Conventional B2 B Cell Depletion Ameliorates whereas Its Adoptive Transfer Aggravates Atherosclerosis

Abstract

Atherosclerosis is a chronic inflammatory arterial disease characterized by focal accumulation of lipid and inflammatory cells. It is the number one cause of deaths in the Western world because of its complications of heart attacks and strokes. Statins are effective in only approximately one third of patients, underscoring the urgent need for additional therapies. B cells that accumulate in atherosclerotic lesions and the aortic adventitia of humans and mice are considered to protect against atherosclerosis development. Unexpectedly, we found that selective B cell depletion in apolipoprotein E-deficient (ApoE−/−) mice using a well-characterized mAb to mouse CD20 reduced atherosclerosis development and progression without affecting the hyperlipidemia imposed by a high-fat diet. Adoptive transfer of 5 × 106 or 5 × 107 conventional B2 B cells but not 5 × 106 B1 B cells to a lymphocyte-deficient ApoE−/− Rag-2−/− common cytokine receptor γ-chain–deficient mouse that was fed a high-fat diet augmented atherosclerosis by 72%. Transfer of 5 × 106 B2 B cells to an ApoE−/− mouse deficient only in B cells aggravated atherosclerosis by >300%. Our findings provide compelling evidence for the hitherto unrecognized proatherogenic role of conventional B2 cells. The data indicate that B2 cells can potently promote atherosclerosis development entirely on their own in the total absence of all other lymphocyte populations. Additionally, these B2 cells can also significantly augment atherosclerosis development in the presence of T cells and all other lymphocyte populations. Our findings raise the prospect of B cell depletion as a therapeutic approach to inhibit atherosclerosis development and progression in humans.

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

“…To date, it is generally accepted that (auto)antibody‐producing B1 B cells are atheroprotective26, 27 and this protective effect depends on IgM secretion,28 whereas conventional B2 B cells are generally considered proatherogenic 29. This proatherogenic phenotype in mice has mainly been attributed to the production of pathogenic IgG antibodies against oxidized low‐density lipoprotein (oxLDL) and the immune effector function of these B cells 27, 28, 30, 31, 32, 33. In human atherosclerosis, however, there is conflicting evidence about the role of autoantibodies directed against oxLDL.…”

Characterization of Resident B Cells of Vascular Walls in Human Atherosclerotic Patients

“…Accordingly, immune-mediated inflammation in atherosclerosis has been initially envisioned as solely orchestrated by T cells. However, B cell depletion in animal models has recently challenged this conclusion (5,6).…”

Anti‐TIM‐1 Monoclonal Antibody (RMT1‐10) Attenuates Atherosclerosis By Expanding IgM‐producing B1a Cells

“…B lymphocytes and non‐B‐lymphocyte populations in spleen and peritoneal cavity were analyzed with fluorochrome conjugated antibodies (BD Pharmingen, San Diego, CA) on FACS‐Canto II (BD Biosciences) as described 1, 20, 21. Phycoerythrin (PE)‐conjugated anti‐CD19, Allophycocyanin (APC)‐conjugated anti‐CD5, APC‐Cy7–conjugated anti‐CD11b, Pacific Blue‐conjugated anti‐CD4, PerCP‐conjugated anti‐CD8α, Fluorescein isothiocyanate (FITC)‐ conjugated anti‐TCR‐b and PE‐Cy7–conjugated anti‐NK1.1 antibodies were used in lymphocyte analysis.…”

“…In accordance with the American Heart Association statement22, 24 frozen sections (6 μm) were cut from the aortic sinus, the region where the valve or valve cusps first become visible to where the left and right coronary arteries branch off 25. To assess atherosclerosis, Oil Red O‐stained atherosclerotic lesions at aortic sinus (6 sequential sections at 80‐μm intervals) were used to measure both total intimal lesion areas and Oil Red O‐stained lipid deposition areas as described before 20. For necrotic core assessment in atherosclerotic lesions, aortic root atherosclerotic lesions were stained with hematoxylin and eosin (H&E) to identify acellular areas as necrotic cores and measured as described previously 1, 26, 27.…”

“…Apoptotic cells identified by terminal dUTP nick end‐labeling (TUNEL) under light microscopy were expressed per lesion areas as described before 20, 28…”