Serum amyloid A proteins (SAA) represents a family of apolipoproteins that circulates in association with high-density lipoproteins (HDL).The level of apo-SAA, normally 1-5 μg/ml in plasma, increases 500-1000 fold within 24 hours of an inflammatory stimulus and, under these conditions, is the most abundant HDL apo-lipoprotein.The human SAA gene codes for a 122 amino acid nonglycosylated polypeptide, which contains an 18 amino acid N-terminal sequence.Recombinant human apo-SAA1 is an 11.7 kDa protein containing 105 amino acid residues.