for their exploitation in immunotherapy of OSCC.

The Role of CD4+ Resident Memory T Cells in Local Immunity in the Mucosal Tissue - Protection Versus Pathology

Memory T cells are crucial for both local and systemic protection against pathogens over a long period of time. Three major subsets of memory T cells; effector memory T (T_EM) cells, central memory T (T_CM) cells, and tissue-resident memory T (T_RM) cells have been identified. The most recently identified subset, T_RM cells, is characterized by the expression of the C-type lectin CD69 and/or the integrin CD103. T_RM cells persist locally at sites of mucosal tissue, such as the lung, where they provide frontline defense against various pathogens. Importantly, however, T_RM cells are also involved in shaping the pathology of inflammatory diseases. A number of pioneering studies revealed important roles of CD8⁺ T_RM cells, particularly those in the local control of viral infection. However, the protective function and pathogenic role of CD4⁺ T_RM cells that reside within the mucosal tissue remain largely unknown. In this review, we discuss the ambivalent feature of CD4⁺ T_RM cells in the protective and pathological immune responses. We also review the transcriptional and epigenetic characteristics of CD4⁺ T_RM cells in the lung that have been elucidated by recent technical approaches. A better understanding of the function of CD4⁺ T_RM cells is crucial for the development of both effective vaccination against pathogens and new therapeutic strategies for intractable inflammatory diseases, such as inflammatory bowel diseases and chronic allergic diseases.

Sphingosine 1-Phosphate Receptor Modulators for Multiple Sclerosis

Fingolimod (Gilenya) received regulatory approval from the US FDA in 2010 as the first-in-class sphingosine 1-phosphate (S1P) receptor (S1PR) modulator and was the first oral disease-modifying therapy (DMT) used for the treatment of the relapsing forms of multiple sclerosis (MS). Development of this new class of therapeutic compounds has continued to be a pharmacological goal of high interest in clinical trials for treatment of various autoimmune disorders, including MS. S1P is a physiologic signaling molecule that acts as a ligand for a group of cell surface receptors. S1PRs are expressed on various body tissues and regulate diverse physiological and pathological cellular responses involved in innate and adaptive immune, cardiovascular, and neurological functions. Subtype 1 of the S1PR (S1PR₁) is expressed on the cell surface of lymphocytes, which are well known for their major role in MS pathogenesis and play an important regulatory role in the egress of lymphocytes from lymphoid organs to the lymphatic circulation. Thus, S1PR₁-directed pharmacological interventions aim to modulate its role in immune cell trafficking through sequestration of autoreactive lymphocytes in the lymphoid organs to reduce their recirculation and subsequent infiltration into the central nervous system. Indeed, receptor subtype selectivity for S1PR₁ is theoretically favored to minimize safety concerns related to interaction with other S1PR subtypes. Improved understanding of fingolimod's mechanism of action has provided strategies for the development of the more selective second-generation S1PR modulators. This selectivity serves to reduce the most important safety concern regarding cardiac-related side effects, such as bradycardia, which requires prolonged first-dose monitoring. It has led to the generation of smaller molecules with shorter half-lives, improved onset of action with no requirement for phosphorylation for activation, and preserved efficacy. The shorter half-lives of the second-generation agents allow for more rapid reversal of their pharmacological effects following treatment discontinuation. This may be beneficial in addressing further treatment-related complications in case of adverse events, managing serious or opportunistic infections such as progressive multifocal leukoencephalopathy, and eliminating the drug in pregnancies. In March 2019, a breakthrough in MS treatment was achieved with the FDA approval for the second S1PR modulator, siponimod (Mayzent), for both active secondary progressive MS and relapsing-remitting MS. This was the first oral DMT specifically approved for active forms of secondary progressive MS. Furthermore, ozanimod received FDA approval in March 2020 for treatment of relapsing forms of MS, followed by subsequent approvals from Health Canada and the European Commission. Other second-generation selective S1PR modulators that have been tested for MS, with statistically significant data from phase II and phase III clinical studies, include ponesimod (ACT-128800), ceralifimod (ONO-4641), and amiselimod (MT-1303). This review covers the available data about the mechanisms of action, pharmacodynamics and kinetics, efficacy, safety, and tolerability of the various S1PR modulators for patients with relapsing-remitting, secondary progressive, and, for fingolimod, primary progressive MS.

Autoantibodies against C5aR1, C3aR1, CXCR3, and CXCR4 are decreased in primary Sjogren's syndrome

BACKGROUND

Networks formed of numerous autoantibodies (aabs) directed against G-protein coupled receptors (GPCR) have been suggested to play important role in autoimmune disorders. In present study, we aimed to evaluate the association between anti-GPCR antibodies and primary Sjogren's syndrome (pSS) to determine the potential pathogenic factors.

METHODS

By applying a cell membrane-based ELISA technique, which is capable of detecting aabs against conformational epitopes within GPCR, serum levels of fourteen GPCR were determined in well-characterized patients with pSS (n = 52) and gender-matched healthy controls (n = 54). Comparisons between groups were analyzed by two-tailed Mann-Whitney U test, Bonferroni correction was applied for multiple comparisons. Spearman`s rank correlation coefficients were calculated between variables and visualized by heat map.

RESULTS

Compared to healthy subjects, sera of patients with pSS showed significantly higher binding to β2AR and ETAR, but lower binding to C5aR1, C3aR1, CXCR3, and CXCR4. Autoantibodies against C5aR1, C3aR1, CXCR3, and CXCR4 were also decreased in patients with rheumatoid arthritis. In pSS patients, levels of anti-CXCR3 and anti-CXCR4 antibodies were negatively correlated with circulating lymphocyte counts. Furthermore, correlation signatures of anti-GPCR antibodies changed dramatically in the patients with pulmonary involvement.

CONCLUSIONS

This study demonstrates an association between pSS and autoantibodies recognizing GPCR, especially those functionally involved in immune cell migration and exocrine glandular secretion.

Comprehensive flow cytometric reference intervals of leukocyte subsets from six study centers across Europe

A group of European FOCIS Centers of Excellence adapted panels of the Human Immunophenotyping Consortium (HIPC) for whole blood analysis. Using four core panels [T/regulatory T cell/B/natural killer (T/Treg /B/NK) and myeloid cells] the main leukocyte populations were analyzed in a clinical-diagnostic setting in a harmonized manner across different platforms. As a first step, the consortium presents here the absolute and relative frequencies of the leukocyte subpopulations in the peripheral blood of more than 300 healthy volunteers across six different European centers.

Intestinal inflammatory profile shows increase in a diversity of biomarkers in irritable bowel syndrome

Background: It has been proposed that irritable bowel syndrome (IBS) is a low-grade mucosal inflammatory disease.Objective: To characterize the intestinal inflammatory profile in IBS patients with or without fructose intolerance.Design: Patients referred to colonoscopy with IBS complaints were screened for participation. IBS patients diagnosed according to the Rome II criteria and with no organic gastrointestinal disease were included in the study. One subgroup was patients included in a fructose-reduced diet study for 2 months with effects based on VAS symptom scores. Healthy controls were subjects under investigation of colorectal cancer screening with no IBS or other gastrointestinal diseases. All patients included had normal histology from rectum. Mucosal cytokines, chemokines and growth factors were measured by multiplex technology.Results: Of 27 inflammatory markers tested in the mucosal tissue, 13 were significantly increased and none was significantly decreased in IBS as compared to controls. Significantly increased were the proinflammatory cytokines tumor necrosis factor, the typical TH1 markers IFNγ, IL-1β, IL-2 and RANTES, the typical TH2 markers IL-5 and IL-9, the TH17 marker IL-17, TNF, the pleiotropic IL-15, and the growth factors bFGF and GM-CSF. In IBS patients with fructose intolerance only IL-5 was significantly increased compared to patients without fructose intolerance.Conclusions: A dysregulated mucosal inflammatory profile with an increased level of TH1, TH2 and TH17 markers, and growth factors were observed in bowel mucosa in of IBS patients when compared to healthy controls.

The Synthetic Dipeptide Pidotimod Shows a Chemokine-Like Activity through CXC Chemokine Receptor 3 (CXCR3)

In recent years immunomodulators have gained a strong interest and represent nowadays an active expanding area of research for the control of microbial diseases and for their therapeutic potential in preventing, treating and reducing the morbidity and mortality of different diseases. Pidotimod (3-L-pyroglutamyl-L-thiaziolidine-4carboxylic acid, PDT) is a synthetic dipeptide, which possesses immunomodulatory properties and exerts a well-defined pharmacological activity against infections, but its real mechanism of action is still undefined. Here, we show that PDT is capable of activating tyrosine phosphorylation-based cell signaling in human primary monocytes and triggering rapid adhesion and chemotaxis. PDT-induced monocyte migration requires the activation of the PI3K/Akt signaling pathway and chemokine receptor CXCR3. Indeed, a mAb to CXCR3 and a specific receptor inhibitor suppressed significantly PDT-dependent chemotaxis, and CXCR3-silenced primary monocytes lost responsiveness to PDT chemoattraction. Moreover, our results highlighted that the PDT-induced migratory activity is sustained by the CXCR3A isoform, since CXCR3-transfected L1.2 cells acquired responsiveness to PDT stimulation. Finally, we show that PDT, as CXCR3 ligands, is also able to direct the migration of IL-2 activated T cells, which express the highest levels of CXCR3 among CXCR3-expressing cells. In conclusion, our study defines a chemokine-like activity for PDT through CXCR3A and points on the possible role that this synthetic dipeptide may play in leukocyte trafficking and function. Since recent studies have highlighted diverse therapeutic roles for molecules which activates CXCR3, our findings call for an exploration of using this dipeptide in different pathological processes.

The challenges of primary biliary cholangitis: What is new and what needs to be done

Primary Biliary Cholangitis (PBC) is an uncommon, chronic, cholangiopathy of autoimmune origin and unknown etiology characterized by positive anti-mitochondrial autoantibodies (AMA), female preponderance and progression to cirrhosis if left untreated. The diagnosis is based on AMA- or PBC-specific anti-nuclear antibody (ANA)-positivity in the presence of a cholestatic biochemical profile, histologic confirmation being mandatory only in seronegative cases. First-line treatment is ursodeoxycholic acid (UDCA), which is effective in preventing disease progression in about two thirds of the patients. The only approved second-line treatment is obeticholic acid. This article summarizes the most relevant conclusions of a meeting held in Lugano, Switzerland, from September 23rd-25th 2018, gathering basic and clinical scientists with various background from around the world to discuss the latest advances in PBC research. The meeting was dedicated to Ian Mackay, pioneer in the field of autoimmune liver diseases. The role of liver histology needs to be reconsidered: liver pathology consistent with PBC in AMA-positive individuals without biochemical cholestasis is increasingly reported, raising the question as to whether biochemical cholestasis is a reliable disease marker for both clinical practice and trials. The urgent need for new biomarkers, including more accurate markers of cholestasis, was also widely discussed during the meeting. Moreover, new insights in interactions of bile acids with biliary epithelia in PBC provide solid evidence of a role for impaired epithelial protection against potentially toxic hydrophobic bile acids, raising the fundamental question as to whether this bile acid-induced epithelial damage is the cause or the consequence of the autoimmune attack to the biliary epithelium. Strategies are needed to identify difficult-to-treat patients at an early disease stage, when new therapeutic approaches targeting immunologic pathways, in addition to bile acid-based therapies, may be effective. In conclusion, using interdisciplinary approaches, groundbreaking advances can be expected before long in respect to our understanding of the etiopathogenesis of PBC, with the ultimate aim of improving its treatment.

Relationships Between Phenotype and Function of Blood CD4+ T-Cells and Ascending Thoracic Aortic Aneurysm: an Experimental Study

Introduction

Non-familial ascending thoracic aorta dilation and aneurysms (TAAs) are silent diseases in elderly patients. Histopathology revealed that functionally polarized infiltrating CD4⁺ T-cells play a key role in aortic wall weakening.

Objective

To evaluate the possible associations between phenotype and cytokine production of circulating CD4⁺ T-lymphocytes and the presence of TAA in patients with aortic valve disease (AVD).

Methods

We studied blood samples from 10 patients with TAA and 10 patients with AVD. Flow cytometry was used to quantify: a) CD4⁺ T-lymphocytes surface expression of CD25, CD28, and chemokine receptors (CCR5, CXCR3, CX3CR1); b) fractions of in vitro stimulated CD4⁺ T-cells producing cytokines (interferon gamma [IFN-γ], interleukin [IL]-17A, IL-21, IL-10); c) CD4⁺CD25^highFoxP3⁺ regulatory T-cells (Treg) fraction. Enzyme-linked immunosorbent assays (ELISA) were performed for cytokines (IFN-γ, IL-6, IL-10, IL-17A, IL-23, transforming growth factor beta [TGF-β]) and chemokines (RANTES, CX3CL1).

Results

The total CD4⁺CD28^±CD4⁺/CX3CR1⁺ T-cells fraction was higher (P=0.0323) in AVD (20.452±4.673) than in TAA patients (8.633±2.030). The frequency ratio of CD4⁺ T-lymphocytes producing IFN-γ vs. IL-17A+IL-21 cytokine-producing CD4+ T-cells was higher (P=0.0239) in AVD (2.102±0.272) than in TAA (1.365±0.123) patients. The sum of CD4⁺CD28^±CD4⁺/CX3CR1⁺ T-cells correlated positively with values of the previous cytokine ratio (P=0.0002, R=0.732). The ratio of CD4⁺CD28^±CD4⁺/CX3CR1⁺ T-cells vs. Treg was higher (P=0.0008) in AVD (20.859±3.393) than in TAA (6.367±1.277) patients.

Conclusion

Our results show that the presence of TAA in subjects with AVD is associated with imbalance between phenotypic and cytokine-producing subsets of circulating CD4+ T-lymphocytes, prevalently oriented towards a pro-fibrotic and IFN-γ counteracting effect to functional polarization.

Participation of the spleen in the IgA immune response in the gut

The role of the spleen in the induction of an immune response to orally administered antigens is still under discussion. Although it is well known that after oral antigen administration specific germinal centres are not only formed in the Peyers patches (PP) and the mesenteric lymph nodes (mLN) but also in the spleen, there is still a lack of functional data showing a direct involvement of splenic B cells in an IgA immune response in the gut. In addition, after removal of mLN a high level of IgA+ B cells was observed in the gut. Therefore, in this study we analysed the role of the spleen in the induction of IgA+ B cells in the gut after mice were orally challenged with antigens. Here we have shown that antigen specific splenic IgM+ B cells after in vitro antigen stimulation as well as oral immunisation of donor mice were able to migrate into the gut of recipient mice, where they predominantly switch to IgA+ plasma cells. Furthermore, stimulation of recipient mice by orally administered antigens enhanced the migration of the splenic B cells into the gut as well as their switch to IgA+ plasma cells. Removal of the mLN led to a higher activation level of the splenic B cells. Altogether, our results imply that splenic IgM+ B cells migrate in the intestinal lamina propria, where they differentiate into IgA+ plasma cells and subsequently proliferate. In conclusion, we demonstrated that the spleen plays a major role in the gut immune response serving as a reservoir of immune cells that migrate to the site of antigen entrance.

CCL18 promotes epithelial-mesenchymal transition, invasion and migration of pancreatic cancer cells in pancreatic ductal adenocarcinoma

CCL18 is a chemokine that is primarily expressed in monocytes, macrophages and immature dendritic cells and plays a crucial role in immune and inflammation responses. Recently, CCL18 was found to play pivotal roles in the development of several kinds of cancers, but its expression status and role during the tumorigenesis of pancreatic cancer remain unknown. In this study, we performed immunohistochemistry and enzyme-linked immunosorbent assay (ELISA) to evaluate the expression of CCL18 in human pancreatic ductal adenocarcinoma (PDAC) tissues and preoperative serum, respectively. The results showed that both cancer epithelial cells and mesenchymal macrophages in PDAC tissues positively expressed CCL18. Serum CCL18 levels were significantly higher in patients with PDAC in comparison to healthy controls. The expression of CCL18 in both cancer epithelial cells and mesenchymal cells was correlated with lymph node metastasis, histopathological grading and overall survival in 62 PDAC patients. In vitro assays showed that the gene and protein expression of CCL18 from U937 and THP-1 cell- derived macrophages were significantly higher than that from unstimulated U937 cells and THP-1 cells. In contrast, pancreatic cancer cell lines showed little to no CCL18 expression even after IL4 stimulation. Intriguingly, pancreatic cancer cell lines expressed the potential CCL18 receptors PITPNM3, CCR6 and GPR3. Furthermore, treatment with recombinant human CCL18 promoted the migration and invasion of pancreatic cancer cells, but had no effect on cell proliferation. Consistent with these results, CCL18 induced the expression of the epithelial-mesenchymal transition (EMT) related gene SNAIL1. Our findings suggest that the serum level of CCL18 is a potential biomarker for the diagnosis and prognosis of PDAC, and that the combined functions of CCL18 in mesenchymal and cancer cells might accelerate the progression of PDAC by promoting the epithelial-mesenchymal transition, invasion and migration of pancreatic cancer cells.

Molecular pharmacodynamics of new oral drugs used in the treatment of multiple sclerosis

New oral drugs have considerably enriched the therapeutic armamentarium for the treatment of multiple sclerosis. This review focuses on the molecular pharmacodynamics of fingolimod, dimethyl fumarate (BG-12), laquinimod, and teriflunomide. We specifically comment on the action of these drugs at three levels: 1) the regulation of the immune system; 2) the permeability of the blood-brain barrier; and 3) the central nervous system. Fingolimod phosphate (the active metabolite of fingolimod) has a unique mechanism of action and represents the first ligand of G-protein-coupled receptors (sphingosine-1-phosphate receptors) active in the treatment of multiple sclerosis. Dimethyl fumarate activates the nuclear factor (erythroid-derived 2)-related factor 2 pathway of cell defense as a result of an initial depletion of reduced glutathione. We discuss how this mechanism lies on the border between cell protection and toxicity. Laquinimod has multiple (but less defined) mechanisms of action, which make the drug slightly more effective on disability progression than on annualized relapse rate in clinical studies. Teriflunomide acts as a specific inhibitor of the de novo pyrimidine biosynthesis. We also discuss new unexpected mechanisms of these drugs, such as the induction of brain-derived neurotrophic factor by fingolimod and the possibility that laquinimod and teriflunomide regulate the kynurenine pathway of tryptophan metabolism.

CCR7 provides localized access to IL-2 and defines homeostatically distinct regulatory T cell subsets

CD44^loCD62L^hi regulatory T cells preferentially access IL-2 in T cell zones due to expression of CCR7

Immune tolerance and activation depend on precise control over the number and function of immunosuppressive Foxp3⁺ regulatory T (T reg) cells, and the importance of IL-2 in maintaining tolerance and preventing autoimmunity is clear. However, the homeostatic requirement for IL-2 among specific populations of peripheral T reg cells remains poorly understood. We show that IL-2 selectively maintains a population of quiescent CD44^loCD62L^hi T reg cells that gain access to paracrine IL-2 produced in the T cell zones of secondary lymphoid tissues due to their expression of the chemokine receptor CCR7. In contrast, CD44^hiCD62L^loCCR7^lo T reg cells that populate nonlymphoid tissues do not access IL-2–prevalent regions in vivo and are insensitive to IL-2 blockade; instead, their maintenance depends on continued signaling through the co-stimulatory receptor ICOS (inducible co-stimulator). Thus, we define a fundamental homeostatic subdivision in T reg cell populations based on their localization and provide an integrated framework for understanding how T reg cell abundance and function are controlled by unique signals in different tissue environments.

Monitoring immune modulation by nutrition in the general population: identifying and substantiating effects on human health

Optimal functioning of the immune system is crucial to human health, and nutrition is one of the major exogenous factors modulating different aspects of immune function. Currently, no single marker is available to predict the effect of a dietary intervention on different aspects of immune function. To provide further guidance on the assessment and interpretation of the modulation of immune functions due to nutrition in the general population, International Life Sciences Institute Europe commissioned a group of experts from academia, government and the food industry to prepare a guidance document. A draft of this paper was refined at a workshop involving additional experts. First, the expert group defined criteria to evaluate the usefulness of immune function markers. Over seventy-five markers were scored within the context of three distinct immune system functions: defence against pathogens; avoidance or mitigation of allergy; control of low-grade (metabolic) inflammation. The most useful markers were subsequently classified depending on whether they by themselves signify clinical relevance and/or involvement of immune function. Next, five theoretical scenarios were drafted describing potential changes in the values of markers compared with a relevant reference range. Finally, all elements were combined, providing a framework to aid the design and interpretation of studies assessing the effects of nutrition on immune function. This stepwise approach offers a clear rationale for selecting markers for future trials and provides a framework for the interpretation of outcomes. A similar stepwise approach may also be useful to rationalise the selection and interpretation of markers for other physiological processes critical to the maintenance of health and well-being.

CD8(+) granzyme B(+)-mediated tissue injury vs. CD4(+)IFNγ(+)-mediated parasite killing in human cutaneous leishmaniasis

A protective or deleterious role of CD8⁺T cells in human cutaneous leishmaniasis (CL) has been debated. The present report explores the participation of CD8⁺T cells in disease pathogenesis as well as in parasite killing. CD8⁺T cells accumulated in CL lesions as suggested by a higher frequency of CD8⁺CD45RO⁺T cells and CD8⁺CLA⁺T cells compared with peripheral blood mononuclear cells. Upon Leishmania braziliensis restimulation, most of the CD8⁺T cells from the lesion expressed cytolytic markers, CD107a and granzyme B. Granzyme B expression in CL lesions positively correlated with lesion size and percentage of TUNEL-positive cells. We also observed a significantly higher percentage of TUNEL-positive cells and granzyme B expression in the biopsies of patients showing a more intense necrotic process. Furthermore, coculture of infected macrophages and CD8⁺T lymphocytes resulted in the release of granzyme B, and the use of granzyme B inhibitor, as well as z-VAD, Fas:Fc, or anti-IFN-γ, had no effect upon parasite killing. However, coculture of infected macrophages with CD4⁺T cells strongly increased parasite killing, which was completely reversed by anti-IFN-γ. Our results reveal a dichotomy in human CL: CD8⁺ granzyme B⁺T cells mediate tissue injury, whereas CD4⁺IFN-γ⁺T cells mediate parasite killing.

Inflammatory chemokines direct and restrict leukocyte migration within live tissues as glycan-bound gradients

Chemokines are essential in many cell migration processes, including the recruitment of leukocytes to sites of infection. In the latter context, chemokines promote leukocyte extravasation into the relevant tissue through a well-studied cascade of events. It is widely believed that chemokines further guide leukocytes within tissues via chemotaxis, the directed migration along gradients of soluble ligands. However, the basic mechanism of chemokine action within tissues has yet to be formally addressed in vivo. We identified a chemokine (zCxcl8) that recruits zebrafish neutrophils to infection loci and analyzed its function directly within interstitial tissues of living larvae. Using noninvasive imaging and a controlled cellular source of zCxcl8, we found that zCxcl8 guides neutrophils in a 2-fold manner: by biasing cell speed according to direction (orthotaxis) and by restricting cell motility near the source. We further show that zCxcl8 establishes tissue-bound gradients in vivo by binding to heparan sulfate proteoglycans (HSPGs). Inhibition of this interaction compromised both directional guidance and restriction of neutrophil motility. Thus, by interacting with extracellular HSPGs, chemokines establish robust surface-bound (haptotactic) gradients that mediate both recruitment and retention of leukocytes at sites of infection.

CCX-CKR deficiency alters thymic stroma impairing thymocyte development and promoting autoimmunity

The atypical chemokine receptor CCX-CKR regulates bioavailability of CCL19, CCL21, and CCL25, homeostatic chemokines that play crucial roles in thymic lymphopoiesis. Deletion of CCX-CKR results in accelerated experimental autoimmunity induced by immunization. Here we show that CCX-CKR deletion also increases incidence of a spontaneous Sjögren's syndrome-like pathology, characterized by lymphocytic infiltrates in salivary glands and liver of CCX-CKR(-/-) mice, suggestive of a defect in self-tolerance when CCX-CKR is deleted. This prompted detailed examination of the thymus in CCX-CKR(-/-) mice. Negatively selected mature SP cells were less abundant in CCX-CKR(-/-) thymi, yet expansion of both DP and immature SP cells was apparent. Deletion of CCX-CKR also profoundly reduced proportions of DN3 thymocyte precursors and caused DN2 cells to accumulate within the medulla. These effects are likely driven by alterations in thymic stroma as CCX-CKR(-/-) mice have fewer cTECs per thymocyte, and cTECs express the highest level of CCX-CKR in the thymus. A profound decrease in CCL25 within the thymic cortex was observed in CCX-CKR(-/-) thymi, likely accounting for their defects in thymocyte distribution and frequency. These findings identify a novel role for CCX-CKR in regulating cTEC biology, which promotes optimal thymocyte development and selection important for self-tolerant adaptive immunity.

T cell homing to epithelial barriers in allergic disease

Allergic inflammation develops in tissues that have large epithelial surface areas that are exposed to the environment, such as the lung, skin and gut. In the steady state, antigen-experienced memory T cells patrol these peripheral tissues to facilitate swift immune responses against invading pathogens. In at least two allergy-prone organs, the skin and the gut, memory T cells are programmed during the initial antigen priming to express trafficking receptors that enable them to preferentially home to these organs. In this review we propose that tissue-specific memory and inflammation-specific T cell trafficking facilitates the development of allergic disease in these organs. We thus review recent advances in our understanding of tissue-specific T cell trafficking and how regulation of T cell trafficking by the chemokine system contributes to allergic inflammation in mouse models and in human allergic diseases of the skin, lung and gut. Inflammation- and tissue-specific T lymphocyte trafficking pathways are currently being targeted as new treatments for non-allergic inflammatory diseases and may yield effective new therapeutics for allergic diseases.

The colocalization potential of HIV-specific CD8+ and CD4+ T-cells is mediated by integrin β7 but not CCR6 and regulated by retinoic acid

CD4⁺ T-cells from gut-associated lymphoid tissues (GALT) are major targets for HIV-1 infection. Recruitment of excess effector CD8⁺ T-cells in the proximity of target cells is critical for the control of viral replication. Here, we investigated the colocalization potential of HIV-specific CD8⁺ and CD4⁺ T-cells into the GALT and explored the role of retinoic acid (RA) in regulating this process in a cohort of HIV-infected subjects with slow disease progression. The expression of the gut-homing molecules integrin β7, CCR6, and CXCR3 was identified as a “signature” for HIV-specific but not CMV-specific CD4⁺ T-cells thus providing a new explanation for their enhanced permissiveness to infection in vivo. HIV-specific CD8⁺ T-cells also expressed high levels of integrin β7 and CXCR3; however CCR6 was detected at superior levels on HIV-specific CD4⁺versus CD8⁺ T-cells. All trans RA (ATRA) upregulated the expression of integrin β7 but not CCR6 on HIV-specific T-cells. Together, these results suggest that HIV-specific CD8⁺ T-cells may colocalize in excess with CD4⁺ T-cells into the GALT via integrin β7 and CXCR3, but not via CCR6. Considering our previous findings that CCR6⁺CD4⁺ T-cells are major cellular targets for HIV-DNA integration in vivo, a limited ability of CD8⁺ T-cells to migrate in the vicinity of CCR6⁺CD4⁺ T-cells may facilitate HIV replication and dissemination at mucosal sites.

Myocardial migration by fibroblast progenitor cells is blood pressure dependent in a model of angII myocardial fibrosis

Activation of the renin-angiotensin system (RAS) is thought to promote myocardial fibrosis. However, it is unclear whether this physiological fibrotic response results from chronic hemodynamic stress or from direct cellular signaling. Male C57B/6 mice were randomly assigned to receive angiotensin II (AngII) (2.0 μg kg(-1) min(-1)), AngII+hydralazine (6.9 μg kg(-1) min(-1)) or saline (control) via osmotic pumps for 7 days. Blood pressure was measured via noninvasive plethysmography. Hearts were harvested and processed for analysis. Cellular infiltration and collagen deposition were analyzed using histological staining. Molecular mediators were assessed using quantitative RT-PCR. As previously described, animals that received AngII developed hypertension and multifocal cellular infiltration by SMA(+)/CD133(+) fibroblast progenitors followed by collagen deposition. The coadministration of hydralazine with AngII completely inhibited the hypertensive effects of AngII (P0.01) and resulted in minimal cellular infiltration and minimal collagen deposition. These findings were in the context of persistent RAS activation, which was evidenced by elevation in serum aldosterone levels in animals that received AngII or AngII+hydralazine compared with animals that received saline. At the molecular level, infusion of AngII resulted in the significant upregulation of profibrotic factors (connective tissue growth factor-7.8±0.7 fold), proinflammatory mediators (TNFα-4.6±0.8 fold; IL-1β-6.4±2.6 fold) and chemokines (CCL2-3.8±1.0 fold; CXCL12-3.2±0.4 fold), which were inhibited when hydralazine was also infused. We provide evidence that myocardial infiltration by fibroblast progenitor cells secondary to AngII and the resultant fibrosis can be prevented by the addition of hydralazine. Furthermore, the beneficial effects of hydralazine were observed while maintaining RAS activation, suggesting that the mechanism of fibrosis is blood pressure dependent.

LPS-induced migration of peritoneal B-1 cells is associated with upregulation of CXCR4 and increased migratory sensitivity to CXCL12

B-1 cells, which constitute a predominant lymphocyte subset in serosal cavities and produce most of natural antibodies, are subdivided into the CD5(+) B-1a and CD5(-) B-1b cell subpopulations, but the differential roles of B-1a and B-1b cells are not well understood. We report that B-1a cells preferentially migrate out of the peritoneal cavity and upregulate the expression of CXCR4 with heightened sensitivity to CXCL12 and CXCL13 upon LPS treatment compared to B-1b and B-2 cells. Whereas B-1a cells were slightly more abundant than B-1b and B-2 cells in the homeostatic condition, the number of B-1a cells preferentially decreased 48 hr after LPS treatment. The decrease in the peritoneal B-1a cell number was accompanied with increased migration of B-1a cells toward CXCL-12 and CXCL-13 in in vitro transmigration assay using peritoneal B cells from LPS treated mice. The expression level of CXCR4, but not of CXCR5, was also more prominently increased in B-1a cells upon LPS stimulation. LPS-stimulated B-1a cells did not accumulate in omental milky spots in contrast to B-2 cells. These results suggest that B-1a cells actively migrate out of the peritoneal cavity through the regulation of the migratory responsiveness to chemokines and actively participate in systemic immune responses.

Immune functions of the skin

The skin, the body's largest organ, helps to secure the integrity of the host and, at the same time, allows the individual to communicate with the outside world. This finely tuned balance between protection from harmful pathogens (mostly microorganisms) and bidirectional signal exchange is provided by a network of structural, cellular, and molecular elements that are collectively referred to as the skin barrier. This "gateway" has a physical, chemical, and immunologic component. The role of the latter is to elicit a powerful defense reaction in the case of danger and, at the same time, to prevent such a reaction against innocuous substances. Immune responses originating in the skin are mounted and executed by cells and molecules of the innate or the adaptive immune system. Innate reactions are typically rapid, poorly discriminating, and do not exhibit memory. Adaptive responses, in contrast, show a high degree of specificity as well as memory but need a protracted time for their development. As a consequence, innate and adaptive responses are consecutive events influencing each other. In fact, we now know that the type and magnitude of the innate reactions govern and often determine the quality and quantity of adaptive responses.

Inflammatory cytokines IL-6 and TNF-α regulate lymphocyte trafficking through the local lymph node

Lymphocyte trafficking from blood to lymph and back is a tightly regulated process. Given appropriate stimuli, trafficking of cells through the lymph node changes from a 'steady-state' to a bimodal flow. Initially, a 'shutdown' phase occurs, leading to a dramatic reduction in efferent cell output. This is followed by a 'recruitment' phase whereby the efferent cell output becomes greatly elevated before returning to baseline levels. The shutdown/recruitment process is hypothesised to promote encounters between Ag-specific lymphocytes and APCs in an environment conducive to immune response induction. Cytokines, such as TNF-α have been shown to play an important role in regulating lymphocyte trafficking. Here, we unravel the role of cytokines in the regulation of cell trafficking using an in vivo sheep lymphatic cannulation model whereby the prefemoral lymph nodes were cannulated and recombinant cytokines were injected subcutaneously into the draining area of the cannulated node. We demonstrate that local injection of purified IL-6 or TNF-α stimulates shutdown/recruitment in the draining lymph node. While the effect of IL-6 appears to be direct, TNF-α may mediate shutdown/recruitment through IL-6.

Platelet function in rheumatoid arthritis: arthritic and cardiovascular implications

Patients with rheumatoid arthritis (RA) are at high risk of cardiovascular events. Platelet biomarkers are involved in inflammation, atherosclerosis and thrombosis. Cardiovascular and RA-associated factors can alter the structure and function of platelets, starting from megakaryocytopoiesis. Reactive megakaryocytopoiesis increases circulating platelets count and triggers hyperactivity. Hyperactive platelets target synovial membranes with subsequent local rheumatoid inflammation. Hyperactive platelets interact with other cells, and target the vascular wall. Accumulating evidence suggests that disease modifying anti-rheumatic drugs (DMARD) decrease platelet activity.

Platelet function in rheumatoid arthritis: arthritic and cardiovascular implications

Patients with rheumatoid arthritis (RA) are at high risk of cardiovascular events. Platelet biomarkers are involved in inflammation, atherosclerosis and thrombosis. Cardiovascular and RA-associated factors can alter the structure and function of platelets, starting from megakaryocytopoiesis. Reactive megakaryocytopoiesis increases circulating platelets count and triggers hyperactivity. Hyperactive platelets target synovial membranes with subsequent local rheumatoid inflammation. Hyperactive platelets interact with other cells, and target the vascular wall. Accumulating evidence suggests that disease modifying anti-rheumatic drugs (DMARD) decrease platelet activity.

A rapid chemokine response of macrophage inflammatory protein (MIP)-1α, MIP-1β and the regulated on activation, normal T expressed and secreted chemokine is associated with a sustained virological response in the treatment of chronic hepatitis C

The role of chemokines in chronic hepatitis C virus (HCV) infection is not fully understood. The present study aimed to characterize the baseline serum concentrations and the initial β-chemokine response to treatment with interferon-α and ribavirin with respect to the final clinical outcome of virological response to treatment. Serum concentrations of alanine aminotransferase (ALT) and of the CC subfamily chemokines [macrophage inflammatory protein (MIP)-1α, MIP-1β, monocyte chemoattractant protein (MCP)-1 and the regulated on activation, normal T expressed and secreted (RANTES) chemokine] were measured in patients with chronic HCV infection and in healthy individuals. Necroinflammation and fibrosis were scored in liver biopsies. Treatment outcomes were classified as with or without a sustained virological response after a full-course treatment according to the genotypes. The main treatment group consisted of 72 patients with chronic hepatitis C, whereas 24-h blood samples were available for 42 patients. Increased baseline levels of all CC chemokines were found in the two responder groups compared to the healthy controls, although significant levels were reached only for MIP-1α and MCP-1. No correlation was observed between chemokine levels and serum ALT levels, any histological necroinflammatory parameters, or the fibrosis grade. After 24 h of treatment, increases in MIP-1α, MIP-1β and RANTES levels were exclusively observed in the group with sustained virological response. MCP-1 was also significantly increased after 24 h in both responder groups, although no differences were observed between the two responder groups. In conclusion, an early MIP-1α, MIP-1β, and RANTES response may predict a sustained response to virological treatment.

CXCR5 expressing human central memory CD4 T cells and their relevance for humoral immune responses

High expression of CXCR5 is one of the defining hallmarks of T follicular helper cells (T(FH)), a CD4 Th cell subset that promotes germinal center reactions and the selection and affinity maturation of B cells. CXCR5 is also expressed on 20-25% of peripheral blood human central memory CD4 T cells (T(CM)), although the definitive function of these cells is not fully understood. The constitutive expression of CXCR5 on T(FH) cells and a fraction of circulating T(CM) suggests that CXCR5(+) T(CM) may represent a specialized subset of memory-type T(FH) cells programmed for homing to follicles and providing B cell help. To verify this assumption, we analyzed this cell population and show its specialized function in supporting humoral immune responses. Compared with their CXCR5(-) T(CM) counterparts, CXCR5(+) T(CM) expressed high levels of the chemokine CXCL13 and efficiently induced plasma cell differentiation and Ig secretion. We found that the distinct B cell helper qualities of CXCR5(+) T(CM) were mainly due to high ICOS expression and pronounced responsiveness to ICOS ligand costimulation together with large IL-10 secretion. Furthermore, B cell helper attributes of CXCR5(+) T(CM) were almost exclusively acquired on cognate interaction with B cells, but not with dendritic cells. This implies that a preferential recruitment of circulating CXCR5(+) T(CM) to CXCL13-rich B cell follicles is required for the promotion of a quick and efficient protective secondary humoral immune response. Taken together, we propose that CXCR5(+) T(CM) represent a distinct memory cell subset specialized in supporting Ab-mediated immune responses.

Finding their niche: chemokines directing cell migration in the thymus

T lymphocytes are generated throughout life, arising from bone marrow-derived progenitors that complete an essential developmental process in the thymus. Thymic T cell education leads to the generation of a self-restricted and largely self-tolerant peripheral T-cell pool and is facilitated by interactions with thymic stromal cells residing in distinct supportive niches. The signals governing thymocyte precursor migration into the thymus, directing thymocyte navigation through thymic microenvironments and mature T-cell egress into circulation were, until recently, largely unknown, but presumed to be mediated to a large extent by chemokine signalling. Recent studies have now uncovered various specific functions for members of the chemokine superfamily in the thymus. These studies have not only revealed distinct but also in some cases overlapping roles for several chemokine family members in various thymocyte migration events and have also shown that homing and positioning of other cells in the thymus, such as dendritic cells and natural killer T cells is also chemokine-dependent. Here, we discuss current understanding of the role of chemokines in the thymus and highlight key future avenues for investigation in this field.

Th17 lineage commitment and HIV-1 pathogenesis

PURPOSE OF REVIEW

The present review emphasizes the requirement for functional genomic studies and studies in human immunology toward the identification of tissue-specific regulators of human Th17 lineage commitment and molecular determinants for HIV permissiveness in Th17 cells.

RECENT FINDINGS

Th17 cells play a beneficial role in immunity against bacteria and fungi and a deleterious role in autoimmune diseases. Commensal microbiota control Th17 differentiation in the gut. Th17 cells are depleted from the gut of HIV-infected individuals and their depletion is associated with microbial translocation, which is a cause for chronic immune activation and disease progression. Th17 cells are permissive to HIV infection and therefore play a dual role in HIV pathogenesis.

SUMMARY

The discovery of human Th17 lineage revised our thinking about CD4 T-cell heterogeneity and plasticity in the context of HIV pathogenesis. The present review highlights unsolved mysteries around the genetic control of differentiation and tissue-specific specialization of human Th17 cells. Systems biology studies are now required to provide a global view of transcriptional changes in Th17 subsets and mucosal tissues and to shed light on molecular mechanisms of Th17 depletion in HIV infection, with the final goal to identify new strategies to improve mucosal immunity in infected individuals.

Chemerin contributes to inflammation by promoting macrophage adhesion to VCAM-1 and fibronectin through clustering of VLA-4 and VLA-5

Chemerin is a potent macrophage chemoattractant protein. We used murine peritoneal exudate cells (PECs) in adhesion, flow cytometry, and confocal microscopy assays to test the hypothesis that chemerin can also contribute to inflammation by promoting macrophage adhesion. Chemerin stimulated the adhesion of PECs to the extracellular matrix protein fibronectin and to the adhesion molecule VCAM-1 within a minute, with an EC(50) of 322 and 196 pM, respectively. Experiments using pertussis toxin and PECs from ChemR23(-/-) mice demonstrated that chemerin stimulated the adhesion of macrophages via the Gi protein-coupled receptor ChemR23. Blocking Abs against integrin subunits revealed that 89% of chemerin-stimulated adhesion to fibronectin was dependent on increased avidity of the integrin VLA-5 (alpha(5)beta(1)) and that 88% of adhesion to VCAM-1 was dependent on increased avidity of VLA-4 (alpha(4)beta(1)). Although chemerin was unable to induce an increase in integrin affinity as judged by the binding of soluble ligand, experiments using confocal microscopy revealed an increase in valency resulting from integrin clustering as the mechanism responsible for chemerin-stimulated macrophage adhesion. PI3K, Akt, and p38 were identified as key signaling mediators in chemerin-stimulated adhesion. The finding that chemerin can rapidly stimulate macrophage adhesion to extracellular matrix proteins and adhesion molecules, taken together with its ability to promote chemotaxis, suggests a novel role for chemerin in the recruitment and retention of macrophages at sites of inflammation.

Alternatively activated alveolar macrophages in pulmonary fibrosis-mediator production and intracellular signal transduction

Activated macrophages have been characterized as M1 and M2 according to their inflammatory response pattern. Here we analyzed the M2 marker expression and intracellular signal transduction in the course of cytokine-driven differentiation. We found elevated spontaneous production of the chemokines CCL17, CCL18 and CCL22 and increased expression of CD206 by alveolar macrophages from patients with lung fibrosis. Stimulation of normal human AM with Th2 cytokines IL-4 and/or IL-10 in vitro revealed IL-4 as the most powerful inducer of M2-phenotype in AM and monocytes. Importantly, IL-10 enhanced IL-4-induced expression of CCL18 and IL-1RA in a synergistic fashion. IL-4/IL-10 stimulation induces a strong activation of STAT3 in AM from fibrosis patients. These results suggest an important role for M2 polarized AM in the pathogenesis of pulmonary fibrosis and indicate that both IL-4 and IL-10 account for human AM phenotype shift to M2, as seen in patients with fibrotic interstitial lung diseases.

Polarized dendritic cells as cancer vaccines: directing effector-type T cells to tumors

Ex vivo generation and antigen loading of dendritic cells (DCs) from cancer patients helps to bypass the dysfunction of endogenous DCs. It also allows to control the process of DC maturation and to imprint in maturing DCs several functions essential for induction of effective forms of cancer immunity. Recent reports from several groups including ours demonstrate that distinct conditions of DC generation and maturation can prime DCs for preferential interaction with different (effector versus regulatory) subsets of immune cells. Moreover, differentially-generated DCs have been shown to imprint different effector mechanisms in CD4(+) and CD8(+) T cells (delivery of "signal three") and to induce their different homing properties (delivery of "signal four"). These developments allow for selective induction of tumor-specific T cells with desirable effector functions and tumor-relevant homing properties and to direct the desirable types of immune cells to tumors.

Resistance to dengue virus infection in mice is potentiated by CXCL10 and is independent of CXCL10-mediated leukocyte recruitment

CXCL10 is an IFN-inducible chemokine ligand that binds CXCR3, a receptor that is expressed on lymphocytes; CXCL10 shares the CXCR3 receptor with another two ligands, CXCL9 and CXCL11. Previously, we found that CXCL10(-/-) mice were more susceptible than wild-type (WT) mice to dengue virus (DENV) infection. In this study, we explored the mechanisms underlying this enhanced susceptibility. We found that viral loads were higher in the brains of CXCL10(-/-) mice than in WT mice. Presuming a defect in effector lymphocyte migration, we investigated whether recruitment of effector T cells and Ab-secreting cells to the infected tissues were impaired in CXCL10(-/-) mice. Unexpectedly, compared with WT, CXCL10(-/-) mice had comparable numbers of total infiltrating T cells, higher numbers of CXCR3(+) T cells, and higher numbers of Ab-secreting cells in the brain. Additionally, we found that CXCL10 was induced in neurons following DENV infection and that CXCL10 competed with DENV for binding to cell surface heparan sulfate, a coreceptor for DENV entry, thus inhibiting binding of DENV to neuronal cells. These results demonstrate that the enhanced susceptibility of CXCL10(-/-) mice to DENV infection is not due to a defect in recruitment of effector lymphocytes but rather to an antiviral activity that promotes viral clearance.

Peripheral blood CCR4+CCR6+ and CXCR3+CCR6+CD4+ T cells are highly permissive to HIV-1 infection

There is limited knowledge on the identity of primary CD4(+) T cell subsets selectively targeted by HIV-1 in vivo. In this study, we established a link between HIV permissiveness, phenotype/homing potential, and lineage commitment in primary CD4(+) T cells. CCR4(+)CCR6(+), CCR4(+)CCR6(-), CXCR3(+)CCR6(+), and CXCR3(+)CCR6(-) T cells expressed cytokines and transcription factors specific for Th17, Th2, Th1Th17, and Th1 lineages, respectively. CCR4(+)CCR6(+) and CXCR3(+)CCR6(+) T cells expressed the HIV coreceptors CCR5 and CXCR4 and were permissive to R5 and X4 HIV replication. CCR4(+)CCR6(-) T cells expressed CXCR4 but not CCR5 and were permissive to X4 HIV only. CXCR3(+)CCR6(-) T cells expressed CCR5 and CXCR4 but were relatively resistant to R5 and X4 HIV in vitro. Total CCR6(+) T cells compared with CCR6(-) T cells harbored higher levels of integrated HIV DNA in treatment-naive HIV-infected subjects. The frequency of total CCR6(+) T cells and those of CCR4(+)CCR6(+) and CXCR3(+)CCR6(+) T cells were diminished in chronically infected HIV-positive subjects, despite viral-suppressive therapy. A high-throughput analysis of cytokine profiles identified CXCR3(+)CCR6(+) T cells as a major source of TNF-alpha and CCL20 and demonstrated a decreased TNF-alpha/IL-10 ratio in CXCR3(+)CCR6(-) T cells. Finally, CCR4(+)CCR6(+) and CXCR3(+)CCR6(+) T cells exhibited gut- and lymph node-homing potential. Thus, we identified CCR4(+)CCR6(+) and CXCR3(+)CCR6(+) T cells as highly permissive to HIV replication, with potential to infiltrate and recruit more CCR6(+) T cells into anatomic sites of viral replication. It is necessary that new therapeutic strategies against HIV interfere with viral replication/persistence in discrete CCR6(+) T cell subsets.

CD3 expression distinguishes two gammadeltaT cell receptor subsets with different phenotype and effector function in tuberculous pleurisy

Tuberculous pleurisy is a naturally occurring site of Mycobacterium tuberculosis (Mtb) infection. Herein, we describe the expression of activation, natural killer (NK) and cell migration markers, as well as effector functions from gammadeltaT cells in peripheral blood (PB) and pleural effusion (PE) from tuberculosis patients (TB). We observed a decreased percentage of circulating gammadeltaT from TB patients and differential expression of NK as well as of chemokine receptors on PB and PE. Two subsets of gammadeltaT cells were differentiated by the CD3/gammadeltaT cell receptor (gammadeltaTCR) complex. The gammadeltaTCR(low) subset had a higher CD3 to TCR ratio and was enriched in Vdelta2(+) cells, whereas most Vdelta1(+) cells belonged to the gammadeltaTCR(high) subset. In PB from TB, most gammadeltaTCR(high) were CD45RA(+)CCR7(-) and gammadeltaTCR(low) were CD45RA(+/-)CCR7(+)CXCR3(+). In the pleural space the proportion of CD45RA(-)CCR7(+)CXCR3(+) cells was higher. Neither spontaneous nor Mtb-induced interferon (IFN)-gamma production was observed in PB-gammadeltaT cells from TB; however, PE-gammadeltaT cells showed a strong response. Both PB- and PE-gammadelta T cells expressed surface CD107a upon stimulation with Mtb. Notably, PE-gammadeltaTCR(low) cells were the most potent effector cells. Thus, gammadeltaT cells from PB would acquire a further activated phenotype within the site of Mtb infection and exert full effector functions. As gammadeltaT cells produce IFN-gamma within the pleural space, they would be expected to play a beneficial role in tuberculous pleurisy by helping to maintain a T helper type 1 profile.

Production of interleukin 22 but not interleukin 17 by a subset of human skin-homing memory T cells

Interleukin 22 (IL-22) is a cytokine produced by the T(H)-17 lineage of helper T cells and NK-22 subset of natural killer cells that acts on epithelial cells and keratinocytes and has been linked to skin homeostasis and inflammation. Here we characterize a population of human skin-homing memory CD4(+) T cells that expressed the chemokine receptors CCR10, CCR6 and CCR4 and produced IL-22 but neither IL-17 nor interferon-gamma (IFN-gamma). Clones isolated from this population produced IL-22 only and had low or undetectable expression of the T(H)-17 and T helper type 1 (T(H)1) transcription factors RORgammat and T-bet. The differentiation of T cells producing only IL-22 was efficiently induced in naive T cells by plasmacytoid dendritic cells in an IL-6- and tumor necrosis factor-dependent way. Our findings delineate a previously unknown subset of human CD4(+) effector T cells dedicated to skin pathophysiology.

The role of CXC chemokine ligand (CXCL)12-CXC chemokine receptor (CXCR)4 signalling in the migration of neural stem cells towards a brain tumour

AIMS

It has been shown that neural stem cells (NSCs) migrate towards areas of brain injury or brain tumours and that NSCs have the capacity to track infiltrating tumour cells. The possible mechanism behind the migratory behaviour of NSCs is not yet completely understood. As chemokines are involved in the migration of immune cells in the injured brain, they may also be involved in chemoattraction of NSCs towards a brain tumour.

METHODS

The expression profile of various chemokine receptors in NSCs, harvested from the subventricular zone of adult mice, was investigated by reverse transcriptase- polymerase chain reaction analysis. Furthermore, the functionality of the chemokine receptors was assessed in in vitro chemotaxis assays and calcium signalling experiments. To test the in vivo migration of NSCs, a syngeneic mouse model was developed, whereby a B16F10 melanoma cell line was grafted into one hemisphere and later NSCs were grafted in the contralateral hemisphere. Furthermore, the expression of chemokines in this melanoma cell line was investigated.

RESULTS AND CONCLUSIONS

Adult mouse NSCs functionally express various chemokine receptors of which CXC chemokine receptor (CXCR)4 shows the highest mRNA levels and most pronounced functional responses in vitro. CXC chemokine ligand (CXCL)12, the ligand for CXCR4, is expressed by the melanoma cell line. In this mouse model for metastatic brain tumours, it is shown that NSCs express CXCR4 at their cell membranes while they migrate towards the tumour, which produces CXCL12. It is therefore suggested that the CXCR4/CXCL12 pathway plays a role in the mechanism underlying tumour-mediated attraction of NSCs.

Dendritic cell-based therapeutic cancer vaccines: what we have and what we need

Therapeutic cancer vaccines rely on the immune system to eliminate tumor cells. In contrast to chemotherapy or passive (adoptive) immunotherapies with antibodies or ex vivo-expanded T cells, therapeutic vaccines do not have a direct anti-tumor activity, but aim to reset patients' immune systems to achieve this goal. Recent identification of effective ways of enhancing immunogenicity of tumor-associated antigens, including the use of dendritic cells and other potent vectors of cancer vaccines, provide effective tools to induce high numbers of circulating tumor-specific T cells. However, despite indications that some of the new cancer vaccines may be able to delay tumor recurrence or prolong the survival of cancer patients, their ability to induce cancer regression remains low. Recent reports help to identify and prospectively remove the remaining obstacles towards effective therapeutic vaccination of cancer patients. They indicate that the successful induction of tumor-specific T cells by cancer vaccines is not necessarily associated with the induction of functional cytotoxic T lymphocytes, and that current cancer vaccines may promote undesirable expansion of Treg cells. Furthermore, recent studies also identify the tools to counteract such phenomena, in order to assure the desirable induction of Th1-cytotoxic T lymphocytes, NK-mediated type-1 immunity and appropriate homing of effector cells to tumors.

Chemotactically active proteins of neutrophils

Polymorphonuclear leukocytes (neutrophils) are the first cells that arrive at sites of infection or injury. There, besides their microorganism-targeted effector functions, activated neutrophils secrete numerous chemoattractants that recruit other leukocyte subtypes into the inflamed tissue. First, neutrophil activation leads to the upregulation of the gene expression of several classical chemokines of the CXC and CC families. Second, neutrophil granules contain preformed intracellular storage pools of chemotactically active proteins that are rapidly released upon neutrophil degranulation. The third pathway of generation of chemotactically active proteins by activated neutrophils--shedding and concomitant proteolytic processing of a membrane protein--has recently been demonstrated in our laboratory. In this review, we summarize the essential features of chemoattractant production by neutrophils and their contribution to orchestrating the recruitment of leukocyte subtypes during inflammatory response.

Cyclooxygenase inhibition during allergic sensitization increases STAT6-independent primary and memory Th2 responses

Immune sensitization and memory generation are required for the development of allergic inflammation. Our previous studies demonstrate that the cyclooxygenase (COX) metabolic pathway is actively involved in allergic responses and COX inhibition increases allergic airway inflammation in a STAT6-independent fashion. To test the hypothesis that COX inhibition augments allergic inflammation by enhancing immune sensitization and memory, we sensitized STAT6 knockout mice with an i.p. injection of OVA with aluminum hydroxide as an adjuvant and treated the mice with the COX inhibitor indomethacin or vehicle for analyses of the primary and memory immune responses. We found that COX inhibition during immune sensitization, but not the allergic challenge phase, was necessary and sufficient to increase allergic inflammation. COX inhibition during sensitization increased the numbers of mature dendritic cells and activated CD4 T cells in the spleen and augmented OVA-specific IL-5 and IL-13 responses of the splenic CD4 T cells at day 5 after sensitization. COX inhibition during sensitization also augmented allergic Th2 response to OVA challenge 90 days after the sensitization. Therefore, COX inhibition during allergic sensitization augments allergic responses by enhancing Th2 cell activation and memory generation and the proallergic effect is STAT6-independent. These findings provide a mechanistic explanation for the increased allergic inflammation previously shown in the mice treated with COX inhibitors and in COX-deficient mice and suggest that use of COX-inhibiting drugs during initial allergen exposure may increase the risk of developing allergic responses.

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.

Dimerization of chemokine receptors in living cells: key to receptor function and novel targets for therapy

Chemokine receptors control and mediate a diverse array of physiological and pathogenic processes. Many seven transmembrane (TM) G-protein-coupled receptors (GPCRs), including chemokine receptors, exist as homo- or heterodimers. Growing evidence indicates that the dimeric form is the basic functional structure of these receptors. Hetero-dimerization may allow for enhanced or specific functions of receptors and may be essential for receptor activity. Thus, dimers may provide new targets for chemokine receptor-based therapies. Synthetic peptides of TM regions of chemokine receptors may interfere with homologous interactions and inhibit functional activity of the receptors. Therefore, TM peptides and possibly compounds that target dimers and/or signaling of chemokine receptors may have therapeutic applications.

Tristetraprolin regulates CXCL1 (KC) mRNA stability

mRNAs encoding proinflammatory chemokines are regulated posttranscriptionally via adenine-uridine-rich sequences (AREs) located in the 3' untranslated region of the message, which are recognized by sequence-specific RNA-binding proteins. One ARE binding protein, tristetraprolin (TTP), has been implicated in regulating the stability of several ARE-containing mRNAs, including those encoding TNF-alpha and GM-CSF. In the present report we examined the role of TTP in regulating the decay of the mouse chemokine KC (CXCL1) mRNA. Using tetR-regulated control of transcription in TTP-deficient HEK293 cells, KC mRNA half-life was markedly decreased in the presence of TTP. Deletion and site-specific mutagenesis were used to identify multiple AUUUA sequence determinants responsible for TTP sensitivity. Although a number of studies suggest that the destabilizing activity of TTP is subject to modulation in response to ligands of Toll/IL-1 family receptors, decay mediated by TTP in 293 cells was not sensitive to stimulation with IL-1alpha. Using primary macrophages from wild-type and TTP-deficient mice, KC mRNA instability was found to be highly dependent on TTP. Furthermore, LPS-mediated stabilization of KC mRNA is blocked by inhibition of the p38 MAPK in macrophages from wild-type but not TTP-deficient mice. These findings demonstrate that TTP is the predominant regulator of KC mRNA decay in mononuclear phagocytes acting via multiple 3'-untranslated region-localized AREs. Nevertheless, KC mRNA remains highly unstable in cells that do not express TTP, suggesting that additional determinants of instability and stimulus sensitivity may operate in cell populations where TTP is not expressed.

Cancer treatment: the combination of vaccination with other therapies

Harnessing of the immune system by the development of ‘therapeutic’ vaccines, for the battle against cancer has been the focus of tremendous research efforts over the past two decades. As an illustration of the impressive amounts of data gathered over the past years, numerous antigens expressed on the surface of cancer cells, have been characterized. To this end, recent years research has focussed on characterization of antigens that play an important role for the growth and survival of cancer cells. Anti-apoptotic molecules like survivin that enhance the survival of cancer cells and facilitate their escape from cytotoxic therapies represent prime vaccination candidates. The characterization of a high number of tumor antigens allow the concurrent or serial immunological targeting of different proteins associated with such cancer traits. Moreover, while vaccination in itself is a promising new approach to fight cancer, the combination with additional therapy could create a number of synergistic effects. Herein we discuss the possibilities and prospects of vaccination when combined with other treatments. In this regard, cell death upon drug exposure may be immunogenic or non-immunogenic depending on the specific chemotherapeutics. Also, chemotherapy represents one of several options available for clearance of CD4⁺ Foxp3⁺ regulatory T cells. Moreover, therapies based on monoclonal antibodies may have synergistic potential in combination with vaccination, both when used for targeting of tumor cells and endothelial cells. The efficacy of therapeutic vaccination against cancer will over the next few years be studied in settings taking advantage of strategies in which vaccination is combined with other treatment modalities. These combinations should be based on current knowledge not only regarding the biology of the cancer cell per se, but also considering how treatment may influence the malignant cell population as well as the immune system.

The control of human mesenchymal cell differentiation using nanoscale symmetry and disorder

A key tenet of bone tissue engineering is the development of scaffold materials that can stimulate stem cell differentiation in the absence of chemical treatment to become osteoblasts without compromising material properties. At present, conventional implant materials fail owing to encapsulation by soft tissue, rather than direct bone bonding. Here, we demonstrate the use of nanoscale disorder to stimulate human mesenchymal stem cells (MSCs) to produce bone mineral in vitro, in the absence of osteogenic supplements. This approach has similar efficiency to that of cells cultured with osteogenic media. In addition, the current studies show that topographically treated MSCs have a distinct differentiation profile compared with those treated with osteogenic media, which has implications for cell therapies.