Interleukin-10 production and T cell-suppressive capacity in B cell subsets from atherosclerotic apoE -/- mice

The dichotomy of regulatory B cells in cancer versus allergic disease

Regulatory B cells (Bregs) are an immunosuppressive cell phenotype that affects the immune system by limiting the inflammatory cascade. Dysregulation of Bregs can interestingly play a dichotomous role in the pathophysiology of many diseases and is especially highlighted when examining cancer pathology compared to allergic disease. This study reviews the existing literature on Bregs and compares their role in allergic disease in contrast to cancer development. Upregulation of Bregs in cancer states has been associated with poor prognostic outcomes across various cancer types, and Breg proliferation was associated with chronic interferon signaling, activation of the BCR-BTK (B cell receptor-Bruton's tyrosine kinase) pathway, and release of C-X-C motif ligand 13. In contrast, Breg dysfunction has been identified as a key mechanism in many allergic diseases, such as allergic asthma, allergic rhinitis, atopic dermatitis, and contact dermatitis. Development of Breg-targeted immunotherapies is currently at the preclinical level, but strategies differentially focus on Breg depletion in cancer versus Breg stimulation in allergy. Our review highlights the divergent functions that Bregs play in cancer compared to allergy. We conclude that natural homeostasis hinges on a fine balance between the dichotomous role of Bregs-over or underactivation can result in a pathological state.

Vascular Inflammation in Cardiovascular Disease: Is Immune System Protective or Bystander?

Cardiovascular disease (CVD) is one of the leading causes of death worldwide. Chronic atherosclerosis induced vascular inflammation and perturbation of lipid metabolism is believed to be a major cause of CVD. Interplay of innate and adaptive Immune system has been interwined with various risk factors associated with the initiation and progression of atherosclerosis in CVD. A large body of evidence indicates a correlation between immunity and atherosclerosis. Retention of plasma lipoproteins in arterial subendothelial wall triggers the T helper type 1 (Th1) cells and monocyte-derived macrophages to form atherosclerotic plaques. In the present review, we will discuss the pathogenesis of CVD in relation to atherosclerosis with a particular focus on pro-atherogenic role of immune cells. Recent findings have also suggested anti-atherogenic roles of different B cell subsets. Therapeutic approaches to target atherosclerosis risk factors have reduced the mortality, but a need exists for the novel therapies to treat arterial vascular inflammation. These insights into the immune pathogenesis of atherosclerosis can lead to new targeted therapeutics to abate cardiovascular mortality and morbidity.

Immunosuppressive Mechanisms of Regulatory B Cells

Regulatory B cells (Bregs) is a term that encompasses all B cells that act to suppress immune responses. Bregs contribute to the maintenance of tolerance, limiting ongoing immune responses and reestablishing immune homeostasis. The important role of Bregs in restraining the pathology associated with exacerbated inflammatory responses in autoimmunity and graft rejection has been consistently demonstrated, while more recent studies have suggested a role for this population in other immune-related conditions, such as infections, allergy, cancer, and chronic metabolic diseases. Initial studies identified IL-10 as the hallmark of Breg function; nevertheless, the past decade has seen the discovery of other molecules utilized by human and murine B cells to regulate immune responses. This new arsenal includes other anti-inflammatory cytokines such IL-35 and TGF-β, as well as cell surface proteins like CD1d and PD-L1. In this review, we examine the main suppressive mechanisms employed by these novel Breg populations. We also discuss recent evidence that helps to unravel previously unknown aspects of the phenotype, development, activation, and function of IL-10-producing Bregs, incorporating an overview on those questions that remain obscure.

Functional Role of B Cells in Atherosclerosis

Atherosclerosis is a lipid-driven inflammatory disease of blood vessels, and both innate and adaptive immune responses are involved in its development. The impact of B cells on atherosclerosis has been demonstrated in numerous studies and B cells have been found in close proximity to atherosclerotic plaques in humans and mice. B cells exert both atheroprotective and pro-atherogenic functions, which have been associated with their B cell subset attribution. While B1 cells and marginal zone B cells are considered to protect against atherosclerosis, follicular B cells and innate response activator B cells have been shown to promote atherosclerosis. In this review, we shed light on the role of B cells from a different, functional perspective and focus on the three major B cell functions: antibody production, antigen presentation/T cell interaction, and the release of cytokines. All of these functions have the potential to affect atherosclerosis by multiple ways and are dependent on the cellular milieu and the activation status of the B cell. Moreover, we discuss B cell receptor signaling and the mechanism of B cell activation under atherosclerosis-prone conditions. By summarizing current knowledge of B cells in and beyond atherosclerosis, we are pointing out open questions and enabling new perspectives.

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.

Interleukin-32 increases in coronary arteries and plasma from patients with coronary artery disease

BACKGROUND

Interleukin-32 (IL-32) is a cytokine associated with higher risk of cardiovascular diseases in inflammatory environments. This study aimed to investigate the IL-32 levels in coronary artery disease (CAD) patients.

METHODS

IL-32 expression in coronary arteries from both normal donors and CAD patients were analyzed. Plasma IL-32, IFN-γ and IL-17 levels in stable angina pectoris (SAP, n = 80) patients, unstable angina pectoris (UAP, n = 96) patients, acute myocardial infarction (AMI, n = 72) patients and patients exhibiting chest pain unrelated to coronary artery disease (NCAD, n = 72) were measured. Additionally, whether plasma IL-32 levels were independent correlated with the presence of CAD was analyzed.

RESULTS

IL-32 was high expressed in atherosclerotic plaques of CAD patients when compared with normal coronary arteries, and macrophages were the major sources of IL-32. Compared with the NCAD group, IL-32, IFN-γ and IL-17 levels were increased in the CAD group and gradually increased through the SAP, UAP and AMI groups. Plasma IL-32 levels were positively correlated with the Gensini score, IFN-γ levels and IL-17 levels in CAD patients. The results of linear regression showed that IL-32 was independently associated with the occurrence of CAD.

CONCLUSION

Both the coronary artery and circulating IL-32 levels were increased in CAD patients and IL-32 may be a marker of noninvasive diagnosis of CAD.

Bidirectional effects of IL-10+ regulatory B cells in Ldlr-/- mice

BACKGROUND AND AIMS

Limiting the pro-inflammatory immune response is critical for the treatment of atherosclerosis. Regulatory B cells (Bregs) can modulate the immune response through interleukin-10 (IL-10). Current data regarding Bregs and atherosclerosis is scarce and conflicting.

METHODS

In this study, we investigated the frequency of IL-10⁺ B cells during the development of atherosclerosis in low-density lipoprotein receptor-deficient (Ldlr^-/-) mice and studied the effect of adoptive transfer of IL-10⁺ B cells on atherosclerosis.

RESULTS

We found a very strong inverse correlation between atherosclerosis severity and the frequency of IL-10⁺ B cells. This effect was cholesterol-independent and observed in spleen, draining lymph nodes and peritoneal cavity. To directly assess the effects of IL-10⁺ B cells on atherosclerosis, we expanded IL-10⁺ B cells ex vivo with anti-CD40 and selected pure and viable IL-10-secreting B cells and IL-10^- B cells and adoptively transferred them to Ldlr^-/- mice, respectively. While IL-10^- B cells were strongly atherogenic compared to control-treated mice, IL-10⁺ B cells did not affect lesion size. Adoptive transfer of IL-10⁺ B cells strongly reduced circulating leukocyte numbers and inflammatory monocytes. In addition, they decreased CD4⁺ T cell activation and increased IL-10⁺ CD4⁺ T cell numbers. Interestingly, both IL-10⁺ and IL-10^- B cells exacerbated serum cholesterol levels and resulted in fatty livers, which potentially masked the beneficial effects of IL-10⁺ B cells on atherosclerosis.

CONCLUSIONS

These findings underscore the strong immune-regulating function of IL-10⁺ B cells and provide additional incentives to explore effective strategies that expand IL-10⁺ B cells in atherosclerosis.