Innate and adaptive immune responses have an essential role in the development and progression of many cardiovascular diseases. The concept of atherosclerosis--the primary cause of coronary artery disease, stroke, and peripheral vascular disease--as a chronic inflammatory disease is widely accepted. Inflammation is also involved in the pathophysiology of atrial fibrillation, the most common cardiac arrhythmia. Defects in the resolution of inflammation promote the progression to vulnerable plaque in atherosclerosis, and altered immune responses can lead to cardiac remodelling after myocardial infarction. To highlight the importance of the immune system in the pathophysiology of cardiovascular diseases, Nature Reviews Cardiology brings together a Collection (1) of Reviews and news articles that summarize our current knowledge and recent advances in this field.

Three Reviews in this Collection focus on specific immune cells and their role in cardiovascular diseases. Chinetti-Gbaguidi and colleagues review the diverse range of macrophage phenotypes in atherosclerotic lesions and their roles in plaque progression and stability. Shi et al. focus on mast cells, which are involved in the pathogenesis of many cardiometabolic diseases, including atherosclerosis, aortic aneurysm, valvular disease, obesity, and diabetes mellitus. Accumulating evidence indicates that regulatory T cells ([T. sub. reg])--which regulate T-cell responses and induce anti-inflammatory macrophages--might have an important role in protecting against cardiovascular disease. The latest discoveries on the role of [T. sub. reg] cells in several cardiovascular disorders, such as atherosclerosis, hypertension, and myocardial infarction, are discussed by Meng and colleagues in their Review.