Serum amyloid A (SAA), a protein without a function: some suggestions with reference to cholesterol metabolism.

Serum amyloid A, as an apolipoprotein, is present on high density lipoprotein only during inflammatory states. When viewed from HDL's established function as a mechanism for reverse cholesterol transportation, it is postulated that serum amyloid A represents a signal to redirect HDL to sites of tissue destruction where cholesterol is being collected by macrophages. The object is to direct the reverse cholesterol transporter to sites of cholesterol accumulation for the subsequent removal of these cholesterol stores. The hypothesis has relevance to the process of atheroma formation.