apoSAA and AA: Precursor and Product Revisited

Since the discovery of the immunologie cross-reactivity and amino acid sequence identity between AA amyloid and the amino terminal portion of apoSAA, a precursor-product relationship between these two proteins has been envisaged (1). In light of the chronically elevated level of serum apoSAA requisite for the development of AA amyloidosis, the role of precursor to deposited AA has been ascribed to the circulating apoSAA pool. The selective removal of the putative amyloid-forming isotype apoSAA2 from the circulation of amyloidotic mice provides indirect support for this hypothesis (2), Other than a single report of the apparent conversion of human apoSAA to human AA in mice (3), direct evidence of a precursor product relationship has been lacking.