Serum Amyloid A protein-1 belongs to the SAA family of apolipoproteins that circulates in association with high-density lipoproteins (HDL). It is a multifunctional protein produced by hepatocytes in response to pro-inflammatory cytokines. SAA1 is a ligand for CD36/SR-B3, SR-B1, FPRL1, TLR2, and RAGE on monocytes/macrophages, inducing chemotaxis and generation of cytokines and tissue factor. It also can bind the surface of invading gram-negative bacteria, acting as an opsonin to aid clearance by macrophages. Additionally, SAA1 binds platelets, probably by engaging fibrinogen on the platelet surface.