Neutrophils are polymorphonuclear leucocytes that are distinguished and named by the special shape of their multi-lobed nucleus. They function as an early defence against pathogens and fulfil important functions in inflammatory and innate immune responses to protect the host. Neutrophils developed several strategies to accomplish these tasks, including degranulation, phagocytosis, apoptosis, release of reactive oxygen species (ROS), and the formation of neutrophil extracellular traps (NETs). These mechanisms are triggered by pathogens (eg bacterial lipopolysaccharides), but can also be activated by other leucocytes, locally produced cytokines, or other inflammatory stimuli.

Neutrophils produce cytoplasmic granules containing enzymes that can be released upon stimulation, including myeloperoxidase (MPO), matrix metalloproteinase 8 (MMP8), cathelicidin antimicrobial peptide (CAMP, also known as LL-37), azurocidin 1 (AZU1), cathepsin G (CTSG), and elastase 2 (ELA2). These enzymes serve to directly combat a pathogen or to enhance an inflammatory response. Despite their important function in innate immunity, the outcome of neutrophil activation is not always beneficial. Many studies are showing an involvement of neutrophils in the progression of cardiovascular diseases (CVD) including atherosclerosis, thrombosis, and ACS.