Oligoclonal T cell expansions in atherosclerotic lesions of apolipoprotein E-deficient mice

Atherosclerosis and the role of immune cells

Atherosclerosis is a chronic inflammatory disease arising from lipids, specifically low-density lipoproteins, and leukocytes. Following the activation of endothelium with the expression of adhesion molecules and monocytes, inflammatory cytokines from macrophages, and plasmacytoid dendritic cells, high levels of interferon (IFN)-α and β are generated upon the activation of toll-like receptor-9, and T-cells, especially the ones with Th1 profile, produce pro-inflammatory mediators such as IFN-γ and upregulate macrophages to adhere to the endothelium and migrate into the intima. This review presents an exhaustive account for the role of immune cells in the atherosclerosis.

The macrophage-TCRαβ is a cholesterol-responsive combinatorial immune receptor and implicated in atherosclerosis

Recent evidence indicates constitutive expression of a recombinatorial TCRαβ immune receptor in mammalian monocytes and macrophages. Here, we demonstrate in vitro that macrophage-TCRβ repertoires are modulated by atherogenic low density cholesterol (LDL) and high-density cholesterol (HDL). In vivo, analysis of freshly obtained artery specimens from patients with severe carotid atherosclerosis reveals massive abundance of TCRαβ(+) macrophages within the atherosclerotic lesions. Experimental atherosclerosis in mouse carotids induces accumulation of TCR bearing macrophages in the vascular wall and TCR deficient rag(-/-) mice have an altered macrophage-dependent inflammatory response. We find that the majority of TCRαβ bearing macrophages are localized in the hot spot regions of the atherosclerotic lesions. Advanced carotid artery lesions express highly restricted TCRαβ repertoires that are characterized by a striking usage of the Vβ22 and Vβ16 chains. This together with a significant degree of interindividual lesion repertoire sharing suggests the existence of atherosclerosis-associated TCRαβ signatures. Our results implicate the macrophage-TCRαβ combinatorial immunoreceptor in atherosclerosis and thus identify an as yet unknown adaptive component in the innate response-to-injury process that underlies this macrophage-driven disease.

A journey in science: medical scientist in translation

Real innovations in medicine and science are historic and singular; the stories behind each occurrence are precious. At Molecular Medicine we have established the Anthony Cerami Award in Translational Medicine to document and preserve these histories. The monographs recount the seminal events as told in the voice of the original investigators who provided the crucial early insight. These essays capture the essence of discovery, chronicling the birth of ideas that created new fields of research; and launched trajectories that persisted and ultimately influenced how disease is prevented, diagnosed and treated. In this volume, the Cerami Award Monograph is by Göran K Hansson, MD, PhD, Karolinska Institute. A visionary in the field of cardiovascular research, this is the story of Dr. Hansson's scientific journey.

Oligoclonal CD8+ T cells play a critical role in the development of hypertension

Recent studies have emphasized a role of adaptive immunity, and particularly T cells, in the genesis of hypertension. We sought to determine the T-cell subtypes that contribute to hypertension and renal inflammation in angiotensin II-induced hypertension. Using T-cell receptor spectratyping to examine T-cell receptor usage, we demonstrated that CD8(+) cells, but not CD4(+) cells, in the kidney exhibited altered T-cell receptor transcript lengths in Vβ3, 8.1, and 17 families in response to angiotensin II-induced hypertension. Clonality was not observed in other organs. The hypertension caused by angiotensin II in CD4(-/-) and MHCII(-/-) mice was similar to that observed in wild-type mice, whereas CD8(-/-) mice and OT1xRAG-1(-/-) mice, which have only 1 T-cell receptor, exhibited a blunted hypertensive response to angiotensin II. Adoptive transfer of pan T cells and CD8(+) T cells but not CD4(+)/CD25(-) cells conferred hypertension to RAG-1(-/-) mice. In contrast, transfer of CD4(+)/CD25(+) cells to wild-type mice receiving angiotensin II decreased blood pressure. Mice treated with angiotensin II exhibited increased numbers of kidney CD4(+) and CD8(+) T cells. In response to a sodium/volume challenge, wild-type and CD4(-/-) mice infused with angiotensin II retained water and sodium, whereas CD8(-/-) mice did not. CD8(-/-) mice were also protected against angiotensin-induced endothelial dysfunction and vascular remodeling in the kidney. These data suggest that in the development of hypertension, an oligoclonal population of CD8(+) cells accumulates in the kidney and likely contributes to hypertension by contributing to sodium and volume retention and vascular rarefaction.

Adaptive (T and B cells) immunity and control by dendritic cells in atherosclerosis

Chronic inflammation in response to lipoprotein accumulation in the arterial wall is central in the development of atherosclerosis. Both innate and adaptive immunity are involved in this process. Adaptive immune responses develop against an array of potential antigens presented to effector T lymphocytes by antigen-presenting cells, especially dendritic cells. Functional analysis of the role of different T-cell subsets identified the Th1 responses as proatherogenic, whereas regulatory T-cell responses exert antiatherogenic activities. The effect of Th2 and Th17 responses is still debated. Atherosclerosis is also associated with B-cell activation. Recent evidence established that conventional B-2 cells promote atherosclerosis. In contrast, innate B-1 B cells offer protection through secretion of natural IgM antibodies. This review discusses the recent development in our understanding of the role of T- and B-cell subsets in atherosclerosis and addresses the role of dendritic cell subpopulations in the control of adaptive immunity.

Artery Tertiary Lymphoid Organs Contribute to Innate and Adaptive Immune Responses in Advanced Mouse Atherosclerosis

Tertiary lymphoid organs emerge in tissues in response to nonresolving inflammation. Recent research characterized artery tertiary lymphoid organs in the aorta adventitia of aged apolipoprotein E–deficient mice. The atherosclerosis-associated lymphocyte aggregates are organized into distinct compartments, including separate T-cell areas harboring conventional, monocyte-derived, lymphoid, and plasmacytoid dendritic cells, as well as activated T-cell effectors and memory cells; B-cell follicles containing follicular dendritic cells in activated germinal centers; and peripheral niches of plasma cells. Artery tertiary lymphoid organs show marked neoangiogenesis, aberrant lymphangiogenesis, and extensive induction of high endothelial venules. Moreover, newly formed lymph node–like conduits connect the external lamina with high endothelial venules in T-cell areas and also extend into germinal centers. Mouse artery tertiary lymphoid organs recruit large numbers of naïve T cells and harbor lymphocyte subsets with opposing activities, including CD4 + and CD8 + effector and memory T cells, natural and induced CD4 + regulatory T cells, and memory B cells at different stages of differentiation. These data suggest that artery tertiary lymphoid organs participate in primary immune responses and organize T- and B-cell autoimmune responses in advanced atherosclerosis. In this review, we discuss the novel concept that pro- and antiatherogenic immune responses toward unknown arterial wall–derived autoantigens may be organized by artery tertiary lymphoid organs and that disruption of the balance between pro- and antiatherogenic immune cell subsets may trigger clinically overt atherosclerosis.

Distinct functions of specialized dendritic cell subsets in atherosclerosis and the road ahead

Atherosclerotic vascular disease is modulated by immune mechanisms. Dendritic cells (DCs) and T cells are present within atherosclerotic lesions and function as central players in the initiation and modulation of adaptive immune responses. In previous years, we have studied the functional contribution of distinct DC subsets in disease development, namely, that of CCL17-expressing DCs as well as that of plasmacytoid DCs that play specialized roles in disease development. This review focuses on important findings gathered in these studies and dissects the multifaceted contribution of CCL17-expressing DCs and pDCs to the pathogenesis of atherosclerosis. Furthermore, an outlook on future challenges faced when studying DCs in this detrimental disease are provided, and hurdles that will need to be overcome in order to enable a better understanding of the contribution of DCs to atherogenesis are discussed, a prerequisite for their therapeutic targeting in atherosclerosis.

Effect of the Kv1.3 voltage-gated potassium channel blocker PAP-1 on the initiation and progress of atherosclerosis in a rat model

Acute coronary syndrome is a serious medical emergency. It occurs when an atherosclerotic plaque ruptures, leading to thrombus formation within a coronary artery. Previous studies have shown that T cells are involved in the initiation and progression of acute coronary syndrome. CD4(+)CD28(null) T lymphocytes increase in atherosclerotic plaque, and voltage-gated potassium channel Kv1.3 blockers can suppress the function of these cells in vitro by preventing exocytosis of their cytoplasmic granules. The purpose of this study was to investigate the effect of PAP-1, a small molecule voltage-gated potassium channel Kv1.3 blocker, on the development of atherosclerosis (AS) in a rat model and the potential mechanism for this effect. Plasma lipids, interferonγ, CRP, CD4(+)CD28(null) T cells, and perforin were increased and unstable atherosclerotic plaques developed in the rat model of AS. Blockade of the Kv1.3 potassium channel via PAP-1 administration decreased perforin levels and prevented plaque formation but had no effect on the other changes seen in this AS model. These findings suggest that the small molecule, voltage-gated potassium channel Kv1.3 blocker PAP-1 can suppress the development of AS in a rat model, most likely by inhibiting the exocytosis of cytoplasmic granules from CD4(+)CD28(null) T cells.

Heat shock proteins 60 and 70 specific proinflammatory and cytotoxic response of CD4+CD28null cells in chronic kidney disease

Background. CD4⁺CD28^null T cells are expanded in peripheral blood of patients with chronic kidney disease and associated with subclinical atherosclerosis. However, triggers for the oligoclonal expansion and activation of these cells are not clear. Methods. We investigated twenty-five stage V-IV chronic kidney disease (CKD) patients and eight healthy subjects (HC). Peripheral mononuclear cells were isolated and incubated with heat shock protein- (HSP) 60 and 70. CD4⁺CD28^null and CD4⁺CD28⁺ cells were sorted by flowcytometry and antigen specific response was assessed by the mRNA and protein expression of interferon (IFN)-γ, perforin, and granzyme B using qRT-PCR and Elispot. Results. The basal mRNA expression of IFN-γ, perforin, and granzyme B in CD4⁺CD28^null cells was higher in subjects with CKD compared to that in HC (P < 0.0001). Subjects with CKD also showed expression of IFN-γ, perforin, and granzyme B in the CD4⁺CD28⁺ subset, but this was much weaker than that seen in the CD4⁺CD28^null population (P < 0.0001). We did not note the expression of these molecules at mRNA or protein level in either subset of CD4 cells in HC. After incubation with HSP60 and HSP70, CD4⁺CD28^null cells showed increased expression at mRNA (P < 0.001) and protein level (P < 0.001). CD4⁺CD28⁺ cells also showed a weak increase in expression. No antigen-specific response was noted in HC. Conclusion. These data show that CD4⁺CD28^null cells in subjects with CKD react with HSP60 and HSP70 by upregulating the expression of IFN-γ, perforin and granzyme B. Increased circulating level of HSP60 and HSP70 might play a role in initiation and/or progression of atherosclerosis in CKD subjects through perturbation of CD4⁺CD28^null cells.

Dendritic cells in atherosclerosis

Atherosclerosis is a chronic inflammatory disease with activation of both the innate and adaptive arms of the immune system. Dendritic cells (DCs) are potent activators of adaptive immunity and have been identified in the normal arterial wall and within atherosclerotic lesions. Recent evidence points to a functional role for DCs in all stages of atherosclerosis because of their myriad functions including lipid uptake, antigen presentation, efferocytosis, and inflammation resolution. Moreover, DC-based vaccination strategies are currently being developed for the treatment of atherosclerosis. This review will focus on the current evidence as well as the proposed roles for DCs in the pathogenesis of atherosclerosis and discuss future therapeutic strategies.

Inflammation and immune system interactions in atherosclerosis

Cardiovascular disease (CVD) is the leading cause of mortality worldwide, accounting for 16.7 million deaths each year. The underlying cause of the majority of CVD is atherosclerosis. In the past, atherosclerosis was considered to be the result of passive lipid accumulation in the vessel wall. Today's picture is far more complex. Atherosclerosis is considered a chronic inflammatory disease that results in the formation of plaques in large and mid-sized arteries. Both cells of the innate and the adaptive immune system play a crucial role in its pathogenesis. By transforming immune cells into pro- and anti-inflammatory chemokine- and cytokine-producing units, and by guiding the interactions between the different immune cells, the immune system decisively influences the propensity of a given plaque to rupture and cause clinical symptoms like myocardial infarction and stroke. In this review, we give an overview on the newest insights in the role of different immune cells and subtypes in atherosclerosis.

Can we vaccinate against atherosclerosis?

A large body of evidence implicates the immune system in the pathogenesis of atherosclerosis. Both active and passive immunizations have been tested as immunomodulation strategies to confer protective effect against atherogenesis. This review focuses on the current knowledge of the complex role and the potential for immune modulation therapy via active immunization for atherosclerosis.

Expansion of the NKG2C+ natural killer-cell subset is associated with high-risk carotid atherosclerotic plaques in seropositive patients for human cytomegalovirus

OBJECTIVE

Human cytomegalovirus (HCMV), a pathogen involved in the development and progression of atherosclerosis, promotes in some individuals a marked reconfiguration of the natural killer (NK)-cell compartment whose hallmark is a persistent expansion of a peripheral blood NK-cell subset expressing the CD94/NKG2C NK receptor. We aimed to evaluate whether the HCMV-associated NK-cell compartment reconfiguration is related to carotid atherosclerotic plaque (CAP) instability.

APPROACH AND RESULTS

NK receptor expression (ie, LILRB1, NKG2A, NKG2C, and killer immunoglobulin-like receptors [KIR]) by peripheral NK and T cells was evaluated in 40 patients with HCMV+ with CAP, including nonatherosclerotic strokes (n=15) and healthy subjects (n=11) as controls. High-risk CAP (n=16), defined as carotid stenosis >50% with ipsilateral neurological symptomatology in the previous 180 days, compared with non-high-risk CAP had higher %NKG2C+ NK cells (29.5 ± 22.4% versus 16.3 ± 13.2%; P=0.026; odds ratio, 1.053; 95% confidence interval, 1.002-1.106; P=0.042), with a corresponding reduction in the NKG2A+ NK subset (31.7 ± 17.8% versus 41.8 ± 15.8%; P=0.072). The proportions of NKG2C+ NK cells in high-risk CAP were inversely correlated with the CD4+/CD8+ ratio (R(Spearman)=-0.629; P=0.009) and directly with high-sensitivity C-reactive protein levels (R(Pearson) = 0.591; P=0.012), consistent with higher subclinical systemic inflammation. The intraplaque inflammatory infiltrate, evaluated in 27 CAP obtained after endarterectomy, showed a higher presence of subintimal CD3+ lymphocytes in those patients with HCMV-induced changes in the peripheral NK- and T-cell compartments.

CONCLUSIONS

The expansion of NKG2C+ NK cells in patients with CAP seems to be associated with an increased risk of plaque destabilization in some patients with chronic HCMV infection.

T helper cell polarization in healthy people: implications for cardiovascular disease

Atherosclerosis is a chronic inflammatory disease characterized by T lymphocyte infiltration into the atherosclerotic plaque. Assessments of T cell subtypes have demonstrated a predominance of CD4(+) T helper (Th) cells, implicated Th1 and Th17 immunity in both human and mouse atherogenesis, and provided some evidence suggesting protective roles of Th2 and T regulatory cells. Observations that certain inbred mouse strains have an inherent T helper bias suggest a genetic predisposition toward developing a particular T helper phenotype. This review summarizes our current understanding of mechanisms of antigen processing for major histocompatibility complex molecules, describes the different T helper cell subsets and their roles in atherosclerosis, and discusses mechanisms of genetic predisposition toward Th1/Th2 bias in mice. We also present data from our laboratory demonstrating inherent Th1/Th2 phenotypes in apparently healthy human volunteers that are stable over time and discuss the potential implications for cardiovascular disease.

Immunological aspects of atherosclerosis

Cardiovascular disease is the leading cause of death in several countries. The underlying process is atherosclerosis, a slowly progressing chronic disorder that can lead to intravascular thrombosis. There is overwhelming evidence for the underlying importance of our immune system in atherosclerosis. Monocytes, which comprise part of the innate immune system, can be recruited to inflamed endothelium and this recruitment has been shown to be proportional to the extent of atherosclerotic disease. Monocytes undergo migration into the vasculature, they differentiate into macrophage phenotypes, which are highly phagocytic and can scavenge modified lipids, leading to foam cell formation and development of the lipid-rich atheroma core. This increased influx leads to a highly inflammatory environment and along with other immune cells can increase the risk in the development of the unstable atherosclerotic plaque phenotype. The present review provides an overview and description of the immunological aspect of innate and adaptive immune cell subsets in atherosclerosis, by defining their interaction with the vascular environment, modified lipids and other cellular exchanges. There is a particular focus on monocytes and macrophages, but shorter descriptions of dendritic cells, lymphocyte populations, neutrophils, mast cells and platelets are also included.

The role of the vascular dendritic cell network in atherosclerosis

A complex role has been described for dendritic cells (DCs) in the potentiation and control of vascular inflammation and atherosclerosis. Resident vascular DCs are found in the intima of atherosclerosis-prone vascular regions exposed to disturbed blood flow patterns. Several phenotypically and functionally distinct vascular DC subsets have been described. The functional heterogeneity of these cells and their contributions to vascular homeostasis, inflammation, and atherosclerosis are only recently beginning to emerge. Here, we review the available literature, characterizing the origin and function of known vascular DC subsets and their important role contributing to the balance of immune activation and immune tolerance governing vascular homeostasis under healthy conditions. We then discuss how homeostatic DC functions are disrupted during atherogenesis, leading to atherosclerosis. The effectiveness of DC-based "atherosclerosis vaccine" therapies in the treatment of atherosclerosis is also reviewed. We further provide suggestions for distinguishing DCs from macrophages and discuss important future directions for the field.

Analysis of the K+ current in human CD4+ T lymphocytes in hypercholesterolemic state

Atherosclerosis involves immune mechanisms: T lymphocytes are found in atherosclerotic plaques, suggesting their activation during atherogenesis. The predominant voltage-gated potassium channel of T cells, Kv1.3 is a key regulator of the Ca(2+)-dependent activation pathway. In the present experiments we studied the proliferation capacity and functional changes of Kv1.3 channels in T cells from healthy and hypercholestaeremic patients. By means of CFSE-assay (carboxyfluorescein succinimidyl ester) we showed that spontaneous activation rate of lymphocytes in hypercholesterolemia was elevated and the antiCD3/antiCD28 co-stimulation was less effective as compared to the healthy group. Using whole-cell patch-clamping we obtained that the activation and deactivation kinetics of Kv1.3 channels were faster in hypercholesterolemic state but no change in other parameters of Kv1.3 were found (inactivation kinetics, steady-state activation, expression level). We suppose that incorporation of oxLDL species via its raft-rupturing effect can modify proliferative rate of T cells as well as the gating of Kv1.3 channels.

Emerging role of chemokine receptor 7 in atherosclerosis

The CC chemokine receptor 7 (CCR7) and its ligands CCL19 and CCL21 essentially contribute to both immunity and tolerance by directing T cells and antigen-presenting dendritic cells (DCs) to and within lymph organs. In the pathogenesis of atherosclerosis, the accumulation of cholesterol in the subendothelial space of the vessel wall represents the initial step of plaque development in which DCs acquire and process low-density lipoprotein cholesterol as antigen in the vessel wall and then migrate to draining lymph nodes and present this antigen to naive T cells. Deletion of CCR7 receptor in murine atherosclerosis not only results in a reduced atherosclerotic plaque content but also leads to a disturbed entry and exit of T cells within the inflamed vessel wall. These observations are consistent with the notion that CCR7-dependent T cell priming in secondary lymphoid organs and CCR7-dependent recirculation of T cells between secondary lymphoid organs and inflamed tissue is pivotal for atherosclerotic plaque development and may represent an interesting target for innovative immune-modulatory therapy.

Regulatory T cells and Atherosclerosis

Atherosclerosis is a chronic autoimmune inflammatory disease. The involvement of both innate and adaptive immune responses in the pathogenesis of the disease has been well recognized. Tregs are an essential part of the immune system and have indispensable functions in maintaining immune system homeostasis, mediating peripheral tolerance, preventing autoimmune diseases, and suppressing inflammatory and proatherogenic immune response. Tregs carry out their immunosuppressive functions via several mechansims. One of the well-documented suppressive mechanisms of Tregs is the secretion of anti-inflammatory cytokines including IL-10, TGF-β, and IL-35. Studies have found that IL-10 and TGF-β have atheroprotective properties. In addition, Tregs can suppress the activity of proatherogenic effector T cells, suggesting an atheroprotective role. In fact, fewer Tregs are found in atherogenic ApoE-/- mice comparing to wild-type mice, suggesting an uncontrolled balance between weakened Tregs and effector T cells in atherogenesis. Some clinical studies of autoimmune diseases also suggest that decreased Tregs numbers are associated with increased disease activity. The importance of Tregs in many autoimmune diseases and experimental atherosclerosis has been established in in vivo and in vitro studies. However, the roles of Tregs in atherosclerosis in the clinical setting remains to be further characterized.

Neuroimmunology of the atherosclerotic plaque: a morphological approach

Atherosclerosis is a chronic inflammatory process, lasting for several decades until the onset of its clinical manifestations. The progression of the atherosclerotic lesion to a stable fibrotic plaque, narrowing the vascular lumen, or to a vulnerable plaque leading to main vascular complications, is associated to the involvement of several cell subpopulations of the innate as well as of the adaptive immunity, and to the release of chemokines and pro-inflammatory cytokines. Emerging evidence outlines that the cardiovascular risk is dependent on stress-mediators influencing cell migration and vascular remodeling. The view that atherosclerosis is initiated by monocytes and lymphocytes adhering to dysfunctional endothelial cells is substantiated by experimental and clinical observations. Macrophages, dendritic cells, T and B lymphocytes, granulocytes accumulating into the subendothelial space secrete and are stimulated by soluble factors, including peptides, proteases and cytokines acting synergistically. The final step of the disease, leading to plaque destabilization and rupture, is induced by the release, at the level of the fibrous cap, of metalloproteinases and elastases by the activated leukocytes which accumulate locally. Recruitment of specific cell subpopulations as well as the progression of atherosclerotic lesions towards a stable or an unstable phenotype, are related to the unbalance between pro-atherogenic and anti-atherogenic factors. In this connection stress hormones deserve particular attention, since their role in vascular remodeling, via vascular smooth cell proliferation, as well as in neoangiogenesis, via stimulation of endothelial cell proliferation and migration, has been already established.

OxLDL- and HSP-60 antigen-specific CD8(+) T lymphocytes are detectable in the peripheral blood of patients suffering from coronary artery disease

Inflammatory and immunologic mechanisms are important for the initiation and the progression of atherosclerotic lesions. OxLDL and HSP-60 antigens are involved in the pathogenesis of atherosclerotic disease by triggering immune cells within the plaques. Through the MHC pentamer assays, we investigated the presence of OxLDL- and HSP-60-specific CD8(+) T lymphocytes in twenty HLA-A2-positive patients suffering from coronary artery disease (10 NSTEMI and 10 stable angina). Similarly, 10 age- and sex-matched healthy subjects were enrolled as controls. Biological samples were collected within 6 h of admission to hospital, at 30 days and at 180 days. OxLDL- and HSP-60-specific CD8(+) T lymphocytes were never detectable in the peripheral blood from all the healthy controls. On the contrary, at each scheduled time point, both of these specific cells could be detected in peripheral blood from all enrolled patients. More in detail, the flow cytometric analysis of MHC-1 pentamer OxLDL-specific CD8(+) T lymphocytes revealed a sharp and significant increase at the hospital admission, within 6 h from the chest pain onset, followed by an evident decline to lower levels at 30 days and at 180 days from the enrollment in the study. On the contrary, although MHC-1 pentamer HSP-60 CD8(+) T lymphocytes were detectable in enrolled patients, almost no variance could be detectable during the follow-up scheduled evaluations. On the whole, this finding indicates that HSP-60- and OxLDL-specific CD8(+) T lymphocytes could play a role in the maintenance or worsening of the atherosclerotic coronary disease.

Control of dichotomic innate and adaptive immune responses by artery tertiary lymphoid organs in atherosclerosis

Tertiary lymphoid organs (TLOs) emerge in tissues in response to non-resolving inflammation such as chronic infection, graft rejection, and autoimmune disease. We identified artery TLOs (ATLOs) in the adventitia adjacent to atherosclerotic plaques of aged hyperlipidemic ApoE^−/− mice. ATLOs are structured into T cell areas harboring conventional dendritic cells and monocyte-derived DCs; B cell follicles containing follicular dendritic cells within activated germinal centers; and peripheral niches of plasma cells. ATLOs also show extensive neoangiogenesis, aberrant lymphangiogenesis, and high endothelial venule (HEV) neogenesis. Newly formed conduit networks connect the external lamina of the artery with HEVs in T cell areas. ATLOs recruit and generate lymphocyte subsets with opposing activities including activated CD4⁺ and CD8⁺ effector T cells, natural and induced CD4⁺ T regulatory (nTregs; iTregs) cells as well as B-1 and B-2 cells at different stages of differentiation. These data indicate that ATLOs organize dichotomic innate and adaptive immune responses in atherosclerosis. In this review we discuss the novel concept that dichotomic immune responses toward atherosclerosis-specific antigens are carried out by ATLOs in the adventitia of the arterial wall and that malfunction of the tolerogenic arm of ATLO immunity triggers transition from silent autoimmune reactivity to clinically overt disease.

Lymphocytes and the adventitial immune response in atherosclerosis

Although much of the research on atherosclerosis has focused on the intimal accumulation of lipids and inflammatory cells, there is an increasing amount of interest in the role of the adventitia in coordinating the immune response in atherosclerosis. In this review of the contributions of the adventitia and adventitial lymphocytes to the development of atherosclerosis, we discuss recent research on the formation and structural nature of adventitial immune aggregates, potential mechanisms of crosstalk between the intima, media, and adventitia, specific contributions of B lymphocytes and T lymphocytes, and the role of the vasa vasorum and surrounding perivascular adipose tissue. Furthermore, we highlight techniques for the imaging of lymphocytes in the vasculature.

Linking immunity to atherosclerosis: implications for vascular pharmacology--a tribute to Göran K. Hansson

For the past decade, we have deepened our understanding of the pathogenesis of atherosclerosis, a chronic arterial disease that causes cardiac and cerebral infarction and peripheral vascular disorders. Because of this extended understanding, more effective strategies for prevention and treatment of this disease are emerging. One of the fundamental mechanisms that lead to progress or regression in atherosclerosis, thus influencing its life-threatening complications, occurs through functional changes in vascular immunity and inflammation. This review briefly summarizes the discoveries in basic and translational sciences in this area and recent advances in clinical medicine against atherosclerotic vascular diseases.

Correlation of peripheral Th17 cells and Th17-associated cytokines to the severity of carotid artery plaque and its clinical implication

OBJECTIVE

Atherosclerosis is a chronic inflammatory disease regulated by T lymphocyte subsets. Th17 cells reportedly play important roles in the development of inflammatory and autoimmune diseases. In this study, we investigated the contributions of circulating Th17 cells and plasma Th17-associated cytokines to carotid artery plaques.

METHODS

Based on carotid artery ultrasonography, 280 atherosclerosis patients were categorized both by: (1) 4 levels for extent and severity of plaques (Level 1=least severe; Level 4=most severe) and (2) 5 groups for ultrasound features of carotid artery plaques (none, flat, soft, hard, ulcerated). Peripheral blood Th17 cell frequencies and plasma concentrations of Th17-associated cytokines (IL-17, IL-6, and TNF-α) were also determined.

RESULTS

For groups categorized by the extent and severity of carotid artery plaques, Th17 cell frequencies, common carotid artery intima-media thickness (CCA-IMT), and Crouse scores were significantly increased in higher level groups (Levels 3 and 4) than in lower level groups (Levels 1 and 2), and plasma concentrations of IL-17, IL-6, and TNF-α increased with increased levels of plaque severity. The same pattern was found for groups categorized by ultrasound features of carotid artery plaques. The results of Pearson correlation and multiple linear regression analyses showed that both CCA-IMT and Crouse scores for carotid artery plaques were significantly and positively correlated with Th17 cell frequencies and plasma Th17-associated cytokine concentrations.

CONCLUSION

These results suggest that increased frequencies of circulating Th17 cells and Th17-associated cytokines are correlated to the severity and progression of carotid artery plaques.

CCL17-expressing dendritic cells drive atherosclerosis by restraining regulatory T cell homeostasis in mice

Immune mechanisms are known to control the pathogenesis of atherosclerosis. However, the exact role of DCs, which are essential for priming of immune responses, remains elusive. We have shown here that the DC-derived chemokine CCL17 is present in advanced human and mouse atherosclerosis and that CCL17+ DCs accumulate in atherosclerotic lesions. In atherosclerosis-prone mice, Ccl17 deficiency entailed a reduction of atherosclerosis, which was dependent on Tregs. Expression of CCL17 by DCs limited the expansion of Tregs by restricting their maintenance and precipitated atherosclerosis in a mechanism conferred by T cells. Conversely, a blocking antibody specific for CCL17 expanded Tregs and reduced atheroprogression. Our data identify DC-derived CCL17 as a central regulator of Treg homeostasis, implicate DCs and their effector functions in atherogenesis, and suggest that CCL17 might be a target for vascular therapy.

Cellular immunity, low-density lipoprotein and atherosclerosis: break of tolerance in the artery wall

Atherosclerosis is a chronic inflammatory disease. Atherosclerotic plaques contain abundant immune cells that can dictate and effect inflammatory responses. Among them, T cells are present during all stages of the disease suggesting that they are essential in the initiation as well as the progression of plaque. Experimental as well as clinical research has demonstrated different T cell subsets, i.e. CD4+ Th1, Th2, Th17, and Treg as well as CD8+ and NKT cells in the plaque. Moreover, candidate antigens inducing T cell responses have been identified. Knowledge about the pathological role of these cells in atherogenesis may lead to development of new therapies. This review provides an overview of the research field of cellular immunity in atherosclerosis. It emphasises the events and findings involving antigen specific T cells, in particular low-density lipoprotein-specific T cells.

Current views on the functions of interleukin-17A-producing cells in atherosclerosis

Multiple components of the immune response are involved in the initiation, progression and persistence of atherosclerosis. Interleukin (IL)-17A is produced by a broad variety of leukocytes and plays an important role in host defense. IL-17A is also involved in the pathology of several autoimmune diseases mainly via the regulation of chemokine expression and leukocyte migration to the site of inflammation. There is an increasing body of evidence indicating an association between elevated levels of IL-17A and cardiovascular diseases. Interestingly, this IL-17A-dependent response occurs in parallel with the Th1-dominant immune response during atherogenesis. To date, the precise role of IL-17A+ cells in atherosclerosis is controversial. Several studies have suggested a pro-atherogenic role of IL-17A via the regulation of aortic macrophage numbers, Th1-related cytokines and aortic chemokine expression. However, two studies recently described anti-inflammatory effects of IL-17A on mouse plaque burden via possible regulation of aortic VCAM-1 expression and T cell content. Furthermore, an initial study using IL-17A-deficient mice demonstrated that IL-17A affects the immune composition and inflammatory phenotype of the aortic wall; however, no effects were observed on atherosclerosis. Further studies are necessary to fully address the role of IL-17A and other IL-17 family members in atherosclerosis.

Evidence for a role of regulatory T cells in mediating the atheroprotective effect of apolipoprotein B peptide vaccine

OBJECTIVES

Autoimmune responses against oxidized low-density lipoprotein are considered to play an important pro-inflammatory role in atherosclerosis and to promote disease progression. T-regulatory cells (Tregs) are immunosuppressive cells that have an important part in maintaining self-tolerance and protection against autoimmunity. We investigated whether aBp210, a prototype atherosclerosis vaccine based on a peptide sequence derived from apolipoprotein B, inhibits atherosclerosis through the activation of Tregs.

DESIGN

Six-week-old Apoe(-/-) mice were immunized with aBp210 and received booster immunizations 3 and 5 weeks later, as well as 1 week before being killed at 25 weeks of age.

RESULTS

At 12 weeks, immunized mice had increased expression of the Treg marker CD25 on circulating CD4 cells, and concanavalin A (Con A)-induced interferon-γ, interleukin (IL)-4, and IL-10 release from splenocytes was markedly depressed. At 25 weeks, there was a fivefold expansion of splenic CD4+ CD25+ Foxp3 Tregs, a 65% decrease in Con A-induced splenic T-cell proliferation and a 37% reduction in the development of atherosclerosis in immunized mice. Administration of blocking antibodies against CD25 neutralized aBp210-induced Treg activation as well as the reduction of atherosclerosis.

CONCLUSIONS

The present findings demonstrate that immunization of Apoe(-/-) mice with the apolipoprotein B peptide vaccine aBp210 is associated with activation of Tregs. Administration of antibodies against CD25 results in depletion of Tregs and blocking of the atheroprotective effect of the vaccine. Modulation in atherosclerosis-related autoimmunity by antigen-specific activation of Tregs represents a novel approach for treatment of atherosclerosis.

The immune system in atherosclerosis

Cardiovascular disease, a leading cause of mortality worldwide, is caused mainly by atherosclerosis, a chronic inflammatory disease of blood vessels. Lesions of atherosclerosis contain macrophages, T cells and other cells of the immune response, together with cholesterol that infiltrates from the blood. Targeted deletion of genes encoding costimulatory factors and proinflammatory cytokines results in less disease in mouse models, whereas interference with regulatory immunity accelerates it. Innate as well as adaptive immune responses have been identified in atherosclerosis, with components of cholesterol-carrying low-density lipoprotein triggering inflammation, T cell activation and antibody production during the course of disease. Studies are now under way to develop new therapies based on these concepts of the involvement of the immune system in atherosclerosis.

Invariant natural killer T cells: linking inflammation and neovascularization in human atherosclerosis

Atherosclerosis, a chronic inflammatory lipid storage disease of large arteries, is complicated by cardiovascular events usually precipitated by plaque rupture or erosion. Inflammation participates in lesion progression and plaque rupture. Identification of leukocyte populations involved in plaque destabilization is important for effective prevention of cardiovascular events. This study investigates CD1d-expressing cells and invariant NKT cells (iNKT) in human arterial tissue, their correlation with disease severity and symptoms, and potential mechanisms for their involvement in plaque formation and/or destabilization. CD1d-expressing cells were present in advanced plaques in patients who suffered from cardiovascular events in the past and were most abundant in plaques with ectopic neovascularization. Confocal microscopy detected iNKT cells in plaques, and plaque-derived iNKT cell lines promptly produced proinflammatory cytokines when stimulated by CD1d-expressing APC-presenting α-galactosylceramide lipid antigen. Furthermore, iNKT cells were diminished in the circulating blood of patients with symptomatic atherosclerosis. Activated iNKT cell-derived culture supernatants showed angiogenic activity in a human microvascular endothelial cell line HMEC-1-spheroid model of in vitro angiogenesis and strongly activated human microvascular endothelial cell line HMEC-1 migration. This functional activity was ascribed to IL-8 released by iNKT cells upon lipid recognition. These findings introduce iNKT cells as novel cellular candidates promoting plaque neovascularization and destabilization in human atherosclerosis.

Chemokine receptor 7 knockout attenuates atherosclerotic plaque development

BACKGROUND

Atherosclerosis is a systemic inflammatory disease characterized by the formation of atherosclerotic plaques. Both innate immunity and adaptive immunity contribute to atherogenesis, but the mode of interaction is poorly understood. Chemokine receptor 7 (CCR7) is critically involved in the transition from innate to adaptive immune activation by coordinating the migration to and positioning of antigen-presenting dendritic cells and T cells in secondary lymphoid organs. More recently, it was shown that CCR7 is also responsible for T-cell migration into inflamed tissues and T-cell egress from these tissues via the afferent lymph. Thus, we investigated the influence of a systemic CCR7 deficiency on atherogenesis in atherosclerosis-prone low-density lipoprotein receptor (ldlr) knockout mice.

METHODS AND RESULTS

CCR7 deficiency resulted in reduced atherosclerotic plaque development. CCR7(-/-) T cells showed impaired entry and exit behavior from atherosclerotic lesions. Oxidized low-density lipoprotein, a key molecule for atherogenesis with antigenic features, was used to pulse dendritic cells and to expand T cells ex vivo. Adoptive transfer of C57BL/6 wild-type T cells but not ccr7(-/-)-derived T cells primed with oxidized low-density lipoprotein-pulsed dendritic cells resulted in a reconstitution of atherogenesis in ccr7(-/-)/ldlr(-/-) mice.

CONCLUSION

These results demonstrate that both CCR7-dependent T-cell priming in secondary lymphoid organs and CCR7-dependent recirculation of T cells between secondary lymphoid organs and inflamed tissue are crucially involved in atherosclerotic plaque development.

Inhibition of T cell response to native low-density lipoprotein reduces atherosclerosis

Immune responses to oxidized low-density lipoprotein (oxLDL) are proposed to be important in atherosclerosis. To identify the mechanisms of recognition that govern T cell responses to LDL particles, we generated T cell hybridomas from human ApoB100 transgenic (huB100(tg)) mice that were immunized with human oxLDL. Surprisingly, none of the hybridomas responded to oxidized LDL, only to native LDL and the purified LDL apolipoprotein ApoB100. However, sera from immunized mice contained IgG antibodies to oxLDL, suggesting that T cell responses to native ApoB100 help B cells making antibodies to oxLDL. ApoB100 responding CD4(+) T cell hybridomas were MHC class II-restricted and expressed a single T cell receptor (TCR) variable (V) beta chain, TRBV31, with different Valpha chains. Immunization of huB100(tg)xLdlr(-/-) mice with a TRBV31-derived peptide induced anti-TRBV31 antibodies that blocked T cell recognition of ApoB100. This treatment significantly reduced atherosclerosis by 65%, with a concomitant reduction of macrophage infiltration and MHC class II expression in lesions. In conclusion, CD4(+) T cells recognize epitopes on native ApoB100 protein, this response is associated with a limited set of clonotypic TCRs, and blocking TCR-dependent antigen recognition by these T cells protects against atherosclerosis.

Inflammatory and autoimmune reactions in atherosclerosis and vaccine design informatics

Atherosclerosis is the leading pathological contributor to cardiovascular morbidity and mortality worldwide. As its complex pathogenesis has been gradually unwoven, the regime of treatments and therapies has increased with still much ground to cover. Active research in the past decade has attempted to develop antiatherosclerosis vaccines with some positive results. Nevertheless, it remains to develop a vaccine against atherosclerosis with high affinity, specificity, efficiency, and minimal undesirable pathology. In this review, we explore vaccine development against atherosclerosis by interpolating a number of novel findings in the fields of vascular biology, immunology, and bioinformatics. With recent technological breakthroughs, vaccine development affords precision in specifying the nature of the desired immune response—useful when addressing a disease as complex as atherosclerosis with a manifold of inflammatory and autoimmune components. Moreover, our exploration of available bioinformatic tools for epitope-based vaccine design provides a method to avoid expenditure of excess time or resources.

Downregulation of T helper cell type 3 in patients with acute coronary syndrome

BACKGROUND AND AIMS

There is an imbalance between Th1 and Th2 in the development and progression of atherosclerosis and in patients with acute coronary syndrome (ACS) including acute myocardial infarction (AMI) and unstable angina. T helper cell type 3 (Th3), which primarily secretes transforming growth factor beta-1 (TGF-beta1), has been shown to inhibit both Th1 and Th2 cells. The present study was designed to investigate whether Th3 cells are involved in plaque destabilization and the onset of ACS.

METHODS

Ninety one patients who underwent diagnostic catheterization were classified into four groups (AMI group, unstable angina group, stable angina group and chest pain syndrome group). The cell frequencies of Th1, Th2 and Th3 were detected using flow cytometry, and the concentrations of their related cytokines IFN-gamma, IL-4 and TGF-beta1 were studied by ELISA.

RESULTS

Apart from the imbalance between Th1 and Th2, results revealed a significant decrease in peripheral Th3 number and levels of TGF-beta1 in patients with ACS as compared with those in patients with stable angina and chest pain syndrome (p<0.01).

CONCLUSIONS

Downregulation of Th3 cells in patients with ACS may play a potential role in plaque destabilization and the onset of ACS.

Vaccines modulating lipoprotein autoimmunity as a possible future therapy for cardiovascular disease

Current strategies for prevention of cardiovascular disease focus on risk factor intervention. Although these have been proven both safe and effective results from randomized clinical trials suggest that it is difficult to achieve relative risk reductions exceeding 40% with this approach. To further improve efficacy future therapies must aim at targeting the actual disease process in the arterial wall. Emerging evidence have identified an important role of the immune system in atherosclerosis and suggest that modulation of autoimmune responses against oxidized LDL and other antigens in the atherosclerotic plaque represent one possible new approach to disease prevention. Oxidized LDL is targeted by both antibody-mediated and cellular immune responses and as much as 10% of the T cells in atherosclerotic plaques are oxidized LDL-specific. Immune activation in the atherosclerotic plaque is primarily of the pro-inflammatory Th1-type and inhibition Th1 immunity reduces atherosclerosis in experimental animals. Atherosclerosis vaccines based on antigens derived from LDL have been developed to modulate these processes. Their mechanisms of action remain to be full characterized but may involve expression of protective antibodies that facilitate the removal of oxidized LDL and antigen-specific regulatory T cells that counteract Th1 autoimmunity against oxidized LDL. In this review we will discuss the possibilities and challenges encountering the translation of immune-modulatory therapy for atherosclerosis from the experimental stage into the clinic.

Adaptive immunity and atherosclerosis

Atherosclerosis involves the formation of inflammatory arterial lesions and is one of the most common causes of death globally. It has been evident for more than 20 years that adaptive immunity and T cells in particular regulate the magnitude of the atherogenic pro-inflammatory response. T cells also influence the stability of the atherosclerotic lesion and thus the propensity for thrombus formation and the clinical outcome of disease. This review summarizes our current understanding of T cells in atherogenesis, including which antigens they recognize, the role of T cell costimulation/coinhibition, and their secretion of pro- and anti-inflammatory mediators. Furthermore, we outline future areas of research and potential clinical intervention strategies.

Adhesion of T and B lymphocytes to mouse atherosclerotic aortas: Association with lesion topology and VCAM‐1 expression

OBJECTIVE

Although T and B lymphocytes accumulate in atherosclerotic lesions and play a key role in their growth, the mechanisms involved in the adhesion and recruitment of T and B lymphocytes by the lesions have not been resolved. The aim of this study was to compare T and B lymphocyte adhesion to atherosclerotic arteries and to test the role of VCAM-1 and ICAM-1.

MATERIAL AND METHODS

T and B lymphocytes were labelled with red and green fluorescent dyes and incubated with freshly isolated aortas from apolipoprotein-E-deficient mice. In some experiments the aortas were pre-incubated with specific monoclonal antibodies. After washing, the adhering cells were detected by confocal laser scanning microscopy.

RESULTS

The number of T and B lymphocytes that adhered to the aortic intimal surface was similar in both lesioned and non-lesioned areas and in the shoulder region of the lesions. However, the adhesion of T and B lymphocytes was significantly higher in the shoulder regions compared with the lesioned (p<0.0001) and non-lesioned areas of the aorta (p<0.0001). After pre-incubation of the aortas with antibodies against VCAM-1 or ICAM-1, the lymphocyte adhesions in lesioned areas were 42 % (p = 0.04) and 55 % (p = 0.17), respectively, of those in lesioned areas that had been pre-incubated with a control antibody. However, although VCAM-1 protein expression was most pronounced in the shoulder region, the lymphocyte adhesions in the shoulder region and in non-lesioned areas were unaffected by pre-incubation with VCAM-1 antibodies.

CONCLUSIONS

The results suggest that adhesion of T and B lymphocytes to mouse aortic endothelium is similar, is affected by lesion topology and is dependent on VCAM-1 expression over the core of atherosclerotic lesions.

Immune and inflammatory mechanisms of atherosclerosis (*)

Atherosclerosis is an inflammatory disease of the wall of large- and medium-sized arteries that is precipitated by elevated levels of low-density lipoprotein (LDL) cholesterol in the blood. Although dendritic cells (DCs) and lymphocytes are found in the adventitia of normal arteries, their number is greatly expanded and their distribution changed in human and mouse atherosclerotic arteries. Macrophages, DCs, foam cells, lymphocytes, and other inflammatory cells are found in the intimal atherosclerotic lesions. Beneath these lesions, adventitial leukocytes organize in clusters that resemble tertiary lymphoid tissues. Experimental interventions can reduce the number of available blood monocytes, from which macrophages and most DCs and foam cells are derived, and reduce atherosclerotic lesion burden without altering blood lipids. Under proatherogenic conditions, nitric oxide production from endothelial cells is reduced and the burden of reactive oxygen species (ROS) and advanced glycation end products (AGE) is increased. Incapacitating ROS-generating NADPH oxidase or the receptor for AGE (RAGE) has beneficial effects. Targeting inflammatory adhesion molecules also reduces atherosclerosis. Conversely, removing or blocking IL-10 or TGF-beta accelerates atherosclerosis. Regulatory T cells and B1 cells secreting natural antibodies are atheroprotective. This review summarizes our current understanding of inflammatory and immune mechanisms in atherosclerosis.

Vaccination against atherosclerosis? Induction of atheroprotective immunity

Atherosclerosis involves the formation of inflammatory arterial lesions and is one of the most common causes of death globally. It has been evident for more than 20 years that adaptive immunity regulates the magnitude of the atherogenic proinflammatory response. T cells may also influence the stability of the atherosclerotic lesion and thus the propensity for thrombus formation and the clinical outcome of disease. Immunization of hypercholesterolemic animals with low-density lipoprotein preparations reduces atherosclerosis, suggesting that vaccination may represent a useful strategy for disease prevention or modulation. This review summarizes our current understanding of the role immunity in atherosclerosis and outlines strategies for antigen-specific prevention of this disease.

Innate and adaptive immunity in atherosclerosis

Atherosclerosis, a chronic inflammatory disorder, involves both the innate and adaptive arms of the immune response that mediate the initiation, progression, and ultimate thrombotic complications of atherosclerosis. Most fatal thromboses, which may manifest as acute myocardial infarction or ischemic stroke, result from frank rupture or superficial erosion of the fibrous cap overlying the atheroma, processes that occur in inflammatorily active, rupture-prone plaques. Appreciation of the inflammatory character of atherosclerosis has led to the application of C-reactive protein as a biomarker of cardiovascular risk and the characterization of the anti-inflammatory and immunomodulatory actions of the statin class of drugs. An improved understanding of the pathobiology of atherosclerosis and further studies of its immune mechanisms provide avenues for the development of future strategies directed toward better risk stratification of patients as well as the identification of novel anti-inflammatory therapies. This review retraces leukocyte subsets involved in innate and adaptive immunity and their contributions to atherogenesis.

CD4+ CD28 null T cells in coronary artery disease: when helpers become killers

The crucial role of T cells in atherosclerosis and coronary artery disease (CAD) has been highlighted by recent observations. Helper CD4(+) T cells can both aggravate or attenuate the atherogenic process and the development of CAD. CD4(+)CD28(null) T cells are an unusual subset of helper cells which expand and have deleterious effects in CAD. In this review, we discuss the current issues on the generation of CD4(+)CD28(null) T cells and focus on their phenotypic and functional characteristics relevant to the development of cardiovascular events. The possible effects of the present day therapies for CAD on the CD4(+)CD28(null) T cells are also explored. Targeting the CD4(+)CD28(null) T cell subset in CAD could provide novel therapeutic strategies to prevent acute life-threatening coronary events.

Pervasive and stochastic changes in the TCR repertoire of regulatory T-cell-deficient mice

We hypothesize that regulatory T-cell (Treg)-deficient strains have an altered TCR repertoire in part due to the expansion of autoimmune repertoire by self-antigen. We compared the Vbeta family expression profile between B6 and Treg-lacking B6.Cg-Foxp3(sf)(/Y) (B6.sf) mice using fluorescent anti-Vbeta mAbs and observed no changes. However, while the spectratypes of 20 Vbeta families among B6 mice were highly similar, the Vbeta family spectratypes of B6.sf mice were remarkably different from B6 mice and from each other. Significant spectratype changes in many Vbeta families were also observed in Treg-deficient IL-2 knockout (KO) and IL-2Ralpha KO mice. Such changes were not observed with anti-CD3 mAb-treated B6 mice or B6 CD4+CD25- T cells. TCR transgenic (OT-II.sf) mice displayed dramatic reduction of clonotypic TCR with concomitant increase in T cells bearing non-transgenic Vbeta and Valpha families, including T cells with dual receptors expressing reduced levels of transgenic Valpha and endogenous Valpha. Collectively, the data demonstrate that Treg deficiency allows polyclonal expansion of T cells in a stochastic manner, resulting in widespread changes in the TCR repertoire.

CX3CR1 deficiency impairs dendritic cell accumulation in arterial intima and reduces atherosclerotic burden

OBJECTIVE

Dendritic cells (DCs) have recently been found in atherosclerosis-predisposed regions of arteries and have been proposed to be causal in atherosclerosis. The chemokine receptor CX3CR1 is associated with arterial injury and atherosclerosis. We sought to determine whether a link exists between arterial DC accumulation, CX3CR1, and atherosclerosis.

METHODS AND RESULTS

Mouse aortas were isolated and subjected to en face immunofluorescence analysis. We found that DCs were located predominantly in the intimal regions of arterial branch points and curvatures. Consistent with the increased accumulation of intimal DCs in aged and ApoE-/- aortas compared with young WT aortas (P=0.004 and 0.05, respectively), the incidence of atherosclerosis was 88.9% for aged WT and 100% for ApoE-/- mice compared with 0% for young WT mice. CX3CR1 was expressed on intimal DCs and DC numbers were decreased in CX3CR1-deficient aortas of young, aged, and ApoE-/- mice (P=0.0008, 0.013, and 0.0099). The reduced DC accumulation in CX3CR1-deficiency was also correlated with decreased atherosclerosis in these animals.

CONCLUSIONS

The accumulation of intimal DC increases in aged and ApoE-/- aortas and correlates with the generation of atherosclerosis. CX3CR1-deficiency impairs the accumulation of DC in the aortic wall and markedly reduces the atherosclerotic burden.