Prediction of myocardial infarction in dyslipidemic men by elevated levels of immunoglobulin classes A, E, and G, but not M

Therapeutic Avenues to Modulate B-Cell Function in Patients With Cardiovascular Disease

The adaptive immune system plays an important role in the development and progression of atherosclerotic cardiovascular disease. B cells can have both proatherogenic and atheroprotective roles, making treatments aimed at modulating B cells important therapeutic targets. The innate-like B-cell response is generally considered atheroprotective, while the adaptive response is associated with mixed consequences for atherosclerosis. Additionally, interactions of B cells with components of the adaptive and innate immune system, including T cells and complement, also represent key points for therapeutic regulation. In this review, we discuss therapeutic approaches based on B-cell depletion, modulation of B-cell survival, manipulation of both the antibody-dependent and antibody-independent B-cell response, and emerging immunization techniques.

Mast cells: a novel therapeutic avenue for cardiovascular diseases?

Mast cells are tissue-resident immune cells strategically located in different compartments of the normal human heart (the myocardium, pericardium, aortic valve, and close to nerves) as well as in atherosclerotic plaques. Cardiac mast cells produce a broad spectrum of vasoactive and proinflammatory mediators, which have potential roles in inflammation, angiogenesis, lymphangiogenesis, tissue remodelling, and fibrosis. Mast cells release preformed mediators (e.g. histamine, tryptase, and chymase) and de novo synthesized mediators (e.g. cysteinyl leukotriene C4 and prostaglandin D2), as well as cytokines and chemokines, which can activate different resident immune cells (e.g. macrophages) and structural cells (e.g. fibroblasts and endothelial cells) in the human heart and aorta. The transcriptional profiles of various mast cell populations highlight their potential heterogeneity and distinct gene and proteome expression. Mast cell plasticity and heterogeneity enable these cells the potential for performing different, even opposite, functions in response to changing tissue contexts. Human cardiac mast cells display significant differences compared with mast cells isolated from other organs. These characteristics make cardiac mast cells intriguing, given their dichotomous potential roles of inducing or protecting against cardiovascular diseases. Identification of cardiac mast cell subpopulations represents a prerequisite for understanding their potential multifaceted roles in health and disease. Several new drugs specifically targeting human mast cell activation are under development or in clinical trials. Mast cells and/or their subpopulations can potentially represent novel therapeutic targets for cardiovascular disorders.

Plasma viscosity, immunoglobulins and risk of cardiovascular disease and mortality: new data and meta-analyses

AIMS

Associations of plasma viscosity and plasma Ig levels (a determinant of viscosity) with incident coronary heart disease (CHD) events; and with CHD, cardiovascular disease (CVD: CHD and stroke) and all-cause mortalities.

METHODS

Meta-analysis of plasma viscosity levels from the MONitoring of trends and determinants of CArdiovascular (MONICA)/Cooperative Health Research in the Region of Augsburg, MONICA Glasgow and Speedwell Studies; and five other published studies. Meta-analysis of IgA, IgG and IgM levels from the Augsburg, Glasgow and Speedwell studies; and one other published study.

RESULTS

Over median follow-up periods of 14-26 years, there were 2270 CHD events, and 4220 all cause deaths in 28 605 participants with baseline plasma viscosity measurements. After adjustment for major risk factors, (HRs; 95% CIs) for a 1 SD increase in viscosity were 1.14 (1.09 to 1.20) for CHD events; and 1.21 (1.17 to 1.25) for all-cause mortality. 821 CHD events and 2085 all-cause deaths occurred in 8218 participants with baseline Ig levels. For CHD events, adjusted HRs for 1 SD increases in IgA, IgG and IgM were, respectively, 0.97 (0.89 to 1.05); 0.95(0.76 to 1.17) and 0.90 (0.79 to 1.03). Corresponding adjusted HRs for all-cause mortality were 1.08 (95% CI 1.02 to 1.13), 1.03 (95% CI 0.94 to 1.14) and 1.01 (95% CI 0.96 to 1.06).

CONCLUSIONS

After risk factor adjustment, plasma viscosity was significantly associated with risks of CHD events; and with CHD, CVD and all-cause mortalities. We found no significant association of IgA, IgG or IgM levels with incident CHD events or mortality, except for a borderline association of IgA with all-cause mortality.

Mast cells participate in smooth muscle cell reprogramming and atherosclerotic plaque calcification

BACKGROUND

Calcification, a key feature of advanced human atherosclerosis, is positively associated with vascular disease burden and adverse events. We showed that macrocalcification can be a stabilizing factor for carotid plaque molecular biology, due to inverse association with immune processes. Mast cells (MCs) are important contributors to plaque instability, but their relationship with macrocalcification is unexplored. With a hypothesis that MC activation negatively associates with carotid plaque macrocalcification, we aimed to investigate the link between MCs and carotid plaque vulnerability, and study MC role in plaque calcification via smooth muscle cells (SMCs).

METHODS

Pre-operative computed tomography angiographies of patients (n = 40) undergoing surgery for carotid stenosis were used to characterize plaque morphology. Plaque microarrays (n = 40 and n = 126) were used for bioinformatic deconvolution of immune cell populations. Tissue microarrays (n = 103) were used to histologically validate the contribution of activated and resting MCs in plaques.

RESULTS

Activated MCs and their typical markers were negatively correlated with macrocalcification. The ratio of activated vs. resting MCs was increased in low-calcified plaques from symptomatic patients. There was no modulating effect of medication on MC ratios. In vitro experiments showed that SMC calcification attenuated MC activation, while both active and resting MCs stimulated SMC calcification and induced dedifferentiation towards a pro-inflammatory-, osteochondrocyte-like phenotype, without modulating their migro-proliferative function.

CONCLUSIONS

Integrative analyses from human plaques showed that MC activation is inversely associated with macrocalcification and positively with parameters of plaque vulnerability. Mechanistically, MCs induce SMC osteogenic reprograming, while matrix calcification in turn attenuates MC activation, offering new therapeutic avenues for exploration.

Antibodies in action: the role of humoral immunity in the fight against atherosclerosis

The sequestering of oxidation-modified low-density lipoprotein by macrophages results in the accumulation of fatty deposits within the walls of arteries. Necrosis of these cells causes a release of intercellular epitopes and the activation of the adaptive immune system, which we predict leads to robust autoantibody production. T cells produce cytokines that act in the plaque environment and further stimulate B cell antibody production. B cells in atherosclerosis meanwhile have a mixed role based on subclass. The current model is that B-1 cells produce protective IgM antibodies in response to oxidation-specific epitopes that work to control plaque formation, while follicular B-2 cells produce class-switched antibodies (IgG, IgA, and IgE) which exacerbate the disease. Over the course of this review, we discuss further the validation of these protective antibodies while evaluating the current dogma regarding class-switched antibodies in atherosclerosis. There are several contradictory findings regarding the involvement of class-switched antibodies in the disease. We hypothesize that this is due to antigen-specificity, and not simply isotype, being important, and that a closer evaluation of these antibodies' targets should be conducted. We propose that specific antibodies may have therapeutical potential in preventing and controlling plaque development within a clinical setting.

Autoantibodies to IgE can induce the release of proinflammatory and vasoactive mediators from human cardiac mast cells

Mast cells are multifunctional immune cells with complex roles in tissue homeostasis and disease. Cardiac mast cells (HCMCs) are strategically located within the human myocardium, in atherosclerotic plaques, in proximity to nerves, and in the aortic valve. HCMCs express the high-affinity receptor (FcεRI) for IgE and can be activated by anti-IgE and anti-FcεRI. Autoantibodies to IgE and/or FcεRI have been found in the serum of patients with a variety of immune disorders. We have compared the effects of different preparations of IgG anti-IgE obtained from patients with atopic dermatitis (AD) with rabbit IgG anti-IgE on the release of preformed (histamine and tryptase) and lipid mediators [prostaglandin D₂ (PGD₂) and cysteinyl leukotriene C₄ (LTC₄)] from HCMCs. Functional human IgG anti-IgE from one out of six AD donors and rabbit IgG anti-IgE induced the release of preformed (histamine, tryptase) and de novo synthesized mediators (PGD₂ and LTC₄) from HCMCs. Human IgG anti-IgE was more potent than rabbit IgG anti-IgE in inducing proinflammatory mediators from HCMCs. Human monoclonal IgE was a competitive antagonist of both human and rabbit IgG anti-IgE. Although functional anti-IgE autoantibodies rarely occur in patients with AD, when present, they can powerfully activate the release of proinflammatory and vasoactive mediators from HCMCs.

Changes in Specific Biomarkers Indicate Cardiac Adaptive and Anti-inflammatory Response of Repeated Recreational SCUBA Diving

Objective

Recreational SCUBA (rSCUBA) diving has become a highly popular and widespread sport. Yet, information on molecular events underlying (patho)physiological events that follow exposure to the specific environmental conditions (hyperbaric conditions, coldness, immersion, and elevated breathing pressure), in which rSCUBA diving is performed, remain largely unknown. Our previous study suggested that repeated rSCUBA diving triggers an adaptive response of cardiovascular and immune system. To elucidate further molecular events underlying cardiac and immune system adaptation and to exclude possible adverse effects we measured blood levels of specific cardiac and inflammation markers.

Methods

This longitudinal intervention study included fourteen recreational divers who performed five dives, one per week, on the depth 20–30 m that lasted 30 min, after the non-dive period of 5 months. Blood samples were taken immediately before and after the first, third, and fifth dives. Copeptin, immunoglobulins A, G and M, complement components C3 and C4, and differential blood count parameters, including neutrophil-to-lymphocyte ratio (NLR) were determined using standard laboratory methods. Cell-free DNA was measured by qPCR analysis and N-glycans released from IgG and total plasma proteins (TPP), were analyzed by hydrophilic interaction ultra-performance liquid chromatography.

Results

Copeptin level increased after the first dive but decreased after the third and fifth dive. Increases in immunoglobulins level after every dive and during whole studied period were observed, but no changes in C3, C4, and cfDNA level were detected. NLR increased only after the first dive. IgG and TPP N-glycosylation alterations toward anti-inflammatory status over whole studied period were manifested as an increase in monogalyctosylated and core-fucosylated IgG N-glycans and decrease in agalactosylated TPP N-glycans.

Conclusion

rSCUBA diving practiced on a regular basis promotes anti-inflammatory status thus contributing cardioprotection and conferring multiple health benefits.

Quantitative proteomics reveals differential immunoglobulin-associated proteome (IgAP) in patients of acute myocardial infarction and chronic coronary syndromes

B cells and immunoglobulins are implicated in the pathogenesis of chronic diseases, including coronary artery disease (CAD). However, it remains elusive how the humoral immunity is incriminated in the disease progression of CAD. Using serum samples of chronic coronary syndrome (CCS) and acute myocardial infarction (AMI), we conducted a quantitative profiling of the proteomic landscape recognized by immunoglobulins, which we term immunoglobulin-associated proteome (IgAP). Intriguingly, CCS and AMI patients displayed distinctive IgAP profiles that enriched proteins in the pathways of blood coagulation regulation and lipoprotein transport, suggesting that CCS-AMI transition involves changes of these pathways that are associated with immunoglobulins. Furthermore, we identified immunoglobulin-bound coagulation factor X (F10) as a potential biomarker and validated it with an independent cohort of CCS, AMI and healthy individuals. Our study indicates that IgAP proteins may serve as novel diagnostic biomarkers for CCS and AMI. SIGNIFICANCE: Our work it demonstrates a clear implication of immunoglobulin-associated proteome (IgAP), the proteomic landscape recognized by immunoglobulins, in the pathogenesis of CAD. In addition, it reports for the first time that immunoglobulin-bound F10 is implicated in CAD.

Unbiased plasma proteomics discovery of biomarkers for improved detection of subclinical atherosclerosis

Background

Imaging of subclinical atherosclerosis improves cardiovascular risk prediction on top of traditional risk factors. However, cardiovascular imaging is not universally available. This work aims to identify circulating proteins that could predict subclinical atherosclerosis.

Methods

Hypothesis-free proteomics was used to analyze plasma from 444 subjects from PESA cohort study (222 with extensive atherosclerosis on imaging, and 222 matched controls) at two timepoints (three years apart) for discovery, and from 350 subjects from AWHS cohort study (175 subjects with extensive atherosclerosis on imaging and 175 matched controls) for external validation. A selected three-protein panel was further validated by immunoturbidimetry in the AWHS population and in 2999 subjects from ILERVAS cohort study.

Findings

PIGR, IGHA2, APOA, HPT and HEP2 were associated with subclinical atherosclerosis independently from traditional risk factors at both timepoints in the discovery and validation cohorts. Multivariate analysis rendered a potential three-protein biomarker panel, including IGHA2, APOA and HPT. Immunoturbidimetry confirmed the independent associations of these three proteins with subclinical atherosclerosis in AWHS and ILERVAS. A machine-learning model with these three proteins was able to predict subclinical atherosclerosis in ILERVAS (AUC [95%CI]:0.73 [0.70–0.74], p < 1 × 10⁻⁹⁹), and also in the subpopulation of individuals with low cardiovascular risk according to FHS 10-year score (0.71 [0.69–0.73], p < 1 × 10⁻⁶⁹).

Interpretation

Plasma levels of IGHA2, APOA and HPT are associated with subclinical atherosclerosis independently of traditional risk factors and offers potential to predict this disease. The panel could improve primary prevention strategies in areas where imaging is not available.

Immune system and atherosclerosis: Hostile or friendly relationship

Coronary artery disease has remained a major health challenge despite enormous progress in prevention, diagnosis, and treatment strategies. Formation of atherosclerotic plaque is a chronic process that is developmentally influenced by intrinsic and extrinsic determinants. Inflammation triggers atherosclerosis, and the fundamental element of inflammation is the immune system. The immune system involves in the atherosclerosis process by a variety of immune cells and a cocktail of mediators. It is believed that almost all main components of this system possess a profound contribution to the atherosclerosis. However, they play contradictory roles, either protective or progressive, in different stages of atherosclerosis progression. It is evident that monocytes are the first immune cells appeared in the atherosclerotic lesion. With the plaque growth, other types of the immune cells such as mast cells, and T lymphocytes are gradually involved. Each cell releases several cytokines which cause the recruitment of other immune cells to the lesion site. This is followed by affecting the expression of other cytokines as well as altering certain signaling pathways. All in all, a mix of intertwined interactions determine the final outcome in terms of mild or severe manifestations, either clinical or subclinical. Therefore, it is of utmost importance to precisely understand the kind and degree of contribution which is made by each immune component in order to stop the growing burden of cardiovascular morbidity and mortality. In this review, we present a comprehensive appraisal on the role of immune cells in the atherosclerosis initiation and development.

Humoral immunity in atherosclerosis and myocardial infarction: from B cells to antibodies

Immune mechanisms are critically involved in the pathogenesis of atherosclerosis and its clinical manifestations. Associations of specific antibody levels and defined B cell subsets with cardiovascular disease activity in humans as well as mounting evidence from preclinical models demonstrate a role of B cells and humoral immunity in atherosclerotic cardiovascular disease. These include all aspects of B cell immunity, the generation of antigen-specific antibodies, antigen presentation and co-stimulation of T cells, as well as production of cytokines. Through their impact on adaptive and innate immune responses and the regulation of many other immune cells, B cells mediate both protective and detrimental effects in cardiovascular disease. Several antigens derived from (oxidised) lipoproteins, the vascular wall and classical autoantigens have been identified. The unique antibody responses they trigger and their relationship with atherosclerotic cardiovascular disease are reviewed. In particular, we focus on the different effector functions of specific IgM, IgG, and IgE antibodies and the cellular responses they trigger and highlight potential strategies to target B cell functions for therapy.

Data-Independent Acquisition Proteomics Reveals Long-Term Biomarkers in the Serum of C57BL/6J Mice Following Local High-Dose Heart Irradiation

Background and Purpose: Cardiotoxicity is a well-known adverse effect of radiation therapy. Measurable abnormalities in the heart function indicate advanced and often irreversible heart damage. Therefore, early detection of cardiac toxicity is necessary to delay and alleviate the development of the disease. The present study investigated long-term serum proteome alterations following local heart irradiation using a mouse model with the aim to detect biomarkers of radiation-induced cardiac toxicity.

Materials and Methods: Serum samples from C57BL/6J mice were collected 20 weeks after local heart irradiation with 8 or 16 Gy X-ray; the controls were sham-irradiated. The samples were analyzed by quantitative proteomics based on data-independent acquisition mass spectrometry. The proteomics data were further investigated using bioinformatics and ELISA.

Results: The analysis showed radiation-induced changes in the level of several serum proteins involved in the acute phase response, inflammation, and cholesterol metabolism. We found significantly enhanced expression of proinflammatory cytokines (TNF-α, TGF-β, IL-1, and IL-6) in the serum of the irradiated mice. The level of free fatty acids, total cholesterol, low-density lipoprotein (LDL), and oxidized LDL was increased, whereas that of high-density lipoprotein was decreased by irradiation.

Conclusions: This study provides information on systemic effects of heart irradiation. It elucidates a radiation fingerprint in the serum that may be used to elucidate adverse cardiac effects after radiation therapy.

Mast Cells Are the Trigger of Small Vessel Disease and Diastolic Dysfunction in Diabetic Obese Mice

[Figure: see text].

Immunoglobulin G levels predicts risk of recurrent adverse cardiovascular events in myocardial infarction patients

Background: Patients with myocardial infarction (MI) are at an increased risk of experiencing recurrent major adverse cardiovascular events (MACE) but predicting MACE has remained challenging. Immunoglobulins are implicated in cardiovascular disease, although the predictive value of total immunoglobulin G (IgG) has not yet been evaluated in a secondary prevention setting. This study examined whether total IgG is predictive of MACE in an MI population, and how total IgG compared to the predictive value of C-reactive protein (CRP), an acute inflammatory marker. Methods: We conducted a case-control study with 40 MI subjects (cases) who experienced MACE within 1 year of their index admission. Cases were matched for age, sex, diabetes and presentation with 77 controls who did not have MACE. Pre-discharge plasma samples were analysed for total IgG and CRP. Results: We observed higher levels of total plasma IgG in MI subjects with MACE (24.9 (16.2-43.7) mg/mL) compared to controls (18.4 (9.1-37.3) mg/mL; p < 0.05). Higher levels of IgG were associated with increased risk of MACE in our MI population. MI subjects within quartiles 3 and 4 of total IgG had 6 times and 4 times, respectively, the rate of MACE compared to subjects in quartile 1. There was no difference in CRP levels between cases and controls (1.1 (0.5-3.0) vs. 1.9 (0.6-6.1) mg/mL, p = 0.10), and no relationship was observed between CRP and MACE. Conclusion: Pre-discharge IgG level was a better marker for predicting MACE post-MI than CRP, which had no predictive value in this study.

Multisystem Trajectories Over the Adult Life Course and Relations to Cardiovascular Disease and Death

BACKGROUND

Comprehensive conjoint characterization of long-term trajectories representing several biological systems is lacking.

METHODS

We measured serially indicators representing 14 distinct biological systems in up to 3,453 participants attending four Framingham Study examinations: bone mineral density, body mass index (BMI), C-reactive protein, glomerular filtration rate, forced vital capacity (FVC), 1 second forced expiratory volume/FVC ratio (FEV1/FVC), gait speed, grip strength, glycosylated hemoglobin (HbA1c), heart rate, left ventricular mass, Mini-Mental State Examination (MMSE), pulse pressure, and total/high-density lipoprotein cholesterol ratio (TC/HDL).

RESULTS

We observed that correlations among the 14 sex-specific trajectories were modest (r < .30 for 169 of 182 sex-specific correlations). During follow-up (median 8 years), 232 individuals experienced a cardiovascular disease (CVD) event and 393 participants died. In multivariable regression models, CVD incidence was positively related to trajectories of BMI, HbA1c, TC/HDL, gait time, and pulse pressure (p < .06); mortality risk was related directly to trajectories of gait time, C-reactive protein, heart rate, and pulse pressure but inversely to MMSE and FEV1/FVC (p < .006). A unit increase in the trajectory risk score was associated with a 2.80-fold risk of CVD (95% confidence interval [CI], 2.04-3.84; p < .001) and a 2.71-fold risk of death (95% CI, 2.30-3.20; p < .001). Trajectory risk scores were suggestive of a greater increase in model c-statistic compared with single occasion measures (delta-c compared with age- and sex-adjusted models: .032 vs .026 for CVD; .042 vs .030 for mortality).

CONCLUSIONS

Biological systems age differentially over the life course. Longitudinal data on a parsimonious set of biomarkers reflecting key biological systems may facilitate identification of high-risk individuals.

Low frequency of IL-10+ B cells in patients with atherosclerosis is related with inflammatory condition

Background and aims

B cells involvement in animal models of atherosclerosis has been unequivocally established. However, the role of these cells in patients with atherosclerosis is almost unknown. Besides the production of antibodies, B cells can also exhibit regulatory functions mainly through IL-10. Here, we characterized human B cell subsets, their production of IL-10 in patients with atherosclerosis and their potential association with inflammation.

Methods

Patients with confirmed atherosclerotic events and controls with low cardiovascular risk were included. B cells subsets were determined in mononuclear cells (PBMC) using flow cytometry. PBMC were cultured ex vivo (5 h) and in vitro (48 h) to determine IL-10⁺ B cells and in some cases TNF-α⁺ and IFN-γ⁺ CD4⁺ T cells. The inflammatory state of the participants was determined through high sensitivity C reactive protein levels.

Results

Increase in percentage and number of plasmablasts was observed in patients with atherosclerosis compared with controls. A decreased frequency of IL-10⁺ B cells was observed in patients, both in ex vivo and in vitro cultures. This decrease was detected in transitional, memory, and plasmablast subsets. Interestingly, the reduction of IL-10⁺ B cells negatively and significantly correlated with the inflammatory condition of the studied subjects and associated with an increased frequency of TNF-α⁺ and IFN-γ⁺ CD4⁺ T cells. The blockade of IL-10R did not show further effect in T cells activation.

Conclusions

There is an association between the inflammatory state and a reduction of IL-10⁺ B cells that could contribute to the development of atherosclerosis.

PD-1/PD-L1 in cardiovascular disease

The PD-1/PD-L1 coinhibitory pathway has critical roles in the immune response and autoimmunity via the regulation of T cell activity. Excessive activity and high expression of this pathway suppresses the function of T cells and immunity. Recent research has indicated that tumour cells express high levels of PD-L1, which has an immunosuppressive effect and can result in treatment failure. Anti-PD-L1 or anti-PD-1 agents have well-established beneficial effects on mortality and quality of life in cancer patients. Based on the regulatory effects and therapeutic value of the PD-1/PD-L1 pathway in malignant disorders, we propose that it also regulates cell immunity and in CHD and atherosclerosis. Low expression level of PD-1/ PD-L1 or anti-PD-1/PD-L1 therapy accelerates the immune processes in CHD and aggravates disease according to numerous studies. A few studies have provided strong evidence that changes in the expression levels of PD-1 or PD-L1 can alter the degree of inflammation and the state of coronary plaques in atherosclerosis. In this review, we summarise the alterations of the PD-1/PD-L1 pathway and discuss its role in CHD.

Mast Cells as Potential Accelerators of Human Atherosclerosis-From Early to Late Lesions

Mast cells are present in atherosclerotic lesions throughout their development. The process of atherogenesis itself is characterized by infiltration and retention of cholesterol-containing blood-derived low-density lipoprotein (LDL) particles in the intimal layer of the arterial wall, where the particles become modified and ingested by macrophages, resulting in the formation of cholesterol-filled foam cells. Provided the blood-derived high-density lipoproteins (HDL) particles are able to efficiently carry cholesterol from the foam cells back to the circulation, the early lesions may stay stable or even disappear. However, the modified LDL particles also trigger a permanent local inflammatory reaction characterized by the presence of activated macrophages, T cells, and mast cells, which drive lesion progression. Then, the HDL particles become modified and unable to remove cholesterol from the foam cells. Ultimately, the aging foam cells die and form a necrotic lipid core. In such advanced lesions, the lipid core is separated from the circulating blood by a collagenous cap, which may become thin and fragile and susceptible to rupture, so causing an acute atherothrombotic event. Regarding the potential contribution of mast cells in the initiation and progression of atherosclerotic lesions, immunohistochemical studies in autopsied human subjects and studies in cell culture systems and in atherosclerotic mouse models have collectively provided evidence that the compounds released by activated mast cells may promote atherogenesis at various steps along the path of lesion development. This review focuses on the presence of activated mast cells in human atherosclerotic lesions. Moreover, some of the molecular mechanisms potentially governing activation and effector functions of mast cells in such lesions are presented and discussed.

Mast Cells in Cardiovascular Disease: From Bench to Bedside

Mast cells are pluripotent leukocytes that reside in the mucosa and connective tissue. Recent studies show an increased prevalence of cardiovascular disease among patients with mastocytosis, which is a hematological disease that is characterized by the accumulation of mast cells due to clonal proliferation. This association suggests an important role for mast cells in cardiovascular disease. Indeed, the evidence establishing the contribution of mast cells to the development and progression of atherosclerosis is continually increasing. Mast cells may contribute to plaque formation by stimulating the formation of foam cells and causing a pro-inflammatory micro-environment. In addition, these cells are able to promote plaque instability by neo-vessel formation and also by inducing intraplaque hemorrhage. Furthermore, mast cells appear to stimulate the formation of fibrosis after a cardiac infarction. In this review, the available data on the role of mast cells in cardiovascular disease are summarized, containing both in vitro research and animal studies, followed by a discussion of human data on the association between cardiovascular morbidity and diseases in which mast cells are important: Kounis syndrome, mastocytosis and allergy.

Superantigenic Activation of Human Cardiac Mast Cells

B cell superantigens, also called immunoglobulin superantigens, bind to the variable regions of either the heavy or light chain of immunoglobulins mirroring the lymphocyte-activating properties of classical T cell superantigens. Protein A of Staphylococcus aureus, protein L of Peptostreptococcus magnus, and gp120 of HIV are typical immunoglobulin superantigens. Mast cells are immune cells expressing the high-affinity receptor for IgE (FcεRI) and are strategically located in the human heart, where they play a role in several cardiometabolic diseases. Here, we investigated whether immunoglobulin superantigens induced the activation of human heart mast cells (HHMCs). Protein A induced the de novo synthesis of cysteinyl leukotriene C₄ (LTC₄) from HHMCs through the interaction with IgE V_H3⁺ bound to FcεRI. Protein L stimulated the production of prostaglandin D₂ (PGD₂) from HHMCs through the interaction with κ light chains of IgE. HIV glycoprotein gp120 induced the release of preformed (histamine) and de novo synthesized mediators, such as cysteinyl leukotriene C₄ (LTC₄), angiogenic (VEGF-A), and lymphangiogenic (VEGF-C) factors by interacting with the V_H3 region of IgE. Collectively, our data indicate that bacterial and viral immunoglobulin superantigens can interact with different regions of IgE bound to FcεRI to induce the release of proinflammatory, angiogenic, and lymphangiogenic factors from human cardiac mast cells.

Postmortem IgE determination in coronary artery disease

Allergic, IgE-mediated inflammation is thought to play a role in atherogenesis and atherosclerotic disease progression. In this study, total IgE and mast cell tryptase were measured in a series of forensic autopsy cases including non-allergic cardiac deaths (14 cases with minimal or no coronary atherosclerosis, 14 cases with significant coronary artery atherosclerosis without acute coronary thrombosis, and 14 cases with significant coronary artery atherosclerosis and acute coronary thrombosis or myocardial infarction) and non-allergic non-cardiac deaths (21 cases with death due to hanging and 21 cases with death due to intracranial gunshot wounds), in order to correlate laboratory results with morphological findings and compare them to conclusions reported in the clinical setting. In cardiac death cases, postmortem serum total IgE levels were increased in 7 out of 42 cases and mast cell tryptase levels were increased in 3 out of 42 cases. In non-cardiac death cases, postmortem serum total IgE levels were not increased in 39 out of 42 cases and mast cell tryptase levels were not increased in any of these cases. These preliminary findings seem to indicate that a portion of coronary deaths characterized by coronary artery atherosclerosis of various severities are also characterized by increased total IgE and mast cell tryptase levels, thus corroborating the data previously reported in both clinical and forensic literature on this topic as well as the necessity of combining morphological investigations focusing on the heart and coronary arteries with biochemical analyses.

Associations of immunological factors with metabolic syndrome and its characteristic elements in Chinese centenarians

BACKGROUND

Metabolic syndrome (MetS) has an increased prevalence (approximately 20-25% of the adult population) all over the world. Immunological function is significantly associated with the development of MetS, and MetS is beginning to be considered as a chronic immune-related disease. The present study addressed on the associations of immunological factors with MetS and its characteristic elements in Chinese centenarians.

METHODS

Hainan is a longevity region with the highest population density of centenarians in China. The China Hainan Centenarian Cohort Study has a considerable sample size, and provides a significant population-based sample of centenarians. Home interview, physical examination and blood analysis were conducted following standard procedures.

RESULTS

All centenarians had a median age of 102 (100-115) years, and the proportion of females was 80.8%. The proportion of centenarians with MetS was 16.0% (135 centenarians). Abdominal obesity, hypertension, dyslipidemia and diabetes mellitus had a prevalence of 26.4% (223 centenarians), 73.7% (623 centenarians), 40.4% (341 centenarians) and 10.7% (90 centenarians), respectively. In Logistic regression analyses, MetS was significantly associated with immunoglobulin E and complement C3 levels (P < 0.05 for all). Abdominal obesity was significantly associated with immunoglobulin E and complement C3 levels (P < 0.05 for all).

CONCLUSIONS

The present study provides epidemiological evidence that MetS has significant associations with immunoglobulin E and complement C3 levels, and demonstrates that abdominal obesity is significantly associated with immunoglobulin E and complement C3 levels in Chinese centenarians.

High Levels of (Un)Switched Memory B Cells Are Associated With Better Outcome in Patients With Advanced Atherosclerotic Disease

BACKGROUND

Atherosclerosis is an inflammatory lipid disorder and the main underlying pathology of acute ischemic events. Despite a vast amount of data from murine atherosclerosis models, evidence of B-cell involvement in human atherosclerotic disease is limited. We therefore investigated the association of circulating B-cell subtypes with the occurrence of secondary cardiovascular events in advanced atherosclerotic disease.

METHODS AND RESULTS

This cohort study consists of 168 patients who were included in the Athero-Express biobank between 2009 and 2011. Before surgery, peripheral blood mononuclear cells were isolated and stored in liquid nitrogen. After gentle thawing of the peripheral blood mononuclear cells, different B-cell subtypes including naïve, (un)switched memory, and CD27+CD43+ B1-like B cells, were analyzed by flow cytometry. Univariable and multivariable Cox proportional hazard models were used to analyze associations between B-cell subtypes, circulating antibodies and secondary cardiovascular manifestations during the 3-year follow-up period. Mean age was 70.1±9.6 years, males represented 62.8% of the population, and 54 patients had secondary manifestations during follow-up. High numbers of unswitched memory cells were protective against secondary outcome (hazard ratio, 0.30 [95% CI, 0.13-0.69]; P<0.01). Similar results were obtained for the switched memory cells that also showed to be protective against secondary outcome (hazard ratio, 0.33 [95% CI, 0.14-0.77]; P=0.01).

CONCLUSIONS

A high number of (un)switched memory B cells is associated with better outcome following carotid artery endarterectomy. These findings suggest a potential role for B-cell subsets in prediction and prevention of secondary cardiovascular events in patients with atherosclerosis.

Impact of high serum Immunoglobulin E levels on the risk of atherosclerosis in humans

Background

Epidemiological studies show that immunoglobulin E (IgE) levels were higher in subjects with acute coronary events. However, it is unknown if the increased IgE level is a marker of future coronary incidents and whether it may be regarded as a risk factor of an ischemic heart disease.

Objective

Our aim was to investigate the relationship between IgE levels and some atherosclerotic markers in patients without known atherosclerotic disease.

Methods

Fifty patients (mean age, 40.96 ± 10.8 years) with high serum IgE levels due to various conditions who did not display evidence of an atherosclerotic disease and 30 healthy control subjects (mean age, 47 ± 8.27 years) were included in the study. Atherosclerotic disease markers including adhesion molecules like vascular cell adhesion molecule-1, intercellular adhesion molecule-1, proinflammatory cytokines such as interleukin-6, endothelin-1, and systemic inflammatory markers such as high sensitivity C-reactive protein were determined by enzyme-linked immunosorbent assay (ELISA). Endothelial functions of the coronary arteries were determined by coronary flow reserve (CFR) measurements and carotid intima media thickness using transthoracic Doppler echocardiography.

Results

CFR was significantly lower in the patient group when compared with the control group (p<0.001; 95% confidence interval, -0.79 to-0.20) while carotid media thicknesses were not different between 2 groups. There were no differences in ELISA test results between the 2 groups.

Conclusion

Our results showed that CFR as an early marker of endothelial dysfunction was significantly lower in patients with high IgE levels. This finding seems to support the role of IgE in the vascular pathology of atherosclerosis.

Immunoglobulin M, a novel molecule of myocardial cells of mice

BACKGROUND

Immunoglobulins(Igs)play an important role in host defence and were initially thought to be expressed solely by B cells. However, recent data suggest that Igs are also expressed in other lineages. Recently, Ig transcripts were detected in cardiomyocytes, but whether the functional Ig protein is expressed by cardiomyocytes has not been thoroughly elucidated.

METHODS

Gene Expression Omnibus (GEO) microarray database analysis was used to analyse IgM heavy chain expression in the myocardium of mice. Immunohistochemistry (IHC), ELISA and Western blot were used to identify IgM in cardiomyocytes of both Balb/c mice and μMT mice (B cell-deficient mice), as well as in cultured cardiomyocytes of neonatal mice and in the myocardial cell line HL-1. Moreover, RT-PCR and cDNA sequencing were used to determine the VDJ rearrangement of the IgM heavy chain.

RESULTS

In this study, we first analysed transcription of the IgM heavy chain in heart tissue in mice by mining the GEO database, and we observed that IgM heavy chain transcripts were expressed in heart tissues. Subsequently, IgM was found to be expressed in cardiomyocytes in mice; the IgM was primarily localized on the cell membranes and intercalated discs of murine heart cells and in the cytoplasm and cell membranes of isolated cardiomyocytes and HL-1. Importantly, the functional IgM heavy chain transcripts exhibit a unique VDJ rearrangement pattern. Furthermore, IgM can be secreted and deposited in the extracellular space of the myocardium under ischaemic/hypoxic conditions.

CONCLUSIONS

Our data indicate for the first time that IgM is expressed by cardiomyocytes in mice and suggest that its physiological function warrants further investigation.

High Serum Immunoglobulin G and M Levels Predict Freedom From Adverse Cardiovascular Events in Hypertension: A Nested Case-Control Substudy of the Anglo-Scandinavian Cardiac Outcomes Trial

AIMS

We aimed to determine whether the levels of total serum IgM and IgG, together with specific antibodies against malondialdehyde-conjugated low-density lipoprotein (MDA-LDL), can improve cardiovascular risk discrimination.

METHODS AND RESULTS

The Anglo-Scandinavian Cardiac Outcomes Trial (ASCOT) randomized 9098 patients in the UK and Ireland into the Blood Pressure-Lowering Arm. 485 patients that had cardiovascular (CV) events over 5.5years were age and sex matched with 1367 controls. Higher baseline total serum IgG, and to a lesser extent IgM, were associated with decreased risk of CV events (IgG odds ratio (OR) per one standard deviation (SD) 0.80 [95% confidence interval, CI 0.72,0.89], p<0.0001; IgM 0.83[0.75,0.93], p=0.001), and particularly events due to coronary heart disease (CHD) (IgG OR 0.66 (0.57,0.76); p<0.0001, IgM OR 0.81 (0.71,0.93); p=0.002). The association persisted after adjustment for a basic model with variables in the Framingham Risk Score (FRS) as well as following inclusion of C-reactive protein (CRP) and N-terminal pro-B-type natriuretic peptide (NtProBNP). IgG and IgM antibodies against MDA-LDL were also associated with CV events but their significance was lost following adjustment for total serum IgG and IgM respectively. The area under the receiver operator curve for CV events was improved from the basic risk model when adding in total serum IgG, and there was improvement in continuous and categorical net reclassification (17.6% and 7.5% respectively) as well as in the integrated discrimination index.

CONCLUSION

High total serum IgG levels are an independent predictor of freedom from adverse cardiovascular events, particularly those attributed to CHD, in patients with hypertension.

Immune-inflammatory responses in atherosclerosis: Role of an adaptive immunity mainly driven by T and B cells

Adaptive immune response plays an important role in atherogenesis. In atherosclerosis, the proinflammatory immune response driven by Th1 is predominant but the anti-inflammatory response mediated mainly by regulatory T cells is also present. The role of Th2 and Th17 cells in atherogenesis is still debated. In the plaque, other T helper cells can be observed such as Th9 and Th22 but is little is known about their impact in atherosclerosis. Heterogeneity of CD4(+) T cell subsets presented in the plaque may suggest for plasticity of T cell that can switch the phenotype dependening on the local microenvironment and activating/blocking stimuli. Effector T cells are able to recognize self-antigens released by necrotic and apoptotic vascular cells and induce a humoral immune reaction. Tth cells resided in the germinal centers help B cells to switch the antibody class to the production of high-affinity antibodies. Humoral immunity is mediated by B cells that release antigen-specific antibodies. A variety of B cell subsets were found in human and murine atherosclerotic plaques. In mice, B1 cells could spontaneously produce atheroprotective natural IgM antibodies. Conventional B2 lymphocytes secrete either proatherogenic IgG, IgA, and IgE or atheroprotective IgG and IgM antibodies reactive with oxidation-specific epitopes on atherosclerosis-associated antigens. A small population of innate response activator (IRA) B cells, which is phenotypically intermediate between B1 and B2 cells, produces IgM but possesses proatherosclerotic properties. Finally, there is a minor subset of splenic regulatory B cells (Bregs) that protect against atherosclerotic inflammation through support of generation of Tregs and production of anti-inflammatory cytokines IL-10 and TGF-β and proapoptotic molecules.

Elevated serum complement factors 3 and 4 are strong inflammatory markers of the metabolic syndrome development: a longitudinal cohort study

An epidemiological design, consisting of cross-sectional (n = 2376) and cohort (n = 976) studies, was adopted to investigate the association between complement factors 3 (C3) and 4, and the metabolic syndrome (MetS) development. In the cross-sectional study, the C3 and C4 concentrations in the MetS group were higher than those in the non-MetS group (all P < 0.001), and the levels of immune globulin M (IgM), IgA, IgE, and IgG exhibited no significant differences between MetS and non-MetS (all P > 0.050). After multi-factor adjustment, the odds ratios (ORs) in the highest quartile of C3 and C4 concentrations were 7.047 (4.664, 10.648) and 1.961 (1.349, 2.849), respectively, both P_trend < 0.050. After a 4 years follow-up, total 166 subjects were diagnosed with MetS, and the complement baseline levels from 2009 were used to predict the MetS risk in 2013. In the adjusted model, the relative risks (RRs) in the highest quartile of C3 and C4 levels were 4.779 (2.854, 8.003) and 2.590 (1.567, 4.280), respectively, both P_trend < 0.001. Activation of complement factors may be an important part of inflammatory processes, and our results indicated that the elevated C3 and C4 levels were independent risk factors for MetS development.

B lymphocytes in abdominal aortic aneurysms

Abdominal aortic aneurysm (AAA) is a progressive inflammatory disease of the artery walls. Immune cells, including B lymphocytes, are implicated in the pathogenesis of AAA through interconnected mechanisms. Many studies have shown that compared with normal abdominal aortic tissue, the amount of B lymphocytes that infiltrate the adventitia of AAAs was significantly higher. Activated B lymphocytes promote AAA by producing immunoglobulins, cytokines, and matrix metalloproteinases (MMPs), resulting in the activation of macrophages, mast cells (MCs) and complement pathways. Finally, all of these factors lead to the degradation of collagen and matrix proteins and to aortic wall remodeling, which are hallmarks of AAA. However, few studies focus on the relative function of B cells, and their precise mechanisms in AAA remain unclear. Thus, we summarize the current knowledge on the role of B cells in AAA and offer recommendations for further investigation of preventing the progression of AAA.

Mast cells mediate neutrophil recruitment during atherosclerotic plaque progression

AIMS

Activated mast cells have been identified in the intima and perivascular tissue of human atherosclerotic plaques. As mast cells have been described to release a number of chemokines that mediate leukocyte fluxes, we propose that activated mast cells may play a pivotal role in leukocyte recruitment during atherosclerotic plaque progression.

METHODS AND RESULTS

Systemic IgE-mediated mast cell activation in apoE(-/-)μMT mice resulted in an increase in atherosclerotic lesion size as compared to control mice, and interestingly, the number of neutrophils was highly increased in these lesions. In addition, peritoneal mast cell activation led to a massive neutrophil influx into the peritoneal cavity in C57Bl6 mice, whereas neutrophil numbers in mast cell deficient Kit(W(-sh)/W(-sh)) mice were not affected. Within the newly recruited neutrophil population, increased levels of CXCR2(+) and CXCR4(+) neutrophils were observed after mast cell activation. Indeed, mast cells were seen to contain and release CXCL1 and CXCL12, the ligands for CXCR2 and CXCR4. Intriguingly, peritoneal mast cell activation in combination with anti-CXCR2 receptor antagonist resulted in decreased neutrophil recruitment, thus establishing a prominent role for the CXCL1/CXCR2 axis in mast cell-mediated neutrophil recruitment.

CONCLUSIONS

Our data suggest that chemokines, and in particular CXCL1, released from activated mast cells induce neutrophil recruitment to the site of inflammation, thereby aggravating the ongoing inflammatory response and thus affecting plaque progression and destabilization.

The impact of mast cells on cardiovascular diseases

Mast cells comprise an innate immune cell population, which accumulates in tissues proximal to the outside environment and, upon activation, augments the progression of immunological reactions through the release and diffusion of either pre-formed or newly generated mediators. The released products of mast cells include histamine, proteases, as well as a variety of cytokines, chemokines and growth factors, which act on the surrounding microenvironment thereby shaping the immune responses triggered in various diseased states. Mast cells have also been detected in the arterial wall and are implicated in the onset and progression of numerous cardiovascular diseases. Notably, modulation of distinct mast cell actions using genetic and pharmacological approaches highlights the crucial role of this cell type in cardiovascular syndromes. The acquired evidence renders mast cells and their mediators as potential prognostic markers and therapeutic targets in a broad spectrum of pathophysiological conditions related to cardiovascular diseases.

Selective IgE deficiency and cardiovascular diseases

Selective immunoglobulin E (IgE) deficiency (IgED) is defined as serum levels of IgE more than or equal to 2 kIU/L and is associated with immune dysregulation and autoimmunity. This study aimed to investigate a prevalence of atherosclerotic cardiovascular disease (ASCVD) in population with IgED. Within the electronic patient record (EPR) database of Leumit Health Care Services (LHS) in Israel, data capture was performed using IBM Cognos 10.1.1 BI Report Studio software. The case samples were drawn from the full study population (n = 18,487), having any allergy-related symptoms and/or those requesting antiallergy medications and performed serum total IgE measurement during 2012 at LHS. All subjects aged more than or equal to 40 years old, with serum total IgE less than 2 kIU/L were included in case group. Control group was randomly sampled from the remained subjects, with a case-control ratio of 10 controls for each case (1:10). The comorbid cardiovascular diseases during less than or equal to 10 years before serum total IgE testing were identified and retrieved using specific International Classification of Diseases, 9th Revision, Clinical Modification diagnostic codes. There were 103 in case and 1030 subjects in control group. Compared with control group patients, the case group had significantly more arterial hypertension [34 (37.7%) versus 187 (18.2%), p < 0.001], ischemic heart disease (IHD) [26 (25.2%) versus 87 (8.4%), p < 0.001], carotid stenosis [5 (4.9%) versus 7 (0.7%), p = 0.003], cerebrovascular disease (CVD) [3 (2.9%) versus 5 (0.5%), p = 0.029], and peripheral vascular disease (PVD) [4 (3.9%) versus 9 (0.9%), p = 0.024]. IgED is associated with higher prevalence of arterial hypertension and ASCVD.

Inflammatory mediators in vascular disease: identifying promising targets for intracranial aneurysm research

Inflammatory processes are implicated in many diseases of the vasculature and have been shown to play a key role in the formation of intracranial aneurysms (IAs). Although the specific mechanisms underlying these processes have been thoroughly investigated in related pathologies, such as atherosclerosis, there remains a paucity of information regarding the immunopathology of IA. Cells such as macrophages and lymphocytes and their effector molecules have been suggested to be players in IA, but their specific interactions and the role of other components of the inflammatory response have yet to be determined. Drawing parallels between the pathogenesis of IA and other vascular disorders could provide a roadmap for developing a mechanistic understanding of the immunopathology of IA and uncovering useful targets for therapeutic intervention. Future research should address the presence and function of leukocyte subsets, mechanisms of leukocyte recruitment and activation, and the role of damage-associated molecular patterns in IA.

The role of T and B cells in human atherosclerosis and atherothrombosis

Far from being merely a passive cholesterol accumulation within the arterial wall, the development of atherosclerosis is currently known to imply both inflammation and immune effector mechanisms. Adaptive immunity has been implicated in the process of disease initiation and progression interwined with traditional cardiovascular risk factors. Although the body of knowledge regarding the correlation between atherosclerosis and immunity in humans is growing rapidly, a relevant proportion of it derives from studies carried out in animal models of cardiovascular disease (CVD). However, while the mouse is a well-suited model, the results obtained therein are not fully transferrable to the human setting due to intrinsic genomic and environmental differences. In the present review, we will discuss mainly human findings, obtained either by examination of post-mortem and surgical atherosclerotic material or through the analysis of the immunological profile of peripheral blood cells. In particular, we will discuss the findings supporting a pro-atherogenic role of T cell subsets, such as effector memory T cells or the potential protective function of regulatory T cells. Recent studies suggest that traditional T cell-driven B2 cell responses appear to be atherogenic, while innate B1 cells appear to exert a protective action through the secretion of naturally occurring antibodies. The insights into the immune pathogenesis of atherosclerosis can provide new targets in the quest for novel therapeutic targets to abate CVD morbidity and mortality.

Immunological Aspects of Atherosclerosis

Atherosclerosis is a degenerative inflammatory disease of the vascular wall, which is characterized by the formation of atherosclerotic plaques that contain lipids, activated smooth muscle cells, immune cells, foam cells, a necrotic core and calcified sites. In atherosclerosis pathology, monocytes and macrophages play the most important role by accumulating redundant LDL particles in their oxidized form and producing proinflammatory cytokines. Atherosclerotic plaque macrophages reveal distinct phenotypes that are distinguished into M1 (pro-inflammatory) and M2 (anti-inflammatory) macrophages. Numerous environmental signals (cytokines, microbial cell molecules) that are received by macrophages drive their polarization, but it must be determined whether this classification reflects different macrophage subtypes or plasticity and phenotypic tissue changes, but the balance between subsets is crucial. M1 macrophages are dominant in symptomatic atherosclerotic plaques, while M2 macrophages are more frequent in asymptomatic plaques. Nevertheless, a positive correlation of both M1 and M2 macrophages with atherosclerotic lesion severity was also observed.

The role of mast cells in atherosclerosis

Rupture of an atherosclerotic plaque is the major underlying cause of adverse cardiovascular events such as myocardial infarction or stroke. Therapeutic interventions should therefore be directed towards inhibiting growth of atherosclerotic lesions as well as towards prevention of lesion destabilization. Interestingly, the presence of mast cells has been demonstrated in both murine and human plaques, and multiple interventional murine studies have pointed out a direct role for mast cells in early and late stages of atherosclerosis. Moreover, it has recently been described that activated lesional mast cells correlate with major cardiovascular events in patients suffering from cardiovascular disease. This review focuses on the effect of different mast cell derived mediators in atherogenesis and in late stage plaque destabilization. Also, possible ligands for mast cell activation in the context of atherosclerosis are discussed. Finally, we will elaborate on the predictive value of mast cells, together with therapeutic implications, in cardiovascular disease.

Immunoglobulin E (IgE) and ischemic heart disease. Which came first, the chicken or the egg?

Several lines of evidence demonstrate that the immune system plays a pivotal role in development and progression of ischemic heart disease (IHD). More recently, a series of biological and clinical investigations has generated new interest about the existence of a relationship between a specific class of immunoglobulin, that is immunoglobulin E (IgE), and IHD. Data obtained in several epidemiological studies have convincingly demonstrated that the concentration of total serum IgEs is significantly increased in patients with IHD and often correlates with the prognosis. The putative mechanisms are essentially mediated by a physiological interaction between IgEs and mast cells, which triggers the direct or indirect release of a variety of substances that are actively involved in the pathogenesis of myocardial ischemia and thrombosis. Regardless of these important evidences, a causality dilemma remains, since it is still unclear whether increased IgE levels are a consequence of IHD or, rather, IHD is an underlying cause of increased IgE levels. The answer would allow us to recognize whether total IgEs may be considered simple biomarkers or risk factors of IHD, thus paving the way to investigations focused on immunotherapy or avoidance of allergenic foods for reducing serum IgEs in patients at risk of IHD.

Targeting B cells in atherosclerosis: closing the gap from bench to bedside

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.

Mast cells as effectors in atherosclerosis

The mast cell is a potent immune cell known for its functions in host defense responses and diseases, such as asthma and allergies. In the past years, accumulating evidence established the contribution of the mast cell to cardiovascular diseases as well, in particular, by its effects on atherosclerotic plaque progression and destabilization. Through its release not only of mediators, such as the mast cell-specific proteases chymase and tryptase, but also of growth factors, histamine, and chemokines, activated mast cells can have detrimental effects on its immediate surroundings in the vessel wall. This results in matrix degradation, apoptosis, and enhanced recruitment of inflammatory cells, thereby actively contributing to cardiovascular diseases. In this review, we will discuss the current knowledge on mast cell function in cardiovascular diseases and speculate on potential novel therapeutic strategies to prevent acute cardiovascular syndromes via targeting of mast cells.

B cells and humoral immunity in atherosclerosis

Insights into the important contribution of inflammation and immune functions in the development and progression of atherosclerosis have greatly improved our understanding of this disease. Although the role of T cells has been extensively studied for decades, only recently has the role of B cells gained more attention. Recent studies have identified differential effects of different B-cell subsets and helped to clarify the still poorly understood mechanisms by which these act. B1 cells have been shown to prevent lesion formation, whereas B2 cells have been suggested to promote it. Natural IgM antibodies, mainly derived from B1 cells, have been shown to mediate atheroprotective effects, but the functional role of other immunoglobulin classes, particularly IgG, still remains elusive. In this review, we will focus on recent insights on the role of B cells and various immunoglobulin classes and how these may mediate their effects in atherosclerotic lesion formation. Moreover, we will highlight potential therapeutic approaches focusing on B-cell depletion that could be used to translate experimental evidence to human disease.

Lymphocytes and immunoglobulin patterns across the threshold of severe obesity

The proinflammatory state of metabolic disorders encompasses the alterations in leukocyte counts and acute-phase reactants, and thus, predisposes to acute and chronic cardiovascular events linked to fat accumulation. Leptin is a marker of adiposity and also yields regulatory effects on innate and adaptive immunity; however, its role on the immune function of obese subjects remains to be elucidated. The aim of this study is to determine the influence of obesity and the role of leptin concentrations on lymphocyte counts and immunoglobulin levels as broad markers of immune function. Cross-sectional analysis in 147 obese (64 M, BMI 43 ± 8.1 kg/m(2)) and 111 age- and sex-matched controls (36 M, BMI 22.5 ± 2.6 kg/m(2)) by assessment of peripheral leukocyte counts, immunoglobulin (Ig) A, G, M levels, leptin, glucose and lipid homeostasis, and acute-phase reactants. Compared to controls, all the leukocyte components were significantly increased in obesity (p < 0.0001 for all) except for basophils and eosinophils. While IgA and IgG levels were similar between groups, IgM levels were lower (p < 0.001) in obese individuals. A significant relationship was evident between leptin and leukocyte counts (p < 0.001), with this latter being correlated to insulin resistance, adiposity, and lipid profile. At the stepwise multiple regression analysis, leukocytes were best predicted by leptin (β = 0.43, p < 0.0001) and male gender (β = 0.15, p < 0.05), yet when obesity entered the equation, it acted as an independent predictor of leukocytes (β = 0.51, p < 0.0001). Leptin also acted as a predictor of IgA levels (β = 0.20, p < 0.01). Current results show that IgM levels are significantly decreased in patients with obesity in association to significant increments in leukocyte counts. These latter are markedly correlated to leptin levels, insulin resistance, lipid profile, and adiposity. This circumstance, and the significant correlation seen between leptin and IgA levels, may suggest an indirect intervention of leptin in the immunologic alterations consequent to obesity and related to its cardiovascular risk.

Circulating immunoglobulins are not associated with intraplaque mast cell number and other vulnerable plaque characteristics in patients with carotid artery stenosis

Background

Recently, we have shown that intraplaque mast cell numbers are associated with atherosclerotic plaque vulnerability and with future cardiovascular events, which renders inhibition of mast cell activation of interest for future therapeutic interventions. However, the endogenous triggers that activate mast cells during the progression and destabilization of atherosclerotic lesions remain unidentified. Mast cells can be activated by immunoglobulins and in the present study, we aimed to establish whether specific immunoglobulins in plasma of patients scheduled for carotid endarterectomy were related to (activated) intraplaque mast cell numbers and plasma tryptase levels. In addition, the levels were related to other vulnerable plaque characteristics and baseline clinical data.

Methods and Results

OxLDL-IgG, total IgG and total IgE levels were measured in 135 patients who underwent carotid endarterectomy. No associations were observed between the tested plasma immunoglobulin levels and total mast cell numbers in atherosclerotic plaques. Furthermore, no associations were found between IgG levels and the following plaque characteristics: lipid core size, degree of calcification, number of macrophages or smooth muscle cells, amount of collagen and number of microvessels. Interestingly, statin use was negatively associated with plasma IgE and oxLDL-IgG levels.

Conclusions

In patients suffering from carotid artery disease, total IgE, total IgG and oxLDL-IgG levels do not associate with plaque mast cell numbers or other vulnerable plaque histopathological characteristics. This study thus does not provide evidence that the immunoglobulins tested in our cohort play a role in intraplaque mast cell activation or grade of atherosclerosis.