Serum amyloid P component (SAP, also known as APCS), belongs to the family of pentraxins, a superfamily of plasma proteins characterized by their pentameric assembly and calcium-dependent ligand binding. SAP is a constitutive serum protein synthesized by hepatocytes. It is structurally related to C-reactive protein, a major acute-phase reactant in humans. SAP is a calcium-dependent ligand binding protein, which can interact with DNA and histones and may scavenge nuclear material released from damaged circulating cells. SAP can also bind to fibrils in all types of amyloid deposits, and contributes to the pathogenesis of amyloidosis.