Figure 4: Overview of the major activities of the pentraxins.  Both CRP and SAP are predominantly serum proteins, produced in the liver. In man SAP is constitutive and CRP is a major acute phase reactant. Both contribute to host defense as direct opsonins and through complement activation. Both bind to ligands exposed during cell death and tissue damage leading to opsonization and removal. In addition to these activities many studies support a role for pentraxins in regulating the inflammatory response to immune complexes and TLR agonists. This regulation is initiated by pentraxin interactions with FcγR and mediated by polarized macrophages.