T cell extravasation: demonstration of synergy between activation of CXCR3 and the T cell receptor

Self-assembled and perfusable microvasculature-on-chip for modeling leukocyte trafficking

Leukocyte recruitment from blood to tissue is a process that occurs at the level of capillary vessels during both physiological and pathological conditions. This process is also relevant for evaluating novel adoptive cell therapies, in which the trafficking of therapeutic cells such as chimeric antigen receptor (CAR)-T cells throughout the capillaries of solid tumors is important. Local variations in blood flow, mural cell concentration, and tissue stiffness contribute to the regulation of capillary vascular permeability and leukocyte trafficking throughout the capillary microvasculature. We developed a platform to mimic a biologically functional human arteriole-venule microcirculation system consisting of pericytes (PCs) and arterial and venous primary endothelial cells (ECs) embedded within a hydrogel, which self-assembles into a perfusable, heterogeneous microvasculature. Our device shows a preferential association of PCs with arterial ECs that drives the flow-dependent formation of microvasculature networks. We show that PCs stimulate basement membrane matrix synthesis, which affects both vessel diameter and permeability in a manner correlating with the ratio of ECs to PCs. Moreover, we demonstrate that hydrogel concentration can affect capillary morphology but has no observed effect on vascular permeability. The biological function of our capillary network was demonstrated using an inflammation model, where significantly higher expression of cytokines, chemokines, and adhesion molecules was observed after tumor necrosis factor-alpha (TNF-α) treatment. Accordingly, T cell adherence and transendothelial migration were significantly increased in the immune-activated state. Taken together, our platform allows the generation of a perfusable microvasculature that recapitulates the structure and function of an in vivo capillary bed that can be used as a model for developing potential immunotherapies.

CXCR3 regulates stem and proliferative CD8+ T cells during chronic infection by promoting interactions with DCs in splenic bridging channels

Production of effector CD8+ T cells during persistent infection requires a stable pool of stem-like cells that can give rise to effector cells via a proliferative intermediate population. In infection models marked by T cell exhaustion, this process can be transiently induced by checkpoint blockade but occurs spontaneously in mice chronically infected with the protozoan intracellular parasite Toxoplasma gondii. We observe distinct locations for parasite-specific T cell subsets, implying a link between differentiation and anatomical niches in the spleen. Loss of the chemokine receptor CXCR3 on T cells does not prevent white pulp-to-red pulp migration but reduces interactions with CXCR3 ligand-producing dendritic cells (DCs) and impairs memory-to-intermediate transition, leading to a buildup of memory T cells in the red pulp. Thus, CXCR3 increases T cell exposure to differentiation-inducing signals during red pulp migration, providing a dynamic mechanism for modulating effector differentiation in response to environmental signals.

Bangs et al. report that distinct subsets of CD8+ T cells found during chronic infection occupy distinct regions of the spleen. CXCR3 regulates differentiation of T cells but not their migration. Instead, CXCR3 promotes the interaction of T cells with ligand-producing DCs in bridging channels, resulting in effector differentiation.

Soluble DC-HIL/Gpnmb Modulates T-Lymphocyte Extravasation to Inflamed Skin

Previously, we discovered antigen-presenting cells to express DC-HIL receptor and to secrete its soluble form (soluble DC-HIL [sDC-HIL]), both of which bind to syndecan-4 on T cells and endothelial cells (ECs), with the former binding attenuating T-cell function and the latter binding promoting angiogenesis. In this study, we examined the effects of sDC-HIL binding to EC on T-cell extravasation using an allergic contact dermatitis model in mice. The hapten oxazolone applied to ear skin in sensitized mice upregulated cutaneous expression of sDC-HIL, which downregulated the allergic reaction by reducing transendothelial migration of T cells but not other immune cells (neutrophils and mast cells). Moreover, intravenously infused sDC-HIL bound to EC in blood vessels of oxazolone-challenged skin in a scattered and patchy pattern, and intravital microscopic analysis revealed that blood-circulating T cells firmly adhere to DC-HIL-treated endothelia. This regulatory property of sDC-HIL requires syndecan-4 expression by both EC and T cells. Our findings indicate that the DC-HIL/syndecan-4 pathway mediates a cross-talk between T cells and ECs, regulating the cutaneous immune response by preventing extravasation of activated T cells into inflamed skin.

Contribution of CXCR3-mediated signaling in the metastatic cascade of solid malignancies

Metastasis is a significant cause of the mortality resulting from solid malignancies. The process of metastasis is complex and is regulated by numerous cancer cell-intrinsic and -extrinsic factors. CXCR3 is a chemokine receptor that is frequently expressed by cancer cells, endothelial cells and immune cells. CXCR3A signaling in cancer cells tends to promote the invasive and migratory phenotype of cancer cells. Indirectly, CXCR3 modulates the anti-tumor immune response resulting in variable effects that can permit or inhibit metastatic progression. Finally, the activity of CXCR3B in endothelial cells is generally angiostatic, which limits the access of cancer cells to key conduits to secondary sites. However, the interaction of these activities within a tumor and the presence of opposing CXCR3 splice variants clouds the picture of the role of CXCR3 in metastasis. Consequently, thorough analysis of the contributions of CXCR3 to cancer metastasis is necessary. This review is an in-depth examination of the involvement of CXCR3 in the metastatic process of solid malignancies.

The intratumoral CXCR3 chemokine system is predictive of chemotherapy response in human bladder cancer

Chemotherapy has direct toxic effects on cancer cells; however, long-term cancer control and complete remission are likely to involve CD8⁺ T cell immune responses. To study the role of CD8⁺ T cell infiltration in the success of chemotherapy, we examined patients with muscle invasive bladder cancer (MIBC) who were categorized on the basis of the response to neoadjuvant chemotherapy (NAC). We identified the intratumoral CXCR3 chemokine system (ligands and receptor splice variants) as a critical component for tumor eradication upon NAC in MIBC. Through characterization of CD8⁺ T cells, we found that stem-like T cell subpopulations with abundant CXCR3alt, a variant form of the CXCL11 receptor, responded to CXCL11 in culture as demonstrated by migration and enhanced effector function. In tumor biopsies of patients with MIBC accessed before treatment, CXCL11 abundance correlated with high numbers of tumor-infiltrating T cells and response to NAC. The presence of CXCR3alt and CXCL11 was associated with improved overall survival in MIBC. Evaluation of both CXCR3alt and CXCL11 enabled discrimination between responder and nonresponder patients with MIBC before treatment. We validated the prognostic role of the CXCR3-CXCL11 chemokine system in an independent cohort of chemotherapy-treated and chemotherapy-naïve patients with MIBC from data in TCGA. In summary, our data revealed stimulatory activity of the CXCR3alt-CXCL11 chemokine system on CD8⁺ T cells that is predictive of chemotherapy responsiveness in MIBC. This may offer immunotherapeutic options for targeted activation of intratumoral stem-like T cells in solid tumors.

RNA-Seq analysis of early transcriptional responses to activation in the leukaemic Jurkat E6.1 T cell line

Background: The leukaemia-derived Jurkat E6.1 cell line has been used as a model T cell in the study of many aspects of T cell biology, most notably activation in response to T cell receptor (TCR) engagement. Methods: We present whole-transcriptome RNA-Sequencing data for Jurkat E6.1 cells in the resting state and two hours post-activation via TCR and CD28. We compare early transcriptional responses in the presence and absence of the chemokines CXCL12 and CCL19, and perform a basic comparison between observed transcriptional responses in Jurkat E6.1 cells and those in primary human T cells using publicly deposited data. Results: Jurkat E6.1 cells have many of the hallmarks of standard T cell transcriptional responses to activation, but lack most of the depth of responses in primary cells. Conclusions: These data indicate that Jurkat E6.1 cells hence represent only a highly simplified model of early T cell transcriptional responses.

Investigating T Cell Immunity in Cancer: Achievements and Prospects

T cells play a key role in tumour surveillance, both identifying and eliminating transformed cells. However, as tumours become established they form their own suppressive microenvironments capable of shutting down T cell function, and allowing tumours to persist and grow. To further understand the tumour microenvironment, including the interplay between different immune cells and their role in anti-tumour immune responses, a number of studies from mouse models to clinical trials have been performed. In this review, we examine mechanisms utilized by tumour cells to reduce their visibility to CD8⁺ Cytotoxic T lymphocytes (CTL), as well as therapeutic strategies trialled to overcome these tumour-evasion mechanisms. Next, we summarize recent advances in approaches to enhance CAR T cell activity and persistence over the past 10 years, including bispecific CAR T cell design and early evidence of efficacy. Lastly, we examine mechanisms of T cell infiltration and tumour regression, and discuss the strengths and weaknesses of different strategies to investigate T cell function in murine tumour models.

Single-Molecule, Super-Resolution, and Functional Analysis of G Protein-Coupled Receptor Behavior Within the T Cell Immunological Synapse

A central process in immunity is the activation of T cells through interaction of T cell receptors (TCRs) with agonistic peptide-major histocompatibility complexes (pMHC) on the surface of antigen presenting cells (APCs). TCR-pMHC binding triggers the formation of an extensive contact between the two cells termed the immunological synapse, which acts as a platform for integration of multiple signals determining cellular outcomes, including those from multiple co-stimulatory/inhibitory receptors. Contributors to this include a number of chemokine receptors, notably CXC-chemokine receptor 4 (CXCR4), and other members of the G protein-coupled receptor (GPCR) family. Although best characterized as mediators of ligand-dependent chemotaxis, some chemokine receptors are also recruited to the synapse and contribute to signaling in the absence of ligation. How these and other GPCRs integrate within the dynamic structure of the synapse is unknown, as is how their normally migratory Gαi-coupled signaling is terminated upon recruitment. Here, we report the spatiotemporal organization of several GPCRs, focusing on CXCR4, and the G protein Gαi2 within the synapse of primary human CD4⁺ T cells on supported lipid bilayers, using standard- and super-resolution fluorescence microscopy. We find that CXCR4 undergoes orchestrated phases of reorganization, culminating in recruitment to the TCR-enriched center. This appears to be dependent on CXCR4 ubiquitination, and does not involve stable interactions with TCR microclusters, as viewed at the nanoscale. Disruption of this process by mutation impairs CXCR4 contributions to cellular activation. Gαi2 undergoes active exclusion from the synapse, partitioning from centrally-accumulated CXCR4. Using a CRISPR-Cas9 knockout screen, we identify several diverse GPCRs with contributions to T cell activation, most significantly the sphingosine-1-phosphate receptor S1PR1, and the oxysterol receptor GPR183. These, and other GPCRs, undergo organization similar to CXCR4; including initial exclusion, centripetal transport, and lack of receptor-TCR interactions. These constitute the first observations of GPCR dynamics within the synapse, and give insights into how these receptors may contribute to T cell activation. The observation of broad GPCR contributions to T cell activation also opens the possibility that modulating GPCR expression in response to cell status or environment may directly regulate responsiveness to pMHC.

RNA-Seq analysis of early transcriptional responses to activation in the leukaemic Jurkat E6.1 T cell line

Background: The leukaemia-derived Jurkat E6.1 cell line has been used as a model T cell in the study of many aspects of T cell biology, most notably activation in response to T cell receptor (TCR) engagement. Methods: We present whole-transcriptome RNA-Sequencing data for Jurkat E6.1 cells in the resting state and two hours post-activation via TCR and CD28. We compare early transcriptional responses in the presence and absence of the chemokines CXCL12 and CCL19, and perform a basic comparison between observed transcriptional responses in Jurkat E6.1 cells and those in primary human T cells using publicly deposited data. Results: Jurkat E6.1 cells have many of the hallmarks of standard T cell transcriptional responses to activation, but lack most of the depth of responses in primary cells. Conclusions: These data indicate that Jurkat E6.1 cells hence represent only a highly simplified model of early T cell transcriptional responses.

Tumor infiltrating lymphocytes from acute myeloid leukemia marrow can be reverted to CD45RA+ central memory state by reactivation in SIP (Simulated Infective Protocol)

Simulated Infective Protocol (SIP) is an ex-vivo culture system modeled after the temporal changes of essential cytokines in an acute infection, and previously proven successful in converting T lymphocytes harvested and activated from peripheral blood of normal donors, to revertant CD45RA + Central Memory T lymphocytes (Tcmra) demonstrating properties akin to T Memory Stem Cells (Tscm). In this study, we applied similar SIP on tumor infiltrating lymphocytes (TIL) from bone marrow of patients diagnosed with acute myeloid leukemia (AML), and replicated the feasibility to convert activated TILs into Tcmra phenotype. These revertant Tcmra lymphocytes re-expressed CD45RA+, CCR7+, CD62L + and CD127+, shown improved survivability with longer telomere length, expressed memory properties including higher Eomes to Tbet ratio, and exhibited cytotoxicity against autologous AML blast cells.

Biomarkers of endothelial activation/dysfunction distinguish sub-groups of Ugandan patients with sepsis and differing mortality risks

BACKGROUND

Sepsis is a complex clinical syndrome with substantial heterogeneity. We sought to identify patterns of serum biomarkers of endothelial activation and dysfunction in individuals with sepsis and evaluate subgroup-specific differences in mortality.

METHODS

Adult patients with sepsis (n=426) were consecutively recruited from two hospitals in Uganda. Clinical information was collected and serum concentrations of eleven biomarkers involved in the endothelial response to infection were measured in samples from 315 patients. Latent variable models were fit to evaluate whether the endothelial response to sepsis consists of one unified biological process or multiple processes and to identify subgroups of patients with distinct host-response profiles. Differences in survival at day 28 were evaluated using Kaplan-Meier survival curves.

RESULTS

We identified three patient subgroups characterized by unique host endothelial response profiles. Patients fitting Profile 2 had significantly worse survival (log-rank p<0.001). Four latent factors (Factor 1-4) were identified, each potentially representing distinct biological processes for the endothelial response to sepsis: Factor 1 (CHI3L1, sTREM1, sFLT1); Factor 2 (ANGPT1, PF4, VEGF); Factor 3 (CXCL10, VWF, sICAM1); and Factor 4 (ANGPT2, sTEK).

CONCLUSION

Patient profiles based on patterns of circulating biomarkers of endothelial responses may provide a clinically meaningful way to categorize patients into homogeneous subgroups and may identify patients with a high risk of mortality. Profile 2 may represent dysfunction of the endothelial response to infection.

FUNDING

Primary funding: Investigator-Initiated Award provided by Pfizer, Inc (WMS, STJ). Additional support: Canadian Institutes of Health Research (CIHR) Foundation grant (KCK; FDN-148439) and the Canada Research Chair program (KCK).

Precise Spatiotemporal Interruption of Regulatory T-cell-Mediated CD8+ T-cell Suppression Leads to Tumor Immunity

Tumors can develop despite the presence of competent host immunity via a complex system of immune evasion. One of the most studied factors originating from the host is immune suppression by regulatory T cells (Treg). Ample laboratory and clinical evidence suggests that Treg ablation leads to robust antitumor immune activation. However, how Tregs specifically achieve their suppression in the context of tumor progression is not entirely clear, particularly with regard to the timing and location where Treg inhibition takes place. In this work, we report that Tregs migrate to tumor-draining lymph nodes (TDLN) and block expression of sphingosine-1-phosphate receptor 1 (S1P1) on CD8⁺ T cells. This event trapped the CD8⁺ T cells in the TDLN and served as a facilitating factor for tumor growth. Intriguingly, minimalistic depletion of Tregs in TDLN in a short window following tumor inoculation was sufficient to restore CD8⁺ T-cell activities, which resulted in significant tumor reduction. Similar treatments outside this time frame had no such effect. Our work therefore reveals a subtle feature in tumor biology whereby Tregs appear to be driven by newly established tumors for a programmed encounter with newly activated CD8⁺ T cells in TDLN. Our results suggest the possibility that clinical interception of this step can be tested as a new strategy of cancer therapy, with expected high efficacy and low systemic side effects. SIGNIFICANCE: These findings reveal a strong tumor suppressive effect invoked by minimal blockade of tumor draining lymph node regulatory T cells during early versus late tumorigenesis.

Analysis of cysteine-X-cysteine motif chemokine ligands 9, 10, and 11, their receptor CXCR3, and their possible role on the recruitment of immune cells at the maternal-conceptus interface in pigs

Chemokines play critical roles in the establishment and maintenance of pregnancy in animals. Cysteine-X-cysteine motif chemokine ligand 9 (CXCL9), CXCL10, and CXCL11 are involved in recruiting immune cells by binding to their shared receptor, CXC receptor 3 (CXCR3), in a variety of tissues. This study examined the expression and regulation of chemokines CXCL9, CXCL10, and CXCL11, their receptor CXCR3, and their role at the maternal-conceptus interface in pigs. The endometrium expressed CXCL9, CXCL10, CXCL11, and CXCR3 stage specifically during pregnancy, with the greatest abundance on Day 15 of pregnancy. It was noted that their expression was primarily localized to stromal cells, endothelial cells, or vascular smooth muscle cells in the endometrium. Interferon-γ increased the abundance of CXCL9, CXCL10, CXCL11 mRNAs, but not CXCR3, in endometrial explants. Furthermore, recombinant CXCL9 (rCXCL9), rCXCL10, and rCXCL11 proteins increased migration of cultured peripheral blood mononuclear cells (PBMCs) in a dose-dependent manner. Recombinant CXCL9 and rCXCL10 caused migration of CD4+, CD8+, CD4+CD8+ T cells, and natural killer (NK) cells, and rCXCL11 increased migration of CD4+ T and NK cells in PBMCs. The present study demonstrated that interferon-γ-induced CXCL9, CXCL10, and CXCL11, and their receptor CXCR3 were expressed in the uterus in stage- and cell-type specific manners and increased the migration of T and NK cells, which showed the greatest endometrial infiltration on Day 15 of pregnancy. These results suggest that CXCL9, CXCL10, and CXCL11 may play an important role in the recruitment of immune cells into the endometrium during the implantation period in pigs.

Overview of the Mechanisms that May Contribute to the Non-Redundant Activities of Interferon-Inducible CXC Chemokine Receptor 3 Ligands

The inflammatory chemokines CXCL9, CXCL10, and CXCL11 are predominantly induced by interferon (IFN)-γ and share an exclusive chemokine receptor named CXC chemokine receptor 3 (CXCR3). With a prototype function of directing temporal and spatial migration of activated T cells and natural killer cells, and inhibitory effects on angiogenesis, these CXCR3 ligands have been implicated in infection, acute inflammation, autoinflammation and autoimmunity, as well as in cancer. Intense former research efforts led to recent and ongoing clinical trials using CXCR3 and CXCR3 ligand targeting molecules. Scientific evidence has claimed mutual redundancy, ligand dominance, collaboration or even antagonism, depending on the (patho)physiological context. Most research on their in vivo activity, however, illustrates that CXCL9, CXCL10, and CXCL11 each contribute to the activation and trafficking of CXCR3 expressing cells in a non-redundant manner. When looking into detail, one can unravel a multistep machinery behind final CXCR3 ligand functions. Not only can specific cell types secrete individual CXCR3 interacting chemokines in response to certain stimuli, but also the receptor and glycosaminoglycan interactions, major associated intracellular pathways and susceptibility to processing by particular enzymes, among others, seem ligand-specific. Here, we overview major aspects of the molecular properties and regulatory mechanisms of IFN-induced CXCR3 ligands, and propose that their in vivo non-redundancy is a reflection of the unprecedented degree of versatility that seems inherent to the IFN-related CXCR3 chemokine system.

Human immune compartment comparisons: Optimization of proliferative assays for blood and gut T lymphocytes

The accumulation of peripheral blood late-differentiated memory CD8 T cells with features of replicative (cellular) senescence, including inability to proliferate in vitro, has been extensively studied. Importantly, the abundance of these cells is directly correlated with increased morbidity and mortality in older persons. Of note, peripheral blood contains only 2% of the total body lymphocyte population. By contrast, the gut-associated lymphoid tissue (GALT) is the most extensive lymphoid organ, housing up to 60% of total body lymphocytes, but has never been assessed with respect to senescence profiles. We report here the development of a method for measuring and comparing proliferative capacity of peripheral blood and gut colorectal mucosa-derived CD8 T cells. The protocol involves a 5-day culture of mononuclear leukocyte populations, from blood and gut colorectal mucosa respectively, labeled with 5-(and 6)-carboxyfluorescein diacetate succinimidyl ester (CFSE) and 5-bromo-2'-deoxyuridine (BrdU) and stimulated with anti-CD2/3/28-linked microbeads. Variables tested and optimized as part of the protocol development include: mode of T cell stimulation, CFSE concentration, inclusion of a second proliferation marker, BrdU, culture duration, initial culture concentration, and inclusion of autologous irradiated feeder cells. Moving forward, this protocol demonstrates a significant advance in the ability of researchers to study compartment-specific differences of in vitro proliferative dynamics of CD8 T cells, as an indicator of replicative senescence and immunological aging. The study's two main novel contributions are (1) Optimization and adaptation of standard proliferative dynamics blood T cell protocols for T cells within the mucosal immune system. (2) Introduction of the novel technique of combining CFSE and BrdU staining to do so.

Pancreatic β-Cell production of CXCR3 ligands precedes diabetes onset

Type 1 diabetes mellitus (T1DM) results from immune cell-mediated reductions in function and mass of the insulin-producing β-cells within the pancreatic islets. While the initial trigger(s) that initiates the autoimmune process is unknown, there is a leukocytic infiltration that precedes islet β-cell death and dysfunction. Herein, we demonstrate that genes encoding the chemokines CXCL9, 10, and 11 are primary response genes in pancreatic β-cells and are also elevated as part of the inflammatory response in mouse, rat, and human islets. We further established that STAT1 participates in the transcriptional control of these genes in response to the pro-inflammatory cytokines IL-1β and IFN-γ. STAT1 is phosphorylated within five minutes after β-cell exposure to IFN-γ, with subsequent occupancy at proximal and distal response elements within the Cxcl9 and Cxcl11 gene promoters. This increase in STAT1 binding is coupled to the rapid appearance of chemokine transcript. Moreover, circulating levels of chemokines that activate CXCR3 are elevated in non-obese diabetic (NOD) mice, consistent with clinical findings in human diabetes. We also report herein that mice with genetic deletion of CXCR3 (receptor for ligands CXCL9, 10, and 11) exhibit a delay in diabetes development after being injected with multiple low doses of streptozotocin. Therefore, we conclude that production of CXCL9, 10, and 11 from islet β-cells controls leukocyte migration and activity into pancreatic tissue, which ultimately influences islet β-cell mass and function. © 2016 BioFactors, 42(6):703-715, 2016.

pMHC affinity controls duration of CD8+ T cell-DC interactions and imprints timing of effector differentiation versus expansion

Ozga and colleagues use intravital two-photon microscopy and quantitative whole-organ imaging to reveal the dynamics of early affinity-driven CD8⁺ T cell activation.

During adaptive immune responses, CD8⁺ T cells with low TCR affinities are released early into the circulation before high-affinity clones become dominant at later time points. How functional avidity maturation is orchestrated in lymphoid tissue and how low-affinity cells contribute to host protection remains unclear. In this study, we used intravital imaging of reactive lymph nodes (LNs) to show that T cells rapidly attached to dendritic cells irrespective of TCR affinity, whereas one day later, the duration of these stable interactions ceased progressively with lowering peptide major histocompatibility complex (pMHC) affinity. This correlated inversely BATF (basic leucine zipper transcription factor, ATF-like) and IRF4 (interferon-regulated factor 4) induction and timing of effector differentiation, as low affinity–primed T cells acquired cytotoxic activity earlier than high affinity–primed ones. After activation, low-affinity effector CD8⁺ T cells accumulated at efferent lymphatic vessels for egress, whereas high affinity–stimulated CD8⁺ T cells moved to interfollicular regions in a CXCR3-dependent manner for sustained pMHC stimulation and prolonged expansion. The early release of low-affinity effector T cells led to rapid target cell elimination outside reactive LNs. Our data provide a model for affinity-dependent spatiotemporal orchestration of CD8⁺ T cell activation inside LNs leading to functional avidity maturation and uncover a role for low-affinity effector T cells during early microbial containment.

FLI1 Levels Impact CXCR3 Expression and Renal Infiltration of T Cells and Renal Glycosphingolipid Metabolism in the MRL/lpr Lupus Mouse Strain

The ETS factor Friend leukemia virus integration 1 (FLI1) is a key modulator of lupus disease expression. Overexpressing FLI1 in healthy mice results in the development of an autoimmune kidney disease similar to that observed in lupus. Lowering the global levels of FLI1 in two lupus strains (Fli1(+/-)) significantly improved kidney disease and prolonged survival. T cells from MRL/lpr Fli1(+/-) lupus mice have reduced activation and IL-4 production, neuraminidase 1 expression, and the levels of the glycosphingolipid lactosylceramide. In this study, we demonstrate that MRL/lpr Fli1(+/-) mice have significantly decreased renal neuraminidase 1 and lactosylceramide levels. This corresponds with a significant decrease in the number of total CD3(+) cells, as well as CD4(+) and CD44(+)CD62L(-) T cell subsets in the kidney of MRL/lpr Fli1(+/-) mice compared with the Fli1(+/+) nephritic mice. We further demonstrate that the percentage of CXCR3(+) T cells and Cxcr3 message levels in T cells are significantly decreased and correspond with a decrease in renal CXCR3(+) cells and in Cxcl9 and Cxcl10 expression in the MRL/lpr Fli1(+/-) compared with the Fli1(+/+) nephritic mice. Our results suggest that reducing the levels of FLI1 in MRL/lpr mice may be protective against development of nephritis in part through downregulation of CXCR3, reducing renal T cell infiltration and glycosphingolipid levels.

High IP-10 levels decrease T cell function in HIV-1-infected individuals on ART

HIV-1-infected subjects, despite control of viral replication with ART, have an altered immune cytokine/chemokine milieu. Changes in systemic cytokines and chemokines can alter immune responses. IP-10, in particular, has been associated with pathogenesis in a number of conditions, and we found that IP-10 is increased in serum in subjects who are HIV-1 infected and on stable ART compared with HIV-1-uninfected individuals. In a series of in vitro studies, we found that PBMCs exposed to IP-10 showed a significant decrease in the number of cells capable of secreting IFN-γ, as well as other cytokines, when stimulated with recall antigens. Furthermore, treatment with IP-10 led to decreased antigen-specific calcium signaling and MAPK38 phosphorylation. Importantly, the cytokines, as well as proliferative responses, could be enhanced with an IP-10 Nab. Our findings suggest that IP-10-modulating drugs may potentially enhance T cell responses to vaccination and HIV-1 in HIV+ subjects on ART.

Breast cancer metastasis: demonstration that FOXP3 regulates CXCR4 expression and the response to CXCL12

The X-linked transcription factor FOXP3 is expressed by epithelial cells of organs including the breast, where it is considered a tumour suppressor. The chemokine receptor CXCR4 also regulates the development of breast cancer by stimulating cell migration towards CXCL12-expressing sites of metastatic spread. During activation, human T cells show reciprocal regulation of FOXP3 and CXCR4. This study was designed to examine the role FOXP3 plays in metastatic breast cancer, with a particular focus on its potential to regulate CXCR4. Human breast cancer samples showed significantly decreased FOXP3 protein expression but an increased number of CXCR4 transcripts. In comparison with normal primary breast epithelial cells, FOXP3 was down-regulated at both transcript and protein levels in the breast cancer cell lines MCF-7 and MDA-MB-231. In the invasive MDA-MB-231 cells, the remaining FOXP3 was located predominately within the cytoplasm. Following stable FOXP3 overexpression in MDA-MB-231 cells, significant decreases were observed in the expression of ErbB2/HER2, SKP2, c-MYC, and CXCR4. In contrast, an increase in p21 expression led to inhibition of cell proliferation, with a greater proportion in the G1 phase of the cell cycle suggesting the induction of senescence. Specific knockdown of FOXP3 in normal human breast epithelial cells with siRNA significantly increased ErbB2/HER2, SKP2, c-MYC, and CXCR4, and decreased p21 expression. These cells also showed a significantly increased chemotactic response towards CXCL12, consistent with a role for FOXP3 in the regulation of cell migration. Results from this study are consistent with FOXP3 functioning as an important tumour suppressor in breast cancer. Indeed, the potential functions of FOXP3 in breast epithelium can now be extended to include regulation of CXCR4 expression and response to the pro-metastatic chemokine CXCL12.

Enhancement of antigen-specific CD8 T cell responses by co-delivery of Fc-fused CXCL11

Chemokines have been known to play an important role in eliciting adaptive immune responses by, selectively attracting the innate cellular components to the site of antigen presentation. In this study, we demonstrated that all three CXCR3 ligands, CXCL9, CXCL10, and CXCL11, could act as a strong, genetic adjuvant. Among them, CXCL11 increased vaccine antigen-specific CD8 T cells, including, several cytokine secretions (IFN-γ and TNF-α) to a greater degree than the other two CXCR3 ligands. Fc-fusion of CXCL11 (CXCL11-Fc) induced similar but slightly higher CD8 T cell response, which, appeared to be antigen- (ovalbumin (OVA) vs. human papillomavirus 16 (HPV16) E7) and vaccine, type- (adenovirus vs. DNA vaccine) independent. In addition, the adjuvant effect of CXCL11-Fc was, further confirmed by suppressing tumor growth and extension of survival rates in a therapeutic tumor, model, which was correlated with enhanced antigen-specific CD8 T cell responses. Interestingly, the, enhanced antigen-specific CD8 T cell responses by co-delivery of CXCL11-Fc were associated with CD8, T cell proliferation, followed by increased total and effector memory T cell frequencies. Taken together, our findings provide a novel role of CXCL11 as a strong genetic adjuvant which might be used to, increase antigen-specific CD8 T cell immunity elicited by vaccination.

Inhibition of CXCR4-CXCL12 chemotaxis in melanoma by AMD11070

BACKGROUND

Despite intensive research and novel adjuvant therapies, there is currently no cure for metastatic melanoma. The chemokine receptor CXCR4 controls metastasis to sites such as the liver; however, the therapeutic blockade with the existing agents has proven difficult.

METHODS

AMD11070, a novel orally bioavailable inhibitor of CXCR4, was tested for its ability to inhibit the migration of melanoma cells compared with the commonly described antagonist AMD3100.

RESULTS

AMD11070 abrogated melanoma cell migration and was significantly more effective than AMD3100. Importantly for the clinical context, the expression of B-RAF-V600E did not the affect the sensitivity of AMD11070.

CONCLUSION

Liver-resident myofibroblasts excrete CXCL12, which is able to promote the migration of CXCR4-expressing tumour cells from the blood into the liver. Blockade of this axis by AMD11070 thus represents a novel therapeutic strategy for both B-RAF wild-type and mutated melanomas.

The yin and yang of chemokine receptor activation

Chemokines represent a class of cytokines that control the migration of leucocytes. The human chemokine system comprises 44 ligands and 21 receptors that have evolved to control leucocyte migration. Although chemokines are an attractive therapeutic target for anti-inflammatory intervention, clinical trials of small molecule receptor antagonists have failed to demonstrate efficacy. One often cited explanation for this is the apparent redundancy within the chemokine system, wherein several ligands bind and activate each receptor. The work of Scholten et al. and Nedjai et al. reported in this issue of the British Journal of Pharmacology demonstrates that this redundancy does not exist at the molecular level and provides a powerful insight into the complex nature of chemokine receptor activation.

Treatment with transcatheter arterial chemoembolization induces an increase of the L-selectin(low) CXCR3+ CD8+ T cell subset in patients with hepatocellular carcinoma

BACKGROUND

The purpose of this study was to investigate the impact of treatment with transcatheter arterial chemoembolization on the expression of chemokine receptors on memory T cells around tumor sites in vivo in patients with hepatocellular carcinoma.

METHODS

Blood samples from the hepatic artery and a peripheral vein were collected from 100 patients with hepatocellular carcinoma before and 4 weeks after treatment with transcatheter arterial chemoembolization. Mononuclear cells were isolated and examined for the expression of L-selectin (CD62L) and CXCR3 (CD183) on CD8+ T cells in patients with hepatocellular carcinoma during transcatheter arterial chemoembolization.

RESULTS

Both the frequency and number of L-selectin(low) CXCR3+ proinflammatory effector T cells in patients with hepatocellular carcinoma increased significantly following treatment versus pretreatment (61.92% ± 8.69% versus 24.45% ± 7.36%, P < 0.05, and 18.98 ± 2.33 e7/L versus 6.10 ± 1.21 e7/L, P < 0.001, respectively). There was no significant difference in its frequency whether in the hepatic artery or peripheral vein. Furthermore, the frequency of CD69+ T cells in patients with hepatocellular carcinoma increased from 2.53% ± 0.51% in the artery and 2.38% ± 0.49% in the vein to 3.80% ± 0.62% and 4.48% ± 0.75%, respectively, after treatment (both P < 0.05).

CONCLUSION

Treatment with transcatheter arterial chemoembolization may lead to an increase in L-selectin(low) CXCR3+ effector T cells in patients with hepatocellular carcinoma.

Concomitant active tuberculosis prolongs survival in non-small cell lung cancer: a study in a tuberculosis-endemic country

Background

Adjuvant tumor cell vaccine with chemotherapy against non-small cell lung cancer (NSCLC) shows limited clinical response. Whether it provokes effective cellular immunity in tumor microenvironment is questionable. Concomitant active tuberculosis in NSCLC (TBLC) resembles locoregional immunotherapy of tumor cell vaccine; thus, maximally enriches effective anti-tumor immunity. This study compares the survival and immunological cell profile in TBLC over NSCLC alone.

Methods

Retrospective review of NSCLC patients within 1-year-period of 2007 and follow-up till 2010.

Results

A total 276 NSCLC patients were included. The median survival of TBLC is longer than those of NSCLC alone (11.6 vs. 8.8 month, p<0.01). Active tuberculosis is an independent predictor of better survival with HR of 0.68 (95% CI, 0.48∼0.97). Squamous cell carcinoma (SCC) (55.8 vs. 31.7%, p<0.01) is a significant risk factor for NSCLC with active TB. The median survival of SCC with active tuberculosis is significantly longer than adenocarcinoma or undetermined NSCLC with TB (14.2 vs. 6.6 and 2.8 months, p<0.05). Active tuberculosis in SCC increases the expression of CD3 (46.4±24.8 vs. 24.0±16.0, p<0.05), CXCR3 (35.1±16.4 vs. 19.2±13.3, p<0.01) and IP-10 (63.5±21.9 vs. 35.5±21.0, p<0.01), while expression of FOXP3 is decreased (3.5±0.5 vs. 13.3±3.7 p<0.05, p<0.05). Survival of SCC with high expression of CD3 (12.1 vs. 3.6 month, p<0.05) and CXCR3 (12.1 vs. 4.4 month, p<0.05) is longer than that with low expression.

Conclusions

Active tuberculosis in NSCLC shows better survival outcome. The effective T lymphocyte infiltration in tumor possibly underlies the mechanism. Locoregional immunotherapy of tumor cell vaccine may deserve further researches.

Chemokine receptor CXCR3 agonist prevents human T-cell migration in a humanized model of arthritic inflammation

The recruitment of T lymphocytes during diseases such as rheumatoid arthritis is regulated by stimulation of the chemokine receptors expressed by these cells. This study was designed to assess the potential of a CXCR3-specific small-molecule agonist to inhibit the migration of activated human T cells toward multiple chemokines. Further experiments defined the molecular mechanism for this anti-inflammatory activity. Analysis in vitro demonstrated agonist induced internalization of both CXCR3 and other chemokine receptors coexpressed by CXCR3(+) T cells. Unlike chemokine receptor-specific antagonists, the CXCR3 agonist inhibited migration of activated T cells toward the chemokine mixture in synovial fluid from patients with active rheumatoid arthritis. A humanized mouse air-pouch model showed that intravenous treatment with the CXCR3 agonist prevented inflammatory migration of activated human T cells toward this synovial fluid. A potential mechanism for this action was defined by demonstration that the CXCR3 agonist induces receptor cross-phosphorylation within CXCR3-CCR5 heterodimers on the surface of activated T cells. This study shows that generalized chemokine receptor desensitization can be induced by specific stimulation of a single chemokine receptor on the surface of activated human T cells. A humanized mouse model was used to demonstrate that this receptor desensitization inhibits the inflammatory response that is normally produced by the chemokines present in synovial fluid from patients with active rheumatoid arthritis.

Inflammatory chemokine receptors regulate CD8(+) T cell contraction and memory generation following infection

CD8⁺ T cells lacking CXCR3 and CCR5 expression have impaired contraction and generate an increased number of memory cells after virus infection.

The development of T cell memory from naive precursors is influenced by molecular cues received during T cell activation and differentiation. In this study, we describe a novel role for the chemokine receptors CCR5 and CXCR3 in regulating effector CD8⁺ T cell contraction and memory generation after influenza virus infection. We find that Ccr5^−/− Cxcr3^−/− cells show markedly decreased contraction after viral clearance, leading to the establishment of massive numbers of memory CD8⁺ T cells. Ccr5^−/− Cxcr3^−/− cells show reduced expression of CD69 in the lung during the peak of infection, which coincides with differential localization and the rapid appearance of memory precursor cells. Analysis of single chemokine receptor–deficient cells revealed that CXCR3 is primarily responsible for this phenotype, although there is also a role for CCR5 in the enhancement of T cell memory. The phenotype could be reversed by adding exogenous antigen, resulting in the activation and contraction of Ccr5^−/− Cxcr3^−/− cells. Similar results were observed during chronic Mycobacterium tuberculosis infection. Together, the data support a model of memory CD8⁺ T cell generation in which the chemokine-directed localization of T cells within infected tissues regulates antigen encounter and controls the extent of CD8⁺ T cell activation and differentiation, which ultimately regulates effector versus memory cell fate decisions.

Chemokine receptor CXCR3 facilitates CD8(+) T cell differentiation into short-lived effector cells leading to memory degeneration

Strength of inflammatory stimuli during the early expansion phase plays a crucial role in the effector versus memory cell fate decision of CD8(+) T cells. But it is not known how early lymphocyte distribution after infection has an impact on this process. We demonstrate that the chemokine receptor CXCR3 is involved in promoting CD8(+) T cell commitment to an effector fate rather than a memory fate by regulating T cell recruitment to an antigen/inflammation site. After systemic viral or bacterial infection, the contraction of CXCR3(-/-) antigen-specific CD8(+) T cells is significantly attenuated, resulting in massive accumulation of fully functional memory CD8(+) T cells. Early after infection, CXCR3(-/-) antigen-specific CD8(+) T cells fail to cluster at the marginal zone in the spleen where inflammatory cytokines such as IL-12 and IFN-α are abundant, thus receiving relatively weak inflammatory stimuli. Consequently, CXCR3(-/-) CD8(+) T cells exhibit transient expression of CD25 and preferentially differentiate into memory precursor effector cells as compared with wild-type CD8(+) T cells. This series of events has important implications for development of vaccination strategies to generate increased numbers of antigen-specific memory CD8(+) T cells via inhibition of CXCR3-mediated T cell migration to inflamed microenvironments.

CXCR3 in T cell function

CXCR3 is a chemokine receptor that is highly expressed on effector T cells and plays an important role in T cell trafficking and function. CXCR3 is rapidly induced on naïve cells following activation and preferentially remains highly expressed on Th1-type CD4(+) T cells and effector CD8(+) T cells. CXCR3 is activated by three interferon-inducible ligands CXCL9 (MIG), CXCL10 (IP-10) and CXCL11 (I-TAC). Early studies demonstrated a role for CXCR3 in the trafficking of Th1 and CD8 T cells to peripheral sites of Th1-type inflammation and the establishment of a Th1 amplification loop mediated by IFNγ and the IFNγ-inducible CXCR3 ligands. More recent studies have also suggested that CXCR3 plays a role in the migration of T cells in the microenvironment of the peripheral tissue and lymphoid compartment, facilitating the interaction of T cells with antigen presenting cells leading to the generation of effector and memory cells.

CXCR3 in T cell function

CXCR3 is a chemokine receptor that is highly expressed on effector T cells and plays an important role in T cell trafficking and function. CXCR3 is rapidly induced on naïve cells following activation and preferentially remains highly expressed on Th1-type CD4(+) T cells and effector CD8(+) T cells. CXCR3 is activated by three interferon-inducible ligands CXCL9 (MIG), CXCL10 (IP-10) and CXCL11 (I-TAC). Early studies demonstrated a role for CXCR3 in the trafficking of Th1 and CD8 T cells to peripheral sites of Th1-type inflammation and the establishment of a Th1 amplification loop mediated by IFNγ and the IFNγ-inducible CXCR3 ligands. More recent studies have also suggested that CXCR3 plays a role in the migration of T cells in the microenvironment of the peripheral tissue and lymphoid compartment, facilitating the interaction of T cells with antigen presenting cells leading to the generation of effector and memory cells.

Chemokine receptor expression in tumour islets and stroma in non-small cell lung cancer

BACKGROUND

We have previously demonstrated that tumour islet infiltration by macrophages is associated with extended survival (ES) in NSCLC. We therefore hypothesised that patients with improved survival would have high tumour islet expression of chemokine receptors known to be associated with favourable prognosis in cancer. This study investigated chemokine receptor expression in the tumour islets and stroma in NSCLC.

METHODS

We used immunohistochemistry to identify cells expressing CXCR1, CXCR2, CXCR3, CXCR4, CXCR5 and CCR1 in the tumour islets and stroma in 20 patients with surgically resected NSCLC. Correlations were made with macrophage and mast cell expression.

RESULTS

There was increased expression of CXCR2, CXCR3, and CCR1 in the tumour islets of ES compared with poor survival (PS) patients (p = 0.007, 0.01, and 0.002, respectively). There was an association between 5 year survival and tumour islet CXCR2, CXCR3 and CCR1 density (p = 0.02, 0.003 and <0.001, respectively) as well as stromal CXCR3 density (p = 0.003). There was a positive correlation between macrophage density and CXCR3 expression (rs = 0.520, p = 0.02) and between mast cell density and CXCR3 expression (rs = 0.499, p = 0.03) in the tumour islets.

CONCLUSION

Above median expression of CXCR2, CXCR3 and CCR1 in the tumour islets is associated with increased survival in NSCLC, and expression of CXCR3 correlates with increased macrophage and mast cell infiltration in the tumour islets.