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Gran K. Hansson

Immune Mechanisms in Atherosclerosis

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Immune Mechanisms in Atherosclerosis

Gran K. Hansson

AbstractAtherosclerosis is an inflammatory disease. Its lesions are filled with immune cells that can orchestrate andeffect inflammatory responses. In fact, the first lesions of atherosclerosis consist of macrophages and T cells. Unstableplaques are particularly rich in activated immune cells, suggesting that they may initiate plaque activation. We have seena rapid increase in the understanding of the mechanisms that govern the recruitment, differentiation, and activation ofimmune cells in atherosclerosis. Experimental research has identified several candidate antigens, and there areencouraging data suggesting that immune modulation as well as immunization can reduce the progression of the disease.This review provides an overview of our current understanding of the role of immune mechanisms in atherosclerosis.(Arterioscler Thromb Vasc Biol. 2001;21:1876-1890.)

Key Words:atherosclerosis pathophysiology cell biology cytokines

The atherosclerotic lesion contains large numbers of im-

mune cells, particularly macrophages and T cells. Fur-thermore, the disease is associated with systemic immuneresponses and signs of inflammation. Histopathological andclinical investigations point to inflammatory/immune activa-tion of plaques as a cause of acute coronary syndromes, andseroepidemiological studies have suggested links betweenatherosclerosis and microbial infections. During recent years,experiments in gene-targeted mice have provided mechanisticevidence in support of the hypothesis that immune mecha-nisms are involved in atherosclerosis. This review willprovide an update on immune mechanisms in atherosclerosis,with particular focus on mechanistic studies.

Immune Cells in the Lesions of AtherosclerosisAdaptive (ie, antigen-specific) immune reactions are initiatedwhen a macrophage (or a dendritic cell of the macrophagelineage) displays a surface complex consisting of an antigenicpeptide bound to a major histocompatibility complex (MHC)protein to a neighbor T cell. This can elicit T-cell activation,cytokine secretion, cytotoxicity, antibody production, andmany other components of an immune reaction. There is nowgood evidence that atherosclerosis is associated with immunereactions and that antigen presentation occurs in atheroscle-rotic lesions. The cellular composition of an atheroma isillustrated in Figure 1. It has been known for many years that

monocyte-derived macrophages are present in large numbersin atherosclerotic lesions.17 The discovery of the scavengerreceptor pathway for uptake of modified lipoproteins810

provided an explanation for the finding that most foam cellsbear macrophage differentiation markers.

The other main immune cell of atherosclerotic lesions, theT cell, remained undetected for a long time. It was observed

that many vascular smooth muscle cells (SMCs) in human

lesions express human leukocyte antigen (HLA)-DR, a cellsurface protein that is induced by the T-cell cytokineinterferon- (IFN-).11 By using T-cellspecific CD3 anti-bodies, it could be established that T cells are abundant inhuman plaques.12 A large proportion of them are in anactivated state1316; ie, they express adhesion molecules andother surface molecules, secrete cytokines, and may prolifer-ate. The activation of T cells and macrophages leads to acascade of cytokines that induce an inflammatory state. Withthe cDNA cloning and production of recombinant cytokines,it became possible to study their effects in the context ofvascular biology. Such studies revealed that vascular endo-

thelial cells and SMCs are important targets for inflammatorycytokines and that they are capable of producing significantamounts of cytokines themselves on stimulation.17,18

Studies during the last decade have identified other types ofimmune cells in atherosclerotic plaques. Among them, dendriticcells are professional antigen-presenting cells that may beparticularly important in the initiation of immune responses toplaque antigens.19 Mast cells are immune effector cells with acapacity to modify lipoproteins and digest matrix components;they could be important in plaque activation and rupture.20 Allthese different cells may be involved in the initiation, progres-sion, and/or development of complications to atherosclerosis. Atpresent, there is evidence for pathogenic roles of monocyte-

derived macrophages and T cells.

Recruitment of Immune Cells to the Vessel Wall

Leukocyte Adhesion to the EndotheliumDuring the initiation of atherosclerosis, mononuclear leuko-cytes, ie, monocytes and T cells, are recruited to the vesselwall across an intact endothelium. This requires activation of

Received May 21, 2001; revision accepted October 2, 2001.From the Center for Molecular Medicine and the Department of Medicine at Karolinska Hospital, Karolinska Institute, Stockholm, Sweden.Correspondence to Gran K. Hansson, Center for Molecular Medicine and Department of Medicine, Karolinska Hospital, Karolinska Institute,

SE-17176, Stockholm, Sweden. E-mail [email protected]

2001 American Heart Association, Inc.Arterioscler Thromb Vasc Biol.is available at http://www.atvbaha.org

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Brief Reviews

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the endothelium to express leukocyte adhesion molecules.

These cell surface proteins are mainly regulated transcription-

ally in a process that involves nuclear factor (NF)-B,21 a

transcription factor that is transactivated when proinflamma-

tory cytokines ligate their receptors on the endothelial sur-

face. Both E-selectin and 2 imunoglobulin-like adhesionmolecules, intercellular adhesion molecule-1 (ICAM-1) and

vascular cell adhesion molecule-1 (VCAM-1), can be induced

in this way.

VCAM-1 can be induced not only on cytokine stimulation

but also in response to other proinflammatory macromole-

cules. Lipopolysaccharides of Gram-negative bacteria acti-

vate NF-B by ligating toll-like receptors (TLRs), which

transduce NF-B activation through a kinase cascade similar

to the one initiated by interleukin-1 (IL-1). In addition,

lysophosphatidylcholine and other oxidized phospholipids

can induce VCAM-1 expression in endothelial cells.22,23

Interestingly, such phospholipid species are generated during

lipoprotein oxidation. Their activity may explain the in-creased adhesive properties of endothelial cells exposed to

oxidized LDL (oxLDL)24 (Figure 2). In vivo studies have

shown that hypercholesterolemia rapidly leads not only to

lipoprotein deposition and oxidation in the intima but also to

VCAM-1 expression on the luminal aortic endothelium.25,26

This provides a direct link between hypercholesterolemia and

inflammatory activation of the vessel wall.

ICAM-1 is induced in endothelial cells through a cytokine-

dependent pathway, but its expression is also promoted by

hemodynamic stress. The latter seems to be due to activation

of the shear stress response element in its promoter.27 This

probably explains the finding of ICAM-1 expression in aortic

regions where the endothelium is exposed to variations in

shear stress caused by blood flow.2729 It is likely that the

disturbed flow encountered during hypertension can increase

ICAM-1 expression. Thus, both hypercholesterolemia andhypertension, 2 major risk factors for atherosclerosis, in-

crease the recruitment of leukocytes to the artery.

Adhesion is a multistep process that starts with leukocyte

rolling on the endothelial surface. This is due to selectin

ligation, whereas the subsequent firm adhesion depends on

interactions between immunoglobulin-like molecules

(VCAM-1, ICAM-1, and others) on the endothelium and

integrins on the leukocyte surface.30 Very lateactivationantigen-4 (VLA-4), a major counterreceptor for VCAM-1, is

expressed by monocytes and lymphocytes but not by granu-

locytes.31 This explains the selective recruitment of mononu-

clear cells to the arterial intima during early atherosclerosis.32

Immunopharmacological blockade of ICAM-1 and VCAM-1has been shown to inhibit fatty streak development33 (Table

1). The importance of selectin interactions is illustrated by the

finding that mice deficient in E-selectin and P-selectin de-

Figure 1. Immune cells in atheroma. Macrophages (MPh) and Tcells are common components of lesions, which may also con-tain mast cells and occasional B cells. T cells are activated bylocal antigens presented by antigen-presenting macrophagesand dendritic cells. Activation leads to production of interferon-(IFNg), which not only primes macrophages for activation but

also regulates smooth muscle and endothelial functions. Acti-vated macrophages produce proinflammatory cytokines such astumor necrosis factor- (TNFa) and IL-1, which can induce pro-coagulant (Coag), fibrinolytic (fibr.), and adhesive properties onendothelial cells (EC). Macrophages also make matrix metallo-proteinases (MMP), and both T cells and macrophages producecytotoxic factors, which contribute to apoptosis. See text forexplanation of other abbreviations.

TABLE 1. Animal Studies Demonstrating Important Roles for Leukocyte Adhesion and Migration

in Atherosclerosis

Molecule Function Experiment Atherosclerosis Model Result Reference No.

P-, E-selectin Rolling (PMN, MC, Ly) KO ApoE-KO 2 Fatty streaks 34

P-selectin Rolling (PMN, MC, Ly) KO ApoE-KO 2 Atheroma 35

VCAM-1 Firm adhesion (MC, Ly) Ab Rabbit 2 Postinjury lesion 213

MCP-1 Chemoattractant (MC, Ly) KO LDLR-KO, apoE-KO, apoB-Tg 2 Atheroma 44, 46

CCR-2 MCP-1 rec (MC, Ly) KO LDLR, apoE-KO 2 Atheroma 45

CCR-2 indicates C-C chemokine receptor-2; PMN, polymorphonuclear leukocytes; MC, monocytes; Ly, lymphocytes; rec, receptor;

and Tg, transgenic. See text for explanation of other abbreviations.

Figure 2. Hypercholesterolemia leads to recruitment of immunecells to the vessel wall. LDL accumulates in the arterial intima.Lipid products of LDL oxidation induce VCAM-1 in endothelialcells. Monocytes and T cells adhere through their VLA-4 recep-tors. Their subsequent migration through the endothelial layer isstimulated by chemokines such as MCP-1 and also by comple-ment activation products (Cpt), which can be generated by oxi-dized cholesterol aggregates. See text for explanation of otherabbreviations.

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addition, IFN- induces expression of secretory phospho-lipase A2, which can lead to production of inflammatory lipid

mediators such as eicosanoids, lysophosphatidylcholine, and

PAF.71

In vivo studies in rats have shown that the proliferative

response of SMCs after arterial injury is inhibited by IFN-,72

which also inhibits smooth muscle contractility and collagen

synthesis.70,73 It was therefore proposed that IFN-produc-ing T cells could play an important role in plaque destabili-

zation by reducing the fibrous cap.74,75 Histopathological

findings of activated T cells at sites of rupture in culprit

lesions support this notion.76

Further support for a proatherogenic role came from

studies of compound KO mice lacking the IFN-receptor as

well as apoE. These mice had an 60% reduction in

atherosclerosis, supporting the notion that IFN-is a strongly

proatherogenic cytokine77 (Table 4). The lack of IFN-

signaling affected the lipoprotein profile (reduced apoA-IV)

as well as the vessel wall (increased collagen), implying that

both systemic and local effects could be important for the

antiatherogenic action. However, IFN-was recently shownto aggravate transplant vasculopathy by its local action on the

vessel wall.78 Even in severe combined-immunodeficient

(SCID) mice, IFN- induced vascular pathology in xeno-

grafts, indicating that its direct vascular actions are sufficient

to promote disease. Finally, recent experiments have shown

that administration of this cytokine accelerates atherosclero-

sis in apoE-KO mice.79 All these data imply that IFN- is a

proatherogenic cytokine.

Proinflammatory Cytokines: Mediators of Innate andTh1 ResponsesTNF- and IL-1 are also present in human lesions.16,80,81

Similarly to IFN-, they affect smooth muscle proliferation,but their effects are more complex and indirect. IL-1 not only

stimulates SMC replication by inducing an autocrine plate-

let-derived growth factor loop but also inhibits proliferation

by inducing the growth-inhibitory autacoid, prostaglandin

E1.82,83 The net effect on SMC growth therefore depends on

the precise conditions in experimental systems and remains

TABLE 2. Some Immune Cytokine-Regulated Genes of Importance in Atherosclerosis

Gene Product Cytokine Cytokine Producers Target Cells Effect Reference No.

VCAM-1 IL-1, TNF-, IL-4 M, Th2, SMC, EC EC, SMC Adhesion 214

ICAM-1 IL-1, TNF-, IFN- M, Th1, SMC, EC EC Adhesion 215

CD36 IL-4 Th2 M OxLDL uptake 216

SR-A IFN-, TNF-, IL-6 Th1, M, SMC M 2 OxLDL uptake 4850

NOS2 IFN-, TNF-, IL-1 Th1, M, SMC, EC M, SMC, EC 1 NO 217, 218

NOS2 IL-4 Th2 M, SMC, EC 2 NO 101

COX2 IFN-, TNF-, IL-1 M, Th1, SMC, EC M, SMC, EC 1 Eicosanoids 219

COX2 IL-4 Th2 M, SMC, EC 2 Eicosanoids 103

15-LO IL-4, IL-13 Th2 M, SMC Oxidation, leukotrienes 220, 221

IL-1, TNF- IFN- Th1 M Activ 222

IL-6 IL-1 M, EC, SMC SMC B-cell activ, PTX prod 92

MMPs TNF-, IL-1, CD40L* M M, SMC, EC Proteolysis 84, 201, 223, 224

MMPs IFN- Th1 M, SMC, EC 2 Proteolysis 84, 201

tPA, uPA TNF-, IL-1 M, EC, SMC EC 1 Fibrinolysis 225

uPA IFN- Th1 EC 2 Fibrinolysis 226

PAI-1, -2 IFN-, TNF-, IL-1 M, Th1 EC Antifibrinolysis 227

PPAR-dep genes IL-4 Th2 M 1 CD36 expression 228

ApoA-IV IFN- Th1 Hepatocytes 2 HDL 77

ABCA1 IFN- Th1 M foam cells 2 Cholesterol efflux 229

sPLA2 IFN- Th1 SMC 1 Eicosanoids, PAF, lysoPC 71

LPL IFN-, TNF-, IL-1 M, Th1 M 2 Lipolysis 86, 87

NOS indicates nitric oxide synthase; COX, cyclooxygenase; LO, lipoxygenase; MMPs, matrix metalloproteinases; tPA, tissue

plasminogen activator; uPA, urokinase-type plasminogen activator; PAI, plasminogen activator inhibitor; PPAR, peroxisome

proliferatoractivated receptor; dep, dependent; LPL, lipoprotein lipase; M, macrophage; EC, endothelial cell; activ, activation; PTX,

pentraxin; prod, products; and lysoPC, lysophosphatidylcholine. See text for explanation of other abbreviations.

*The cell surface molecule CD40L (CD154) has effects similar to those of a soluble cytokine.

TABLE 3. T-Cell Types Potentially Involved in Atherosclerosis

Cell Type

Antigen

Rec Epitope Restriction Element

Present in

Lesions

Effect Shown in

Exp Model

CD4 TCR Peptide MHC class II Yes Yes

CD8 TCR Peptide MHC class I Yes Yes

T TCR Lipid CD1 Yes No

rec indicates receptor; exp, experimental. See text for explanation of other abbreviations.




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controversial in the in vivo situation. TNF- and IL-1 are

powerful inducers of local inflammation in blood vessels and

elsewhere (Table 2). For instance, they stimulate further

activation of macrophages, induce secretion of matrix

metalloproteinase-9,84 and promote expression of leukocyte

adhesion molecules (see above). IL-1 is also an important

costimulatory factor for T-cell activation and TNF-, a

proapoptotic cytokine.

The metabolic effects of IL-1 and TNF- are even more

striking than those of IFN- (Table 2). They are powerful

inhibitors of lipoprotein lipase, which leads to increased

systemic levels of VLDL and hypertriglyceridemia.85,86 In

addition, they exert important effects on glucose and energymetabolism. High-dose stimulation with TNF- therefore

results in cachexia. It is possible that much lower TNF-

levels lead to metabolic changes of the kind observed in the

metabolic syndrome, such as hypertriglyceridemia, redistri-

bution of adipose tissue, and reduced insulin sensitivity.8789

Interestingly, this syndrome is considered an important risk

factor for atherosclerotic cardiovascular disease.

The proinflammatory cytokine pathway is a cascade that

involves activation by TNF- and IL-1 to IL-6 expression90

and also to secretion of pentraxins such as C-reactive protein

(CRP).91 This cascade is amplified in each step. For instance,

IFN- produced by Th1 cells stimulates macrophages to

secrete IL-1. The latter cytokine stimulates SMCs to make

copious amounts of IL-6,92 a mediator that is present in

atherosclerotic lesions64,93 and that may also be induced by

the terminal complement complex C5b-994 (Table 2). CRP

and other pentraxins may not only be markers of inflamma-tion but also exert direct effects on leukocyte recruitment and

apoptosis in the vessel wall.95,96

Patients with unstable coronary syndromes have elevated

levels of IL-6, CRP, and pentraxin-3,9799 which may be due

to increased inflammatory activity in their culprit lesions.

Importantly, even a modestly elevated CRP level is a risk

factor for coronary heart disease in healthy, middle-aged

men.100 This suggests that the modest inflammatory activity

of silent plaques results in a cascade leading to CRPproduction and also accelerates disease progression.

Th2, Th3, and More: Are Anti-inflammatory

Cytokines Antiatherosclerotic?Th2 cytokines such as IL-4, IL-5, and IL-10 are less abundant

than cytokines of the Th1 type in end-stage human lesions.64

In cell culture systems, IL-4 and IL-10 inhibit inflammatory

genes such as inducible nitric oxide (NO) synthase101 and

cyclooxygenase 2,102,103 but IL-4 also upregulates the scav-

enger receptor CD36 (Table 2). In apoE-KO mice, Th2

cytokines can be found in atherosclerotic lesions only in

conditions of excessive hypercholesterolemia, with serum

cholesterol levels of 40 to 50 mmol/L.104 Th1 and Th2

cytokines are cross-regulatory, IL-10 being an inhibitor of the

Th1 pathway and IL-12 a Th2 inhibitor. The low level of Th2

activity in lesions may be at least partly due to local IL-12secretion.65 There may be a corresponding IL-10 damper of

the Th1 response, because IL-10 containing areas of humanplaques exhibit reduced apoptosis and expression of inflam-

matory genes such as cytokine-inducible NO synthase.105

Interestingly, IL-10/ C57BL/6J mice exhibit increased fatty

streak development,106,107 and IL-10/ apoE/

compound-KO mice show increased plaque activation and

coronary thrombosis (G. Caligiuri, G.K. Hansson, and A.

Nicoletti, unpublished observations, 2001). However, IL-10

appears to be a cytokine secretioninhibiting cytokine with a

Figure 3. Antigen presentation of modified lipoproteins. WhenLDL is modified, eg, by oxidation, it is transformed into anautoantigen. Uptake by scavenger receptors (SR) leads to intra-cellular processing in macrophages (MPh) and presentation ofpeptide fragments on MHC class II molecules (MHC-II). T cellsthat carry the appropriate antigen receptors (TCR) are activatedby contact to the MHC-II:peptide complex in the presence ofcostimulatory factors (co-stim) such as CD4, CD40, and B7molecules. This results in T-cell activation, with proliferation andcytokine secretion.

TABLE 4. Effects of Immune Deficiency and Immunomodulation on Atherosclerosis

Experiment

Immune

Defect Immune Phenotype

Atherosclerosis

Model

Effect on

Disease

Reference

No.

Compound KO RAG-1 SCID ApoE 2 Athero 194

Compound KO RAG-2 SCID ApoEfatty diet No effect 195

Compound KO SCID/SCID SCID ApoE 2 Athero 197

Compound KO IFN- rec Defective Th1 ApoE 2 Athero 77

IvIg inj Immunosuppression ApoE 2 Athero 209

Anti-CD40 inj Immunosuppression LDLR 2 Athero 204

Compound KO CD40L Reduced immune activation ApoE 2 Athero 205

IFN- inj Increased Th1 ApoE 1 Athero 79

KO on B6 background TNF- rec Defective inflammation Fat feeding 2 Fatty streaks 230

KO on B6 background IL-10 Increased proinflammatory cytokines, 1 Th1 Fat feeding 1 Fatty streaks 106, 107

IvIg inj indicates intravenous immunoglobulin injection; rec, receptor; and athero, atherosclerosis. See text for explanation of other

abbreviations.

1880 Arterioscler Thromb Vasc Biol. December 2001



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broader set of targets than Th1 cells alone, and its effects may

not be equivalent to those of Th2 activity.

A third T-helper cell called Th3 was recently described.108

It produces TGF- on activation. This cytokine stimulates

collagen synthesis and is fibrogenic. Furthermore, it is

strongly anti-inflammatory, as illustrated by the fact that

TGF-KO mice die of fulminant inflammation by the age of6 weeks.109 TGF- and its receptor are present in the

atherosclerotic lesion,64,110 where it may act to stimulate

collagen synthesis and cap formation and to dampen inflam-

mation. Several different cell types, including macrophages,

SMCs, and Th3 cells, can express TGF-, which might be

important for plaque stabilization. The SMC growthpromot-ing action of T cells that release heparin-binding growth

factors might add to this effect.111

In conclusion, although Th1 cytokines are abundant in

lesions, it seems less likely that atherosclerosis will be

considered a strict Th1 disease. It might even be speculated

that different phases of this chronic disease are promoted by

different effector pathways. Clearly, the development andregulation of Th pathways in atherosclerosis require further

studies.

CD8 Cells andT Cells: Additional Players inthe Plaque Orchestra?CD8 T cells are found at varying proportions in human

lesions (Table 3). Most of the cytotoxic activity associated

with T cells is found in this subpopulation (Tc cells), which

is activated by cells that express proteasomally processed

peptide fragments of nascent proteins in the context of MHC

class I. It was recently shown that expression of a foreignantigen on vascular SMCs can lead to cytotoxic attack by

CD8 T cells.112 In an apoE-deficient mouse, this results in

significant aggravation of atherosclerosis. Thus, it is possible

that CD8 T cells cause some of the widespread apoptosis

that is associated with atherosclerosis.113 However, apoptosis

can also be induced by reactive oxygen and nitrogen species,

which are generated by macrophages and SMCs on stimula-

tion with proinflammatory cytokines.114 Therefore, activation

of CD4 as well as CD8 T cells can lead to cell death in

lesions. In addition, CD8 T cells may respond to antigens

not only by cytotoxic activity but also by secretion of

cytokines in a manner parallel to that observed for Th1 and

Th2 cells. Functional Tc1 and Tc2 subsets of CD8 T cells

seem to be important for the tissue response in mycobacterial

infections, but it is not known whether they play a role inatherosclerosis.

A third type of T cell has a CD3 4 8 phenotype and

expresses TCRs that are rather than dimers. Such T

cells are important in mucosal immunity and in the recogni-

tion of complex lipids as antigens. TCR binds such

antigens, which are presented on CD1 rather than MHC

proteins. The capacity ofT cells to recognize lipids makes

them potentially interesting in atherosclerosis. T cells and

CD1-expressing cells have been found at varying proportions

in arterial inflammatory lesions115 and atherosclerotic le-

sions,116,117 but their role remains unclear.

Other Immune Cells May Also Participate in theLocal Immune ResponseThe 2 other types of lymphocytes, B cells and natural killer

(NK) cells, are less frequent in atheroscleroticlesions than T

cells. Relatively few B and NK cells are found in advanced

human lesions, but prominent B-cell infiltrates may occur in

the adventitia and the periadventitial connective tissue.118

They can develop into pathological perivascular lymphoid

aggregates, a condition termed periaortitis.119 In lesions of

hypercholesterolemic rabbits and mice, B cells are relatively

abundant, and clones of immunoglobulin-producing cells canbe found.120,121 In humans as well as animals, IgG accumu-

lation is prominent in lesions.118,122 Some of these IgGs may

be specific for antigens present in the tissue. Although a

substantial proportion of the IgG may have entered the lesion

by filtration, there is also evidence for local synthesis.120

Plasma cells, which may secrete large amounts of IgG, are

present in lesions and are the likely source of this locally

produced IgG.

A different kind of hematopoietic cell, the mast cell, has

been identified in atherosclerotic lesions.20 Mast cells are less

frequent than macrophages and T cells but may be important

in plaque activation and acute coronary syndromes because

they produce several proteases and accumulate at sites ofplaque rupture.123125 Factors released from mast cells may

degrade the extracellular matrix126 and could also influence

the functions of surrounding cells and modify locally depos-

ited lipoproteins.127 Finally, the dendritic cell, which is a

specialized member of the macrophage lineage, has been

found in human and experimental atherosclerotic lesions.19,128

This cell performs a key role in immune activation because it

is specialized on antigen presentation and appears to be the

only cell that can activate naive T cells. It has a high

migratory capacity and maypatroltissues such as the arterywall in search of antigens, which are endocytosed and

transported to regional lymph nodes, where presentation of

the antigen to naive and memory T cells, and hence, induction

of adaptive immunity, can take place.

Immune Specificity in the Atherosclerotic Lesion

Restricted Heterogeneity Suggests LocalImmune ActivationThe antigen specificity of T cells is encoded in the sequence

of their rearranged TCR genes, which determine the confor-

mation of the antigen-binding site in the CDR3 domain of the

TCR protein.129 Because the rearrangement process is sto-

chastic, each nascent T cell carries a unique TCR gene and

protein. On activation, the stimulated T cell divides to give

rise to a clone of cells with identical specificities. Thepresence in tissue of a population of T cells with an identical

TCR is therefore indicative of clonal proliferation and hence,

of expansion of these particular T cells due to antigenic

stimulation. Such clonal expansions are found in early lesions

of apoE-KO mice.130 This finding is suggestive of local

clonal proliferation of T cells, which is compatible with

activation by local antigens. Interestingly, similar TCRs

containing the V6 variable domain are frequently expressed

by T cells that recognize oxidatively modified LDL, one of

the candidate antigens in atherosclerosis (A. Nicoletti, G.

Paulsson, and G.K. Hansson, unpublished observations,

2001).

In human lesions, the situation is more complex. A

heterogeneous population of TCRs and therefore, of T cells is

found in lesions,131 and the enormous allelic variation in


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MHC molecules, ie, HLA proteins, between individuals

makes it difficult to identify patterns that could reflect local

expansions of HLA-restricted T cells. Although this may be

partly due to technical difficulties, it seems unlikely that the

immunological situation in atherosclerosis could be as simple

as the one in type 1 diabetes, for example, where one specific

HLA-DQ allele permits an autoimmune response that leads to

-cell destruction and disease. Instead, it is likely that several

antigens and antigenic epitopes are involved and can be

presented by several different HLA alleles. Nevertheless,

autoantigens have also been identified in atherosclerosis.

OxLDL Is a Candidate AutoantigenAntibodies to oxLDL can be detected in atherosclerotic

patients and experimental animals119,132,133 and are present in

atherosclerotic lesions.134 These studies identified oxLDL as

a candidate antigen in atherosclerosis (Table 5). Further

support for this notion came with the identification of cellular

immune responses to oxLDL. T cells can be isolated from

fresh human plaques, cloned, expanded in culture, andchallenged with candidate antigens. By using this approach,

oxLDL was shown to be a major autoantigen in the cellular

immune response of atherosclerosis.135 One fourth of all

CD4 T cells cloned from human plaques recognized ox-

LDL in an HLA-DR dependent manner. OxLDL-specific Tcells are present in lymph nodes of apoE-KO mice,136,137

which have strong humoral as well as cellular immune

responses to such modified lipoproteins.138,139 In humans,

oxLDL induces activation of a subset of peripheral T cells,

suggesting that it is a quantitatively important antigen.140

The antibody specificity of IgG molecules in lesions can be

determined by isolating them and permitting them to reactwith an antigen, eg, in ELISA or Western blot analyses. With

this approach, it was demonstrated that IgGs of atheroscle-

rotic lesions contain antibodies reactive with oxLDL.134 The

antigens, ie, LDL carrying various kinds of oxidative modi-

fications, could be demonstrated in the lesions by immuno-

staining and Western blot. Therefore, oxLDL is an autoanti-

gen that is formed in the lesion, and it elicits a local cellular

as well as a humoral immune response.

The immune response to oxLDL plays a pathogenetic role

in atherosclerosis because lesion progression can be inhibited

by immunization141143 or induction of neonatal tolerance to

oxLDL.137 It seems paradoxical that both tolerization and

hyperimmunization can reduce the extent of disease; this may

be due to the different effector pathways activated by these

two kinds of treatment.

Heat Shock Proteins Are Common Autoantigens inInflammatory DiseaseHeat shock proteins have also been implicated in the patho-

genesis of atherosclerosis144 (Table 5). Such proteins are

involved in protein folding in the normal cell, are produced in

large amounts by injured cells, are released on tissue inju-

ry,145 and serve as targets for autoimmune responses in many

inflammatory diseases. Interestingly, heat shock proteins arealso released by monocytes exposed to oxLDL.146 Antibodies

to heat shock protein 60 (hsp60) and its prokaryotic homo-

logue hsp65 are frequently detected in rheumatoid arthritis

and other inflammatory conditions.145

Xu and coworkers147 immunized rabbits with hsp65/60 and

recorded induction of vascular inflammation, with endothelial

activation and mononuclear cell adhesion. The developing

lesions also contained T cells, and cell lines derived from

such infiltrates exhibited anti-hsp60 reactivity. Anti-hsp60

antibodies occurred in peripheral blood, and immunization

with hsp60 was found to increase fatty streak development in

hypercholesterolemic rabbits and mice.147,148

In humans,antibodies to hsp 65/60 are elevated in hypertension149 and

early atherosclerosis150 and may predict progression of ath-

erosclerotic disease.151 Because heat shock proteins of hu-

mans and microbes are structurally and antigenically similar,

it is possible that molecular mimicry between immune re-

sponses to microbial heat shock proteins and homologues

expressed by vascular cells could account for the association

between infections and atherosclerosis.152

A third autoantigen, 2-glycoprotein Ib (2-GPI), is pres-

ent on platelets but may also be expressed by endothelial cells

(Table 5). Autoantibodies to 2-GPI are produced in several

inflammatory disorders, including atherosclerosis.153,154 The

immune response to 2-GPI appears to be proatherogenic,because hyperimmunization with 2-GPI155 or transfer of

2-GPIreactive T cells aggravates fatty streak formation inLDLR/ mice.156 The pathogenetic mechanism by which

2-GPI acts remains unclear, but it may be related to this

proteins capacity to bind phospholipids.

A Role for Phospholipid Antibodiesin Atherosclerosis?Antibodies reacting with phospholipids such as cardiolipin

are associated with recurrent thrombosis157 and accelerated

atherosclerosis.158 Many of these antibodies recognize

phospholipid-binding plasma proteins such as -GPI,159 and

it could be speculated that 2-GPI affects atherosclerosis by

targeting immune responses to membrane lipids. Interest-

ingly, another set of phospholipid antibodies recognizes

TABLE 5. Candidate Antigens in Atherosclerosis

Antigen Type Processing Presentation Recognition Effect of Immun.

OxLDL Autoantigen Endosomal MHC-II CD4T (T?) 2 atheroma

hsp60 Autoantigen Endosomal, cytosolic MHC-II

MHC-I

CD4

CD8

1 atheroma

2-Gp1b Autoantigen Endosomal MHC-II CD4 fatty streak

C pneum Microbe Endosomal MHC-II CD4 ?

CMV Virus Cytosolic MHC-I CD8 ?

C pneum indicates Chlamydia pneumoniae; CMV, cytomegalovirus; and immun, immunization. See text for

explanation of other abbreviations.




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oxidized phospholipids in oxLDL160 and may representnat-ural antibodies that appear in early life and also bindphospholipids on apoptotic cells and certain bacteria.161

Perhaps pathogenic immune responses are due tomolecularmimicry between oxLDL and modified lipids on microbesand apoptotic cells.

Microbes as Antigens in AtherosclerosisIn 1988, Saikku et al162 discovered that patients with cardiovas-

cular diseases often have high-titer antibodies to Chlamydia

pneumoniae(Table 5). This common pathogen can cause pneu-

monia, but it has also been associated with a variety of other

chronic diseases. Further investigations revealed that C pneu-

moniaesurvives intracellularly in macrophages, can be detected

in atherosclerotic lesions, and can be isolated and grown from

such lesions.163165 This established that C pneumoniae is in-

volved in atherosclerosis. However, the extent ofC pneumoniae

infiltrates in lesions remains controversial,166 as does the impor-

tance of C pneumoniae infection as an aggravating factor in

experimental atherosclerosis.167170

It therefore remains to beclarified how important C pneumoniae is for disease develop-

ment and whether the microorganism or the immune response

against it can be harmful.

Viruses of the Herpesviridae family have also been implicated

in atherosclerosis (Table 5). Both herpes simplex type 1 and

cytomegalovirus have been detected in human lesions.171173 An

avian analogue, Mareks disease virus, aggravates cholesterol-induced atherosclerosis in chickens. Cytomegalovirus has been

linked to transplant arteriosclerosis174,175 and may also be asso-

ciated withgarden-varietyatherosclerosis and restenosis afterangioplasty.176,177 Several pathogenic mechanisms have been

proposed.178 Cell culture studies have identified a role for this

virus as a stimulus for smooth muscle migration and scavengerreceptor expression, which may be important in vascular pathol-

ogy.179 However, it appears that direct action of the virus, rather

than immune responses against it, is playing the important

pathogenic role.

Systemic Immune Responses and SerodiagnosisSystemic humoral immune responses are characteristic for

atherosclerotic disease in humans and experimental models.

Antibodies to oxidatively modified LDL are commonly found in

patients; as expected from the incidence of silent disease, they

are frequent also in healthy individuals.133,180 Immunodominant

epitopes in modified LDL include malondialdehyde-conjugated

and 4-hydroxynonenal conjugated lysine residues.139,181 Thesemodifications are generated by enzymatic or nonenzymatic

attack on fatty acid residues, which leads to release of reactive

aldehydes that can bind to the polypeptide chain of apoB-100.

Other B-cell epitopes on oxLDL include oxidized phospholipids

such as phosphorylcholine, which is also present on several

microbes and apoptotic cells and is recognized by naturalantibodies present in most individuals.161

Anti-oxLDL antibody titers are correlated with the pro-

gression of advanced atherosclerosis in some studies,133,182

whereas others have been unable to find any such correlation.

Interestingly, titers are correlated negatively with early car-

diovascular diseases, including borderline hypertension andcarotid intima/media thickening.183185 It appears that no

simple, positive correlation occurs between antibodies and

disease throughout its natural history. Instead, it may be that

bursts of plaque activity boost immune responses, possibly by

releasing antigenic material, and give rise to titer increases.

Such episodic activity might be interspersed with periods of

slow, silent growth of lesions and fading immune activity. It

is also possible that antibodies can serve to eliminate modi-

fied lipoproteins from the circulation, thus reducing the load

of atherogenic lipoproteins in arterial lesions. Antibodies maytherefore be viewed both as markers of disease activity and as

vehicles for clearance of antigen. The situation with regard to

other antigens appears to be similar to that for modified LDL.

Anti-hsp65/60 antibodies have been positively correlated

with the progression of carotid atherosclerotic disease in an

epidemiological study,151 but more data are needed before

these assays find their place in clinical diagnostics.

Evidence That Immunity Affects Atherosclerosis

Atherosclerosis in Patients With Immune DisordersIt is by now well established that atherosclerosis is accom-

panied by adaptive immune responses and that the earlyphase of the disease is dominated by immune cells, particu-

larly macrophages. These facts do not necessarily imply that

atherosclerosis can be treated or prevented by interfering with

immune mechanisms. To clarify whether that could be

possible, it has been important to determine whether the

extent of atherosclerosis is different (reduced or increased) in

individuals with immune defects.

The situation in immune-deficient patients is complicated

and difficult to interpret. Individuals with severe combined

immune deficiencies have not survived long enough to

develop cardiovascular disease, and most of the congenital

immune deficiencies affect too few patients to make epide-miological investigations into cardiovascular disease mean-

ingful. Individuals with selective, congenital defects in the

humoral immune responses are relatively frequent, and the

clinical syndrome is compatible with life into adult age.

These patients do not exhibit any reduced heart disease,

suggesting that humoral immunity does not aggravate athero-

sclerosis.186 HIV patients, who lack CD4 T cells (and

particularly Th1 activity), develop aggressive cardiovascular

disease, particularly when modern highly active antiretroviral

treatment has been used to prevent rapid development of

AIDS.187189 However, the protease inhibitor treatment may

itself cause metabolic syndromes, and it is difficult todetermine whether the increased cardiovascular morbidity is

due to the disease or its treatment.

Some of the most remarkable data in support of a link

between immunity and atherosclerosis come from epidemio-

logical studies of patients with autoimmune disorders. Pa-

tients with rheumatoid arthritis have a 2- to 5-fold increase in

cardiovascular morbidity and mortality,190 and patients with

systemic lupus erythematosus exhibit an even higher increase

in cardiovascular disease.191,192 Although some of this mor-

bidity is clearly due to small-vessel vasculitis associated with

the underlying autoimmune disease, there is also evidence for

atherosclerotic large-vessel disease in many cases. Interest-

ingly, patients with systemic lupus erythematosus share

several autoimmune phenomena with atherosclerotic pa-

tients.193 Further studies into these aspects are clearly needed.




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Mechanistic Insights From Gene-TargetedMouse ModelsTo clarify the role for adaptive immunity in atherosclerosis, it

was necessary to generate immunodeficient animal models

(Table 4). The apoE-KO mouse was crossed with the

recombinase-activating gene-1/ (RAG-1/) mouse, which

lacks functional T and B cells due to a mutation in therearrangement machinery. The offspring exhibited a 40%

reduction of atherosclerosis, indicating that adaptive immu-

nity accelerates disease.194 However, the impact of the im-

mune defect was undetectable in cases of excessive hyper-

cholesterolemia.194,195 This could be due to either an

overwhelming effect of very high cholesterol levels or a

qualitative difference in immune activity in this metabolic

condition. The finding of a Th13Th2 switch in severehypercholesterolemia104 supports the latter conclusion. Inter-

estingly, the atheroprotective effect of estrogens was recently

found to be lacking in immunodeficient mice, suggesting that

the atheroprotective effect of estrogen depends on estrogen

action via immune mechanisms.196

Whether this involvesswitches in effector functions remains to be determined.

A more recently constructed apoE/ scid/scid mouse,

which also lacks adaptive immunity, shows an even more

striking phenotype, with a 70% reduction of disease in

immunodeficient female apoE/ scid/scidmice compared

with immunocompetent apoE/ scid/ littermates197 (Table

4). Neither the RAG nor the SCID immunodeficient mice

exhibited any changes in serum cholesterol compared with

single-KO apoE/ mice; this points to important effects on

the vascular wall rather than on systemic metabolism for the

effect on atherosclerosis.

This conclusion was further supported when immune cell

populations were transferred into the apoE/ scid/scidmice.Transfer of CD4 T cells from immunocompetent apoE/

mice to immunodeficient apoE/ scid/scidmice increased

atherosclerosis dramatically in the recipient, from 27% to 79%

of the level in fully immunocompetent apoE/ mice.197 Trans-

ferred T cells migrated to lesions and induced expression of

MHC class II genes, probably through IFN-secretion. These

data show that immune activity increases atherosclerosis and

identifies CD4 T cells as the proatherogenic subset.

In another recent study, a T-cellmediated response to avascular autoantigen was found to aggravate atherosclerosis

in apoE-KO mice.112 These mice were bred with a mouse

strain that carries the -galactosidase gene under the control

of a smooth musclespecific promotor activated by atamoxifen-inducible Cre recombinase. When such mice were

immunized by injections of dendritic cells presenting

-galactosidase, CD8 T cells were activated to specifically

recognize this antigen. Subsequent induction of

-galactosidase expression in SMCs by tamoxifen treatment

led to a lytic attack of the SMCs by antigen-specific CD8 T

cells. This resulted in a dramatic increase in atherosclerosis.

Important Roles for Immunoregulatory CellSurface MoleculesImmune activation depends on interactions between proteins

displayed on the surfaces of adjacent cells as well as onsoluble cytokines. Such proteins include adhesion molecules,

such as ICAM-1, and the more narrowly expressed pairs of

costimulatory molecules. The latter include theT-cell protein

CD28, which binds 2 alternative counterreceptors, B7.1

(CD80) and B7.2 (CD86). CD28 ligation promotes T-cell

activation, whereas ligation of B7 proteins to the alternative

T-cell surface receptor, cytotoxic T-lymphocyte antigen-4

(CTLA-4, CD152), induces a negative signal for cell-

mediated immune responses. Soluble CTLA-4 proteins have

been used to inhibit immune reactions and can preventchronic rejection of organ transplants.198 However, they do

not appear to reduce experimental atherosclerosis.

Another costimulatory molecule, CD40, is expressed by B

cells and dendritic cells and can be induced on many different

cell types. It ligates the constitutively expressed T-cell

protein, CD40 ligand (CD40L, or CD154). This interaction is

necessary for T-B cell cooperation in the induction of

antibody responses. CD40 is constitutively expressed by

endothelial cells and can be induced in both vascular endo-

thelial cells and SMCs by stimulation with proinflammatory

cytokines and IFN-.199,200 Similarly, CD40L could be in-

duced on these cells by cytokine stimulation.200 Ligation of

CD40 leads to tissue factor expression by endothelial cellsand can stimulate proteinase secretion from macrophages and

SMCs.201203 Interestingly, CD40 and CD40L are present on

vascular cells and macrophages of atherosclerotic lesions, and

their activation may be involved in the progression of

atherosclerotic disease. Recent animal experiments support

this notion (Table 4). First, anti-CD40L antibody injections

reduced fatty streak development in LDLR mice.204 Second,

CD40L/ apoE/ compound-KO mice exhibited slower

induction of lesions than did the CD40L/ apoE/ con-

trols.205 These data suggest that inhibition of the CD40

pathway might be a means of treating atherosclerosis. How-

ever, the mechanism of action for inhibitors such as anti-

CD40L antibodies remains unclear and could involve not only

immunomodulation but also direct effects on vascular cells.

Can We Prevent Atherosclerosisby Immunization?

Encouraging Experimental Data for theImmune StrategyAfter having cited a wealth of studies that establish adap-

tiveand innateimmunity as proatherogenic, it may seemtotally unrealistic to ask whether immunization, ie, deliberate

activation of specific immunity, might protect against athero-

sclerosis. However, one should consider that several infec-

tions in which cellular immunity plays a pathogenic role canbe prevented by vaccination. Experimental autoimmune dis-

eases such as experimental autoimmune encephalomyelitis

can be prevented by protective immunization. It is now

evident that entirely different immune effector responses can

be induced against the same antigen, with some important

ones elicited by local antigen release in parenchymal tissue

and others by subcutaneous or oral immunization.

As discussed, several different antigens have been impli-

cated in the pathogenesis of atherosclerosis. Interestingly,

immunization with one of them, oxLDL, can reduce disease

in several animal models141143,206,207 (Table 4), whereas

immunization with hsp65/60 or 2-GPIb aggravates lesion

development147,148,155,156 (Table 4). The reason for this appar-

ent discrepancy is not known; however, there are important

differences between the antigens. Hsp60 is an intracellular




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molecule that can be expressed on the surface of stressed

cells. OxLDL, in contrast, is an extracellular particle that is

present in the interstitial space of the intima and may even

circulate in the blood.208 It could be speculated that protective

immunization against atherosclerosis works by inducing

high-titer antibodies that increase the clearance of oxLDL by

way of Fc and C3 receptors. In support of this, the protectiveeffect of oxLDL immunization can be correlated with the titer

of T-cell dependent IgG antibodies,143 and transfer of poly-clonal immunoglobulins, which contain anti-oxLDL antibod-

ies, reduces atherosclerosis in apoE/ mice.209

The detrimental effect of immunization with hsp60 may

depend on the fact that this protein can appear on the surface of

endothelial cells and/or SMCs. This could lead to antibody

binding that is followed by complement activation and lysis of

the vascular cells. In addition, peptides derived from hsp60

synthesis might bind to MHC class I molecules, which would

permit attack by cytolytic CD8 T cells. The potential impor-

tance of the latter pathway was recently demonstrated in mice in

which an autoimmune response to a transgene expressed onSMCs led to a CD8 T-cell attack on the vessel wall and

aggravation of atherosclerosis.112 It is possible that endogenous

antigens such as hsp60 could elicit a similar attack once a

cellular immune response has developed toward the protein.

Therapeutic Potential of Vaccinationand ImmunomodulationCan we use our current knowledge about immune activity in

atherosclerosis to prevent or treat the disease? Although no such

therapy is used clinically today, there is reason for optimism.

The success in protective immunization with oxLDL as an

immunogen in experimental models suggests that this could also

be a fruitful approach in humans. However, oxLDL is aheterogeneous particle that may be unsuitable for parenteral

administration in patients. It may also be extremely difficult to

standardize to the extent that is required for vaccines. For these

reasons, it will be necessary to identify the most important B-

and T-cell epitopes on oxLDL and to test whether either of them

can be used as an immunogen with the same success as the intact

particle. If this turns out to be the case, clinical trials should be

encouraged.

Immunomodulation is also attractive as a possible therapeutic

principle. However, broadly acting immunosuppressants such as

corticosteroids and cyclosporins have undesirable, direct vascu-

lar effects that make them unsuitable for this purpose. Instead,

we should try to develop more specific immunomodulators that

act on the key mechanisms in the pathogenesis of atherosclero-

sis. Potential targets are proinflammatory lipids such as PAF and

lysophosphatidylcholine, lipoprotein-derived antigens, and sig-

nal transduction pathways leading to inflammatory innate and

adaptive immune responses.

Interestingly, certain drugs targeting lipid and carbohydrate

metabolism may also act as immunomodulators. Statins act as

repressors of MHC class IImediated T-cell activation210 andcan improve the outcome of cardiac transplantation.211 Gli-

tazones, which are agonists for peroxisome-proliferator acti-

vating receptor-, can also inhibit T-cell activation and

cytokine secretion.

212

It is tempting to speculate that some ofthe beneficial effects of these types of compounds are due to

their immuomodulatory effects rather than their action on

cholesterol or glucose metabolism.

Because the proinflammatory/Th1 pathway appears to play

a key role, interference with signal transduction molecules,

receptors, or cytokines involved in this cascade could be

interesting as a potential therapeutic approach. TNF-antag-

onists are already in clinical use for rheumatoid arthritis and

have been tested clinically for heart failure. It will be

important to determine whether they also act against athero-sclerosis. Similarly, IFN antagonists and inhibitors of the

NF-B and Janus kinase/signal transducer and activator of

transcription (Jak/STAT) pathways could turn out to be

useful. Experimental studies have already shown beneficial

effects of blockers of the costimulatory molecules CD40/

CD40L; inhibition of this or similar costimulatory proteins

might also be effective against atherosclerosis (see above).

Finally, it would be theoretically attractive to apply an

immunomodulatory treatment that promotes anti-

inflammatory immunity. This might be accomplished by

enhancing the Th2 or TGF-/Th3 effector mechanisms, for

example, or by the more general inhibition of cell-mediated

immunity that can be achieved by treatment with large dosesof polyclonal immunoglobulins.209 The latter treatment, if

useful clinically, would have to be reserved for selected cases

of rapidly accelerating atherosclerosis. However, it may point

to a useful principle for immunomodulation that could be

used to develop more defined pharmaceuticals.

To summarize, several interesting drugs and immunogens

have shown effects against atherosclerosis in experimental

systems, and an additional set of molecules is attractive from

a theoretical point of view. We should have some interesting

years ahead of us.

AcknowledgmentsOur work is supported by the Swedish Heart-Lung Foundation andScience Council (project 6816) and by the Ragnar and TorstenSderberg foundation. I thank Johan Frostegrd, Zhong-qun Yan,and Xinghua Zhou for constructive criticism.

References1. Poole JCF, Florey HW. Changes in the endothelium of the aorta and the

behaviour of macrophages in experimental atheroma of rabbits. J Pathol

Bacteriol. 1958;75:245252.2. Schaffner T, Taylor K, Bartucci EJ, Fischer DK, Beeson JH, Glagov S,

Wissler RW. Arterial foam cells with distinctive immunomorphologic and

histochemical features of macrophages.Am J Pathol. 1980;100:5780.3. Fowler S, Shio H, Haley NJ.Characterization of lipid-laden aortic cellsfrom

cholesterol-fed rabbits, IV: investigation of macrophage-like properties of

aortic cell populations. Lab Invest. 1979;41:372378.4. Gerrity RG. The role of the monocyte in atherogenesis, I: transition of

blood-borne monocytes into foam cells in fatty lesions. Am J Pathol.

1981;103:181190.5. Gerrity RG. The role of the monocyte in atherogenesis, II: migration of

foam cells from atherosclerotic lesions.Am J Pathol. 1981;103:191200.6. Faggiotto A, Ross R. Studies of hypercholesterolemia in the nonhuman

primate, I: changes that lead to fatty streak formation. Arteriosclerosis.

1984;4:323340.7. Faggiotto A, Ross R. Studies of hypercholesterolemia in the nonhuman

primate, II: fatty streak conversion to fibrous plaque. Arteriosclerosis. 1984;

4:341356.8. Brown MS, Goldstein JL. A receptor-mediated pathway for cholesterol

homeostasis.Science. 1986;232:34 47.9. Fogelman AM, Shechter I, Seager J, Hokom M, Child JS, Edwards PA.

Malondialdehyde alteration of low density lipoproteins leads to cholesteryl

ester accumulation in human monocyte-macrophages.Proc Natl Acad Sci

U S A. 1980;77:2214 2218.10. Steinberg D, Parthasarathy S, Carew TE, Khoo JC, Witztum JL. Beyond

cholesterol: modifications of low-density lipoprotein that increase its athero-

genicity.N Engl J Med. 1989;320:915924.




12/16


13/16

56. Frostegrd J, Nilsson J, Haegerstrand A, Hamsten A, Wigzell H, GidlundM. Oxidized low density lipoprotein induces differentiation and adhesion of

human monocytes and the monocytic cell line U937.Proc Natl Acad Sci

U S A. 1990;87:904 908.57. Jovinge S, Ares MPS, Kallin B, Nilsson J. Human monocytes/macrophages

release TNF- in response to ox-LDL. Arterioscler Thromb Vasc Biol.

1996;16:15731579.58. Lehr HA, Seemuller J, Hubner C, Menger MD, Messmer K. Oxidized

LDL-induced leukocyte/endothelium interaction in vivo involves thereceptor for platelet-activating factor. Arterioscler Thromb. 1993;13:

10131018.59. Watson AD, Navab M, Hama SY, Sevanian A, Prescott SM, Stafforini DM,

McIntyre TM, Du BN, Fogelman AM, Berliner JA. Effect of platelet

activating factor-acetylhydrolase on the formation and action of minimally

oxidized low density lipoprotein. J Clin Invest. 1995;95:774 782.60. Frostegrd J, Huang YH, Ronnelid J, Schafer-Elinder L. Platelet-activating

factor and oxidized LDL induce immune activation by a common

mechanism.Arterioscler Thromb Vasc Biol. 1997;17:963968.61. Huang YH, Schafer-Elinder L, Wu R, Claesson HE, Frostegrd J. Lyso-

phosphatidylcholine (LPC) induces proinflammatory cytokines by a plate-

let-activating factor (PAF) receptor-dependent mechanism. Clin Exp

Immunol. 1999;116:326331.62. Wright SD. Toll, a new piece in the puzzle of innate immunity.J Exp Med.

1999;189:605 609.63. Costet P, Luo Y, Wang N, Tall AR. Sterol-dependent transactivation of the

ABC1 promoter by the liver X receptor/retinoid X receptor.J Biol Chem.

2000;275:2824028245.64. Frostegrd J, Ulfgren AK,Nyberg P, Hedin U, Swedenborg J, AnderssonU,

Hansson GK. Cytokine expression in advanced human atherosclerotic

plaques: dominance of pro-inflammatory (Th1) and macrophage-

stimulating cytokines.Atherosclerosis. 1999;145:33 43.65. Uyemura K, Demer LL, Castle SC, Jullien D, Berliner JA, Gately MK,

Warrier RR, Pham N, Fogelman AM, Modlin RL. Cross-regulatory roles of

interleukin (IL)-12 and IL-10 in atherosclerosis. J Clin Invest. 1996;97:

21302138.66. Ashkar S, Weber GF, Panoutsakopoulou V, Sanchirico ME, Jansson M,

Zawaideh S, Rittling SR, Denhardt DT, Glimcher MJ, Cantor H. Eta-1

(osteopontin): an early component of type-1 (cell-mediated) immunity.

Science. 2000;287:860 864.

67. Giachelli CM, Bae N, Almeida M, Denhardt DT, Alpers CE, Schwartz SM.Osteopontin is elevated during neointima formation in rat arteries and is a

novel component of human atherosclerotic plaques.J Clin Invest. 1993;92:

16861696.68. OBrien ER, Garvin MR, Stewart DK, Hinohara T, Simpson JB, Schwartz

SM, Giachelli CM. Osteopontin is synthesized by macrophage, smooth

muscle, and endothelial cells in primary and restenotic human coronary

atherosclerotic plaques. Arterioscler Thromb. 1994;14:1648 1656.69. Friesel R, Komoriya A, Maciag T. Inhibition of endothelial cell proliferation

by-interferon.J Cell Biol. 1987;104:689 696.70. Hansson GK, Hellstrand M, Rymo L, Rubbia L, Gabbiani G. Interferon-

inhibits both proliferation and expression of differentiation-specific

-smooth muscle actin in arterial smooth muscle cells. J Exp Med. 1989;

170:15951608.71. Peilot H, Rosengren B, Bondjers G, Hurt-Camejo E. Interferon-induces

secretory group IIA phospholipase A2 in human arterial smooth muscle

cells: involvement of cell differentiation, STAT-3 activation, and modu-lation by other cytokines. J Biol Chem. 2000;275:2289522904.

72. Hansson GK, Holm J. Interferon-inhibits arterial stenosis after injury.

Circulation. 1991;84:1266 1272.73. Amento EP, Ehsani N, Palmer H, Libby P. Cytokines and growth factors

positively and negatively regulate interstitial collagen gene expression in

human vascular smooth muscle cells. Arterioscler Thromb. 1991;11:

12231230.74. Hansson GK, Libby P. The role of the lymphocyte. In: Fuster V, Ross R,

Topol EJ, eds. Atherosclerosis and Coronary Artery Disease. Philadel-

phia/New York: Lippincott-Raven Publishers; 1995;1:557568.75. Libby P. Molecular bases of the acute coronary syndromes.Circulation.

1995;91:28442850.76. van der Wal AC, Becker AE, van der Loos CM, Das PK. Site of intimal

rupture or erosion of thrombosed coronary atherosclerotic plaques is char-

acterized by an inflammatory process irrespective of the dominant plaque

morphology.Circulation. 1994;89:36 44.77. Gupta S, Pablo AM, Jiang X-c, Wang N, Tall AR, Schindler C. IFN-

potentiates atherosclerosis in apoE knock-out mice. J Clin Invest. 1997;99:

27522761.

78. Tellides G, Tereb DA, Kirkiles-Smith NC, Kim RW, Wilson JH, Schechner

JS, Lorber MI, Pober JS. Interferon-elicits arteriosclerosis in the absence

of leukocytes. Nature. 2000;403:207211.79. Whitman SC, Ravisankar P, Elam H, Daugherty A. Exogenous interferon-

enhances atherosclerosis in apolipoprotein E-/- mice. Am J Pathol. 2000;

157:18191824.80. Barath P, Fishbein MC, Cao J, Berenson J, Helfant RH, Forrester JS.

Detection and localization of tumor necrosis factor in human atheroma.

Am J Cardiol. 1990;65:297302.81. Moyer CF, Sajuthi D, Tulli H, Williams JK. Synthesis of IL-1and IL-1

by arterial cells in atherosclerosis. Am J Pathol. 1992;138:951960.82. Libby P, Warner S, Friedman GB. Interleukin-1: a mitogen for human

vascular smooth muscle cells that induces the release of growth-inhibitory

prostanoids.J Clin Invest. 1988;81:487498.83. Tingstrm A, Reuterdahl C, Lindahl P, Heldin CH, Rubin K. Expression of

platelet-derived growth factor-receptors on human fibroblasts: regulation

by recombinant platelet-derived growth factor-BB, IL-1, and tumor necrosis

factor-. J Immunol. 1992;148:546554.84. Sarn P, Welgus HG, Kovanen PT. TNF- and IL-1 selectively induce

expression of 92-kDa gelatinase by human macrophages.J Immunol. 1996;

157:41594165.85. Beutler B, Mahoney J, Le Trang N, Pekala P, Cerami A. Purification of

cachectin, a lipoprotein lipase-suppressing hormone secreted by endotoxin-

induced RAW 264.7 cells. J Exp Med. 1985;161:984995.

86. Beutler BA, Cerami A. Recombinant interleukin 1 suppresses lipoproteinlipase activity in 3T3-L1 cells. J Immunol. 1985;135:3969 3971.

87. Tracey KJ, Cerami A. Metabolic responses to cachectin/TNF: a brief

review.Ann N Y Acad Sci. 1990;587:325331.88. Nilsson J, Jovinge S, Niemann A, Reneland R, Lithell H. Relation between

plasma tumor necrosis factor- and insulin sensitivity in elderly men with

noninsulin-dependent diabetes mellitus. Arterioscler Thromb Vasc Biol.1998;18:11991202.

89. Jovinge S, Hamsten A, Tornvall P, Proudler A, Bvenholm P, Ericsson CG,Godsland I, de Faire U, Nilsson J. Evidence for a role of tumor necrosis

factor- in disturbances of triglyceride and glucose metabolism predis-

posing to coronary heart disease. Metabolism. 1998;47:113118.90. Introna M, Mantovani A. Early activation signals in endothelial cells:

stimulation by cytokines. Arterioscler Thromb Vasc Biol. 1997;17:

423 428.91. Gewurz H, Zhang XH, Lint TF. Structure and function of the pentraxins.

Curr Opin Immunol. 1995;7:54 64.92. Loppnow H, Libby P. Proliferating or interleukin 1-activated human

vascular smooth muscle cells secrete copious interleukin 6. J Clin Invest.

1990;85:731738.93. Ikeda U, Ikeda M, Seino Y, Takahashi M, Kano S, Shimada K. Interleukin

6 gene transcripts are expressed in atherosclerotic lesions of genetically

hyperlipidemic rabbits.Atherosclerosis. 1992;92:213218.94. Viedt C, Hansch GM, Brandes RP, Kubler W, Kreuzer J. The terminal

complement complex C5b-9 stimulates interleukin-6 production in human

smooth muscle cells through activation of transcription factors NF-B and

AP-1.FASEB J. 2000;14:2370 2372.95. Pasceri V, Willerson JT, Yeh ET. Direct proinflammatory effect of

C-reactive protein on human endothelial cells. Circulation. 2000;102:

21652168.96. Rovere P, Peri G, Fazzini F, Bottazzi B, Doni A, Bondanza A, Zimmermann

VS, Garlanda C, Fascio U, Sabbadini MG, Rugarli C, Mantovani A,

Manfredi AA. The long pentraxin PTX3 binds to apoptotic cells and reg-ulates their clearance by antigen-presenting dendritic cells. Blood. 2000;96:

43004306.97. Liuzzo G, Biasucci LM, Gallimore JR, Grillo RL, Rebuzzi AG, Pepys MB,

Maseri A. The prognostic value of C-reactive protein and serum amyloid A

protein in severe unstable angina. N Engl J Med. 1994;331:417424.98. Biasucci LM, Vitelli A, Liuzzo G, Altamura S, Caligiuri G, Monaco C,

Rebuzzi AG, Ciliberto G, Maseri A. Elevated levels of interleukin-6 in

unstable angina. Circulation. 1996;94:874 877.99. Peri G, Introna M, Corradi D, Iacuitti G, Signorini S, Avanzini F, Pizzetti F,

Maggioni AP, Moccetti T, Metra M, Cas LD, Ghezzi P, Sipe JD, Re G,

Olivetti G, Mantovani A, Latini R. PTX3, a prototypical long pentraxin, is

an early indicator of acute myocardial infarction in humans. Circulation.

2000;102:636 641.100. Ridker PM, Rifai N, Stampfer MJ, Hennekens CH. Plasma concentration of

interleukin-6 and the risk of future myocardial infarction among apparently

healthy men.Circulation. 2000;101:17671772.101. Bogdan C, Vodovotz Y, Paik J, Xie Q-w, Nathan C. Mechanism of sup-

pression of nitric oxide synthase expression by interleukin-4 in primary

mouse macrophages.J Leukoc Biol. 1994;55:227233.


http://atvb.ahajournals.org/http://atvb.ahajournals.org/http://atvb.ahajournals.org/http://atvb.ahajournals.org/http://atvb.ahajournals.org/http://atvb.ahajournals.org/http://atvb.ahajournals.org/http://atvb.ahajournals.org/


14/16

102. Niiro H, Otsuka T, Kuga S, Nemoto Y, Abe M, Hara N, Nakano T, Ogo T,

Niho Y. IL-10 inhibits prostaglandin E2production by lipopolysaccharide-

stimulated monocytes.Int Immunol. 1994;6:661 664.103. Mehindate K, al-Daccak R, Aoudjit F, Damdoumi F, Fortier M, Borgeat P,

Mourad W. Interleukin-4, transforming growth factor1, and dexametha-

sone inhibit superantigen-induced prostaglandin E2-dependent collagenase

gene expression through their action on cyclooxygenase-2 and cytosolic

phospholipase A2. Lab Invest. 1996;75:529538.

104. Zhou X, Paulsson G, Stemme S, Hansson GK. Hypercholesterolemia isassociated with a Th1/Th2 switch of the autoimmune response in athero-

sclerotic apo E-knockout mice.J Clin Invest. 1998;101:17171725.105. Mallat Z, Heymes C, Ohan J, Faggin E, Leseche G, Tedgui A. Expression

of interleukin-10 in advanced human atherosclerotic plaques: relation to

inducible nitric oxide synthase expression and cell death. Arterioscler

Thromb Vasc Biol. 1999;19:611616.106. Mallat Z, Besnard S, Duriez M, Deleuze V, Emmanuel F, Bureau MF,

Soubrier F, Esposito B, Duez H, Fievet C, Staels B, Duverger N, Scherman

D, Tedgui A. Protective role of interleukin-10 in atherosclerosis. Circ Res.

1999;85:e17 e24.107. Pinderski-Oslund LJ, Hedrick CC, Olvera T, Hagenbaugh A, Territo M,

Berliner JA, Fyfe AI. Interleukin-10 blocks atherosclerotic events in vitro

and in vivo. Arterioscler Thromb Vasc Biol. 1999;19:28472853.108. Shi FD, Li H, Wang H, Bai X, van der Meide PH, Link H, Ljunggren HG.

Mechanisms of nasal tolerance induction in experimental autoimmune

myasthenia gravis: identification of regulatory cells. J Immunol. 1999;162:57575763.

109. Kulkarni AB, HuhCG, Becker D, Geiser A, Lyght M, Flanders KC,Roberts

AB, Sporn MB, Ward JM, Karlsson S. Transforming growth factor 1 null

mutation in mice causes excessive inflammatory response and early death.

Proc Natl Acad Sci U S A. 1993;90:770 774.110. McCaffrey TA, Du B, Consigli S, Szabo P, Bray PJ, Hartner L, Weksler

BB, Sanborn TA, Bergman G, Bush HL. Genomic instability in the type II

TGF-1 receptor gene in atherosclerotic and restenotic vascular cells. J Clin

Invest. 1997;100:21822188.111. Peoples GE, Blotnick S, Takahashi K, Freeman MR, Klagsbrun M, Eberlein

TJ. T lymphocytes that infiltrate tumors and atherosclerotic plaques produce

heparin-binding epidermal growth factor-like growth factor and basic

fibroblast growth factor: a potential pathologic role. Proc Natl Acad Sci

U S A. 1995;92:6547 6551.112. Ludewig B, Freigang S, Jaggi M, Kurrer MO, Pei YC, Vlk L, Odermatt B,

Zinkernagel RM, Hengartner H. Linking immune-mediated arterial inflam-mation and cholesterol-induced atherosclerosis in a transgenic mouse

model.Proc Natl Acad Sci U S A. 2000;97:1275212757.113. Geng YJ, Henderson LE, Levesque EB, Muszynski M, Libby P. Fas is

expressed in human atherosclerotic intima and promotes apoptosis of cyto-

kine-primed human vascular smooth muscle cells. Arterioscler Thromb

Vasc Biol. 1997;17:2200 2208.114. Geng Y-J, Wu Q, Muszynski M, Hansson GK, Libby P. Apoptosis of

vascular smooth muscle cells induced by in vitro stimulation with

interferon-, tumor necrosis factor-, and interleukin-1. Arterioscler

Thromb Vasc Biol. 1996;16:19 27.115. Seitz CS, Kleindienst R, Xu QB, Wick G. Coexpression of heat-shock

protein 60 and intercellular-adhesion molecule-1 is related to increased

adhesion of monocytes and T cells to aortic endothelium of rats in response

to endotoxin.Lab Invest. 1996;74:241252.116. Kleindienst R, Xu Q, Willeit J, Waldenberger FR, Weimann S, Wick G.

Immunology of atherosclerosis: demonstration of heat shock protein 60

expression and T lymphocytes bearing / or /receptor in human ath-

erosclerotic lesions. Am J Pathol. 1993;142:19271937.117. Melian A, Geng YJ, Sukhova GK, Libby P, Porcelli SA. CD1 expression in

human atherosclerosis: a potential mechanism for T cell activation by foam

cells.Am J Pathol. 1999;155:775786.118. Parums DV, Chadwick DR, Mitchinson MJ. The localization of immuno-

globulin in chronic periaortitis. Atherosclerosis. 1986;61:117123.119. Parums DV, Brown DL, Mitchinson MJ. Serum antibodies to oxidized

low-density lipoprotein and ceroid in chronic periaortitis. Arch Pathol Lab

Med. 1990;114:383387.120. Sohma Y, Sasano H, Shiga R, Saeki S, Suzuki T, Nagura H, Nose M,

Yamamoto T. Accumulation of plasma cells in atherosclerotic lesions of

Watanabe heritable hyperlipidemic rabbits.Proc Natl Acad Sci U S A. 1995;

92:49374941.121. Zhou X, Hansson GK. Detection of B cells and proinflammatory cytokines

in atherosclerotic plaques of hypercholesterolemic apoE knockout mice.

Scand J Immunol. 1999;50:2530.122. Hansson GK, Holm J, Kral JG. Accumulation of IgG and complement

factor C3 in human arterial endothelium and atherosclerotic lesions. Acta

Pathol Microbiol Immunol Scand A. 1984;92:429 435.

123. Kovanen PT, Kaartinen M, Paavonen T. Infiltrates of activated mast cells at

the site of coronary atheromatous erosion or rupture in myocardial

infarction.Circulation. 1995;92:1084 1088.124. Kaartinen M, Penttila A, Kovanen PT. Mast cells in rupture-prone areas of

human coronary atheromas produce and store TNF-. Circulation. 1996;

11:27872792.125. Kaartinen M, van der Wal AC, van der Loos CM, Piek JJ, Koch KT, Becker

AE, Kovanen PT. Mast cell infiltration in acute coronary syndromes: impli-

cations for plaque rupture. J Am Coll Cardiol. 1998;32:606 612.126. Saarinen J, Kalkkinen N, Welgus HG, Kovanen PT. Activation of human

interstitial procollagenase through direct cleavage of the Leu83-Thr84 bond

by mast cell chymase. J Biol Chem. 1994;269:18134 18140.127. Lindstedt KA, Kokkonen JO, Kovanen PT. Soluble heparin proteoglycans

released from stimulated mast cells induce uptake of low density

lipoproteins by macrophages via scavenger receptor-mediated phagocytosis.

J Lipid Res. 1992;33:6575.128. Bobryshev YV, Lord RSA. Ultrastructural recognition of cells with den-

dritic cell morphology in human aortic intima: contacting interactions of

vascular dendritic cells in athero-resistant and athero-prone areas of the

normal aorta.Arch Histol Cytol. 1995;58:307322.129. Bentley GA, Mariuzza RA. The structure of the T cell antigen receptor.

Annu Rev Immunol. 1996;14:563590.130. Paulsson G, Zhou X, Trnquist E, Hansson GK. Oligoclonal T cell

expansions in atherosclerotic lesions of apoE-deficient mice. Arterioscler

Thromb Vasc Biol. 2000;20:1017.131. Stemme S, Rymo L, Hansson GK. Polyclonal origin of T lymphocytes in

human atherosclerotic plaques.Lab Invest. 1991;65:654 660.132. Palinski W, Rosenfeld ME, Yl-Herttuala S, Gurtner GC, Socher SS, Butler

SW, Parthasarathy S, Carew TE, Steinberg D, Witztum JL. Low density

lipoprotein undergoes oxidative modification in vivo. Proc Natl Acad Sci

U S A. 1989;86:13721376.133. Salonen JT, Yl-Herttuala S, Yamamoto R, Butler S, Korpela H, Salonen R,

Nyyssnen K, Palinski W, Witztum JL. Autoantibody against oxidised LDLand progression of carotid atherosclerosis.Lancet. 1992;339:883887.

134. Yl-Herttuala S, Palinski W, Butler SW, Picard S, Steinberg D, Witztum JL.Rabbit and human atherosclerotic lesions contain IgG that recognizes

epitopes of oxidized LDL. Arterioscler Thromb. 1994;14:32 40.135. Stemme S, Faber B, Holm J, Wiklund O, Witztum JL, Hansson GK. T

lymphocytes from human atherosclerotic plaques recognize oxidized LDL.

Proc Natl Acad Sci U S A. 1995;92:38933897.

136. Caligiuri G, Nicoletti A, Trnberg I, Zhou X, Hansson GK. Effects of sexand age on atherosclerosis and autoimmunity in apoE-deficient mice. Ath-

erosclerosis. 1999;145:301308.137. Nicoletti A, Paulsson G, Caligiuri G, Zhou X, Hansson GK. Induction of

neonatal tolerance to oxidized lipoprotein reduces atherosclerosis in apoE

knockout mice.Mol Med. 2000;6:283290.138. Palinski W, Ord V, Plump AS, Breslow JL, Steinberg D, Witztum JL.

ApoE-deficient mice are a model of lipoprotein oxidation in atherogenesis:

demonstration of oxidation-specific epitopes in lesions and high titers of

autoantibodies to malondialdehyde-lysine in serum. Arterioscler Thromb.

1994;14:605616.139. Palinski W, HrkkS, Miller E, Steinbrecher UP, Powell HC, Curtiss LK,

Witztum JL. Cloning of monoclonal autoantibodies to epitopes of oxidized

lipoproteins from apolipoprotein E-deficient mice: demonstration of

epitopes of oxidized low density lipoprotein in human plasma.J Clin Invest.

1996;98:800814.

140. Frostegrd J, Wu R, Giscombe R, Holm G, Lefvert AK,Nilsson J. Inductionof T-cell activation by oxidized low density lipoprotein. Arterioscler

Thromb. 1992;12:461467.141. Palinski W, Miller E, Witztum JL. Immunization of low density lipoprotein

(LDL) receptor-deficient rabbits with homologous malondialdehyde-

modified LDL reduces atherogenesis.Proc Natl Acad Sci U S A. 1995;92:

821 825.142. Ameli S, Hultgrdh-Nilsson A, Regnstrm J, Calara F, Yano J, Cercek B,

Shah PK, Nilsson J. Effect of immunization with homologous LDL and

oxidized LDL on early atherosclerosis in hypercholesterolemic rabbits.

Arterioscler Thromb Vasc Biol. 1996;16:10741079.143. Zhou X, Caligiuri G, Hamsten A, Lefvert AK, Hansson GK. Protection

against atherosclerosis by LDL immunization is associated with T cell de-pendent IgG antibodies in apoE-deficient mice. Arterioscler Thromb Vasc

Biol. 2001;21:108 114.144. Wick G, Schett G, Amberger A, Kleindienst R, Xu Q. Is atherosclerosis an

immunologically mediated disease?Immunol Today. 1995;16:2733.145. Kiessling R, Gronberg A, Ivanyi J, Soderstrom K, Ferm M, Kleinau S,

Nilsson E, Klareskog L. Role of hsp60 during autoimmune and bacterial

inflammation.Immunol Rev. 1991;121:91111.


http://atvb.ahajournals.org/http://atvb.ahajournals.org/http://atvb.ahajournals.org/http://atvb.ahajournals.org/http://atvb.ahajournals.org/http://atvb.ahajournals.org/http://atvb.ahajournals.org/http://atvb.ahajournals.org/http://atvb.ahajournals.org/


15/16

146. Frostegard J, Kjellman B, Gidlund M, Andersson B, Jondahl M, Kiessling

R. Induction of heat shock protein in monocytic cells by oxidized low

density lipoprotein.Atherosclerosis. 1996;121:93103.147. Xu Q, Dietrich H, Steiner HJ, Gown AM, Schoel B, Mikuz G, Kaufmann

S, Wick G. Induction of arteriosclerosis in normocholesterolemic rabbits by

immunization with heat shock protein 65. Arterioscler Thromb. 1992;12:

789799.148. George J, Shoenfeld Y, Afek A, Gilburd B, Keren P, Shaish A, Kopolovic

J, Wick G, Harats D. Enhanced fatty streak formation in C57BL/6J mice byimmunization with heat shock protein-65. Arterioscler Thromb Vasc Biol.

1999;19:505510.149. Frostegard J, Lemne C, Andersson B, van der Zee R, Kiessling R, de Faire

U. Association of serum antibodies to heat-shock protein 65 with borderline

hypertension.Hypertension. 1997;29:40 44.150. Pockley AG, Wu R, Lemne C, Kiessling R, de Faire U, Frostegard J.

Circulating heat shock protein 60 is associated with early cardiovascular

disease. Hypertension. 2000;36:303307.151. Xu Q, Willeit J, Marosi M, Kleindienst R, Oberhollenzer F, Kiechl S,

Stulnig T, Luef G, Wick G. Association of serum antibodies to heat-shock

protein 65 with carotid atherosclerosis. Lancet. 1993;341:255259.152. Mayr M, Metzler B, Kiechl S, Willeit J, Schett G, Xu Q, Wick G. Endo-

thelial cytotoxicity mediated by serum antibodies to heat shock proteins of

Escherichia coli and Chlamydia pneumoniae: immune reactions to heat

shock proteins as a possible link between infection and atherosclerosis.

Circulation. 1999;99:1560 1566.153. Frostegard J, Wu R, Gillis-Haegerstrand C, Lemne C, de Faire U. Anti-

bodies to endothelial cells in borderline hypertension. Circulation. 1998;98:

10921098.154. Shoenfeld Y, Harats D, George J. Atherosclerosis and the antiphospholipid

syndrome: a link unravelled?Lupus. 1998;7:S140S143.155. George J, Afek A, Gilburd B, Blank M, Levy Y, Aron-Maor A, Levkovitz

H, Shaish A, Goldberg I, Kopolovic J, Harats D, Shoenfeld Y. Induction of

early atherosclerosis in LDL-receptor-deficient mice immunized with

2-glycoprotein I. Circulation. 1998;98:1108 1115.156. George J, Harats D, Gilburd B, Afek A, Shaish A, Kopolovic J, Shoenfeld

Y. Adoptive transfer of(2)-glycoprotein I-reactive lymphocytes enhances

early atherosclerosis in LDL receptor-deficient mice. Circulation. 2000;102:

18221827.157. Hughes GR. The antiphospholipid syndrome: ten years on. Lancet. 1993;

342:341344.

158. Lecerf V, Alhenc-Gelas M, Laurian C, Bruneval P, Aiach M, Cormier JM,Fiessinger JN. Antiphospholipid antibodies and atherosclerosis. Am J Med.

1992;92:575576.159. Roubey RA. Autoantibodies to phospholipid-binding plasma proteins: a

new view of lupus anticoagulants and other antiphospholipid autoanti-bodies.Blood. 1994;84:28542867.

160. HrkkS, Miller E, Dudl E, Reaven P, Curtiss LK, Zvaifler NJ, TerkeltaubR, Pierangeli SS, Branch DW, Palinski W, Witztum JL. Antiphospholipid

antibodies are directed against epitopes of oxidized phospholipids: recog-

nition of cardiolipin by monoclonal antibodies to epitopes of oxidized low

density lipoprotein.J Clin Invest. 1996;98:815 825.161. Shaw PX, Horkko S, Chang MK, Curtiss LK, Palinski W, Silverman GJ,

Witztum JL. Natural antibodies with the T15 idiotype may act in athero-

sclerosis, apoptotic clearance, and protective immunity. J Clin Invest. 2000;

105:17311740.162. Saikku P, Leinonen M, Mattila K, Ekman MR, Nieminen MS, MkelPH,

Huttunen JK, Valtonen V. Serological evidence of an association of a novelChlamydia, TWAR, with chronic coronary heart disease and acute myo-

cardial infarction. Lancet. 1988;2:983986.163. Kuo CC, Gown AM, Benditt EP, Grayston JT. Detection ofChlamydia

pneumoniae in aortic lesions of atherosclerosis by immunocytochemical

stain.Arterioscler Thromb. 1993;13:15011504.164. Muhlestein JB, Hammond EH, Carlquist JF, Radicke E, Thomson MJ,

Karagounis LA, Woods ML, Anderson JL. Increased incidence of

Chlamydia species within the coronary arteries of patients with symptomatic

atherosclerotic versus other forms of cardiovascular disease. J Am Coll

Cardiol. 1996;27:15551561.165. Saikku P. Chlamydia pneumoniae and atherosclerosis: an update. Scand

J Infect Dis Suppl. 1997;104:5356.166. Weiss SM, Roblin PM, Gaydos CA, Cummings P, Patton DL, Schulhoff N,

Shani J, Frankel R, Penney K, Quinn TC, Hammerschlag MR, Schachter J.

Failure to detectChlamydia pneumoniaein coronary atheromas of patients

undergoing atherectomy.J Infect Dis. 1996;173:957962.167. Moazed TC, Campbell LA, Rosenfeld ME, Grayston JT, Kuo CC.

Chlamydia pneumoniaeinfection accelerates the progression of atheroscle-

rosis in apolipoprotein E-deficient mice. J Infect Dis. 1999;180:238241.

168. Hu H, Pierce GN, Zhong G. The atherogenic effects ofChlamydia are

dependent on serum cholesterol and specific to Chlamydia pneumoniae.

J Clin Invest. 1999;103:747753.169. Caligiuri G, Rottenberg M, Nicoletti A, Wigzell H, Hansson GK.

Chlamydia pneumoniaeinfection does not induce or modify atherosclerosis

in mice.Circulation. 2001;103:2834 2838.170. Aalto-SetalaK, Laitinen K, Erkkila L, LeinonenM, Jauhiainen M, Ehnholm

C, Tamminen M, Puolakkainen M, Penttila I, Saikku P. Chlamydia pneu-

moniaedoes not increase atherosclerosis in the aortic root of apolipoproteinE deficient mice.Arterioscler Thromb Vasc Biol. 2001;21:578 584.

171. Hendrix MGR, Salimans MMM, Boven CPA, van Bruggeman CA. High

prevalence of latently present cytomegalovirus in arterial walls of patients

suffering from grade III atherosclerosis. Am J Pathol. 1990;136:2328.172. Nicho

arterioscler thromb vasc biol 2001 hansson 1876 90

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