Alpha2 beta1 integrin signaling augments T cell receptor-dependent production of interferon-gamma in human T cells

A unique human cord blood CD8+CD45RA+CD27+CD161+ T-cell subset identified by flow cytometric data analysis using Seurat

Advances in single-cell level analytical techniques, especially cytometric approaches, have led to profound innovation in biomedical research, particularly in the field of clinical immunology. This has resulted in an expansion of high-dimensional data, posing great challenges for comprehensive and unbiased analysis. Conventional manual analysis is thus becoming untenable to handle these challenges. Furthermore, most newly developed computational methods lack flexibility and interoperability, hampering their accessibility and usability. Here, we adapted Seurat, an R package originally developed for single-cell RNA sequencing (scRNA-seq) analysis, for high-dimensional flow cytometric data analysis. Based on a 20-marker antibody panel and analyses of T-cell profiles in both adult blood and cord blood (CB), we showcased the robust capacity of Seurat in flow cytometric data analysis, which was further validated by Spectre, another high-dimensional cytometric data analysis package, and conventional manual analysis. Importantly, we identified a unique CD8+ T-cell population defined as CD8+CD45RA+CD27+CD161+ T cell that was predominantly present in CB. We characterised its IFN-γ-producing and potential cytotoxic properties using flow cytometry experiments and scRNA-seq analysis from a published dataset. Collectively, we identified a unique human CB CD8+CD45RA+CD27+CD161+ T-cell subset and demonstrated that Seurat, a widely used package for scRNA-seq analysis, possesses great potential to be repurposed for cytometric data analysis. This facilitates an unbiased and thorough interpretation of complicated high-dimensional data using a single analytical pipeline and opens a novel avenue for data-driven investigation in clinical immunology.

Migration and homeostasis of regulatory T cells in rheumatoid arthritis

Regulatory T (T_reg) cells are garnering increased attention in research related to autoimmune diseases, including rheumatoid arthritis (RA). They play an essential role in the maintenance of immune homeostasis by restricting effector T cell activity. Reduced functions and frequencies of T_reg cells contribute to the pathogenesis of RA, a common autoimmune disease which leads to systemic inflammation and erosive joint destruction. T_reg cells from patients with RA are characterized by impaired functions and by an altered phenotype. They show increased plasticity towards Th17 cells and a reduced suppressive capacity. Besides the suppressive function of T_reg cells, their effectiveness is determined by their ability to migrate into inflamed tissues. In the past years, new mechanisms involved in T_reg cell migration have been identified. One example of such a mechanism is the phosphorylation of vasodilator-stimulated phosphoprotein (VASP). Efficient migration of T_reg cells requires the presence of VASP. IL-6, a cytokine which is abundantly present in the peripheral blood and in the synovial tissue of RA patients, induces posttranslational modifications of VASP. Recently, it has been shown in mice with collagen-induced arthritis (CIA) that this IL-6 mediated posttranslational modification leads to reduced T_reg cell trafficking. Another protein which facilitates T_reg cell migration is G-protein-signaling modulator 2 (GPSM2). It modulates G-protein coupled receptor functioning, thereby altering the cellular activity initiated by cell surface receptors in response to extracellular signals. The almost complete lack of GPSM2 in T_reg cells from RA patients contributes to their reduced ability to migrate towards inflammatory sites. In this review article, we highlight the newly identified mechanisms of T_reg cell migration and review the current knowledge about impaired T_reg cell homeostasis in RA.

Immune Modulatory Properties of Collagen in Cancer

During tumor growth the extracellular matrix (ECM) undergoes dramatic remodeling. The normal ECM is degraded and substituted with a tumor-specific ECM, which is often of higher collagen density and increased stiffness. The structure and collagen density of the tumor-specific ECM has been associated with poor prognosis in several types of cancer. However, the reason for this association is still largely unknown. Collagen can promote cancer cell growth and migration, but recent studies have shown that collagens can also affect the function and phenotype of various types of tumor-infiltrating immune cells such as tumor-associated macrophages (TAMs) and T cells. This suggests that tumor-associated collagen could have important immune modulatory functions within the tumor microenvironment, affecting cancer progression as well as the efficacy of cancer immunotherapy. The effects of tumor-associated collagen on immune cells could help explain why a high collagen density in tumors is often correlated with a poor prognosis. Knowledge about immune modulatory functions of collagen could potentially identify targets for improving current cancer therapies or for development of new treatments. In this review, the current knowledge about the ability of collagen to influence T cell activity will be summarized. This includes direct interactions with T cells as well as induction of immune suppressive activity in other immune cells such as macrophages. Additionally, the potential effects of collagen on the efficacy of cancer immunotherapy will be discussed.

Fibroblasts as confederates of the immune system

Fibroblastic stromal cells are as diverse, in origin and function, as the niches they fashion in the mammalian body. This cellular variety impacts the spectrum of responses elicited by the immune system. Fibroblast influence on the immune system keeps evolving our perspective on fibroblast roles and functions beyond just a passive structural part of organs. This review discusses the foundations of fibroblastic stromal-immune crosstalk, under the scope of stromal heterogeneity as a basis for tissue-specific tutoring of the immune system. Focusing on the skin as a relevant immunological organ, we detail the complex interactions between distinct fibroblast populations and immune cells that occur during homeostasis, injury repair, scarring, and disease. We further review the relevance of fibroblastic stromal cell heterogeneity and how this heterogeneity is central to regulate the immune system from its inception during embryonic development into adulthood.

The stiffness-controlled release of interleukin-6 by cardiac fibroblasts is dependent on integrin α2β1

Cardiac fibroblasts are able to sense the rigidity of their environment. The present study examines whether the stiffness of the substrate in cardiac fibroblast culture can influence the release of interleukin‐6 (IL‐6), interleukin‐11 (IL‐11) and soluble receptor of IL‐6 (sIL‐6R). It also examines the roles of integrin α2β1 activation and intracellular signalling in these processes. Cardiac fibroblasts were cultured on polyacrylamide gels and grafted to collagen, with an elasticity of E = 2.23 ± 0.8 kPa (soft gel) and E = 8.28 ± 1.06 kPa (stiff gel, measured by Atomic Force Microscope). Flow cytometry and ELISA demonstrated that the fibroblasts cultured on the soft gel demonstrated higher expression of the α2 integrin subunit and increased α2β1 integrin count and released higher levels of IL‐6 and sIL‐6R than those on the stiff gel. Substrate elasticity did not modify fibroblast IL‐11 content. The silencing of the α2 integrin subunit decreased the release of IL‐6. Similar effects were induced by TC‐I 15 (an α2β1 integrin inhibitor). The IL‐6 levels in the serum and heart were markedly lower in α2 integrin‐deficient mice B6.Cg‐Itga2^{tm1.1Tkun/tm1.1Tkun} than wild type. Inhibition of Src kinase by AZM 475271 modifies the IL‐6 level. sIL‐6R secretion is not dependent on α2β1 integrin. Conclusion: The elastic properties of the substrate influence the release of IL‐6 by cardiac fibroblasts, and this effect is dependent on α2β1 integrin and kinase Src activation.

NIH3T3 Directs Memory-Fated CTL Programming and Represses High Expression of PD-1 on Antitumor CTLs

Memory CD8⁺ T cells have long been considered a promising population for adoptive cell therapy (ACT) due to their long-term persistence and robust re-stimulatory response. NIH3T3 is an immortalized mouse embryonic fibroblast cell line. We report that NIH3T3-conditioned medium (CM) can augment effector functions of CTLs following antigen priming and confer phenotypic and transcriptional properties of central memory cells. After NIH3T3-CM-educated CTLs were infused into naïve mice, they predominantly developed to central memory cells. A large number of NIH3T3-CM-educated CTLs with high functionality persisted and infiltrated to tumor mass. In addition, NIH3T3-CM inhibited CTLs expression of PD-1 in vitro and repressed their high expression of PD-1 in tumor microenvironment after adoptive transfer. Consequently, established tumor models showed that infusion of NIH3T3-CM-educated CTLs dramatically improved CTL mediated-antitumor immunity. Furthermore, NIH3T3-CM also promoted human CD8⁺ T cells differentiation into memory cells. These results suggest that NIH3T3-CM-programmed CTLs are good candidates for adoptive transfer in tumor therapy.

Alpha2beta1 Integrin (VLA-2) Protects Activated Human Effector T Cells From Methotrexate-Induced Apoptosis

β1 integrins are critical for T cell migration, survival and costimulation. The integrin α2β1, which is a receptor for collagen, also named VLA-2, is a major costimulatory pathway of effector T cells and has been implicated in arthritis pathogenesis. Herein, we have examined its ability to promote methotrexate (MTX) resistance by enhancing effector T cells survival. Our results show that attachment of anti-CD3-activated human polarized Th17 cells to collagen but not to fibronectin or laminin led to a significant reduction of MTX-induced apoptosis. The anti-CD3+collagen-rescued cells still produce significant amounts of IL-17 and IFNγ upon their reactivation indicating that their inflammatory nature is preserved. Mechanistically, we found that the prosurvival role of anti-CD3+collagen involves activation of the MTX transporter ABCC1 (ATP Binding Cassette subfamily C Member 1). Finally, the protective effect of collagen/α2β1 integrin on MTX-induced apoptosis also occurs in memory CD4⁺ T cells isolated from rheumatoid arthritis (RA) patients suggesting its clinical relevance. Together these results show that α2β1 integrin promotes MTX resistance of effector T cells, and suggest that it could contribute to the development of MTX resistance that is seen in RA.

Formation and phenotypic characterization of CD49a, CD49b and CD103 expressing CD8 T cell populations in human metastatic melanoma

Integrins α1β1 (CD49a), α2β1 (CD49b) and αEβ7 (CD103) mediate retention of lymphocytes in peripheral tissues, and their expression is upregulated on tumor infiltrating lymphocytes (TIL) compared to circulating lymphocytes. Little is known about what induces expression of these retention integrins (RI) nor whether RI define subsets in the tumor microenvironment (TME) with a specific phenotype. Human metastatic melanoma-derived CD8 TIL could be grouped into five subpopulations based on RI expression patterns: RI^neg, CD49a⁺ only, CD49a⁺CD49b⁺, CD49a⁺CD103⁺, or positive for all three RI. A significantly larger fraction of the CD49a⁺ only subpopulation expressed multiple effector cytokines, whereas CD49a⁺CD103⁺ and CD49a⁺CD49b⁺ cells expressed IFNγ only. RI^neg and CD49a⁺CD49b⁺CD103⁺ CD8 TIL subsets expressed significantly less effector cytokines overall. Interestingly, however, CD49a⁺CD49b⁺CD103⁺ CD8 expressed lowest CD127, and highest levels of perforin and exhaustion markers PD-1 and Tim3, suggesting selective exhaustion rather than conversion to memory. To gain insight into RI expression induction, normal donor PBMC were cultured with T cell receptor (TCR) stimulation and/or cytokines. TCR stimulation alone induced two RI⁺ cell populations: CD49a single positive and CD49a⁺CD49b⁺ cells. TNFα and IL-2 each were capable of inducing these populations. Addition of TGFβ to TCR stimulation generated two additional populations; CD49a⁺CD49b^negCD103⁺ and CD49a⁺CD49b⁺CD103^+. Taken together, our findings identify opportunities to modulate RI expression in the TME by cytokine therapies and to generate subsets with a specific RI repertoire in the interest of augmenting immune therapies for cancer or for modulating other immune-related diseases such as autoimmune diseases.

Embryonic Fibroblasts Promote Antitumor Cytotoxic Effects of CD8+ T Cells

Adoptive CD8⁺ T cell therapy has emerged as an important modality for the treatment of cancers. However, the significant drawback of transfused T cells is their poor survival and functionality in response to tumors. To overcome this limitation, an important consideration is exploring a culture condition to generate superior antitumor cytotoxic T lymphocytes (CTLs) for adoptive therapy. Here, we provide a novel approach to generate potent CTL clones in mouse embryonic fibroblast-conditioned medium (MEF-CM). We found CTLs derived with MEF-CM have higher potential in long-term persistence in tumor bearing and non-tumor-bearing mice. Importantly, adoptive transfer of MEF-CM-cultured CTLs dramatically regressed tumor growth and prolonged mice survival. Characterization of MEF-CM-cultured CTLs (effector molecules, phenotypes, and transcription factors) suggests that MEF-CM enhances the effector functions of CD8⁺ T cells in part by the upregulation of the T-box transcription factor eomesodermin. Consequently, MEF-CM enhances the intrinsic qualities of effector CD8⁺ T cells to augment antitumor immunity.

Transient warming events occurring after freezing impairs umbilical cord-derived mesenchymal stromal cells functionality

BACKGROUND

Mesenchymal stromal cells (MSCs) have shown promising results for the treatment of refractory acute graft-versus-host disease. While safety of MSC infusion has been demonstrated, the use of cryopreserved MSCs in clinical trials has raised concerns regarding the retention of their functional activity. This has led to the recommendation by experts in the field to use freshly harvested MSCs, even though this approach is much less practical from a logistic point of view. In the present study, we revisited the impact of cryopreservation on MSC functionality and addressed the possibility that warming events on frozen cells rather than cryopreservation per se could impact MSC functionality.

METHODS

Following controlled-rate freezing to -130°C, umbilical cord-derived MSCs were left at room temperature (RT) for 2-10 min or on dry ice for 10 min, before being transferred into liquid nitrogen (LqN₂). MSCs of each group were subsequently tested (viability, functionality and cellular damage) and compared with their freshly harvested counterparts.

RESULTS

We demonstrated that freshly harvested MSCs as well as cryopreserved MSCs that were left on dry ice following step-down freezing have comparable viability, functionality and integrity. In contrast, cryopreserved MSCs that were left at RT before being transferred into LqN₂ were functionally impaired and showed cellular damage upon thawing even though they exhibited high viability.

DISCUSSION

Warming events after freezing and not cryopreservation per se significantly impair MSC functionality, indicating that cryopreserved MSCs can be an advantageous alternative to freshly harvested cells for therapeutic purposes.

T Cell Migration in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic inflammation in joints, associated with synovial hyperplasia and with bone and cartilage destruction. Although the primacy of T cell-related events early in the disease continues to be debated, there is strong evidence that autoantigen recognition by specific T cells is crucial to the pathophysiology of rheumatoid synovitis. In addition, T cells are key components of the immune cell infiltrate detected in the joints of RA patients. Initial analysis of the cytokines released into the synovial membrane showed an imbalance, with a predominance of proinflammatory mediators, indicating a deleterious effect of Th1 T cells. There is nonetheless evidence that Th17 cells also play an important role in RA. T cells migrate from the bloodstream to the synovial tissue via their interactions with the endothelial cells that line synovial postcapillary venules. At this stage, selectins, integrins, and chemokines have a central role in blood cell invasion of synovial tissue, and therefore in the intensity of the inflammatory response. In this review, we will focus on the mechanisms involved in T cell attraction to the joint, the proteins involved in their extravasation from blood vessels, and the signaling pathways activated. Knowledge of these processes will lead to a better understanding of the mechanism by which the systemic immune response causes local joint disorders and will help to provide a molecular basis for therapeutic strategies.

Sulfonamide inhibitors of α2β1 integrin reveal the essential role of collagen receptors in in vivo models of inflammation

Small molecule inhibitors of α2β1 integrin, a major cellular collagen receptor, have been reported to inhibit platelet function, kidney injury, and angiogenesis. Since α2β1 integrin is abundantly expressed on various inflammation-associated cells, we tested whether recently developed α2β1 blocking sulfonamides have anti-inflammatory properties. Integrin α2β1 inhibitors were shown to reduce the signs of inflammation in arachidonic acid-induced ear edema, PAF stimulated air pouch, ovalbumin-induced skin hypersensitivity, adjuvant arthritis, and collagen-induced arthritis. Thus, these sulfonamides are potential drugs for acute and allergic inflammation, hypersensitivity, and arthritis. One sulfonamide with potent anti-inflammatory activity has previously been reported to be selective for activated integrins, but not to inhibit platelet function. Thus, the experiments also revealed fundamental differences in the action of nonactivated and activated α2β1 integrins in inflammation when compared to thrombosis.

α2β1 Integrin

The α2β1 integrin, also known as VLA-2, GPIa-IIa, CD49b, was first identified as an extracellular matrix receptor for collagens and/or laminins [55, 56]. It is now recognized that the α2β1 integrin serves as a receptor for many matrix and nonmatrix molecules [35, 79, 128]. Extensive analyses have clearly elucidated the α2 I domain structural motifs required for ligand binding, and also defined distinct conformations that lead to inactive, partially active or highly active ligand binding [3, 37, 66, 123, 136, 137, 140]. The mechanisms by which the α2β1 integrin plays a critical role in platelet function and homeostasis have been carefully defined via in vitro and in vivo experiments [76, 104, 117, 125]. Genetic and epidemiologic studies have confirmed human physiology and disease states mediated by this receptor in immunity, cancer, and development [6, 20, 21, 32, 43, 90]. The role of the α2β1 integrin in these multiple complex biologic processes will be discussed in the chapter.

Integrin signaling in cancer cell survival and chemoresistance

Resistance to apoptosis and chemotherapy is a hallmark of cancer cells, and it is a critical factor in cancer recurrence and patient relapse. Extracellular matrix (ECM) via its receptors, the integrins, has emerged as a major pathway contributing to cancer cell survival and resistance to chemotherapy. Several studies over the last decade have demonstrated that ECM/integrin signaling provides a survival advantage to various cancer cell types against numerous chemotherapeutic drugs and against antibody therapy. In this paper, we will discuss the major findings on how ECM/integrin signaling protects tumor cells from drug-induced apoptosis. We will also discuss the potential role of ECM in malignant T-cell survival and in cancer stem cell resistance. Understanding how integrins and their signaling partners promote tumor cell survival and chemoresistance will likely lead to the development of new therapeutic strategies and agents for cancer treatment.

Intrinsic modulation of lymphocyte function by stromal cell network: advance in therapeutic targeting of cancer

Advances in tumor biology have demonstrated a point of critical importance: tumor are established as an intersection of malignant clone cells and surrounding stromal cells. The stroma is composed of nonhematopoietic cells, including connective tissue cells, blood vessels, nerves, fat and smooth muscle cells, in the extracellular matrix niche. Recent studies have demonstrated that stromal cells regulate immune responses by: coordinating lymphocyte homing, differentiation, activation and antigen responses; inducing tolerance; and maintaining immunologic memory. Hence, elucidation of the interaction between stromal cells and lymphocytes is essential for generating effective immunotherapies. In this article, we summarize what is currently known about the interactions between stromal cells and lymphocytes in the tumor microenvironment, as well as potential immunotherapeutic approaches targeting stroma-lymphocyte interactions; both in the context of our work on multiple myeloma, and of recent literature in both solid tumors and hematologic malignancies.

Integrins and their ligands in rheumatoid arthritis

Integrins play an important role in cell adhesion to the extracellular matrix and other cells. Upon ligand binding, signaling is initiated and several intracellular pathways are activated. This leads to a wide variety of effects, depending on cell type. Integrin activation has been linked to proliferation, secretion of matrix-degrading enzymes, cytokine production, migration, and invasion. Dysregulated integrin expression is often found in malignant disease. Tumors use integrins to evade apoptosis or metastasize, indicating that integrin signaling has to be tightly controlled. During the course of rheumatoid arthritis, the synovial tissue is infiltrated by immune cells that secrete large amounts of cytokines. This pro-inflammatory milieu leads to an upregulation of integrin receptors and their ligands in the synovial tissue. As a consequence, integrin signaling is enhanced, leading to enhanced production of matrix-degrading enzymes and cytokines. Furthermore, in analogy to invading tumors, synovial fibroblasts start invading and degrading cartilage, thereby generating extracellular matrix debris that can further activate integrins.

Selective, α2β1 integrin-dependent secretion of il-6 by connective tissue mast cells

Mast cells, critical mediators of inflammation and anaphylaxis, are poised as one of the first lines of defense against external assault. Mast cells release several classes of preformed and de novo synthesized mediators. Cross-linking of the high-affinity FcεRI results in degranulation and the release of preformed, proinflammatory mediators including histamine and serotonin. We previously demonstrated that mast cell activation by Listeria monocytogenes requires the α2β1 integrin for rapid IL-6 secretion both in vivo and in vitro. However, the mechanism of IL-6 release is unknown. Here, we demonstrate the Listeria- and α2β1 integrin-mediated mast cell release of preformed IL-6 without the concomitant release of histamine or β-hexosaminidase. α2β1 integrin-dependent mast cell activation and IL-6 release is calcium independent. In contrast, IgE cross-linking-mediated degranulation is calcium dependent and does not result in IL-6 release, demonstrating that distinct stimuli result in the release of specific mediator pools. These studies demonstrate that IL-6 is presynthesized and stored in connective tissue mast cells and can be released from mast cells in response to distinct, α2β1 integrin-dependent stimulation, providing the host with a specific innate immune response without stimulating an allergic reaction.

Alpha2beta1 integrin is the major collagen-binding integrin expressed on human Th17 cells

Growing evidence indicates that collagen-binding integrins are important costimulatory molecules of effector T cells. In this study, we demonstrate that the major collagen-binding integrin expressed by human Th17 cells is alpha2beta1 (α2β1) or VLA-2, also known as the receptor for collagen I on T cells. Our results show that human naïve CD4(+) T cells cultured under Th17 polarization conditions preferentially upregulate α2β1 integrin rather than α1β1 integrin, which is the receptor for collagen IV on T cells. Double staining analysis for integrin receptors and intracellular IL-17 showed that α2 integrin but not α1 integrin is associated with Th17 cells. Cell adhesion experiments demonstrated that Th17 cells attach to collagen I and collagen II using α2β1 integrin but did not attach to collagen IV. Functional studies revealed that collagens I and II but not collagen IV costimulate the production of IL-17A, IL-17F and IFN-γ by human Th17 cells activated with anti-CD3. These results identify α2β1 integrin as the major collagen receptor expressed on human Th17 cells and suggest that it can be an important costimulatory molecule of Th17 cell responses.

Crosstalk between T cells and bronchial fibroblasts obtained from asthmatic subjects involves CD40L/alpha 5 beta 1 interaction

BACKGROUND

Allergic asthma is characterized by infiltration of inflammatory cells into the airways. T cell-derived cytokines regulate both airway inflammation and remodelling. In the human airways, T cell-fibroblast interactions may have a role in regulating inflammation and remodelling.

OBJECTIVES

To evaluate the effect of bronchial fibroblast-T cell interaction on profibrogenic cytokine release and determine the nature of the molecules involved in this interaction.

METHODS

Human bronchial fibroblasts obtained from healthy and asthmatic donors were co-cultured with purified T cells derived from peripheral blood of the same subjects. IL-6 mRNA and protein levels were measured by real time PCR and ELISA. CD40, CD40L and alpha 5 beta 1 were evaluated by flow cytometry. Bronchial fibroblasts were stimulated with rsCD40L. Neutralisation was performed using neutralizing antibodies anti-CD40L and anti-alpha 5.

RESULTS

Contact of T cells with bronchial fibroblasts up-regulated IL-6 at both gene and protein levels. This effect was significantly higher in fibroblasts from asthmatics than those from controls. Blocking CD40L and alpha 5 beta 1 integrin showed a significant inhibition of IL-6 expression in asthmatics but not in healthy controls. Stimulation of fibroblasts with recombinant soluble CD40L up-regulated IL-6 production in asthmatics but not in controls. Adhesion to fibronectin, a alpha 5 beta 1 integrin ligand, is increased in fibroblasts from asthmatics compared to fibroblasts from controls.

CONCLUSION

These results showed that interaction of bronchial fibroblasts with T cells increases the production of profibrogenic cytokine IL-6. In asthmatic condition this interaction involves CD40L/alpha 5 beta 1. These results suggest that T cells and structural cells crosstalk in asthma may maintain local mucosal inflammation.

Pepscan mapping of viral hemorrhagic septicemia virus glycoprotein G major lineal determinants implicated in triggering host cell antiviral responses mediated by type I interferon

Surface glycoproteins of enveloped virus are potent elicitors of type I interferon (IFN)-mediated antiviral responses in a way that may be independent of the well-studied genome-mediated route. However, the viral glycoprotein determinants responsible for initiating the IFN response remain unidentified. In this study, we have used a collection of 60 synthetic 20-mer overlapping peptides (pepscan) spanning the full length of glycoprotein G (gpG) of viral hemorrhagic septicemia virus (VHSV) to investigate what regions of this protein are implicated in triggering the type I IFN-associated immune responses. Briefly, two regions with ability to increase severalfold the basal expression level of the IFN-stimulated mx gene and to restrict the spread of virus among responder cells were mapped to amino acid residues 280 to 310 and 340 to 370 of the gpG protein of VHSV. In addition, the results obtained suggest that an interaction between VHSV gpG and integrins might trigger the host IFN-mediated antiviral response after VHSV infection. Since it is known that type I IFN plays an important role in determining/modulating the protective-antigen-specific immune responses, the identification of viral glycoprotein determinants directly implicated in the type I IFN induction might be of special interest for designing new adjuvants and/or more-efficient and cost-effective viral vaccines as well as for improving our knowledge on how to stimulate the innate immune system.

T cells and stromal fibroblasts in human tumor microenvironments represent potential therapeutic targets

The immune system of cancer patients recognizes tumor-associated antigens expressed on solid tumors and these antigens are able to induce tumor-specific humoral and cellular immune responses. Diverse immunotherapeutic strategies have been used in an attempt to enhance both antibody and T cell responses to tumors. While several tumor vaccination strategies significantly increase the number of tumor-specific lymphocytes in the blood of cancer patients, most vaccinated patients ultimately experience tumor progression. CD4+ and CD8+ T cells with an effector memory phenotype infiltrate human tumor microenvironments, but most are hyporesponsive to stimulation via the T cell receptor (TCR) and CD28 under conditions that activate memory T cells derived from the peripheral blood of the cancer patients or normal donors. Attempts to identify cells and molecules responsible for the TCR signaling arrest of tumor-infiltrating T cells have focused largely upon the immunosuppressive effects of tumor cells, tolerogenic dendritic cells and regulatory T cells. Here we review potential mechanisms by which human T cell function is arrested in the tumor microenvironment with a focus on the immunomodulatory effects of stromal fibroblasts. Determining in vivo which cells and molecules are responsible for the TCR arrest in human tumor-infiltrating T cells will be necessary to formulate and test strategies to prevent or reverse the signaling arrest of the human T cells in situ for a more effective design of tumor vaccines. These questions are now addressable using novel human xenograft models of tumor microenvironments.

Human immune responses to porcine xenogeneic matrices and their extracellular matrix constituents in vitro

Several tissue engineering approaches for the treatment of cardiovascular diseases are based on a xenogeneic extracellular matrix. However, the application of engineered heart valves has failed in some patients, causing severe signs of inflammation by so far undetermined processes. Therefore we investigated the immune-mediated responses to porcine valve matrices (native, decellularized and glutaraldehyde-fixed) and to purified xenogeneic extracellular matrix proteins (ECMp). The induction of human immune responses in vitro was evaluated by analyzing the co-stimulatory effects of matrices and ECMp collagen and elastin on the proliferation of immune cell sub-populations via CFSE-based proliferation assays. The pattern of cytokine release was also determined. In porcine matrix punches we demonstrated strong immune responses with the native as well as the decellularized type, in contrast to attenuated effects with glutaraldehyde-fixed matrices. Furthermore, our results indicate that collagen type I (porcine and human) and human elastin were able to elicit proliferation in co-stimulation with anti-CD3 antibody, accompanied by a strong release of Th1 cytokines (IFN-gamma, TNF-alpha). In contrast, porcine elastin did not elicit any response at all. This low immunogenic potential of porcine elastin suggests its suitability for the creation of new tissue engineering heart valve scaffolds in the future.

Plant-derived micronutrients suppress monocyte adhesion to cultured human aortic endothelial cell layer by modulating its extracellular matrix composition

Monocyte adhesion to endothelium plays an important role in atherosclerosis. We investigated the effects of micronutrients on monocyte-binding properties of extracellular matrix (ECM) produced by human aortic endothelial cells (AoEC). Confluent cultures of AoEC were exposed to ascorbic acid, quercetin, gotu kola extract (10% asiatic acid), green tea extract (40% epigallocatechin gallate), or a mixture of these micronutrients for 48 hours. AoEC-produced ECM was exposed by differential treatment. U937 monocyte adhesion was assayed by fluorescence. ECM composition was assayed immunochemically and with radiolabeled metabolic precursors. AoEC exposure to micronutrients reduced ECM capacity to bind monocytes in a dose-dependent manner. This effect was accompanied by profound changes in the ECM composition. Correlation analysis revealed that changes in monocyte adhesion to ECM had the strongest positive correlation with ECM content for laminin (CC = 0.9681, P < 0.01), followed by fibronectin, collagens type III, I, and IV, biglycan, heparan sulfate, and elastin. The strongest negative correlation was with chondroitin sulfate (CC = -0.9623, P < 0.01), followed by perlecan and versican. Individual micronutrients had diverse effects on ECM composition and binding properties, and their mixture was the most effective treatment. In conclusion, micronutrient-dependent reduction of monocyte adhesion to endothelium is partly mediated through specific modulation of ECM composition and properties.

Alpha1beta1 integrin and interleukin-7 receptor up-regulate the expression of RANKL in human T cells and enhance their osteoclastogenic function

Activated T cells, through the production of the receptor activator of NF-kappaB ligand (RANKL) cytokine, have been implicated in the osteoclast development and bone loss that are associated with autoimmune diseases such as rheumatoid arthritis. However, the cellular pathways that regulate the expression of RANKL and the induction of osteoclasts are still unclear. In this study, we show that, in human effector CD4(+) T cells, activation of alpha1beta1 integrin and interleukin (IL)-7 receptor (IL-7R) up-regulates the expression and production of RANKL but has no effect on the production of interferon-gamma, an inhibitor of T-cell-mediated osteoclastogenesis. Thus, both alpha1beta1 integrin and IL-7R enhance the ability of these cells to induce the formation of osteoclasts from human monocytes. Furthermore, we found that simultaneous activation of effector CD4(+) T cells via alpha1beta1 integrin and IL-7R synergistically increases the production of RANKL and enhances their osteoclastogenic function. We also show that, although alpha1beta1 integrin does not protect human effector CD4(+) T cells from IL-2-withdrawal-induced apoptosis, it does enhance the pro-survival effect of IL-7, further emphasizing the importance of the alpha1beta1/IL-7R synergistic effect. Together our results identify a new function of alpha1beta1 integrin in T cells and suggest that activation of effector CD4(+) T cells through alpha1beta1 integrin and IL-7R is an important regulatory pathway in T-cell-dependent osteoclastogenesis. Further understanding of the mechanisms by which IL-7R and alpha1beta1 integrin promote T-cell-mediated osteoclastogenesis will lead to new insights into the regulatory pathways of T-cell-dependent bone resorption associated with autoimmune diseases.