Rationale: Deficiency of secreted IgM (sIgM-/-) accelerates atherosclerosis in Ldlr-/-mice. Several atheroprotective effects of increased levels of IgM antibodies have been suggested, including... Show moreRationale: Deficiency of secreted IgM (sIgM-/-) accelerates atherosclerosis in Ldlr-/-mice. Several atheroprotective effects of increased levels of IgM antibodies have been suggested, including preventing inflammation induced by oxidized LDL and promoting apoptotic cell clearance. However, the mechanisms by which the lack of sIgM promotes lesion formation remain unknown. Objective: To identify the mechanisms by which sIgM deficiency accelerates atherosclerosis in mice. Methods and Results: We here show that both sIgM-/- and Ldlr-/-sIgM-/- mice develop increased plasma IgE titers due to impaired generation of B cells expressing the low affinity IgE receptor CD23, which mediates the clearance of IgE antibodies. We further report that Ldlr-/-sIgM-/- mice exhibit increased numbers of activated mast cells and neutrophils in the perivascular area of atherosclerotic plaques. Treatment with an anti-IgE neutralizing antibody fully reversed vascular inflammation and accelerated atherosclerotic lesion formation in cholesterol-fed Ldlr-/-sIgM-/- mice. Conclusions: Thus, our data identify a previously unsuspected mechanism by which sIgM deficiency aggravates atherosclerosis. Keywords: Atherosclerosis, secreted IgM, IgE, B cells, arteriosclerosis, immune system, antibody, inflammation. Show less
A great majority of the morbidity and mortality worldwide can still be attributed to cardiovascular diseases, such as ischemic (coronary) heart disease, angina pectoris, and myocardial and cerebral... Show moreA great majority of the morbidity and mortality worldwide can still be attributed to cardiovascular diseases, such as ischemic (coronary) heart disease, angina pectoris, and myocardial and cerebral infarction. Atherosclerosis, narrowing of the arteries because of arterial cholesterol deposition in macrophage foam cells, is the driving force behind the cardiovascular disease pathology. Water-soluble protein/lipid complexes called lipoproteins mediate the transport of cholesterol and other lipoid substances through the blood compartment. Relatively high levels of cholesterol associated with apolipoprotein B–containing low-density lipoprotein (LDL) particles predispose human subjects to the development of atherosclerosis and, thereby, increase the risk for cardiovascular disease.1,2 Apolipoprotein B–containing lipoproteins are, therefore, generally regarded as being proatherogenic factors. Cholesterol ester–rich high-density lipoprotein (HDL) particles use apolipoprotein A1 (apoA1) as their primary protein component. In sharp contrast to LDL, HDL is considered a potent anti-atherogenic agent. This notion is based on the fact that, in the general population, a strong inverse correlation exists between plasma levels of HDL cholesterol and the risk of cardiovascular disease.1 Of note, this inverse association seems to be independent of the level of cholesterol associated with proatherogenic LDL particles. As such, increasing plasma levels of HDL cholesterol has long been regarded a promising alternative therapy to supplement classical statin–based LDL cholesterol–lowering strategies that are able to reduce cardiovascular disease by only ≈30%.3 However, over the last decade, the enthusiasm for HDL as an interesting therapeutic target has been challenged by the HDL hypothesis critics because genetic association studies have excluded HDL cholesterol levels as determinants for cardiovascular disease risk.2,4 Furthermore, several therapeutic HDL-targeting approaches have proven insufficient to secure benefit for cardiovascular disease patients. Show less
PURPOSE OF REVIEW:The number of deaths associated with cardiovascular disease remains high, despite great advances in treating the associated high levels of cholesterol. The main underlying... Show morePURPOSE OF REVIEW:The number of deaths associated with cardiovascular disease remains high, despite great advances in treating the associated high levels of cholesterol. The main underlying pathology of cardiovascular disease is atherosclerosis, which is recognized as a chronic autoimmune-like inflammatory disease. Hence, there is a pressing need to shed light on the immune pathways associated with atherosclerosis. B cells have long been thought to have a general protective effect in atherosclerosis. However, findings in the last decade have challenged this paradigm, showing that it is crucial to differentiate between the various B-cell subsets when assessing their role/effect on atherosclerosis.RECENT FINDINGS:It has become increasingly recognized lately that B cells can have significant effects on the immune system independent of antibody production. The understanding that B cells form a major source of cytokines and can directly influence T-cell responses via surface markers, have led to the identification of novel B-cell subsets. These subsets are important modulators of autoimmune disorders but have not yet been fully investigated in atherosclerosis.SUMMARY:Here we review the current known roles of B-cell subsets and the putative effects of recently identified B cells on atherosclerosis. Show less
