Introduction
SAA4 is a constitutively expressed protein which is a member of the SAA family. SAA4 is a major acute phase reactant and an apolipoprotein of the HDL complex. SAA4 is constitutively expressed only in humans and mice; it is connected almost completely with lipoproteins of the high density range. The physiological function of SAA4 is unknown, and its serum concentration has no association with those of other major apolipoproteins. SAA4 mRNA and protein occurrence in macrophage derived foam cells of coronary and carotid arteries implied a specific role of human SAA4 during inflammation including atherosclerosis.