Slower clearance of human SAA1.5 in mice: implications for allele specific variation of SAA concentration in human.

Serum amyloid A (SAA), the serum precursor of the fibrillar component (AA proteins) in reactive amyloid deposits, is a multigene product. SAA1, the prominent acute phase isotype in serum and also the dominant fibril precursor, has several allelic variants. In Japan, each of the three major alleles (1.1, 1.3 and 1.5) appears with approximately equal frequency. Recent research suggested that allele 1.5 has a positive influence on the serum SAA concentration. To clarify this, in the present study, recombinant human SAA1.1, SAA1.3 and SAA1.5 were produced in an E. coli expression system and those species of reconstituted high density lipoprotein were injected into mice to examine plasma clearance. SAA1.5 disappeared from plasma more slowly than the other two isotypes. This may account for the positive influence of allele 1.5 on the serum SAA concentration.