Plasma variation and reproducibility of oxidized LDL-cholesterol and low-grade inflammation biomarkers among participants of the Malmö Diet and Cancer cohort.

CONTEXT: Large epidemiological studies often collect non-fasting samples, although the reliability of biomarkers may be uncertain. OBJECTIVE: To explore the reliability and reproducibility of a single measurement of selected biomarkers in a sub-sample of the Malmö Diet and Cancer cohort. METHODS: We estimated single- and average-measures intraclass correlation coefficients (ICC) for oxidized (ox)-LDL, interleukin (IL)-1ß, IL-6, IL-8 and TNF-α. RESULTS: Single-measures ICC in non-fasting samples of ox-LDL, IL-1ß, IL-6, IL-8 and TNF-α were the following: 0.85, 0.71, 0.61, 0.78 and 0.66 for men, and 0.67, 0.81, 0.87, 0.69 and 0.81 for women. Biomarkers at non-fasting and fasting samples were highly correlated (all r > 0.80). CONCLUSIONS: The observed ICC suggest that most of the examined biomarkers (non-fasting blood) would allow meaningful analysis in epidemiological studies.

Apolipoprotein B-100 Antibody Interaction With Atherosclerotic Plaque Inflammation and Repair Processes.

BACKGROUND AND PURPOSE: Treatment with IgG against the malondialdehyde (MDA)-modified apolipoprotein B-100 epitope p45 reduces atherosclerosis in experimental models. This study investigated the association between p45 IgG autoantibodies and plaque inflammation in subjects with advanced cardiovascular disease. METHODS: Native and MDA-p45 IgG levels were analyzed by ELISA in 349 carotid endarterectomy patients. In a subcohort of 195 subjects, endarterectomy samples were analyzed by immunohistochemistry and ELISA to determine plaque constituents and inflammation. Peripheral blood mononuclear cells were isolated from healthy donors. RESULTS: Patients with preoperative events of neurological ischemia had lower levels of native p45 IgG. Low levels of MDA-p45 IgG were associated with increased risk of postoperative cardiovascular death during a mean follow-up of 54 months. High plasma levels of native p45 IgG were associated with increased plaque content of collagen and smooth muscle cell growth factors, as well as with lower levels of proinflammatory cytokines. Exposure of peripheral blood mononuclear cells from healthy donors to recombinant MDA-p45 IgG in presence of oxidized low-density lipoprotein reduced the expression of tumor necrosis factor-α and stimulated release of smooth muscle cell growth factors. CONCLUSIONS: This study confirms previous experimental findings of anti-inflammatory properties of apolipoprotein B-100 p45 antibodies and provides the first clinical evidence of associations between p45 IgG autoantibody levels and atherosclerotic plaque inflammation, plaque repair as well as prevalent and incident cardiovascular events in carotid endarterectomy patients. These findings suggest the possibility that treatment with anti-p45 antibodies may have beneficial effects in advanced cardiovascular disease.

Low Levels of Apolipoprotein B-100 Autoantibodies Are Associated With Increased Risk of Coronary Events.

OBJECTIVE: Previous smaller studies have indicated inverse associations between autoantibodies to oxidized low-density lipoprotein epitopes, and cardiovascular disease. The present study investigated associations between autoantibodies against the apolipoprotein B-100 peptides p45 and p210, respectively, and risk of incident cardiovascular disease in a large population-based cohort. APPROACH AND RESULTS: Apolipoprotein B-100 autoantibodies were analyzed by ELISA in a prospective study, including 5393 individuals (aged 46-68 years) belonging to the cardiovascular arm of the Malmö Diet and Cancer study with a follow-up time of >15 years. Subjects that suffered an acute coronary event during follow-up (n=382) had lower levels at baseline of IgM autoantibodies recognizing the native and malondialdehyde-modified apolipoprotein B-100 peptides p45 and p210 and also lower IgG levels recognizing native p210, whereas no association was found with risk for stroke (n=317). Subjects in the highest compared with lowest tertile of IgM-p45MDA (hazard ratio [95% confidence interval]: 0.72 [0.55, 0.94]; P=0.017) and IgG-p210native (hazard ratio [95% confidence interval]: 0.73 [0.56, 0.97]; P=0.029) had lower risk for incident coronary events after adjustment for cardiovascular risk factors in Cox proportional hazard regression models. Moreover, subjects with high levels of IgG-p210native were less likely to have carotid plaques as assessed by ultrasonography at baseline (odds ratio=0.81, 95% confidence interval 0.70-0.95, P=0.008 after adjustment for risk factors). CONCLUSIONS: This large prospective study demonstrates that subjects with high levels of apolipoprotein B-100 autoantibodies have a lower risk of coronary events supporting a protective role of these autoantibodies in cardiovascular disease.

Low Levels of IgM Antibodies against an Advanced Glycation Endproduct-Modified Apolipoprotein B100 Peptide Predict Cardiovascular Events in Nondiabetic Subjects.

Increased glucose levels are associated with the generation of advanced glycation endproduct (AGE) modifications. Interaction between AGE-modified plaque components and immune cells is believed to have an important role in the development of vascular complications in diabetes. Methylglyoxal (MGO) is one type of reactive aldehyde that gives rise to AGE modification. The present study analyzed whether autoantibodies against MGO-modified epitopes of the low-density lipoprotein apolipoprotein B (apoB) 100 predict cardiovascular events. A library consisting of 302 peptides comprising the complete apoB100 molecule was screened to identify peptides targeted by MGO-specific autoantibodies. Peptide (p) 220 (apoB amino acids 3286-3305) was identified as a major target. Baseline IgM and IgG against MGO-peptide 220 (p220) were measured in 700 individuals from the Malmö Diet and Cancer Cohort. A total of 139 cardiovascular events were registered during the 15-y follow-up period. Controlling for major cardiovascular risk factors demonstrated that subjects in the lowest tertile of MGO-p220 IgM had an increased risk for cardiovascular events (hazard ratio [95% confidence interval]: 2.07 [1.22-3.50]; p(trend) = 0.004). Interestingly, the association between MGO-p220 IgM and cardiovascular events remained and even tended to become stronger when subjects with prevalent diabetes were excluded from the analysis (2.51 [1.37-4.61]; p(trend) = 0.002). MGO-p220 IgM was inversely associated with blood glucose, but not with oxidized low-density lipoprotein. Finally, we demonstrate that anti-MGO-p220 IgM is produced by B1 cells. These data show that subjects with low levels of IgM recognizing MGO-modified p220 in apoB have an increased risk to develop cardiovascular events and that this association is present in nondiabetic subjects.

Low levels of IgG autoantibodies against the apolipoprotein B antigen p210 increases the risk of cardiovascular death after carotid endarterectomy.

OBJECTIVES: Autoimmune responses against oxidized-LDL (oxLDL) have been suggested to modulate inflammation in atherosclerosis. Previous studies showed an association between autoantibodies against the apolipoprotein B (apoB) p210 antigen and a lower risk of cardiovascular (CV) events. In the present study we investigated if autoantibodies against p210 at the time of carotid endarterectomy (CEA) predict risk for future CV events. METHODS: Native (nat) and malondialdehyde (MDA)-modified apoB p210 autoantibodies (IgM-p210nat, IgG-p210nat, IgM-p210MDA and IgG-p210MDA) were analyzed by ELISA from plasma samples of 351 patients at the time they underwent CEA. The incidence of postoperative CV events was assessed using national registers. RESULTS: A total of 52 non-fatal and 15 fatal CV events were registered during the follow-up period (35.1 ± 16.7 months). Patients who suffered from a fatal CV event had significantly lower plasma levels of IgG-p210nat and IgG-p210MDA. Kaplan-Meier curves of event-free survival showed increased CV mortality in patients with levels of IgG-p210nat and IgG-p210MDA below the median (Log Rank 7.813, p .005 and 9.105, p .003 respectively). The association between low levels of p210 IgG and fatal post-operative CV events remained significant when adjusting for age, sex, total cholesterol, HDL cholesterol, smoking habits and hypertension in a Cox Proportional Hazard model (hazard ratios (HR) IgG-p210nat below median: HR 6.7 (95% C.I. 1.5-30.6, p .013) and IgG-p210MDA below median: HR 7.8 (95% C.I. 1.7-35.5, p .008). CONCLUSIONS: The present findings support the notion that autoantibodies against LDL antigens are involved in the atherosclerotic disease process and suggest that CEA patients with low levels of IgG-p210nat and IgG-p210MDA have an increased risk of post-operative CV death.

Circulating CD40+ and CD86+ B cell subsets demonstrate opposing associations with risk of stroke.

OBJECTIVE: Accumulating evidence shows that immune cells play an important role in atherosclerosis. Most attention has focused on the role of different T cell subsets, whereas the possible involvement of B cells has been less studied. In this study, we assessed the association of 2 different B cell subsets, CD19(+)CD40(+) and CD19(+)CD86(+) B cells, with risk for development of acute cardiovascular events. APPROACH AND RESULTS: The prospective study included 700 subjects randomly selected from the cardiovascular cohort of the Malmö Diet and Cancer study. Mononuclear leukocytes, stored at -140(○)C at the baseline investigation in 1991-1994, were thawed and B cell subsets analyzed by flow cytometry. Cytokine release from CD3/CD28-stimulated mononuclear leukocytes was measured with multiplex ELISA. Baseline carotid intima-media thickness and stenosis were assessed by ultrasonography, and clinical events were monitored through validated national registers during a median/mean follow-up time of 15 years. The subjects in the highest tertile of CD19(+)CD40(+) B cells had a significantly lower risk of incident stroke after adjustment for other risk factors. In contrast, CD19(+)CD86(+) B cells were associated with higher risk for development of a stroke event and increased release of proinflammatory cytokines from mononuclear leukocytes. CONCLUSIONS: These observations provide evidence for an involvement of B cells in the incidence of stroke and suggest that both pathogenic and protective B cell subsets exist.

Antibodies against gonadotropin-releasing hormone (GnRH) in patients with diabetes mellitus is associated with lower body weight and autonomic neuropathy.

BACKGROUND: Esophageal dysmotility and gastroparesis are common secondary complications in patients with diabetes mellitus. Patients with dysmotility express antibodies against gonadotropin-releasing hormone (GnRH) in serum. The aim of the present study was to scrutinize patients with diabetes mellitus with regard to the presence of GnRH antibodies, and to examine associations between antibodies and clinical findings. RESULTS: Thirty-nine consecutive patients with diabetes mellitus were included in the study after clinical examination and examination by esophageal manometry and gastric emptying scintigraphy. Serum was analyzed for the presence of antibodies against GnRH using an ELISA, and values are expressed as relative units (RU). Two age- and gender-matched healthy subjects per each patient served as controls. The prevalence of IgM GnRH antibodies in patients was 33% compared to 14% in controls (p = 0.027), with a higher antibody titer; 1.2 (0.6-5.0) and 0.2 (0.1-0.3) RU, respectively (p = 0.000). The expression of IgG antibodies was 15% in patients and none in controls (p = 0.000). Lower body mass index was associated with the presence of IgM antibodies (OR = 0.835, 95% CI = 0.699-0.998), and autonomic neuropathy with the presence IgG antibodies (OR = 9.000, 95% CI = 1.327-61.025). Esophageal dysmotility (69%) or gastroparesis (18%) were not associated with the presence of IgM antibodies (OR = 0.589, 95% CI = 0.143-2.424 and OR = 3.407, 95% CI = 0.633-18.350, respectively). Neither was esophageal dysmotility associated with IgG antibodies (OR = 2.500, 95% CI = 0.259-24.096). CONCLUSIONS: Antibodies against GnRH are more common in patients with diabetes mellitus compared with healthy controls. IgM antibodies are associated with lower body mass index and IgG antibodies are associated with autonomic neuropathy.

Gonadotropin-releasing hormone analog buserelin causes neuronal loss in rat gastrointestinal tract.

Gonadotropin-releasing hormone (GnRH) analogs are given to women undergoing in vitro fertilization. Case reports describing the development of chronic intestinal pseudo-obstruction and auto-antibodies against GnRH after such treatment suggest a strong association between intestinal dysfunction and GnRH analogs. No experimental model for studying such a relationship is currently at hand. Our main goal was to investigate possible enteric neurodegeneration and titers of GnRH antibodies in response to repeated administration of the GnRH analog buserelin in rat. Rats were treated for 1-4 sessions with daily subcutaneous injections of buserelin or saline for 5 days, followed by 3 weeks of recovery. Buserelin treatment caused significant loss of submucous and myenteric neurons in the fundus, ileum, and colon. The loss of enteric neurons can, at least partly, be explained by increased apoptosis. No GnRH- or GnRH-receptor-immunoreactive (IR) enteric neurons but numerous luteinizing hormone (LH)-receptor-IR neurons were detected. After buserelin treatment, the relative number of enteric LH-receptor-IR neurons decreased, whereas that of nitric-oxide-synthase-IR neurons increased. No intestinal inflammation or increased levels of circulating interleukins/cytokines were noted in response to buserelin treatment. Serum GnRH antibody titers were undetectable or extremely low in all rats. Thus, repeated administrations of buserelin induce neurodegeneration in rat gastrointestinal tract, possibly by way of LH-receptor hyperactivation. The present findings suggest that enteric neurodegenerative effects of GnRH analog treatment in man can be mimicked in rat. However, in contrast to man, no production of GnRH auto-antibodies has been noted in rat.

Depletion of enteric gonadotropin-releasing hormone is found in a few patients suffering from severe gastrointestinal dysmotility.

OBJECTIVE: Many patients, especially women, suffer from severe gastrointestinal pain and dysmotility for several years without being diagnosed. Depletion of gonadotropin-releasing hormone (GnRH) in the enteric nervous system (ENS) has been described in some patients. The aim of this study was to examine the expression of GnRH in ENS and antibodies against GnRH in serum, in a dysmotility patient cohort of southern Sweden. MATERIALS AND METHODS: All consecutive patients (n = 35) referred for laparoscopic full-thickness biopsy because of symptoms or signs of severe dysmotility between 1998 and 2009, or patients with a severe dysmotility disorder having had a bowel resection within the time frame, were considered for inclusion. In 22 cases, representative biopsy material containing ganglia was available, and these patients were included. Medical records were scrutinized. The expression of GnRH was determined by immunohistochemistry in bowel biopsies from these patients and in patients with carcinoma or diverticulosis without ENS histopathology. Antibodies against GnRH in serum were determined by ELISA in patients and controls. RESULTS: 14 patients were diagnosed with enteric dysmotility (ED) and 8 with chronic intestinal pseudo-obstruction due to varying etiology. Immunostained biopsies showed expression of GnRH in the ENS. A reduced expression of GnRH-containing neurons was found in 5 patients, as well as antibodies against GnRH in serum. 3 of these patients had a history of in vitro fertilization (IVF) using GnRH analogs. CONCLUSIONS: A subgroup of patients with severe dysmotility had a reduced expression of GnRH-containing neurons in the ENS and expressed antibodies against GnRH in serum.

TAP1-deficiency does not alter atherosclerosis development in Apoe-/- mice.

Antigen presenting cells (APC) have the ability to present both extra-cellular and intra-cellular antigens via MHC class I molecules to CD8(+) T cells. The cross presentation of extra-cellular antigens is reduced in mice with deficient Antigen Peptide Transporter 1 (TAP1)-dependent MHC class I antigen presentation, and these mice are characterized by a diminished CD8(+) T cell population. We have recently reported an increased activation of CD8(+) T cells in hypercholesterolemic Apoe(-/-) mice. Therefore, this study included TAP1-deficient Apoe(-/-) mice (Apoe(-/-)Tap1(-/-)) to test the atherogenicity of CD8(+) T cells and TAP1-dependent cross presentation in a hypercholesterolemic environment. As expected the CD8(+) T cell numbers were low in Apoe(-/-)Tap1(-/-) mice in comparison to Apoe(-/-) mice, constituting ~1% of the lymphocyte population. In spite of this there were no differences in the extent of atherosclerosis as assessed by en face Oil Red O staining of the aorta and cross-sections of the aortic root between Apoe(-/-)Tap1(-/-) and Apoe(-/-) mice. Moreover, no differences were detected in lesion infiltration of macrophages or CD3(+) T cells in Apoe(-/-)Tap1(-/-) compared to Apoe(-/-) mice. The CD3(+)CD4(+) T cell fraction was increased in Apoe(-/-)Tap1(-/-) mice, suggesting a compensation for the decreased CD8(+) T cell population. Interestingly, the fraction of CD8(+) effector memory T cells was increased but this appeared to have little impact on the atherosclerosis development.In conclusion, Apoe(-/-)Tap1(-/-) mice develop atherosclerosis equal to Apoe(-/-) mice, indicating a minor role for CD8(+) T cells and TAP1-dependent antigen presentation in the disease process.

Immunization with cationized BSA inhibits progression of disease in ApoBec-1/LDL receptor deficient mice with manifest atherosclerosis.

Immune responses against modified self-antigens generated by hypercholesterolemia play an important role in atherosclerosis identifying the immune system as a possible novel target for prevention and treatment of cardiovascular disease. It has recently been shown that these immune responses can be modulated by subcutaneous injection of adjuvant. In the present study we immunized 25-week old ApoBec-1/LDL receptor deficient mice with manifest atherosclerosis with adjuvant and two different concentrations of the carrier molecule cationized BSA (cBSA). Plasma levels of Th2-induced apolipoprotein B (apoB)/IgG1 immune complexes were increased in the cBSA immunized groups verifying induction of immunity against a self-antigen. Mice were sacrificed at 36 weeks of age and atherosclerosis was monitored by en face Oil red O staining of the aorta. Immunization with 100 µg cBSA inhibited plaque progression, whereas the lower dose (50 µg) did not. In addition, the higher dose induced a more stable plaque phenotype, indicated by a higher content of collagen and less macrophages and T cells in the plaques. Moreover, there was an increased ratio of Foxp3+/Foxp3⁻ T cells in the circulation suggesting activation of a regulatory T cell response. In conclusion, we show that immunization with cBSA induces an immune response against apoB as well as an activation of Treg cells. This was associated with development of a more stable plaque phenotype and reduced atherosclerosis progression.

Association between IgM against an aldehyde-modified peptide in apolipoprotein B-100 and progression of carotid disease.

BACKGROUND AND PURPOSE: Autoantibodies against antigens in oxidized low-density lipoprotein are common in people; experimental studies suggest that these immune responses have a functional role in the disease process. The aim of this study was to evaluate the relationship between the immune response against one defined oxidized low-density lipoprotein antigen, the aldehyde-modified peptide corresponding amino acids 3136 and 3155 (MDA-p210) in apolipoprotein (apo) B-100, and progression of carotid intima media thickness (IMT). METHODS: IgM and IgG against MDA-p210 were determined by enzyme-linked immunosorbent assay at baseline and after 12 months of treatment with placebo, metoprolol, fluvastatin, or metoprolol/fluvastatin in 751 individuals participating in the BCAPS. Carotid IMT was assessed by ultrasonography at baseline and after 18 and 36 months of treatment. RESULTS: Antibody levels did not change in response to treatment, but high baseline MDA-p210 IgM levels were associated with a more rapid progression of carotid disease both at 18 (r=0.09, P<0.05) and 36 months (r=0.12, P<0.005). At 36 months, the difference in IMT progression rate per year between those with high MDA-p210 IgM levels and those with low was 0.011 mm (95% CI=0.005 to 0.018 mm, P<0.0001). Treatment with fluvastatin markedly decreased the progression of IMT among subjects with high but not with low MDA-p210 IgM levels. There was no association between MDA-p210 IgG and carotid IMT progression. CONCLUSIONS: IgM against the aldehyde-modified peptide corresponding amino acids 3136 and 3155 in apo B-100 is common in subjects with asymptomatic carotid disease, and high levels are associated with a more rapid progression of carotid IMT. The observation that the effect of fluvastatin was restricted to subjects with high MDA-p210 IgM levels may reflect the increased rate of disease progression in this group.

Autoantibody against the amino acid sequence 661-680 in apo B-100 is associated with decreased carotid stenosis and cardiovascular events.

Immunization with malondialdehyde (MDA)-modified peptides corresponding to the amino acid sequence between 661 and 680 in apo B-100 (p45) inhibits atherosclerosis in apo E knockout mice. The same effect can be obtained by treating the mice with recombinant anti-MDA-p45 IgG, suggesting that these antibodies have atheroprotective effects. In the present study we analyzed if autoantibodies against p45 and MDA-p45 are related to carotid atherosclerosis and acute cardiovascular events in humans. Using a nested case control design we determined plasma levels of IgG recognizing native and MDA-modified p45 in baseline samples from 75 subjects with acute myocardial infarction or sudden cardiac death and 148 matched controls. The control group was found to have significantly higher levels of p45 IgG than the cases. Moreover, an independent association was found between high levels of MDA-p45 IgG and a low degree of carotid stenosis (P=0.006). There was a high degree of co-variation between IgG binding to native p45 and MDA-p45 (r=0.68, P<0.0001). The associations between lower levels of autoantibodies against the apo B-100 p45 sequence and cardiovascular disease are in agreement with previous experimental studies demonstrating that these antibodies have atheroprotective effects. Our findings support the notion that the p45 sequence of apo B-100 is a potential target for immunomodulatory treatment of atherosclerosis in humans.

Identification of autoantibodies in human plasma recognizing an apoB-100 LDL receptor binding site peptide.

The aim of this study was to test the hypothesis that autoantibodies recognize amino acid sequences in the LDL receptor binding region of apolipoprotein B-100 (apoB-100). Autoantibodies against an unmodified or malondialdehyde (MDA)-modified LDL receptor binding site peptide were determined by ELISA in baseline plasma samples of 78 cases with coronary events and 149 matched controls recruited from the prospective Malmö Diet Cancer Study. IgG and IgM recognizing this peptide were detected in all subjects but did not differ between cases and controls. Inverse associations were observed between IgG against the native binding site and plasma oxidized LDL (r = -0.21, P < 0.005), but there were no significant associations with total or LDL cholesterol levels. In univariate analyses, inverse associations were found between baseline carotid intima-media thickness and IgG against the MDA-modified binding site (r = -0.14, P < 0.05), but this association was lost when controlling for other major cardiovascular risk factors. Specificity studies demonstrated that the binding of autoantibodies to these sequences could be inhibited by oxidized but not by native LDL. Autoantibodies recognizing the LDL receptor binding site in apoB-100 are frequently expressed. Their association with plasma oxidized LDL suggests that they have been generated in response to breakdown products of LDL oxidation, but their influence on cholesterol metabolism and the development of atherosclerosis appears limited.

Association between diet, lifestyle, metabolic cardiovascular risk factors, and plasma C-reactive protein levels.

Increased C-reactive protein (CRP) levels have been associated with several of the components of the metabolic syndrome, but the direct influence of diet and lifestyle factors on CRP levels remains largely unknown. The purpose of the present study was to investigate the association between CRP and diet and lifestyle factors. Plasma CRP levels were determined by a highly sensitive enzyme-linked immunosorbent assay (ELISA) in 760 participants in the beta-Blocker Cholesterol-Lowering Asymptomatic Plaque Study (BCAPS). In accordance with previous findings, increased levels of CRP were associated with high body mass index (BMI) (P = .012), triglycerides (P = .001), systolic blood pressure (P = .019), cholesterol/high-density lipoprotein (HDL) ratio (P = .009), and low HDL cholesterol (P = .001). CRP was also increased in smokers (P = .023) and in subjects with a low vitamin C intake (P = .018). When men and women were analyzed together, there were no significant associations between CRP and dietary intake of total calories, total fat, saturated fat, monounsaturated fat, polyunsaturated fat, n-3 polyunsaturated fatty acids, n-6 polyunsaturated fatty acids, fiber, vitamin E, carotene, or selen, or in physical activity. However, in the female subgroup weak inverse relations were observed between CRP and the intake of total fat (r = -0.13, P = .011), saturated fat (r = -0.13, P = .011), monounsaturated fat (r = -0.13, P = .010), polyunsaturated fat (r = -0.14, P = .007), and n-3 PUFA (r = -0.14, P = .004). Stratified factor analyses in smoking subgroups, obese, and in under-reporters of energy, largely confirmed the results although in male never-smokers a combination of high fiber vitamin C/beta carotene intake was associated with low CRP levels. These observations suggest that CRP levels are only marginally associated with individual dietary and lifestyle factors. Surprisingly, a higher intake of fat tended to be associated with lower CRP values among women.

Identification of immune responses against aldehyde-modified peptide sequences in apoB associated with cardiovascular disease.

OBJECTIVE: Atherosclerosis is associated with an immune response against oxidized LDL, which modulates the progression of the disease process. METHODS AND RESULTS: Using a library of polypeptides covering the complete sequence of apoB-100, the only major protein of LDL, we have identified over 100 different human antibodies reacting against aldehyde-modified apoB-100 sequences. IgM antibody titer levels decreased with age and were associated with the intima-media thickness of the carotid artery in subjects younger than 60 years. There were also inverse associations between IgM levels and oxidized LDL in plasma. In prospective clinical studies, antibody levels against several aldehyde-modified apoB-100 sites were associated with cardiovascular disease in this age group. Whether this immune response is adaptive (protective) or maladaptive (causal) in atherosclerosis requires further investigation. CONCLUSIONS: We have characterized a large number of epitopes within the apoB-100 component of oxidized LDL that provoke an immune response in humans. These findings will make it possible to study the role of immune responses against specific sites in oxidized LDL and to determine whether these immune responses influence the risk for future cardiac events.