Signaling of gp34 (OX40 ligand) induces vascular endothelial cells to produce a CC chemokine RANTES/CCL5

The increased cfRNA of TNFSF4 in peripheral blood at late gestation and preterm labor: its implication as a noninvasive biomarker for premature delivery

Introduction

Given the important roles of immune tolerance and inflammation in both preterm and term labor, some inflammation-related genes could be related to the initiation of labor, even preterm labor. Inspection of cell-free RNA (cfRNA) engaged in inflammation in maternal blood may represent the varied gestational age and may have significant implications for the development of noninvasive diagnostics for preterm birth.

Methods

To identify potential biomarkers of preterm birth, we investigated the cfRNA and exosomal miRNA in the peripheral blood of pregnant women at different gestational ages that undergo term labor or preterm labor. 17 inflammatory initiation-related cfRNAs were screened by overlapping with the targets of decreasing miRNAs during gestation and highly expressed cfRNAs at late gestation in maternal blood. To reveal the origins and mechanisms of these screened cfRNAs, the datasets of single-cell RNA sequencing from peripheral blood mononuclear cells of pregnant women, the fetal lung, and the placenta across different gestational ages were analyzed.

Results

During late gestation, TNFSF4 expression increased exclusively in pro-inflammatory macrophages of maternal blood, whereas its receptor, TNFRSF4, increased expression in T cells from the decidua, which suggested the potential cell-cell communication of maternally-originated pro-inflammatory macrophages with the decidual T cells and contributed to the initiation of labor. Additionally, the cfRNA of TNFSF4 was also increased in preterm labor compared to term labor in the validation cohorts. The EIF2AK2 and TLR4 transcripts were increased in pro-inflammatory macrophages from both fetal lung and placenta but not in those from maternal mononuclear cells at late gestation, suggesting these cfRNAs are possibly derived from fetal tissues exclusively. Moreover, EIF2AK2 and TLR4 transcripts were found highly expressed in the pro-inflammatory macrophages from decidua as well, which suggested these specific fetal-origin macrophages may function at the maternal-fetal interface to stimulate uterine contractions, which have been implicated as the trigger of parturition and preterm labor.

Discussion

Taken together, our findings not only revealed the potential of peripheral TNFSF4 as a novel cfRNA biomarker for noninvasive testing of preterm labor but further illustrated how maternal and fetal signals coordinately modulate the inflammatory process at the maternal-fetal interface, causing the initiation of term or preterm labor.

Expression of CD70 Modulates NO and Redox Status in Endothelial Cells

BACKGROUND

Endothelial dysfunction is a critical component in the pathogenesis of cardiovascular diseases and is closely associated with NO levels and oxidative stress. Here, we report on novel findings linking endothelial expression of CD70 with alterations in NO and reactive oxygen species.

METHODS

CD70 expression was genetically manipulated in human aortic and pulmonary artery endothelial cells. Intracellular NO and hydrogen peroxide (H₂O₂) were measured using genetically encoded biosensors, and cellular phenotypes were assessed.

RESULTS

An unbiased phenome-wide association study demonstrated that polymorphisms in CD70 associate with vascular phenotypes. Endothelial cells treated with CD70-directed short-interfering RNA demonstrated impaired wound closure, decreased agonist-stimulated NO levels, and reduced eNOS (endothelial nitric oxide synthase) protein. This was accompanied by reduced NO bioactivity, increased 3-nitrotyrosine levels, and a decrease in the eNOS binding partner heat shock protein 90. Following treatment with the thioredoxin inhibitor auranofin or with agonist histamine, intracellular H₂O₂ levels increased up to 80% in the cytosol, plasmalemmal caveolae, and mitochondria. There was increased expression of NADPH oxidase 1 complex and gp91phox; expression of copper/zinc and manganese superoxide dismutases was also elevated. CD70 knockdown reduced levels of the H₂O₂ scavenger catalase; by contrast, glutathione peroxidase 1 expression and activity were increased. CD70 overexpression enhanced endothelial wound closure, increased NO levels, and attenuated the reduction in eNOS mRNA induced by TNFα.

CONCLUSIONS

Taken together, these data establish CD70 as a novel regulatory protein in endothelial NO and reactive oxygen species homeostasis, with implications for human vascular disease.

Radiation Augments the Local Anti-Tumor Effect of In Situ Vaccine With CpG-Oligodeoxynucleotides and Anti-OX40 in Immunologically Cold Tumor Models

Introduction

Combining CpG oligodeoxynucleotides with anti-OX40 agonist antibody (CpG+OX40) is able to generate an effective in situ vaccine in some tumor models, including the A20 lymphoma model. Immunologically "cold" tumors, which are typically less responsive to immunotherapy, are characterized by few tumor infiltrating lymphocytes (TILs), low mutation burden, and limited neoantigen expression. Radiation therapy (RT) can change the tumor microenvironment (TME) of an immunologically "cold" tumor. This study investigated the effect of combining RT with the in situ vaccine CpG+OX40 in immunologically "cold" tumor models.

Methods

Mice bearing flank tumors (A20 lymphoma, B78 melanoma or 4T1 breast cancer) were treated with combinations of local RT, CpG, and/or OX40, and response to treatment was monitored. Flow cytometry and quantitative polymerase chain reaction (qPCR) experiments were conducted to study differences in the TME, secondary lymphoid organs, and immune activation after treatment.

Results

An in situ vaccine regimen of CpG+OX40, which was effective in the A20 model, did not significantly improve tumor response or survival in the "cold" B78 and 4T1 models, as tested here. In both models, treatment with RT prior to CpG+OX40 enabled a local response to this in situ vaccine, significantly improving the anti-tumor response and survival compared to RT alone or CpG+OX40 alone. RT increased OX40 expression on tumor infiltrating CD4+ non-regulatory T cells. RT+CpG+OX40 increased the ratio of tumor-infiltrating effector T cells to T regulatory cells and significantly increased CD4+ and CD8+ T cell activation in the tumor draining lymph node (TDLN) and spleen.

Conclusion

RT significantly improves the local anti-tumor effect of the in situ vaccine CpG+OX40 in immunologically "cold", solid, murine tumor models where RT or CpG+OX40 alone fail to stimulate tumor regression.

Exploring the Biomaterial-Induced Secretome: Physical Bone Substitute Characteristics Influence the Cytokine Expression of Macrophages

In addition to their chemical composition various physical properties of synthetic bone substitute materials have been shown to influence their regenerative potential and to influence the expression of cytokines produced by monocytes, the key cell-type responsible for tissue reaction to biomaterials in vivo. In the present study both the regenerative potential and the inflammatory response to five bone substitute materials all based on β-tricalcium phosphate (β-TCP), but which differed in their physical characteristics (i.e., granule size, granule shape and porosity) were analyzed for their effects on monocyte cytokine expression. To determine the effects of the physical characteristics of the different materials, the proliferation of primary human osteoblasts growing on the materials was analyzed. To determine the immunogenic effects of the different materials on human peripheral blood monocytes, cells cultured on the materials were evaluated for the expression of 14 pro- and anti-inflammatory cytokines, i.e., IL-6, IL-10, IL-1β, VEGF, RANTES, IL-12p40, I-CAM, IL-4, V-CAM, TNF-α, GM-CSF, MIP-1α, Il-8 and MCP-1 using a Bio-Plex^® Multiplex System. The granular shape of bone substitutes showed a significant influence on the osteoblast proliferation. Moreover, smaller pore sizes, round granular shape and larger granule size increased the expression of GM-CSF, RANTES, IL-10 and IL-12 by monocytes, while polygonal shape and the larger pore sizes increased the expression of V-CAM. The physical characteristics of a bone biomaterial can influence the proliferation rate of osteoblasts and has an influence on the cytokine gene expression of monocytes in vitro. These results indicate that the physical structure of a biomaterial has a significant effect of how cells interact with the material. Thus, specific characteristics of a material may strongly affect the regenerative potential in vivo.

OX40 expression in neutrophils promotes hepatic ischemia/reperfusion injury

Neutrophils play critical roles during the initial phase of hepatic ischemia/reperfusion injury (HIRI). However, the regulation of neutrophil activation, infiltration, and proinflammatory cytokine secretion has not been fully elucidated. In this study, we revealed that OX40 was expressed by neutrophils, its expression in neutrophils was time-dependently upregulated following HIRI, and Ox40 knockout markedly alleviated liver injury. Compared with wild-type neutrophils, the adoptive transfer of Ox40-/- neutrophils decreased HIRI in neutrophil-depleted Rag2/Il2rg-/- or Ox40-/- mice. Moreover, consistently, the in vitro experiments showed that Ox40 not only prolonged neutrophil survival but also promoted proinflammatory cytokines, ROS production, and even neutrophil chemotaxis. Further investigation demonstrated that the knockout of Ox40 in neutrophils inhibited NF-κB signaling via the TRAF1/2/4 and IKKα/IKKβ/IκBα pathways. OX40L and OX86 stimulation could enhance neutrophil activation and survival in vitro and in vivo. In conclusion, our study provides a new understanding of OX40, which is expressed not only in adaptive immune cells but also in innate immune cells, i.e., neutrophils, contributing to the activation and survival of neutrophils. These findings provide a novel potential therapeutic target for the prevention of HIRI during liver transplantation or hepatic surgery.

Expression of the Immune Checkpoint Modulator OX40 in Acute Lymphoblastic Leukemia Is Associated with BCR-ABL Positivity

OX40 and its ligand are members of the TNF/TNF receptor superfamily, which includes various molecules influencing cellular signaling and function of both tumor and immune cells. The ability of OX40 to promote proliferation and differentiation of activated T cells fueled present attempts to modulate this immune checkpoint to reinforce antitumor immunity. While we recently found evidence for the involvement of OX40 in pathophysiology of acute myeloid leukemia including natural killer (NK) cell immunosurveillance, less is known on its role in acute lymphoblastic leukemia (ALL). In the present study, OX40 expression on ALL cells was significantly associated with positivity for the adverse risk factor BCR-ABL. In line, signaling via OX40 increased metabolic activity of primary ALL cells and resulted in release of cytokines involved in disease pathophysiology. Furthermore, interaction of ALL-expressed OX40 with its cognate ligand on NK cells stimulated ALL cell lysis. The data presented thus not only identify the yet unknown involvement of OX40/OX40L in ALL pathophysiology and NK cell immunosurveillance but also point to the necessity to thoroughly consider the consequences of modulating the OX40/OX40L molecule system beyond its effects on T cells when developing OX40-targeting approaches for cancer immunotherapy.

Arid5a stabilizes OX40 mRNA in murine CD4+ T cells by recognizing a stem-loop structure in its 3'UTR

AT-rich interactive domain-containing protein 5a (Arid5a) is an RNA-binding protein (RBP) required for autoimmunity via stabilization of interleukin-6 (Il6) and signal transducer and activator of transcription 3 (STAT3) mRNAs. However, the roles of Arid5a in Th17 cells and its association with autoimmunity remain unknown. Here, we show that the levels of Arid5a and OX40 are correlated in CD4⁺ T cells under Th17 conditions in an IL-6-dependent manner. Lack of Arid5a in T cells reduced OX40 expression levels and repressed IL-17 production in response to OX40 ligation. Arid5a stabilized OX40 mRNA by recognizing the alternative decay element (ADE)-like stem-loop (SL) in the 3' untranslated region (3'UTR). Interestingly, Arid5a impaired the RNA-destabilizing functions of Regnase-1 and Roquin-1 on OX40 ADE-like SL. In EAE, Arid5a-deficient mice exhibited resistance to EAE, with reduced OX40 expression in CD4⁺ T cells, and the number of CD4⁺ CD45⁺ T cells was decreased in CNS. Furthermore, ameliorated EAE was induced by adoptive transfer of Arid5a^-/- encephalitogenic CD4⁺ T cells expressing less OX40 mRNA and producing less IL-17. In conclusion, our findings indicate that the Arid5a/OX40 axis in CD4⁺ T cells may have important implications in pathogenesis of autoimmune diseases such as EAE.

The Immune Checkpoint Modulator OX40 and Its Ligand OX40L in NK-Cell Immunosurveillance and Acute Myeloid Leukemia

The TNF receptor family member OX40 promotes activation and proliferation of T cells, which fuels efforts to modulate this immune checkpoint to reinforce antitumor immunity. Besides T cells, NK cells are a second cytotoxic lymphocyte subset that contributes to antitumor immunity, particularly in leukemia. Accordingly, these cells are being clinically evaluated for cancer treatment through multiple approaches, such as adoptive transfer of ex vivo expanded polyclonal NK cells (pNKC). Here, we analyzed whether and how OX40 and its ligand (OX40L) influence NK-cell function and antileukemia reactivity. We report that OX40 is expressed on leukemic blasts in a substantial percentage of patients with acute myeloid leukemia (AML) and that OX40 can, after stimulation with agonistic OX40 antibodies, mediate proliferation and release of cytokines that act as growth and survival factors for the leukemic cells. We also demonstrate that pNKC differentially express OX40L, depending on the protocol used for their generation. OX40L signaling promoted NK-cell activation, cytokine production, and cytotoxicity, and disruption of OX40-OX40L interaction impaired pNKC reactivity against primary AML cells. Together, our data implicate OX40/OX40L in disease pathophysiology of AML and in NK-cell immunosurveillance. Our findings indicate that effects of the OX40-OX40L receptor-ligand system in other immune cell subsets and also malignant cells should be taken into account when developing OX40-targeted approaches for cancer immunotherapy. Cancer Immunol Res; 6(2); 209-21. ©2018 AACR.

OX40, OX40L and Autoimmunity: a Comprehensive Review

The tumour necrosis factor receptor OX40 (CD134) is activated by its cognate ligand OX40L (CD134L, CD252) and functions as a T cell co-stimulatory molecule. OX40-OX40L interactions have been proposed as a potential therapeutic target for treating autoimmunity. OX40 is expressed on activated T cells, and in the mouse at rest on regulatory T cells (Treg). OX40L is found on antigen-presenting cells, activated T cells and others including lymphoid tissue inducer cells, some endothelia and mast cells. Expression of both molecules is increased after antigen presentation occurs and also in response to multiple other pro-inflammatory factors including CD28 ligation, CD40L ligation and interferon-gamma signaling. Their interactions promote T cell survival, promote an effector T cell phenotype, promote T cell memory, tend to reduce regulatory function, increase effector cytokine production and enhance cell mobility. In some circumstances, OX40 agonism may be associated with increased tolerance, although timing with respect to antigenic stimulus is important. Further, recent work has suggested that OX40L blockade may be more effective than OX40 blockade in reducing autoimmunity. This article reviews the expression of OX40 and OX40L in health, the effects of their interactions and insights from their under- or over-expression. We then review OX40 and OX40L expression in human autoimmune disease, identified associations of variations in their genes (TNFRSF4 and TNFSF4, respectively) with autoimmunity, and data from animal models of human diseases. A rationale for blocking OX40-OX40L interaction in human autoimmunity is then presented along with commentary on the one trial of OX40L blockade in human disease conducted to date. Finally, we discuss potential problems with clinical use of OX40-OX40L directed pharmacotherapy.

Death Ligands and Autoimmune Demyelination

Death ligands induce apoptosis, which is a cell suicide program leading mainly to selective elimination of an organism's useless cells. Importantly, the dying cell is an active participant in its own demise (“cellular suicide”). Under physiological conditions, apoptosis is most often found during normal cell turnover and tissue homeostasis, embryogenesis, induction and maintenance of immune tolerance, development of the nervous system, and endocrine-dependent tissue atrophy. However, apoptotic processes have also been suggested to contribute to the pathology of the autoimmune demyelinating disease multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis. Here, apoptosis plays a double role. On one hand, impaired apoptosis may result in increased numbers or persistence of activated myelinspecific T cells. On the other hand, local tissue damage involves apoptosis of oligodendrocytes and neurons, leading to the clinical symptoms. In this article, an overview is given of the current knowledge of the roles of apoptosis-mediating and immune regulatory death ligands of the tumor necrosis factor (TNF) family (TNF, lymphotoxin-beta, OX40L [CD134L], CD154 [CD40L], CD95L, CD70 [CD27L], CD153 [CD30L], 4-1BBL [CD137L], TRAIL, TWEAK, BAFF, GITRL) in the pathogenesis of MS and of their implications for related therapeutic strategies.

Role of Tumor Necrosis Factor Superfamily in Neuroinflammation and Autoimmunity

Tumor necrosis factor superfamily (TNFSF) molecules play an important role in the activation, proliferation, differentiation, and migration of immune cells into the central nervous system (CNS). Several TNF superfamily molecules are known to control alloimmunity, autoimmunity, and immunity. Development of transgenic and gene knockout animals, and monoclonal antibodies against TNFSF molecules have increased our understanding of individual receptor-ligand interactions, and their intracellular signaling during homeostasis and neuroinflammation. A strong clinical association has been observed between TNFSF members and CNS autoimmunity such as multiple sclerosis and also in its animal model experimental autoimmune encephalomyelitis. Therefore, they are promising targets for alternative therapeutic options to control autoimmunity. Although, TNFSF ligands are widely distributed and have diverse functions, we have restricted the discussions in this review to TNFSF receptor-ligand interactions and their role in the pathogenesis of neuroinflammation and CNS autoimmunity.

The role of CCL5 in the ability of adipose tissue-derived mesenchymal stem cells to support repair of ischemic regions

Mesenchymal stem cells (MSC) are multipotent and possess high proliferative activity, and thus are thought to be a reliable cell source for cell therapies. Here, we isolated MSC from adult tissues--bone marrow (BM-MSC), dental tissue (DT-MSC), and adipose tissue (AT-MSC)--to compare how autotransplantation of these MSC effectively supports the repair of bone fracture and ischemic tissue. An analysis by in vitro differentiation assays showed no significant difference among these MSC. The degree of calcification at the joint region of bone fracture was higher in mice transplanted with AT-MSC than in mice transplanted with BM-MSC or DT-MSC. To compare the abilities of MSC, characterize how those MSC affect the repair of ischemic tissue, vascular occlusion was performed by ligation of the femoral artery and vein. Of note, the blood flow in the ischemic region rapidly increased in mice injected with AT-MSC, as contrasted with mice injected with BM- or DT-MSC. The number of CD45- and F4/80-positive cells at the femoral region was higher in AT-MSC recipients than in recipients of BM-MSC or DT-MSC. We evaluated the mRNA expression of angiogenic and migration factors in MSC and found the expression of CCL5 mRNA was higher in AT-MSC than in BM-MSC or DT-MSC. Transplantation of AT-MSC with impaired expression of CCL5 clearly showed a significant delay in the recovery of blood flow compared with the control. These findings have fundamental implications for the modulation of AT-MSC in the repair of vasculature and bone fracture.

Lymph node-derived lymphatic endothelial cells express functional costimulatory molecules and impair dendritic cell-induced allogenic T-cell proliferation

Lymphatic endothelial cells (LECs) interact with different immune cells, including T cells within lymph nodes (LNs). However, direct interactions of LECs with immune cells have yet to be investigated. In vitro studies were performed to characterize primary cultures of human LECs derived from LNs in their capacity of interacting with T cells. The results show that LECs express HLA molecules and functional costimulatory molecules needed for T-cell activation. A direct binding of LECs and T cells was detected in cell cultures connected with a clustering of costimulatory molecules on the contact phase. LECs were also able to take up and process antigens. However, major histocompatibility complex class II(+) LECs fail to induce allogeneic T-cell proliferation. Interestingly, supernatants of IFN-γ activated LECs impair proliferation of T cells cocultured with allogeneic dendritic cells, suggesting an inhibitory role of LECs. Indoleamine 2,3 dioxygenase was identified as one inhibitory molecule, which may be responsible for the impaired CD4(+) T-cell proliferation. Our observations suggest a regulatory function for activated LECs on CD4(+) T cells, which may play a role in vivo in the maintenance of the critical balance between tolerance and recall responses.

The role of costimulatory receptors of the tumour necrosis factor receptor family in atherosclerosis

Atherosclerosis is a chronic inflammatory disease that is mediated by both the innate and adaptive immune responses. T lymphocytes, that together with B cells are the cellular effectors of the adaptive immune system, are currently endowed with crucial roles in the development and progression of atherosclerosis. Costimulatory receptors are a class of molecules expressed by T lymphocytes that regulate the activation of T cells and the generation of effector T-cell responses. In this review we present the roles of costimulatory receptors of the tumour necrosis factor receptor (TNFR) superfamily in atherosclerosis and discuss the implications for future therapies that could be used to specifically modulate the immune response of pathogenic T cells in this disease.

Indispensable roles of OX40L-derived signal and epistatic genetic effect in immune-mediated pathogenesis of spontaneous pulmonary hypertension

Background

Pulmonary hypertension (PH) refers to a spectrum of diseases with elevated pulmonary artery pressure. Pulmonary arterial hypertension (PAH) is a disease category that clinically presents with severe PH and that is histopathologically characterized by the occlusion of pulmonary arterioles, medial muscular hypertrophy, and/or intimal fibrosis. PAH occurs with a secondary as well as a primary onset. Secondary PAH is known to be complicated with immunological disorders. The aim of the present study is to histopathologically and genetically characterize a new animal model of PAH and clarify the role of OX40 ligand in the pathogenesis of PAH.

Results

Spontaneous onset of PAH was stably identified in mice with immune abnormality because of overexpression of the tumor necrosis factor (TNF) family molecule OX40 ligand (OX40L). Histopathological and physical examinations revealed the onset of PAH-like disorders in the C57BL/6 (B6) strain of OX40L transgenic mice (B6.TgL). Comparative analysis performed using different strains of transgenic mice showed that this onset depends on the presence of OX40L in the B6 genetic background. Genetic analyses demonstrated a susceptibility locus of a B6 allele to this onset on chromosome 5. Immunological analyses revealed that the excessive OX40 signals in TgL mice attenuates expansion of regulatory T cells the B6 genetic background, suggesting an impact of the B6 genetic background on the differentiation of regulatory T cells.

Conclusion

Present findings suggest a role for the OX40L-derived immune response and epistatic genetic effect in immune-mediated pathogenesis of PAH.

Down-regulation of chemokine Ccl5 gene expression in the NTS of SHR may be pro-hypertensive

OBJECTIVES

Recent studies have demonstrated that pro-inflammatory molecules such as junctional adhesion molecules-1 are highly expressed in the nucleus tractus solitarii (NTS) of the spontaneously hypertensive rat (SHR), compared to normotensive rats (Wistar-Kyoto rats: WKY), suggesting that the NTS of SHR may exhibit an abnormal inflammatory state. In the present study, we tested whether gene expression of inflammatory markers such as cytokines and chemokines is altered in the NTS of SHR and whether this contributes to the hypertensive phenotype in the SHR.

METHODS

We have performed RT Profiler PCR arrays in the NTS of SHR and WKY, which were designed to specifically target major cytokines/chemokines and their receptors. To validate PCR array results quantitative RT-PCR was performed. Microinjection studies using anesthetized rats were also carried out to examine whether validated inflammatory molecules exhibit functional roles on cardiovascular regulation at the level of the NTS.

RESULTS

Five inter-related transcripts were identified to be differentially expressed between the NTS of SHR and WKY. They include chemokine (C-C motif) ligand 5 (Ccl5), and its receptors, chemokine (C-C motif) receptor 1 and 3. All of them were down-regulated in the NTS of SHR compared to WKY. Moreover, we found that the protein Ccl5 microinjected into the NTS significantly decreased baseline arterial pressure and that the response was greater in the SHR compared to the WKY (-33.2±3.2 vs. -8.8±1.6 mmHg, P<0.001), demonstrating that its down-regulation in the NTS may contribute to hypertension in the SHR.

CONCLUSION

We suggest that gene expression of specific chemokines may be down-regulated to protect further inflammatory reactions in the NTS of SHR at the expense of arterial hypertension.

Technical advance: soluble OX40 molecule mimics regulatory T cell modulatory activity on FcεRI-dependent mast cell degranulation

Tregs play a central role in modulating FcεRI-dependent MC effector functions in the course of the allergic response. Cellular interaction depends on the constitutive expression of OX40 on Tregs and the OX40L counterpart on MCs. Study of OX40L signaling on MCs is hampered by the need of a highly purified molecule, which triggers OX40L specifically. We now report that sOX40 mimics the physiological activity of Treg interaction by binding to activated MCs. When treated with sOX40, activated MCs showed decreased degranulation and Ca(++) influx, whereas PLC-γ2 phosphorylation remained unaffected. Once injected into experimental animals, sOX40 not only located within the endothelium but also in parenchyma, where it could be found in close proximity and apparently bound to MCs. This soluble molecule triggers MC-OX40L without the requirement of Tregs, thus allowing study of OX40L signaling pathways in MCs and in other OX40L-expressing cell populations. Importantly, as sOX40 inhibits MC degranulation, it may provide an in vivo therapeutic tool in allergic disease.

Contributions of vascular inflammation in the brainstem for neurogenic hypertension

Essential hypertension is idiopathic although it is accepted as a complex polygenic trait with underlying genetic components, which remain unknown. Our supposition is that primary hypertension involves activation of the sympathetic nervous system. One pivotal region controlling arterial pressure set point is nucleus tractus solitarii (NTS). We recently identified that pro-inflammatory molecules, such as junctional adhesion molecule-1, were over expressed in endothelial cells of the microvasculature supplying the NTS in an animal model of human hypertension (the spontaneously hypertensive rat: SHR) compared to normotensive Wistar Kyoto (WKY) rats. We have also shown endogenous leukocyte accumulation inside capillaries within the NTS of SHR but not WKY rats. Despite the inflammatory state in the NTS of SHR, transcripts of some inflammatory molecules such as chemokine (C-C motif) ligand 5 (Ccl5), and its receptors, chemokine (C-C motif) receptor 1 and 3 were down-regulated in the NTS of SHR compared to WKY rats. This may be compensatory to avoid further strong inflammatory activity. More importantly, we found that down-regulation of Ccl5 in the NTS of SHR may be pro-hypertensive since microinjection of Ccl5 into the NTS of SHR decreased arterial pressure but was less effective in WKY rats. Leukocyte accumulation of the NTS microvasculature may also induce an increase in vascular resistance and hypoperfusion within the NTS; the latter may trigger release of pro-inflammatory molecules which via paracrine signaling may affect central neural cardiovascular activity conducive to neurogenic hypertension. All told, we suggest that vascular inflammation within the brainstem contributes to neurogenic hypertension by multiple pathways.

Nasal cardiac myosin peptide treatment and OX40 blockade protect mice from acute and chronic virally-induced myocarditis

Myocarditis poses a severe health problem, can lead to dilated cardiomyopathy (DCM) and death, and is thought to be triggered by infections. Enteroviruses such as Coxsackie virus B3 (CVB3) have been implicated as a culprit, since they can cause acute and chronic heart disease in susceptible mice. CVB was detected in human cardiac myocytes in some cases, whereas acute CVB infection was thought to have caused death. Here we studied, whether nasal administration of cardiac myosin (CM) major histocompatibility class (MHC) II peptides CM₉₄₇-₉₆₀ and CM₇₃₅-₇₄₇ and OX40 blockade would be able to ameliorate immunopathology and heart disease in BALB/C mice infected with CVB3. We found that nasal CM-peptide prophylactic treatment significantly reduced myocarditis and mortality by enhancing Treg and IL-10 induction and that blockade of OX40 signaling could reduce heart inflammation when administered late during pathogenesis. Altogether, these results chart the way for novel prevention and intervention strategies for viral myocarditis.

Role of CCR5 and its ligands in the control of vascular inflammation and leukocyte recruitment required for acute excitotoxic seizure induction and neural damage

Chemokines may play a role in leukocyte migration across the blood-brain barrier (BBB) during neuroinflammation and other neuropathological processes, such as epilepsy. We investigated the role of the chemokine receptor CCR5 in seizures. We used a rat model based on intraperitoneal kainic acid (KA) administration. Four months before KA injection, adult rats were given femoral intramarrow inoculations of SV (RNAiR5-RevM10.AU1), which carries an interfering RNA (RNAi) against CCR5, plus a marker epitope (AU1), or its monofunctional RNAi-carrying homologue, SV(RNAiR5). This treatment lowered expression of CCR5 in circulating cells. In control rats, seizures induced elevated expression of CCR5 ligands MIP-1α and RANTES in the microvasculature, increased BBB leakage and CCR5(+) cells, as well as neuronal loss, inflammation, and gliosis in the hippocampi. Animals given either the bifunctional or the monofunctional vector were largely protected from KA-induced seizures, neuroinflammation, BBB damage, and neuron loss. Brain CCR5 mRNA was reduced. Rats receiving RNAiR5-bearing vectors showed far greater repair responses: increased neuronal proliferation, and decreased production of MIP-1α and RANTES. Controls received unrelated SV(BUGT) vectors. Decrease in CCR5 in circulating cells strongly protected from excitotoxin-induced seizures, BBB leakage, CNS injury, and inflammation, and facilitated neurogenic repair.

T-cell co-stimulators as anti-inflammatory targets for atherosclerotic disease

Currently, most pharmacological therapies for atherosclerosis rely on lowering plasma low-density lipoprotein levels. Several ongoing clinical trials are testing the possibility of reducing atherosclerosis with drugs that raise plasma high-density lipoprotein levels and/or promote high-density lipoprotein-mediated protective functions. Atherosclerosis can also be treated by targeting inflammatory cells. Recent studies have shown that atherosclerosis is primarily an inflammatory disease and that immune cells, particularly T cells, are found in atherosclerotic lesions throughout the early and late stages. Therefore, therapies that modulate T-cell co-stimulators might slow down the atherosclerosis process by inhibiting T-cell-mediated inflammation.

Control of immunity by the TNFR-related molecule OX40 (CD134)

TNFR/TNF superfamily members can control diverse aspects of immune function. Research over the past 10 years has shown that one of the most important and prominent interactions in this family is that between OX40 (CD134) and its partner OX40L (CD252). These molecules strongly regulate conventional CD4 and CD8 T cells, and more recent data are highlighting their ability to modulate NKT cell and NK cell function as well as to mediate cross-talk with professional antigen-presenting cells and diverse cell types such as mast cells, smooth muscle cells, and endothelial cells. Additionally, OX40-OX40L interactions alter the differentiation and activity of regulatory T cells. Blocking OX40L has produced strong therapeutic effects in multiple animal models of autoimmune and inflammatory disease, and, in line with a prospective clinical future, reagents that stimulate OX40 signaling are showing promise as adjuvants for vaccination as well as for treatment of cancer.

Serial OX40 engagement on CD4+ T cells and natural killer T cells causes allergic airway inflammation

RATIONALE

OX40-OX40 ligand (OX40L) interactions have been proposed to support induction of allergic airway inflammation, which may be attributable to OX40 signaling in CD4(+) helper T cells for adaptive immune responses. However, a possible involvement of natural killer T (NKT) cells in the pathogenesis suggests that the underlying mechanisms are not yet fully elucidated.

OBJECTIVES

We aimed to characterize the OX40-modulated cellular contribution to allergic airway inflammation in a mouse model of house dust mite (HDM) allergen exposure.

METHODS

Mice were sensitized to HDM and, 3 weeks later, challenged with HDM on three consecutive days through the airways. Two days after the last exposure, bronchoalveolar lavage fluids and blood samples and lung tissues were evaluated for the airway inflammation.

MEASUREMENTS AND MAIN RESULTS

The development of HDM-induced eosinophilic airway inflammation was dependent on OX40 of both CD4(+) T cells and NKT cells; OX40 engagement on CD4(+) T cells in the sensitization led to pulmonary OX40L augmentation after the allergen challenge, which stimulated pulmonary NKT cells through OX40 to provide the pathogenic cytokine milieu. This was ablated by OX40L blockade by inhalation of the neutralizing antibody during the challenge, suggesting the therapeutic potential of targeting pulmonary OX40-OX40L interactions. Moreover, OX40 expression in CD4(+) T cells, but not in NKT cells, was reciprocally regulated by the helper T cell type 1-skewing transcription factor Runx3.

CONCLUSIONS

OX40 on not only CD4(+) T cells but also NKT cells is involved in allergic airway inflammation. Notably, pulmonary blockade of OX40 ligation on NKT cells has therapeutic implications.

Role of the chemokines CCL3/MIP-1 alpha and CCL5/RANTES in sponge-induced inflammatory angiogenesis in mice

OBJECTIVE

We examined the potential contribution of CCL3 and CCL5 to inflammatory angiogenesis in mice.

METHODS

Polyester-polyurethane sponges were implanted in mice and blood vessel counting and hemoglobin, myeloperoxidase and N-acetylglucosaminidase measurements used as indexes for vascularization, neutrophil and macrophage accumulation, respectively.

RESULTS

CCL3 and CCL5 were expressed throughout the observation period. Exogenous CCL3 enhanced angiogenesis in WT, but angiogenesis proceeded normally in CCL3(-/-) mice, suggesting that endogenous CCL3 is not critical for sponge-induced angiogenesis in mice. CCL5 expression was detected at day 1, but levels significantly increased thereafter. Exogenous CCL5 reduced angiogenesis in WT mice possible via CCR5 as CCL5 was without an effect in CCR5(-/-) mice. Treatment of WT with the CCR1/CCR5 antagonist, Met-RANTES, prevented neutrophil and macrophage accumulation, but enhanced sponge vascularization.

CONCLUSION

Thus, endogenous CCL3 appears not to play a role in driving sponge-induced inflammatory angiogenesis in mice. The effects of CCL5 were anti-angiogenic and appeared to be mediated via activation of CCR5.

NKT cell-plasmacytoid dendritic cell cooperation via OX40 controls viral infection in a tissue-specific manner

Invariant natural killer T (iNKT) cells promote immune responses to various pathogens, but exactly how iNKT cells control antiviral responses is unclear. Here, we showed that iNKT cells induced tissue-specific antiviral effects in mice infected by lymphocytic choriomeningitis virus (LCMV). Indeed, iNKT cells inhibited viral replication in the pancreas and liver but not in the spleen. In the pancreas, iNKT cells expressed the OX40 molecule and promoted type I interferon (IFN) production by plasmacytoid dendritic cells (pDCs) through OX40-OX40 ligand interaction. Subsequently, this iNKT cell-pDC cooperation attenuated the antiviral adaptive immune response in the pancreas but not in the spleen. The dampening of pancreatic anti-LCMV CD8(+) T cell response prevented tissue damage in transgenic mice expressing LCMV protein in islet beta cells. Thus, this study identifies pDCs as an essential partner of iNKT cells for mounting an efficient, nondeleterious antiviral response in peripheral tissue.

OX40 (CD134) and OX40L

The interaction between OX40 and OX40L plays an important role in antigen-specific T-cell expansion and survival. While OX40 is expressed predominantly on T-lymphocytes early after antigen activation, OX40L is expressed on activated antigen presenting cells and endothelial cells within acute inflammatory environments. We discuss here how ligation of OX40 by OX40L leads to enhanced T-cell survival, along with local inflammatory responses that appear critical for both effective T-cell mediated responses and chronic immune pathologies. We describe how interventions that block or mimic the OX40-OX40L interaction can be applied to treat autoimmune diseases or enhance anti-tumor immune responses. The clinically relevant properties of these agents emphasize the importance of this particular TNFSF-TNFSF in health and disease.

Manipulation of acute inflammatory lung disease

Inflammatory lung disease to innocuous antigens or infectious pathogens is a common occurrence and in some cases, life threatening. Often, the inflammatory infiltrate that accompanies these events contributes to pathology by deleterious effects on otherwise healthy tissue and by compromising lung function by consolidating (blocking) the airspaces. A fine balance, therefore, exists between a lung immune response and immune-mediated damage, and in some the "threshold of ignorance" may be set too low. In most cases, the contributing, potentially offending, cell population or immune pathway is known, as are factors that regulate them. Why then are targeted therapeutic strategies to manipulate them not more commonplace in clinical medicine? This review highlights immune homeostasis in the lung, how and why this is lost during acute lung infection, and strategies showing promise as future immune therapeutics.

Genetic variants of tumor necrosis factor superfamily, member 4 (TNFSF4), and risk of incident atherothrombosis and venous thromboembolism

BACKGROUND

Recent data have implicated tumor necrosis factor (ligand) superfamily, member 4 (TNFSF4) gene variation in myocardial infarction in women; however, no prospective data are available on either incident arterial or venous disorders.

METHODS

We evaluated 2 previously characterized TNFSF4 gene variants (-921C>T and dbSNP rs3850641) with a) incident arterial events using a prospective case-cohort design with 344 incident CVD cases and 2254 control participants, all white, drawn from the Women's Health Study cohort with 10 years of follow-up, and b) venous thromboembolism (VTE) risk using a nested, matched case-control design of 108 white male pairs (drawn from the Physicians' Health Study cohort) and a case-cohort design of white female participants consisting of 125 cases and 2269 controls (drawn from the Women's Health Study cohort), analyzed separately.

RESULTS

Genotype distributions were in Hardy-Weinberg equilibrium. Results from a marker-by-marker regression analysis, adjusting for traditional risk factors, showed a significant association of -921C>T with an increased risk of VTE in women (additive: odds ratio 1.86; 95% CI 1.17-2.92, P = 0.008) in women. Furthermore, using a haplotype-based regression analysis, haplotype C-G was associated with a reduced risk of VTE relative to the referent haplotype, C-A (odds ratio 0.50; 95% CI 0.27-0.92; P = 0.02). In contrast, we found little evidence for an association of the variants/haplotypes with risk of VTE in men or CVD risk in women (as previously reported).

CONCLUSIONS

Our present findings, if corroborated in other prospective investigations, suggest that the TNFSF4 variants tested may be useful indicators for assessing the risk of venous thromboembolism.

Genetic and genomic insights into the molecular basis of atherosclerosis

Atherosclerosis is a complex disease involving genetic and environmental risk factors, acting on their own or in synergy. Within the general population, polymorphisms within genes in lipid metabolism, inflammation, and thrombogenesis are probably responsible for the wide range of susceptibility to myocardial infarction, a fatal consequence of atherosclerosis. Genetic linkage studies have been carried out in both humans and mouse models to identify these polymorphisms. Approximately 40 quantitative trait loci for atherosclerotic disease have been found in humans, and approximately 30 in mice. Recently, genome-wide association studies have been used to identify atherosclerosis-susceptibility polymorphisms. Although discovering new atherosclerosis genes through these approaches remains challenging, the pace at which these polymorphisms are being found is accelerating due to rapidly improving bioinformatics resources and biotechnologies. The outcome of these efforts will not only unveil the molecular basis of atherosclerosis but also facilitate the discovery of drug targets and individualized medication against the disease.

OX40-OX40 ligand interaction through T cell-T cell contact contributes to CD4 T cell longevity

Signals through the OX40 costimulatory receptor on naive CD4 T cells are essential for full-fledged CD4 T cell activation and the generation of CD4 memory T cells. Because the ligand for OX40 is mainly expressed by APCs, including activated B cells, dendritic cells, and Langerhans cells, the OX40-OX40 ligand (OX40L) interaction has been thought to participate in T cell-APC interactions. Although several reports have revealed the expression of OX40L on T cells, the functional significance of its expression on them is still unclear. In this study, we demonstrate that Ag stimulation induced an increase in the surface expression and transcript levels of OX40L in CD4 T cells. Upon contact with OX40-expressing T cells, the cell surface expression of OX40L on CD4 T cells was markedly down-regulated, suggesting that OX40-OX40L binding occurs through a novel T cell-T cell interaction. To investigate the function of this phenomenon, we examined the proliferative response and survival of OX40L-deficient CD4 T cells when challenged with Ag. In vitro studies demonstrated markedly less CD3-induced proliferation of OX40L-deficient CD4 T cells compared with wild-type CD4 T cells. When using TCR transgenic CD4 T cells upon Ag stimulation, survival of OX40L-deficient T cells was impaired. Furthermore, we show that upon antigenic stimulation, fewer OX40L-deficient CD4 T cells than wild-type cells survived following transfer into wild-type and sublethally irradiated recipient mice. Taken together, our findings indicate that OX40L-expressing T cells have an autonomous machinery that provides OX40 signals through a T cell-T cell circuit, creating an additional mechanism for sustaining CD4 T cell longevity.

Roles of OX40 in the pathogenesis and the control of diseases

OX40 belongs to the tumor necrosis factor receptor superfamily, and its expression is restricted to activated T-cells. Ligation of OX40 during T-cell-dendritic cell interaction is crucial for clonal expansion of antigen-specific T-cells and generation of T-cell memory. The ligand of OX40 (OX40L) is expressed not only on dendritic cells but also on other cell types, such as B-cells, vascular endothelial cells, natural killer cells, and mast cells. The pathophysiological relevance of this broad distribution needs further investigation. In particular, OX40L on vascular endothelial cells may play a role in inflammatory vasculitis as well as in atherosclerotic change. Recent studies with animal models have indicated the critical involvement of OX40 in the pathogenesis of a variety of immunologic abnormalities of inflammatory, autoimmune, infectious, allergic, and allotransplantation-related diseases. Blockade of OX40-OX40L interaction has been shown to prevent, cure, or ameliorate these diseases. In contrast, activation of OX40 is known to break an existing state of tolerance in malignancies, leading to a reactivation of antitumor immunity. These findings clearly suggest that the OX40/OX40L system is one of the most promising targets of immune intervention for treatment of these diseases.

Human genetic evidence that OX40 is implicated in myocardial infarction

We recently showed that genetic variants in OX40L are associated with myocardial infarction (MI) and severity of coronary artery disease in human. A number of studies also suggest a possible role for OX40 (the OX40L receptor) as a factor contributing to atherosclerosis. In the present study, the OX40 gene was screened for variants associated with precocious MI, using individuals with MI before the age of 60 and controls. Despite the fact that the OX40 gene is highly conserved between species and that relatively few common genetic variants were encountered, an association with MI was seen for a polymorphism in intron 5 (rs2298212). In silico investigation suggested that genetic variation (rs2298211), linked to this intronic variant, is possibly affecting spliceosome function. Our results provide evidence that variants in human OX40 might influence susceptibility to MI. The relevance of these findings is supported by the vital functions fulfilled by OX40 in mammals as reflected by the high level of evolutionary conservation.

TNF/TNFR family members in costimulation of T cell responses

Several members of the tumor necrosis factor receptor (TNFR) family function after initial T cell activation to sustain T cell responses. This review focuses on CD27, 4-1BB (CD137), OX40 (CD134), HVEM, CD30, and GITR, all of which can have costimulatory effects on T cells. The effects of these costimulatory TNFR family members can often be functionally, temporally, or spatially segregated from those of CD28 and from each other. The sequential and transient regulation of T cell activation/survival signals by different costimulators may function to allow longevity of the response while maintaining tight control of T cell survival. Depending on the disease condition, stimulation via costimulatory TNF family members can exacerbate or ameliorate disease. Despite these complexities, stimulation or blockade of TNFR family costimulators shows promise for several therapeutic applications, including cancer, infectious disease, transplantation, and autoimmunity.

Ligands working as receptors: reverse signaling by members of the TNF superfamily enhance the plasticity of the immune system

The inflammatory cytokine tumor necrosis factor (TNF), as well as most other ligand members of the TNF superfamily, exist both as classical soluble cytokines, but also in the form of type II transmembrane proteins. Both forms possess bioactivity, although some effects are distinct. In addition, an increasing body of evidence suggests that the membrane integrated ligands can receive signals, i.e. act as receptors which can transmit positive and negative feedback signals into the ligand bearing cell. Thus, reverse signaling enables a two-way communication in cell-to-cell signaling, and it is conceivable that this bi-directional signal exchange contributes to the plasticity of the ligand-receptor systems. Reverse signaling mainly has been observed in the immune system and within the TNF superfamily. Its function is only beginning to emerge warranting additional investigation, especially when it comes to therapeutic strategies involving cytokine modulation. This review provides an update of the literature about reverse signaling of transmembrane TNF family members and discusses its potential biological and clinical impact.

Positional identification of TNFSF4, encoding OX40 ligand, as a gene that influences atherosclerosis susceptibility

Ath1 is a quantitative trait locus on mouse chromosome 1 that renders C57BL/6 mice susceptible and C3H/He mice resistant to diet-induced atherosclerosis. The quantitative trait locus region encompasses 11 known genes, including Tnfsf4 (also called Ox40l or Cd134l), which encodes OX40 ligand. Here we report that mice with targeted mutations of Tnfsf4 had significantly (P <or= 0.05) smaller atherosclerotic lesions than did control mice. In addition, mice overexpressing Tnfsf4 had significantly (P <or= 0.05) larger atherosclerotic lesions than did control mice. In two independent human populations, the less common allele of SNP rs3850641 in TNFSF4 was significantly more frequent (P <or= 0.05) in individuals with myocardial infarction than in controls. We therefore conclude that Tnfsf4 underlies Ath1 in mice and that polymorphisms in its human homolog TNFSF4 increase the risk of myocardial infarction in humans.

Role of T cell costimulation in anti-viral immunity

Members of both the CD28 and TNFR families can have costimulatory roles in T cell activation. Gene targeted mice as well as in vivo blocking experiments have established distinct roles for CD28/B7; ICOS/ICOSL; CD27/CD70; 4-1BB/4-1BBL and OX40/OX40L during viral infection. Many issues remain to be addressed, including the timing and location of the interactions, the possibility of partial redundancy between related family members and the molecular basis for the specific phenotypes observed in the different gene targeted mice.

Cross-talk between activated human NK cells and CD4+ T cells via OX40-OX40 ligand interactions

It is important to understand which molecules are relevant for linking innate and adaptive immune cells. In this study, we show that OX40 ligand is selectively induced on IL-2, IL-12, or IL-15-activated human NK cells following stimulation through NKG2D, the low affinity receptor for IgG (CD16) or killer cell Ig-like receptor 2DS2. CD16-activated NK cells costimulate TCR-induced proliferation, and IFN-gamma produced by autologous CD4+ T cells and this process is dependent upon expression of OX40 ligand and B7 by the activated NK cells. These findings suggest a novel and unexpected link between the natural and specific immune responses, providing direct evidence for cross-talk between human CD4+ T cells and NK receptor-activated NK cells.

Antigen presentation by the endothelium: a green light for antigen-specific T cell trafficking?

The functional consequences of recognition of antigen displayed by the endothelium during T cell extravasation in the development of an immune response have been a matter of debate for a long time. Most investigations have focused on the induction of proliferative responses and cytokine production by T cells. In parallel, endothelial cells have been shown to express costimulatory molecules with positive and negative regulatory effects on T cell responses. Recent studies have provided an alternative view of the antigen presenting cell function of endothelial cells, suggesting that cognate recognition of the endothelium by trafficking T cells is a key event in selecting the migration of antigen-specific lymphocytes into the site of inflammation.

Categorically distinct acute stressors elicit dissimilar transcriptional profiles in the paraventricular nucleus of the hypothalamus

The paraventricular hypothalamic nucleus (PVH) is a key site for integrating neuroendocrine, autonomic, and behavioral adjustments to diverse homeostatic challenges, including "physiological" (e.g., infection or hemorrhage) and "emotional" [e.g., restraint (RST) or footshock] stresses. Both types of challenges ultimately converge to activate common response systems represented in PVH, including the hypothalamo-pituitary-adrenal axis and the sympathoadrenal system. Oligonucleotide microarrays (U74A; Affymetrix, Santa Clara, CA) were used to compare and contrast gene expression profiles in the PVH elicited at 1 and 3 hr after acute exposure to representative physiological [intraperitoneal injection of 10 microg lipopolysaccharide (LPS)] and emotional (30 min RST) stressors. In general, the two challenges recruited relatively few genes in common, with the degree of overlap varying across functional classes of genes. The greatest degree of commonality was seen among signaling molecules and neuropeptides, whereas transcription factors upregulated by RST and LPS were largely distinct. Unexpectedly, RST induced a number of immune-related molecules, which were not regulated by LPS. Hybridization histochemical analyses localized a subset of responsive transcripts to the PVH and/or immediately adjoining regions. Immunerelated molecules in particular distributed broadly to vascular and other barrier-associated cell types. These global transcriptional profiles inform the search for early (transcription factors) and late (target genes) mechanisms in the modulation of PVH, and generalized CNS, responses to categorically distinct stressors.

Acute stress evokes selective mobilization of T cells that differ in chemokine receptor expression: a potential pathway linking immunologic reactivity to cardiovascular disease

T lymphocytes and monocytes/macrophages are the most abundant cells found in the atherosclerotic plaque. These cells can migrate towards the activated endothelium through the local release of chemotactic cytokines, or chemokines. Given the important role of leukocyte migration in atherosclerosis and the role of stress in mediating leukocyte trafficking, the present study examined the effects of an acute stressor on the redistribution of T cells (CD3+) and monocytes that express the chemokine receptors CCR5, CCR6, CXCR1, CXCR2, CXCR3, and CXCR4. Forty-four undergraduate students underwent a public speaking task. The acute stressor induced sympathetic cardiac activation, parasympathetic cardiac withdrawal, lymphocytosis, and monocytosis (all p<.001). Although the total number of T lymphocytes did not change, there was a selective increase in the number of circulating T cells expressing CXCR2, CXCR3, and CCR5. The ligands of these receptors are chemokines known to be secreted by activated endothelial cells. Analyses of individual differences in stress-induced responses demonstrated a positive relationship between sympathetic cardiac reactivity and mobilization of the various T cell subsets (.35<r<.56;p<.05). For the monocytes, all sub-populations increased in parallel with total monocyte numbers, with no relation to changes in sympathetic cardiac drive. These results indicate that acute stress induces a mobilization of T cells that are primed to respond to inflamed endothelium. Acute stressors may thus promote the recruitment of circulating immune cells into the sub-endothelia, and therefore accelerate atherosclerotic plaque formation and potentially contribute to the complications that follow acute stressful events. This mechanism may help explain the link between stress, reactivity, and cardiovascular disease.