C-Reactive Protein (CRP), also known as Pentraxin 1, is a secreted pentameric protein that functions as a sensor and activator for the innate immune response. In humans, it is a major acute-phase protein; its circulating concentration is dramatically elevated at the onset of inflammation. In mice, however, serum CRP levels increase only slightly during inflammation, and the analogous acute phase role is filled by Pentraxin 2. CRP binds, opsonizes, and induces the phagocytosis of bacteria and apoptotic cells. It regulates activation of the classical complement pathway by binding several proteins in the complement cascade as well as Fc gamma RI, Fc gamma RIIA, and Fc gamma RIIB on macrophages and dendritic cells. It also promotes dendritic cell maturation and humoral immunity. In cardiovascular disease, CRP binds to oxidized LDL, exacerbates tissue damage in myocardial infarction, and inhibits the repair of injured vascular endothelium.