Natural antibodies with the T15 idiotype may act in atherosclerosis, apoptotic clearance, and protective immunity

B cells in non-lymphoid tissues

B cells have long been understood to be drivers of both humoral and cellular immunity. Recent advances underscore this importance but also indicate that in infection, inflammatory disease and cancer, B cells function directly at sites of inflammation and form tissue-resident memory populations. The spatial organization and cellular niches of tissue B cells have profound effects on their function and on disease outcome, as well as on patient response to therapy. Here we review the role of B cells in peripheral tissues in homeostasis and disease, and discuss the newly identified cellular and molecular signals that are involved in regulating their activity. We integrate emerging data from multi-omic human studies with experimental models to propose a framework for B cell function in tissue inflammation and homeostasis.

Immunomodulation for accelerated atherosclerosis in rheumatoid arthritis and systemic lupus erythematosus

In the last decades, consisting evidence supported a close relationship between both innate and adaptive immune systems and the accelerated cardiovascular (CV) disease characterizing autoimmune diseases, such as systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). Indeed, several cell lines involved in the pathogenesis of these autoimmune diseases, such as macrophages and dendritic cells, as well as different T and B lymphocyte subsets, and inflammatory cytokines, have been demonstrated to be directly involved in the mechanisms underlying early atherosclerotic arterial wall damage. Traditional CV risk factors play a concomitant role but do not sufficiently account for the increased prevalence of CV disease in these patients. Indeed, the pathophysiological link between RA and SLE and atherosclerosis is based on complex inflammatory pathways that interconnect these conditions and may explain the significant morbidity and mortality rates demonstrated in these patients, with consequent significant negative effects on quality of life and long-term survival. Consequently, it is intriguing to hypothesize that immunosuppressive drugs commonly used in the treatment of these pathologies may also exert an immunomodulatory and anti-inflammatory effect in mitigating the atherosclerotic damage that has been demonstrated to occur early in the initial stages of the disease. Recognizing risk factors, predicting occurrences and early intervention to prevent CV disease development have emerged as critical objectives in RA and SLE treatment. In this review, we aimed to provide an updated overview of the atherogenic effects exerted by the immune and inflammatory pathways involved in the pathogenesis of RA and SLE. Moreover, we examined the available evidence which may support the potential effects of immunosuppressive therapies in reducing CV damage and, consequently, CV disease risk in these patients.

Identification of plasma proteins binding oxidized phospholipids using pull-down proteomics and OxLDL masking assay

Oxidized phospholipids (OxPLs) are increasingly recognized as toxic and proinflammatory mediators, which raises interest in the mechanisms of their detoxification. Circulating OxPLs are bound and neutralized by plasma proteins, including both antibodies and non-immunoglobulin proteins. The latter group of proteins is essentially not investigated because only three OxPC-binding plasma proteins are currently known. The goal of this work was to characterize a broad spectrum of plasma proteins selectively binding OxPLs. Using pull-down-proteomic analysis, we found about 150 non-immunoglobulin proteins preferentially binding oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-phosphatidylcholine (OxPAPC) as compared to non-oxidized PAPC. To test if candidate proteins indeed can form a barrier isolating OxPLs from recognition by other proteins, we applied an immune masking assay. Oxidized LDL (OxLDL) immobilized in multiwell plates was used as a carrier of OxPLs, while mAbs recognizing OxPC or OxPE were used as "detectors" showing if OxPLs on the surface of OxLDL are physically accessible to external binding partners. Using an orthogonal combination of pull-down and masking assays we confirmed that previously described OxPL-binding proteins (non-fractionated IgM, CFH, and Apo-M) indeed can bind to and mask OxPC and OxPE on liposomes and OxLDL. Furthermore, we identified additional plasma proteins selectively binding and masking OxPC including Apo-D, Apo-H, pulmonary surfactant-associated protein B, and antithrombin-III. We hypothesize that in addition to circulating antibodies, multiple non-immunoglobulin plasma proteins can also bind OxPLs and modulate their recognition by innate and adaptive immunity.

Autoimmune diseases and atherosclerotic cardiovascular disease

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.

Role of Antibodies and Their Specificities in Atherosclerotic Cardiovascular Disease

Atherosclerosis is a lipid-driven chronic inflammatory disease that is modulated by innate and adaptive immunity including humoral immunity. Importantly, antibody alterations achieved by genetic means or active and passive immunization strategies in preclinical studies can improve or aggravate atherosclerosis. Additionally, a wide range of epidemiological data demonstrate not only an association between the total levels of different antibody isotypes but also levels of antibodies targeting specific antigens with atherosclerotic cardiovascular disease. Here, we discuss the potential role of atherogenic dyslipidemia on the antibody repertoire and review potential antibody-mediated effector mechanisms involved in atherosclerosis development highlighting the major atherosclerosis-associated antigens that trigger antibody responses.

Tipping the Scale: Atheroprotective IgM-Producing B Cells in Atherosclerosis

Atherosclerosis is a chronic inflammatory disease whose progression is fueled by proinflammatory moieties and limited by anti-inflammatory mediators. Whereas oxidative damage and the generation of oxidation-specific epitopes that act as damage-associated molecular patterns are highly inflammatory, IgM antibodies produced by B-1 and marginal zone B cells counteract unrestricted inflammation by neutralizing and encouraging clearance of these proinflammatory signals. In this review, we focus on describing the identities of IgM-producing B cells in both mice and humans, elaborating the mechanisms underlying IgM production, and discussing the potential strategies to augment the production of atheroprotective IgM. In addition, we will discuss promising therapeutic interventions in humans to help tip the scale toward augmentation of IgM production and to provide atheroprotection.

B Cells of Early-life Origin Defined by RAG2-based Lymphoid Cell Tracking under Native Hematopoietic Conditions

During the perinatal period, the immune system sets the threshold to select either response or tolerance to environmental Ags, which leads to the potential to provide a lifetime of protection and health. B-1a B cells have been demonstrated to develop during this perinatal time window, showing a unique and restricted BCR repertoire, and these cells play a major role in natural Ab secretion and immune regulation. In the current study, we developed a highly efficient temporally controllable RAG2-based lymphoid lineage cell labeling and tracking system and applied this system to understand the biological properties and contribution of B-1a cells generated at distinct developmental periods to the adult B-1a compartments. This approach revealed that B-1a cells with a history of RAG2 expression during the embryonic and neonatal periods dominate the adult B-1a compartment, including those in the bone marrow (BM), peritoneal cavity, and spleen. Moreover, the BCR repertoire of B-1a cells with a history of RAG2 expression during the embryonic period was restricted, becoming gradually more diverse during the neonatal period, and then heterogeneous at the adult stage. Furthermore, more than half of plasmablasts/plasma cells in the adult BM had embryonic and neonatal RAG2 expression histories. Moreover, BCR analysis revealed a high relatedness between BM plasmablasts/plasma cells and B-1a cells derived from embryonic and neonatal periods, suggesting that these cell types have a common origin. Taken together, these findings define, under native hematopoietic conditions, the importance in adulthood of B-1a cells generated during the perinatal period.

A protective role for B-1 cells and oxidation-specific epitope IgM in lung fibrosis

Idiopathic pulmonary fibrosis (IPF) is a morbid fibrotic lung disease with limited treatment options. The pathophysiology of IPF remains poorly understood, and elucidation of the cellular and molecular mechanisms of IPF pathogenesis is key to the development of new therapeutics. B-1 cells are an innate B cell population which play an important role linking innate and adaptive immunity. B-1 cells spontaneously secrete natural IgM and prevent inflammation in several disease states. One class of these IgM recognize oxidation-specific epitopes (OSE), which have been shown to be generated in lung injury and to promote fibrosis. A main B-1 cell reservoir is the pleural space, adjacent to the typical distribution of fibrosis in IPF. In this study, we demonstrate that B-1 cells are recruited to the lung during injury where they secrete IgM to OSE (IgM OSE ). We also show that the pleural B-1 cell reservoir responds to lung injury through regulation of the chemokine receptor CXCR4. Mechanistically we show that the transcription factor Id3 is a novel negative regulator of CXCR4 expression. Using mice with B-cell specific Id3 deficiency, a model of increased B-1b cells, we demonstrate decreased bleomycin-induced fibrosis compared to littermate controls. Furthermore, we show that mice deficient in secretory IgM ( sIgM -/- ) have higher mortality in response to bleomycin-induced lung injury, which is partially mitigated through airway delivery of the IgM OSE E06. Additionally, we provide insight into potential mechanisms of IgM in attenuation of fibrosis through RNA sequencing and pathway analysis, highlighting complement activation and extracellular matrix deposition as key differentially regulated pathways.

The role of B-1 cells in cancer progression and anti-tumor immunity

In recent years, in addition to the well-established role of T cells in controlling or promoting tumor growth, a new wave of research has demonstrated the active involvement of B cells in tumor immunity. B-cell subsets with distinct phenotypes and functions play various roles in tumor progression. Plasma cells and activated B cells have been linked to improved clinical outcomes in several types of cancer, whereas regulatory B cells have been associated with disease progression. However, we are only beginning to understand the role of a particular innate subset of B cells, referred to as B-1 cells, in cancer. Here, we summarize the characteristics of B-1 cells and review their ability to infiltrate tumors. We also describe the potential mechanisms through which B-1 cells suppress anti-tumor immune responses and promote tumor progression. Additionally, we highlight recent studies on the protective anti-tumor function of B-1 cells in both mouse models and humans. Understanding the functions of B-1 cells in tumor immunity could pave the way for designing more effective cancer immunotherapies.

Loss of TET2 increases B-1 cell number and IgM production while limiting CDR3 diversity

Recent studies have demonstrated a role for Ten-Eleven Translocation-2 (TET2), an epigenetic modulator, in regulating germinal center formation and plasma cell differentiation in B-2 cells, yet the role of TET2 in regulating B-1 cells is largely unknown. Here, B-1 cell subset numbers, IgM production, and gene expression were analyzed in mice with global knockout of TET2 compared to wildtype (WT) controls. Results revealed that TET2-KO mice had elevated numbers of B-1a and B-1b cells in their primary niche, the peritoneal cavity, as well as in the bone marrow (B-1a) and spleen (B-1b). Consistent with this finding, circulating IgM, but not IgG, was elevated in TET2-KO mice compared to WT. Analysis of bulk RNASeq of sort purified peritoneal B-1a and B-1b cells revealed reduced expression of heavy and light chain immunoglobulin genes, predominantly in B-1a cells from TET2-KO mice compared to WT controls. As expected, the expression of IgM transcripts was the most abundant isotype in B-1 cells. Yet, only in B-1a cells there was a significant increase in the proportion of IgM transcripts in TET2-KO mice compared to WT. Analysis of the CDR3 of the BCR revealed an increased abundance of replicated CDR3 sequences in B-1 cells from TET2-KO mice, which was more clearly pronounced in B-1a compared to B-1b cells. V-D-J usage and circos plot analysis of V-J combinations showed enhanced usage of VH11 and VH12 pairings. Taken together, our study is the first to demonstrate that global loss of TET2 increases B-1 cell number and IgM production and reduces CDR3 diversity, which could impact many biological processes and disease states that are regulated by IgM.

Oxidized phospholipids in cardiovascular disease

Prolonged or excessive exposure to oxidized phospholipids (OxPLs) generates chronic inflammation. OxPLs are present in atherosclerotic lesions and can be detected in plasma on apolipoprotein B (apoB)-containing lipoproteins. When initially conceptualized, OxPL-apoB measurement in plasma was expected to reflect the concentration of minimally oxidized LDL, but, surprisingly, it correlated more strongly with plasma lipoprotein(a) (Lp(a)) levels. Indeed, experimental and clinical studies show that Lp(a) particles carry the largest fraction of OxPLs among apoB-containing lipoproteins. Plasma OxPL-apoB levels provide diagnostic information on the presence and extent of atherosclerosis and improve the prognostication of peripheral artery disease and first and recurrent myocardial infarction and stroke. The addition of OxPL-apoB measurements to traditional cardiovascular risk factors improves risk reclassification, particularly in patients in intermediate risk categories, for whom improving decision-making is most impactful. Moreover, plasma OxPL-apoB levels predict cardiovascular events with similar or greater accuracy than plasma Lp(a) levels, probably because this measurement reflects both the genetics of elevated Lp(a) levels and the generalized or localized oxidation that modifies apoB-containing lipoproteins and leads to inflammation. Plasma OxPL-apoB levels are reduced by Lp(a)-lowering therapy with antisense oligonucleotides and by lipoprotein apheresis, niacin therapy and bariatric surgery. In this Review, we discuss the role of role OxPLs in the pathophysiology of atherosclerosis and Lp(a) atherogenicity, and the use of OxPL-apoB measurement for improving prognosis, risk reclassification and therapeutic interventions.

Knowledge mapping of B cell and atherosclerosis over the past 20 years: A bibliometric analysis

Atherosclerosis (AS) is the main underlying cause of cardiovascular disease, and B cells are considered a key immune cell type to regulate AS. So far, there is no bibliometric study on B cell and AS. This study aims to comprehensively analyze the scientific output about B cell and AS, summarize the literature characteristics, explore research hotspots, and point out emerging trends. We searched the literature from 2003 to 2022 from the Web of Science Core Collection (WoSCC) database. CiteSpace, VOSviewer, and the R package "Bibliometrix" were used for literature analysis and visualization. A total of 1,062 articles and reviews were identified. The number of annual publications generally showed an upward trend. The United States and China were the most productive countries. Medical University of Vienna was the most productive research institution, and Binder Christoph J. was the most productive author, who was also from Medical University of Vienna. "Arteriosclerosis Thrombosis and Vascular Biology" was the most published journal and the most frequently cited journal. The most cited reference was written by Caligiuri G (2002) in "Journal of Clinical Investigation." The most frequent keywords were "inflammation," "macrophages," "cardiovascular disease," "T cells," "apoptosis," "immunity," "cytokines," "lymphocytes," etc. The trend topics were mainly focused on "immune infiltration," "immunoglobulins," and "biomarkers." The complex role of B cell subtypes and a variety of B cell mediators is the main research direction at present. In-depth analysis of B cell-specific targets can provide new ideas and methods for the prevention and treatment of AS.

Atherosclerosis antigens as targets for immunotherapy

Atherosclerosis is a chronic inflammatory disease of the arteries that can lead to thrombosis, infarction and stroke, underlying the first cause of mortality worldwide. Adaptive immunity plays critical roles in atherosclerosis, and numerous studies have ascribed both atheroprotective and atherogenic functions to specific subsets of T and B cells. However, less is known on how antigen specificity determines the protective or adverse outcome of such adaptive responses. Understanding antigen triggers in atherosclerosis is crucial to delve deeper into mechanisms of disease initiation and progression and to implement specific immunotherapeutic approaches, including vaccination strategies. Here we review the role of adaptive immunity in atherosclerosis and the insights that single-cell technology has provided into the function of distinct immune cell subsets. We outline the most relevant atherosclerosis antigens and antibodies reported to date and examine their immunotherapeutic potential. Finally, we review the most promising vaccination-based clinical trials targeting the adaptive immune system.

Enhancers within the Ig V Gene Region Orchestrate Chromatin Topology and Regulate V Gene Rearrangement Frequency to Shape the B Cell Receptor Repertoire Specificities

Effective Ab-mediated responses depend on a highly diverse Ab repertoire with the ability to bind a wide range of epitopes in disease-causing agents. The generation of this repertoire depends on the somatic recombination of the variable (V), diversity (D), and joining (J) genes in the Ig loci of developing B cells. It has been known for some time that individual V, D, and J gene segments rearrange at different frequencies, but the mechanisms behind this unequal V gene usage have not been well understood. However, recent work has revealed that newly described enhancers scattered throughout the V gene-containing portion of the Ig loci regulate the V gene recombination frequency in a regional manner. Deletion of three of these enhancers revealed that these elements exert many layers of control during V(D)J recombination, including long-range chromatin interactions, epigenetic milieu, chromatin accessibility, and compartmentalization.

Human circulating CD24hi marginal zone B cells produce IgM targeting atherogenic antigens and confer protection from vascular disease

IgMs that inactivate oxidation-specific epitopes (IgMOSE), which are secondary products of lipid peroxidization, protect against inflammatory diseases, including diet-induced atherosclerosis. However, the human B cell subtype that produces IgMOSE remains unknown. In this study, we used single-cell mass cytometry and adoptive transfer of B cell subtypes to NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ (NSG) mice to identify B27+IgM+CD24hi cells as the major producers of IgMOSE in humans. Notably, these cells have characteristics of human circulatory marginal zone B (MZB) cells, which are known to be atheoroprotective IgM producers in mice. CD24 antibody treatment to reduce MZB cells and IgM in a hyperlipidemic humanized mouse model provides the evidence that MZB cells protect against vascular inflammation. Consistent with these findings, the frequency of B27+IgM+CD24hi cells (MZB) in patients inversely correlates with coronary artery disease severity.

Stages, pathogenesis, clinical management and advancements in therapies of age-related macular degeneration

Age-related macular degeneration (AMD) is a retinal degenerative disorder prevalent in the elderly population, which leads to the loss of central vision. The disease progression can be managed, if not prevented, either by blocking neovascularization ("wet" form of AMD) or by preserving retinal pigment epithelium and photoreceptor cells ("dry" form of AMD). Although current therapeutic modalities are moderately successful in delaying the progression and management of the disease, advances over the past years in regenerative medicine using iPSC, embryonic stem cells, advanced materials (including nanomaterials) and organ bio-printing show great prospects in restoring vision and efficient management of either forms of AMD. This review focuses on the molecular mechanism of the disease, model systems (both cellular and animal) used in studying AMD, the list of various regenerative therapies and the current treatments available. The article also highlights on the recent clinical trials using regenerative therapies and management of the disease.

Homeostatic role of B-1 cells in tissue immunity

To date, studies of tissue-resident immunity have mainly focused on innate immune cells and T cells, with limited data on B cells. B-1 B cells are a unique subset of B cells with innate-like properties, enriched in murine pleural and peritoneal cavities and distinct from conventional B-2 cells in their ontogeny, phenotype and function. Here we discuss how B-1 cells represent exemplar tissue-resident immune cells, summarizing the evidence for their long-term persistence & self-renewal within tissues, differential transcriptional programming shaped by organ-specific environmental cues, as well as their tissue-homeostatic functions. Finally, we review the emerging data supporting the presence and homeostatic role of B-1 cells across non-lymphoid organs (NLOs) both in mouse and human.

Increased extracellular vesicles (EVs) related to T cell-mediated inflammation and vascular function in familial hypercholesterolemia

Background and aims

OxLDL modulates innate and adaptive immunity, and extracellular vesicles (EVs) released from both non-immune and immune cells are proposed key players in atherosclerosis development. In the present study, we aimed to investigate EVs expressing markers related to adaptive immunity-driven inflammation and endothelial activation/dysfunction in hypercholesterolemic patients.

Methods

EVs were phenotyped in thirty patients with familial hypercholesterolemia (FH) and twenty-three healthy controls using the Extracellular Vesicle (EV) Array with antibodies targeting proteins expressed on B and T cells, and endothelial cells.

Results

FH patients had a higher atherosclerotic burden, as determined by the mean carotid intima-media thickness (IMT) (0.64 ± 0.12 mm vs. 0.58 ± 0.07 mm; p = 0.033), higher oxLDL levels (p < 0.0001), and showed increased levels of EV-specific markers: CD9 (p = 0.017), CD63 (p = 0.045), CD81 (p = 0.003), Annexin V (p = 0.018), and EV markers related to adaptive/lymphocyte immunity: CD28 (p = 0.034), CD4 (p = 0.049), CD152 (p = 0.029), LFA-1 (p = 0.024), and endothelial function: CD62E (p = 0.032), CD144 (p = 0.018), tPA (p = 0.017), CD31 (p = 0.024). Linear regression revealed a positive relationship between carotid IMT and several of the increased markers observed within the FH group, including CD9 (β = 0.33; p = 0.022), CD63 (β = 0.35; p 225 = 0.026), CD28 (β = 0.37; p = 0.026), CD4 (β = 0.40; p = 0.025), CD152 (β = 0.41; p = 0.017), LFA-1 (β = 0.42; p = 0.014) and CD62E (β = 0.38; p = 0.024).

Conclusion

EVs associated with adaptive immunity and endothelial dysfunction are elevated in FH patients, and several markers related to a higher atherosclerotic burden.

Immunometabolism and immune response regulate macrophage function in atherosclerosis

Macrophages are crucial in the progression of atherosclerotic cardiovascular disease (ASCVD). In the atherosclerotic lesions, macrophages play a central role in maintaining inflammatory response, promoting plaque development, and facilitating thrombosis. Increasing studies indicate that metabolic reprogramming and immune response mediate macrophage functional changes in all stages of atherosclerosis. In this review article, we explain how metabolic changes in glycolysis, oxidative phosphorylation, the tricarboxylic acid cycle, fatty acid synthesis, fatty acid oxidation, and cholesterol metabolism regulate macrophage function in atherosclerosis. We discuss how immune response to oxidized lipids regulate macrophage function in atherosclerosis. Additionally, we explore how abnormal metabolism leads to macrophage mitochondrial dysfunction in atherosclerosis.

Targeting foam cell formation to improve recovery from ischemic stroke

Inflammation is a crucial part of the healing process after an ischemic stroke and is required to restore tissue homeostasis. However, the inflammatory response to stroke also worsens neurodegeneration and creates a tissue environment that is unfavorable to regeneration for several months, thereby postponing recovery. In animal models, inflammation can also contribute to the development of delayed cognitive deficits. Myeloid cells that take on a foamy appearance are one of the most prominent immune cell types within chronic stroke infarcts. Emerging evidence indicates that they form as a result of mechanisms of myelin lipid clearance becoming overwhelmed, and that they are a key driver of the chronic inflammatory response to stroke. Therefore, targeting lipid accumulation in foam cells may be a promising strategy for improving recovery. The aim of this review is to provide an overview of current knowledge regarding inflammation and foam cell formation in the brain in the weeks and months following ischemic stroke and identify targets that may be amenable to therapeutic intervention.

B-1 cells in immunotoxicology: Mechanisms underlying their response to chemicals and particles

Since their discovery nearly 40 years ago, B-1 cells have continued to challenge the boundaries between innate and adaptive immunity, as well as myeloid and lymphoid functions. This B-cell subset ensures early immunity in neonates before the development of conventional B (B-2) cells and respond to immune injuries throughout life. B-1 cells are multifaceted and serve as natural- and induced-antibody-producing cells, phagocytic cells, antigen-presenting cells, and anti-/pro-inflammatory cytokine-releasing cells. This review retraces the origin of B-1 cells and their different roles in homeostatic and infectious conditions before focusing on pollutants comprising contact-sensitivity-inducing chemicals, endocrine disruptors, aryl hydrocarbon receptor (AHR) ligands, and reactive particles.

Group 2 Innate Lymphoid Cells Protect Mice from Abdominal Aortic Aneurysm Formation via IL5 and Eosinophils

Development of abdominal aortic aneurysms (AAA) enhances lesion group-2 innate lymphoid cell (ILC2) accumulation and blood IL5. ILC2 deficiency in Rorafl/fl Il7rCre/+ mice or induced ILC2 depletion in Icosfl-DTR-fl/+ Cd4Cre/+ mice expedites AAA growth, increases lesion inflammation, but leads to systemic IL5 and eosinophil (EOS) deficiency. Mechanistic studies show that ILC2 protect mice from AAA formation via IL5 and EOS. IL5 or ILC2 from wild-type (WT) mice, but not ILC2 from Il5-/- mice induces EOS differentiation in bone-marrow cells from Rorafl/fl Il7rCre/+ mice. IL5, IL13, and EOS or ILC2 from WT mice, but not ILC2 from Il5-/- and Il13-/- mice block SMC apoptosis and promote SMC proliferation. EOS but not ILC2 from WT or Il5-/- mice block endothelial cell (EC) adhesion molecule expression, angiogenesis, dendritic cell differentiation, and Ly6Chi monocyte polarization. Reconstitution of WT EOS and ILC2 but not Il5-/- ILC2 slows AAA growth in Rorafl/fl Il7rCre/+ mice by increasing systemic EOS. Besides regulating SMC pathobiology, ILC2 play an indirect role in AAA protection via the IL5 and EOS mechanism.

Enhancer-instructed epigenetic landscape and chromatin compartmentalization dictate a primary antibody repertoire protective against specific bacterial pathogens

Antigen receptor loci are organized into variable (V), diversity (D) and joining (J) gene segments that rearrange to generate antigen receptor repertoires. Here, we identified an enhancer (E34) in the murine immunoglobulin kappa (Igk) locus that instructed rearrangement of Vκ genes located in a sub-topologically associating domain, including a Vκ gene encoding for antibodies targeting bacterial phosphorylcholine. We show that E34 instructs the nuclear repositioning of the E34 sub-topologically associating domain from a recombination-repressive compartment to a recombination-permissive compartment that is marked by equivalent activating histone modifications. Finally, we found that E34-instructed Vκ-Jκ rearrangement was essential to combat Streptococcus pneumoniae but not methicillin-resistant Staphylococcus aureus or influenza infections. We propose that the merging of Vκ genes with Jκ elements is instructed by one-dimensional epigenetic information imposed by enhancers across Vκ and Jκ genomic regions. The data also reveal how enhancers generate distinct antibody repertoires that provide protection against lethal bacterial infection.

Subclinical atherosclerosis profiles in rheumatoid arthritis and primary Sjögren's syndrome: the impact of BAFF genetic variations

OBJECTIVES

RA and primary SS carry increased atherosclerotic risk, while B-cell activating factor holds a vital role in disease pathogenesis and atherosclerosis. We aimed to compare subclinical atherosclerosis profiles between the two clinical entities and define whether BAFF genetic variants alter atherosclerotic risk.

METHODS

DNA from 166 RA, 148 primary SS patients and 200 healthy controls of similar age and sex distribution was subjected to PCR-based assay for the detection of five single nucleotide polymorphisms of the BAFF gene (rs1224141, rs12583006, rs9514828, rs1041569 and rs9514827). Genotype and haplotype frequencies were determined by SNPStats software and statistical analysis was performed by SPSS and Graphpad Software. Subclinical atherosclerosis was defined by the presence of carotid/femoral plaque formation and arterial wall thickening.

RESULTS

Atherosclerotic plaque formation was more frequently detected in the RA vs primary SS group (80.7% vs 62.2%, P-value <0.001), along with higher rates of family CVD history, current steroid dose and serum inflammatory markers. The TT genotype of the rs1224141 variant was more prevalent in RA but not primary SS patients with plaque and arterial wall thickening vs their counterparts without. Regarding the rs1014569 variant, among RA patients the TT genotype increased the risk for plaque formation while in primary SS patients the AT genotype conferred increased risk. Haplotype GTTTT was protective in the RA cohort, while TATTT and TTCTT haplotypes increased susceptibility for arterial wall thickening in the primary SS cohort.

CONCLUSIONS

Increased inflammatory burden, higher steroid doses and distinct BAFF gene variations imply chronic inflammation and B-cell hyperactivity as key contributors for the augmented atherosclerotic risk among autoimmune patients.

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.

Total fecal IgA levels increase and natural IgM antibodies decrease after gastric bypass surgery

Obesity is associated with low-grade inflammation and increased systemic oxidative stress. Roux-en-Y gastric bypass (RYGB) surgery is known to ameliorate the obesity-induced metabolic dysfunctions. We aimed to study the levels of natural antibodies in feces, before and 6 months after RYGB surgery in obese individuals with and without type 2 diabetes (T2D). Sixteen individuals with T2D and 14 non-diabetic (ND) individuals were operated. Total IgA, IgG and IgM antibody levels and specific antibodies to oxidized low-density lipoprotein (oxLDL), malondialdehyde-acetaldehyde adducts (MAA adducts), Porphyromonas gingivalis gingipain A hemagglutinin domain (Rgp44) and phosphocholine (PCho) were measured using chemiluminescence immunoassay. Total fecal IgA was elevated, while total IgM and IgG were not affected by the surgery. Fecal natural IgM specific to oxLDL decreased significantly in both T2D and ND individuals, while fecal IgM to Rgp44 and PCho decreased significantly in T2D individuals. A decrease in IgG to MAA-LDL, Rgp44 and PCho was detected. RYGB surgery increases the levels of total fecal IgA and decreases fecal natural IgG and IgM antibodies specific to oxLDL. Natural antibodies and IgA are important in maintaining the normal gut homeostasis and first-line defense against microbes, and their production is markedly altered with RYGB surgery.

The OSE complotype and its clinical potential

Cellular death, aging, and tissue damage trigger inflammation that leads to enzymatic and non-enzymatic lipid peroxidation of polyunsaturated fatty acids present on cellular membranes and lipoproteins. This results in the generation of highly reactive degradation products, such as malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE), that covalently modify free amino groups of proteins and lipids in their vicinity. These newly generated neoepitopes represent a unique set of damage-associated molecular patterns (DAMPs) associated with oxidative stress termed oxidation-specific epitopes (OSEs). OSEs are enriched on oxidized lipoproteins, microvesicles, and dying cells, and can trigger sterile inflammation. Therefore, prompt recognition and removal of OSEs is required to maintain the homeostatic balance. This is partially achieved by various humoral components of the innate immune system, such as natural IgM antibodies, pentraxins and complement components that not only bind OSEs but in some cases modulate their pro-inflammatory potential. Natural IgM antibodies are potent complement activators, and 30% of them recognize OSEs such as oxidized phosphocholine (OxPC-), 4-HNE-, and MDA-epitopes. Furthermore, OxPC-epitopes can bind the complement-activating pentraxin C-reactive protein, while MDA-epitopes are bound by C1q, C3a, complement factor H (CFH), and complement factor H-related proteins 1, 3, 5 (FHR-1, FHR-3, FHR-5). In addition, CFH and FHR-3 are recruited to 2-(ω-carboxyethyl)pyrrole (CEP), and full-length CFH also possesses the ability to attenuate 4-HNE-induced oxidative stress. Consequently, alterations in the innate humoral defense against OSEs predispose to the development of diseases associated with oxidative stress, as shown for the prototypical OSE, MDA-epitopes. In this mini-review, we focus on the mechanisms of the accumulation of OSEs, the pathophysiological consequences, and the interactions between different OSEs and complement components. Additionally, we will discuss the clinical potential of genetic variants in OSE-recognizing complement proteins – the OSE complotype - in the risk estimation of diseases associated with oxidative stress.

Cardiovascular risk factors: The effects of ageing and smoking on the immune system, an observational clinical study

Currently immunomodulatory compounds are under investigation for use in patients with cardiovascular disease, caused by atherosclerosis. These trials, using recurrent cardiovascular events as endpoint, require enrollment of large patient groups. We investigated the effect of key risk factors for atherosclerosis development, ageing and smoking, on the immune system, with the objective to identify biomarkers differentiating between human populations, and potentially serving as endpoints for future phase 1B trials with immunomodulatory compounds. Blood was collected from young healthy volunteers (aged 18-25 years, n=30), young smokers (18-25 years, n=20), elderly healthy volunteers (>60 years, n=20), heavy smokers (>45 years, 15 packyears, n=11) and patients with stable coronary artery disease (CAD) (>60 years, n=27). Circulating immune cell subsets were characterized by flow cytometry, and collected plasma was evaluated by proteomics (Olink). Clear ageing effects were observed, mostly illustrated by a lower level in CD8+ and naïve CD4+ and CD8+ T cells, with an increase in CD4+ and CD8+ effector memory T cells in elderly healthy volunteers compared to young healthy volunteers. Heavy smokers showed a more inflammatory cellular phenotype, especially a shift in Th1/Th2 ratio: higher Th1 and lower Th2 percentages compared to young healthy volunteers. A significant decrease in circulating atheroprotective oxLDL-specific IgM was found in patients with CAD compared to young healthy volunteers. Elevated pro-inflammatory and chemotactic proteins TREM1 and CCL11 were observed in elderly volunteers compared to young volunteers. In addition, heavy smokers had an increase in pro-inflammatory cytokine IL-6 and lysosomal protein LAMP3. These data show that ageing and smoking are associated with an inflammatory immunophenotype, and that heavy smokers or aged individuals may serve as potential populations for future clinical trials investigating immunomodulatory drugs targeted for cardiovascular disease.

B-1b Cells Have Unique Functional Traits Compared to B-1a Cells at Homeostasis and in Aged Hyperlipidemic Mice With Atherosclerosis

Immunoglobulin M (IgM) to oxidation specific epitopes (OSE) are inversely associated with atherosclerosis in mice and humans. The B-1b subtype of B-1 cells secrete IgM to OSE, and unlike B-1a cells, are capable of long-lasting IgM memory. What attributes make B-1b cells different than B-1a cells is unknown. Our objectives were to determine how B-1b cells produce more IgM compared to B-1a cells at homeostatic condition and to see the differences in the B-1a and B-1b cell distribution and IgM CDR-H3 sequences in mice with advanced atherosclerosis. Here, in-vivo studies demonstrated greater migration to spleen, splenic production of IgM and plasma IgM levels in ApoE^-/-Rag1^-/- mice intraperitoneally injected with equal numbers of B-1b compared to B-1a cells. Bulk RNA seq analysis and flow cytometry of B-1a and B-1b cells identified CCR6 as a chemokine receptor more highly expressed on B-1b cells compared to B-1a. Knockout of CCR6 resulted in reduced B-1b cell migration to the spleen. Moreover, B-1b cell numbers were significantly higher in spleen of aged atherosclerotic ApoE^-/- mice compared to young ApoE^-/- mice. Single cell sequencing results of IgHM in B-1a and B-1b cells from peritoneal cavity and spleen of atherosclerotic aged ApoE^-/- mice revealed significantly more N additions at the V-D and D-J junctions, greater diversity in V region usage and CDR-H3 sequences in B-1b compared to B-1a cells. In summary, B-1b cells demonstrated enhanced CCR6-mediated splenic migration, IgM production, and IgM repertoire diversification compared to B-1a cells. These findings suggest that potential strategies to selectively augment B-1b cell numbers and splenic trafficking could lead to increased and more diverse IgM targeting OSE to limit atherosclerosis.

Targeting oxidized phospholipids by AAV-based gene therapy in mice with established hepatic steatosis prevents progression to fibrosis

Oxidized phosphatidylcholines (OxPCs) are implicated in chronic tissue damage. Hyperlipidemic LDL-R--deficient mice transgenic for an OxPC-recognizing IgM fragment (scFv-E06) are protected against nonalcoholic fatty liver disease (NAFLD). To examine the effect of OxPC elimination at different stages of NAFLD progression, we used cre-dependent, adeno-associated virus serotype 8-mediated expression of the single-chain variable fragment of E06 (AAV8-scFv-E06) in hepatocytes of albumin-cre mice. AAV8-induced expression of scFv-E06 at the start of FPC diet protected mice from developing hepatic steatosis. Independently, expression of scFv-E06 in mice with established steatosis prevented the progression to hepatic fibrosis. Mass spectrometry-based oxophospho-lipidomics identified individual OxPC species that were reduced by scFv-E06 expression. In vitro, identified OxPC species dysregulated mitochondrial metabolism and gene expression in hepatocytes and hepatic stellate cells. We demonstrate that individual OxPC species independently affect disease initiation and progression from hepatic steatosis to steatohepatitis, and that AAV-mediated expression of scFv-E06 is an effective therapeutic intervention.

Effect of Pneumococcal Vaccine on Mortality and Cardiovascular Outcomes: A Systematic Review and Meta-Analysis

Various studies have suggested the possible cardiovascular (CV) protective effects of the pneumococcal vaccine (PV). Therefore, we conducted a meta-analysis to assess the association between recipients of PV with mortality and CV outcomes among patients with and without established cardiovascular disease. We performed a systematic literature search in PubMed, Embase, and Scopus for studies evaluating the effect of PV on mortality and CV outcomes. A total of 15 studies with 347,444 patients were included in the meta-analysis: 111,784 patients received PV (32%) and 235,660 patients were in the unvaccinated group (68%). Recipients of PV were associated with decreased all-cause mortality (HR, 0.76 (95% CI: 0.66 to 0.87), p < 0.001). PV was associated with a decrease in the incidence of myocardial infarction (MI) (HR, 0.73 (95% CI: 0.56−0.96), p = 0.02), without significant reduction in CV mortality (HR, 0.87 (95% CI: 0.72−1.07), p = 0.18) and stroke (HR, 1.01 (95% CI: 0.93−1.10), p = 0.82). Our study found PV was associated with decreased risk of all-cause mortality and MI. Future RCTs will be necessary to confirm benefits associated with receipt of PV.

Receptor editing constrains development of phosphatidyl choline-specific B cells in VH12-transgenic mice

B1 B cells reactive to phosphatidyl choline (PtC) exhibit restricted immunoglobulin heavy chain (HC) and light chain (LC) combinations, exemplified by V_H12/Vκ4/5H. Two checkpoints are thought to focus PtC⁺ B cell maturation in V_H12-transgenic mice (VH12 mice): V-J rearrangements encoding a "permissive" LC capable of V_H12 HC pairing are selected first, followed by positive selection based on PtC binding, often requiring LC receptor editing to salvage PtC^- B cells and acquire PtC reactivity. However, evidence obtained from breeding VH12 mice to editing-defective dnRAG1 mice and analyzing LC sequences from PtC⁺ and PtC^- B cell subsets instead suggests that receptor editing functions after initial positive selection to remove PtC⁺ B cells in VH12 mice. This offers a mechanism to constrain natural, polyreactive B cells to limit their frequency. Sequencing also reveals occasional in-frame hybrid LC genes, reminiscent of type 2 gene replacement, that, testing suggests, arise via a recombination-activating gene (RAG)-independent mechanism.

The Spectrum of B Cell Functions in Atherosclerotic Cardiovascular Disease

B cells are a core element of the pathophysiology of atherosclerotic cardiovascular disease (ASCVD). Multiple experimental and epidemiological studies have revealed both protective and deleterious functions of B cells in atherosclerotic plaque formation. The spearhead property of B cells that influences the development of atherosclerosis is their unique ability to produce and secrete high amounts of antigen-specific antibodies that can act at distant sites. Exposure to an atherogenic milieu impacts B cell homeostasis, cell differentiation and antibody production. However, it is not clear whether B cell responses in atherosclerosis are instructed by atherosclerosis-specific antigens (ASA). Dissecting the full spectrum of the B cell properties in atherosclerosis will pave the way for designing innovative therapies against the devastating consequences of ASCVD.

Circulating Autoantibodies Recognizing Immunodominant Epitopes From Human Apolipoprotein B Associate With Cardiometabolic Risk Factors, but Not With Atherosclerotic Disease

Rationale

Atherosclerosis is a chronic inflammatory disease of large arteries that involves an autoimmune response with autoreactive T cells and auto-antibodies recognizing Apolipoprotein B (ApoB), the core protein of low-density lipoprotein (LDL). Here, we aimed to establish a clinical association between circulating human ApoB auto-antibodies with atherosclerosis and its clinical risk factors using a novel assay to detect auto-antibodies against a pool of highly immunogenic ApoB-peptides.

Methods and Results

To detect polyclonal IgM- and IgG-antibodies recognizing ApoB, we developed a chemiluminescent sandwich ELISA with 30 ApoB peptides selected by an in silico assay for a high binding affinity to MHC-II, which cover more than 80% of known MHC-II variants in a Caucasian population. This pre-selection of immunogenic self-peptides accounted for the high variability of human MHC-II, which is fundamental to allow T cell dependent generation of IgG antibodies. We quantified levels of ApoB-autoantibodies in a clinical cohort of 307 patients that underwent coronary angiography. Plasma anti-ApoB IgG and IgM concentrations showed no differences across healthy individuals (n = 67), patients with coronary artery disease (n = 179), and patients with an acute coronary syndrome (n = 61). However, plasma levels of anti-ApoB IgG, which are considered pro-inflammatory, were significantly increased in patients with obesity (p = 0.044) and arterial hypertension (p < 0.0001). In addition, patients diagnosed with the metabolic syndrome showed significantly elevated Anti-ApoB IgG (p = 0.002). Even when normalized for total plasma IgG, anti-ApoB IgG remained highly upregulated in hypertensive patients (p < 0.0001). We observed no association with triglycerides, total cholesterol, VLDL, or LDL plasma levels. However, total and normalized anti-ApoB IgG levels negatively correlated with HDL. In contrast, total and normalized anti-ApoB IgM, that have been suggested as anti-inflammatory, were significantly lower in diabetic patients (p = 0.012) and in patients with the metabolic syndrome (p = 0.005).

Conclusion

Using a novel ELISA method to detect auto-antibodies against ApoB in humans, we show that anti-ApoB IgG associate with cardiovascular risk factors but not with the clinical appearance of atherosclerosis, suggesting that humoral immune responses against ApoB are shaped by cardiovascular risk factors but not disease status itself. This novel tool will be helpful to develop immune-based risk stratification for clinical atherosclerosis in the future.

Antibodies Against Phosphorylcholine Among 60-Year-Olds: Clinical Role and Simulated Interactions

Aims

Antibodies against phosphorylcholine (anti-PC) are implicated as protection markers in atherosclerosis, cardiovascular disease (CVD), and other chronic inflammatory conditions. Mostly, these studies have been focused on IgM. In this study, we determined IgG, IgG1, and IgG2 anti-PC among 60-year-olds.

Methods

Based on a 7-year follow-up of 60-year-olds (2,039 men and 2,193 women) from Stockholm County, we performed a nested case-control study of 209 incident CVD cases with 620 age- and sex-matched controls. Anti-PC was determined using ELISA. We predicted the binding affinity of PC with our fully human, in-house-produced IgG1 anti-PC clones (i.e., A01, D05, and E01) using the molecular docking and molecular dynamics simulation approach, to retrieve information regarding binding properties to PC.

Results

After adjustment for confounders, IgG and IgG2 anti-PC showed some significant associations, but IgG1 anti-PC was much stronger as a protection marker. IgG1 anti-PC was associated with an increased risk of CVD below 33rd, 25th, and 10th percentile and of stroke below 33rd and 25th, and of myocardial infarction (MI) below 10th percentile. Among men, a strong association with stroke was determined below the 33rd percentile [HR 9.20, CI (2.22–38.12); p = 0.0022]. D05 clone has higher binding affinity followed by E01 and A01 using molecular docking and further have been confirmed during the course of 100 ns simulation. The stability of the D05 clone with PC was substantially higher.

Conclusion

IgG1 anti-PC was a stronger protection marker than IgG anti-PC and IgG2 anti-PC and also separately for men. The molecular modeling approach helps in identifying the intrinsic properties of anti-PC clones and atomistic interactions with PC.

Bioactive lipids and metabolic syndrome-a symposium report

Recent research has shed light on the cellular and molecular functions of bioactive lipids that go far beyond what was known about their role as dietary lipids. Bioactive lipids regulate inflammation and its resolution as signaling molecules. Genetic studies have identified key factors that can increase the risk of cardiovascular diseases and metabolic syndrome through their effects on lipogenesis. Lipid scientists have explored how these signaling pathways affect lipid metabolism in the liver, adipose tissue, and macrophages by utilizing a variety of techniques in both humans and animal models, including novel lipidomics approaches and molecular dynamics models. Dissecting out these lipid pathways can help identify mechanisms that can be targeted to prevent or treat cardiometabolic conditions. Continued investigation of the multitude of functions mediated by bioactive lipids may reveal additional components of these pathways that can provide a greater understanding of metabolic homeostasis.

Postnatal regulation of B-1a cell development and survival by the CIC-PER2-BHLHE41 axis

B-1 cell development mainly occurs via fetal and neonatal hematopoiesis and is suppressed in adult bone marrow hematopoiesis. However, little is known about the factors inhibiting B-1 cell development at the adult stage. We report that capicua (CIC) suppresses postnatal B-1a cell development and survival. CIC levels are high in B-1a cells and gradually increase in transitional B-1a (TrB-1a) cells with age. B-cell-specific Cic-null mice exhibit expansion of the B-1a cell population and a gradual increase in TrB-1a cell frequency with age but attenuated B-2 cell development. CIC deficiency enhances B cell receptor (BCR) signaling in transitional B cells and B-1a cell viability. Mechanistically, CIC-deficiency-mediated Per2 derepression upregulates Bhlhe41 levels by inhibiting CRY-mediated transcriptional repression for Bhlhe41, consequently promoting B-1a cell formation in Cic-null mice. Taken together, CIC is a key transcription factor that limits the B-1a cell population at the adult stage and balances B-1 versus B-2 cell formation.

A highly conserved host lipase deacylates oxidized phospholipids and ameliorates acute lung injury in mice

Oxidized phospholipids have diverse biological activities, many of which can be pathological, yet how they are inactivated in vivo is not fully understood. Here, we present evidence that a highly conserved host lipase, acyloxyacyl hydrolase (AOAH), can play a significant role in reducing the pro-inflammatory activities of two prominent products of phospholipid oxidation, 1-palmitoyl-2-glutaryl-sn-glycero-3-phosphocholine and 1-palmitoyl-2-(5-oxovaleroyl)-sn-glycero-3-phosphocholine. AOAH removed the sn-2 and sn-1 acyl chains from both lipids and reduced their ability to induce macrophage inflammasome activation and cell death in vitro and acute lung injury in mice. In addition to transforming Gram-negative bacterial lipopolysaccharide from stimulus to inhibitor, its most studied activity, AOAH can inactivate these important danger-associated molecular pattern molecules and reduce tissue inflammation and injury.

An atherosclerotic plaque-targeted single-chain antibody for MR/NIR-II imaging of atherosclerosis and anti-atherosclerosis therapy

Background

Oxidation-specific epitopes (OSEs) are rich in atherosclerotic plaques. Innate and adaptive immune responses to OSEs play an important role in atherosclerosis. The purpose of this study was to develop novel human single-chain variable fragment (scFv) antibody specific to OSEs to image and inhibit atherosclerosis.

Results

Here, we screened a novel scFv antibody, named as ASA6, from phage-displayed human scFv library. ASA6 can bind to oxidized LDL (Ox-LDL) and atherosclerotic plaques. Meanwhile, ASA6 can also inhibit the uptake of Ox-LDL into macrophage to reduce macrophage apoptosis. The atherosclerotic lesion area of ApoE^−/− mice administrated with ASA6 antibody was significantly reduced. Transcriptome analysis reveals the anti-atherosclerosis effect of ASA6 is related to the regulation of fatty acid metabolism and inhibition of M1 macrophage polarization. Moreover, we conjugated ASA6 antibody to NaNdF₄@NaGdF₄ nanoparticles for noninvasive imaging of atherosclerotic plaques by magnetic resonance (MR) and near-infrared window II (NIR-II) imaging.

Conclusions

Together, these data demonstrate the potential of ASA6 antibody in targeted therapy and noninvasive imaging for atherosclerosis.

Graphic abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-01047-4.

Complement Inhibition Targeted to Injury Specific Neoepitopes Attenuates Atherogenesis in Mice

Rationale: Previous studies have indicated an important role for complement in atherosclerosis, a lipid-driven chronic inflammatory disease associated to oxidative stress in the vessel wall. However, it remains unclear how complement is activated in the process of atherogenesis. An accepted general model for complement activation in the context of ischemia reperfusion injury is that ischemia induces the exposure of neoepitopes that are recognized by natural self-reactive IgM antibodies, and that in turn activate complement. Objective: We investigated whether a similar phenomenon may be involved in the pathogenesis of atherosclerosis, and whether interfering with this activation event, together with inhibition of subsequent amplification of the cascade at the C3 activation step, can provide protection against atherogenesis. Methods and Results: We utilized C2scFv-Crry, a novel construct consisting of a single chain antibody (scFv) linked to Crry, a complement inhibitor that functions at C3 activation. The scFv moiety was derived from C2 IgM mAb that specifically recognizes phospholipid neoepitopes known to be expressed after ischemia. C2scFv-Crry targeted to the atherosclerotic plaque of Apoe -/- mice, demonstrating expression of the C2 neoepitope. C2scFv-Crry administered twice per week significantly attenuated atherosclerotic plaque in the aorta and aortic root of Apoe -/- mice fed with a high-fat diet (HFD) for either 2 or 4 months, and treatment reduced C3 deposition and membrane attack complex formation as compared to vehicle treated mice. C2scFv-Crry also inhibited the uptake of oxidized low-density-lipoprotein (oxLDL) by peritoneal macrophages, which has been shown to play a role in pathogenesis, and C2scFv-Crry-treated mice had decreased lipid content in the lesion with reduced oxLDL levels in serum compared to vehicle-treated mice. Furthermore, C2scFv-Crry reduced the deposition of endogenous total IgM in the plaque, although it did not alter serum IgM levels, further indicating a role for natural IgM in initiating complement activation. Conclusion: Neoepitope targeted complement inhibitors represent a novel therapeutic approach for atherosclerosis.

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.

The Fetal-to-Adult Hematopoietic Stem Cell Transition and its Role in Childhood Hematopoietic Malignancies

As with most organ systems that undergo continuous generation and maturation during the transition from fetal to adult life, the hematopoietic and immune systems also experience dynamic changes. Such changes lead to many unique features in blood cell function and immune responses in early childhood. The blood cells and immune cells in neonates are a mixture of fetal and adult origin due to the co-existence of both fetal and adult types of hematopoietic stem cells (HSCs) and progenitor cells (HPCs). Fetal blood and immune cells gradually diminish during maturation of the infant and are almost completely replaced by adult types of cells by 3 to 4 weeks after birth in mice. Such features in early childhood are associated with unique features of hematopoietic and immune diseases, such as leukemia, at these developmental stages. Therefore, understanding the cellular and molecular mechanisms by which hematopoietic and immune changes occur throughout ontogeny will provide useful information for the study and treatment of pediatric blood and immune diseases. In this review, we summarize the most recent studies on hematopoietic initiation during early embryonic development, the expansion of both fetal and adult types of HSCs and HPCs in the fetal liver and fetal bone marrow stages, and the shift from fetal to adult hematopoiesis/immunity during neonatal/infant development. We also discuss the contributions of fetal types of HSCs/HPCs to childhood leukemias.

Higher levels of anti-phosphorylcholine autoantibodies in early rheumatoid arthritis indicate lower risk of incident cardiovascular events

Background

The increased risk of cardiovascular events (CVE) in rheumatoid arthritis (RA) is not fully explained by traditional risk factors. Immuno-inflammatory mechanisms and autoantibodies could be involved in the pathogenesis of atherosclerotic disease. It has been suggested that anti-phosphorylcholine antibodies (anti-PC) of the IgM subclass may have atheroprotective effects. Here, we aimed to investigate the association between levels of IgM anti-PC antibodies with CVE in patients with early RA.

Methods

The study population was derived from the BARFOT early RA cohort, recruited in 1994–1999. The outcome of incident CVE (AMI, angina pectoris, coronary intervention, ischemic stroke, TIA) was tracked through the Swedish Hospital Discharge and the National Cause of Death Registries. Sera collected at inclusion and the 2-year visit were analyzed with ELISA to determine levels of anti-PC IgM. The Kaplan-Meier estimates and Cox proportional hazards regression models were used to compare CV outcome in the groups categorized by baseline median level of IgM anti-PC.

Results

In all, 653 patients with early RA, 68% women, mean (SD) age 54.8 (14.7) years, DAS28 5.2 (1.3), 68% seropositive, and without prevalent CVD, were included. During the follow-up of mean 11.7 years, 141 incident CVE were recorded.

Baseline IgM anti-PC above median was associated with a reduction in risk of incident CVE in patients aged below 55 years at inclusion, HR 0.360 (95% CI, 0.142–0.916); in males, HR 0.558 (0.325–0.958); in patients with BMI above 30 kg/m², HR 0.235 (0.065–0.842); and in those who did not achieve DAS28 remission at 1 year, HR 0.592 (0.379–0.924). The pattern of associations was confirmed in the models with AUC IgM anti-PC over 2 years.

Conclusion

Protective effects of higher levels of innate IgM anti-PC autoantibodies on CVE were detected in younger patients with RA and those at high risk of CVE: males, presence of obesity, and non-remission at 1 year.

Anti-inflammatory and Immunomodulatory Therapies in Atherosclerosis

Hypercholesterolemia is a major risk factor in atherosclerosis development and lipid-lowering drugs (i.e., statins) remain the treatment of choice. Despite effective reduction of LDL cholesterol in patients, a residual cardiovascular risk persists in some individuals, highlighting the need for further therapeutic intervention. Recently, the CANTOS trial paved the way toward the development of specific therapies targeting inflammation, a key feature in atherosclerosis progression. The pre-existence of multiple drugs modulating both innate and adaptive immune responses has significantly accelerated the number of translational studies applying these drugs to atherosclerosis. Additional preclinical research has led to the discovery of new therapeutic targets, offering promising perspectives for the treatment and prevention of atherosclerosis. Currently, both drugs with selective targeting and broad unspecific anti-inflammatory effects have been tested. In this chapter, we aim to give an overview of current advances in immunomodulatory treatment approaches for atherosclerotic cardiovascular diseases.

Uptake of oxidized lipids by the scavenger receptor CD36 promotes lipid peroxidation and dysfunction in CD8+ T cells in tumors

A common metabolic alteration in the tumor microenvironment (TME) is lipid accumulation, a feature associated with immune dysfunction. Here, we examined how CD8+ tumor infiltrating lymphocytes (TILs) respond to lipids within the TME. We found elevated concentrations of several classes of lipids in the TME and accumulation of these in CD8+ TILs. Lipid accumulation was associated with increased expression of CD36, a scavenger receptor for oxidized lipids, on CD8+ TILs, which also correlated with progressive T cell dysfunction. Cd36-/- T cells retained effector functions in the TME, as compared to WT counterparts. Mechanistically, CD36 promoted uptake of oxidized low-density lipoproteins (OxLDL) into T cells, and this induced lipid peroxidation and downstream activation of p38 kinase. Inhibition of p38 restored effector T cell functions in vitro, and resolution of lipid peroxidation by overexpression of glutathione peroxidase 4 restored functionalities in CD8+ TILs in vivo. Thus, an oxidized lipid-CD36 axis promotes intratumoral CD8+ T cell dysfunction and serves as a therapeutic avenue for immunotherapies.

B Cells in Atherosclerosis: Mechanisms and Potential Clinical Applications

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B cells regulate atherosclerotic plaque formation through production of antibodies and cytokines, and effects are subset specific (B1 and B2).

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Putative human atheroprotective B1 cells function similarly to murine B1 in their spontaneous IgM antibody production. However, marker strategies in identifying human and murine B1 are different.

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IgM antibody to oxidation specific epitopes produced by B1 cells associate with human coronary artery disease.

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Neoantigen immunization may be a promising strategy for atherosclerosis vaccine development, but further study to determine relevant antigens still need to be done.

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B-cell–targeted therapies, used in treating autoimmune diseases as well as lymphoid cancers, might have potential applications in treating cardiovascular diseases. Short- and long-term cardiovascular effects of these agents need to be assessed.

Because atherosclerotic cardiovascular disease is a leading cause of death worldwide, understanding inflammatory processes underpinning its pathology is critical. B cells have been implicated as a key immune cell type in regulating atherosclerosis. B-cell effects, mediated by antibodies and cytokines, are subset specific. In this review, we focus on elaborating mechanisms underlying subtype-specific roles of B cells in atherosclerosis and discuss available human data implicating B cells in atherosclerosis. We further discuss potential B cell–linked therapeutic approaches, including immunization and B cell–targeted biologics. Given recent evidence strongly supporting a role for B cells in human atherosclerosis and the expansion of immunomodulatory agents that affect B-cell biology in clinical use and clinical trials for other disorders, it is important that the cardiovascular field be cognizant of potential beneficial or untoward effects of modulating B-cell activity on atherosclerosis.