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Autoimmune diseases are associated with a dramatically increased risk of atherosclerotic cardiovascular disease and its clinical manifestations. The increased risk is consistent with the notion that atherogenesis is modulated by both protective and disease-promoting immune mechanisms. Notably, traditional cardiovascular risk factors such as dyslipidaemia and hypertension alone do not explain the increased risk of cardiovascular disease associated with autoimmune diseases. Several mechanisms have been implicated in mediating the autoimmunity-associated cardiovascular risk, either directly or by modulating the effect of other risk factors in a complex interplay. Aberrant leukocyte function and pro-inflammatory cytokines are central to both disease entities, resulting in vascular dysfunction, impaired resolution of inflammation and promotion of chronic inflammation. Similarly, loss of tolerance to self-antigens and the generation of autoantibodies are key features of autoimmunity but are also implicated in the maladaptive inflammatory response during atherosclerotic cardiovascular disease. Therefore, immunomodulatory therapies are potential efficacious interventions to directly reduce the risk of cardiovascular disease, and biomarkers of autoimmune disease activity could be relevant tools to stratify patients with autoimmunity according to their cardiovascular risk. In this Review, we discuss the pathophysiological aspects of the increased cardiovascular risk associated with autoimmunity and highlight the many open questions that need to be answered to develop novel therapies that specifically address this unmet clinical need.

BackgroundSerological tests are widely used in various medical disciplines for diagnostic and monitoring purposes. Unfortunately, the sensitivity and specificity of test systems are often poor, leaving room for false-positive and false-negative results. However, conventional methods were used to increase specificity and decrease sensitivity and vice versa. Using SARS-CoV-2 serology as an example, we propose here a novel testing strategy: the ‘sensitivity improved two-test’ or ‘SIT²’ algorithm.MethodsSIT² involves confirmatory retesting of samples with results falling in a predefined retesting zone of an initial screening test, with adjusted cut-offs to increase sensitivity. We verified and compared the performance of SIT² to single tests and orthogonal testing (OTA) in an Austrian cohort (1117 negative, 64 post-COVID-positive samples) and validated the algorithm in an independent British cohort (976 negatives and 536 positives).ResultsThe specificity of SIT² was superior to single tests and non-inferior to OTA. The sensitivity was maintained or even improved using SIT² when compared with single tests or OTA. SIT² allowed correct identification of infected individuals even when a live virus neutralisation assay could not detect antibodies. Compared with single testing or OTA, SIT² significantly reduced total test errors to 0.46% (0.24–0.65) or 1.60% (0.94–2.38) at both 5% or 20% seroprevalence.ConclusionFor SARS-CoV-2 serology, SIT² proved to be the best diagnostic choice at both 5% and 20% seroprevalence in all tested scenarios. It is an easy to apply algorithm and can potentially be helpful for the serology of other infectious diseases.

Thrombosis and its associated complications are a major cause of morbidity and mortality worldwide. Microvesicles (MVs), a class of extracellular vesicles, are increasingly recognized as mediators of coagulation and biomarkers of thrombotic risk. Thus, identifying factors targeting MV-driven coagulation may help in the development of novel antithrombotic treatments. We have previously identified a subset of circulating MVs that is characterized by the presence of oxidation-specific epitopes and bound by natural immunoglobulin M (IgM) antibodies targeting these structures. This study investigated whether natural IgM antibodies, which are known to have important anti-inflammatory housekeeping functions, inhibit the procoagulatory properties of MVs. We found that the extent of plasma coagulation is inversely associated with the levels of both free and MV-bound endogenous IgM. Moreover, the oxidation epitope-specific natural IgM antibody LR04, which recognizes malondialdehyde adducts, reduced MV-dependent plasmatic coagulation and whole blood clotting without affecting thrombocyte aggregation. Intravenous injection of LR04 protected mice from MV-induced pulmonary thrombosis. Of note, LR04 competed the binding of coagulation factor X/Xa to MVs, providing a mechanistic explanation for its anticoagulatory effect. Thus, our data identify natural IgM antibodies as hitherto unknown modulators of MV-induced coagulation in vitro and in vivo and their prognostic and therapeutic potential in the management of thrombosis.

Atherosclerotic cardiovascular disease causes heart attacks and strokes, which are the leading causes of mortality worldwide1. The formation of atherosclerotic plaques is initiated when low-density lipoproteins bind to heparan-sulfate proteoglycans (HSPGs)2and become trapped in the subendothelial space of large and medium size arteries, which leads to chronic inflammation and remodelling of the artery wall2. A proliferation-inducing ligand (APRIL) is a cytokine that binds to HSPGs3, but the physiology of this interaction is largely unknown. Here we show that genetic ablation or antibody-mediated depletion of APRIL aggravates atherosclerosis in mice. Mechanistically, we demonstrate that APRIL confers atheroprotection by binding to heparan sulfate chains of heparan-sulfate proteoglycan 2 (HSPG2), which limits the retention of low-density lipoproteins, accumulation of macrophages and formation of necrotic cores. Indeed, antibody-mediated depletion of APRIL in mice expressing heparan sulfate-deficient HSPG2 had no effect on the development of atherosclerosis. Treatment with a specific anti-APRIL antibody that promotes the binding of APRIL to HSPGs reduced experimental atherosclerosis. Furthermore, the serum levels of a form of human APRIL protein that binds to HSPGs, which we termed non-canonical APRIL (nc-APRIL), are associated independently of traditional risk factors with long-term cardiovascular mortality in patients with atherosclerosis. Our data reveal properties of APRIL that have broad pathophysiological implications for vascular homeostasis.

IgM antibodies have gained much attention as risk markers of atherosclerotic cardiovascular disease, but the exact antigenic determinants and the full spectrum of functions remain to be defined. A better understanding of the potentially diverse nature of the antigens that they recognize will help to dissect the function of IgM in atherosclerosis.

Genome sequencing and gene-based therapies appear poised to advance the management of rare lipoprotein disorders and associated dyslipidaemias. However, in practice, underdiagnosis and undertreatment of these disorders are common, in large part due to interindividual variability in the genetic causes and phenotypic presentation of these conditions. To address these challenges, the European Atherosclerosis Society formed a task force to provide practical clinical guidance focusing on patients with extreme concentrations (either low or high) of plasma low-density lipoprotein cholesterol, triglycerides, or high-density lipoprotein cholesterol. The task force also recognises the scarcity of quality information regarding the prevalence and outcomes of these conditions. Collaborative registries are needed to improve health policy for the care of patients with rare dyslipidaemias.

BACKGROUND

Atherosclerosis is a lipid-driven chronic inflammatory disease that is modulated by many immune cell subsets, including B cells. Therefore, targeting the inflammatory component of cardiovascular disease represents a promising therapeutic strategy. In the past years, immunotherapy has revolutionized the treatment of autoimmunity and cancer. Many of these clinically used strategies target B cells. Given the multifaceted role of B cells in atherogenesis, it is conceivable that B-cell–directed therapies can modulate disease development. Here, we review clinically available B-cell–targeted therapies and the possible benefits or detrimental effects on cardiovascular disease.

Supplemental Digital Content is available in the text.

Supplemental Digital Content is available in the text.

Apolipoprotein-E (ApoE) has been implicated in Alzheimer’s disease, atherosclerosis, and other unresolvable inflammatory conditions but a common mechanism of action remains elusive. We found in ApoE-deficient mice that oxidized lipids activated the classical complement cascade (CCC), resulting in leukocyte infiltration of the choroid plexus (ChP). All human ApoE isoforms attenuated CCC activity via high-affinity binding to the activated CCC-initiating C1q protein (KD~140–580 pM) in vitro, and C1q–ApoE complexes emerged as markers for ongoing complement activity of diseased ChPs, Aβ plaques, and atherosclerosis in vivo. C1q–ApoE complexes in human ChPs, Aβ plaques, and arteries correlated with cognitive decline and atherosclerosis, respectively. Treatment with small interfering RNA (siRNA) against C5, which is formed by all complement pathways, attenuated murine ChP inflammation, Aβ-associated microglia accumulation, and atherosclerosis. Thus, ApoE is a direct checkpoint inhibitor of unresolvable inflammation, and reducing C5 attenuates disease burden.

The cardiovascular system is subject to hyperlipidaemic, inflammatory, and pro-oxidant stressors. Over time, these factors drive prevalent chronic diseases, of which atherosclerosis is most prominent and accounts for the majority of deaths globally. Antibody-producing B cells perform a unique role in responses to stress, injury, and infection. The power, inducibility, and adaptability of the antibody repertoire require an equally complex range of control measures. Defects and chronic perturbations in these checkpoints lead to inappropriate antibody responses, which might have important roles in shaping the development and outcome of atherosclerotic disease. A unique aspect related to atherosclerosis is the prominent role of natural antibodies, specifically those binding to the oxidized epitopes that are abundant on modified lipoproteins and cellular debris. B cells control cellular immune responses through cell–cell contact, antigen presentation, and cytokine production, and thereby participate in systemic and local immune responses in atherosclerotic arteries. To date, both proatherogenic and antiatherogenic properties have been assigned to B cells, depending on subsets and how they are functionally targeted. For these reasons, a deeper understanding of how B cells influence atherosclerotic plaque development is being pursued with the hope of providing novel B cell-targeted interventions to prevent inflammation-driven cardiovascular events.

Sleep is integral to life1. Although insufficient or disrupted sleep increases the risk of multiple pathological conditions, including cardiovascular disease2, we know little about the cellular and molecular mechanisms by which sleep maintains cardiovascular health. Here we report that sleep regulates haematopoiesis and protects against atherosclerosis in mice. We show that mice subjected to sleep fragmentation produce more Ly-6Chighmonocytes, develop larger atherosclerotic lesions and produce less hypocretin—a stimulatory and wake-promoting neuropeptide—in the lateral hypothalamus. Hypocretin controls myelopoiesis by restricting the production of CSF1 by hypocretin-receptor-expressing pre-neutrophils in the bone marrow. Whereas hypocretin-null and haematopoietic hypocretin-receptor-null mice develop monocytosis and accelerated atherosclerosis, sleep-fragmented mice with either haematopoietic CSF1 deficiency or hypocretin supplementation have reduced numbers of circulating monocytes and smaller atherosclerotic lesions. Together, these results identify a neuro-immune axis that links sleep to haematopoiesis and atherosclerosis.

Supplemental Digital Content is available in the text.

Supplemental Digital Content is available in the text.

Supplemental Digital Content is available in the text.

The symbiotic gut microbiota play pivotal roles in host physiology and the development of cardiovascular diseases, but the microbiota-triggered pattern recognition signaling mechanisms that impact thrombosis are poorly defined. In this article, we show that germ-free (GF) and Toll-like receptor-2 (Tlr2)-deficient mice have reduced thrombus growth after carotid artery injury relative to conventionally raised controls. GF Tlr2−/−and wild-type (WT) mice were indistinguishable, but colonization with microbiota restored a significant difference in thrombus growth between the genotypes. We identify reduced plasma levels of von Willebrand factor (VWF) and reduced VWF synthesis, specifically in hepatic endothelial cells, as a critical factor that is regulated by gut microbiota and determines thrombus growth in Tlr2−/−mice. Static platelet aggregate formation on extracellular matrix was similarly reduced in GF WT, Tlr2−/−, and heterozygous Vwf+/−mice that are all characterized by a modest reduction in plasma VWF levels. Defective platelet matrix interaction can be restored by exposure to WT plasma or to purified VWF depending on the VWF integrin binding site. Moreover, administration of VWF rescues defective thrombus growth in Tlr2−/−mice in vivo. These experiments delineate an unexpected pathway in which microbiota-triggered TLR2 signaling alters the synthesis of proadhesive VWF by the liver endothelium and favors platelet integrin–dependent thrombus growth.

Splenic marginal zone B (MZB) cells, positioned at the interface between circulating blood and lymphoid tissue, detect and respond to blood-borne antigens. Here we show that MZB cells in mice activate a homeostatic program in response to a high-cholesterol diet (HCD) and regulate both the differentiation and accumulation of T follicular helper (TFH) cells. Feeding mice an HCD resulted in upregulated MZB cell surface expression of the immunoregulatory ligand PDL1 in an ATF3-dependent manner and increased the interaction between MZB cells and pre-TFHcells, leading to PDL1-mediated suppression of TFHcell motility, alteration of TFHcell differentiation, reduced TFHabundance and suppression of the proatherogenic TFHresponse. Our findings reveal a previously unsuspected role for MZB cells in controlling the TFH–germinal center response to a cholesterol-rich diet and uncover a PDL1-dependent mechanism through which MZB cells use their innate immune properties to limit an exaggerated adaptive immune response.

Supplemental Digital Content is available in the text.

Oxidative stress results in the oxidative damage of membrane lipids, leading to the formation of neo-self epitopes, which are known as oxidation-specific epitopes (OSEs).Major carriers of OSEs are dying cells, microvesicles and damaged proteins and lipoproteins, such as oxidized low-density lipoproteins.OSEs are recognized by multiple arcs of the innate immune system, such as soluble pattern recognition receptors (natural antibodies and complement components) and cellular pattern recognition receptors (Toll-like receptors and scavenger receptors).OSEs have an important role in physiological processes by serving as markers of oxidatively modified endogenous structures, allowing the immune system to mediate their clearance and to maintain homeostasis.The accumulation of OSEs can trigger sterile inflammation.OSEs have been suggested to contribute, as drivers of disease development, to various chronic and acute inflammatory diseases, including atherosclerosis, non-alcoholic steatohepatitis and age-related macular degeneration.

Atherosclerosis is initiated and sustained by hypercholesterolemia, which results in the generation of oxidized LDL (OxLDL) and other metabolic byproducts that trigger inflammation. Specific immune responses have been shown to modulate the inflammatory response during atherogenesis. The sialic acid-binding immunoglobulin-like lectin G (Siglec-G) is a negative regulator of the functions of several immune cells, including myeloid cells and B-1 cells. Here, we show that deficiency of Siglec-G in atherosclerosis-prone mice inhibits plaque formation and diet-induced hepatic inflammation. We further demonstrate that selective deficiency of Siglec-G in B cells alone is sufficient to mediate these effects. Levels of B-1 cell-derived natural IgM with specificity for OxLDL were significantly increased in the plasma and peritoneal cavity of Siglec-G-deficient mice. Consistent with the neutralizing functions of OxLDL-specific IgM, Siglec-G-deficient mice were protected from OxLDL-induced sterile inflammation. Thus, Siglec-G promotes atherosclerosis and hepatic inflammation by suppressing protective anti-inflammatory effector functions of B cells.

Supplemental Digital Content is available in the text.

Supplemental Digital Content is available in the text.

Oxidation-specific epitopes (OSEs) present on apoptotic cells and oxidized low density lipoprotein (OxLDL) represent danger-associated molecular patterns that are recognized by different arcs of innate immunity, including natural IgM antibodies. Here, we investigated whether circulating microparticles (MPs), which are small membrane vesicles released by apoptotic or activated cells, are physiological carriers of OSEs. OSEs on circulating MPs isolated from healthy donors and patients with ST-segment elevation myocardial infarction (STE-MI) were characterized by flow cytometry using a panel of OSE-specific monoclonal antibodies. We found that a subset of MPs carry OSEs on their surface, predominantly malondialdehyde (MDA) epitopes. Consistent with this, a majority of IgM antibodies bound on the surface of circulating MPs were found to have specificity for MDA-modified LDL. Moreover, we show that MPs can stimulate THP-1 (human acute monocytic leukemia cell line) and human primary monocytes to produce interleukin 8, which can be inhibited by a monoclonal IgM with specificity for MDA epitopes. Finally, we show that MDA+MPs are elevated at the culprit lesion site of patients with STE-MI. Our results identify a subset of OSE+MPs that are bound by OxLDL-specific IgM. These findings demonstrate a novel mechanism by which anti-OxLDL IgM antibodies could mediate protective functions in CVD.

Atherosclerotic plaque formation is strongly influenced by different arms of the immune system, including B lymphocytes. B cells are divided into 2 main families: the B1 and the B2 cells. B1 cells are atheroprotective mainly via the production of natural IgM antibodies that bind oxidized low-density lipoprotein and apoptotic cells. B2 cells, which include follicular and marginal zone B cells, are suggested to be proatherogenic. Antibody-mediated depletion of B cells has become a valuable treatment option for certain autoimmune diseases, such as systemic lupus erythematosus and rheumatoid arthritis that are also characterized by the development of premature atherosclerosis. Thus, B cells represent a novel interesting target for therapeutic modulation of the atherosclerotic disease process. Here, we discuss the effect of different of B-cell subsets in experimental atherosclerosis, their mechanism of action as well as potential ways to exploit these findings for the treatment of human disease.

Immunization with homologous malondialdehyde (MDA)-modified LDL (MDA-LDL) leads to atheroprotection in experimental models supporting the concept that a vaccine to oxidation-specific epitopes (OSEs) of oxidized LDL could limit atherogenesis. However, modification of human LDL with OSE to use as an immunogen would be impractical for generalized use. Furthermore, when MDA is used to modify LDL, a wide variety of related MDA adducts are formed, both simple and more complex. To define the relevant epitopes that would reproduce the atheroprotective effects of immunization with MDA-LDL, we sought to determine the responsible immunodominant and atheroprotective adducts. We now demonstrate that fluorescent adducts of MDA involving the condensation of two or more MDA molecules with lysine to form malondialdehyde-acetaldehyde (MAA)-type adducts generate immunodominant epitopes that lead to atheroprotective responses. We further demonstrate that a T helper (Th) 2-biased hapten-specific humoral and cellular response is sufficient, and thus, MAA-modified homologous albumin is an equally effective immunogen. We further show that such Th2-biased humoral responses per se are not atheroprotective if they do not target relevant antigens. These data demonstrate the feasibility of development of a small-molecule immunogen that could stimulate MAA-specific immune responses, which could be used to develop a vaccine approach to retard or prevent atherogenesis.

Macrophages play a key role in atherogenesis in part through excessive uptake of oxidized LDL (OxLDL) via scavenger receptors. Binding of OxLDL to macrophages has traditionally been assessed using radiolabeled OxLDL. To allow more efficient and convenient measurements, we developed a nonradioactive binding assay in which biotinylated OxLDL (Bt-OxLDL) is added to macrophages in 96-well microtiter culture plates under various conditions and the extent of binding is determined using solid phase chemiluminescent immunoassay techniques. As examples, we show that Bt-OxLDL displayed high and saturable binding to macrophages in contrast to Bt-LDL, which showed very low binding. In competition assays, unlabeled OxLDL and the anti-OxLDL monoclonal antibody E06 inhibited Bt-OxLDL binding to macrophages in a dose-dependent manner. Specific binding of Bt-OxLDL to ApoE/SR-A/CD36 triple knockout macrophages was reduced by 80% as compared with binding to macrophages from ApoE knockout mice. Binding of Bt-OxLDL to CD36 transfected COS-7 cells showed enhanced saturable binding compared with mock-transfected cells. This assay avoids the use of radioactivity and uses small amounts of materials. It can be used to study binding of OxLDL to macrophages and factors that influence this binding. The techniques described should be readily adaptable to study of other ligands, receptors, and cell types.

Autoantibodies specific for malondialdehyde-modified LDL (MDA-LDL) represent potential biomarkers to predict cardiovascular risk. However, MDA-LDL is a high variability antigen with limited reproducibility. To identify peptide mimotopes of MDA-LDL, phage display libraries were screened with the MDA-LDL-specific IgM monoclonal Ab LRO4, and the specificity and antigenic properties of MDA mimotopes were assessed in vitro and in vivo. We identified one 12-mer linear (P1) and one 7-mer cyclic (P2) peptide carrying a consensus sequence, which bound specifically to murine and human anti-MDA monoclonal Abs. Furthermore, MDA mimotopes were found to mimic MDA epitopes on the surface of apoptotic cells. Immunization of mice with P2 resulted in the induction of MDA-LDL-specific Abs, which strongly immunostained human atherosclerotic lesions. We detected IgG and IgM autoAbs to both MDA mimotopes in sera of healthy subjects and patients with myocardial infarction and stable angina pectoris undergoing percutaneous coronary intervention, and the titers of autoAbs correlated significantly with respective Ab titers against MDA-LDL. In conclusion, we identified specific peptides that are immunological mimotopes of MDA. These mimotopes can serve as standardized and reproducible antigens that will be useful for diagnostic and therapeutic applications in cardiovascular disease.

Lipid peroxidation is a common event in health and is greatly accelerated in pro-inflammatory settings such as hypercholesterolemia. Consequently, oxidation-specific epitopes are generated, which are pro-inflammatory and immunogenic, leading to both adaptive and innate responses. Because innate immune mechanisms use conserved germline pattern recognition receptors (PRRs) that are preformed and present at birth, it is not obvious why they should bind to such epitopes. In this review, we put forward the hypothesis that because oxidation-specific epitopes are ubiquitous in both health and disease, and because they in essence represent "danger signals," they constitute a class of pathogen-associated molecular patterns leading to the natural selection of multiple innate PRRs that target such epitopes. We suggest that apoptotic cells, and the blebs and microparticles released from such cells, which are rich in oxidation-specific epitopes and thus pro-inflammatory, constitute an endogenous set of selecting antigens. In turn, natural antibodies, scavenger receptors, and soluble innate proteins, such as pentraxins, all represent PRRs that target such epitopes. We discuss the evidence for this hypothesis and the consequences of such responses in health and disease, such as atherosclerosis.

Oxidized phospholipids (OxPLs) on apolipoprotein B-100 (apoB-100) particles are strongly associated with lipoprotein [a] (Lp[a]). In this study, we evaluated whether Lp[a] is preferentially the carrier of OxPL in human plasma. The content of OxPL on apoB-100 particles was measured with monoclonal antibody E06, which recognizes the phosphocholine (PC) headgroup of oxidized but not native phospholipids. To assess whether OxPLs were preferentially bound by Lp[a] as opposed to other lipoproteins, immunoprecipitation and ultracentrifugation experiments, in vitro transfer studies, and chemiluminescent ELISAs were performed. Immunoprecipitation of Lp[a] from human plasma with an apolipoprotein [a] (apo[a])-specific antibody demonstrated that more than 85% of E06 reactivity (i.e., OxPL) coimmunoprecipitated with Lp[a]. Ultracentrifugation experiments showed that nearly all OxPLs were found in fractions containing apo[a], as opposed to other apolipoproteins. In vitro transfer studies showed that oxidized LDL preferentially donates OxPLs to Lp[a], as opposed to LDL, in a time- and temperature-dependent manner, even in aqueous buffer. Approximately 50% of E06 immunoreactivity could be extracted from isolated Lp[a] following exposure of plasma to various lipid solvents. These data demonstrate that Lp[a] is the preferential carrier of PC-containing OxPL in human plasma. This unique property of Lp[a] suggests novel insights into its physiological function and mechanisms of atherogenicity.

Atherosclerosis is now widely recognized as a chronic inflammatory disease that involves innate and adaptive immune responses. Both cellular and humoral components of the immune system have been implicated in atherogenesis. Natural antibodies can be considered humoral factors of innate immunity, and their functional role in health and disease has been reexamined in recent years. Natural antibodies exhibit a remarkably conserved repertoire that includes a broad specificity for self-antigens. For this reason, they are believed to be a product of natural selection and have been suggested to play an important role in "housekeeping" functions. Recent evidence has revealed that oxidation-specific epitopes are important and maybe immunodominant targets of natural antibodies, suggesting an important function for these antibodies in the host response to consequences of oxidative stress, for example, to the oxidative events that occur when cells undergo apoptosis. This review will focus on these recent findings and discuss the emerging evidence for an important role of natural antibodies in atherogenesis.

Oxidation of low density lipoprotein (LDL) generates a variety of oxidatively modified lipids and lipid-protein adducts that are immunogenic and proinflammatory, which in turn contribute to atherogenesis. Cells undergoing apoptosis also display oxidized moieties on their surface membranes, as determined by binding of oxidation-specific monoclonal antibodies. In the present paper, we demonstrated by mass spectrometry that in comparison with viable cells, membranes of cells undergoing apoptosis contain increased levels of biologically active oxidized phospholipids (OxPLs). Indeed, immunization of mice with syngeneic apoptotic cells induced high autoantibody titers to various oxidation-specific epitopes of oxidized LDL, including OxPLs containing phosphorylcholine, whereas immunization with viable thymocytes, primary necrotic thymocytes, or phosphate-buffered saline did not. Reciprocally, these antisera specifically bound to apoptotic cells through the recognition of oxidation-specific epitopes. Moreover, splenocyte cultures from mice immunized with apoptotic cells spontaneously released significant levels of T helper cell (Th) 1 and Th2 cytokines, whereas splenocytes from controls yielded only low levels. Finally, we demonstrated that the OxPLs of apoptotic cells activated endothelial cells to induce monocyte adhesion, a proinflammatory response that was abrogated by an antibody specific to oxidized phosphatidylcholine. These results suggest that apoptotic cell death generates oxidatively modified moieties, which can induce autoimmune responses and a local inflammatory response by recruiting monocytes via monocyte–endothelial cell interaction.

This study tests the hypothesis that autoantibodies to oxidation epitopes on oxidized LDL (OxLDL) promote the clearance of OxLDL from the plasma. Human LDL (hLDL) was injected into immune-competent apolipoprotein E-deficient (apoE(-/-)) mice and immune-deficient apoE(-/-)/recombination-activating gene-deficient mice that lack mature T and B cells and thus antibodies. There was a progressive decrease in human apoB-100 in the plasma in all mice, but the rate of clearance was not greater in the immune-competent mice than in the immune-deficient mice. Interestingly, oxidized phospholipid (OxPL) epitopes as detected by the EO6 antibody on the hLDL increased over time, suggesting de novo oxidation of the LDL or transfer of OxPL to the particles. Because the native LDL was not extensively modified, we also examined the clearance of copper OxLDL. Although the extensively OxLDL was cleared faster than the native LDL, there was no difference in the rate of clearance as a function of immune status. There appeared to be some transfer of OxPL to the endogenous murine LDL. Together, these results suggest that oxidation-specific antibodies do not participate to any great extent in the clearance of OxLDL from plasma. However, it is possible that such antibodies may bind to oxidation epitopes and modulate lesion formation within the vessel wall.

Atherosclerosis is now recognized as a chronic inflammatory disease. This review discusses recent literature reporting that innate immune receptors bind oxidatively modified LDL and its many oxidized moieties and consequently modulate the atherogenic process. These innate pattern recognition receptors are known to play a central role in pro-inflammatory responses to bacteria by binding pathogen-associated molecular patterns. It is hypothesized that oxidized LDL exposes similar molecular patterns recognized by receptors of innate immunity.

Focal segmental glomerulosclerosis is a steroid-resistant glomerular disease characterized by foot process flattening and heavy proteinuria. A similar disease was found to occur spontaneously in mice in which the Mpv17 gene was inactivated by retroviral insertion (Mpv17−/− mice). Here evidence is provided that glomerular damage in this murine model is due to overproduction of oxygen radicals and accumulation of lipid peroxidation adducts that were found in isolated glomeruli of Mpv17−/− mice. The development of glomerular disease in Mpv17−/− mice was inhibited by scavengers of oxygen radicals (dithiomethylurea) and lipid peroxidation (probucol), but not by steroid treatment. Although the glomerular polyanion was greatly reduced in proteinuric Mpv17−/− mice, it was preserved by antioxidative therapy. These results indicate that the glomerular disease in Mpv17−/− mice qualifies as a model of steroid-resistant focal segmental glomerulosclerosis and that experimental therapies with scavengers of oxygen radicals and lipid peroxidation efficiently ameliorate glomerular damage.

The European Atherosclerosis Society Familial Hypercholesterolaemia Studies Collaboration (FHSC) global registry provides a platform for the global surveillance of familial hypercholesterolaemia through harmonisation and pooling of multinational data. In this study, we aimed to characterise the adult population with heterozygous familial hypercholesterolaemia and described how it is detected and managed globally.

In the version of this article originally published, a sentence was erroneously included in the author contributions, and information regarding second shared authorship was missing from the author contributions. The following should not have been included in the author contributions: “C.W. and A.J.R.H. supervised the work presented in Figs. 1, 2, 5, 6; P.Z. and C.S. supervised the work presented in Figs. 3, 4.” Additionally, this sentence should have appeared at the beginning of the author contributions: “These authors contributed equally: C.W., P.F.Z., C.S., and A.J.R.H.” The errors have been corrected in the print, PDF and HTML versions of the article.

No relevant conflicts of interest to declare.

Autoantibodies specific for malondialdehyde modified LDL (MDA-LDL) represent potential biomarkers to predict cardiovascular risk. However, the generation of MDA-LDL results in the formation of many different epitopes with high variability. Because it is not known, which MDA epitope is biological important, the aim of this study was to identify and characterize peptide mimotopes of MDA-LDL that could be used as antigens to improve the reproducible detection of MDA-specific autoantibodies.

In normal individuals microparticles (MPs) derived from leukocytes, erythrocytes, platelets and endothelial cells are found in the circulation. When the thrombogenicity of microparticles was measured in vitro by their capacity to generate thrombin (thrombin generating activity, TGA) in normal control plasma we found the highest in vitro activity to be generated by red blood cell derived MPs and the lowest by monocyte derived MPs. While all MPs exhibited Annexin V binding, indicating the presence of negatively charged phospholipids on the surface, only monocyte and smooth muscle cell (SMC) derived MPs expressed tissue factor and their TGA was dependent on the “extrinsic” factor VII dependent pathway. All other MPs utilized the “intrinsic” factor XI, factor IX and VIII dependent pathway. In vivo, however, only MPs activating the “extrinsic” pathway were active as shown by TAT formation upon injection of MPs in wt C57/bl6 mice (3 minutes after injection). When, however, not directly thrombogenic MPs derived from red blood cells were co-injected with tissue factor bearing MPs, TAT formation was significantly enhanced, indicating that non-directly thrombogenic MPs need tissue factor “priming” to become thrombogenic. To prove this hypothesis, we injected red blood cell (RBC) derived MPs (106–108) into wild type C57BL/6 mice and into ApoE−/− or LDLR−/ − deficient mice, fed a high lipid diet. In wild type C57BL6 mice red blood cell derived MPs did not significantly increase TAT complexes as compared to PBS (RBC derived MPs 108 6.2±0.8 vs. PBS 4.1±1.3 mg/L). When, however, such RBC derived MPs were injected into LDLR−/− mice fed a high lipid diet, TAT complexes significantly increased (PBS 4.4±0.5 vs RBC derived MPs 108 15.8±1.9mg/L). Similar results were obtained also in ApoE−/− mice. This indicates that tissue factor “priming” also occurs in atherosclerotic mice, likely by tissue factor expressed on the plaque or by plaque derived tissue factor bearing MPs. To determine whether local tissue factor expression causes also local fibrin formation upon injection of red blood cell derived MPs, the aortic arch of such mice were analyzed for local fibrin deposition after injection of red blood cell derived MPs. In fact red blood cell derived MPs did not only induce higher TAT complexes in LDLR−/− mice but also increased the number of fibrin positive plaques as compared to PBS. This indicates that red blood cell derived MPs are thrombogenic in animal models of atherosclerosis. When MPs isolated form the arterial blood of atherosclerotic patients undergoing carotid endarterectomy were analyzed, it was found that MPs from symptomatic patients were more thrombogenic and that this increased thrombogenicity was due to increased number of red blood cell derived MPs. This indicates that red blood cell derived MPs might also cause thrombus formation in atherosclerotic patients.