This Article Abstract Full Text (PDF) All Versions of this Article: 108/17/2107    most recent 01.CIR.0000092891.55157.A7v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Karvonen, J. Articles by Hörkkö, S. Search for Related Content PubMed PubMed Citation Articles by Karvonen, J. Articles by Hörkkö, S. Related Collections Pathophysiology

(Circulation. 2003;108:2107.)
© 2003 American Heart Association, Inc.

Clinical Investigation and Reports

Immunoglobulin M Type of Autoantibodies to Oxidized Low-Density Lipoprotein Has an Inverse Relation to Carotid Artery Atherosclerosis

From the Department of Internal Medicine (J.K., Y.A.K., S.H.), Biocenter Oulu (J.K., Y.A.K., S.H.), and Department of Diagnostic Radiology (M.P.), University of Oulu, Finland.

Correspondence to Jarkko Karvonen, Department of Internal Medicine, University of Oulu, P.O. Box 5000, FIN-90014, University of Oulu, Finland. E-mail jakarvon{at}paju.oulu.fi

Received November 15, 2002; de novo received May 20, 2003; revision received July 2, 2003; accepted July 8, 2003.

	Abstract

Top Abstract Introduction Methods Results Discussion References

 
Background— Lipoprotein oxidation plays an important part in atherogenesis. Autoantibodies to oxidation-specific epitopes of LDL occur in plasma and atherosclerotic lesions of humans and animals. The potential role of these autoantibodies in atherogenesis still remains unsolved. We studied the relationship between different isotypes of autoantibodies to copper-oxidized LDL and malondialdehyde-modified LDL (MDA-LDL) and carotid artery intima-media thickness (IMT) in a population-based cohort of 1022 middle-aged men and women. In addition, we studied the relation of C-reactive protein (CRP) to IMT.

Methods and Results— The levels of IgM, IgG, and IgG2 autoantibodies binding to MDA-LDL and copper-oxidized LDL were determined in plasma samples by chemiluminescence-based ELISA. IMT and the number of plaques were measured ultrasonographically. The subjects were divided into tertiles for antibody titers. We found an inverse association between IMT and IgM autoantibody titers to MDA-LDL that remained statistically significant after adjusting for age, gender, LDL cholesterol, systolic blood pressure, CRP, and smoking. CRP was not independently associated with IMT.

Conclusions— These results show that IgM autoantibodies to MDA-LDL have an inverse association with carotid atherosclerosis. The possible implications of this finding are discussed.

Key Words: antibodies • lipoproteins • atherosclerosis

	Introduction

Top Abstract Introduction Methods Results Discussion References

 
Hypercholesterolemia is the major factor involved in the initiation of fatty streak formation, the initial lesion of the atherogenic process. However, there are numerous other factors that may influence the transformation of these fatty streaks into complex plaques.¹ It is now well recognized that this progressive atherogenic process has many characteristics of a chronic inflammatory process, and experimental evidence in animal models demonstrate that the immune system plays an important role and may alter the course of the atherosclerotic process.^2,3

Lipoprotein oxidation is known to enhance atherogenesis by several different of mechanisms.^2,3 During oxidation, a variety of highly reactive breakdown products, such as malondialdehyde (MDA),⁴ are generated, which additionally modify closely associated lipids and proteins into immunogenic epitopes. Autoantibodies to oxidation-specific epitopes of LDL, such as MDA-modified LDL (MDA-LDL), occur in plasma and atherosclerotic lesions of humans and animals.^5–7 The potential role of these autoantibodies in the atherogenic process is complex and still remains unsolved. Indeed, some studies demonstrate that immunization of animals with oxidized LDL (OxLDL) induces high levels of antibodies to OxLDL and decreases atherosclerosis,^8–11 whereas other studies demonstrate elevated antibody titers to OxLDL in humans and animals with increased atherosclerosis.^12–14

The relationship between carotid artery intima-media thickness (IMT) and cardiovascular diseases has been well documented.¹⁵ The aim of the present study was to investigate the relationship between different isotypes of autoantibodies to OxLDL and carotid artery IMT in a large, randomly selected population-based cohort of middle-aged men and women (n=1022). In addition, we measured CRP and investigated its relationship to IMT.

	Methods

Top Abstract Introduction Methods Results Discussion References

 
Sample
The Oulu Project Elucidating Risk of Atherosclerosis (OPERA) project is a population-based, epidemiological study addressing the risk factors and end points of atherosclerotic cardiovascular diseases. The detailed study design has been previously described.¹⁶ The participants were randomly selected from Finnish national population registers. In this study, a total of 1022 participants (508 men and 514 women) were screened. Eighty-three subjects had coronary heart disease, and 58 subjects were diabetic. Five hundred twenty-nine subjects used blood pressure-lowering medication, 29 subjects used lipid-lowering medication, 55 subjects used aspirin, 17 subjects used oral diabetes medication, 12 subjects used insulin, and 109 subjects were undergoing hormone replacement therapy. The characteristics of the participants are shown in Table 1. The study was approved by the Ethical Committee of the Faculty of Medicine, University of Oulu, and followed the Declaration of Helsinki.

Clinical Measurements
Plasma cholesterol levels were determined by enzymatic colorimetric methods, and lipoprotein fractions were separated by ultracentrifugation. The glucose concentrations were measured using the glucose-oxidase method (Diagnostica, Merck). C-reactive protein was measured using commercially available ELISA kits (Diagnostic Systems Laboratories).

Autoantibody Measurements to OxLDL
The levels of IgM and IgG and IgG2 autoantibodies binding to MDA-LDL and copper-oxidized (CuOx)-LDL were determined by chemiluminescence-based ELISA.¹⁷ MDA-LDL and CuOx-LDL were generated as previously described,^10,18 and the degree of the modification was verified by TNBS method¹⁹ and testing monoclonal anti-OxLDL antibody binding (EO6 binding¹⁷). The same modified LDL preparation was used throughout the study. Antigens at 10 µg/mL in PBS-EDTA (PBS with 0.27 mmol/L EDTA) were incubated overnight at 4°C in white MicroFluor plates (Dynatech Laboratories). Plates were washed 3 times with PBS-EDTA with an automated plate washer and blocked with PBS-EDTA containing 1% BSA for 30 minutes. Plasma samples were diluted 1:1000 for IgM, 1:500 for total IgG, and 1:50 for IgG2 and incubated 1 hour at room temperature. Plates for IgM and IgG were incubated with an alkaline phosphatase-labeled goat anti-human IgM or IgG (Sigma) for 1 hour at room temperature. Finally, 25 µL of a 50% solution of Lumi-Phos530 (Lumigen) was added and the luminescence was determined after 90 minutes with Victor² Luminometer (Wallac, Perkin-Elmer). Plates for IgG2 were first incubated with biotin-labeled mouse anti-human IgG2 (Pharmingen), followed by alkaline phosphatase-labeled NeutrAvidin (Pierce) and LumiPhos. Triplicate determinations were performed for each plasma sample. A standard curve of human IgM or IgG and a control plasma sample was added to each plate to correct potential variations between the assays. The interassay coefficients of variation were as follows: IgM, 13.6% for CuOx-LDL and 10.0% for MDA-LDL; IgG, 11.5% for CuOx-LDL and 9.14% for MDA-LDL; and IgG2, 11.9% for CuOx-LDL and 10.3% for MDA-LDL.

Carotid Ultrasonography
The intima-media thickness and the number of the atheromatous plaques were measured by a trained radiologist without knowledge of clinical data. A duplex ultrasound system with 7.5-MHz scanning frequency in B-mode, pulsed Doppler mode, and color mode was used (Toshiba SSA-270A; Toshiba Corp). IMT, defined as the distance between the media-adventitia interface and the lumen-intima interface, was measured on the following 5 points at each side: internal carotid artery, bifurcation, and common carotid artery (at 3 different locations). The mean IMT was defined as the mean of internal carotid artery, bifurcation, and the 3 highest common carotid artery measurements. An arterial plaque was defined as an echogenic structure having an IMT more than 50% greater than those of the neighboring sites.²⁰ The reproducibility was assessed from the videotapes of 31 randomly selected study subjects by 2 radiologists blind to the original results. The intrareader variability and correlation coefficient (Pearson) were 3% and 0.97 for the mean IMT. The respective interreader variability and correlation values were 7.2% and 0.93.

Statistical Analyses
The subjects were divided into tertiles of antibodies. ANOVA was used to compare IMT and Kruskal-Wallis test was used to compare the number of plaques between the tertiles. The results were adjusted for age, gender, systolic blood pressure, LDL cholesterol, CRP, and pack-years using ANCOVA. Logarithmic transformation was used for pack-years (skewed distribution). ANOVA and ANCOVA were used to investigate the relationship between CRP and IMT. Statistical significance was defined as P<0.05. SPSS 10.1 (SPSS Inc) was used in all analyses.

	Results

Top Abstract Introduction Methods Results Discussion References

 
We first analyzed the different antibody isotype titers to OxLDL, and our data showed statistically significant differences in the IMT in the following subclasses of autoantibodies: IgM autoantibody titers to MDA-LDL and CuOx-LDL and also IgG autoantibody titers to CuOx-LDL. No trends were seen in IgG titers to MDA-LDL or IgG2 titers either to MDA-LDL or CuOx-LDL. Therefore, only IgM to MDA-LDL, IgM to CuOx-LDL, and IgG to CuOx-LDL were additionally analyzed. No statistical correlation was observed between any subclass of antibodies and the traditional risk factors for atherosclerosis (age, gender, LDL cholesterol, systolic blood pressure, or smoking). Also, medications or concomitant diseases did not have a statistically significant influence on the antibody levels.

Figure 1 shows the IMT of all the study subjects in various tertiles of IgM autoantibodies to MDA-LDL in the different parts of the carotid artery. The IMT was lowest in the highest antibody tertile in all parts of the vessel. This association remained significant after adjusting for the known risk factors of atherosclerosis (age, gender, LDL cholesterol, systolic blood pressure, CRP, and smoking) (Figure 1), although the statistical significance was not reached in every section of the artery. In addition, the calculated mean IMT was lowest in the highest antibody titer, and this difference remained statistically significant after adjusting for covariates (Figure 2). Similar results were seen in the measurements of maximal IMT and number of plaques, even though these were statistically significant only before adjusting for covariates (Figure 2).

View larger version (45K): [in this window] [in a new window]   Figure 1. IMT by tertiles of IgM antibodies to MDA-LDL in different parts of the carotid artery. Adjustment was made for age, gender, systolic blood pressure, LDL cholesterol, CRP, and pack-years.

View larger version (28K): [in this window] [in a new window]   Figure 2. Mean and maximal IMT and the number of plaques by tertiles of IgM antibodies to MDA-LDL in different parts of the carotid artery. Adjustment was made for age, gender, systolic blood pressure, LDL cholesterol, CRP, and pack-years.

Table 2 presents data of autoantibody titers to another model of oxidized LDL, CuOx-LDL. Again, the IgM autoantibody titers to CuOx-LDL and also the IgG type of autoantibodies to CuOx-LDL seemed to be negatively associated with IMT. Before adjusting for the known risk factors of atherosclerosis, the IMT was lowest in the highest tertiles of antibodies in all parts of the carotid artery. Data for the mean IMT, maximal IMT, and the number of plaques are shown in Table 2. After adjusting for other previously known risk factors, the significant differences, however, disappeared.

Finally, we measured the CRP values of the subjects. Previous studies have suggested that increased CRP values are related to increased atherosclerosis.²¹ Before the adjustment there was a positive correlation between CRP and IMT (Table 3). This correlation was seen in all segments of the vessel (data not shown), but after adjusting for the previously known risk factors, the correlation vanished in all parts of the carotid artery. Also, the linear trend toward greater number of plaques in higher tertiles of CRP disappeared after the adjustment. One previous study²² has reported a positive correlation between CPR and IgG antibodies to OxLDL. In our study, however, we found no correlation between CRP and antibody levels.

	Discussion

Top Abstract Introduction Methods Results Discussion References

 
The major finding of this study was that circulating IgM type of autoantibodies to OxLDL is inversely related to subclinical atherosclerosis determined by the IMT of the carotid artery. In addition, these antibodies remained an independent negative risk factor for increased IMT after adjusting for other major known risk factors, such as age, gender, LDL cholesterol, systolic blood pressure, CRP, and smoking.

Lipoprotein oxidation is one of the early events in atherosclerotic process. Polyunsaturated fatty acids in LDL particles undergo lipid peroxidation, forming hundreds of different kinds of oxidation products, many of which are highly reactive and additionally modify closely associated proteins and lipids.²³ These newly formed modified structures are no longer recognized as "self" structures, and, therefore, an immune response rises against them. In animal models of atherosclerosis, such as apolipoprotein E-deficient mice, autoantibodies to OxLDL have been shown to strongly correlate to measures of atherosclerosis.⁷ Autoantibodies to OxLDL have also been intensively studied in human populations, both in patients with cardiovascular disease as well as in healthy populations. One of the very earliest studies reported that the baseline titer of IgG autoantibodies to MDA-LDL predicted progression of carotid IMT in a group of 30 healthy Finnish men.¹² Since this initial report, many studies have shown a relationship between autoantibody titers to OxLDL and various cardiovascular diseases or risk factors, such as coronary artery disease, myocardial infarction, peripheral vascular disease, hypertension, preeclampsia, or diabetes.²⁴ So far, in most of the studies, the relationship between the autoantibodies to OxLDL and measures of atherosclerosis have been positive, suggesting that these antibodies could be markers of the progression of the disease or that they may even play an active role and enhance the progression of the disease. However, the results from our present study clearly demonstrate that those subjects having the highest titers of IgM type of autoantibodies binding to a classical model of OxLDL, MDA-LDL, have the lowest IMT in their carotid arteries. In the present study, we have not examined the possible underlying mechanisms for this finding. It is possible that instead of having an active role in the atherosclerotic diseases, these antibodies are merely markers. Thus, lower level of antibodies in the individuals with more extensive disease may be attributable to, for example, consumption of antibodies into the plaques. However, on the basis of the earlier studies, we may speculate that these types of antibodies may play a protective role in atherosclerosis.

There are several lines of earlier data supporting our hypothesis that there also exists a protective type of antibodies to OxLDL in vivo, and these data also provide important mechanistic insights. Several years ago, when working together with Professor Witztum’s group, we cloned natural IgM type of monoclonal autoantibodies from apolipoprotein E-deficient mice having extremely high titers of autoantibodies to a wide variety of oxidation-specific epitopes without any exogenous immunization.¹⁸ Of great interest was that most of these OxLDL-specific monoclonal autoantibodies had important biological properties, such as being able to block the binding and degradation of OxLDL by macrophages.¹⁷ Since uptake of OxLDL by macrophages and formation of foam cells is one of the key events in atherosclerosis, it suggested that these antibodies could play a protective role in vivo in atherosclerosis. In addition, because such oxidized epitopes exist on circulating LDL in vivo, these antibodies could enhance the removal of oxidatively modified lipoproteins from plasma and prevent their entrance into the arterial wall.²⁵ In the present study, both IgM (to CuOx-LDL and MDA-LDL) and IgG (to CuOx-LDL) types of antibodies were negatively associated with IMT before adjusting for confounding factors. However, it is interesting that after the adjustments, only IgM type of antibodies was inversely related to carotid atherosclerosis. We can speculate that IgG type of antibodies does not have similar blocking properties as discussed above for IgM. Instead, IgG molecules have Fc-domain, which may even enhance the uptake of OxLDL through the Fc-receptors on macrophages.

The other line of data suggesting that there exists a protective type of antibodies in vivo is the immunization studies with OxLDL. Palinski et al⁸ first reported that immunization of WHHL rabbits with MDA-LDL inhibits the progression of atherogenesis, and this finding has been confirmed with several other animal models.^9–11,26 Of special importance, a recent study by Zhou et al¹¹ demonstrated not only that immunization with MDA-LDL protected against atherosclerosis but also that the increased titers of antibodies were negatively related to the degree of lesion formation. Immunization with MDA-LDL results in a strong increase of antibodies, not only to MDA-LDL but also to a variety of other oxidative neoepitopes that may be present on OxLDL, such as oxidized phospholipids, oxidized cholesterol, oxidized cholesteryl linoleate, and oxidized cardiolipin.^10,11 Again, it can be hypothesized that high titers of antibodies to the oxidation-specific epitopes enhance formation of immune complexes with minimally modified LDL, which leads to its rapid removal from the circulation before it enters the vascular wall.

Although the general deem so far has been that high antibody titers to OxLDL are related to increased atherosclerosis, in addition to our present study, there have been few other studies suggesting the opposite.^13,27 In addition, a study by Wu et al²⁸ recently showed that autoantibodies to oxidized LDL were lower in men with borderline hypertension compared with age-matched controls. One explanation for the inconsistencies between the different studies may be because of the preparation of the antigens. The in vitro preparation of OxLDL will vary from one preparation to another within one laboratory and between different laboratories, and one main reason for this is that the isolated LDL preparations are never identical (eg, the antioxidant content). Therefore, each OxLDL preparation should be routinely tested for the degree of oxidation. However, the conditions for antigen preparation and controlling are seldom published and therefore difficult to compare. Another explanation for the inconsistencies between the different studies may be the different study populations. Atherosclerosis is a chronic inflammatory process that involves complex interplay of circulating cellular and blood elements.^2,3 High amount of OxLDL in circulation does not necessarily lead to high antibody titers to OxLDL. In fact, it has been shown that the amount of circulating OxLDL is inversely related to the antibody titers to OxLDL.²⁹ The role of the humoral immune response may vary between different patient groups as well as at different stages of the disease. In addition, certain isotypes of antibodies may possess protective properties, whereas others may be harmful. Our study sample is so far the largest population published (n=1022) where antibodies to OxLDL and the IMT have been measured. In addition, it should be emphasized that the study subjects were not selected high-risk individuals but subjects from a random population-based cohort that is a representative sample of the Finnish middle-aged population.

In this study, we found no independent role of CRP in determining IMT. CRP is strongly associated with the traditional risk factors of atherosclerosis and especially those of the metabolic syndrome.³⁰ It may therefore be a marker of increased risk for atherosclerotic diseases rather than a cause of them. Lack of association between CRP and subclinical atherosclerosis has been previously reported, assessed both with IMT³¹ and electron beam computed tomography.³² It has thus been suggested that CRP may predict the risk of cardiovascular diseases by indicating inflammation that leads to the atherothrombotic events or by directly interacting with the atherosclerotic vessels promoting inflammation and thrombosis.²¹ Our results may also support the findings of Hashimoto et al,³³ who have shown that CRP concentration is a marker of atherosclerotic activity rather than the extent of atherosclerosis.

In conclusion, experimental animal models of atherosclerosis have clearly shown that vaccination with OxLDL ameliorates atherosclerosis. We have shown that increased antibody titers to OxLDL have an independent inverse association with subclinical atherosclerosis in humans. Our present data support the recent view that induction of humoral immune response to oxidized neoepitopes may be beneficial,³⁴ and prospective studies are urgently needed to additionally assess whether these antibodies are protective in atherosclerosis in humans.

	Acknowledgments

 
This study was supported by the Research Council for Health of the Academy of Finland, the Finnish Foundation for Cardiovascular Research, the Research Foundation of Orion Corporation, the Aarne Koskelo Foundation, and the Ida Montin Foundation.

	References

Top Abstract Introduction Methods Results Discussion References

 
1. Newby AC, Libby P, van der Wal AC. Plaque instability: the real challenge for atherosclerosis research in the next decade? Cardiovasc Res. 1999; 41: 321–322.[Free Full Text]

2. Ross R. Atherosclerosis is an inflammatory disease. Am Heart J. 1999; 138: S419–S420.[CrossRef][Medline] [Order article via Infotrieve]

3. Hansson GK, Libby P, Schonbeck U, et al. Innate and adaptive immunity in the pathogenesis of atherosclerosis. Circ Res. 2002; 91: 281–291.[Abstract/Free Full Text]

4. Esterbauer H, Schaur RJ, Zollner H. Chemistry and biochemistry of 4-hydroxynonenal, malonaldehyde and related aldehydes. Free Radic Biol Med. 1991; 11: 81–128.[CrossRef][Medline] [Order article via Infotrieve]

5. Haberland ME, Fong D, Cheng L. Malondialdehyde-altered protein occurs in atheroma of Watanabe heritable hyperlipidemic rabbits. Science. 1988; 241: 215–218.[Abstract/Free Full Text]

6. Hammer A, Kager G, Dohr G, et al. Generation, characterization, and histochemical application of monoclonal antibodies selectively recognizing oxidatively modified apoB-containing serum lipoproteins. Arterioscler Thromb Vasc Biol. 1995; 15: 704–713.[Abstract/Free Full Text]

7. Palinski W, Ord VA, Plump AS, et al. 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: 605–616.[Abstract/Free Full Text]

8. 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.[Abstract/Free Full Text]

9. Ameli S, Hultgardh-Nilsson A, Regnstrom J, et al. Effect of immunization with homologous LDL and oxidized LDL on early atherosclerosis in hypercholesterolemic rabbits. Arterioscler Thromb Vasc Biol. 1996; 16: 1074–1079.[Abstract/Free Full Text]

10. Freigang S, Hörkkö S, Miller E, et al. Immunization of LDL receptor-deficient mice with homologous malondialdehyde-modified and native LDL reduces progression of atherosclerosis by mechanisms other than induction of high titers of antibodies to oxidative neoepitopes. Arterioscler Thromb Vasc Biol. 1998; 18: 1972–1982.[Abstract/Free Full Text]

11. Zhou X, Caligiuri G, Hamsten A, et al. LDL immunization induces T-cell-dependent antibody formation and protection against atherosclerosis. Arterioscler Thromb Vasc Biol. 2001; 21: 108–114.[Abstract/Free Full Text]

12. Salonen JT, Ylä-Herttuala S, Yamamoto R, et al. Autoantibody against oxidised LDL and progression of carotid atherosclerosis. Lancet. 1992; 339: 883–887.[CrossRef][Medline] [Order article via Infotrieve]

13. Hulthe J, Bokemark L, Fagerberg B. Antibodies to oxidized LDL in relation to intima-media thickness in carotid and femoral arteries in 58-year-old subjectively clinically healthy men. Arterioscler Thromb Vasc Biol. 2001; 21: 101–107.[Abstract/Free Full Text]

14. Puurunen M, Mänttäri M, Manninen V, et al. Antibody against oxidized low-density lipoprotein predicting myocardial infarction. Arch Intern Med. 1994; 154: 2605–2609.[Abstract/Free Full Text]

15. Burke GL, Evans GW, Riley WA, et al. Arterial wall thickness is associated with prevalent cardiovascular disease in middle-aged adults: the Atherosclerosis Risk in Communities (ARIC) Study. Stroke. 1995; 26: 386–391.[Abstract/Free Full Text]

16. Rantala AO, Kauma H, Lilja M, et al. Prevalence of the metabolic syndrome in drug-treated hypertensive patients and control subjects. J Intern Med. 1999; 245: 163–174.[CrossRef][Medline] [Order article via Infotrieve]

17. Hörkkö S, Bird DA, Miller E, et al. Monoclonal autoantibodies specific for oxidized phospholipids or oxidized phospholipid-protein adducts inhibit macrophage uptake of oxidized low-density lipoproteins. J Clin Invest. 1999; 103: 117–128.[Medline] [Order article via Infotrieve]

18. Palinski W, Hörkkö S, Miller E, et al. 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: 800–814.[Medline] [Order article via Infotrieve]

19. Habeeb AF. Determination of free amino groups in proteins by trinitrobenzenesulfonic acid. Anal Biochem. 1966; 14: 328–336.[CrossRef][Medline] [Order article via Infotrieve]

20. Giral P, Pithois-Merli I, Filitti V, et al. Risk factors and early extracoronary atherosclerotic plaques detected by three-site ultrasound imaging in hypercholesterolemic men: Prevention Cardio-vasculaire en Medecine du Travail METRA Group. Arch Intern Med. 1991; 151: 950–956.[Abstract/Free Full Text]

21. Lagrand WK, Visser CA, Hermens WT, et al. C-reactive protein as a cardiovascular risk factor: more than an epiphenomenon? Circulation. 1999; 100: 96–102.[Abstract/Free Full Text]

22. Hulthe J, Wikstrand J, Fagerberg B. Relationship between C-reactive protein and intima-media thickness in the carotid and femoral arteries and to antibodies against oxidized low-density lipoprotein in healthy men: the Atherosclerosis and Insulin Resistance (AIR) study. Clin Sci (Lond). 2001; 100: 371–378.[Medline] [Order article via Infotrieve]

23. Hörkkö S, Binder CJ, Shaw PX, et al. Immunological responses to oxidized LDL. Free Radic Biol Med. 2000; 28: 1771–1779.[CrossRef][Medline] [Order article via Infotrieve]

24. Ylä-Herttuala S. Is oxidized low-density lipoprotein present in vivo? Curr Opin Lipidol. 1998; 9: 337–344.[CrossRef][Medline] [Order article via Infotrieve]

25. Wiklund O, Witztum JL, Carew TE, et al. Turnover and tissue sites of degradation of glucosylated low density lipoprotein in normal and immunized rabbits. J Lipid Res. 1987; 28: 1098–1109.[Abstract]

26. George J, Afek A, Gilburd B, et al. Hyperimmunization of apo-E-deficient mice with homologous malondialdehyde low-density lipoprotein suppresses early atherogenesis. Atherosclerosis. 1998; 138: 147–152.[CrossRef][Medline] [Order article via Infotrieve]

27. Fukumoto M, Shoji T, Emoto M, et al. Antibodies against oxidized LDL and carotid artery intima-media thickness in a healthy population. Arterioscler Thromb Vasc Biol. 2000; 20: 703–707.[Abstract/Free Full Text]

28. Wu R, de Faire U, Lemne C, et al. Autoantibodies to OxLDL are decreased in individuals with borderline hypertension. Hypertension. 1999; 33: 53–59.[Abstract/Free Full Text]

29. Shoji T, Nishizawa Y, Fukumoto M, et al. Inverse relationship between circulating oxidized low density lipoprotein (oxLDL) and anti-oxLDL antibody levels in healthy subjects. Atherosclerosis. 2000; 148: 171–177.[CrossRef][Medline] [Order article via Infotrieve]

30. Fröhlich M, Imhof A, Berg G, et al. Association between C-reactive protein and features of the metabolic syndrome: a population-based study. Diabetes Care. 2000; 23: 1835–1839.[Abstract/Free Full Text]

31. Hak AE, Stehouwer CD, Bots ML, et al. Associations of C-reactive protein with measures of obesity, insulin resistance, and subclinical atherosclerosis in healthy, middle-aged women. Arterioscler Thromb Vasc Biol. 1999; 19: 1986–1991.[Abstract/Free Full Text]

32. Hunt ME, O’Malley PG, Vernalis MN, et al. C-reactive protein is not associated with the presence or extent of calcified subclinical atherosclerosis. Am Heart J. 2001; 141: 206–210.[CrossRef][Medline] [Order article via Infotrieve]

33. Hashimoto H, Kitagawa K, Hougaku H, et al. C-reactive protein is an independent predictor of the rate of increase in early carotid atherosclerosis. Circulation. 2001; 104: 63–67.[Abstract/Free Full Text]

34. Hansson GK. Vaccination against atherosclerosis: science or fiction? Circulation. 2002; 106: 1599–1601.[Free Full Text]

This article has been cited by other articles:

				M. J. Lewis, T. H. Malik, M. R. Ehrenstein, J. J. Boyle, M. Botto, and D. O. Haskard Immunoglobulin M Is Required for Protection Against Atherosclerosis in Low-Density Lipoprotein Receptor-Deficient Mice Circulation, August 4, 2009; 120(5): 417 - 426. [Abstract] [Full Text] [PDF]

				L. Garrido-Sanchez, J. M. Garcia-Almeida, S. Garcia-Serrano, I. Cardona, J. Garcia-Arnes, F. Soriguer, F. J. Tinahones, and E. Garcia-Fuentes Improved Carbohydrate Metabolism After Bariatric Surgery Raises Antioxidized LDL Antibody Levels in Morbidly Obese Patients Diabetes Care, December 1, 2008; 31(12): 2258 - 2264. [Abstract] [Full Text] [PDF]

				M. Sampi, O. Ukkola, M. Paivansalo, Y. A. Kesaniemi, C. J. Binder, and S. Horkko Plasma Interleukin-5 Levels Are Related to Antibodies Binding to Oxidized Low-Density Lipoprotein and to Decreased Subclinical Atherosclerosis J. Am. Coll. Cardiol., October 21, 2008; 52(17): 1370 - 1378. [Abstract] [Full Text] [PDF]

				S. J. Nicholls The Complex Intersection of Inflammation and Oxidation: Implications for Atheroprotection J. Am. Coll. Cardiol., October 21, 2008; 52(17): 1379 - 1380. [Full Text] [PDF]

				F. J. Tinahones, M. A. Rubio, L. Garrido-Sanchez, C. Ruiz, E. Gordillo, L. Cabrerizo, and F. Cardona Green Tea Reduces LDL Oxidability and Improves Vascular Function J. Am. Coll. Nutr., April 1, 2008; 27(2): 209 - 213. [Abstract] [Full Text] [PDF]

				C. J. Binder, K. Hartvigsen, and J. L. Witztum Promise of Immune Modulation to Inhibit Atherogenesis J. Am. Coll. Cardiol., August 7, 2007; 50(6): 547 - 550. [Full Text] [PDF]

				G. N. Fredrikson, B. Hedblad, G. Berglund, R. Alm, J.-A. Nilsson, A. Schiopu, P. K. Shah, and J. Nilsson Association Between IgM Against an Aldehyde-Modified Peptide in Apolipoprotein B-100 and Progression of Carotid Disease Stroke, May 1, 2007; 38(5): 1495 - 1500. [Abstract] [Full Text] [PDF]

				S. Tsimikas, E. S. Brilakis, R. J. Lennon, E. R. Miller, J. L. Witztum, J. P. McConnell, K. S. Kornman, and P. B. Berger Relationship of IgG and IgM autoantibodies to oxidized low density lipoprotein with coronary artery disease and cardiovascular events J. Lipid Res., February 1, 2007; 48(2): 425 - 433. [Abstract] [Full Text] [PDF]

				S. G. Tsouli, D. N. Kiortsis, V. Xydis, M. I. Argyropoulou, M. Elisaf, and A. D. Tselepis Antibodies Against Various Forms of Mildly Oxidized Low-Density Lipoprotein Are Not Associated With Carotid Intima-Media Thickness in Patients With Primary Hyperlipidemia Angiology, October 1, 2006; 57(5): 615 - 622. [Abstract] [PDF]

				G. N. Fredrikson, G. Berglund, R. Alm, J.-A. Nilsson, P. K. Shah, and J. Nilsson Identification of autoantibodies in human plasma recognizing an apoB-100 LDL receptor binding site peptide J. Lipid Res., September 1, 2006; 47(9): 2049 - 2054. [Abstract] [Full Text] [PDF]

				M. Mayr, S. Kiechl, S. Tsimikas, E. Miller, J. Sheldon, J. Willeit, J. L. Witztum, and Q. Xu Oxidized Low-Density Lipoprotein Autoantibodies, Chronic Infections, and Carotid Atherosclerosis in a Population-Based Study J. Am. Coll. Cardiol., June 20, 2006; 47(12): 2436 - 2443. [Abstract] [Full Text] [PDF]

				S. Tsimikas, S. Kiechl, J. Willeit, M. Mayr, E. R. Miller, F. Kronenberg, Q. Xu, C. Bergmark, S. Weger, F. Oberhollenzer, et al. Oxidized Phospholipids Predict the Presence and Progression of Carotid and Femoral Atherosclerosis and Symptomatic Cardiovascular Disease: Five-Year Prospective Results From the Bruneck Study J. Am. Coll. Cardiol., June 6, 2006; 47(11): 2219 - 2228. [Abstract] [Full Text] [PDF]

				J. Rodenburg, M. N. Vissers, A. Wiegman, E. R. Miller, P. M. Ridker, J. L. Witztum, J. J.P. Kastelein, and S. Tsimikas Oxidized Low-Density Lipoprotein in Children With Familial Hypercholesterolemia and Unaffected Siblings: Effect of Pravastatin J. Am. Coll. Cardiol., May 2, 2006; 47(9): 1803 - 1810. [Abstract] [Full Text] [PDF]

				J. Frostegard Atherosclerosis in Patients With Autoimmune Disorders Arterioscler Thromb Vasc Biol, September 1, 2005; 25(9): 1776 - 1785. [Abstract] [Full Text] [PDF]

				C. J. Binder, P. X. Shaw, M.-K. Chang, A. Boullier, K. Hartvigsen, S. Horkko, Y. I. Miller, D. A. Woelkers, M. Corr, and J. L. Witztum Thematic review series: The Immune System and Atherogenesis. The role of natural antibodies in atherogenesis J. Lipid Res., July 1, 2005; 46(7): 1353 - 1363. [Abstract] [Full Text] [PDF]

				I. Goncalves, M.-L. M. Gronholdt, I. Soderberg, M. P.S. Ares, B. G. Nordestgaard, J. F. Bentzon, G. N. Fredrikson, and J. Nilsson Humoral Immune Response Against Defined Oxidized Low-Density Lipoprotein Antigens Reflects Structure and Disease Activity of Carotid Plaques Arterioscler Thromb Vasc Biol, June 1, 2005; 25(6): 1250 - 1255. [Abstract] [Full Text] [PDF]

				P A J Krijnen, C Ciurana, T Cramer, T Hazes, C J L M Meijer, C A Visser, H W M Niessen, and C E Hack IgM colocalises with complement and C reactive protein in infarcted human myocardium J. Clin. Pathol., April 1, 2005; 58(4): 382 - 388. [Abstract] [Full Text] [PDF]

				F. J. Tinahones, J. M. Gomez-Zumaquero, L. Garrido-Sanchez, E. Garcia-Fuentes, G. Rojo-Martinez, I. Esteva, M. S. R. de Adana, F. Cardona, and F. Soriguer Influence of age and sex on levels of anti-oxidized LDL antibodies and anti-LDL immune complexes in the general population J. Lipid Res., March 1, 2005; 46(3): 452 - 457. [Abstract] [Full Text] [PDF]

				Y. Shoenfeld, R. Wu, L. D. Dearing, and E. Matsuura Are Anti-Oxidized Low-Density Lipoprotein Antibodies Pathogenic or Protective? Circulation, October 26, 2004; 110(17): 2552 - 2558. [Full Text] [PDF]

				M. Schneider, B. Verges, A. Klein, E. R. Miller, V. Deckert, C. Desrumaux, D. Masson, P. Gambert, J.-M. Brun, J. Fruchart-Najib, et al. Alterations in Plasma Vitamin E Distribution in Type 2 Diabetic Patients With Elevated Plasma Phospholipid Transfer Protein Activity Diabetes, October 1, 2004; 53(10): 2633 - 2639. [Abstract] [Full Text] [PDF]

				S. Tsimikas, J. L. Witztum, E. R. Miller, W. J. Sasiela, M. Szarek, A. G. Olsson, G. G. Schwartz, and for the Myocardial Ischemia Reduction with Aggress High-Dose Atorvastatin Reduces Total Plasma Levels of Oxidized Phospholipids and Immune Complexes Present on Apolipoprotein B-100 in Patients With Acute Coronary Syndromes in the MIRACL Trial Circulation, September 14, 2004; 110(11): 1406 - 1412. [Abstract] [Full Text] [PDF]

This Article Abstract Full Text (PDF) All Versions of this Article: 108/17/2107    most recent 01.CIR.0000092891.55157.A7v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Karvonen, J. Articles by Hörkkö, S. Search for Related Content PubMed PubMed Citation Articles by Karvonen, J. Articles by Hörkkö, S. Related Collections Pathophysiology