Characterization of amyloid related protein SAA complexed with serum lipoproteins (apoSAA).

The amyloid related protein SAA was isolated from the serum lipoproteins of three patients with connective tissue disease, one of them having amyloidosis, and from a pool of normal control sera. The bulk of SAA (apoSAA) was complexed to high density lipoprotein (HDL), but significant amounts of apoSAA were also detected in the other lipoprotein fractions. Electrofocusing revealed five-six subspecies of SAA which were distributed in similar proportions in HDL and LDL. Three of these SAA subspecies made up almost all of the apoSAA present in HDL and LDL in the sera from the patients as well as in the control. A small portion of SAA not complexed to lipoproteins was isolated corresponding to a molecular weight higher than 200,000. No particular 'amyloid prone' SAA was found in serum from the patient with amyloidosis.