Mouse Serum Amyloid A protein 1 is a multifunctional apolipoprotein produced by hepatocytes in response to proinflammatory cytokines. It is secreted as a 12 kDa, 103 amino acid, nonglycosylated protein and circulates as part of the HDL complex. SAA1 can bind the surface of invading gram?negative bacteria, acting as an opsonin to aid clearance by macrophages. SAA1 also binds platelets, probably by engaging fibrinogen on the platelet surface.